A FRICTION FIT STRAIN RELIEF BOOT

Abstract: A strain relief boot (10) in combination with a cable (15). The strain relief boot (10) has a body (11) having a rigid portion (12) and a flexible portion (13). A center bore (14) extends through the body (11) and the cable (15) is slidingly disposed in the center bore (14). The body (11) has an inner wall (20) surrounding the center bore (14). A plurality of spaced-apart ribs (21) are formed on the inner wall (20) of the rigid portion (12). Each rib (21) has a top surface (22) and a pair of adjoining sidewalls (23). The ribs (21) extend inwardly into the center bore (14) and grip the cable (15) with a friction fit, retaining the strain relief boot (10) on the cable (15).

Description: A FRICTION FIT STRAIN RELIEF BOOT The present invention relates to a strain relief boot for use with a cable and more particularly, to a strain relief boot which is removably retained on the cable by friction fit. There is an effort under way in the industry to provide connectors for wiring that are approved by the Underwriters Laboratory. The connectors which are presently approved have strain relief boots which are secured to the cables by an epoxy adhesive. Unfortunately, in the event of a fire, the epoxy adhesive burns with the production of noxious fumes. Furthermore, the use of an adhesive requires man hours to apply the adhesive and to assemble the system in addition to requiring curing time for the adhesive to harden. The cost of the adhesive is added to the labor costs. A further problem is that the epoxy adhesive produces an attachment which cannot be removed. U.S. Patent 4,930,856 discloses a strain relief boot adhered to a cable with epoxy. The applicants are also aware of snap fits and threaded means for attaching strain relief boots to cables as in the following: U.S. Patent Nos. 4,813,760, 5,062,683, and 5,202,942. The strain relief boots disclosed in these references are complex, difficult to manufacture and require excessive time to assemble. A need exists for a simple, easily manufactured strain relief boot which can be assembled rapidly, is cost effective, is removable and does not produce noxious fumes in the event of a fire. It is an object of the present invention to provide a strain relief boot which can be assembled to a cable without the use of adhesive and which is removable. It is a further object of the present invention to provide a strain relief boot which can be molded inexpensively and which can be joined to a cable in a cost efficient manner. In accordance with the teachings of the present invention, there is disclosed herein a strain relief boot in combination with a cable. The strain relief boot has a body with a rigid portion and a flexible portion. The body has a center bore extending therethrough. The cable is slidingly disposed in the center bore. The body has an inner wall. A plurality of spaced-apart ribs are formed on the inner wall of the rigid portion of the body. Each rib has a top surface and a pair of sidewalls. The ribs extend inwardly into the center bore. In this manner, the ribs grip the cable with a friction fit and retain the strain relief boot on the cable. An embodiment of the present invention will now be described by way of example with reference to the following drawings in which: FIG. 1 is a perspective view showing the strain relief boot of the present invention attached to a cable. FIG. 2 is a cross-sectional view taken along the lines 2-2 of FIG. 1. FIG. 3 is a cross-sectional view taken along the lines 3-3 of FIG. 2, the cable not being shown. FIG. 4 is a perspective view showing the cable received in the strain relief boot. Referring to FIGS. 1-4 the strain relief boot 10 has a body 11 which further has a rigid portion 12 contiguous with a flexible portion 13. The flexible portion 13 may have a plurality of openings formed therein and may have a plurality of fluted or hinged segments or other means to provide flexibility. A center bore 14 is formed in the body 11 and extends throughout the length of the body. A cable 15 may be for electrical or optical use and the strain relief boot 10 provides mechanical support for the cable 15 to reduce the possibility of damage to the cable 15 or the inner cable 16. The cable 15 may have an eyelet or other portion which is slidingly received in the center bore 14 of the strain relief boot 10. The body 11 has an inner wall 20 which surrounds the center bore 14. A plurality of ribs 21 are formed on the inner wall 20 of the rigid portion 12 of the body 11. The ribs 21 are spaced apart from one another and extend inwardly into the center bore 14. It is preferred that there be eight ribs 21 although a greater or a lesser number of ribs 21 may be formed. For improved gripping of the cable 15, it is preferred that pairs of ribs 21 be formed opposing one another. The choice of the number of ribs 21 is a function of the ease of manufacture of the ribs and the tooling to form the strain relief boot. Another consideration in determining the number of ribs 21 is to provide for the strain relief boot 10 to be centered geometrically on the cable 15. Each rib 21 has a top surface 22 and a pair of adjoining sidewalls 23. Each sidewall 23 extends from the top surface 22 of each rib 21 to the inner wall 20 of the rigid portion 12 of the body 11. Each rib 21 is disposed in a plane 24, the plane 24 bisects the body 11, passing through the center point of the body 11. The plane 24 also bisects the respective rib 21. Each sidewall 23 of each rib 21 is chamfered at an angle α of approximately 20°-30° with respect to the plane 24 of the respective rib 21. An angle a of 25° is preferred to obtain uniform compression on the cable 15. The top surface 22 of each rib 21 may be arcuate to more nearly conform to the cylindrical form of the cable 15 and to assure improved contact between the respective ribs 21 and the cable 15. The friction fit between the top surface 22 of the ribs 21 and the cable 15 is sufficient to retain the strain relief boot 10 on the cable 15 while permitting ease of assembly of the components. The ribs 21 are circumferentially spaced substantially parallel to one another and extend longitudinally on the inner wall 10 of the rigid portion 12 of the body 11 from near the end of the rigid portion 12 toward the flexible portion 13. Each rib 21 has a first end 25 which is distal from the flexible portion 13 of the body 11. Each first end 25 is tapered from the inner wall 20 toward the top surface 22 of the respective rib 21 at an angle β of approximately 30°. In this manner, when the cable 15 is slidingly disposed into the rigid portion 12 of the body 11 (FIGS. 1 and 4) the cable 15 initially contacts the tapered first ends 25 of the ribs 21 and sliding disposition of the cable 15 is facilitated. The friction fit of the strain relief boot 10 on the cable 15 due to the contact of the cable 15 with the plurality of ribs 21, permits the removal of the strain relief boot 10 from the cable 15. When required, the mated cable 15 and strain relief boot 10 may be pulled apart without using undue force so that the members are not damaged. In this manner, the present invention provides versatility not possible with strain relief boots of the prior art which were joined with epoxy adhesive. In the event of a fire, the present invention also avoids the generation of noxious fumes produced by the combustion of epoxy adhesive. Obviously, many modifications may be made without departing from the basic spirit of the present invention. Accordingly, it will be appreciated by those skilled in the art that within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.

Claims: WHAT IS CLAIMED IS; 1. A strain relief boot in combination with a cable, the strain relief boot comprising a body having a rigid portion and a flexible portion, the body having a center bore extending therethrough, the cable being slidingly disposed along the center bore, the body having an inner wall surrounding the center bore, a plurality of spaced-apart ribs formed on the inner wall, each rib having a top surface and a pair of adjoining sidewalls, the ribs extending inwardly into the center bore, wherein the ribs grip the cable with a friction fit and retain the strain relief boot on the cable. 2. The strain relief boot of claim 1, wherein the ribs are circumferentially spaced approximately parallel to one another and extend longitudinally on the inner wall of the rigid portion of the body. 3. The.strain relief boot of claim 2, wherein the ribs are equally spaced. 4. The strain relief boot of claim 1, wherein the ribs are disposed in pairs opposite of one another. 5. The strain relief boot of claim 1, wherein each rib is disposed in a plane, the plane bisecting the body and bisecting the respective rib, each sidewall being chamfered at an acute angle with respect to the bisecting plane. 6. The strain relief boot of claim 5, wherein the acute angle is approximately 20°-30°. 7. The strain relief boot of claim 6, wherein the acute angle is 25°. 8. The strain relief boot of claim 1, wherein each rib has a first edge, each first edge being distal from the flexible portion, each first edge being tapered at an acute angle from the inner wall toward the top surface of the respective rib, wherein sliding disposition of the cable into the strain relief boot is facilitated. 9. The strain relief boot of claim 8, wherein the acute angle is approximately 30°. 10. The strain relief boot of claim 1, wherein the top surface of each rib is arcuate.

Inventors: CHRISTNER THOMAS LEE, PETERSON MATTHEW ALAN, WERTMAN DANIEL ERLIN, CHRISTNER, THOMAS, LEE, PETERSON, MATTHEW, ALAN, WERTMAN, DANIEL, ERLIN
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1995
Main classification: G02B6
IPC codes: G02B6