Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF ONE PIECE INSERT USE FOR AN ARTIFICFIAL FOOT
Abstract	An improved process for the preparation of a one piece insert consisting of the components such as the ankle block, forefoot and the hindfoot useful in the preparation of an artificial foot This invention relates to an improved process for the preparation of a one piece insert useful for an artificial foot consisting of the components such as the ankle block, forefoot and the hind foot. The one piece insert prepared by the process of the invention can be used for the preparation of an artificial foot such as the Jaipur foot. The process of the present invention is less labor intensive, cost effective and amenable to semi or automatic production techniques. The process for the preparation of an artificial foot such as the Jaipur foot still required the tying of the individual components namely the ankle block, hind foot block and the forefoot blocks with a nylon tyrecord. The components tied together were then used for the preparation of an artificial foot. The drawback in this process is that the labour involved and the skill involved in tying of the individual components of the foot. Failures resulted if the components were not tied together properly. In the present invention these drawbacks have been removed by preparing single piece insert thus eliminating the procedure of tying the components.

Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF ONE PIECE INSERT USE FOR AN ARTIFICFIAL FOOT

Abstract

An improved process for the preparation of a one piece insert consisting of the components such as the ankle block, forefoot and the hindfoot useful in the preparation of an artificial foot This invention relates to an improved process for the preparation of a one piece insert useful for an artificial foot consisting of the components such as the ankle block, forefoot and the hind foot. The one piece insert prepared by the process of the invention can be used for the preparation of an artificial foot such as the Jaipur foot. The process of the present invention is less labor intensive, cost effective and amenable to semi or automatic production techniques. The process for the preparation of an artificial foot such as the Jaipur foot still required the tying of the individual components namely the ankle block, hind foot block and the forefoot blocks with a nylon tyrecord. The components tied together were then used for the preparation of an artificial foot. The drawback in this process is that the labour involved and the skill involved in tying of the individual components of the foot. Failures resulted if the components were not tied together properly. In the present invention these drawbacks have been removed by preparing single piece insert thus eliminating the procedure of tying the components.

Full Text	This invention relates to an improved process for the preparation of a one piece insert useful for an artificial foot. The invention particularly relates to a process for the preparation of a one piece insert consisting of the components such as the ankle block,forefoot and the hindfoot. The one piece insert prepared by the process of the invention can be used for the preparation of an artificial foot such as the Jaipur foot. The process of the present invention is less labor intensive, cost effective and amenable to semi or automatic production techniques. In our copending application number 1096/del/93 (Patent no. 187914) we have described and claimed a process for the preparation of polyol useful for ankle block preparation. In application nos. 1087/del/93(Patent no. 187915) we have claimed and described process for the preparation of ankle and fore/hindfoot components respectively. These components can be used in the preparation of an artificial foot such as the Jaipur foot by the process of the present invention. Jaipur foot is an extensively used and very well accepted rehabilitation aid for the physically handicapped persons in this country. The number of amputees who have been fitted with these foot piece runs into hundreds and thousands. The utility of the foot has been well proven and there is a heavy demand from several countries including some of the advanced countries due to the mobility offered by the design, of the said foot. A number of alternative rehabilitation aids for the physically handicapped are available from the western world. The major difficulty of these rehabilitation aids, not acceptable in our country is due to the differences in the life style of the persons affected. The western style of rehabilitation aids for the physically handicapped has closed shoe wearing norm in contrast to the needs of the patients of this country where bare foot walking and use of well ventilated footwear for the warm climate is the preferred option. The Jaipur foot was first introduced in 1970 and though there have been design changes to suit the needs of the patients from time to time, the basic features continue to be followed. The conventional Jaipur foot is made from wood laminates shaped to form the ankle block portion and microcellular rubber blocks for the forefoot and hind foot. The three components are held together by a nylon reinforced tyrecord and enclosed within a cover of skin colored solid elastomer. The foot has been used in tough field conditions and is very well accepted by the handicapped persons. The conventional hindfoot component preparation has the following drawbacks : 1. The ankle block is made from wood and shaped to give the shape of the ankle and is highly labour intensive and requires special skill of the worker so that the block is useful 2. The process for the hindfoot manufacturing involves preparation of laminates of microcellular rubber and then manually carving the laminates into a form of hindfoot. The process is thus highly labor intensive and time consuming. 3. The hindfoot is heavy and the product is non-standardized in the sense that there is a large variation in the product depending on the technician making the product and the material used. 4. The technology is hand crafted and leads to unacceptable variations in the quality in addition to variations in the quality of microcellular rubber obtained from various sources. Most of the drawbacks were eliminated by the process fully described in copending applications bearing no. 1087/del/93 (Patent no. 187915) wherein we have claimed and described process for the preparation of ankle and fore/hindfoot components respectively. The process for the preparation of an artificial foot such as the Jaipur foot still required the tying of the individual components namely the ankle block,hindfoot block and the forefoot blocks with a nylon tyrecord. The components tied together were then used for the preparation of an artificial foot. The drawback in this process is that the labour involved and the skill involved in tying of the individual components of the foot. Failures resulted if the components were not tied together properly. The main object of this invention is therefore to provide a process for the preparation of the single insert using appropriate polyurcthane composition to give rigid, semi-rigid and flexible foam respectively. The single piece insert prepared by the process of this invention could then be used for the preparation of the artificial foot eliminating the procedure of tying the components. The polyurethane foam should be rigid for the ankle block part, semi-rigid in nature for the forefoot component and flexible in nature for the hindfoot component. The characteristics of the resultant foam are as follows : (a) The density of the foam should be in the range of 0.38 to 0.42 gm/cc. (b) The cell structure of the foam should be uniform. The present invention has been developed based on our finding that the three components namely, the ankle,fore foot arid the hind foot are held together firmly by the use of the appropriate polyurethane formulation. Since all the components rare made from appropriate polyurethane formulation the one piece insert can be postcured at one time instead of curing the individual components separately and the adhesion between the components is very good. Accordingly the present invention provides an improved process for the preparation of a one piece insert consisting of the components such as the ankle block.forefoot and the hindfoot useful in the preparation of an artificial foot which comprises a) coating the mold with relaxing agent such as herein described, b)casting flexible polyurethane formulation such as herein described for the hind foot c) allowing the formulation to solidify by maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, d) repeating step a), e)casting the rigid formulations such as herein described for the ankle and semirigid formulation such as herein described for fore foot wherein the order of casting can be varied, maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, f) demolding the one piece insert as obtained in steps c) and e) and postcuring the product at a temperature in the range of 80 to 100 deg.C for a period ranging from 2 to 4 hours. According to another feature of the invention the polyurethane for the ankle and fore foot components are prepared by the process described and claimed in our copending application numbers 1087/del/93(Patent no. 187915). In another copending application number 1086/DEL/93 we have described a process for the preparation of polyol useful for preparation of formulations and components such as ankle block. According to yet another feature of the invention, the formulation for the ankle component can be cast first followed by the casting of the fore foot and hind foot components. The order of casting the components can be varied to suit the convenience. According to yet another feature of the invention, since all the components are made from polyurethane formulation, adhesion between the different components are very good. According to yet another feature of the invention, preparation of all the components in a single mold helps in saving of considerable time and labour as the process described as per the process of this invention does not require the need to tie the components with tyre cords as is done in conventional foot components. The invention is described with reference to examples typically describing the casting of the ankle block, fore foot and hind fool components for the foot of si/.e 7. The examples given below should not however be construed to limit the scope this invention. The preparation of polyester polyol that forms the resin component and is useful for the preparation of the polyurethane hindlbot, forefoot component and the ankle block component of an artificial foot, such as the Jaipur foot may be done by any of the known conventional process. Preferably the polyol can be prepared by reacting a diacid with di or polyhydroxy compounds under inert atmosphere at temperatures in the range of 200 °C to 220 °C for a period ranging from 7 to 1 1 hours, in the presence of a polyesterificalion catalyst, continuously removing (lie water Ibimed timing the reaclion by using xylcnc and removing the product from the reactor. The reaction product, the polyol was obtained in the form of a viscous liquid. The di or polyhydroxy component is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and glycerin, Irimethylol propane and pentaerythrilol. 1 he diacid is selected from succinic acid, adipic acid, sebacic acid and the like. The polyesterification catalyst may be chosen from para toluene sulphonic acid and organometallic catalysis such as titanium tetra butoxide, Zinc di butoxide and the like. The invention is described with reference to examples typically describing the casting of the ankle block, fore foot and hind foot components Ibr the loot of size 7. The examples given below should not however be construed to limit the scope this invention. Polyol Preparation for the hindfoot/furcfoot: 768.69 grams of adipic acid, 668.78 I'lams of dielhylene glycol, 6.06 grams of para toluene sulphonie acid and 25 ml xylene were taken in a reaction vessel. The reaction vessel was a four necked round bottom flask equipped with mechanical stirrer for stirring the reactants, an opening for maintaining an inert atmosphere, provision for placing a thermowel to monitor the temperature of reaclion and an opening to fix a clean-stark apparatus. The reaclion assembly was set up after weighing the reactants. The dean-stark column was filled with xylene. The reaction mixture was heated from ambient temperature to a temperature of 120 °C at the rate of 4 °C per minute and 120 °C to 180 °C at the rate of 2 °C per minute. Acid value of the reaction mixture was continuously monitored during the heating c\cle and 129.9 grams of trimethylol propane was added to the reaction mixture at an acid value of 30 milligrams of potassium hydroxide per gram oi sample. Rcactanls held at 180 °C constant for 120 minutes. The temperature was further increased from 180 °C to 200 °C at the rate of 1 °C per minute. The reactants were held at this temperature for 3 hours and then the temperature was raised to 220 °C at the rate of 1 °C per minute and held at this temperature for 3.5 hours to get the polyester polyol. The reaction was monitored by acid value of the reaction mixture estimated by drawing the samples at various times during the course of reaction. When the acid value reached 13 milligrams ol potassium hydroxide per gram of sample, the xylene was removed from the dean-stark apparatus and the xylene present in the reaction mixture was started removing using fast purge of nitrogen. When the acid value of the batch reached below 2 milligrams of potassium hydroxide per gram of sample, the heating was stopped. When the reaction mixture reaches at 180 °C vacuum applied for 240 minutes. After that reaction mixture was cooled and discharged from the reactor. During the course of reaction an inert atmosphere was maintained by bubbling nitrogen gas and the reactants were stirred at an rpm of 250. The resultant polyol had acid value of 1.4 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 58.95 milligrams of potassium hydroxide per gram of sample and a viscosity of 6400 centipoise at 35 °C. Polyester Polyol Preparation for the ankle block : 375 grams of polyethylene tercphthalate waste in the form of powder or chips, 625 grams of ethylene glycol and 2.24 grams of zinc acetate were weighed in the reaction vessel. The reaction vessel had provision for stirring the reactants, an opening for maintaining an inert atmosphere, provision for placing a thermowel to monitor the temperature of reaction and an opening to fix a reflux condenser. After weighing the reactants, the reaction assembly was setup. The reactants were heated initially to a temperature of 100 °C at the rate of 3 °C per minute and from 100 °C to 200 °C at the rale of 2 °C per minute. The reactants were held at the temperature of 200°C for 8 hours. The reactants were stirred continuously at an rpm of 350. At the end of 8 hours the reactants were cooled to ambient temperature 10 get the glycolysed product. 779 grams of adipic acid and 2.00 grams of para toluene sulphonic acid were added to this mixture and reaction assembly was again setup by replacing reflux condenser with dean-stark assembly which was filled with xylene. 25 ml xylene was added to the reaction mixture and heated from ambient temperature to a temperature of 100 °C at 3 °C per minute and from 100 °C to 180 °C at 1° per minute. The reactants were held at this temperature for 3 hours and then the temperature was raised to 200 °C at the rate of 1 °C per minute and held at this temperature for 4 hours to get the polyester polyol. Water of reaction was continuously removed during the course of reaction. During the course of reaction an inert atmosphere was maintained by bubbling nitrogen gas and the reactants were stirred at an rpm of 150. The polyester polyol thus obtained is coded PETB-2. Casting procedure for the one piece insert involves the use of three appropriate formulations each for the ankle, the hindfoot and the forefoot components. The hindfoot is cast first, using dummy inserts for the other two components. The dummy inserts arc then removed and formulations for the other two components are poured into the mold which contains hindfoot cast earlier. The complete one piece insert is removed from the mold after all the components have cured in the mold. Example 1. liindfoot component Casting; '1 he mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 10 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 30 °C. To this resin component 36.51 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the R.PM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 30 °C for the period of 45 minutes. Fore Foot Block Casting :_ The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after removing the dummy inserts. Into a 250 ml glass beaker 70 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as here in before described, 9 parts of trimethylol propane, 0.15 parts of silicone surfactant and 0.25 parts of dibutyl tin dilauialc. 1 lie moisture content of the resin component was adjusted to 0.35% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 30 °C. To this resin component 32.91 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and toluene diisocyanate comprising of 80:20 isomer mixture. The reactants were mixed together using a high speed stirrer at the RPM of 1250 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the pouring hole was closed. Ankle Block Casting : A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered belter stability towards the external stresses and larger area (or the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that (lie bolt (Its tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold a mold release agent such as silicone grease for easy release of the molded article was applied after removing the dummy insert. Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETB- 2 & synthesized as described above, 10 parts of glycerol, 10 parts of wollastonite, 0.15 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.19% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 30 °C. To this resin component 38.52 grams of hardener component was added. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed stirrer at RPM of 1250 for the duration of 2 inin. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 30 °C for the period of 45 minutes after casting both the ankle and fore foot components. After 45 minutes, the single piece insert component was demolded and then postcured at 90 °C for a period of two hours. Example 2 Hindfoot component Casting : The mold was coated with mold release agent such as silicone grease for easy demolding of the cast component and closed tightly alter placing the dummy inserts. Into a 250 ml glass beaker 110 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 5 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of .slamious ocloale. 'I he moisture content of the lesin component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 35 °C. To this resin component 26.49 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 35°C for the period of 30 minutes. Ankle Block Casting : A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the loam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold coaling of silicone grease lor easy release of the molded article was ensured. Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETI3- 2 & synthesized as described in example 1, 12.50 parts of glycerol, 12.50 parts of wollastonite, 0.2 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.35% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 35 °C. To this resin component 39.55 grams of hardener component was added. Hardener component consisted of polymeric mclhylcnc diisocyanatc having the average functionality of 2.7, equivalent weight of 135 and 3 1% isocyanate. The rcactants were mixed together using a high speed stirrer at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grains of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 35 °C for the period of 30 minutes. Fore Foot Block Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy dcmolding of the molded component and closed tightly after removing the dummy insert. Into a 250 ml glass beaker 65 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 11 parts of trimethylol propane, 0.1 parts of silicone surfactant and 0.05 parts of dibutyl tin dilaurate and 0.05 parts of triethyl amine. The moisture content of the resin component was adjusted to 0.25% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 35 U(J. To this resin component 35.26 grams of hardener component was added. Hardener component consisted of 60/40 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1500 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 35 °C for the period of 30 minutes. The single piece insert component was demolded and then postcured at 80 °C for a period of four hours. Example 3 Hindfoot component Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 105 grams of resin component was weighed accurately. The polyol IIF-750 was a commercial material obtained from M/s Dai Ichi Karkaria Pvt. Ltd., Pimpri, Pune. IIF-750 is a branched polyol based on polypropylene giycol having an acid value of 0.07 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 25 milligrams of potassium hydroxide per gram of sample and viscosity of 850 centipoise at 35 °C. The resin component consisted of 100 parts of commercial polyol HF-750, 7.5 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. I he moisture content of the resin component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 33 °C. To this resin component 24.77 grams of hardener component was added. Prior to the addition of the hardener, the temperature was adjusted to 33 °C. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The rcactants were mixed together using a high speed sliner at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 33 °C for the period of 60 minutes. Ankle Block Casting : A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethnnc loam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coaled with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold coating of silicone grease for easy release of the molded article was ensured.Into a 250 nil glass beaker '10 grains of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalale based polyester polyol coded PETB- 2 & synthcsi/.ed as described in example 1, 10 parts of glycerol, 5 parts of butane diol, 0.1 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.25% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 33°C. To this resin component 41.51 grams of hardener component was added. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 3 1% isocyanale. The reactants were mixed together using a high speed stirrer at RPM of 1500 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 33 °C for the period of 45 minutes. Fore Foot Block Casting : The mold was properly coated with mold releasing silicone grease for easy demolding of the molded component and closed lightly after removing the dummy insert. Into a 250 ml glass beaker 80 grams of resin component was weighed accurately. The polyether polyol HF-750 was obtained from M/s Dai Ichi Karkaria Pvt. Ltd., Pimpri, Pune - 411 018. HF- 750 is a branched polyether polyol based on polypropylene glycol having an acid value of 0.07 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 25 milligrams of potassium hydroxide per gram of sample and viscosity of 850 centipoise at 35 °C. The resin component consisted of 100 parts of polyether polyol HF-750, 10 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 pails of stannous octoate. The moisture content of the resin component was adjusted to 0.3% by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 33 °C. To this resin component 21.67 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 35 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrcr at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initialed. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 33 °C for the period of 60 minutes. The single piece insert component was demoldecl and then postcured at 100 °C for a period of two hours. Example 4 Hindfoot component Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 3, 7 parts of trimethylol propane, 0.2 pails of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3 % and chocked by Kail Fischer Instrument. The temperature of the resin component was maintained at 32°C. To this resin component 4.45 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 32 °C for period up to 60 minutes. Ankle Block Casting : A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed after removing the dummy insert. Prior to the closing of the mold coating of silicone grease for easy release of the molded article was ensured. Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETB- 2 & synthesized as described in example 1, 12.50 parts of butane diol, 7.50 parts of wollastonite, 0.25 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.375% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 32 °C. To this resin component 39.05 grams of hardener component was added. Prior to the addition of the hardener temperature was maintained at 32 °C. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed stirrer at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 32 °C for the period of 60 minutes. Fore Foot Block Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy de-molding of the molded component and closed lightly after placing the dummy inserts. Into a 250 ml glass beaker 65 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 13 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 32 °C. To this resin component 32.70 grams of hardener component was added. Prior to the addition of the hardener, the temperature was maintained at 32°C. Hardener component consisted of 50/50 (\v/\v) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 32°C for a period up to 60 minutes. The single piece insert component was demolded and then postcured at 80 °C for a period up to four hours. Example 5 Hind foot Component Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grains of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol, 9 parts of trimethylol propane, 0.15 parts of silicone surfactant and 0.25 parts of dibutyl tin dilaurate. The moisture content of the resin component was adjusted to 0.35 % and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 27 °C. To this resin component 51.42 grams ol hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric melhylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and toluene diisocyanate comprising of 80:20 isomer mixture. The reaclants were mixed together using a high speed stirrer at the RPM of 1250 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the pouring hole was closed. The mold was kept at 27 °C for a period of 30 minutes. Ankle Block Casting : A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurelhane foam which offered better stability towards the external stresses and larger area lor the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric melhylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding belween the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior lo the closing of the mold coating of silicone grease for easy release of the molded article was ensured and the dummy insert was removed Into a 250 ml glass beaker 40 grains of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PE'I'B- 2 & synthesized as described in example 1, 12.50 parts of glycerol, 5 parts of butane diol, 12.50 parts of vvollastonitc, 0.2 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.175% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 27 °C. To this resin component 45.28 grams of hardener component was added. Prior to the addition of the hardener temperature was maintained at 27 °C. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed slirrcr at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 27 °C for the period of 40 minutes. Fore Foot Block Casting : The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after removing the dummy insert. Into a 250 ml glass beaker 80 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as per example 1, 15 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3% by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 27 °C. To this resin component 32.13 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric mcthylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed slirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 27 °C for the period of 60 minutes. The single piece insert component was demolded and then postcured at 90 °C for a period up to three hours. The insert thus prepared is used for preparation of an artificial foot by conventional methods. The following process can be given as illustrative only. The polyurethane components made as per the process of this invention offers following advantages : 1. The forefoot and hindfoot component are made from semi-rigid and flexible polyurethane foam to replace conventionally used laminated microcellular rubber block without compromising any physical property requirements. The ankle block component is made from rigid foam replacing the conventional wood. 2. The process of the present invention is less labor intensive. 3. The components of semi-rigid and flexible polyurelhane foams prepared using this process are standardized, offering advantages of consistent structure, dimensions and physical properties, thus ensuring product consistency. 4. The process of the present invention is amenable to tailor- making of materials with varying compressional characteristics to meet various needs of the patient. 5. The components made from semi-rigid and llcxihle polyuielhane loams are light weight as compared to the conventionally used microcellular rubber. A weight reduction up to 30% can be achieved. 6. The components prepared are amenable to faster processing. The foam preparation process can be adopted for well established automatic or semi-automatic foam preparation techniques. 7. The components consisting of rigid, semi-rigid and flexible polyurethane foam prepared using this process is resistant to water. 8. The components based on rigid, semi-rigid and flexible polyurethane foam described in the said invention is a water blown, non-CFC foam and is thus, environmentally safe process. 9. Since all the components are prepared in a single mold, considerable time and labour is saving is ensured. The process also eliminates the need to tie the individual components with nylon tyre cords as good adhesion is observed between the individual components of the foot. We Claim: 1. An improved process for the preparation of a one piece insert consisting of the components such as the ankle block,forefoot and the hindfoot useful in the preparation of an artificial foot which comprises a) coating the mold with relaxing agent such as herein described, b)casting flexible polyurethane formulation such as herein described for the hind foot c) allowing the formulation to solidify by maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, d) repeating step a), e)casting the rigid formulations such as herein described for the ankle and semirigid formulation such as herein described for fore foot wherein the order of casting can be varied, maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, f) demolding the one piece insert as obtained in steps c) and e) and postcuring the product at a temperature in the range of 80 to 100 deg.C for a period ranging from 2 to 4 hours. 2. An improved process for the preparation of a one piece insert consisting of the components such as the ankle block,forefoot and the hindfoot useful in the preparation of an artificial foot substantially as herein described with reference to the examples.

Full Text

This invention relates to an improved process for the preparation of a one piece insert useful for an artificial foot. The invention particularly relates to a process for the preparation of a one piece insert consisting of the components such as the ankle block,forefoot and the hindfoot. The one piece insert prepared by the process of the invention can be used for the preparation of an artificial foot such as the Jaipur foot. The process of the present invention is less labor intensive, cost effective and amenable to semi or automatic production techniques.
In our copending application number 1096/del/93 (Patent no. 187914) we have described and claimed a process for the preparation of polyol useful for ankle block preparation. In application nos. 1087/del/93(Patent no. 187915) we have claimed and described process for the preparation of ankle and fore/hindfoot components respectively. These components can be used in the preparation of an artificial foot such as the Jaipur foot by the process of the present invention.
Jaipur foot is an extensively used and very well accepted rehabilitation aid for the physically handicapped persons in this country. The number of amputees who have been fitted with these foot piece runs into hundreds and thousands. The utility of the foot has been well proven and there is a heavy demand from several countries including some of the advanced countries due to the mobility offered by the design, of the said foot.
A number of alternative rehabilitation aids for the physically handicapped are available from the western world. The major difficulty of these rehabilitation aids, not acceptable in our country is due to the differences in the life style of the persons affected. The western style of rehabilitation aids for the physically handicapped has closed shoe wearing norm in contrast to the needs of the patients of this country where
bare foot walking and use of well ventilated footwear for the warm climate is the preferred option. The Jaipur foot was first introduced in 1970 and though there have been design changes to suit the needs of the patients from time to time, the basic features continue to be followed.
The conventional Jaipur foot is made from wood laminates shaped to form the ankle block portion and microcellular rubber blocks for the forefoot and hind foot. The three components are held together by a nylon reinforced tyrecord and enclosed within a cover of skin colored solid elastomer. The foot has been used in tough field conditions and is very well accepted by the handicapped persons. The conventional hindfoot component preparation has the following drawbacks :
1. The ankle block is made from wood and shaped to give the shape of the
ankle and is highly labour intensive and requires special skill of the
worker so that the block is useful
2. The process for the hindfoot manufacturing involves preparation of
laminates of microcellular rubber and then manually carving the laminates
into a form of hindfoot. The process is thus highly labor intensive and time
consuming.
3. The hindfoot is heavy and the product is non-standardized in the sense that
there is a large variation in the product depending on the technician
making the product and the material used.
4. The technology is hand crafted and leads to unacceptable variations in the quality in addition to variations in the quality of microcellular rubber obtained from various sources.
Most of the drawbacks were eliminated by the process fully described in copending applications bearing no. 1087/del/93 (Patent no. 187915) wherein we have claimed and described process for the preparation of ankle and fore/hindfoot components respectively. The process for the preparation of an artificial foot such as the Jaipur foot still required the tying of the individual components namely the ankle block,hindfoot block and the forefoot blocks with a nylon tyrecord. The components tied together were then used for the preparation of an artificial foot. The drawback in this process is that the labour involved and the skill involved in tying of the individual components of the foot. Failures resulted if the components were not tied together properly.
The main object of this invention is therefore to provide a process for the preparation of the single insert using appropriate polyurcthane composition to give rigid, semi-rigid and flexible foam respectively. The single piece insert prepared by the process of this invention could then be used for the preparation of the artificial foot eliminating the procedure of tying the components. The polyurethane foam should be rigid for the ankle block part, semi-rigid in nature for the forefoot component and flexible in nature for the hindfoot component. The characteristics of the resultant foam are as follows :
(a) The density of the foam should be in the range of 0.38 to 0.42 gm/cc.
(b) The cell structure of the foam should be uniform.
The present invention has been developed based on our finding that the three components namely, the ankle,fore foot arid the hind foot are held together firmly by the use of the appropriate polyurethane formulation. Since all the components rare made from appropriate polyurethane formulation the one piece insert can be postcured at one time instead of curing the individual components separately and the adhesion between the components is very good.
Accordingly the present invention provides an improved process for the preparation of a one piece insert consisting of the components such as the ankle block.forefoot and the hindfoot useful in the preparation of an artificial foot which comprises a) coating the mold with relaxing agent such as herein described, b)casting flexible polyurethane formulation such as herein described for the hind foot c) allowing the formulation to solidify by maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, d) repeating step a), e)casting the rigid formulations such as herein described for the ankle and semirigid formulation such as herein described for fore foot wherein the order of casting can be varied, maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period upto 60 minutes, f) demolding the one piece insert as obtained in steps c) and e) and postcuring the product at a temperature in the range of 80 to 100 deg.C for a period ranging from 2 to 4 hours.
According to another feature of the invention the polyurethane for the ankle and fore foot components are prepared by the process described and claimed in our copending application numbers 1087/del/93(Patent no. 187915).
In another copending application number 1086/DEL/93 we have described a process for the preparation of polyol useful for preparation of formulations and components such as ankle block.
According to yet another feature of the invention, the formulation for the ankle component can be cast first followed by the casting of the fore foot and hind foot components. The order of casting the components can be varied to suit the convenience.
According to yet another feature of the invention, since all the components are made from polyurethane formulation, adhesion between the different components are very good.
According to yet another feature of the invention, preparation of all the components in a single mold helps in saving of considerable time and labour as the process described as per the process of this invention does not require the need to tie the components with tyre cords as is done in conventional foot components.
The invention is described with reference to examples typically describing the casting of the ankle block, fore foot and hind fool components for the foot of si/.e 7. The examples given below should not however be construed to limit the scope this invention.
The preparation of polyester polyol that forms the resin component and is useful for the preparation of the polyurethane hindlbot, forefoot component and the ankle block component of an artificial foot, such as the Jaipur foot may be done by any of the known conventional process.
Preferably the polyol can be prepared by reacting a diacid with di or polyhydroxy compounds under inert atmosphere at temperatures in the range of 200 °C
to 220 °C for a period ranging from 7 to 1 1 hours, in the presence of a polyesterificalion catalyst, continuously removing (lie water Ibimed timing the reaclion by using xylcnc and removing the product from the reactor. The reaction product, the polyol was obtained in the form of a viscous liquid. The di or polyhydroxy component is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and glycerin, Irimethylol propane and pentaerythrilol. 1 he diacid is selected from succinic acid, adipic acid, sebacic acid and the like. The polyesterification catalyst may be chosen from para toluene sulphonic acid and organometallic catalysis such as titanium tetra butoxide, Zinc di butoxide and the like.
The invention is described with reference to examples typically describing the casting of the ankle block, fore foot and hind foot components Ibr the loot of size 7. The examples given below should not however be construed to limit the scope this invention. Polyol Preparation for the hindfoot/furcfoot:
768.69 grams of adipic acid, 668.78 I'lams of dielhylene glycol, 6.06 grams of para toluene sulphonie acid and 25 ml xylene were taken in a reaction vessel. The reaction vessel was a four necked round bottom flask equipped with mechanical stirrer for stirring the reactants, an opening for maintaining an inert atmosphere, provision for placing a thermowel to monitor the temperature of reaclion and an opening to fix a clean-stark apparatus. The reaclion assembly was set up after weighing the reactants. The dean-stark column was filled with xylene. The reaction mixture was heated from ambient temperature to a temperature of 120 °C at the rate of 4 °C per minute and 120 °C to 180 °C at the rate of 2 °C per minute. Acid value of the reaction mixture was continuously monitored during the heating c\cle and 129.9 grams of trimethylol propane
was added to the reaction mixture at an acid value of 30 milligrams of potassium hydroxide per gram oi sample. Rcactanls held at 180 °C constant for 120 minutes. The temperature was further increased from 180 °C to 200 °C at the rate of 1 °C per minute. The reactants were held at this temperature for 3 hours and then the temperature was raised to 220 °C at the rate of 1 °C per minute and held at this temperature for 3.5 hours to get the polyester polyol. The reaction was monitored by acid value of the reaction mixture estimated by drawing the samples at various times during the course of reaction. When the acid value reached 13 milligrams ol potassium hydroxide per gram of sample, the xylene was removed from the dean-stark apparatus and the xylene present in the reaction mixture was started removing using fast purge of nitrogen. When the acid value of the batch reached below 2 milligrams of potassium hydroxide per gram of sample, the heating was stopped. When the reaction mixture reaches at 180 °C vacuum applied for 240 minutes. After that reaction mixture was cooled and discharged from the reactor. During the course of reaction an inert atmosphere was maintained by bubbling nitrogen gas and the reactants were stirred at an rpm of 250. The resultant polyol had acid value of 1.4 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 58.95 milligrams of potassium hydroxide per gram of sample and a viscosity of 6400 centipoise at 35 °C. Polyester Polyol Preparation for the ankle block :
375 grams of polyethylene tercphthalate waste in the form of powder or chips, 625 grams of ethylene glycol and 2.24 grams of zinc acetate were weighed in the reaction vessel. The reaction vessel had provision for stirring the reactants, an opening for maintaining an inert atmosphere, provision for placing a thermowel to monitor the
temperature of reaction and an opening to fix a reflux condenser. After weighing the reactants, the reaction assembly was setup. The reactants were heated initially to a temperature of 100 °C at the rate of 3 °C per minute and from 100 °C to 200 °C at the rale of 2 °C per minute. The reactants were held at the temperature of 200°C for 8 hours. The reactants were stirred continuously at an rpm of 350. At the end of 8 hours the reactants were cooled to ambient temperature 10 get the glycolysed product. 779 grams of adipic acid and 2.00 grams of para toluene sulphonic acid were added to this mixture and reaction assembly was again setup by replacing reflux condenser with dean-stark assembly which was filled with xylene. 25 ml xylene was added to the reaction mixture and heated from ambient temperature to a temperature of 100 °C at 3 °C per minute and from 100 °C to 180 °C at 1° per minute. The reactants were held at this temperature for 3 hours and then the temperature was raised to 200 °C at the rate of 1 °C per minute and held at this temperature for 4 hours to get the polyester polyol. Water of reaction was continuously removed during the course of reaction. During the course of reaction an inert atmosphere was maintained by bubbling nitrogen gas and the reactants were stirred at an rpm of 150. The polyester polyol thus obtained is coded PETB-2. Casting procedure for the one piece insert involves the use of three appropriate formulations each for the ankle, the hindfoot and the forefoot components. The hindfoot is cast first, using dummy inserts for the other two components. The dummy inserts arc then removed and formulations for the other two components are poured into the mold which contains hindfoot cast earlier. The complete one piece insert is removed from the mold after all the components have cured in the mold.
Example 1. liindfoot component Casting;
'1 he mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 10 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 30 °C. To this resin component 36.51 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the R.PM of
1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 30 °C for the period of 45 minutes.
Fore Foot Block Casting :_
The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after removing the dummy inserts. Into a 250 ml glass beaker 70 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized
as here in before described, 9 parts of trimethylol propane, 0.15 parts of silicone surfactant and 0.25 parts of dibutyl tin dilauialc. 1 lie moisture content of the resin component was adjusted to 0.35% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 30 °C. To this resin component 32.91 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and toluene diisocyanate comprising of 80:20 isomer mixture. The reactants were mixed together using a high speed stirrer at the RPM of 1250 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the pouring hole was closed. Ankle Block Casting :
A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered belter stability towards the external stresses and larger area (or the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that (lie bolt (Its tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher
shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold a mold release agent such as silicone grease for easy release of the molded article was applied after removing the dummy insert. Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETB- 2 & synthesized as described above, 10 parts of glycerol, 10 parts of wollastonite, 0.15 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.19% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 30 °C. To this resin component 38.52 grams of hardener component was added. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed stirrer at RPM of 1250 for the duration of 2 inin. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 30 °C for the period of 45 minutes after casting both the ankle and fore foot components. After 45 minutes, the single piece insert component was demolded and then postcured at 90 °C for a period of two hours.
Example 2 Hindfoot component Casting :
The mold was coated with mold release agent such as silicone grease for easy demolding of the cast component and closed tightly alter placing the dummy inserts. Into a 250 ml glass beaker 110 grams of resin component was weighed accurately. The resin
component consisted of 100 parts of polyester polyol synthesized as described in example 1, 5 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of .slamious ocloale. 'I he moisture content of the lesin component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 35 °C. To this resin component 26.49 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 35°C for the period of 30 minutes. Ankle Block Casting :
A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the loam and the bolt. The
improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold coaling of silicone grease lor easy release of the molded article was ensured.
Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETI3- 2 & synthesized as described in example 1, 12.50 parts of glycerol, 12.50 parts of wollastonite, 0.2 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.35% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 35 °C. To this resin component 39.55 grams of hardener component was added. Hardener component consisted of polymeric mclhylcnc diisocyanatc having the average functionality of 2.7, equivalent weight of 135 and 3 1% isocyanate. The rcactants were mixed together using a high speed stirrer at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grains of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 35 °C for the period of 30 minutes. Fore Foot Block Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy dcmolding of the molded component and closed tightly after removing the dummy insert. Into a 250 ml glass beaker 65 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 11 parts of trimethylol propane, 0.1 parts of silicone surfactant and 0.05 parts of dibutyl tin dilaurate and 0.05
parts of triethyl amine. The moisture content of the resin component was adjusted to 0.25% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 35 U(J. To this resin component 35.26 grams of hardener component was added. Hardener component consisted of 60/40 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1500 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 35 °C for the period of 30 minutes. The single piece insert component was demolded and then postcured at 80 °C for a period of four hours.
Example 3 Hindfoot component Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 105 grams of resin component was weighed accurately. The polyol IIF-750 was a commercial material obtained from M/s Dai Ichi Karkaria Pvt. Ltd., Pimpri, Pune. IIF-750 is a branched polyol based on polypropylene giycol having an acid value of 0.07 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 25 milligrams of potassium hydroxide per gram of sample and viscosity of 850 centipoise at 35 °C. The resin component consisted of 100 parts of commercial polyol HF-750, 7.5 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. I he moisture content of the resin
component was adjusted to 0.3 % by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 33 °C. To this resin component 24.77 grams of hardener component was added. Prior to the addition of the hardener, the temperature was adjusted to 33 °C. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The rcactants were mixed together using a high speed sliner at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 33 °C for the period of 60 minutes. Ankle Block Casting :
A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethnnc loam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coaled with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher
shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior to the closing of the mold coating of silicone grease for easy release of the molded article was ensured.Into a 250 nil glass beaker '10 grains of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalale based polyester polyol coded PETB- 2 & synthcsi/.ed as described in example 1, 10 parts of glycerol, 5 parts of butane diol, 0.1 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.25% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 33°C. To this resin component 41.51 grams of hardener component was added. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 3 1% isocyanale. The reactants were mixed together using a high speed stirrer at RPM of 1500 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 33 °C for the period of 45 minutes. Fore Foot Block Casting :
The mold was properly coated with mold releasing silicone grease for easy demolding of the molded component and closed lightly after removing the dummy insert. Into a 250 ml glass beaker 80 grams of resin component was weighed accurately. The polyether polyol HF-750 was obtained from M/s Dai Ichi Karkaria Pvt. Ltd., Pimpri, Pune - 411 018. HF- 750 is a branched polyether polyol based on polypropylene glycol having an acid value of 0.07 milligrams of potassium hydroxide per gram of sample, hydroxyl value of 25 milligrams of potassium hydroxide per gram of sample and
viscosity of 850 centipoise at 35 °C. The resin component consisted of 100 parts of polyether polyol HF-750, 10 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 pails of stannous octoate. The moisture content of the resin component was adjusted to 0.3% by addition of desired quantity of water and checked by Karl Fischer Instrument. The temperature of the resin component was adjusted to 33 °C. To this resin component 21.67 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 35 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrcr at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initialed. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 33 °C for the period of 60 minutes. The single piece insert component was demoldecl and then postcured at 100 °C for a period of two hours.
Example 4 Hindfoot component Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 3, 7 parts of trimethylol propane, 0.2 pails of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3 %
and chocked by Kail Fischer Instrument. The temperature of the resin component was maintained at 32°C. To this resin component 4.45 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 32 °C for period up to 60 minutes. Ankle Block Casting :
A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurethane foam which offered better stability towards the external stresses and larger area for the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric methylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding between the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed after
removing the dummy insert. Prior to the closing of the mold coating of silicone grease for easy release of the molded article was ensured.
Into a 250 ml glass beaker 40 grams of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PETB- 2 & synthesized as described in example 1, 12.50 parts of butane diol, 7.50 parts of wollastonite, 0.25 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.375% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 32 °C. To this resin component 39.05 grams of hardener component was added. Prior to the addition of the hardener temperature was maintained at 32 °C. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed stirrer at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 32 °C for the period of 60 minutes. Fore Foot Block Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy de-molding of the molded component and closed lightly after placing the dummy inserts. Into a 250 ml glass beaker 65 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as described in example 1, 13 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to
0.3% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 32 °C. To this resin component 32.70 grams of hardener component was added. Prior to the addition of the hardener, the temperature was maintained at 32°C. Hardener component consisted of 50/50 (\v/\v) mixture of polymeric methylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed stirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 32°C for a period up to 60 minutes.
The single piece insert component was demolded and then postcured at 80 °C for a period up to four hours.
Example 5 Hind foot Component Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after placing the dummy inserts. Into a 250 ml glass beaker 100 grains of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol, 9 parts of trimethylol propane, 0.15 parts of silicone surfactant and 0.25 parts of dibutyl tin dilaurate. The moisture content of the resin component was adjusted to 0.35 % and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 27 °C. To this resin component 51.42 grams ol hardener component was
added. Hardener component consisted of 50/50 (w/w) mixture of polymeric melhylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and toluene diisocyanate comprising of 80:20 isomer mixture. The reaclants were mixed together using a high speed stirrer at the RPM of 1250 for a period up to 2 min. or till the foaming of polymer was initiated. 125 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the pouring hole was closed. The mold was kept at 27 °C for a period of 30 minutes. Ankle Block Casting :
A mild steel bolt of length 105 mm and diameter 8 mm was taken and thoroughly cleaned to remove all the rust. A circular disk of 30 mm diameter was taken and four holes of 3 mm diameter were made. This disk was welded to the bolt head. This bolt design allowed interlocking with the polyurelhane foam which offered better stability towards the external stresses and larger area lor the distributing the external stresses which directly come onto the ankle block component of the foot. At 55 mm from the bolt head the screw was marked with the teflon tape so that the bolt fits tightly in the sleeve provided in the ankle block mold. The remaining portion of the bolt containing circular disk was wiped with solvent to remove all the greasy material and coated with polymeric melhylene diisocyanate for improved bonding between the foam and the bolt. The improved bonding belween the foam and bolt allows ankle block to withstand higher shearing forces. The sleeve was fitted into the mold and the mold was closed. Prior lo the closing of the mold coating of silicone grease for easy release of the molded article was ensured and the dummy insert was removed
Into a 250 ml glass beaker 40 grains of resin component was weighed accurately. The resin component consisted of 100 parts of the polyethylene terephthalate based polyester polyol coded PE'I'B- 2 & synthesized as described in example 1, 12.50 parts of glycerol, 5 parts of butane diol, 12.50 parts of vvollastonitc, 0.2 parts of silicone surfactant. The moisture content of the resin component was adjusted to 0.175% and checked by Karl Fischer Instrument. The temperature of the resin component was maintained at 27 °C. To this resin component 45.28 grams of hardener component was added. Prior to the addition of the hardener temperature was maintained at 27 °C. Hardener component consisted of polymeric methylene diisocyanate having the average functionality of 2.7, equivalent weight of 135 and 31% isocyanate. The reactants were mixed together using a high speed slirrcr at RPM of 1000 for the duration of 2 min. or till the foaming of polymer was initiated. 62 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials using funnel and the mold was closed. The mold was kept at 27 °C for the period of 40 minutes. Fore Foot Block Casting :
The mold was properly coated with mold releasing agent such as silicone grease for easy demolding of the molded component and closed tightly after removing the dummy insert. Into a 250 ml glass beaker 80 grams of resin component was weighed accurately. The resin component consisted of 100 parts of polyester polyol synthesized as per example 1, 15 parts of trimethylol propane, 0.2 parts of silicone surfactant and 0.05 parts of stannous octoate. The moisture content of the resin component was adjusted to 0.3% by addition of desired quantity of water and checked by Karl Fischer
Instrument. The temperature of the resin component was adjusted to 27 °C. To this resin component 32.13 grams of hardener component was added. Hardener component consisted of 50/50 (w/w) mixture of polymeric mcthylene diisocyanate having the functionality of 2.7 and equivalent weight of 135 and 80:20 toluene diisocyanate. The reactants were mixed together using a high speed slirrer at the RPM of 1000 for a period up to 2 min. or till the foaming of polymer was initiated. 95 grams of this reaction mixture was transferred into the closed mold through the hole provided for pouring of the materials and the mold was closed. The mold was kept at 27 °C for the period of 60 minutes. The single piece insert component was demolded and then postcured at 90 °C for a period up to three hours.
The insert thus prepared is used for preparation of an artificial foot by conventional methods. The following process can be given as illustrative only.
The polyurethane components made as per the process of this invention offers following advantages :
1. The forefoot and hindfoot component are made from semi-rigid and flexible
polyurethane foam to replace conventionally used laminated microcellular rubber
block without compromising any physical property requirements. The ankle block
component is made from rigid foam replacing the conventional wood.
2. The process of the present invention is less labor intensive.
3. The components of semi-rigid and flexible polyurelhane foams prepared using this
process are standardized, offering advantages of consistent structure, dimensions and
physical properties, thus ensuring product consistency.
4. The process of the present invention is amenable to tailor- making of materials with
varying compressional characteristics to meet various needs of the patient.
5. The components made from semi-rigid and llcxihle polyuielhane loams are light
weight as compared to the conventionally used microcellular rubber. A weight
reduction up to 30% can be achieved.
6. The components prepared are amenable to faster processing. The foam preparation
process can be adopted for well established automatic or semi-automatic foam
preparation techniques.
7. The components consisting of rigid, semi-rigid and flexible polyurethane foam
prepared using this process is resistant to water.
8. The components based on rigid, semi-rigid and flexible polyurethane foam described
in the said invention is a water blown, non-CFC foam and is thus, environmentally
safe process.
9. Since all the components are prepared in a single mold, considerable time and labour
is saving is ensured. The process also eliminates the need to tie the individual
components with nylon tyre cords as good adhesion is observed between the
individual components of the foot.

We Claim:
1. An improved process for the preparation of a one piece insert consisting of the
components such as the ankle block,forefoot and the hindfoot useful in the
preparation of an artificial foot which comprises a) coating the mold with
relaxing agent such as herein described, b)casting flexible polyurethane
formulation such as herein described for the hind foot c) allowing the formulation
to solidify by maintaining the mold at a temperature in the range of 27 to 35
deg.C for a period upto 60 minutes, d) repeating step a), e)casting the rigid
formulations such as herein described for the ankle and semirigid formulation
such as herein described for fore foot wherein the order of casting can be varied,
maintaining the mold at a temperature in the range of 27 to 35 deg.C for a period
upto 60 minutes, f) demolding the one piece insert as obtained in steps c) and e)
and postcuring the product at a temperature in the range of 80 to 100 deg.C for a
period ranging from 2 to 4 hours.
2. An improved process for the preparation of a one piece insert consisting of the
components such as the ankle block,forefoot and the hindfoot useful in the
preparation of an artificial foot substantially as herein described with reference to
the examples.

Documents:

501-del-1998-abstract.pdf

501-del-1998-claims.pdf

501-del-1998-complete specification (granted).pdf

501-del-1998-correspondence-others.pdf

501-del-1998-correspondence-po.pdf

501-del-1998-description (complete).pdf

501-del-1998-form-1.pdf

501-del-1998-form-19.pdf

501-del-1998-form-2.pdf

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Patent Number

194808

Indian Patent Application Number

501/DEL/1998

PG Journal Number

49/2004

Publication Date

04-Dec-2004

Grant Date

17-Mar-2006

Date of Filing

26-Feb-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG NEW DELHI 110001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	VIKAS MADHUSUDAN NADKARNI	10,NARENDRA HOUSING SOCIETY SENAPATI BAPAT MARG,PUNE - 411016,INDIA
2	SANDEEPAK BALKRISHNA PANDIT	11 NISARGA HOUSING SOCIETY, SOCIETY,MANISHA NAGAR,KALWA,THENE BOMBAY-400 607
3	PRAVHAKAR SADASHIV PATIL	28/11 SHIVNAI BUILDING, INDRAYANI NAGAR,BHOSARI,PUNE -411 026,INDIA
4	OMPRAKASH SHRINI VAS YEMUL	EX-NATIONAL CHEMICAL LABORTORY PUNE MAHRASTRA INDIA
5	CHELANATTU KHIZHAKKE MADATH RAMAN RAJAN	EX-NATIONAL CHEMICAL LABORTORY PUNE MAHRASTRA INDIA

PCT International Classification Number

A47B 007/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA