Constant length composite glass fiber cable under varying temperature conditions

Abstract

A composite glass fiber cable is disclosed having a negative linear coefficient of thermal expansion which is controllable by variation of the .Iadd.helical angle or angles of .Iaddend.twist of helically plied glass roving to substantially zero change in length over a wide variation in environmental temperatures under varying load conditions. .Iadd.It is possible, by controlling the helical angle and maintaining it constant from the cable center to outer surface, to control thermal elongation effects on the cable to obtain either expanding, contracting or constant length cables over a wide temperature range. .Iaddend.

The embodiments of the invention in which a particular property or privilege is claimed are defined as follows: 
     
       1. A composite cable structure composed of multiple layers of helically wound glass fiber rovings with each of the glass .[.fibers.]. .Iadd.filaments .Iaddend.making up each roving completely surrounded by a cured elastomeric sheath bonded to the elastomeric sheaths surrounding adjacent filaments of both the same and adjacent rovings, each layer of roving having the same helical angle as the initial and adjacent layers of roving, the helical angle selected to produce a cable of controlled elongation over a wide temperature range under varying tensile loads. 
     
     
       2. .[.A.]. .Iadd.The composite .Iaddend.cable structure of claim 1 wherein the helical angle is no greater than about 12°. 
     
     
       3. The composite cable structure of claim 1 wherein the helical angle ranges from about 5 to 9°. 
     
     
       4. The composite cable of claim 1 wherein the elastomer is a urethane elastomer. 
     
     
       5. A composite cable structure composed of multiple layers of helically wound glass fiber rovings with each of the glass .[.fibers.]. .Iadd.filaments .Iaddend.making up each roving completely surrounded by .Iadd.a .Iaddend.cured elastomeric sheath bonded to the elastomeric sheaths surrounding adjacent filaments of both the same and adjacent rovings, each layer of roving having the same helical angle as the initial and adjacent layers of roving, the helical angle being no greater than about 12°, such that the composite cable maintains an essentially constant length under widely varying temperature conditions. 
     
     
       6. A method of making a composite cable structure composed of multiple layers of helically wound glass fiber rovings with each of the glass .[.fibers.]. .Iadd.filaments .Iaddend.making up each roving completely surrounded by a cured elastomeric sheath, the composite cable capable of maintaining substantially constant length under varying temperature conditions, comprising: twisting a plurality of glass fiber rovings, the glass .[.fibers.]. .Iadd.filaments .Iaddend.of which are individually coated with an uncured elastomeric resin incorporating a curing agent or hardener therein to form an initial lay-up,   twisting further layers of glass fiber rovings, the glass .[.fibers.]. .Iadd.filaments .Iaddend.of which are coated with an uncured elastomeric resin, around the initial lay-up in the same direction until a cable of desired cross-sectional diameter is obtained, and   maintaining the helical angle of the initial and subsequent rovings during lay-up constant and no greater than about 12°.   
     
     
       7. The method of claim 6 wherein the helical angle is maintained between about 5° to 9°. 
     
     
       8. The method of claim 6 wherein the elastomer is a urethane elastomer. .Iadd. 9. The composite cable of claim 1 wherein the helical angle is selected so as to control the elongation to maintain essentially constant cable length. .Iaddend..Iadd. 10. a method of making a composite cable of glass fiber rovings comprising the steps of: helically winding a plurality of glass fiber rovings to form successive layers of increasing diameter;   surrounding the filaments of each of said rovings with an uncured elastomeric resin having a curing agent or hardener in contact therewith to form an elastomeric cable matrix; and   maintaining the helical angle of the initial and subsequent layers during a lay-up at a constant value selected to control thermal elongation effects on the cable. .Iaddend..Iadd. 11. The method of claim 10 wherein the thermal elongation effects on the cable are controlled such that the cable maintains essentially constant length under widely varying temperature conditions. .Iaddend..Iadd. 12. A composite cable in which thermal elongation effects are controlled under widely varying temperature conditions, the cable being fabricated by the process of helically winding a plurality of glass fiber rovings to form successive layers of increasing diameter, surrounding the filaments of each of said rovings with an uncured elastomeric resin having a curing agent or hardener in contact therewith to form a cable matrix, and maintaining the helical angle of the initial and subsequent layers during lay-up at a constant value selected to control thermal elongation effects on the cable. .Iaddend..Iadd. 13. The composite cable of claim 12 wherein the thermal elongation effects on the cable are controlled such that the cable maintains an essentially constant length under widely varying temperature conditions.