Patent Publication Number: US-9843132-B2

Title: Cable strain relief

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §371 of published PCT Patent Application Number PCT/EP 2015/063227, filed 12 Jun. 2015, claiming priority to European patent application number EP14172422.9 filed on 13 Jun. 2014, the entire contents of which is hereby incorporated by reference herein. 
     TECHNICAL FIELD OF INVENTION 
     The invention relates to an electrical connector system with a cable strain relief member. 
     BACKGROUND OF INVENTION 
     It is known that electrical connector systems are used to connect various cables, such as telecommunication cables, networking cables, other signaling cables or in general any electrical wiring, for example. Electrical connector systems are used for joining electrical circuits, wherein typically a male-ended plug is designed to connect to a female-ended jack. In many applications the safe coupling of connectors is of high importance. For example, in the case of car safety systems, e.g. airbag systems in passenger cars, the connectors used for the connection of an airbag to its ignition base have to be provided with reliable safety systems. To ensure that the connectors cannot become loose unintentionally, secondary locking systems may be used to guarantee the safe mechanical coupling. Often, such secondary locking systems are realized in the form of separate plastic components, which may be installed on one of the connectors which are to be secured, or are directly molded on the connector. 
     Additionally, in many fields of applications, electrical connector systems require cable strain relief members which firmly attach the cables to the connector systems in order to relieve the actual connection portion of the cable from possible strains. This connection portion, where the cable is dismantled and the cable wiring may be connected to a contact terminal, can be particularly fragile and therefore has to be protected. Cable strain relief members are known in the art to relieve electrical connector systems from strains applied to a cable. Normally, any forces applied to a cable directly act on the crimp area, i.e. the interconnection where the cable is connected to a contact terminal. These terminals of electrical connectors are usually very small components, such as components that are stamped and/or formed from thin sheet metal material and easily damaged or destroyed by the strain. 
     An improper seating of a contact terminal in a connector housing may occur if the terminal is not fully inserted therein during the initial assembly of the electrical connector system or if the contact terminal is vibrated or pulled out of its fully seated condition during use of the connector system. Failures of this type are a particular concern in the automotive industry where electrical components are subjected to vibration almost continuously during normal usage. It is therefore known in the art to provide a terminal position assurance (TPA) device for electrical connectors to detect incomplete insertion of contact terminals into the connector housings. TPAs also assure that the contact terminal is properly positioned in the respective housing. 
     SUMMARY OF THE INVENTION 
     Described herein is an electrical connector system that reduces the strain on the crimping area and also on the primary and/or secondary lock of connector systems. It is in particular an object of the present invention to provide an electrical connector system which comprises a minimal number of components and is simple to be mounted. It is a further object to provide an electrical connector system which features terminal position assurance (TPA). 
     In accordance with one embodiment, an electrical connector system is provided. The connector system comprises a contact terminal, and a corresponding connector housing. The contact terminal thereby may comprise an insulation crimp and a wire crimp to connect to a cable, and may provide an electrical interface for a corresponding counter connector. The connector housing defines an aperture which is designed to receive the contact terminal therein. The housing itself may in generally have any shape designed to connect to the corresponding counter connector. The connector housing may include a feature for locking the housing to the corresponding counter connector. The electrical connector system further comprises a cable strain relief member separate from the connector housing. Accordingly, the cable strain relief member is not an integral part of the connector housing. The cable strain relief member comprises cable fastening feature for fastening the cable strain relief member to a cable for strain relief. Furthermore, the cable strain relief member comprises an integrated locking feature that locks the member directly to a corresponding counter connector. 
     The term “counter connector” used herein denotes to any kind of connector designed to connect to the connector housing and contact terminal provided therein. The counter connector may have a suitable feature for fixing it to its environment, such as to a wall of an electrical component, and may provide a respective electrical feed-through there through. The counter connector may further be of any suitable shape, depending on the actual application and design of the connector housing. The counter connector, the connector housing, and the cable strain relief member are preferably fabricated by injection molding. 
     The cable strain relief member is a single, separate, member and is designed to transfer any cable strain directly to the corresponding counter connector. In other words, any pull-out forces applied to the cable are transferred via the cable strain relief member to the counter connector, and not to the connector housing. Accordingly, the crimp area of the terminal arranged in the connector housing has to withstand less force due to the fact that the cable strain relief member transfers the force to the counter connector. Advantageously, the present system also relieves any primary locking feature of the connector housing to the counter connector, and it is applicable in connector systems where the connector housing cannot be provided with an integrated primary lock, due to space limitations, for example. 
     Similarly, the primary and/or secondary lock connecting the contact terminal to the connector housing has to withstand less pull-out force because the cable strain relief member transfers the pull-out force to the corresponding counter connector. Thereby, the pull-out force is advantageously not completely acting on the crimp area and the primary and/or secondary lock of the contact terminal. Thereby the life time of the electrical connector system is prolonged. 
     The term “pull-out force” used herein denotes to any force that is acted so as to pull out a wire or cable from an electrical connector system. Analogously, the term “push-in force” used herein denotes to any force that is acted so as to push in a wire or cable into an electrical connector system. 
     In another embodiment, the cable strain relief member further comprises a mounting feature for mounting the member to the connector housing. This mounting feature is preferably a hook that envelopes a section of the connector housing when the cable strain relief member is mounted thereto. In one embodiment, this hook has preferably a U-shaped cross-sectional profile. 
     This mounting feature allows for a simple assembly process and advantageously fixes the cable strain member to the connector housing, thereby improving stability of the electrical connector system. 
     The terms “fastening”, “locking”, “mounting” and such used herein in connection with different features do not imply a particular application or method, but are merely used to label the different features for clarification. Accordingly, mounting feature may generally provide locking functions, for example, and locking feature may be used for mounting. 
     Preferably, the mounting features are designed to provide terminal position assurance (TPA) when the contact terminal is provided in the at least one aperture of the connector housing and the cable strain relief member is mounted to the connector housing. TPA is known in the art to assure correct positioning of the contact terminal inside the connector housing, thereby reducing the need for time-consuming and costly inspection during assembly. 
     Preferably, the mounting feature for mounting the cable strain relief member to the connector housing provide a lock for the contact terminal to secure the contact terminal in its position in the aperture of the connector housing. The mounting feature may thereby function as a primary lock or as a secondary lock for the contact terminal. Preferably, the mounting feature includes a portion which extends into the connector housing when the cable strain relief member is mounted thereto. This portion is thereby designed to prevent removal of the contact terminal from the aperture of the connector housing. In other words, the portion locks the aperture of the connector housing such that the contact terminal cannot be removed therefrom. 
     In yet another embodiment, the cable strain relief member is designed to releasable lock the connector housing to the corresponding counter connector. In other words, the cable strain relief member enables locking and removing the connector housing to and from the counter connector. Preferably, the cable strain relief member comprises an integrated flexible web which is supporting the integrated locking feature designed for locking the strain relief member directly to the corresponding counter connector. A flexible web may be of any form designed to provide a restoring force when an external force is applied thereto. Accordingly, the integrated locking feature may be provided on the flexible web such that the integrated locking feature is shifted or repositioned when a force is applied to the web. Thereby, the flexible web is designed to release the integrated locking feature from the corresponding connector when an external force is applied to the flexible web. Preferably, the integrated flexible web includes an actuating member. Accordingly, the connector housing with the cable strain relief member can easily be inserted and removed to the corresponding counter connector by applying force to the flexible web thereby interacting with the integrated locking feature such that the insertion or removal is not locked or blocked. 
     The actuating member may preferably be actuated by an operator for unlocking the strain relief member from the counter connector. Preferably the actuating member may be actuated by a suitable tool, such as a screw driver, for example. The actuating member is preferably formed such that it may readily be actuated with such a tool, without damaging the actuating member or the strain relief member. Preferably the strain relief member is designed such that its locking function may only be released when applying large external forces thereto. Thus, a resilient connection between the connector housing and the counter connector may be achieved, which cannot be released accidentally. 
     Preferably the actuating member of the strain relief member is located outside the counter connector when the strain relief member is locked thereto. Accordingly, the actuating member is not encased by the counter connector such that it may be accessible by an operator for releasing the locking function as described and for removing the connector housing from the counter connector. Hence the releasing of the connector housing from the counter connector may be done in a straightforward manner. 
     Preferably, the integrated locking feature is a locking ramp, which is designed to engage a corresponding locking window in a mating part of the corresponding counter connector. In another preferred embodiment, the integrated locking feature of the cable strain relief member is a locking window and the mating part of the corresponding counter connector is preferably a locking ramp. The locking ramp is in both cases designed to lower the flexible web of cable strain relief member when the connector housing with mounted cable strain relief member is inserted into the corresponding counter connector during assembly of the electrical connector system. Once inserted, the locking ramp face, which defines a force normal to the direction of insertion, provides the locking function. Accordingly, the interplay of a locking ramp and a corresponding locking window allows for an easy assembly of the electrical connector system. 
     Also the integrated locking feature may preferably be actuated by an operator for unlocking the strain relief member from the counter connector, for example by use of a suitable tool, such as a screw driver, for example. Preferably the strain relief member is designed to be unlocked from the counter connector when an external force is applied to the integrated locking feature of the strain relief member. Preferably, the external force is thereby applied in a mating direction of the connector system, i.e. the direction of insertion or removal of the connector housing to or from the counter connector. Preferably, the integrated locking feature may be accessed from outside the counter connector through a respective opening provided therein, wherein such an opening is preferably provided in the mating direction of the connector system. Thereby the locking function can be released from the opposite side of insertion or removal, i.e. from “inside” the connector housing, as the integrated locking feature is reachable from inside the counter connector, even though the connector housing is arranged in the counter connector. 
     In yet another embodiment of the present invention, the contact terminal comprises primary locking feature, which is designed to lock the contact terminal in the aperture of the connector housing. Preferably, the primary locking feature is a latching lance which enables easy insertion of the contact terminal into the connector housing and lock the contact terminal therein. Preferably, the connector housing may also comprise a locking feature, which is designed to provide a primary lock for the connector housing to the corresponding counter connector. 
     In yet another embodiment, the cable strain relief member comprises a spacer which separates the cable from the connector housing when the system is fully mounted, i.e. when the cable is connected to the contact terminal, which in turn is inserted into the aperture of the connector housing, and the cable strain relief member is fastened to the cable. The spacer, provided between the cable and the connector housing, advantageously protects the crimping area when, for example, the cable is forced or pushed further into the connector housing. The spacer preferably comprises two surfaces, wherein a first surface is in contact with the connector housing while a second surface is in contact with a cable sheeting of the cable. Hence, when the cable is pushed, the force is preferably transferred via the spacer to the connector housing, thereby advantageously reducing strain on the crimp area. 
     The system may preferably further comprise a corresponding counter connector which may be any connector that is compatible with the connector housing a contact terminal positioned therein, and a cable strain relief member mounted to the connector housing. Preferably, the corresponding counter connector is designed to interact with the integrated locking feature of the cable strain relief member to provide cable strain relief. Preferably, the counter connector comprises an opening enabling to apply an external force in mating direction of the connector system to the strain relief member, and in particular to the integrated locking feature of the strain relief member, for unlocking the strain relief member from the counter connector. The opening may be provided on the counter connector in mating direction of the connector system and is preferably separate from the aperture of the counter connector and may be provided on an opposing side of the counter connector with respect to said aperture. Accordingly, the locking function can easily be released by inserting a screw driver through the opening and by applying a respective force to the strain relief member with the screw driver. Preferably the connector housing and/or the counter connector include a respective groove or path allowing for guiding a respective tool for applying said force in mating direction to the strain relief member for unlocking the locking function. 
     Preferably the connector housing comprises a rib designed to interact with the counter connector for preventing a further insertion of the connector housing into the counter connector when the strain relief member is locked to the counter connector. Preferably the aperture of the counter connector is step-like shaped, wherein a first step of the step-like shaped aperture is designed to interact with such a rib of the connector housing for preventing a further insertion as described. Accordingly, when the connector housing is inserted into the aperture of the counter connector far enough, such that the integrated locking feature of the strain relief member are locking the member to the counter connector, the rib comes into blocking contact with the first step of the step-like shaped aperture such that further insertion forces, or push-in forces are transferred via said blocking contact to the counter connector. Hence the contact terminal is protected. 
     Further, the system may preferably comprise a cable mounted to the contact terminal, wherein the mounting may comprise any means known to one skilled in the art to attach the cable to the contact terminal. For example, an insulation crimp to connect the contact terminal to an insulation of the cable and a wire crimp to connect the contact terminal to a wiring of the cable may be utilized for connecting the cable to the contact terminal. The cable may include one or more wires and the insulation may be any insulation known by the skilled person. 
     Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiments, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic illustration of an electrical connector system in accordance with one embodiment; 
         FIG. 2  shows a three-dimensional cross-section of  FIG. 1  in accordance with one embodiment; 
         FIG. 3  is a schematic illustration of a cable strain relief member in accordance with one embodiment; 
         FIG. 4  shows the cable strain relief member of  FIG. 3  from a different perspective in accordance with one embodiment; 
         FIG. 5  is a schematic illustration of an electrical connector system in accordance with one embodiment; and 
         FIG. 6  shows a three-dimensional cross-section of  FIG. 5  in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective view of an electrical connector system in accordance with the invention. In  FIG. 2 , the electrical connector system of  FIG. 1  is shown in a three-dimensional cross-section. As one can see in  FIGS. 1 and 2 , the illustrated electrical connector system comprises a connector housing  20 , which in turn comprises at least one aperture designed to receive a contact terminal  40  therein. The contact terminal  40  may comprise an insulation crimp and a wire crimp for mounting a cable  30  to the contact terminal  40 . It will be appreciated that any suitable means may be utilized to mount the cable  30  to the contact terminal  40 . An interface  42  between the cable  30  and the contact terminal  40  is denoted as “crimping area” or “crimp area” herein. The contact terminal  40  further comprises a primary locking feature  41 , which provides a primary lock for the contact terminal  40  to secure the contact terminal  40  in its position in the aperture of the connector housing  20 . The primary locking feature  41  may further comprise a latching lance. While any means may be utilized to provide the primary locking function, the latching lance is preferable because, during assembly of the system, the latching lance latches with the connector housing  20  when the contact terminal  40  is fully inserted into the aperture of the connector housing  20 , thereby allowing for an easy assembly. 
     The electrical connector system further comprises a cable strain relief member  10  which is a separate component from the connector housing  20 . The cable strain relief member  10  comprises an integrated locking feature  12  which locks the cable strain relief member  10  directly to a corresponding counter connector  50  ( FIG. 5 ). As illustrated, the integrated locking feature  12  is preferably a locking ramp. The locking ramp includes an insertion ramp face, or ramp wedge, which faces into the direction of insertion during assembly of the system. The locking ramp further includes a locking ramp face perpendicular to the direction of insertion and faces into the opposed direction of insertion. However, the integrated locking feature  12  may also be of other shapes, such as a block-shape, for example. 
     The integrated locking feature  12  is supported by a flexible web  15  which in turn includes an actuating member  14 . The flexible web  15  is designed to release the integrated locking feature  12  from the corresponding counter connector  50  when an external force is applied to the flexible web  15 . Similarly, the flexible web  15  may be designed to allow for an easy insertion of the illustrated electrical connector system into a corresponding counter connector  50  when an external force is applied to the flexible web  15 . The cable strain relief member  10  further comprises a fastening feature  11  for fastening the cable strain relief member  10  to the cable  30  for strain relief. It will be appreciated that the fastening feature  11  is only sketched in the figures and that any means for fastening the cable strain relief member  10  to the cable  30  may be utilized. For example, the cable strain relief member  10  may be clamped, squeezed or glued to the cable  30 . Alternatively, a snap-lock system may be applied or a metal sleeve may be utilized for coupling the cable  30  to the cable strain relief member  10 , for example. The cable  30  in turn comprises a cable sheathing  31  and a wiring  32 . It will be appreciated that the wiring  32  may consist of one or more wires and that the present invention is not restricted to any particular sort or kind of cable sheathing  31 . 
     As can further be seen from  FIGS. 3 and 4 , the cable strain relief member  10  of  FIGS. 1 and 2  also comprises mounting features  13   a  and  13   b  for mounting the cable strain relief member  10  to the connector housing  20 . The mounting features  13   a  and  13   b  thereby allow for securing the position of the cable strain relief member  10  to the connector housing  20 . The mounting features  13   a  and  13   b  may be designed to fit into corresponding features, such as protrusions, apertures or clearances of the connector housing  20 . As illustrated, the mounting features  13   a  and  13   b  may comprise at least one hook designed to envelope a section of the connector housing  20 . Preferably, the mounting features  13   a  and  13   b  has a U-shaped cross sectional profile such that the mounting features  13   a  and  13   b  can envelope a section of the connector housing  20 . This allows for an easy fixation during the mounting of the cable strain relief member  10  to the connector housing  20  during assembly of the electrical connector system. 
     As can be seen from  FIG. 2 , the mounting feature  13   a  also provides terminal position assurance TPA. Accordingly, mounting the cable strain relief member  10  to the connector housing  20  indicates that the pre-inserted contact terminal  40  is in correct position inside the connector housing  20 , reducing the need for any costly and expensive inspection during assembly. 
     The mounting feature  13   a  may further provide a secondary lock for the contact terminal  40 . Accordingly, when the primary locking feature  41  of the contact terminal  40  fails, the secondary lock hinders the contact terminal  40  from dropping out of the connector housing  20 . As can be seen in  FIG. 1 , the mounting feature  13   a  includes a portion extending into the connector housing  20  which in turn blocks the aperture of the connector housing  20 . Preferably the contact terminal  40  is of such shape that it gets fixed in the blocked aperture of the connector housing  20  and cannot be removed when the cable strain relief member  10  is mounted to the connector housing  20 . 
     Accordingly, the mounting feature  13   a  of the electrical connector system of  FIGS. 1 and 2  provide three functions in one single piece, namely fixation of the cable strain relief member  10  to the connector housing  20  and thus a locking of the connector housing  20  to the counter connector  50 , a TPA functionality, and a secondary locking function for the contact terminal  40 . It will be appreciated that a single portion may comprise all these functions, or that separate portions of the cable strain relief member  10  may provide one or more of these functions separately. 
     The electrical connector system of  FIGS. 1 and 2  is designed to be locked to the corresponding counter connector  50  only by the integrated locking feature  12 , because the connector housing  20  shown does not in itself have any primary locking feature  41 . However, it will be appreciated that the connector housing  20  may itself include an integrated feature for locking the connector housing  20  to the counter connector  50 , as will be recognized by one skilled in the art, in which case the integrated locking feature  12  of the cable strain relief member  10  provides a secondary lock for the connector housing  20 . 
       FIGS. 5 and 6  show another electrical connector system, where the electrical connector system of  FIGS. 1 and 2  is connected to a corresponding counter connector  50 . The counter connector  50  may have any desired and suitable shape. A contact pin  60  of the counter connector  50  is in electrical contact with the contact terminal  40 , which provides electrical contact to the wiring  32  of the cable  30 . The counter connector  50  comprises a locking window  51  which is designed to receive the integrated locking feature  12  of the cable strain relief member  10 . It will be appreciated that the counter connector  50  may include the locking ramp and the cable strain relief member  10  include the locking window  51  designed to receive the locking ramp of the counter connector  50  instead. As can be seen from  FIG. 6  in detail, the cable strain relief member  10  provides strain relief for the crimp area  42  and the primary locking feature  41  of the contact terminal  40 . In particular, when a pull-out force is applied to the cable  30 , the pull-out force is transferred via the fastening feature  11  and integrated locking feature  12  of the cable strain relief member  10  directly to the corresponding counter connector  50 . Hence the crimp area  42  and the primary locking feature  41  of the contact terminal  40  have to withstand less pull-out force. 
     Further on, the cable strain relief member  10  includes a flexible web  15 , which supports the integrated locking feature  12  and includes the actuating member  14 . The flexible web  15  is formed to provide a restoring force perpendicular to the direction of insertion or removal of the connector housing  20  with mounted cable strain relief member  10  into or from the corresponding counter connector  50 , when a force is applied to the flexible web  15 . In general, an operator can insert or remove the connector housing  20  with mounted cable strain relief member  10  into the corresponding counter connector  50  by applying force to the flexible web  15  such that the flexible web  15  bows and the integrated locking feature  12  supported by the flexible web  15  is displaced. Preferably, as illustrated, the integrated locking feature  12  is a locking ramp. Accordingly, once the connector housing  20  with mounted cable strain relief member  10  is inserted into the corresponding counter connector  50 , the flexible web  15  bows as a result, such that the integrated locking feature  12  can access the corresponding locking window  51  in the counter connector  50  to provide the locking function. This allows for an easy assembly of the electrical connector system. 
     By pressing on the actuating member  14 , which is preferably located outside the counter connector  50  as illustrated in  FIG. 5 , an operator can unlock the integrated locking feature  12 . By applying a force to the flexible web  15 , the integrated locking feature  12  is displaced such that it is no longer in locking contact with the corresponding counter connector  50 . This allows for extracting the connector housing  20  with mounted cable strain relief member  10  from the corresponding counter connector  50  simply by applying a force on the flexible web  15  by pressing on the actuating member  14  and by pulling the cable  30 . Accordingly, the connector housing  20  with mounted cable strain relief member  10  can then be extracted from counter connector  50  in a non-destructive way. Again, the cable strain relief member  10  reduces the force acting on the crimp area  42 , by transferring the pull-out force during the disassembly via the fastening feature  11  and the mounting features  13   a  and  13   b  directly to the connector housing  20 . Thereby, the fragile crimping area is protected. 
     As illustrated in  FIG. 2  the cable strain relief member  10  further includes a spacer  16 . The spacer  16  is located between the cable sheathing  31  and the connector housing  20  and comprises two surfaces; A first surface  17   a  is in contact with the connector housing  20 , while a second surface  17   b  is in contact with the cable sheathing  31 . When pushing the cable  30  mounted to the contact terminal  40  provided in the connector housing  20  into the corresponding counter connector  50 , the push-in force is transferred via the spacer  16  directly to the connector housing  20 . Thereby, the push-in force acting on the crimp area  42  is reduced. Accordingly, the spacer  16  may reduce an overstraining of the crimping area during assembly of the electrical connector system. 
     Upon inserting the connector housing  20  and the mounted cable strain relief member  10  into the counter connector  50 , the integrated locking feature  12  interacts with the counter connector  50  such that the flexible web  15  is lowered. When the connector housing  20  with the mounted cable strain relief member  10  is fully inserted into the corresponding counter connector  50 , the locking ramp snaps into locking position, i.e. in the locking window  51  of the counter connector  50 , due to the restoring forces of the flexible web  15 . The actuating member  14  may be designed to prevent further insertion of the connector housing  20  with mounted cable strain relief member  10  into the counter connector  50 , thereby preventing an overstraining of the crimp area  42 . 
     According to one particular aspect of the present invention, the integrated locking feature  12  may be assessed from “inside” the counter connector  50 . With reference to  FIG. 6 , the a channel  61  (indicated by dashed lines) may be provided in the counter connector  50  that runs from the left hand side in the mating direction to the locking window  51 . The channel  61  would enable the insertion of a screw driver, or similar tool, from the left side of  FIG. 6 , to eventually urge the integrated locking feature  12  downwards for releasing the locking function. The ramp-like shape of the integrated locking feature  12  is hence particularly preferred in this respect, as it allows for flexing the flexible web  15  by actuating the integrated locking feature  12  in mating direction of the system. The channel  61  indicated in  FIG. 6  is only provided for illustrative purposes and may require a larger dimension to enable the insertion of a tool. This may be achieved by enlarging the respective wall thickness of the counter connector  50  in the portion comprising the channel  61 . 
     Accordingly, an electrical connector system that reduces the strain on the crimping area and also on the primary and/or secondary lock of connector systems is provided. The electrical connector system comprises a minimal number of components and is simple to be mounted and further includes terminal position assurance (TPA). 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.