Patent Publication Number: US-2004043652-A1

Title: Initiator having integral features for orienting and holding an insertable electrical shunt

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to electrical initiators, and more particularly, to an initiator with an electrical connector that includes a body with integral features for orienting and securely holding a shunt, and for orienting a mating electrical connector.  
       [0002] An electrical initiator, such as is used in the automotive airbag industry, typically includes a shunt (or shorting) assembly that is secured within the initiator and in contact with the initiator&#39;s terminals, so as to prevent accidental actuation of the initiator prior to its engagement with a mating connector. Such a shunt assembly is typically a roughly cylindrical piece having a diameter substantially larger than the diameter of the portion of the mating connector that the assembly is designed to receive. The assembly typically includes a metallic shunt clip insert, and typically engages with the initiator&#39;s metal or plastic retainer so as to secure it in position in the initiator. When in place, the shunt assembly typically provides a surface(s) that is used to orient and secure the mating connector. Such shunt assemblies are described in U.S. Pat. Nos. 5,733,135, 6,213,800, and 6,257,910, the disclosures of which are hereby incorporated by reference herein.  
       [0003] The use of such assemblies, however, is subject to certain disadvantages. First, because the entire shunt assembly is inserted into the initiator body rather than made an integral part thereof, minimizing any undesired movement of its surface(s) used to orient and secure the mating connector (and thus degraded ability to mate and shunt reliably) requires tight tolerances and very secure methods of connection, both of which may increase manufacturing cost. Second, orientation features must be provided in both the initiator and the shunt assemblies so as to ensure proper alignment of the shunt clip with the electrical terminals of the initiator. Third, locking features must be provided in both the initiator and shunt assemblies so as to lock such shunt assemblies in place in the initiator. Fourth, the fact that such shunt assemblies are relatively large and comprise more than one part tends to exacerbate all of the foregoing issues. Fifth, producing a shunt assembly requires a separate, dedicated tool(s) and manufacturing step(s), such as an insert mold tool and molding step.  
       [0004] The prior art also includes initiator assemblies that eliminate a separate shunt assembly through the use of an integrated shunt, such as is described in U.S. Pat. Nos. 5,334,025 and 5,944,945. These arrangements, however, are for use with coaxial mating connectors and do not appear readily amenable to modification for use with commonly-used connectors such as the serviceable, non-serviceable, or universal connectors used in the automotive airbag industry. Moreover, because these connectors are coaxial, they do not appear to provide any orientation features and instead appear to permit the mating connector to rotate freely. Thus, it is believed that hitherto, problems such as those mentioned above have not been addressed by providing an initiator with a body having integral features for orienting and holding a shunt and for orienting a mating electrical connector.  
       SUMMARY OF THE INVENTION  
       [0005] An initiator according to the present invention includes a pair of electrical terminals for electrical contact with a mating electrical connector, and a shunt for establishing a short circuit between the electrical terminals when they are not in electrical contact with the mating connector. The initiator also includes integrally-formed means for orienting and securely holding the shunt in the initiator, and integrally-formed means for orienting the mating electrical connector with respect to the electrical terminals. The initiator may also optionally include means for securely holding the mating connector in place.  
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0006]FIG. 1 is a transverse perspective view, partially in section, of an embodiment of an initiator assembly according to the present invention.  
     [0007]FIG. 2 is a bottom plan view of the initiator assembly of FIG. 1.  
     [0008]FIG. 3 is a sectional view of the assembly of FIG. 1 (through the line indicated in FIG. 5) without the shunt inserted.  
     [0009]FIG. 4 is a sectional view taken through the line A-A of FIG. 2.  
     [0010]FIG. 5 is a sectional view taken through the line B-B of FIG. 2.  
     [0011]FIG. 6 is a sectional view taken through the line C-C of FIG. 2.  
     [0012]FIG. 7 is a front view of the shunt of the embodiment depicted in the foregoing drawings.  
     [0013]FIG. 8 is a side view of the shunt.  
     [0014]FIG. 9 is a sectional view similar to that of FIG. 4, but with the mating connector inserted.  
     [0015]FIG. 10 is a sectional view similar to that of FIG. 6, but with connector inserted.  
     [0016]FIG. 11 in an end view of the mating connector.  
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT  
     [0017] The depicted preferred embodiment of the present invention is designed for use with an air bag inflator for discharging inflation fluid to inflate an air bag to protect an occupant of a vehicle when the vehicle is involved in a collision. The present invention is likewise applicable, however, to any other suitable application involving an electrical initiator having a connector that requires a shunt when not in use.  
     [0018] Referring to FIG. 1, an initiator assembly  34  includes an outer can  36  surrounding an igniter  38  and a molded body  42 . The igniter  38  includes a charge can  28  enclosing a suitable pyrotechnic charge(s) and header assembly including an igniter wire (not shown) as is well-known in the art, and electrical terminals in the form of cylindrical metal pins  22  (the upper pin in FIG. 1 is partially cutaway to enhance the illustration). The pins  22  are electrically connected to the igniter wire, and, when the initiator assembly  34  is installed in the vehicle and connected with the vehicle&#39;s mating connector  72  as described below, the pins  22  are electrically connected with the mating connector  72 . The mating connector  72  (see FIG. 9) is in turn connected to vehicle electric circuitry (not shown), including a sensor such as an accelerometer, for receiving an electrical signal to ignite the igniter wire of the igniter  38 . The mating connector  72  is a commercially available part and is typically supplied by the manufacturer of the vehicle in which the initiator assembly  34  is mounted.  
     [0019] In addition to the igniter  38 , the initiator assembly  34  includes a retainer  40  for securing the igniter to the housing of the inflator (not shown). The retainer  40  is preferably made of a metal suitable for cold forming, such as 304L stainless steel. A body  42  of plastic material encases and is in intimate contact with the retainer  40  and the igniter  38 , thus attaching the retainer  40  to the igniter  38 . The pins  22  of the igniter  38  extend axially out through the body  42  into the connector opening  46  of the initiator assembly  34 . The body  42  is preferably injection molded, preferably at low pressures and temperatures, with one suitable material being nylon 6/6 with a 33% glass fill (e.g., ZYTEL®, from E. I. DuPont de Nemours &amp; Co.). It will of course be recognized that various other materials could also be chosen that could be suitably injection molded at low pressures and temperatures, suitably adhere to the retainer  40  and to the igniter  38 , and have suitably strength and durability to form the structures described below (e.g., the post  44 ). Alternatively, the body  42  could be an epoxy adhesive, or another material that is not injection molded.  
     [0020] To secure the igniter  38  to the retainer  40 , the igniter and the retainer are positioned relative to each other in a die (not shown), with the igniter&#39;s pins  22  extending through the central aperture of the retainer  40 . The plastic material of the body  42  in a molten form is then injected into the die where it adheres to the retainer  40 , the igniter  38  and the pins  22 .  
     [0021] Referring now also to FIGS.  2 - 5 , it will be seen that the connector opening  46  of the initiator assembly  34  is formed to include features for properly orienting the mating connector  72  and for receiving and holding in proper orientation the shunt  26  (which is described further below particularly with reference to FIGS. 7 and 8). These orientation features assure proper pin-to-connector polarity (ground/isolated) and prevent the mating connector from being installed backwards. Specifically, as can be seen from FIGS. 2, 3, and  5 , an orientation channel  58  defined in the body  42  extends uniformly up from the bottom surface of the connector opening  46 . On the opposite side of the pins  22 , a post  44  formed in the body  42  also extends uniformly up from the bottom surface of the connector opening  46 . The post  44  includes an orientation ridge  47  that is generally “V”-shaped, with the “V” pointing toward the orientation channel  58 . As can best be seen from FIGS. 3 and 5, a ledge  50  extends uniformly up a short distance from the bottom surface of the connector opening  46 , and a central portion of the ledge  50  merges with the adjacent bottom portion of the post  44 . On the opposite side of this central portion of the ledge  50 , a barb channel  24  defined into the body  42  extends uniformly up from the plane of the ledge  50 . Along the remainder of the ledge  50  (i.e., the portions on either side of the central portion that is adjacent to the barb channel  24 ), a flat face  54  extends uniformly up from the ledge  50 . Although it is not shown in the drawings for the sake of simplicity, it is preferable to bevel the upwardly-facing edges of the features of the connector opening  46 , to the extent practical with the molding technique.  
     [0022] As described further below, the shunt  26  is simply inserted in the space  52  around the post  44 , and it is oriented and securely held by the post  44 , barb channel  24 , face  54 , and ledge  50 . Thus, the features for orienting and holding the shunt, and the features for orienting the mating connector, are all formed during the same step as the forming of the initiator body, eliminating at least one separate part and corresponding manufacturing step. Moreover, the resulting monolithic structure is less prone to undesirable movement of non-integral parts that could reduce the ease and/or reliability of obtaining proper shunting and/or connection with the mating connector.  
     [0023] Referring now also to FIG. 6, it can be seen that the connector opening  46  of the initiator assembly  34  also preferably includes means for maintaining the mating connector  72  in electrical contact with the pins  22 , such as windows  43  that may be formed in the body  42  as is well-known in the art to accept the locking wings of a standard mating connector as described below. Consequently, a further reduction of parts and manufacturing steps is realized, since the formation of the mating connector locking features also occurs as part of forming the initiator body  42  and the other orientation and holding features that are provided in the connector opening  46  as described above.  
     [0024] Referring now also to FIGS. 7 and 8, the shunt  26 , which prevents accidental actuation of the igniter  38  prior to engagement of the mating connector  72  with the initiator assembly  34 , is shown in more detail. The shunt  26  comprises (preferably substantially or wholly) an electrically conductive material, preferably a metal or metal alloy (preferably solid, clad, or plated) having suitable corrosion resistance, flexibility, and durability. In the depicted preferred embodiment, the shunt  26  may be stamped out of a blank of solid 0.007″ inch thick beryllium copper, so as to form legs  62 , flares  67 , and an abutment  61 . Then, the still-flat piece may be further stamped to remove a “U”-shaped cutout  66  and form a barb  60  that extends at an angle (approximately 20°) away from the plane of the rest of the piece. As can be seen, the barb  60  terminates in a small end-portion that is bent so as to lie in a plane substantially parallel to the plane of the rest of the piece. After these stamping steps are completed, the shunt can then be formed into its final shape by forming the bends  65 , inflections  68 , and feet  70  into the legs  62 , using a stamping die. As can be seen, forming the bends  65  in the legs  62  serves to define a post opening  64  at the top of the shunt  26 .  
     [0025] The shunt  26  is then inserted into the connector opening  46  of the initiator assembly  34 , so that its post opening  64  slides over and around the top of the post  44 , and its legs  62  enter space  52 . The shunt  26  is thus slid down along the face  54  of the body  42 , with its barb  60  traveling down the barb channel  24  and its flares  67  in sliding contact with opposing portions of the body  42 , until its abutment  61  reaches the ledge  50  formed in the body  42 . The distance between the face  54  and the opposing portion of the post  44  is preferably selected to be slightly less than width of the barbed portion of the shunt  26 , so that while the shunt is being slid into place, the barb  60  is under slight compression. This further ensures that once the abutment  61  reaches the ledge  50 , the shunt  26  is securely locked in position with the barb  60  impinging against the face  54  and resisting upward movement with respect to the face  54 . Thus, the shunt  26  is precluded from any substantial downward movement by the contact of the abutment  61  with the ledge  50 , it is precluded from any substantial upward movement by the contact of the barb  60  against the face  54 , it is precluded from any substantial lateral movement in a plane parallel with the face  54  by the contact between the flares  67  and the body  42  and the proximity of the legs  62  to the post  44 , and, finally, the portion of the shunt  26  between the post  44  and the barb channel  24  and the face  54  is precluded from any substantial inward or outward movement by its contact with the post  44  and the barb channel  24  and the face  54 . Substantial rotation in any direction of the shunt  26  (except for pivoting in space  52  of the legs  62  at their bends  65  as described below) is also substantially resisted by the foregoing contacts.  
     [0026] The dimensions of the bends  65 , inflections  68 , and feet  70  of the shunt  26  are also selected so that the overall width of the shunt  26  (not counting its barb  60 ) is slightly greater than the distance between the face  54  and the opposing portions of the pins  22 , so that in order to insert the shunt  26  into the connector opening  46  as described above, its feet  70  must first be compressed inwardly a slight amount (e.g., a millimeter or so) so that they can pass by the pins  22  and the shunt  26  can fit between the face  54  and the pins  22  as shown in FIG. 2. This results in a degree of compression of the legs  62  when the shunt  26  is locked in place, which in turn ensures that the feet  70  reliably contact and electrically connect the corresponding pins  22  of the igniter  38 . This connection establishes a short circuit between the pins  22  of the igniter  38  (when the mating connector  72  is not in electrical contact with the terminals) that does not extend through the bridgewire of the igniter  38 , so that any stray electrical current that might be applied across the pins  22  of the igniter  38  does not result in actuation of the igniter.  
     [0027] Finally, the length of the legs  62  is selected so that when the shunt  26  is inserted in place as described above, as shown in FIGS. 4 and 5, the feet  70  are slightly above (e.g., a few millimeters or so) the bottom surface of the connector opening  46 . Thus, when the mating connector  72  is inserted, the feet  70  have room to pivot within space  52 , downwardly and out of contact with the pins  22  as described below.  
     [0028] Referring now also to FIG. 9, when the initiator assembly  34  is installed with an airbag inflator in the vehicle, it is electrically connected to the vehicle electric circuitry by the mating connector  72 . The mating connector  72  has a projecting portion made of an electrically insulating body  74  such as molded nylon, with contacts  76  encased in the projecting portion. The contacts  76  are connected by crimps  80  to lead wires  78  that extend away from the mating connector  72  and are connectable to vehicle circuitry, including the sensor, for generating an actuating signal for the igniter  38 . The external configuration of the projecting portion of the mating connector  72  is adapted to mate in a particular orientation with the features of the connector opening  46 , including the pins  22 , post  44 , orientation channel  58 , and bottom surface of the connector opening  46 . As can also be seen from FIGS. 10 and 11, the projecting portion of the mating connector  72  fits into the connector opening  46  of the initiator assembly  34 , with a groove  82  on its front surface formed to mate with the orientation ridge  47  of the post  44 , and with a bar  87  formed on its opposing surface to mate with the orientation channel  58 .  
     [0029] Thus, when the mating connector  72  is aligned with its groove  82  and bar  87  in proper orientation with the orientation ridge  47  and orientation channel  58 , respectively, the pins  22  of the igniter  38  are in proper alignment to be received in the contacts  76  of the mating connector  72  and establish electrical contact between the igniter  38  and the vehicle electric circuitry. Once the mating connector  72  is substantially inserted into the connector opening  46 , its projecting portion makes contact with the inflections  68  of the shunt  26  and pushes the shunt&#39;s feet  70  away from the pins  22 , disconnecting the short circuit established by the shunt  26 . In this regard, the projecting portion is also preferably configured to enhance its engagement and accommodation of the shunt  26 . Thus, a recess  75  is preferably provided at the end of the projecting portion, so that when the projecting portion is fully inserted into and reaches the bottom surface of the connector opening  46 , there is a space between the projecting portion and the connector opening&#39;s bottom surface to accommodate the feet  70  of the shunt  26 . Also, the part of the projecting portion that first makes contact with the inflections  68  of the shunt  26  is preferably beveled so as to make the engagement smoother.  
     [0030] The projecting portion of the mating connector  72  also preferably includes a pair of opposing wings  84  with locking tabs  86  (see FIG. 10) that are adapted to engage with the windows  43  of the body  42  and to securely interlock the mating connector  72  to the initiator assembly  34 . With the projecting portion of the mating connector  72  disposed in the connector opening  46 , the locking tabs  86  are received and engaged in the windows  43  (see FIG. 6) thus blocking movement of the mating connector  72  axially outwardly of the initiator assembly  34 , that is, in a direction away from the igniter  38 . This interlocking engagement maintains the mating connector  72  in electrical contact with the pins  22  of the igniter  38 .  
     [0031] A preferred embodiment of an initiator with a body having integral features for orienting and holding a shunt, and having integral features for orienting a mating electrical connector, has thus been disclosed. It will be apparent, however, that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. Therefore, the invention is not to be restricted or limited except in accordance with the following claims.