US3849192A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of applying and cooling low density polyethylene cable insulation
Assignee: GEN CABLE CORP Inc
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Filing: 1972-05-12
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Granted: 1974-11-19
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Expires: 1992-05-12
Abstract
Abstract This method of applying polyethylene insulation to an electric cable and cooling the polyethylene maintains the thermal stresses in the cooling polyethylene within sufficiently narrow limits so that shrinkage of thick walls of polyethylene insulation do not cause voids in the insulation, and particularly along the inner surfaces of the insulation. The insulation is extruded over a conductor and the insulation then passes through a plurality of cooling baths where the temperature and rate of cooling are controled in such a way as to avoid the setting up of thermal stresses sufficient to cause the formation of voids. The method is suitable for general application and is not tailor made to suit a particular size of wire having a particular thickness of insulation.
Inventors
- 👤 G Schmidt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:55
CPC Classifications
B; B05; B05D; B05D7/00; B05D7/20; B29; B29C; B29C48/00; B29C48/03; B29C48/05; B29C48/06; B29C48/25; B29C48/88; B29C48/911; B29C48/918; B29C48/9185; B29C48/919
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
312 words
THE METHOD OF APPLYING AND SHRINKING POLYETHYLENE INSULATION OVER METAL CONDUCTORS OF ELECTRIC CABLES HAVING INSULATION OF A RADICAL THICKNESS OF SUBSTANTIALLY 0.345 INCH AND HAVING A MAXIUM SHRINKAGE WITHIN A CRITICAL RANGE FROM ABOUT 120*C TO ABOUT 100*C AND A RATIO OF OUTSIDE DIAMETER TO INSIDE DIAMETER GREATER THAN ABOUT 1.3:1 WHICH METHOD COMPRISES: A. EXTRUDING THE POLYETHYLENE OVER A CONDUCTOR WITH THE POLYETHYLENE AT A TEMPERATURE SUBSTANTIALLY HIGHER THAN THE MELTING POINT OF THE POLYETHYLENE, B. ADVANCING THE CABLE FROM THE REGION OF EXTRUCTION AND ALONG THE MELTING POINT OF THE POLYETHYLENE, ZONE, THE TEMPERATURE OF THE POLYETHYLENE BEING SUBSTANTIALLY HIGHER THAN 120*C. C. MAINTAINING THE TEMPERATURE OF THE OUTSIDE OF THE INSULATION IN THE FIRST COOLING ZONE AT LEAST AS HIGH AS APPROXIMATELY THE MELTING POINT OF THE POLYETHYLENE, D. CONTINUING THE IMMERSION OF THE CABLE IN THE FIRST ZONE WITH THE HEAT ABSORBING CAPACITY OF THE CONDUCTOR AND THE TEMPERATURE OF THE ZONE SUFFICIENT TO COOL THE INSULATION AT THE OUTLET END OF THE FIRST ZONE TO A RADIAL TEMPERATURE GREATER WITHIN ABOUT 20 PERCENT OF THE TEMPERATURE OF THE OUTSIDE OF THE INSULATION, C. ADVANCING THE CABLE FROM THE FIRST ZONE INTO A SECOND ZONE, F. MAINTAINING THE TEMPERATURE OF THE SECOND ZONE AND THE TIME OF IMMERSION OF THE CABLE IN THE SECOND ZONE TO COOL THE OUTSIDE OF THE INSULATION BELOW 100*C, THE LOWER LIMIT OF MAXIMUM SHRINKAGE OF THE POLYETHYLENE, WHILE MAINTAINING THE RADICAL TEMPERATURE GRADIENT IN THE POLYETHYLENE WITHIN A RANGE OF ABOUT 30 PERCENT OF THE HIGHEST TEMPERATURE WITHIN THE RADIAL EXTENT OF THE INSULATION AT EVERY INSTANT DURING THE COOLING IN THE SECOND ZONE, AND G. MAINTAINING THE RADIAL TEMPERATURE GRADIENT WITHIN SAID 30 PERCENT RANGE UNTIL ALL OF THE POLYETHYLENE HAS COOLED BELOW THE 100*C SO AS TO DISTRIBUTE SHRINKAGE STRESSES MORE UNIFORMLY THROUGH THE RADICAL THICKNESS OF THE INSULATION.
Claim 2
Independent Claim
312 words
THE METHOD OF APPLYING AND SHRINKING POLYETHYLENE INSULATION OVER METAL CONDUCTORS OF ELECTRIC CABLES HAVING INSULATION OF A RADICAL THICKNESS OF SUBSTANTIALLY 0.345 INCH AND HAVING A MAXIUM SHRINKAGE WITHIN A CRITICAL RANGE FROM ABOUT 120*C TO ABOUT 100*C AND A RATIO OF OUTSIDE DIAMETER TO INSIDE DIAMETER GREATER THAN ABOUT 1.3:1 WHICH METHOD COMPRISES: A. EXTRUDING THE POLYETHYLENE OVER A CONDUCTOR WITH THE POLYETHYLENE AT A TEMPERATURE SUBSTANTIALLY HIGHER THAN THE MELTING POINT OF THE POLYETHYLENE, B. ADVANCING THE CABLE FROM THE REGION OF EXTRUCTION AND ALONG THE MELTING POINT OF THE POLYETHYLENE, ZONE, THE TEMPERATURE OF THE POLYETHYLENE BEING SUBSTANTIALLY HIGHER THAN 120*C. C. MAINTAINING THE TEMPERATURE OF THE OUTSIDE OF THE INSULATION IN THE FIRST COOLING ZONE AT LEAST AS HIGH AS APPROXIMATELY THE MELTING POINT OF THE POLYETHYLENE, D. CONTINUING THE IMMERSION OF THE CABLE IN THE FIRST ZONE WITH THE HEAT ABSORBING CAPACITY OF THE CONDUCTOR AND THE TEMPERATURE OF THE ZONE SUFFICIENT TO COOL THE INSULATION AT THE OUTLET END OF THE FIRST ZONE TO A RADIAL TEMPERATURE GREATER WITHIN ABOUT 20 PERCENT OF THE TEMPERATURE OF THE OUTSIDE OF THE INSULATION, C. ADVANCING THE CABLE FROM THE FIRST ZONE INTO A SECOND ZONE, F. MAINTAINING THE TEMPERATURE OF THE SECOND ZONE AND THE TIME OF IMMERSION OF THE CABLE IN THE SECOND ZONE TO COOL THE OUTSIDE OF THE INSULATION BELOW 100*C, THE LOWER LIMIT OF MAXIMUM SHRINKAGE OF THE POLYETHYLENE, WHILE MAINTAINING THE RADICAL TEMPERATURE GRADIENT IN THE POLYETHYLENE WITHIN A RANGE OF ABOUT 30 PERCENT OF THE HIGHEST TEMPERATURE WITHIN THE RADIAL EXTENT OF THE INSULATION AT EVERY INSTANT DURING THE COOLING IN THE SECOND ZONE, AND G. MAINTAINING THE RADIAL TEMPERATURE GRADIENT WITHIN SAID 30 PERCENT RANGE UNTIL ALL OF THE POLYETHYLENE HAS COOLED BELOW THE 100*C SO AS TO DISTRIBUTE SHRINKAGE STRESSES MORE UNIFORMLY THROUGH THE RADICAL THICKNESS OF THE INSULATION.
Claim 3
Dependent Claim
18 words
The method described in claim 1 comprising maintaining the first zone at a temperature of approximately 115* C.
Claim 4
Dependent Claim
48 words
The method described in claim 2 wherein the first zone consists of a liquid bath compatible with low density polyethylene and said liquid has a boiling point substantially in excess of 115* C, and the cable is cooled on its way from the extruder to the first zone.
Claim 5
Dependent Claim
41 words
The method described in claim 2 wherein the second zone comprises a liquid bath having a temperature of approximately 92* C at the entrance to the bath and a temperature of approximately 86* C at the discharge end of the bath.
Claim 6
Dependent Claim
32 words
The method described in claim 1 wherein the final cooling of the insulation is performed in a third zone comprising a bath with liquid at a substantially lower temperature than 86* C.
Claim 7
Dependent Claim
89 words
The method described in claim 5 wherein the first zone comprises a bath at a temperature of approximately 115* C, the second zone comprises a bath at a temperature of approximately 92* C at its entrance end and at a temperature of approximately 86* C at its discharge end, and the third bath having a temperature of approximately 88* C at its entrance end and a temperature of approximately 70* C at its discharge end, and moving the cable along a horizontal path in the second and third baths.
Claim 8
Dependent Claim
72 words
The method described in claim 1 wherein the temperature gradient in the insulation in the first zone is within about 10 percent of the temperature of the outside surface of the insulation, and maintaining the temperature gradient in the insulation in the second zone within a range of about 20 percent of the highest temperature within the radial extent of the insulation at every instant during the cooling in the second zone.
Claim 9
Dependent Claim
219 words
The method described in claim 1 comprising immersing the cable in a liquid bath in the first zone, with the liquid at a temperature of about 115* C, for at least about 7 minutes, said first zone bath being a liquid that is compatible with said polyethylene and that does not promote stress cracking of the polyethylene at temperatures of the order of 115* C, and then passing the cable through liquid in a second bath in the second zone, and in which the liquid at the entrance end of the bath is at a temperature of about 92* C and decreases to a temperature of about 86* C at the exit end of the second zone, each portion of the cable being in said second bath for at least about 5 minutes, and immediately after the cable emerges from the second bath, passing the cable through a third liquid bath in a third zone and in which the temperature of the liquid is about 88* C at the entrance end of the third liquid bath and about 82* C at the middle zone of said third liquid bath and is about 70* C at the discharge end of said third bath, each portion of the cable being in said third liquid bath for at least about 9 minutes.
Claim 10
Dependent Claim
19 words
The method described in claim 1 comprising cooling the insulation in the first zone by contact with ethylene glycol.
Claim 11
Dependent Claim
40 words
The method described in claim 1 comprising extruding on the conductor polyethylene insulation in heat-exchanging contact with the conductoR and with a ratio of the outside diameter of insulation to the inside diameter of the insulation of at least 3:1.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |