Title of Invention

"A PROCESS FOR THE MANUFACTURE OF EMBOSSING ROLLERS AND EMBOSSING ROLLERS MANUFACTURED THEREBY"

Abstract

The present invention discloses a process for the manufacture of embossing rollers, which consists a pair of opposing steel embossing rollers. The process describes the method of manufacturing for profiled pins at a fine pitch and configuration and a plasma nitriding process for providing a hard surface. The novelty of wear resistant, smooth surface and high surface hardness embossing rollers has been achieved by the combination of profile turning, high precision optical profile grinding, plasma nitriding and physical vapor deposition (PVD) process coating in the manufacturing process of embossing rollers. The development of embossing rollers is used for embossing on metal foil, metallized paper, paper or plastic sheets.

Full Text

The present invention relates to a process for the manufacture of embossing rollers and embossing rollers manufactured thereby. The present invention particularly relates to a process for the manufacture of embossing rollers, which consists a pair of opposing steel embossing rollers and provides embossing rollers manufactured by the process of the present invention. The main usage of the present invention is for the development of embossing rollers, which are used for embossing on metal foil, metallized paper, paper or plastic sheets. Such embossing is used to stiffen the sheet. It increases the stiffness of the paper/foil thereby helps packing goods such as cigarettes in an automatic packing machine. Another particular usage of the present invention is in pharmaceutical industries. Tablets/capsules are placed between sheets of foil paper and embossed around the tablet/capsules. This helps to seal the pharmaceutical products from the atmosphere. Reference may be made to US patent no. 5,007,271 and US patent no. 6,176,819, which is an improvement of US patent no. 5,007,271. US patent No. 5,007,271 describes a device and a method for embossing a metal foil, wherein a metal foil is passed between two similarly toothed rollers positioned so that the teeth of each roller engages the teeth of the other. A high-quality embossing is obtained which may be kept practically constant over long periods of operation. The rollers are mutually synchronized such that only one of these rollers need be coupled with a driving mechanism. The other roller is free and may easily be removed, replaced or adjusted in order to vary the force by which it is pressed against the foil and the driven roller respectively. This patent suggests that the axial grooves between adjacent rows of teeth may be machined by a slotting tool while the circumferential grooves may be machined by turning. US patent no. 6,176,819, describes a device and a method for embossing a foil, wherein the embossing process is effected between a pair of embossing rollers provided with toothings of the same kind which comprise rows of pyramidal teeth extending in the axial and the circumferential directions. Compared to the theoretical pyramid shape, the heads of the teeth are flattened while the edges of the pyramids are cut. The rollers, which are mutually displaceable in the axial direction, are thus able to catch in a stable mutual position of maximum penetration and to remain in this position in operation. In this patent edges of the pins are flattened by using etching process. Control of etching process is very much difficult for fine and deep structures especially at small pitch intervals. The drawbacks of the above patents are 1) producing burr in the machined pins and 2) profile error from pin to pin due to wear out of the formed cutters which were getting blunt. Such variations will not be easy to detect and correct in a milling or turning operation. These profile variations can affect the quality of embossing. Reference may be made to EP Patent No. 1245376, which describes a device for applying an embossing to a web of tissue paper and method thereof using one or more steel rollers in combination with rubber rollers. The rubber rollers have a yielding surface. A raised embossing pattern on the steel roller elastically presses into the rubber roller, so that the tissue paper fed between the rubber roller and the steel roller is imparted an embossing pattern into the sheet. The drawback of this method is uneven wear due to larger difference in the wear resistance of the matching rollers can affect the quality of embossing and also bring down the life of the rollers. Reference may be made to EP Patent No. 1155815 and CA Patent No.2347963, which describe an embossing roller has a relief pattern, defined on its surface for embossing onto multiple ply sheet material by compressing the material against another roller or similar surface. In this method the relief pattern and the projections are provided by an etching process. The drawbacks of this method are: 1. It is difficult to etch structures that are fine and deep, especially at small pitch intervals. For instance the pins in the embossing rollers, which is typically 100 µm wide and about 200 µm deep. This process is useful only for coarser patterns that are used in textile industry where accuracy is not needed. 2. The two rollers have large differences in wear properties. Hence there can be uneven wear leading to poor quality embossing with use. 3. Life will also be poor. The embossing normally has an array of pyramidal projections at regular pitch. Embossing operations are performed with plastic rollers or combinations of plastic and steel rollers or pair of steel rollers. As stated, the prior state of art on manufacturing of embossing rollers reflects several drawbacks. The Major challenge in the development of a process for the manufacture of embossing rollers is high precision profile generation and surface hardening without affecting the profile accuracy. Hence there is definite need for the improvement of a process for the manufacture of embossing rollers in order to get good quality embossing rollers and embossed products. The main object of the present invention is to provide an improved process for the manufacture of embossing rollers, which obviates the drawbacks of earlier methods. Another object of the present invention is to provide a cost effective method for the manufacture of embossing rollers. Yet another object of the present invention is to provide a smooth and burrs free surface profile for embossing rollers. Still another object of the present invention is to provide a dry process embossing without any lubricant for the embossing rollers. A further object of the present invention is to provide a surface modification of the rollers so as to enhance the wear resistance of the roller. A still further object of the present invention is to provide steel or steel rollers for the development of embossing rollers. Another object of the present invention is to provide a process for the manufacture of embossing rollers, which consists a pair of opposing steel embossing rollers. Yet another object of the present invention is to provide embossing rollers manufactured by the process of the present invention. Fig.1 represents one of the two embossing roller profile details comprising Pitch(P), Angle (9), Depth (D) and Crest radius (C). Fig.2 represents the other of the two embossing roller profile details comprising Pitch(P), Angle(9), Depth (D) and Crest radius (C). Fig.3 depicts the both rollers assembled together in the machine frame for the embossing pattern of a profile wherein part No.1 is one of the two embossing rollers and part No.2 is the other of the two embossing rollers. The present invention discloses a process for the manufacture of embossing rollers and embossing rollers manufactured thereby. The process of the present invention provides a method of manufacturing embossing rollers which consists a pair of opposing steel embossing rollers. The process particularly describes a novel method of manufacturing for profiled pins at a fine pitch and configuration and a plasma nitriding process for providing a hard surface. The novelty of wear resistant, smooth surface and high surface hardness embossing rollers has been achieved by the combination of profile turning, high precision optical profile grinding, plasma nitriding and physical vapor deposition (PVD) process coating in the manufacturing process of embossing rollers. Accordingly the present invention provides a process for the manufacture of embossing rollers, which comprises: a) turning of steel rod, b) drilling and tapping of rods, c) key way slotting and rough machining, d) toughening to 28-32 HRC, e) grinding on the mandrel, f) outer profile turning, g) induction hardening to 40-45 HRC, to obtain roller(s); characterized in that the said roller(s) being subjected to: h) preliminary plasma nitriding, i) optical profile grinding of circular and axial grooves, j) key way finishing by spark erosion, k) overall length finishing by surface grinding, I) running the rollers with abrasive suspension, m) secondary plasma nitriding, n) deep cryo treatment, o) physical vapor deposition (PVD) coating, p) inspecting for required profile of rollers and q) assembling with appropriately machined shaft to obtain embossing roller(s). In an embodiment of the present invention the steel used for making rollers may be EN 40B or of any other equivalent quality. In another embodiment of the present invention, the thickness and the depth of the pins are decided on the impression and the material hardness. In yet another embodiment of the present invention, the pins of the roller are suitable for soft material like paper, aluminum and copper or harder material like steel. In still yet another embodiment of the present invention, abrasive suspension is prepared in water or oil containing suitable inhibitors for preventing erosion. In a further embodiment of the present invention, abrasive suspension contains elements of silicon carbide or aluminum oxide dissolved in water or oil. In a still further embodiment of the present invention, PVD coating material may be selected from chromium nitride, titanium nitride or aluminum nitride. In another embodiment of the present invention, PVD coating may be used with or without deep cryo treatment. In yet another embodiment of the present invention, pitch of the pins of embossing roller is in the range of 0.395 to 0.405 mm. In still another embodiment of the present invention, included angle between the pins of embossing roller is between 58° and 102° In still yet another embodiment of the present invention, depth of pins of embossing roller can be 0.140 to 0.200 mm. In one more embodiment of the present invention, minimum crest radius required for the formation of pins of embossing roller is 0.03 to 0.05mm. Accordingly the present invention provides embossing rollers manufactured by the process of the present invention as described herein. In an embodiment of present invention, the diameter of top and bottom roller may be equal or different. In another embodiment of present invention, diameter of top roller may be of bigger size than the bottom roller. The process of the present invention for the manufacture of embossing rollers use combination of profile turning and profile grinding process. This has brought down the number of profile grinding hours and the manufacturing cost of embossing rollers. The plasma nitriding process has been developed for the surface hardening of embossing rollers. The plasma nitriding process is eco-friendly and does not produce dimensional distortion. The process has been developed to provide a wear resistant nitride layer, which is free from white layer and has a good depth, high surface hardness and no porosity. The plasma nitriding process improves the wear resistance, antifriction property, corrosion resistance and hardness of components. The PVD process still further improves the wear resistance of components. In the process of the present invention for the manufacture of embossing rollers the novelty of wear resistant, smooth surface and high surface hardness embossing rollers have been achieved by the combination of profile turning, high precision optical profile grinding, plasma nitriding and PVD process coating in the manufacturing process of embossing rollers. In the present invention particularly relating to a process for the manufacture of embossing rollers, which consists of a pair of opposing steel embossing rollers and provides embossing rollers manufactured by the process of the present invention, the non-obvious inventive steps are: (i) preliminary plasma nitriding, (ii) optical profile grinding of circular and axial grooves, (iii) running the rollers with abrasive suspension, (iv) secondary plasma nitriding, and (v) PVD coating. In the present invention there is provided a process for the manufacture of embossing rollers and the present invention provides embossing rollers manufactured thereby. The sequence of manufacturing process steps is as follows: 1. Internal and outer (ID, OD) turning of rods as per drawing. 2. Drilling and tapping. 3. Key way slotting and rough machining. 4. Toughening to 28-32 HRC. 5. ID grinding and OD grinding on mandrel (with reference to ID) to the required dimension. 6. Outer profile turning on CNC machine. 7. Induction hardening to 40-45 HRC. 8. First plasma nitriding to the required case depth, which may be varied suitably for the depth of the grooves. 9. Optical profile grinding of circumferential grooves and axial grooves to appropriate depth. 10. Key way finishing (by spark erosion). 11. Overall length finishing by surface grinding. 12. Running the rollers with abrasive suspension (silicon carbide or aluminum oxide). 13. Plasma nitriding to the required case depth. 14. Inspection. 15. Assembly with appropriately machined shaft. The following examples are given by way of illustration of the present invention in actual practice and should not be construed to limit the scope of the present invention. Example 1 Embossing rollers were manufactured by the process of the present invention as described above. Each head had a set of two rollers. Bottom roller had a diameter of 60 mm and the diameter of the top roller was 120 mm. Embossing width was of the order of 100 mm. Bottom roller was driven by a motor through appropriate gear, top roller was pressed against the bottom roller by springs. Both the rollers were mounted on needle bearings. The embossing rollers were used for embossing an array of small squares in X and Y directions on aluminum foil as well as aluminized paper. Foil/metallized paper was fed between the rollers with the metal surface contacting the outer diameter of smaller roller. Fine pins located at a pitch of 0.4 mm on outer surface of both the rollers were produced during embossing. Example 2 Embossing rollers were manufactured by the process of the present invention as described above. Each head had a set of two rollers. Bottom roller had a diameter of 49 mm and the diameter of the top roller was 98 mm. Embossing width was of the order of 145 mm. Bottom roller was driven by a motor through appropriate gear, top roller was pressed against the bottom roller by springs. Both the rollers were mounted on needle bearings. The embossing rollers were used for embossing an array of small squares in X and Y directions on aluminum foil as well as aluminized paper. Foil/metallized paper was fed between the rollers with the metal surface contacting the outer diameter of smaller roller. Fine pins located at a pitch of 0.4 mm on outer surface of both the rollers were produced during embossing. Example 3 Embossing rollers were manufactured by the process of the present invention as described above. Each head had a set of two rollers. Bottom roller and top roller was of diameter of 74.2 mm. Embossing width was of the order of 126 mm. Bottom roller was driven by a motor through appropriate gear, top roller was pressed against the bottom roller by springs. Both the rollers were mounted on needle bearings. The embossing rollers were used for embossing an array of small squares in X and Y directions on aluminum foil as well as aluminized paper. Foil/metallized paper was fed between the rollers with the metal surface contacting the outer diameter of smaller roller. Fine pins located at a pitch of 0.4 mm on outer surface of both the rollers were produced during embossing. Example 4 Embossing rollers were manufactured by the process of the present invention as described above. Each head had a set of two rollers. Bottom roller and top roller was of diameter of 71.1 mm. Embossing width was of the order of 130 mm. Bottom roller was driven by a motor through appropriate gear, top roller was pressed against the bottom roller by springs. Both the rollers were mounted on needle bearings. The embossing rollers were used for embossing an array of small squares in X and Y directions on aluminum foil as well as aluminized paper. Foil/metallized paper was fed between the rollers with the metal surface contacting the outer diameter of smaller roller. Fine pins located at a pitch of 0.4 mm on outer surface of both the rollers were produced during embossing. Example 5 Embossing rollers were manufactured by the process of the present invention as described above. Each head had a set of two rollers. Bottom roller and top roller was of diameter of 57.4 mm. Embossing width was of the order of 100 mm. Bottom roller was driven by a motor through appropriate gear, top roller was pressed against the bottom roller by springs. Both the rollers were mounted on needle bearings. The embossing rollers were used for embossing an array of small squares in X and Y directions on aluminum foil as well as aluminized paper. Foil/metallized paper was fed between the rollers with the metal surface contacting the outer diameter of smaller roller. Fine pins located at a pitch of 0.4 mm on outer surface of both the rollers were produced during embossing. Using the above novel method of manufacturing process, embossing rollers of different patterns can be manufactured from different types of steel. The invention may be used to emboss and combine materials other than paper, or materials in which the plies are of different materials. The main advantages of the process of the present invention for the manufacture of embossing rollers and embossing rollers manufactured thereby, are: (i) The process can be used for the manufacture of metallic embossing rollers for embossing an array of small squares in X and Y directions, (ii) The process can be used for the manufacture of metallic embossing rollers for embossing different patterns. (iii)The process can be used for the manufacture of metallic embossing rollers for embossing on aluminum foil, paper or aluminized paper. (iv)The process can be used for the manufacture of metallic embossing rollers, which can produce a finish similar to knurling, (v) The embossing produced by the embossing roller helps to increase the stiffness of the paper/foil thereby helps packing materials in an automatic packing machine, (vi) Another advantage of embossing produced by embossing roller is aesthetic appearance. (vii)The profile turning on CNC machine is used to eliminate the rough grinding, (viii) Plasma nitriding process used in the present invention is eco- friendly and does not produce dimension distortion. We claim: 1. A process for the manufacture of embossing rollers, which comprises: a) turning of steel rod, b) drilling and tapping of rods, c) key way slotting and rough machining, d) toughening to 28-32 Hardness Rockwell Scale (HRC), e) grinding on the mandrel, f) outer profile turning, g) induction hardening to 40-45 HRC, to obtain roller(s)(l,2) ;characterized in that the said roller(s)(l,2) being subjected to: h) preliminary plasma nitriding being done at a maximum temperature of 1000°C by a plasma generator at s frequency of 2000 Hz and at a dwell time of 150 p second, i) optical profile grinding of circular and axial grooves, j ) key way finishing by spark erosion, k) overall length finishing by surface grinding, (1) running the rollers(l,2) with abrasive suspension, m) secondary plasma nitriding, n) deep cry0 treatment, o) physical vapor deposition (PVD) coating, p. inspecting for required profile of rollers(l,2) and q) assembling with appropriately machined shaft to obtain embossing roller(s). 2. A process as claimed in claim 1, wherein said steel rod used for manufacturing embossing rollers is such as EN 40B or of any other equivalent quality. 3. A process as claimed in claim1 2, wherein said abrasive suspension is prepared in water or oil containing suitable inhibitors for preventing erosion. 4. A process as claimed in claim 1 - 3, wherein said abrasive suspension contains elements of silicon carbide or aluminum oxide dissolved in water or oil. 5. A process as claimed in claim 1- 4, wherein said PVD coating material is selected from chromium nitride, titanium nitride or aluminum nitride. 6. A process as claimed in claim 1- 5, wherein said PVD coating is used with or without deep cry0 treatment. 7. A process as claimed in claiml- 6, wherein said pitch(P) of the pins of embossing roller(l,2) is in the range of 0.395 to 0.405 mm. 8. A process as claimed in claim1 -7, wherein included angle(8) between the pins of embossing roller(l,2) is between 58" and 102". 9. A process as claimed in claim 1 - 8, wherein said depth (D) of pins of embossing roller(l,2) is in the range of 0.140 to 0.200mm. 10. A process as claimed in claim 1- 9, wherein minimum crest radius(C) required for the formation of pins of embossing roller is 0.03 to 0.05mm. 11. Embossing rollers manufactured by the process for the manufacture of embossing rollers as claimed in claiml 10. 12. Embossing rollers as claimed in claim 11, wherein said diameter of top and bottom roller is equal or different. 13.Embossing rollers as claimed in claim 1 1- 12, wherein said diameter of top roller is of bigger size than the bottom roller.

Documents:

2159-del-2005-abstract.pdf

2159-DEL-2005-Claims-(08-02-2013).pdf

2159-del-2005-Claims-(14-01-2013).pdf

2159-del-2005-claims.pdf

2159-del-2005-Correspondence Others-(13-07-2012).pdf

2159-del-2005-Correspondence Others-(14-01-2013).pdf

2159-DEL-2005-Correspondence-Others-(08-02-2013).pdf

2159-del-2005-correspondence-others.pdf

2159-DEL-2005-Description (Complete)-(08-02-2013).pdf

2159-del-2005-description (complete).pdf

2159-del-2005-drawings.pdf

2159-del-2005-form-1.pdf

2159-DEL-2005-Form-13-(08-02-2013).pdf

2159-del-2005-form-18.pdf

2159-del-2005-form-2.pdf

2159-del-2005-Form-3-(13-07-2012).pdf

2159-del-2005-form-5.pdf