Patent Publication Number: US-6213800-B1

Title: Shorting clip for air bag inflator

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an inflator for inflating a vehicle occupant protection device to help protect an occupant of a vehicle. In particular, the present invention relates to a shorting clip for an inflator having an electrically energizable initiator. 
     2. Description of the Prior Art 
     It is known to help protect a vehicle occupant by inflating an air bag with inflation fluid from an air bag inflator. The inflation fluid is released from a container in the inflator and/or generated by ignition of combustible gas generating material in the inflator. 
     The inflator may use an electrically actuatable initiator to open the container and/or to ignite the gas generating material. A typical initiator has two terminals. The terminals are in electrical contact with an electrical connector which is part of vehicle electric circuitry. To actuate the inflator, the vehicle electric circuitry sends an electric signal through the electrical connector and the terminals to the initiator. The electric signal actuates the initiator, resulting in actuation of the inflator. 
     It is desirable to provide an electrical short circuit between the terminals of the inflator prior to connection of an electrical connector with the terminals. The short circuit prevents inadvertent actuation of the initiator. U.S. Pat. No. 5,733,135 describes an inflator having a shorting clip that functions in this manner. 
     SUMMARY OF THE INVENTION 
     The present invention is a shorting clip for establishing a short circuit between first and second electrical terminals of an air bag inflator initiator. The shorting clip comprises a body of electrically insulating material having connector portions engageable with the initiator for connecting the shorting clip to the initiator. The body of electrically insulating material has first and second contact portions engageable with the first and second electrical terminals of the initiator when the shorting clip is connected to the initiator. The shorting clip also comprises an electrically conductive plating on each one of the contact portions for establishing electrical contact between the shorting clip and the first and second terminals of the initiator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following specification with reference to the accompanying drawings, in which: 
     FIG. 1 is a transverse sectional view of an inflator including an initiator assembly and a shorting clip constructed in accordance with the present invention, with the shorting clip in position in the initiator assembly; 
     FIG. 2 is an enlarged view of a portion of the initiator assembly of FIG.  1  and also showing a portion of an electrical connector in a condition prior to engagement with the initiator assembly; 
     FIG. 3 is a sectional view of a portion of the initiator assembly and the shorting clip in a condition prior to assembly into the initiator assembly; 
     FIG. 4 is a view similar to FIG. 3 showing the shorting clip and the electrical connector in position on the initiator assembly; and 
     FIG. 5 is a bottom plan view of the initiator assembly and shorting clip. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     The present invention relates to an inflator for inflating a vehicle occupant protection device to help protect an occupant of a vehicle. The present invention is applicable to various inflator constructions, including inflators of different shapes and sizes and inflators with different modes of operation. For example, the invention can be applied to inflators which release inflation fluid from a container and/or which generate inflation fluid by ignition of combustible gas generating material. 
     As representative of the present invention, FIG. 1 illustrates an inflator  10  for inflating an air bag indicated schematically at  12 . The inflating air bag  12  moves into the space between a driver of a vehicle and a vehicle steering wheel (not shown) to help protect the driver of the vehicle. 
     The inflator  10  (FIG. 2) includes a housing  20 . The housing  20  is made of three pieces, namely, a diffuser cup  22 , a combustion cup  24 , and a combustion chamber cover  26 . The diffuser cup  22  encloses the combustion cup  24  and has an annular array of gas outlet openings  28  formed in its upper portion. The combustion cup  24  has an annular array of openings  30  in its lower portion and is welded with continuous welds to the diffuser cup  22 . The combustion chamber cover  26  is a generally flat metal piece having a circular central opening  34 . The chamber cover  26  is welded with a continuous weld to the combustion cup  24  to close the combustion cup. 
     A hermetically sealed canister  40  is disposed in the combustion cup  24 . A plurality of annular disks  42  of gas generating material are stacked atop each other within the canister  40 . The disks  42  are made of a known material that, when ignited, generates nitrogen gas. Although many types of gas generating material could be used, suitable gas generating materials are disclosed in U.S. Pat. No. 3,895,098. An annular prefilter  44  is disposed in the canister  40 , radially outward of the gas generating disks  42 . A small recess in the center of the canister cover receives a packet  46  of auto ignition material. 
     An annular slag screen indicated schematically at  48  is located in the diffuser cup  22  radially outward of the openings  30  in the combustion cup  24 . An annular final filter assembly indicated schematically at  50  is located above the slag screen  48 . The final filter assembly  50  is radially inward of the gas outlet openings  28  in the diffuser cup  22 . 
     The inflator  10  includes an initiator assembly  60 . The initiator assembly  60  includes an igniter  62  which projects through the opening  34  in the chamber cover  26  into the canister  40 . The igniter  62  may be of any suitable well known construction and includes a resistance wire (not shown) embedded in a known ignition material (not shown) in the igniter. The igniter  62  has a pair of externally projecting terminals in the form of cylindrical metal pins  64  and  66 . The terminals  64  and  66  are connected to the resistance wire in the igniter  62 . 
     When the inflator  10  is mounted in the vehicle, the terminals  64  and  66  are electrically connected with an electrical connector  68  (FIGS. 2 and 4) in a manner described below. The electrical connector  68  is connected to vehicle electric circuitry (not shown), including a vehicle condition sensor, for receiving an electrical signal to actuate the igniter  62 . The electrical connector  68  is a commercially available part and is typically supplied by the manufacturer of the vehicle in which the inflator  10  is mounted, rather than by the manufacturer of the inflator. 
     In addition to the igniter  62 , the initiator assembly  60  includes a retainer  70  (FIGS. 2-4) for securing the igniter to the housing  20  of the inflator  10 . The retainer  70  is preferably made of a weldable metal suitable for cold heading, such as UNS S30430 stainless steel. 
     The retainer  70  includes a tubular, axially extending socket portion  72  and an annular, radially extending flange portion  74  at one end of the socket portion. The socket portion  72  has cylindrical outer and inner circumferential surfaces  78  and  76  centered on an axis  80  of the inflator  10 . The socket portion  72  and the flange portion  74  extend circumferentially around a central opening  82  of the retainer  72 . An interlock portion  84  of the retainer  70  extends axially inward (upward as viewed in FIG. 4) from the socket portion  72 . 
     The flange portion  74  of the retainer  70  has parallel, radially extending inner and outer side surfaces  86  and  88 . An annular outer edge surface  90  extends axially between the inner and outer side surfaces  86  and  88 . A circumferential recess or groove  94  is formed in the inner circumferential surface  76  of the retainer  70 , near the outer side surface  88  of the flange portion  74  of the retainer. 
     A body of plastic material  96  encases and is in intimate contact with the interlock portion  84  of the retainer  70  and with the igniter  62 . The terminals  64  and  66  of the igniter  62  extend axially from the body of plastic material  96  into the central opening  82  of the retainer  70 . The body of plastic material  96  attaches the retainer  70  to the igniter  62 . In the preferred embodiment, the body of plastic material  96  is injection molded nylon with a glass fill. Other materials which can be injection molded at low pressures and temperatures and which will adhere to the retainer  70  and to the igniter  62  are also suitable for use. Alternatively, the body of plastic material  96  could be an epoxy adhesive, or another material which is not injection molded. 
     After the igniter  62  is secured to the retainer  70  by the body of plastic material, the retainer is attached to the combustion chamber cover  26  (FIG.  2 ), preferably by welding along the outer edge surface  90 . The cover  26  is then welded to the combustion cup  24 . The igniter  62  is thereby secured in position in the inflator  10 . It should be noted that the retainer  70  can be secured to the cover  26  by other means. For example, it is contemplated that the retainer  70  and the cover  26  may have complementary threaded portions which permit the retainer and the cover to be screwed together. 
     The initiator assembly  60  includes a shorting clip  100  which prevents accidental actuation of the igniter  62  prior to engagement of the electrical connector  62  with the initiator assembly. The shorting clip  100  also maintains the electrical connector  68  in electrical contact with the electrical terminals  64  and  66  of the igniter  62  after engagement of the electrical connector with the initiator assembly  60 . 
     The shorting clip  100  is made from a single piece of injection molded plastic material  102  having a generally cylindrical configuration. A cylindrical outer side surface  104  of the shorting clip  100  extends parallel to the axis  80 . The shorting clip  100  has parallel, radially extending inner and outer end surfaces  106  and  108 . A plurality of beveled locking tabs  110  are formed on the outer side surface  104  of the shorting clip  100 , near the outer end surface  108 . 
     The shorting clip  100  has a central opening  120  with a configuration adapted to receive the electrical connector  68 . The central opening  120  of the shorting clip  100  is defined generally by a pair of arcuate, axially extending end surfaces  122  and  124  (FIG. 5) centered on and bowed outwardly from the axis  80 , and a pair of planar side surfaces  126  and  128  which extend parallel to the axis. A portion  130  of the central opening  120  projects radially outward from the planar side surface  128  to provide asymmetry to the central opening for orientation purposes. The shorting clip  100  also has a pair of connector locking recesses (not shown) extending outward from the central opening  120 . 
     The body of plastic material includes a pair of terminal contact portions in the form of shorting arms  140  and  142 . The shorting arms  140  and  142  project from the side surface  126  of the shorting clip  100  into the central opening  120 . The shorting arms  140  and  142  are made as one piece with the other plastic portions of the shorting clip  100 . The shorting arms  140  and  142  are resiliently movable relative to the remainder of the main body portion  102 . 
     The shorting clip  100  includes an electrically conductive plating  150 , such as copper or gold, on the body of electrically insulating material  102 . The electrically conductive plating  150  has a generally U-shaped configuration on the body of insulating material  102 , matching the configuration of the two shorting arms  140  and  142 , when viewed in elevation as in FIG. 3. A first portion  152  of the plating  150  is located on the first shorting arm  140 . A second portion  154  of the plating  150  is located on the second shorting arm  142 . A third or bridge portion  156  of the plating  150  extends between and electrically interconnects the first and second portions  152  and  154  of the plating. 
     The shorting clip  100  is inserted in the central opening  82  in the retainer  70 , shortly after the retainer is molded to the igniter  62 . The external configuration of the shorting clip  100  is adapted to fit closely within the internal configuration of the retainer  70 , that is, within the surfaces which define the central opening  82  in the retainer. When the shorting clip  100  is engaged with the retainer  82 , the outer side surface  104  on the shorting clip adjoins the cylindrical inner surface  76  on the retainer  70 . The locking tabs  110  on the shorting clip  100  engage in the groove  94  in the retainer  70 . A pair of locator tabs  160  on the shorting clip  100  engage in recesses  162  in the retainer  70  to assure proper rotational orientation of the shorting clip relative to the retainer. 
     When the shorting clip  100  is disposed in the central opening  82  in the retainer  70 , the electrical terminals  64  and  66  of the igniter  62  extend into the central opening  120  of the shorting clip. The first metal plating portion  152  on the first shorting arm  140  of the shorting clip  100  engages the first electrical terminal  64  of the igniter  62 . The second metal plating portion  154  on the second shorting arm  142  of the shorting clip  100  engages the second electrical terminal  66  of the igniter  62 . 
     As a result, the electrically conductive plating  150  on the shorting clip  100  connects the terminals  64  and  66  of the igniter  62  electrically. This connection establishes a short circuit between the electrical terminals  64  and  66  of the igniter  62 , when the electrical connector  68  is not in electrical contact with the terminals. The short circuit established by the shorting clip  100  does not extend through the bridgewire of the igniter  62 . Therefore, any stray electrical current which might be applied across the electrical terminals  64  and  66  of the igniter  62  does not result in actuation of the ignition material in the igniter, and thus does not cause actuation of the inflator  10 . 
     When the inflator  10  is thereafter mounted in the vehicle, the inflator is electrically connected to the vehicle electric circuitry by the electrical connector  68 . The electrical connector  68  has a projecting portion  170 , made of an electrically insulating material such as plastic. Two split cylindrical metal sleeves  172  and  174  are molded into the projecting portion  170  of the electrical connector  68 . The metal sleeves  172  and  174  connect to lead wires (not shown) which extend away from the electrical connector  68  and which are connectable to the vehicle electric circuitry for receiving an actuating signal for the igniter  62 . 
     The projecting portion  170  of the electrical connector  68  fits into the central opening  120  in the shorting clip  100 . The metal terminals  64  and  66  of the igniter  62  are received in the metal sleeves  172  and  174  of the electrical connector  68  to establish electrical contact between the igniter  62  and the vehicle electric circuitry. At the same time, the projecting portion  170  of the electrical connector  68  bends the shorting arms  140  and  142  of the shorting clip  100  away from the axis  80  to disconnect the short circuit established by the shorting clip. A pair of locking arms (not shown) on the electrical connector engage in the connector locking recesses in the shorting clip  100  to maintain the electrical connector  68  in electrical contact with the electrical terminals  64  and  66  of the igniter  62 . 
     Upon sensing of a vehicle condition for which inflation of the air bag  12  is desired for protection of a vehicle occupant, an electrical actuating signal is transmitted through the electrical connector  68  and through the terminals  64  and  66  to the igniter  62 . The igniter  62  is actuated and provides hot combustion products which flow outwardly from the igniter  62  and rupture an inner wall of the canister  40 . The hot combustion products from the igniter  62  ignite the disks  42  of gas generating material. The disks  42  of gas generating material rapidly produce a large volume of inflation fluid. 
     The pressure of the inflation fluid ruptures the outer side wall of the canister  40 . The inflation fluid then flows radially outwardly through the prefilter  44 , through the openings  30  and into the slag screen  48 . The inflation fluid flows axially upward from the slag screen  48  to the final filter assembly  50 . The gas then flows radially outwardly through the final filter assembly  50  and the gas outlet openings  28  into the air bag  12 . 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.