WO2001021400A1

WO2001021400A1 - A system and method for producing flexible cable

Info

Publication number: WO2001021400A1
Application number: PCT/US2000/025448
Authority: WO
Inventors: Stanley J. Swider; Ritamarie G. Antoncic
Original assignee: Wall Industries, Inc.
Priority date: 1999-09-20
Filing date: 2000-09-18
Publication date: 2001-03-29
Also published as: AU7703500A

Abstract

A system and method for producing a flexible cable (29) having good dielectric properties includes the steps of passing load-bearing core yarns (20) through a latex bath (40), drying the core yarns (22) in an oven (50), forming the core yarns (22) into a core (24) of substantially parallel core yarns, wrapping a neoprene tape (80) around the core (24) to completely encapsulate the core (24), braiding an outer sheath over the neoprene encapsulated core, passing the cable (26) resulting from the previous steps through a latex bath (42), and curing the cable (28) in an oven (100). The process for manufacturing the cable also includes the step of applying electricity to the core before wrapping the core with neoprene tape (80) and detecting the amount of electricity that flows through the core as a measure of the core's dielectric properties. The neoprene tape (80) is provided with a color that contrasts with the color of the outer sheath so that the intermediate layer of neoprene tape (80) provides a visual indicator of wear through the outer sheath.

Description

A SYSTEM AND METHOD FOR PRODUCING FLEXIBLE CABLE

BACKGROUND OF THE INVENTION

Background of the Invention

The present application relates to a system and method for producing flexible textile cable having good dielectric properties.

In the manufacture of ropes and similar articles, it is well known that the use of twisted threads can have a number of disadvantages, such as a decrease in the tensile strength as a result of the stresses imposed on the threads. This has resulted in the development of ropes having a core of substantially parallel threads, and a protective tubular sheath that is preferably braided around the core. The conventional methods for producing these flexible cables with parallel core threads do not provide a means for ensuring that all moisture is removed from the core threads before the core threads are encased in a braided outer sheath. In many applications using these flexible cables it is also critical that some indication be provided when the outer sheath has been worn away, thus creating an unsafe condition. Existing cables do not provide any readily visible indication that the outer sheath has been worn away.

U.S. Patent No. 4,312,260 discloses a process of manufacturing a flexible cable wherein a plurality of substantially parallel textile threads have a binder applied thereto in a discontinuous manner before being bonded together to form a core about which a sheath is bonded by the binder. The binder can be deposited by bonding all the threads together at certain points and then leaving them free over a certain length, or, alternatively, the binder is deposited discontinuously on each thread but in such a way that an impregnated length on one thread corresponds to a non-impregnated length on the adjacent thread, with the possibility of overlapping zones if desired. This gives a cable in which regions resembling a hinged connection have been produced throughout the threads by virtue of bonding in zones. The cable is not provided with any means for ensuring that all moisture is removed from the central core threads before the outer braided cover is applied, and no readily visible indicators of wear through the outer braided cover are provided.

Another problem with conventional flexible cables is that if the core threads and the outer braided sheath are not sufficiently bonded together, the non-twisted core threads can easily fret when the sheath is worn. Proposed methods for correcting this problem include depositing a coating of thermoplastic resin on the core before applying an outer textile sheath. After drying the coating and applying the textile sheath, the textile sheath is rendered integral with the core by subjecting the whole assembly to traction under temperature conditions that assist the softening of the coating.

French patent No. 1,327,110 proposes a process for the manufacture of ropes, comprising essentially parallel core threads and an external tubular sheath. The core threads are simultaneously impregnated with a binder, the sheath then being applied while the binder is still in the adhesive state.

The binder used for impregnating the core threads can be of a very diverse nature, namely natural or synthetic elastomers, in the form of a latex or solution, vinyl polymers or other polymers, polycondensates, paraffins, waxes, metals with a low melting point etc.. Depending on the nature of the binder, the latter can be deposited as a solution or dispersion, in the liquid or viscous state.

SUMMARY OF THE INVENTION

The process of the present invention has been developed in order to provide a simple and inexpensive method to produce a flexible cable having good tensile strength, good dielectric properties, and an easily visible indication of wear. Load bearing core yarns are processed through a latex bath and dried in an oven to approximately 260 degrees Fahrenheit. When the drying process is completed the core yarns are subjected to 10 kilo volts of electricity to ensure that they are completely dry. Moisture detection is accomplished with an in line moisture monitor that shuts down the line if moisture is detected. Typically, the amount of moisture present in the core after undergoing the drying process can be detected as a function of the amount of electricity that will flow through the core when subjected to a known voltage.

The next step is stringing the core yarns through a reeve plate and a die, thereby forming a round firm core. The natural tack of the latex allows the yarns to bond together. After the forming of the core, an intermediate layer of uncured neoprene tape is wrapped around the core. The tape completely encapsulates the core, acting as a moisture barrier, not allowing any penetration of moisture into the central core. The uncured neoprene tape is preferably of a bright color that provides a clear contrast to an outer braided cover that is subsequently braided over the neoprene encapsulated core. The outside jacket is braided over the neoprene encapsulated core and the line is processed through another latex bath. The latex coats the outside of the braided cover, thus protecting the flexible cable from rough abrasive exteriors including surfaces or substances that come into contact with the cable. After processing the flexible cable through this final latex bath, the flexible cable is subjected to another heating application at 280 degrees Fahrenheit. This final curing temperature is sufficient to dry the outside braided cover, while at the same time internally curing the intermediate neoprene layer so that the neoprene layer bonds all of the components together to function as one unit. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates load bearing core yarns being processed through a latex bath.

Fig. 2 illustrates the core yarns being dried in an oven. Fig. 3 illustrates the core yarns being subjected to electricity in order to determine their moisture content.

Fig. 4 illustrates the core yarns being passed through a reeve plate (plate pierced with holes,) which places the core yarns relative to one another in the position that they are to occupy in the finished cable, and then through a die to form a round firm core.

Fig. 5 illustrates an uncured neoprene tape being wrapped around the central core.

Fig. 6 illustrates an outer jacket being braided over the neoprene encapsulated core. Fig. 7 illustrates the completed cable being processed through a latex bath.

Fig. 8 illustrates the completed cable being heated at a temperature sufficient to cure the intermediate neoprene layer and then wrapped on a spool for shipping.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to Fig. 1, load bearing core yarns 20 are passed over a series of tension rollers 32, 34, 36, and 38, in the direction indicated by arrow A, and processed through a latex bath 40, whereby each of the core yarns 20 is coated in a binder consisting of a rubber latex containing the catalysts and adjuvants customary in vulcanization. The latex used to coat the core yarns 20 is preferably a polychloroprene latex compound with additives and a solids content of approximately 25%, and a pH of approximately 11.0. An example of the preferred latex is sold under the trademark "UNTBOND" (product no. 9244HS) by Unichem Co. The core yarns are preferably 100% polyester, with each yam having a gauge selected from a range of 35,000 deniers - 108,000 deniers, depending on the desired finished diameter of the cable. The twist levels of the core yams are preferably selected from a range of 4.0 turns per foot - 8.0 turns per foot, again depending on the desired finished diameter of the cable. The roller tension applied by rollers 32, 34, 36, and 38 preferably ranges from 10 p.s.i. - 70 p.s.i.. As shown in Fig. 2, after being dried in an oven 50 at 260 degrees Fahrenheit, the latex coated core yams 22 are then passed in the direction indicated by the arrow A through a guide assembly 44. The drying process is intended to remove all moisture from the core yams so that the finished flexible cable will have good dielectric properties. When the drying process is completed, the core yarns are subjected to up to 30 kilovolts of electricity, and preferably approximately 10 kilo volts of electricity, as shown in Fig. 3, and the resulting current flow through the core yams is measured in order to ensure that the core yams are completely dry. An in line moisture monitor 60 shuts down the line if moisture is detected during this step. The next step, as shown in Fig. 4, is to string the core yams 22 through a reeve plate 70 or plate having holes pierced through it in an arrangement such that the core yarns are arranged in substantially parallel relationship with each other. The reeve plate has a circular pattern of preferably 127 holes, each having preferably a !/₂ inch diameter. Each core yam is passed through a separate hole in the reeve plate, with the exact pattern of holes being selected dependent upon the desired finished diameter of the core. The parallel core yams are then brought together through a die 72 in order to form a firm round core 24. The natural tack of the latex allows the core yams to bond together.

Referring next to Fig. 5, the latex impregnated core 24 is then directed to a workstation where uncured neoprene tape 80 is wrapped around the core. The uncured neoprene tape is made from a rubber compound mixture such as that designated by the product no. TN65061D and sold by Passaic Tape Co. The tape is preferably approximately 2.0 inches in width and .015 inch in thickness. The application of uncured neoprene tape to the core 24 can be easily and inexpensively achieved by providing an arm 74 rotatable about the core 24, with a roll of the neoprene tape 80 being eccentrically and rotatably mounted through an extension 76 to the arm 74 to orbit about the core 24 as the neoprene tape is applied in a spiral, overlapping intermediate layer to the core 24. The uncured neoprene tape is preferably of a bright red color or other color that will provide a clear contrast with an outer braided cover to be applied after the intermediate neoprene tape layer. The intermediate neoprene tape layer completely encapsulates the central core of substantially parallel core yarns, thus acting as a moisture barrier and preventing the penetration of any moisture into the central core.

As shown in Fig. 6, after the application of the intermediate neoprene tape layer 80, the cable is passed along the axis of a braiding machine 90 that includes multiple spindles 92 to braid a cover 26 continuously around the core 24 encapsulated in neoprene tape. Although 18 spindles are shown in Fig. 6, one of ordinary skill in the art will recognize that the number of spindles can be varied. The cover is composed of cover yam made preferably from 100% polyester and each having a gauge in the range from 4,000 denier - 60,000 denier, depending on the desired finished diameter of the cable and thickness of the protective outer cover. The twist levels of the cover yarns can preferably range from 10.0 turns per foot - 30.0 turns per foot. As shown in Fig. 7, the cable with braided outer cover 26 is then processed through another latex bath 42, which coats the outer braided cover to form the latex coated cable 28, with the outer layer of latex providing protection for the cable from rough abrasive exteriors including surfaces or substances that come into contact with the cable. The latex coating applied to the outer cover 26 is preferably a polychloroprene latex compound with additives, solids content of approximately 50%, and pH of approximately 12.0, such as the latex compound sold under the trademark "NULTEX" (product no. 3-G-3007 - Black #2) by General Latex Co. The outer braided cover 26 is preferably of a color that will contrast with the color of the intermediate neoprene tape layer 80 such that when the outer braided cover 26 wears away, the intermediate neoprene tape layer 80 will be readily visible as a wear indicator.

As shown in Fig. 8, after the final latex bath, the line 28 is subjected to another heating application by passing the line through a tunnel oven 100 at approximately 280 degrees Fahrenheit. During this final step, the latex coating the outer braided cover is dried and the intermediate neoprene tape layer is cured such that the neoprene tape bonds the central core yams to the outer braided cover.

The finished flexible cable 29 that results from the above system and process is ideal for applications where it is imperative to have good dielectric properties and where it is desired to provide the cable with a readily visible wear indicator.

Although specific compositions, sizes and other properties of the yams, intermediate layer of neoprene tape and latex compounds have been specified above in the interest of describing a preferred embodiment and best mode of practicing the invention, one of ordinary skill in the art will recognize that the invention is not limited to the disclosed embodiments and encompasses all cable and processes for producing cable that fall within the spirit and scope of the following claims.

Claims

WHAT IS CLAIMED IS: 1. A process for producing a cable, comprising the steps of: passing a plurality of core yams through a latex bath; drying the core yams in an oven; forming the core yams into a core of substantially parallel core yams; wrapping a neoprene tape around the core to completely encapsulate the core; braiding an outer sheath over the neoprene encapsulated core; passing the cable resulting from the previous steps through a latex bath; and curing the cable in an oven.

2. The process of claim 1 , further including a step of applying electricity to the core before wrapping the core with neoprene tape and detecting the amount of electricity that flows through the core as a measure of the core's dielectric properties.

3. The process of claim 2, wherein the neoprene tape is an uncured neoprene tape.

4. The process of claim 3, wherein the neoprene tape wrapped around the core is

of a color that contrasts with a color of the outer sheath so that the neoprene tape

provides a clear visual indicator when the outer sheath is worn through.

5. The process of claim 1 , wherein the core yarns are dried in the oven at

approximately 260 degrees Fahrenheit.

6. The process of claim 5, wherein the cable is cured as a final step in the oven at

approximately 280 degrees Fahrenheit.

7. A cable produced by the process of claim 1 , wherein the neoprene tape

wrapped around the central core is of a color that contrasts with a color of the outer

sheath.

8. The cable of claim 7, wherein the neoprene tape is red and the outer sheath is

black.