US 3813634 A
A strain relief construction for use with electrical connectors for flat ribbon cable or the like comprises two mating members having complementary tape confronting surfaces which are substantially S-shaped in cross section and substantial mirror images of each other. The two members are joined together with a portion of the flat cable clamped between the complementary surfaces and formed into a similar S-shaped curve thereby. The two members may, for example, form a cable plug or receptacle connector, or the strain relief construction may be used in other applications such as in making cable connections to printed circuit boards.
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Description (OCR text may contain errors)
United States tent n 1 Wigby et a1.
1 1 STRAIN RELIEF FOR FLAT CABLE OR THE LIKE  Inventors: Jon Wigby, Sandy Hook; Leonard St. Jacques, South Norwalk, both of Conn,
 Assignee: Burndy Corporation, Norwalk,
 Filed: Dec. 29, 1972  Appl. No.: 319,149
 References Cited UNITED STATES PATENTS Harthman et al 339/105 X Crimmins 339/17 F [451 May as, 1974 3,336,565 8/1967 Crimmins 339/107 3,601,768 8/1971 Lightner 339/176 MF X 3,737,833 6/1973 Jerominek 339/107 X Primary Examiner-Richard E. Moore Attorney, Agent, or Firml-loward S. Reiter [5 7] ABSTRACT A strain relief construction for use with electrical connectors for flat ribbon cable or the like comprises two mating members having complementary tape confronting surfaces which are substantially S-shaped in cross section and substantial mirror images of each other. The two members are joined together with a portion of the flat cable clamped between the comple mentary surfaces and formed into a similar S-shaped curve thereby. The two members may, for example, form a cable plug or receptacle connector, or the strain relief construction may be used in other applications such as in making cable connections to printed circuit boards.
1 Claim, 5 Drawing Figures STRAIN RELIEF FOR FLAT CABLE OR E LIKE BACKGROUND or THE INVENTION Flat ribbon cable of a type such as that shown in US. Pat. No. 3,239,916 has become widely used for many applications including communications and aerospace. To facilitate its use the cable is typically provided with electrical connectors, and many such connectors of varying design have been devised. A problem common to the use of most such connectors is that tensile and vibratory loads imposed on the cable may break or damage the terminal connections. It is desirable therefor to provide a means on the connector for absorbing the effect of such loads.
A means which has been used in other arts to absorb tensile and vibratory loads on ribbon members are pinch rollers; these are commonly and successfully used in conveyors, roll film cameras, magnetic tape drives and the like. Pinch rollers per se, however, do not lend themselves to use in the type of molded electrical connectors typically used with flat cable for they would, require an excess number of parts and would complicate assembly.
Accordingly, representative objects of the present invention are to provide a method and apparatus for strain relief of ribbon cable or the like which functions in a manner similar to the function of pinch rollers and is adapted for use with cable connectors, the strain relief apparatus being economical to fabricate, easily assembled and effective.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangements of parts which are adapted to effect such steps, all as exemplified in the following disclosure, and the scope ofthe invention will be indicated in the claims.
SUMMARY OF THE INVENTION The present invention relates to a method and apparatus for providing strain relief in flat ribbon cable or similar articles, and more particularly to a strain relief construction especially applicable for use with the type of molded electrical connectors typically used with such cable.
The strain relief construction comprises two parts, each having a cable-confronting face which is substantially S-shaped. The two confronting faces are also substantial mirror images and thus fit together in a complementary manner. Preferably, one confronting face is formed on a surface of a contact-carrying electrical connector member such as a plug or receptacle connector. The other face is preferably formed on a mating insert member. The insert and connector members are then assembled and secured together with a portion of the cable clamped between and conforming to the complementary S-shaped faces. In this way tensile and vibratory loads exerted on the cable are isolated from the connector terminals, shielding them against damage and/or disconnection.
The construction is particularly advantageous in that the benefits of a pinch-roll type strain relief are obtained in a construction which is readily adapted for use in molded connectors. This is accomplished without either unduly multiplying the numbers 'of connector parts, or complicating connector assembly operations. The construction also lends itself to use in other similar applications such as in the making of flat cable connections to printed circuit boards.
BRIEF DESCRIPTION OF THE DRAWINGS A fuller understanding of the nature and objects of the invention may be obtained through reference to the following detailed description, taken in connection with the accompanying drawings, in which:
FIG. 1 is an exploded perspective view, partially in section, of the strain relief construction of the invention as employed on a ribbon cable plug connector.
FIG. 2 is a top plan view, partially broken away, of the plug connector of FIG. 1 showing it in assembled condition.
FIG. 3 is an enlarged partial side sectional view of the strain relief construction of the invention.
FIG. 4 is a sectional view taken along line 4-4 of FIG. 2.
FIG. 5 is an exploded perspective view, partially in section, of the strain relief construction as used on a receptacle connector.
Similar reference characters refer to similar parts throughout the several views of the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I, the strain relief construction of the invention is shown as used on a flat cable plug connector 10. Plug connector 10 comprises a contactcarrying member I2 preferably molded as an integral unit from an electrical insulating material such as a thermoplastic. A cable-confronting face 14 which is substantially S-shaped in cross section (FIG. 3) is provided along the lower back edge 12a of member 12. Specifically, confronting face 14 comprises an indented portion Ma and an overhanging ledge I412 which together give the face its S-shaped configuration in cross section. This S-shaped face 14 of member 12 forms one part of the strain relief construction as is more fully described hereinafter.
As shown in FIGS. I and 2, member 12 further comprises a plurality of narrow, axially extending channels 16. Channels 16 are molded therein for receipt of the electrically conductive contact elements, which in this case are terminal pins 18 which are secured to and make contact with the conductors on the cable 20. As shown in FIG. 1, channels 16 also cut through the overhanging ledge 14b of S-shaped face 14; this makes ledge 14b somewhat flexible so that a spring-lock can be effected on the cable 20 when the plug connector is assembled. The front end of member 12 is also channeled lengthwise (FIGS. 1 and 2) to provide a protected enclosure 22 for the free ends 18a of pins 18 which project through apertures 24 from channels 16. Enclosure 22 may also serve as a female coupling for connecting member 12 with the projecting front edge 25a of a receptacle connector 25 of the type shown in FIG. 5.
Member 12 is also preferably provided with a pair of locking receptacles 26 and 28 integrally molded into each lateral edge thereof as shown in FIGS. 1 and 2. Each locking receptacle 26 and 28 is further provided with a detent ledge 26a and 28a at a point along the length thereof. The function of the detent ledges 26a and 28a will be discussed in greater detail hereinafter.
Referring back to FIG. I, an insert member 30 mates with contact-carrying member 12 to complete the plug connector and its strain relief construction. Insert member 30 is preferably similarly molded as an integral unit from electrical insulating material such as a thermoplastic. As shown in FIGS. 1 and 3, insert member 30 is provided on its front face 32 with a configuration that is substantially S-shaped in cross section and is substantially the mirror image of and complementary to face 14 of member 12. Specifically, S-shaped face 32 comprises a projection 32a (FIG. 3) which substantially corresponds in shape to indented portion 14a on face 14 of member 12, and an indented portion 32b which substantially corresponds in shape to ledge 14b of face 14. The size of these complementary surfaces however differ somewhat to allow for the incorporation therebetween of a predetermined thickness of ribbon cable 20. Overlying S-shaped face 32 is a projecting locating ledge 34 which is preferably provided with a tapered surface 34a to facilitate its insertion into plug connector 12 as shown in FIG. 3.
The lower surface 36 of insert member 30 is preferably slotted as shown at 38 in FIG. 4 so that the trailing edge of the cable may be conveniently held against that lower surface and directed axially of the connector.
Insert member is further provided with a pair of forward projecting locking arms and 42 along the lateral edges thereof, as shown in FIGS. 1 and 2. Locking arms 40 and 42 are each respectively provided with an enlarged head 40a and 42a forming detent ledges 40b and 42b. As shown in FIG. 2, when insert member 30 is assembled with member 12, the locking arms 40 and 42 are received within locking receptacles 26 and 28 respectively until the mating detent ledges 26a and 40b, and 28a and 42b, engage to form a mechanical interlock. The somewhat flexible nature of locking arms 40 and 42 permit them to be readily inserted into the locking receptacles 26 and 28 in the manner just described. It will also be seen that once engaged, the locking extensions 40 and 42 may be readily disengaged by inserting an appropriate tool into the opposite end of each receptacle 26 and 28 and bringing the tool to bear axially against the beveled surfaces 40c and 420 of each head 40a and 420. By application of axial force to surfaces 40c and 420, the flexible arms 40 and 42 may be bent sufficiently inward to disengage their respective detent surfaces.
The method of assembling contact-carrying member 12 with insert member 30 may be seen by reference to FIGS. 1, 3 and 4. A length of flat cable 20 is first threaded through the slot 38 along the bottom of insert member 30, and a portion extended over S-shaped face 32. A plurality of terminal pins 18 may then be placed on the cable and secured in a known manner in electrical contact with the cable conductors. This assembly is then mounted to member 12 by first inserting the terminal pins 18 into their respective channels 16 until the free ends 18a thereof project through apertures 24 into area 22. Insert member 30 may then be connected with member 12 by inserting the locking arms 40 and 42 into their respective locking receptacles 26 and 28. As the two members 12 and 30 are brought together, it will be seen that the portion of cable 20 between the cableconfronting faces 14 and 32 is formed into a similar S- shaped curve as shown in FIG. 3. When fully inserted, detent ledges 40b and 42b engage the corresponding detent ledges 26a and 28 a on the locking arms to form a secure mechanical interlock, clamping that portion of cable 20 between the complementary surfaces 14 and 32. The flexible nature of overlying ledge 14d as discussed hereinabove further serves to spring-lock the cable portion in place between the two members. The terminal pins 18 are thus shielded bythe clamped portion of cable against damage from tensile and vibratory loads imposed on the cable.
While the strain relief construction has been described in conjunction with a plug connector assembly for flat ribbon cable, it is not to be limited to such application. A strain relief construction in accordance with the invention may equally as well be applied, for example, to a cable receptacle connector 25 as shown in FIG. 5. Receptacle connector 25 is substantially identical to plug connector 10 except that terminal receptacles 44 are used rather than the terminal pins described hereinabove. In addition, receptacle connector 25 has an extended front edge 25a having apertures 46 therein for receipt of mating terminal pins. Front edge 25a is thus constructed to mate with enclosure area 22 of member 12 and receive the free ends 18a of the terminal pins thereof. The strain relief construction of the invention may similarly be applied in other applications such as where ribbon cable is being connected to printed circuit boards.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the construction set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.
Having described our invention, what we claim as I new and desire to secure by letters Patent is:
1. A strain relief assembly for flat cable or the like comprising, in combination;
a. a first insert member having a cable confronting first face thereon which is substantially S-shaped in cross section,
b. a second contact-carrying electrical connector member having a cable confronting second face of substantially S-shaped configuration in cross section 1, a substantial mirror image of and complimentary to said first face and c. means for connecting said first and second members together with said first and second faces and engaged in complimentary fashion for a portion of the flat cable formed into a similar S-shaped curve and clamped therebetween including a pair of locking arms projecting from one said member and a pair of locking receptacles on the other said member in position to receive and engage said locking arm; wherein a portion of the S-shaped face on said electrical connector member is cut through by a plurality of channels for receipt of terminal members, said channels serving to make said connector position flexible whereby the flat cable is springlocked in place upon assembly of said first and second members.