US3515798A - Elastic cover and removable cone assembly - Google Patents

Description

June 2, 1970 J. AJSIEVERT i 3,515,798

' ELASTIC COVER AND REMOVABLE CORE ASSEMBLY I Filed Dec. 6, 1968 I N VENTOR.

MAME; A. S/EVEPT BY M M {do /4M ATTORNE Y$ United States Patent 3,515,798 ELASTIC COVER AND REMOVABLE CONE ASSEMBLY James A. Sievert, Stillwater, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Dec. 6, 1968, Ser. No. 781,843

, Int. Cl. H01r 5/00 U.S. Cl. 174-135 6 Claims ABSTRACT OF THE DISCLOSURE An elastic tubular cover member supported in stretched condition on an easily removable one-piece rigid spiral core having interconnected adjacent coils. Uncoiling of the spiral and removal of the core as a continuous narrow strip through the remainder of the spiral permits the cover to be shrink fit upon a workpiece disposed within the assembly.

U.S. Pat. No. 743,346 wherein a soft rubber cover is formed on a metal sleeve which unites the wire-ends. Other forms have been described, e.g. in Dibner U.S. Pat. No. 2,674,647 and in Becker et al. U.S. Pat. No. 3,274,- 330. Heat-retractable normally non-elastic coverings have also been used, as in Foreit U.S. Pat. No. 2,695,853, although providing a less elfective cover because of their inability to retract at normal use temperatures after stretching. In a diflerent area, tough elastic rubbery rings or sleeves used as protectors for drill pipes have been supplied in expanded or stretched form on removable rigid sleeves, as shown for example in Gates U.S. Pat. No. 2,725,621 and Stone et al. U.S. Pat. No. 2,682,102.

Thepresent invention likewise provides a rubbery or elastically shrinkable tubular cover member supported in radially expanded or stretched condition on a removable rigid sleeve, but having a number of advantages. Removal of the sleeve in applying the cover is easily accomplished without the use of complicated or expensive presses or other machines and may be effected by simple hand operation. The supporting sleeve is easily and completely removable from any position and need not be removed at an end of the wire, tube, or other article onto which the rubbery cover is to be permitted to contract. No lubricants or friction-reducing materials are required to facilitate removal of the support.

These and other advantages are obtained, in accordance with the principles of the invention, by employing as the removable rigid supporting core a tubular member having a closed helix configuration as will now be further described in connection with the appended drawing. The single figure is an illustration in elavation and partly in section showing the application of a protective rubbery sleeve to a cable splice area.

The illustration shows two cable-ends 11 comprising a stranded conductor 12 and an insulating covering 13. The covering is cut away as at 14 and the conductors joined together in end-to-end configuration by suitable means not shown but which may typically consist of a com- Patented June 2, 1970 pressed or indented metal sleeve or a close-fitting metal tube with set-screws retainers. The joint or splic may be covered with insulating mastic or tape, here omitted for clarity of illustration.

The cover assembly is slipped over one of the wire-ends prior to joining the two ends. After the splice is completed, the assembly is slid into position over the splice area and the support is removed to permit the elastic cover to contract and form a tight fit. The process will be apparent from the illustration. The support comprises a unitary tubular shell 15 helically grooved along its entire length, the continuous groove 16 permitting the shell to be pulled out into a continuous strip 17 which is removed through the bore, i.e. from between the shell and the cable. An elastic tube 18 in radially extended or strtched condition is supported on the shell 15. As the strip 17 is progressively withdrawn, the tube contracts about the cable as at 19 to form a closely conforming and tightly retained protective covering. Contraction of the tube results in the application of a resultant force against the end of the shell and assists in the removal of the strip 17 as the shell is unwound.

In an illustrative embodiment a cylindrical tube of age-resistant translucent vulcanized rubber which in the relaxed state has an inside diameter of about 15 mm. and a'wall thickness of about 3 mm. is mounted on a rigid cylindrical tubular core of tough flexible cellulose acetate butyrate or polyvinyl chloride polymer material having an outside diameter of about 30 mm. and a wall thickness of about 2 mm. and spirally grooved in a narrow V-shaped groove approximately 1.5 mm. in depth and at a spacing of about 4 mm., the adjacent coils of the closed helix defined by the groove remaining interconnected. The assembly is slipped over a cable splice area having a diameter of about 20 mm. and the core is unwound and removed as a continuous narrow strip from between the core and the cable in the manner illustrated. Hand pulling provides fully adequate tension to unwind the core and remove the strip, leaving the rubber tube tightly aflixed to the cable. It will be appreciated that the polymeric tube in effect is substantially rigid and maintains its tubular shape, even though the material of which it is constructed is sufficiently tough and flexible to permit unwinding and removal of the helical strip under the tension supplied.

Synthetic rubbers and other elastic materials may be used in place of natural rubber, and the coverings may be suitably compounded or treated in any desired manner, for example by the incorporation of opacifying or toughening pigments such as carbon black or zinc oxide, antioxidants, vulcanizing agents, processing oils, and other well-known compounding agents, and by heatcuring or other treatments. Suitable identifying markings or legends may be applied. As a further specific illustration, conductive platelets may be incorporated, as taught in Wyatt U.S. Pat. No. 3,349,164, to provide an elastic insulative stress relief covering.

Although not essential to the application of the elastic covering, in some instances it may be found desirable to pre-coat the cable splice area, for example with a prim ing or water-proofing coating or a wrapping of adhesive tape. Alternatively, the inner surface of the elastic tube may itself carry a thin coating, for example of pressure-sensitive adhesive or of silicone gum for improving the bond or water-resistance between the tube and the cable. In such instances it may be found expedient to cover the external surface of the supporting shell, either before or after the forming of the helical groove, with a low adhesion backsize composition.

The elasticity of the rubbery tube not only retains the tube firmly on the core and assists in the unwinding and removal of the core, but additionally assists in holding the coils of the helix together, i.e. in the form of a closed helix, until they are forcefully removed by pulling on the extended end of the strip. Consequently the groove may be made as deep as desired for ease of separation of the coils, without fear of premature collapse of the structure.

Both the elastic sleeve and the rigid supporting core are ordinarily cylindrical both for ease of manufacture and as being of maximum utility, but tubular structures of non-uniform diameter are also contemplated as coming within the purview of the invention, a specific example being a conical structure for use as an end cap on a cable termination.

What is claimed is as follows:

1. An elastic cover assembly comprising an elastic cover member supported in highly stretched condition on a hollow core member comprising a continuous narrow strip of tough flexible material in the form of a substantially rigid closed helix having adjacent coils interconnected.

2. The assembly of claim 1 wherein said core member is a deeply spirally grooved polymeric tube, the groove being. sufficiently deep to permit separation of the interconnected adjacent coils defined thereby for removal as a continuous narrow strip remainder of said tube.

3. The assembly of claim 2 wherein said polymeric tube is of cellulose acetae butyrate or polyvinyl chloride and said groove extends through about three-fourths the wall thickness of said tube.

'4. The assembly of claim 1 wherein said cover member carries over its inner surface a thin water-resistant coating.

5. The assembly of claim 4 wherein said coating is a pressure-sensitive adhesive.

6. The assembly of claim 4 wherein said coating is a silicone.

extending through the References Cited I FOREIGN PATENTS 189,460 4/1957 Austria.

OTHER REFERENCES German printed application No. 1,053,602, Schwarzer, published Mar. 26, 1959.

LARAMIE E. ASKIN, Primary Examiner U.S. Cl. X.R.

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