Modular connector assembly which provides strain relief

Abstract: A strain relief member (24) of sheet metal is disposed within the housing of a modular connector (10) having a locking bar which ordinarily is crimped into locking engagement with the wires of a multi-wire cable (20). With such an arrangement, flexure of the wires occurs at the locking bar and the wires break thereby breaking the connection provided by the connector to equipment connected to the cable. The strain relief member has a tray portion (26) over which the wires extend to contacts located near one end of a housing (14). A stem (28) extends rearwardly from the tray portion out the housing and has arms (30, 32) which are crimped around the cable thereby providing strain relief. The tray has a slot (38) therein which is disposed in alignment with the locking bar. When the locking bar is crimped, it fastens the strain relief member to the housing.

Description: The present invention relates to a connector assembly for a multi-wire cable having a plurality of wires. It is desirable to use conventional, modular connectors to terminate cables and connect them to receptacles. The cables may be used for example to connect a bar code reader to computer equipment which receives, collects and organizes information as to bar code symbols which are collected by the reader. The cable has a multiplicity of wires which carry signals and which may also carry power for operating the reader. The use of conventional, modular connectors is desirable because they are readily available at low cost. Modular connectors do not afford strain relief because they have locking bars which connect the housing of the connector to the cable, and particularly to the wires of the cable. In ordinary use, the cable flexes and repeated bending of the wires occurs where they are engaged by the locking bar. The wires then break and the cable and its connector must ordinarily be replaced. Even shrouds of elastic material which are molded over the connector and the cable where it enters the connector do not afford sufficient strain relief to prevent failures and allow reliable long-term operation. Special and considerably more expensive connectors have heretobefore been necessary to overcome the problem. One such connector is described in Miyazawa, U.S. Patent 4,714,306 issued December 12, 1987. Other similarly complex connector designs are shown in Loose, U.S. Patent 4,277,124 issued July 7, 1981; Hasircoglu, U.S. Patent 4,605,276 issued August 12, 1986; and Whiting, U.S. Patent 4,606,596 issued August 19, 1986. There are many instances when it is desirable to terminate wire leads from an apparatus at a group of pins or posts which are adapted to be frictionally engaged in a female receptacle connected by suitable leads to the rest of the circuit. This type of terminal is usually referred to as a cluster pin terminal or assembly and is typically found in refrigerating and air conditioning fields where portions of equipment are located within hermetically sealed containers or housings. Electrical connection to this sealed equipment is effected by a series of insulated pins extending through the shell of the hermetically sealed container. The pins are normally clustered together to reduce the required number of seals. Examples of such terminals are found in U.S. Pat. Nos. 2,728,060; 3,202,959; 3,336,567; and 3,605,076. Some connector receptacles previously developed have attempted to avoid loosening of the electrical contact between the connector and pin by arranging the connector in the form of a closed loop or U-shape,the free ends of which are locked against excessive or unintended spreading. Examples of this type of connector are found in U.S. Pat. Nos. 3,120,990; 3,231,849; and 3,271,729. While these closed loop connectors form a tight contact, they have the disadvantage of being somewhat expensive and complicated to form and install. Some problems encountered in the field cluster pin terminals and connectors include assuring that a good mechanical and electrical contact will be maintained with each pin despite the severe operating conditions normally encountered. These conditions include high temperatures and humidity as well as extensive and prolonged vibration. The connectors installed inside the housing are substantially inaccessible once the housing is sealed. Therefore it is a principal consideration to form the connectors in such a manner that they will not come off the pins easily and will not lose their electrical contact efficiency, since failure of the internal contacts to maintain their grip on the pins is tantamount to a complete failure of the entire unit with little possibility of effecting economic repair. Another consideration in making connectors of the present type is the fact that millions of such connectors are made yearly so that economy of production and assembly, as well as reliability, must be considered. Space requirements for cluster pin assemblies also dictate that the receptacle housing and the connectors use as small an amount of space as possible. Thus when several connectors are to be used in combination, they must be capable of being placed closely together with accurate positioning. Of course the housing must provide complete electrical isolation between the individual connectors to avoid possible arcing between adjacent connectors with consequent short circuits and damage to the attendant units. U.S. Patent 3,842,396 describes and claims a disengagable electrical connector for use with a plurality of closely spaced parallel contact pins disposed in a cup-like mounting member, said connector comprising: a unitary block of insulating material having a plurality of parallel cavities extending therethrough, each of said cavities being open at both ends and having a throat portion defined by a pair of side walls converging towards one another to merge with a pair of parallel walls which terminate in sharp shoulders extending transversely outwardly of the cavity, an abutment extending transversely across said cavity spaced from said shoulders, and a pin aperture formed in one wall of each cavity, a terminal connector received in each said cavity, each said connector having, from back to front, first and second ferrule portions adapted to be crimped onto electrical cable and a channel shaped receptacle portion including two spaced side walls resiliently integrally connected by one edge to a central web, an aperture in said central web, and a locking lance rigidly projecting from an upper portion of each side wall, each said lance projecting out of the plane of its corresponding side wall and away from the other said side wall, said side walls of said connector located between said parallel walls of said housing as said locking lances abut said shoulders, retaining said connector in said housing, said pins adapted to engage with interference fit in opposing sides of said connector aperture and between the side walls of said receptacle portion. The disclosure of U.S. Patent 3,842,396 (claims, figures) includes: a strain relief member 52 (suitable for retaining a multi-wire cable in a modular connector having a locking device), said member comprising a tray (fig. 5,6) on which the wires of said cable can (or could) be disposed; a stem (each part of the member between parts 86 and 84 or between parts 84 and 82 or the base part of the web, which can be seen in fig. 5) extending from said tray; a slot 100 in said tray (suitable for receiving a (or said) locking device, on assembly of said connector); and arms (88,90) extending from said stem, said arms being crimpable around said cable. The tray has a base in which said slot 100 is disposed, and said walls 96/98 or 90 extending in the same direction from said base, said wires being disposable between said side walls. Crimpable arms 90,82 extend from opposite sides of said stem, and any arm 90 is offset in a direction longitudinally of said stem from the arms 88. The strain relief member 52 is made of a sheet of metal. European Patent Application Specification EP-A-268129 discloses a strain relief member, made of sheet metal, comprising: a tray (1) with side wall on which the wires of a multi-wire cable can be disposed; a Z-shaped stem (see fig. 1,2a) extending from said tray; a slot (fig. 1,2a) extending from said tray; a slot (fig. 1) in said tray and suitable for receiving a locking device; crimpable arms 3,2 extending from said stem; wherein the base of the tray is offset of an end of the stem, by a distance equal to a radius of the cable. It is the principal object of the present invention to provide an improved connector assembly which provides strain relief for multi-wire cables which are attached thereto and which is low in cost. It is another object of the present invention to provide an improved modular connector providing strain relief for the cable attached thereto which is low in cost by virtue of the ability to make use of conventional modular connector housings which are readily available at low cost. It is a further object of the invention to provide an improved connector with strain relief which is adaptable at low cost for connecting multi-wire cables with different numbers of wires. It is still a further object of the present invention to provide an improved strain relief member for use in electrical connectors which enables a multi-wire cable to be attached to a connector housing with strain relief. The present invention provides a connector assembly for a multi-wire cable having a plurality of wires, said assembly comprising: a housing having opposite ends with at least one contact terminal near the front end of said opposite ends, and an opening therein from the rear end of said opposite ends, said cable being insertable into said opening such that said wires will extend into contact with individual ones of said terminals; a strain relief member disposed in said opening of the housing, the strain relief member having: a tray portion with opposite ends, the tray portion having a slot for attachment of the strain relief member to the housing; the strain relief member has a stem extending rearwardly from the tray portion, the rear of the stem having opposite sides, from at least one of which at least one crimpable arm extends to be crimpable around the cable, the wires being able to extend over the stem and the tray portion; and said housing having a crimpable locking bar extending transversely of said opening and presenting a surface facing that opening, such that when the bar is crimped said surface thereof extends into the slot so as to lock said strain relief member in place in said housing. In a said connector assembly of the present invention, the housing may be a generally rectangular polygonal body having top and bottom walls, the crimpable locking bar being disposable in one of said top and bottom walls in alignment with the slot, such that the locking bar when crimped will be disposed in the slot. The housing may be a body of thermoplastic material. The strain relief member may be a sheet of metal. Said metal may be work hardenable steel. The tray portion may have a base and sidewalls respectively extending from opposite sides of the base, the slot being disposed in the base, and the wires being disposable between the sidewalls. The base may be a flat portion of said sheet; the sidewalls may be bent portions of the sheet; and the stem may be a strip portion of the sheet, extending along the line through the center of the sheet between those sidewalls. The stem rear may of be offset from the tray portion. The stem may be Z-shaped in part; and the rear of the stem may be offset from the base of the tray portion in the longitudinal direction of the stem. The Z-shaped part may have an indentation defining a rib extending longitudinally of said part. The offset rear of the stem may be offset from the tray portion by a displacement equal approximately to the radius of the jacket of a multi-wire cable having said jacket. The crimpable locking bar may be a crimpable portion of one of the top and bottom walls of the housing. The contact terminals may be plates extending from one of top and bottom walls of the housing. The connector assembly may be connected to a multi-wire cable containing wires in a jacket, wherein: the jacket extends over the stem; the jacket has a termination at the tray portion; and the wires are disposed between the sidewalls of the base of the tray portion and extend away from the jacket termination. The jacket termination may extend into the tray portion. In the accompanying drawings which are given by way of example of the present invention: FIG. 1 is a perspective view of one example of a modular connector assembly in accordance with the invention; FIG. 2 is a plan view of the strain relief member used in the assembly shown in FIG. 1; FIG. 3 is a side elevation of the strain relief member shown in FIG. 2; FIGS 3A and B are respectively a side elevation similar to FIG. 3 and a sectional view along the line 3B-3B in FIG 3A; FIG.4 is a side view of the strain relief member shown in FIG. 2; FIG.5 is a perspective view of the strain relief member shown in FIGS. 2, 3 and 4; FIG. 6 is a plan view of the modular connector assembly shown in FIG. 1; FIG. 7 is a side elevation of the modular connector shown in FIG. 6; FIG. 8 is a sectional view of the modular connector shown in FIGS. 6 and 7, the section being taken along the line 8-8 in FIG. 6; FIGS. 9 and 9A are enlarged views of the locking bar, the view being taken along the line 9-9 in FIG. 8 with the locking bar in uncrimped and crimped condition in FIGS. 9 and 9A, respectively; FIGS. 9B & C are bottom views showing the locking bar before and after crimping, respectively. FIG. 10 is a sectional view along the line 10-10 in FIG. 8; FIG. 11 is a perspective view of the connector shown in FIG. 1 with a molded shroud of elastic material thereon; FIG. 12 is a plan view of the connector assembly shown in FIG. 11; FIG. 13 is a side elevation of the connector shown in FIG. 12; and FIG. 14 is a sectional view of the connector shown in FIG. 12 taken along the line 14-14 in FIG. 12. Referring first to FIG. 1, there is shown a modular connector assembly 10 having a modular housing 14 which is a generally rectangular polygon. This housing may be of the type which is generally available and has a front end 12 which is inserted into a receptacle containing pin terminals. The top 16 of the housing has a detent clip 18 which locks with a latch on the receptacle. A multi-wire cable 20 is inserted into the rear end 22 of the housing 14. Extending from the rear end of the housing is a strain relief member 24. This member has a tray portion 26 the end of which is visible in FIG. 1 and a stem 28 extending rearwardly from the tray portion out of the housing 14. The stem has a pair of crimpable arms 30 and 32 extending from the sides of the stem 28. These arms are crimped around the cable 20 and particularly around the jacket 34 of the cable. It will be appreciated that the jacket extends to the opposite end of the cable and that the six wires 36 extending from the cable illustrate that the cable is a multi-wire cable. It will also be appreciated that the cable can have more or fewer wires. The tray may be wider where there are more wires. The strain relief member 24 is shown in FIGS. 2, 3, 4 and 5. It is made from a sheet of metal, preferably work-hardenable steel. The tray portion 26 has a slot 38 which extends between sidewalls 40 and 42. This slot serves for attachment of the member 24 to the housing 14 as will become more apparent from FIGS. 8, 9 and 10. The stem 28 is Z-shaped so that the rear end 44 of the stem, from which the arms 30 and 32 extend, is displaced from the base 46 of the tray portion 26 by approximately half the diameter (the radius) of the cable 20. The flexure and strain due to bending of the cable 20 is exerted primarily on the Z-shaped stem portion 28. While the use of work hardenable steel causes the stem to harden and become resistant against flexure, it is also desirable to strengthen and rigidify the section with a longitudinal rib 48 which may be provided by an indentation in the middle of the Z-shaped stem as shown in FIGS. 3A and 3B. Referring to FIGS. 6, 7 and 8 there is shown, prior to crimping or staking, the connector assembly with the cable attached thereto. The wires extend over the tray and the jacket 34 termination is slightly inwardly of the rear end 50 of the tray. The wires extend over connector terminals 52 one of which is shown in FIG. 8. These terminals are blades with pointed ends 54 which are staked through the insulation surrounding the wires and into the conductive core of the wires as is conventional with modular connectors. It may also be desirable to compress the housing 14 between its top and bottom walls 16 and 17 in the bottom 56 of a slot. The bottom wall 58 of the housing in an area 55 adjacent the terminals 52 may be provided with ribs between which the individual wires are guided into the opening 60 containing the contact terminals 52. A heated swaging tool which compresses the wall and presses the bottom 56 of the slot against the wires and clamps, then to the top wall 57 of the housing may be used for this purpose. The bottom wall 58 has a locking bar 62 formed therein. The locking bar is integral with the bottom wall of the housing 14 and is in a slot 63, the sides of the locking bar being detached from the sides of the slot as shown in detail in FIG.S 9B & C. The swaging tool crimps the locking bar. Optionally and possibly in high volume automated production, the tool may be heated so as to slightly melt the thermoplastic material of the locking bar. The locking bar may be pressed into the housing 14, the contact terminals 52 may be inserted through the insulation on the wires and into contact with the conductive cores thereof, (and also the optional staking of the slot bottom 56) by a single multiple element tool on a single stroke. When the locking bar is pressed in, it is deformed and moved to the position shown in FIG. 10A. It enters the slot 38 and prevents lateral and longitudinal movement of the strain relief member 24. FIG. 14 shows the modular assembly in assembled condition with the locking bar 62 in the slot 38 of the strain relief member 24. As shown in FIGS. 11, 12, 13 and 14, a shroud of elastomeric (flexible rubber or plastic) material may be molded around the cable and extend into the slots in the bottom wall of the housing 14. This elastic material shroud is indicated at 60. It will also be observed that the cable 20 overlies the stem 28 of the strain relief member 24. The holes 62 are used to hold the cable 20 centered in the mold during the molding process. From the foregoing description, it will be apparent that there has been provided an improved electrical connector in which the strain relief for the wires of a multi-wire cable is provided and also an improved strain relief member. Variations and modifications in the herein-described connector and strain relief member, within the scope of the invention, will undoubtedly suggest themselves to those skilled in the art. Accordingly the foregoing description should be taken as illustrative and not in a limiting sense. It will be appreciated that in one embodiment of the present invention, a strain relief member of sheet metal is disposed within the housing of a modular connector having a locking bar which ordinarily is crimped into locking engagement with the wires of a multi-wire cable. With such an arrangement, flexure of the wires occurs at the locking bar and the wires break thereby breaking the connection provided by the connector to equipment connected to the cable. The strain relief member has a tray portion over which the wires extend to contacts located near one end of the housing. A stem extends rearwardly from the tray portion out the housing and has arms which are crimped around the cable thereby providing strain relief. The tray has a slot therein which is disposed in alignment with the locking bar. When the locking bar is crimped, it fastens the strain relief member to the housing. In the present invention, a multi-wire cable may comprise any suitable plurality of wires. The term "Z-shaped" also includes any shape that is substantially Z-shaped.

Claims: A connector assembly (10) for a multi-wire cable (20) having a plurality of wires (36), said assembly comprising: a housing (14) having opposite ends (12,22) with at least one contact terminal (52) near the front end (12) of said opposite ends, and an opening therein from the rear end (22) of said opposite ends, said cable being insertable into said opening such that said wires will extend into contact with individual ones of said terminals; a strain relief member (24) disposed in said opening of the housing, the strain relief member having: a tray portion (26) with opposite ends, the tray portion having a slot (38) for attachment of the strain relief member to the housing; the strain relief member (24) has a stem (28) extending rearwardly from the tray portion, the rear (44) of the stem having opposite sides, from at least one of which at least one crimpable arm (30,32) extends to be crimpable around the cable, the wires being able to extend over the stem and the tray portion; and said housing having a crimpable locking bar (62) extending transversely of said opening and presenting a surface facing that opening, such that when the bar is crimped said surface thereof extends into the slot (38) so as to lock said strain relief member in place in said housing. A connector assembly as claimed in claim 1, characterised by the housing is a generally rectangular polygonal body (14) having top and bottom walls (57,58), the crimpable locking bar (62) being disposable in one of said top and bottom walls in alignment with the slot (38), such that the locking bar when crimped will be disposed in the slot. A connector assembly as claimed in claim 1 or 2, characterised by the housing (14) is a body of thermoplastic material. A connector assembly as claimed in any one of claims 1 to 3, characterised by the strain relief member (24) is a sheet of metal. A connector assembly as claimed in claim 4, charaterised by said metal is work hardenable steel. A connector assembly as claimed in any one of claims 1 to 5, characterised by the tray portion (26) has a base (46) and sidewalls respectively extending from opposite sides of the base, the slot (38) being disposed in the base, and the wires being disposable between the sidewalls. A connector assembly as claimed in claim 6, characterised by the base (46) is a flat portion of said sheet; the sidewalls (40,42) are bent portions of the sheet; and the stem is a strip portion of the sheet, extending along the line through the center of the sheet between those sidewalls. A connector assembly as claimed in any one of claims 1 to 7, characterised by said stem rear (44) is offset from the tray portion. A connector assembly as claimed in 8, characterised by the stem (28) is Z-shaped in part; and the rear (44) of the stem is offset from the base (46) of the tray portion in the longitudinal direction of the stem. A connector assembly as claimed in claim 9, characterised by said Z-shaped part has an indentation defining a rib (48) extending longitudinally of said part. A connector assembly as claimed in claim 9 or 10, when according to claim 6 or 7, characterised by the offset rear (44) of the stem is offset from the tray portion (26) by a displacement equal approximately to the radius of the jacket of a multi-wire cable having said jacket. A connector assembly as claimed in any one of claims 1 to 11, whan according to claim 2, characterised by the crimpable locking bar (62) is a crimpable portion of one of the top and bottom walls (57,58) of the housing. A connector assembly as claimed in any one of claims 1 to 11, when according to claim 2, characterised by the contact terminals (52) are plates extending from one of top and bottom walls (57,88) of the housing. A connector assembly as claimed in any one of claims 1 to 13, when according to claim 6 or 7 and connected to a multi-wire cable containing wires in a jacket (34), wherein: the jacket extends over the stem (28); the jacket has a termination at the tray portion (26); and the wires are disposed between the sidewalls of the base (46) of the tray portion and extend away from the jacket termination. A connector assembly as claimed in claim 14, wherein the jacket termination extends into the tray portion.

Inventors: EASTMAN JAY M, EASTMAN, JAY M.
Applicants: PSC INC, PHOTOGRAPHIC SCIENCES CORPORATION
Application year: 1990
Main classification: H01R13
IPC codes: H01R13, H01R4