|Title of Invention
A PROCESS FOR NORMAL CURE COMPOSITE SEAL FOR CABLE JOINTS
|ABSTRACT A process for sealing the cable wire joints with the Normal cure composite tape seal (NCCS) enclosure, which comprises, Poly sulphide paste (edge sealing). Enclosures of elastomer, composite prepreg tape & insulation tape, along with end clips, effectively seals the cable joints at normal temperature is described. The ambient cure, easily sealable and re-openable / reworkable, anti corrosive, anti termites and cost effective, sealing technique fulfills all the requirements for cable joint protection, particularly for underground cable joints, from water seepage, termite and rats attack, thermal and mechanical impacts.
|The present invention relates to a process for normal cure composite tape seal for cable joints. The main usages of the invention are to seal the cable joints such as communications cables in order to make the joint, high strength, leak proof, anti termite, anti corrosive, flexible, and flame retardant.
Reference may be made from U.S. patent number 5,301,422, dated 12-4-1994, wherein the device comprises a pair of semi-cylinderical shell pieces which, when assembled together, form a modified cylindrical structure having a central aperature for receiving the ferrules. The drawbacks of this system are the complicated rigid structure which may be damaged on the application of high mechanical loads or impacts. Further it may undergo corrosion underground. It needs skilled labour to fabricate the seal and may not be cost effective method.
Reference may be made from U.S. patent number 5,952,612, dated Sep. 14,1999, wherein a two part range-taking member for providing a seal around a substrate includes a mating pair of resilient components for enclosing the substrate and a co-operating pair of rigid components for urging the resilient components into conformity with the substrate. The member may provide an electrical stress cone for a power cable, for example with two such members being provided in a cable joint. In this method, the filling compound is added to fill the gap in the joint and the outer metal shells.
The outer metal shell is of rigid in nature and may undergo failures when it comes in contact with high mechanical toads or impact. The sealing system may not be very tight, which is required to prevent water seepage under ground. Further, it may be more prone to corrosion under ground. It needs skilled labour to fabricate the seal and not cost effective method. Further this patent pertains to electrical cable joints. But in our invention the above drawbacks are rectified.
Reference may be made from U.S. patent number 6,064,002, dated May 16, 2000 , where in an electrically insulated cable having a sheath made of a material which is heat-fusible to a polyamide or polyester resin so that a highly waterproof joint portion can be formed between the cable and a housing simultaneously when the housing is injection-molded from a crosslinked resin composition comprising a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer mixed together in a weight ratio of 80:20 to 20:80. A housing is provided around one end of the sheath of this cable by injection-molding polyamide or polyester engineering plastics to fuse the sheath to the housing, thereby hermetically sealing the interface between the cable and the housing. The sheath may be made from a crosslinked resin composition comprising a thermoplastic polyurethane elastomer and a thermoplastic polyamide elastomer mixed together in a weight of 80:20 to 10:90. It is possible to seat the cable to a housing made of polyamide engineering plastics.
The drawbacks of this method are the technique of themnal curing of resin, which may damage the cable wires at high temperatures. This technique needs heating source and skilled labours for fabrication. During the fabrication, materials may be overheated and wasted. Hence the method is not cost effective. Further, re¬opening the joints may be very difficult, because the cured materials formed are highly crosslinked and rigid. In our system, all these drawbacks are rectified.
Existing system of TSF(Thermoshrink) -kit enclosure for cable joints exhibited in fig-1 describes gell filled thermoshrink closure type joints. This type of sealing is used currently by most of the Telecommunication departments. In this system the cable joint (1) is filled with petroleum jelly (2) and enclosed by polyethylene sleeves. Then the joint is insulated with tapes (4). In the next step the aluminium canister (6) over the splice bundle was fixed. Then degreasing the cables with cleaning tissue for a distance of 200mm from the ends of the splices was carried out and that followed by abrading the cable circumferentiatly over the degreased length and cleaning with dry cloth. Finally the heat shrink sleeve over the canister was fixed and marked the sleeve ends on the cables. Subsequently the second mark approx.20mm towards the splice was made. Then the cable areas between arrows were heated by means of blow lamps for ten to fifteen seconds. After removing release film the heat shrinkable sleeve (7) was heated until the thermochromic paint changes its colour from green to black. The stainless steel channels and retaining clips were also fixed.
The drawbacks in this system are,
I. While heating the thermoshrink sleeve, the temperature produced
becomes sufficient enough to damage the interior wire joints. II. For heating, blow tamps and other accessories are to be used.
III. The rigid joint formed may be easily damaged, when high mechanical strength or impact is applied.
IV. The joints cannot be bended or twisted.
V. Re-opening of joint is a tedious procedure and may incur in more damages and waste of materials.
VI. The size of the fabricated joint becomes three to four times bigger than the cable size.
VII. Get filling and cleaning steps poses laborious problems and not cost
VIII. Because of the presence of gel, termites and ants can easily enter into
the joint and pave a way for water seepage.
tX. Use of aluminium metaf canister leaves behind empty space between the wire joints and outer surface. This results in the crumbling of joints when it receives high impact.
X. Skilled labour is essential to fabricate the joint. Hence the higher labour cost becomes inevitable.
XI. The working period for fabrication Is about three to five hours
XII. It is highly impractical to seal the joint during rainy seasons.
XIII. Wastage of materials.
XIV. High cost product
XV. External surface of the seal joint contains stainless steel channel, which undergoes corrosion under ground.
The above draw backs were eliminated by our newly invented system called Normal cure composite tape seal represented in figure. 2., which, explains the effective method of sealing the cable joint for leak proof, where in it is comprising the enclosing of the wire joints by an insulation tape (1), and sealing the edges with polysulphide paste(11). The said joint is enclosed by covering with polyester film (2). Then the two sides of the cable surface is cleaned and activated by etching with xylene solvent. Now end seals (8&9) are made around the cable surface by using polysulphide paste(11). The entire seat is enclosed by winding with elastomer tape. Poly gel coated on the entire surface. It Is covered by winding a composite NCCS prepreg tape (3) comprising of glass fibre (12) impregnated with polysulphide paste (11) backed with polyethylene peel off film (13 &14). The said assembly covered by winding with elastomer tape (4) followed by insulating tape (5). Finally the two terminal ends are tightened by nylon grip clips (10). Finally Fibre reinforced Shell (6) can be fixed, (optional)
During curing, the sandwich of elasotmer-polygel-NCCS tape-elastomer are formed as a flexible skin. This flexible skin, not only arrests the seepage of water and also imparts high tensile and impact strength to the joint. It protects the joint from deformation while bending or twisting and also prevents electromagnetic interference. Finally the two ends of the sealing joints were clamped (10) tightly by means of nylon tags, which ensures the complete protection of the joint.
Fig-(3) represents flexible composite prepreg tape in which part (11 &13) represents the polysulphide paste. Part (12) represents glass fibre cloth impregnated with polysulphide paste and part (14) is the polyester back up film.
The main objective of the present invention is to provide a cable joint kit which obviates all the drawbacks of the prior art mentioned above.
Another objective of the present invention is to provide a composite cable jointing kit which works at room temperature.
Yet another objective of the present invention is to provide a cost effective cable jointing kit.
Accordingly the present invention provides a process for normal cure composite tape seal for cable joints which comprises :
1. A process for enclosing the cable joints by using Normal (Ambient) cure
composite tape seal (NCCS) which comprising, enclosing the wire joints by an
insulation tape (1), and sealing the edges with polysutphide paste(11). The said
joint is enclosed by covering with polyester film (2). Then the two sides of the
cable surface is cleaned and activated by etching with xylene solvent. Now end
seals (8&9) are made around the cable surface by using potysutphide paste(11).
The entire seat is enclosed by winding with elastomer tape, Poly gel coated on
the entire surface. It is covered by winding a composite NCCS prepreg tape (3)
comprising of glass fibre (12) impregnated with potysutphide paste (11) bactced
with polyethylene peel off film (13 &14). The said assembly covered by winding
with elastomer tape (4) followed by insulating tape (5). Finally the two terminal
ends are tightened by nylon grip clips (10). Finally Fibre reinforced Shell (6) can
be fixed, (optional)
In an embodiment of present invention the composite prepreg tape (3 in fig-2) is made out of potysutphide paste(ll) containing 30 - 50 parts of potysutphide resin comprising 5-10 parts of fused silica, 10-15 parts of talc, with xylene solvent, 5-10 parts of catalyst such as lead oxide containing red oxide as pigment with glass fibre reinforcement.
In another embodiment of present invention , the said potysulphide paste (11) is mixed with 5-10 parts of xylene solvent to get the poly gel of desired consistency and that can be coated above elastomer tape.
In still another embodiment of the present invention , the two ends of the cable joints are sealed by end seals made of potysulphide paste(11), which prevents capillary infiltration of water / moisture / termites entering through the ends.
In another embodiment of the present invention, the said cable joint is enclosed externally by Fibre reinforced plastic shells (6). Hence no corrosion occurs under ground.
In further embodiment of the present invention, the said joint is sealed at normal temperature without applying external heating or external pressure.
Under ground telephone cable ioints are more easily attacked by temnites , water seepage and mechanical damages. Currently used sealing kit system fails to meet the above reguirements. In order to tackle these problems, the improved sealing process technigue was invented.
The concept of the invented sealing system is nomnal cure with no heating, leak proof, anti termite, flame retardant, flexible, easily processable with inland materials and cost effective.
In the present method of sealing the cable joints, in order to make the joint anti termite, water resistant and leak proof, polysulphide mix. is used. In order to resist crack formation at the joints, while bending or twisting and to make flexible seal the composite prepreg tape (NCCS) is made with polysulphide impregnated glass cloth. Edge seals with polysulphide paste, are used to prevent capillary infiltration of water/moisture into the joint. The joint is made tight and leak proof by winding with various component tapes.
Normal cure composite sleeve is simpler, cheaper and superior than the existing thermocure sleeve system used currently. By this system, after installation, curing continues and completes within 24 hours of time during which more tightness, strength and elasticity are imparted. The other important feature of novelty in the present invention is that the joint after curing works like a tight and flexible joint which prevents cracking that occurs in a rigid joint currently used. Cable jointing system results in flexible and easily reopenable / reworkable properties.
Cable joint is sealed with newly invented composite (NCCS) prepreg tape by winding technique, which imparts not only tightness , strength and shape to the seal at the joint and also works as an effective water/moisture barrier. Without gel filling, the cable joint is ensured for complete protection from water / moisture entry, which helps in reducing the cost, easier reopening/reworking at the joints, time and labour. The technique of edge sealing (ref. fig -2 ) ensures the complete leak proof system at the joint. The technique of end sealing (ref.fig-2 ) at the surface of the cable and sealing with sealant prevents the capillary infiltration of water or moisture to the joint through the surface of cable. It also increases the grip and tightness at the sealing area. Size of the joint is kept small ( 14 mm more than the actual cable) and flexible. End clipping (see fig -2) technique adopted, gives not only additional protection to the joint from water seepage and also makes easy removal or reopening of joints.
Preparation of composite prepreg tape (NCCS) includes the following:
With reference to fig-3, wherein the polysulphide paste (11) comprising polysulphide resin to the extent of 30 - 50 parts and comprising silica (fused)about 05-10 parts and talc of about 10-15 parts mixed with red oxide powder of about 05-10 parts and the catalyst (lead oxide) to the extent of 05 -10 parts and the paste is prepared using xylene solvent.
Example -1 Tightness test (leak proof test) was conducted for five pair cable straight joints as per the standard. (Telecom.standard : Generic Requirements No GR/CJM-01/02 June 1999. N0.6.3/p-08 : (6.3. - The tightness of installed closure shall be checked by pressurizing to 700 milli bars for a period of 15 minutes while immersed in water such that they are at least 5 cm below the water surface, at room temperature. A sample shad be considered tight if there is no continuous stream of air bubbles escaping from it)
The sample for the test is prepared by connecting with wires of two five pair (copper core) communication cable and enclosing the jointed wires with our system (Normal cure composite seal enclosure). Further, one end of the cable is sealed and the other end is fitted with valve, through which the compressed air was pumped.
The enclosure fixed part of the cable joint is immersed under water (5cm below the water level) and the compressed air was pumped through the valve inside the cable joints. No air bubbles were observed during the test.
The enclosure withstood to the internal pressure of 0.7 kgf / cm' for more than one hour, (as per the standard, the value should be around 15 minutes). Further test was conducted at increased pressures and the joint withstood even at 30.0 kgf/cm " for more than 15 minutes.
Vibration test was conducted for five pair cable joints (straight) as per Telecom, standard specifications (Generic Requirements No GR/CJM-01/02 June 1999. N0.6.4./p-08) . The sample specimen of 05 pair cable wire joints enclosed was mounted on a vibration apparatus with the cables rigidly clamped at distances of 10 cm from each end of the sleeve. The center point of the enclosure was subjected to a sinusoidal vibration with a frequency of 100 vibrations per minute and amplitude of 10 mm for a period of two hours, followed by tightness test and no leak was observed. Further 200 vibration /min. for two hours and for three hours and four hours were conducted. No leak was observed.
Bending test was conducted as per the standards, (Generic Requirements No GR/CJM-01/02 June 1999. N0.6.8./p-09) for five pair cable joints. The specimen was clamped on a smooth, flat, horizontal surface. A bending force of maximum 500 N was applied at a distance of 10cm from sleeve edge on each extending cable to deflect the cable to maximum angle of 45 " at the point of application of the force.
A bending cycle consisting of one excursion of bending to 45 " from the neutral position and maintained for five minutes , back to the neutral and bent In the opposite direction and maintained for five minutes and then returned to the neutral position. After completion of two cycles, the tightness test was conducted. There was no leak.
Example -4 Temperature cycling test was conducted as per the standard (Generic Requirements No GR/CJM-01/02 June 1999.N0.6.10./p-10), by placing the five pair cable joint in a water bath, five cm below the surface of water and subjected to thirty cycles. Each cycle was conducted for 12 hrs. at the temperature range of 65 "C. After completion of every ten cycles, the joint was subjected to tightness test. There was no leak.
Example - 5
Thermal shock test was conducted (Generic Requirements No GR/CJM-01/02 June 1999. N0.6.11./P-10) by immersing the sealed cable joint in water bath five cm. below the water surface at 65"c. After fifteen minutes the sample was suddenly transferred to ice water (3.0 "C) for five minutes. At the end of five minutes the sample was again transferred to hot water back. After completing ten cycles, sample was subjected to tightness test. There was no leak.
Example - 6 Corrosion test was conducted as per the standard (Generic Requirements No GR/CJM-01/02 June 1999. N0.6.12./p-10), by immersing the cable joint In solution of PH value 4.0 and 10.0 for thirty days. After completion of the period, the sample was inspected visually and there was no corrosion and then subjected to tightness test as described earlier. There was no leak.
Conclusions of experiments :
The above experiments clearly indicate that the invented normal cure composite tape seal (NCCS) is a suitable enclosure product for sealing the cable joints of Telecom. It has several advantages over the existing systems, and the method Is highly cost effective. Further the NCCS prepreg tape enclosure, ensures the total prevention of water seepage inside the joints.
Further the elastomer tape (4) winding ensures tightness and leak proof at the joint. This gets tightened further over a period of time. Inorder to impart total protection to the joint, insulation tape (5) was wound finally. The two ends of the seal tightened by means of clips (10).
Advantages of the present invention :
1. Perfect water / moisture sealing effects / leak proof.
2. Cold cure system. Hence there is no use of blow lamp or torch to cure the
3. High tightness and impact strength and that increases over a period of
4. Time during curing process.
5. Less weight / volume.
6. After the sealing work the thickness of the cable at the joint .becomes 28 mm for 14 mm diameter 5- pair cable.
7. Low cost ie half the cost of existing jointing kits .
8. Easy processing, less time for sealing / fabrication (30 mts).
9. Easy reopening without damaging the wires.
10. No wastages and no disposable problems.
11. Non toxic materials and no health hazards and environment friendly.
12. All the raw materials used are made in India. No imported materials are used.
13. withstand at the temperature range of -30 "c to +100 X
14. No shrinkage or expansion after complete cure.
15. Processed at any climate and weather conditions.
16. Flexible and bends without any damage at the joints.
17. Elasticity and tightness are imparted during cure .
18. Curing takes place within 24 hrs.
19. Life time to the product will be more than ten years.
20. Minimum man power and no special skill is required for installation which reduces the labour cost.
21. No corrosion at the joints
22. Aesthetic look.
1. A process for enclosing the cable joints by using Normal (Ambient) cure composite tape seal (NCCS) which comprising
a. enclosing the wire joints by an insulation tape (1)
b. sealing the edges with polysulphide paste(11).
c. enclosing the joint by covering with polyester film (2)
d. cleaning and activating the cable surfaces by xylene solvent.
e. Making end seals (8&9) around the cable surface by using polysulphide
f. Enclosing the entire seal by winding with elastomer tape
g. Coating the surface by poly gel
h. Covering the seal by winding with composite NCCS prepreg tape(3)
i. Covering the seal by winding with elastomer tape (4)
j. Winding with insulation tape(5)
k. Tightening the two terminal ends by using nylon clips
I. Fixing fibre reinforced shell(6) finally.
2. A process for sealing the cable wire joints with the Normal cure composite tape seal (NCCS) enclosure, at ambient temperature, as claimed in claim 1, in which the composite prepreg tape (3) is made out of polysulphide paste comprising 30 - 50 parts of polysulphide resin and 5-10 parts of fused silica, 10-15 parts of talc, with xylene solvent, 5-10 parts of catalyst such as lead oxide and red oxide (Iron oxide) with glass fibre reinforcement.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|RASHTREEYA SIKSHANA SAMITHI TRUST
|II BLOCK, JAYANAGAR, BANGALORE-560 011, KARNATAKA.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date