Abstract:
The present invention is a child seat detecting apparatus for detecting the presence of a child seat in a vehicle. The child seat detecting apparatus is a tension sensing device that is attached to a vehicle seat. The tension sensing device includes a bracket that is mounted to the vehicle seat. A moveable bar is retained by the bracket. The moveable bar is attached to the child seat. A sensor is mounted between the bracket and the moveable bar. The sensor is adapted to provide an electrical signal that is indicative of a magnitude of tension on the moveable bar. A spring is located between the bracket and the moveable bar. The spring biases the moveable bar away from the bracket.

Description:
This application claims benefit of provisional application Ser. No. 60/482,541 filed Jun. 25, 2003. 

   BACKGROUND 
   1. Field of the Invention 
   This invention relates to a child seat detecting apparatus, and more particularly to a tension sensing device for detecting a child seat mounted on a vehicle seat. 
   2. Description of the Related Art 
   Air bags have been heralded for their ability to reduce injuries and save lives. However, since their incorporation into automobiles, a problem has existed with airbags deploying when children are seated in a vehicle. In particular, young children in child seats are especially susceptible to injury during airbag deployment. Air bags are designed to cushion the impact of occupants and thus reduce the injuries suffered. However, the force needed to properly cushion an adult can cause injuries in children. 
   When a child seat is mounted on the passenger seat and an air bag deploys during a collision, the child seat is impacted by the air bag such that the child seated in the child seat receives the impact. It is desirable to have the airbag automatically switch off and not activate during a collision when a child seat is present. 
   Child seats are constructed so as to be secured to the vehicle seat. Newer vehicles use a pair of child seat latches or anchor bars to attach the child seat to the vehicle seat. The latches or anchor bars are mounted to the frame of the seat which in turn is bolted to the floor of the vehicle. The child seat is attached to the anchor bar by either a mini-belt and buckle or by a locking hook. Both of these attachment devices are tightened by the user during installation, such that they pull or place a tension on the anchor bar. The child seat is therefore cinched down to the vehicle seat by the mini-belt and buckle or by a locking hook. 
   A current unmet need exists for a sensor to detect the tension on a child seat anchor bar in order to determine the presence or absence of a child seat in a vehicle. 
   SUMMARY 
   It is a feature of the present invention to provide a child seat detecting apparatus. 
   Another feature of the invention is to provide a tension sensing device for attachment to a seat that includes a bracket that is adapted to be secured to the seat. A moveable bar is retained by the bracket. A sensor is mounted between the bracket and the moveable bar. The sensor is adapted to provide an electrical signal that is indicative of a magnitude of tension on the moveable bar. A spring is located between the bracket and the moveable bar. The spring biases the moveable bar away from the bracket. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective exploded view of the preferred embodiment of a tension sensing device. 
       FIG. 2  is an assembled view of  FIG. 1  showing the tension sensing device ready to mount to a seat member. 
       FIG. 3  is a perspective view of a seat showing the mounting of the tension sensing device. 
       FIG. 4  is a side cross sectional view of the tension sensing device of  FIG. 2  mounted to the seat member. 
       FIG. 5  is a side cross sectional view of the tension sensing device of  FIG. 2  mounted in a seat. 
   

   It is noted that the drawings of the invention are not to scale. 
   DETAILED DESCRIPTION 
   Referring to  FIGS. 1-5  there is a tension sensing device  20  shown. Tension sensing device  20  has a moveable anchor bar  22  that is mounted to a bracket  30 . Anchor bar  22  has a pair of spaced arms  23  and  24 , a U-shaped end  25  and a pair of ends  26  and  27 . Anchor bar  22  also has a cross-member  28  with a hole  31 . A pair of polymer bushings  29  are mounted over ends  26  and  27 . Bracket  30  has a pair of uprights  32  with notches  33  and ears  34 . Bracket  30  also has a bottom plate  35  with a hole  36 . 
   Bracket  30  supports and retains anchor bar  22 . Ends  26  and  27  with bushings  29  rest in notches  33 . The bushings  29  allow anchor bar  22  to pivot or rotate with respect to bracket  30 . The axis of rotation or pivot point is labeled P in FIG.  4 . Ears  34  are bent over arms  23  and  24  after assembly to retain anchor bar  22  to bracket  30 . Bracket  30  and bar  22  are formed from 1018 steel. 
   A housing  40  is mounted between cross-member  28  and bottom plate  35 . Housing  40  has a pair of projections  42  on opposite sides and a connector shroud  44 . Each projection  42  has a groove  43 . Grooves  43  slide over arms  23  and  24  during assembly and hold the housing  40  to anchor bar  22 . Housing  40  has a pair of cavities  41 A and  41 B. A cover  45  seals housing  40 . Housing  40  and cover  45  are formed from plastic. Cover  45  has a slot  46  and a hole  47 . 
   A sensor  50  is mounted inside cavity  41 A. Sensor  50  can be one of several devices. For example, sensor  50  can be a switch, a hall effect sensor, a variable resistor or a pressure sensor. Sensor  50  preferably is a switch and more preferably is a micro-switch. For convenience, sensor  50  will now be referred to as switch  50 . The switch can be either a normally open or normally closed switch. Switch  50  has an arm  50 A that extends through slot  46  after assembly and is in contact with bottom plate  35 . Switch  50  is mounted to a printed circuit board  52  and is connected to printed circuit lines (not shown) on board  52 . Electronic components  53  such as transistors or resistors may be mounted to the printed circuit board if it is desired to condition the electrical output of switch  50 . Terminals  54  are mounted to printed circuit board  52  and connect with the printed circuit lines on board  52 . A connector  49  mounts to connector shroud  44 . Wire harness  48  is electrically connected through connector  49  to terminals  54 . Wire harness  48  provides power to switch  50 . Wire harness  48  would be connected to another electrical circuit such as an airbag controller so that the output signal from switch  50  can be used to control deployment of an airbag. 
   A spring  56  and actuator  58  are mounted in cavity  41 . Actuator  58  has an end  58 A that extends through hole  47  and another end  58 B that rests in the end of spring  56 . The other end of spring  56  is in contact with a threaded adjustment screw  39  that is mounted to housing  40 . Cover  45  is heat staked to join it with housing  40 . Spring  56  is preloaded to about 10 pounds by the compression of cover  45 . Adjustment screw  39  is used to adjust the spring preload and therefore to adjust the switch point tension. Actuator end  58 A passes through hole  47  and rests against bottom plate  35 . 
   Vehicle seat  70  has a seat bottom  71  and a seat back  72 . A child seat  74  is shown mounted in seat  70 . Child seat  74  is connected to anchor bar  22  by a latch hook or mini belt  76 . The latch hook or mini belt  76  has a mechanism to allow tightening of the child seat  74  to vehicle seat  70 . Tension sensing device  20  is shown mounted to a part of the vehicle seat frame called a seat member  60 . The seat frame is made from steel. A support  62  is welded to seat member  60 . Support  62  has a bore  63  and a tongue  64 . Tongue  64  has a threaded hole  65 . 
   Tension sensing device  20  is shown mounted to support tube  62 . Tension sensing device  20  is mounted above seat member  60  and extends into seat back  72 . Anchor bar  22  wraps around support  62 . Bracket  30  is mounted to support  62 . Bracket  30  rests on tongue  64 . Threaded fastener  68  passes through hole  36  and mates with the threads in hole  65 . 
   Assembly 
   The present invention would be assembled as follows:
     1. Terminals  54 , switch  50  and electronic component  53  are mounted to printed circuit board  52 .   2. Printed circuit board  52  is placed in cavity  41 A, adjustment screw  39 , spring  56  and actuator  58  are placed in cavity  41 B.   3. Cover  45  is placed over housing  40  and either heat staked or fastened in place with screws.   4. Housing  40  is mounted to anchor bar  22  by sliding grooves  43  onto arms  23  and  24 .   5. Bushings  29  are placed onto ends  26  and  27 .   6. Anchor bar  22  is placed onto bracket  30  with bushings  29  being pressed into notches  33 .   7. Ears  34  are bent over arms  23 ,  24  and projections  42  to retain the anchor bar to the bracket.   8. Support  62  is slipped over seat member  60  and welded in place during manufacturing of the seat.   9. Tension sensing device  20  is placed onto tongue  64  and attached using fastener  68 .   10. Connector  49  is mated onto connector shroud  44 .
 
Operation
   

   When a tension or pulling force is applied to anchor bar  22  by latch hook  76 , the anchor bar rotates about pivot point P. The starting or no tension position is shown in FIG.  4 . In  FIG. 4 , the anchor bar  22  is shown with a solid line at position T 1  with no applied tension. As the anchor bar  22  rotates, cross member  28  presses downwardly on the top of housing  40  causing spring  56  to start to be compressed. As more tension is applied to the anchor bar  22 , spring  56  will be further compressed and arm  50 A will start to be depressed. As more tension is applied to the anchor bar  22 , spring  56  will be further compressed and arm  50 A will cause switch  50  to move from an open state to a closed state allowing or altering an electrical current to flow between terminals  54 . As further tension is applied to the anchor bar  22 , spring  56  will be further compressed and the bottom of housing  40  will contact bottom plate  35  at which point depression of arm  50 A ceases. The anchor bar is shown as dotted at this position T 2  in FIG.  4 . It is noted that the switch will change states prior to the housing  40  bottoming on plate  35 . 
   In a high load situation, such as a sudden stop or as a result of the child seat being pulled or cinched down, the force applied to the anchor bar  22  overcomes the force of spring  56 . At this point, housing  40  moves to rest against bottom plate  35 . Any additional force from latch hook  76  is then transferred to bracket  30 , support tube  62  and seat member  60 . Thus, the excessive or overload forces are transferred from the child seat to the vehicle. In this way, no further force is applied to switch  50  and it is thus protected from mechanical damage due to excessive loads. The overload tension position is shown in  FIG. 4  as position T 2 . In  FIG. 4 , the anchor bar  22  is shown with a dotted line in the position with maximum tension. 
   If a further load is applied from position T 2 , the anchor bar  22  can bend to contact support  62  as an additional stop. 
   Remarks 
   The tension sensing device of the present invention has several advantages. It provides for detection of a child seat in a vehicle and can be connected with an airbag controller so that the airbag controller can use the child seat information to determine if an airbag is to be deployed. The tension sensing device allows accurate sensing of the presence of a child seat at low cost. The tension sensing device allows accurate sensing of low tensile forces, while at the same time protecting the switch or sensor from excessive loads that could damage the switch or sensor. 
   The present invention allows an airbag controller to make better decisions as to when and how to deploy an airbag based upon more accurate vehicle seat occupant information. In the case of a child&#39;s car seat being strapped into a car seat, the tension sensing device allows the airbag controller to properly compute that the seat occupant is a child and to prevent deployment of the airbag. 
   The tension sensing device of the present invention is readily mounted to existing vehicle seat frames without extensive modification. Thus, safety engineers can easily incorporate and install the tension sensing device into present and future vehicle designs. 
   Another advantage of the present invention is that it can accurately sense tension over a wide range of applied tension directions or tension vectors. Referring to  FIG. 5 , three different applied tension directions are shown, A, B and C. Because there are dozens of child seat manufacturers, each with their own design, the resulting tension vector can end up being applied from many different directions or angles. Because tension sensing device  20  has anchor bar  22  that rotates about point P, the actuation of switch  20  is substantially independent of the direction of applied tension. Switch  20  will actuate with nearly equal force if the direction of tension is applied along vector A, B or C or anywhere in between. The angle between vectors A and C can be up to 135 degrees and still maintain accurate sensing. 
   If the present invention was only to actuate at a given tension magnitude with a straight line tension, (for example along vector C), then if the same magnitude of tension was placed along vectors A and C, the switch would not be actuated as only a fraction of the tension magnitude would be applied to the switch. The present invention overcomes this potential problem by allowing the tension to be applied over a fairly wide range of angles while still accurately sensing tension. 
   Variations of the Invention 
   The sensor  50  shown was a switch. One skilled in the art will realize that the preferred embodiment would work with other types of sensors. For example, sensor  50  could be a hall effect sensor, a variable resistor, a pressure sensor or a reed switch. 
   Another variation of the tension sensing device would be to utilize other mounting structures or locations. For example, seat support  62  could be eliminated and bracket  30  welded to seat member  60 . Alternatively, tension sensing device  20  could be attached to the floor of the vehicle or to another location within the seat. 
   While the tension sensor was shown with an anchor bar  22 , other shapes of structures that would allow mounting to a child seat and rotation about point P could be used. For example, one half of anchor bar  22  could be used resulting in a C-shaped anchor bar. 
   The tension sensing device was used to detect a child seat. One skilled in the art will realize that the preferred embodiment could be used to detect other tensile forces at other locations. For example, tension sensing device  20  could be attached to a seat belt in a vehicle to detect seat belt tension. 
   While the invention has been taught with specific reference to these embodiments, someone skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.