US3911203A

US3911203A - Cable boot

Info

Publication number: US3911203A
Application number: US449089A
Authority: US
Inventors: Michael P Goldowsky
Original assignee: Kings Electronics Co Inc
Current assignee: Kings Electronics Co Inc
Priority date: 1974-03-07
Filing date: 1974-03-07
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07

Abstract

A cable boot for protecting cables in which a resilient material is provided with a first bore extending partially through said material and a second bore of lesser diameter than the first bore extending the remaining distance through said material, the resilient material surrounding the second bore acting as an extensible finger adapted to decrease in diameter to prevent removal of said boot.

Description

United States Patent [1 1 Goldowsky 1 Oct. 7, 1975 CABLE BOOT [75] Inventor: Michael P. Goldowsky, Tarrytown,

[73] Assignee: Kings Electronic Company, Inc.,

Tuckahoe, NY,

22 Filed: Mar. 7, 1974 21 Appl. No.: 449,089

[52] US. Cl. 174/138 F; 174/74 A; 339/213 R [51] Int. Cl. H01B 17/00 [58] Field of Search 174/74 A, 84 R, 84 C, 87, 174/138 F, 135; 339/101, 103 R, 213 R, 213

[56] References Cited UNITED STATES PATENTS Woofter 339/101 x Moulin 339/103 R 3,522,578 8/1970 Newman 339/101 3,528,051 9/1970 Toedtman et a1 339/101 FOREIGN PATENTS OR APPLICATIONS 1,174,868 6/1964 Germany 339/101 Primary ExaminerArthur T. Grimley Attorney, Agent, or FirmBierman & Bierman [57] ABSTRACT A cable boot for protecting cables in which a resilient material is provided with a first bore extending partially through said material and a second bore of lesser diameter than the first bore extending the remaining distance through said material, the resilient material surrounding the second bore acting as an extensible finger adapted to decrease in diameter to prevent removal of said boot.

9 Claims, 2 Drawing Figures U.S. Patent Oct.7,1975 3,911,203

CABLE BOOT The present invention relates to cable boots and more specifically to resilient cable boots for electrical wires.

Cable boots are generally used to cover electrical wires in regions subject to bending stress. The boot tends to prevent sharp bends in the wire and generally prevents wire breakage which might otherwise occur. Most boots are rather stiff, hard to place on the wire, and are generally fairly easy to remove.

When cables are to be disconnected, people generally tend to pull the cable itself rather than the plug or connector the cable is attached to. All too frequently, the boot is removed because it is the item pulled, and the cable is left unprotected in the region of the connector. One solution has been to provide a molded on boot on the cable or to provide the connector body with one or more openings in which mating portions of the boot are designed to fit. The molded on boot is clearly unsatisfactory in that it is not removable from the cable. ln industrial applications, as well as household applications, the cable to which the boot is integrally attached is not readily replaceable in the field, and it also prohibits inspection of the cable section covered by the boot.

In accordance with the instant invention, a novel boot is provided combining both manufacturing ease and surprisingly simple construction, yet overcoming all of the above problems encountered by the prior art devices. In summary, the instant invention comprises an elongated boot made of resilient material and having two different diameter bores therein. The first extends from the rear of the boot a selected distance forward. The second bore is somewhat smaller in diameter than the first bore, is in communication with the first bore, and extends the remaining distance through the boot. The smaller bore is a gripping bore adapted to initially contact the cable and to increase its gripping force to firmly grip the cable when the boot is pulled from any point other than at the head of the boot.

Referring now to the drawings wherein like numerals refer to like parts:

FIG. 1 is a detail plan view of a preferred boot made in accordance with the present invention with cable inserted.

FIG. 2 is a detail view of the boot of FIG. 1 with a cable installed on the connector.

In the drawings, denotes the boot and the numerals l2 and 14 denote the first and second bores respectively.

Boot 10 is made of a high friction elastic material, preferably insulating, such as natural rubber, soft buna- N, which is a nitrile-butadiene polymer soft neoprene or polychloroprene also a polymer, etc. Boot 10 is cylindrical and increases in external diameter from the rear 16 to the front 18. The external diameter of the boot is made large enough to provide a sufficient amount of material to protect the cable 20 against sharp bends. Although the external diameter of the boot is shown as increasing along its length, the boot may be made using a constant external diameter, if desired.

As is readily apparent, the diameter of cable 20 is approximately equal to the diameter of the second bore 14 and is somewhat smaller than the diameter of the first bore 12. This permits the boot to be easily slipped onto the cable. In contrast, prior art boots generally run the same small diameter bore through the entire length of the boot or open up to a larger diameter at the forward end of the boot, thereby increasing the amount of force needed to move the boot along the cable to its nested position. To further ease the job of placing the boot on the cable, the foremost end of bore 14 is provided with a chamfer 26 to help prevent the boot from rolling under when the boot is moved over the cable.

Generally, the second or forward bore 14 is made approximately equal to the diameter of the cable it is fit over. In cases in which the cable 20 is fitted with a crimp connector sleeve 30 (FIG. 2), the bore 14 is made slightly larger than the cable so that the inner diameter of the bore will be snug on the sleeve 30.

An annular slot 22 is formed in the boot and extends for most of the length of the second bore 14, thereby creating a finger 15 within the boot which encompasses bore 14. In operation, the resilient material of the boot allows the inner diameter of the first and second bores to decrease or increase depending on whether a stretching force or a compression force is applied to the boot. For instance, when the boot is being installed on the cable, it is pushed from the rear. Since bore 14 contacts the cable surface or the sleeve surface (FIG. 2), a slight frictional force is generated between the boot and cable along the length of the second bore 14. The frictional force so generated acts to oppose movement of the'boot onto the sleeve. This opposing force also acts to increase the radial stress in the material surrounding the second bore and to expand its diameter. It can be readily appreciated that a minimum amount of drag will be present during installation of the boot since the diameter of the first bore will expand to keep drag at a minimum.

When the boot has been installed, the second bore is in contact with the cable or sleeve. If the boot is pulled at the rear in the region of the larger bore 12, the frictional force between the second bore and the cable or sleeve will act to oppose motion, thereby setting up radial stresses in the finger 15. The radial stress tends to decrease the diameter of the finger, thereby causing the finger to neck down and tightly grip the cable or sleeve. It should be understood that the inner diameter of the finger 15 does not actually decrease. However, the radial or normal force applied by the material of the finger to the cable or sleeve does increase in direct proportion to the amount of neck down which would have occurred if there were no cable to prevent such a neck down.

The finger 15 is surrounded by an extension 32 of the boot separated from the finger by annular slot 22. When the boot is pulled from the rear thereof, the extension 32 allows all of the axial force to be taken by finger 15 at its rear, thereby permitting the finger to neck down to tightly grip the cable.

The extension performs another important function, in that force applied over the surface of the extension to remove the boot will instead be effectively applied to the rear of the finger rather than to, the outer surface of finger 15. More specifically, if one presses on the surface of extension 32 and then attempts to pull the boot off the cable, the pulling force will be effectively transferred by the boot to the rear of the finger. in the area over which one presses the extension, a radial force will be applied to the finger since the extension will be urged into contact with the finger 15 in the region of applied pressure. However, the finger and extension 32 are separate and will slide with respect to each other, thereby applying the greater pulling force to the rear of the boot. Since the pulling force is then transmitted to the back of the finger 15 as explained above, the finger will tend to neck down and tightly grip the cable even though the axial removal force is applied on the extension 32.

For best results, annular slot 22 is designed to leave a small space between the extension 32 and finger when the boot is on the cable or sleeve to allow the finger to act with little frictional influence of the extension possible.

In order to remove the boot, force must be applied at the extreme forward end of the finger at about the point indicated by the line connected to numeral 18. Force applied at this point will tend to increase the inner diameter of the finger 15 to permit the boot to be removed easily and simply from the cable.

Although it is possible to dispense with the extension 32, it will be appreciated that the exposed surface of the finger, when subjected to a removal force, will not tend to neck down to the same degree it would with the extension present, since the force is no longer applied to the back of the finger. For best results, extension 32 should be used.

In those instances in which a cable connector of the type shown in FIG. 2 is used, the connector sleeve 30 is generally slightly larger than the cable 20. The second bore 14 in finger 15 is preferably made somewhat larger than the cable, but smaller than the sleeve, so that it will snugly fit over the crimped portion of the connector when the boot is applied. Many connector sleeves have expanded ends 34 which will tend to bite 'into the rubber of the boot. These expanded ends,

which usually come about as the result of crimping the sleeve on to the cable. also help keep the boot on the cable.

As shown in FIGS. 1 and 2, a third bore 36 may be provided at the rearward end of the boot to help seal the boot against dirt and moisture. Ribs 24 may be provided to give additional strength to the boot. The ribs 24 stiffen the boot in the flexure mode and help assure that a proper radius of curvature will result when the boot is flexed. The ribs 24 also help to stabilize the boot in the axial direction to keep it from buckling when the boot is placed on the cable or sleeve.

Although the second bore 14 is shown as having a single diameter, it should be understood that the second bore can be made as a plurality of stepped bores having different diameters. Preferably, the diameters of these bores decrease from the rear of the finger to the front thereof. In addition, the largest diameter bore should be made to fit snugly on the cable or connector sleeve, if a connector sleeve is used. The term second bore, as used in this specification and claims appended hereto, shall be construed to cover both a single diameter bore and a stepped diameter bore as described hereinabove.

It is understood that many modifications can be made resilient material, a first bore extending partially along the length of said elongated body. at least one additional second bore of lesser diameter than said first bore in communication with said first bore, said second bore extending the remaining length of said elongated body, the material surrounding said second bore comprising a finger adapted to contact the surface of a cable, an extension surrounding said finger and being connected to said body only in the region at which second bore communicates with said first bore, an annular slot separating said extension from said finger, said finger extending substantially along the length of said second bore.

2. The boot specified in claim 1 wherein said material is an insulating material.

3. The boot specified in claim 1 wherein said material is nitrile-butadiene.

4. The boot specified in claim 1 wherein said second bore has a single diameter throughout its length.

5. The boot specified in claim 1 further comprising a third bore in communication with said first bore and positioned on the end of said first bore opposite that of said second bore, said third bore having an inner diameter substantially the same as that of the cable the boot is placed on.

6. The boot specified in claim 1 further comprising a plurality of stiffening ribs positioned on the outer surface of said boot.

7. A boot for cables having a connector sleeve thereon comprising an elongated body of resilient material having a first bore larger than said cable, said first bore extending partially through the length of said elongated body, a second bore smaller than said first bore and substantially equal in size to said connector sleeve, said second bore being in communication with said first bore and extending the remaining distance through the length of said body, said body having an annular slot extending thereinto from the end at which the second bore exits the body to form an extension which surrounds at least a portion of said second bore, the material of said second bore surrounded by said annular slot frictionally contacting said sleeve and tightly gripping said sleeve when force is applied to said boot at a point other than the point at which said second bore exits said elongated body to prevent accidental removal of said boot from said cable.

8. The boot specified in claim 7 wherein said connector sleeve has an extension thereon for engaging the interior wall of said second bore.

9. The boot specified in claim 7 wherein said second bore has a single diameter throughout its length.

l l l l

Claims

1. A boot for cables comprising an elongated body of resilient material, a first bore extending partially along the length of said elongated body, at least one additional second bore of lesser diameter than said first bore in communication with said first bore, said second bore extending the remaining length of said elongated body, the material surrounding said second bore comprising a finger adapted to contact the surface of a cable, an extension surrounding said finger and being connected to said body only in the region at which second bore communicates with said first bore, an annular slot separating said extension from said finger, said finger extending substantially along the length of said second bore.

3. The boot specified in claim 1 wherein said materiaL is nitrile-butadiene.