IL35917A - Strain relief for electrical connectors - Google Patents

Description

Strain relief for electrical connectors THE BUNKER-RAiiO CORPORATION Shis invention, relates to a strain relief for electrical connectors and more particularly to a highly reliable strain relief in which a cable is readily installed and securely held against axial displcaement , Strain relief arrangement© designed to prevent cable© from bei g pulled out of electrical connectors are known in th art but have been relatively complicated in construction, have not been easy to install and have not always been reliable* This invention was evolved with the general object o overcoming disadvantages of prior art strain relief arrangements and of providing a strain relief which is relatively simple in construction and economically manufact rable while being readily installed and. very rugged, durable and reliable. According to this invention, such a strain relief" arrangement is provided comprising a hollow shell arranged to receive one end of a cable, compressible means arranged to surround a portion of said cable within said shell, and a tubular member arranged in one end of said shell to compress said compressible means into tight engagement with the cable within said shell, said compressible means comprising a generally C-shaped resilient metal member, and said tubular member having an internal surface of generally frustoconioal shape arranged to wedge said C-shaped member inwardly into tight engagemen with the cable within said shell, said shell having an internal shoulder therewithin at the inner end of said end portion thereof, said compressible means further comprising an annular member of elastomerii material arranged to b© axially compressed between said shoulder and an inner end of said tufcular member by axial movement of said tubular member, to cause the inner surface of said elastomeric annular member to be moved radially inwardly into tight engagement with said cable. to COGO the inner ourfooo of tho onnuton mombor †o~bo forood -E-adiotly Iut'o tight anyuyomont with tho cable. Preferably, the annular member has an annular recess in the outer surface thereof effective to cause the inner surface thereof to be bowed radially inwardly when compressed axial ly. An annular metal member of generally L-shaped cross-section is provided on one side of the annular member of elastomeric material, to contain the annular member while applying compressive forces thereto.

Either the C-shaped resi lient metal member of the annular member of elastomeric material might be used alone but with a com ination thereof, a very rugged and reliable connection is obtained to prevent axial displacement of the cable within the she 11.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate a preferred embodiment and in which: FIGURE I is an expanded view of an electrical connector incorporating a strain relief according to the principles of this invention, showing the parts before assembly; FIGURE 2 is a view partly in cross-section showing an assembled connector; and FIGURE 3 is a perspective view of a C-shaped member of the connector.

Reference numeral 10 generally designates an electrical connector incorporating a strain relief constructed in accordance with the principles of this invention. The connector 10 comprises a main connector shell II within which contacts are supported in an insulating body for connection to mating contacts of another connector shell, not shown. An auxiliary shell 12 is provided arranged to be secured to the main shell II by means of a coupling ring 13 having an internal ly threaded portion 14 which Is threaded on an externally threaded portion 15 of the shell II. The coupling ring 13 is held on the shell 12 by means of a snap ring 16 engaged in annular grooves in the outer surface of the shell 12 and in the inner surface of the coupling ring 13, the coupling ring 13 being rotatable relative to the shell 12.

An annular groove 17 is provided on the inside surface of the shell 12, adjacent the end thereof connected to the shell II, for receiving a conventional 0-ring seal member 18 which is compressed against an outer surface portion of the shell II, To prevent relative rotation of the shells II and 12, the internal surface of the shell 12, between the end thereof and the notch 17, is formed with equi-angularly spaced notches 19 which receive equi -angularly spaced projections 20 on the portion of the outer surface of shell II which is adjacent the threaded portion 15.

A knurled disc 21 is provided at the end of shell II.

A tubular member 22 is arranged to be moved into an opposite end portion 23 of the shell 12 and to force two forms of compressible means into tight engagement with the outer surface of an end portion of a cable 24 positioned within the shell 12. One of such compressible means comprises an annular member 25 of elastomeric material, such as a relatively soft natural rubber or an equivalent material, which is axial ly compressed between an internal annular shoulder 26 of the shell 12 and an Inner end surface 27 of the tubular member 22. An annular metal member 28 is provided of general ly L-shaped cross-section having a first wall 29 between an end surface of the member 25 and the end surface 27 of the member 22 and having a second wall 30 surrounding an end portion of the member 25.

The second form of compressible means comprises a generally C-shaped resilient metal member 34 which is engaged by an Internal surface 35 of the member 22 of generally frusto-conical shape to wedge the member 34 inwardly into tight engagement with the cable 24, when the member 22 is moved into the end portion 23 of the shell 12. The C-shaped member 34 preferably has a curved cross-sectional shape to provide a rounded convex outer surface 36 engageable by the surface 35 and to provide a pair of relatively sharp side edges 37 and 38 arranged to bite into the cable at axial ly spaced points.

According to a further feature, the tubular member 22 has an externally threaded portion 39 which is threaded into an internally threaded portion 40 of the end portion 23 of shell 12.

The illustrated connector 10 is designed for use with a cable having an outer sheath of woven metal or the like and to receive and ground the sheath, a member 42 is provided having a wall 43 positioned between the inner end of the shell II and a shoulder 44 on the inside of the shell 12. The member 42 has a generally cylindrical wall into which axial ly extending slots are cut to form four relatively resilient fingers 45 which preferably have inwardly turned terminal end portions 46.

In the assembly of the connector, the shell 12, and members 22, 25, 28, 34 and 42 are slid onto the end of the cable 24, in relative positions as shown in Figure I, and an outer sheath 47 of the cable 24, preferably of a woven metal material with an outer jacket 47a of a tough plastic material or the like, is expanded at one end of the cable and slipped onto the outside of the member 42, around the fingers 45, the outer jacket 47a being removed from the position of the sheath 47 around the fingers 45. The ends of wires 48 within the cable 24 are stripped of insulation and connected to contacts, not shown, within the connector 10 and any wires or contacts to be grounded may be connected to a terminal 49 on the member 42. The she I I 12 is then moved toward the shell II and the ring 13 is- threaded onto the threaded portion 15 of the shell II. The sheath is engaged between the resilient fingers 45 and an internal smoothly rounded surface 50 of the shell 12.

Next, the annular member 25 of the elastomeric material together with the metal member 28 are moved within the end portion 23 of the shell 12 and the member 34 is moved to abut the wall 28 of the member 27. Finally, the tubular member 22 is threaded into place within the end portion 23 of the shell 12, as shown in Figure 2, which serves to axial ly compress the member 25 and to force the inner surface thereof into tight sealing engagement with the outer surface of the outer jacket 47a. At the same time, the member 34 is wedged by the surface 35 into tight engagement with the outer jacket 47a, with biting engagement between the edges 37 and 38 and the outer jacket 47a.

The cable 24 is thus securely locked against axial movement and could not be pulled out of the connector without the exertion of an extremely high force. At the same time, a seal is provided.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.

Claims (1)

1. Strain relief arrangement for electrical connecto comprising a hollow shell arranged to one end of compressible means arranged to surround a portion of said cable within said and tubular arranged in one end of said shell to compress said compressible means into tight engagement with the cable within said said compressible means comprising a generally resilient metal and tubular member an internal surface of generally fruatoconical shape arranged to wedge said member inwardly into tight engagement with th cable within said ehell having an internal shoulde at the inner end of said end portion said compressible further comprising an annular member of material be compressed between said shoulder and inner end of said tubular member axial movement of said tubular to camse the inner surface of said elastomeric annular member to be moved radially inwardly into tight engagement with said Strain relief arrangement for an electrical connector according to Claim said tubular member being threaded into said relief for an electrical connector according an metal member o generally cross section having a first wall between an end surface of said annular member of elastomeric material and said end of said tubular member and having a second wall surrounding one end portion of said annular member of elastomeric said member having an outer dlmeneion greater than the diameter of aaid annular metal member of d cro s sect n Strain relief arrangement for an electrical connector substantially as described herein with reference to the accoiBpanying For the Applicants insufficientOCRQuality