Self-locking strain-relief end bell for electrical connector assembly

United States Patent [19] [ii] Patent Number: 4,808,123

Dee et al. [45] Date of Patent: Feb. 28, 1989

1 2

ciably larger or heavier than conventional end bells, SELF-LOCKING STRAIN-RELIEF END BELL FOR especially in the aerospace industry, where minimizing ELECTRICAL CONNECTOR ASSEMBLY weight is always a vital concern. Furthermore, an end

bell with these features should also be relatively simple BACKGROUND OF THE INVENTION 5 and economical to manufacture.

This invention relates generally to the field of con- SUMMARY OF THE INVENTION nection devices for electrical cables and the like. In

particular, it relates to a self-locking, strain-relief end Broadly, the present invention is a self-locking, or

bell for use in such connection devices. anti-decoupling strain-relief end bell for an electrical

Typically, an electrical cable connection assembly 10 connector, wherein the anti-decoupling mechanism

comprises a male connector, a female connector, a cou- comprises ratcheting means, operatively associated

pling ring or nut that couples the male and female con- with the end bell coupling ring, for providing a plurality

nectors, and a strain-relief member or "end bell" for of detented rotational positions for the coupling ring,

each of the connectors. while also restraining the axial movement of the cou

There are several important considerations in design- 15 pling ring relative the rest of the end bell,

ing connector assemblies. First, the connectors must be More specifically, the present invention comprises an

capable of being quickly and easily coupled and decou- end bell with a strain-relief cable clamp attached to an

pled without special tools, and with the use of no more annular fitting, with the coupling ring rotatably dis

than moderate manual effort. Second, the connectors, posed around the exterior surface of the fitting. The

once coupled, must maintain good electrical contact 20 ratcheting means, operative between the exterior sur

with each other. In the aerospace field, this second face 0f the fitting and the interior surface of the cou

consideration dictates that such connector assemblies pimg ring, includes a retainer ring seated around the

must be able to withstand severe vibrational forces exterior surface of the fitting and having a plurality of

without uncoupling. To this end, the connector indus- detents spaced around its inner periphery. The detents

try has devised a number of connector assembly designs 25 arg engaged by bearing means disposed around the

in which the coupling ring or nut has a self-locking, or exterior surface of the annular fitting In a preferred

anti-decouphng, mechanism torthe purpose ot resisting embodiment of the invention, the bearing means are a

vtbration-induceddecoupling.Theseself-lockingmech- lurali of ball beafm each contained in one of a

anisms typicaUy employ ratchetmg means between he lurali of d around the Quter ri her

couphng nut and one of the connectors for allowing the 30 The registering

coupling nut to move more easily in the coupling or ^ inner%urface of the ^4

tightening direction than m the decoupling or loosening . * , , . ... J .

direction rm^2111 outer surface of the fitting, so that fitting is

The following United States patents exemplify the substantidly prevented. The retamer ring is also fixed in

approaches taken by the prior art in this area: U.S. Pat. 35 the groove in the coupling ring, so that the retainer ring

Nos. 3,552,777-Heinrich et al.; 3,678,439- Vetter; and the c0UPlln8 TM* tum together.

3,750,087- Vetter; 3,869,186- Vetter; 4,030,789- Paoli; In the coupling ring of the end bell is threaded

4,255,008- Snyder et al.; 4,407,529- Holman; 4,508,407- onto the distal end of the connector in the usual manner,

Ball; 4,588,246-Schildkraut et al.; and 4,588,245- except that as the coupling nut is tightened, the detents

Schwartz et al 40 011 the retainer ring engage the bearings in the fitting to

While prior art anti-decoupling mechanisms for sue- provide a ratcheting action. Continued tightening

cess, several shortcomings have been noted. For exam- causes the flttin8 to compress the elastomeric in

ple, some prior art devices may require excessive man- sulator/seal that protrudes from the distal end of the

ual effort for decoupling. Others may exhibit a tendency connector receptacle. Because of the ratchetmg effect

to fail after a number of coupling/decoupling opera- 45 provided by the engagement between the detents and

tions. Several achieve satisfactory results, but only with the bearings, the coupling ring is restrained from rota

relatively complex mechanisms that are costly to manu- tion unless a manual effort is applied to turn it. Thus, the

facture. end bell is restrained from backing off under the pres

Moreover, the prior art has focused on the coupling sure of the compressed insulator/seal. Of equal imporbetween the two connectors. By and large, the interface 50 tance, the assembly is capable of withstanding severe between each connector and its associated strain-relief vibration and shock without any substantial loosening end bell has been ignored. To date, therefore, there has of the end bell. Nevertheless, the end bell can be manubeen no satisfactory way devised to minimize vibration- ally loosened with only moderate effort, induced decoupling between the end bell and the con- As will be better appreciated from the detailed denector. The typical end bell comprises a cable clamp 55 scription which follows, the present invention has a that attaches to the connector by an internally-threaded number of advantages. First, as mentioned above, it coupling ring. This arrangement is prone to vibration- provides an end bell that effectively resists vibrationinduced decoupling. To prevent such decoupling, some induced decoupling. Furthermore, this function is acmechanics have developed the practice of securing the complished by an end bell that is not significantly larger end bell to the connector with a length of wire. A seri- 60 in its outside dimensions than a conventional end bell ous problem with this practice, however, is that a piece for the same size connector. This feature allows easy of the wire occasionally works loose or falls off, with substitution of the end bell of the present invention for the possibility of causing a short circuit if it lodges in conventional end bells without substantial modificacontact with other electrical components. tions of bulkheads, partitions, housings, etc., wherein

Accordingly, there has been a long-felt, but as yet 65 the cable connectors are located. In addition, these

unmet need for a strain-relief end bell that has a simple, functional advantages are achieved with a structure that

yet reliable, anti-decoupling feature. Moreover, there is is relatively simple and economical to manufacture,

a need for such a self-locking end bell that is not appre- Moreover, this structure provides a high degree of reli3 4

ability and durability, providing an effective anti-decou- coined into the outer notch 38 by a punch or the like pling function even after a great number of coupling- applied to the exterior surface of the coupling ring 14. /decoupling operations. As shown in FIGS. 3 and 4, the annular fitting 20 is

provided with a plurality of rotational bearing elements BRIEF DESCRIPTION OF THE DRAWINGS 5 b the groove 32. In the preferred embodiment of the

FIG. lis an exploded perspective view of a preferred invention, the bearing elements 40 are ball bearings,

embodiment of the present invention, showing its rela- each disposed in an individual socket in the groove 32,

tionship to the distal end of a typical connector recepta- and spaced equidistantly around the periphery of the

cje. annular fitting 20. Other types of rotational bearings,

FIG. 2 is a top plan view of an electrical cable con- 10 such as roller bearings, can be used instead of ball bear

nector assembly with end bells in accordance with the mgs- In any event, the bearings 40 should be disposed so

present invention attached; as t0 protrude from the groove 32, thereby to be en

FIG. 3 is a cross-sectional view along line 3—3 of gageable with the retainer ring 12 and its detent notches

FIG 2- and 30. In the preferred embodiment illustrated in the draw

FIG.' 4 is a cross-sectional view along line 4—4 of 15 ings, there are six bearings 40 and twelve detent notches

■piQ 3 30. These numbers can be varied, but for best results,

the number of detents should be no less than the number

DETAILED DESCRIPTION OF THE of bearings, and there should be at least three bearings.

INVENTION The detent notches 30, engaged by the bearings 40,

Referring now to the drawings, a preferred embodi- 20 PTMide a plurality of detented rotational positions for

ment of the present invention will now be described. the cmP}m& ""f.14' thereby creating a ratcheting ac

FIG. 1 illustrates the major components of a self- *e coupling ring and the retainer ring are ro

locking, strain-relief end bell in accordance with the t08e*er mjV"pe?i° the ""f" fit mg". t

present invention. The end bell comprises a strain-relief „ t »sf' *e °ndt *eUPresent tmventl°n ,S at:

v m i 4. u ■ * • 25 tached to the distal end of the connector m the usual

member 10, a clutch ring or retainer ring 12, and an , ,. • ,„ * iV.

ii A J J r Ia Ai I ■ manner, by threading the coupling ring 14 onto the

mtemaUy-threaded coupling ring 14 Also shown in ext *acl(f 16 The distal

FIG. 1 is the distal end of cable connector receptacle 16. Qf ^ connector receptacle {6 is provided with a

As can also be seen in FIG. 1 the stram relief member ^ of s Qr ^ £ ^

10 comprises a cable clamp 18 of conventional design, 3Q ^ 2/Qf mia 2Q TMsBeiJageinent pre.

attached to the distal edge of an annular fitting 20 by a ve*ts ^ fmin from sU m m the M ^ is

pair of axially-extendmg, diametncally-opposed ears 22. tishtened

The cable clamp 1* beuig conventional need not be Contmued tightening of the coupling ring 14 after the described in detail. For the sake of completeness, how- teeth 42 engage the serrated fitting edge 2g causes the ever, it may briefly be descnbed as comprising a pair of 35 retainer ring 12 to slip ^nd the annular fltting 20 with arcuate clamping elements 24 attachable to the distal the ratcheting action created by the sequential engageends of the ears 22 by screws 26. ment of the detent notches 30 with the bearings 40, as

In the preferred embodiment of the invention, the described above. This ratcheting action continues until annular fitting 20 has a serrated proximal edge 28, as the coupling ring js fuuy tightened. As shown in FIG. 3, best shown in FIG. 1. The purpose of the serrated edge 40 the djstai end 0f tne connector receptacle contains an 28 will be explained below. elastorneric, insulating plug or seal 44, which, in turn, is

As shown in FIGS. 1, 3, and 4, the retainer ring 12 channelled through to receive a plurality of cables 46. has an inner peripheral edge that is provided with a -phe distal end of the elastorneric seal 44 protrudes plurality of equidistantly-spaced radial indentations or slightly from receptacle 16, so that it is engaged and notches 30 which, as will be described below, function 45 compressed by the annular fitting 20 as the coupling as detents in a ratcheting mechanism. As in conven- ring is tightened.

tional end bells, the coupling ring 14 is concentrically \ fully assembled connector assembly is shown in mounted around the annular fitting 20, with the interior Fig. 2. As illustrated, a male connector 48 and a female surface of the coupling ring 14 fitting around the exte- connector 50 are mated together and secured by an rior surface of the annular fitting 20 so as to be rotatable 50 annular coupling nut 52, in the usual manner. Each thereon. The exterior surface of the annular fitting 20 connector has a receptacle 16, to the distal end of which has a first circumferential groove 32 which registers is attached an end bell in accordance with the present with a second circumferential groove 34 in the interior invention. After the end bells are attached, in the mansurface of the coupling ring 14. The inner peripheral ner described above, the strain relief cable clamps 24 are edge of the retainer ring is seated in the first groove 32, 55 screwed into placed in the conventional manner, and the outer peripheral edge of the retainer ring is The ratcheting action described above provides a seated in the second groove 34 By this arrangement, the self-locking or anti-decoupling attachment between the coupling ing 14 can be rotated around the annular fit- end bell and the connector. Specifically, the ratcheting ting 20, but relative axial movement between the two action, as previously described, is a result of the multicomponents is substantially prevented. 60 pie detented rotational positions for the coupling ring Relative rotational movement between the coupling 14 and the retainer ring 20, which turn as a unit due to ring 14 and the retainer ring 12 is substantially pre- the engagement between the protrusion 36 and the vented by the engagement of an inward protrusion 36 notch 38, as mentioned above. Because these multiple on the interior surface of the coupling ring with an rotational positions are detented, the coupling ring is outer notch 38 in the outer peripheral edge of the re- 65 restrained from "backing off", or turning in a loosening tainer ring, as shown in FIG. 4. This arrangement en- or decoupling direction, as a result of vibration or physsures that the coupling ring and the retainer ring rotate ical shock. Moreover, this ratcheting effect allows the together as a unit. The protrusion 36 is preferably coupling nut to be more tightly fastened against the