Abstract:
A child safety device for a vehicle including a seat including a shell, a harness including at least one strap for retaining an occupant in the seat, and a sensor between a device on the strap and the seat shell indicating a tension status of the harness.

Description:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a harness tension sensor and related apparatus for a child safety seat. Child safety seats have a harness that includes a pair of shoulder straps that extend from the back rest of the seat across the shoulders of the seat occupant and a crotch strap that extends upwardly from the seat bottom to a point between the legs of the seat occupant. The shoulder straps extend downwardly and have latch members that interconnect with a latch affixed to the crotch strap that extends upwardly through a slot from below the seating surface. A tensioning strap extends through an opening in the front of the seating surface. When the shoulder straps are latched into the latch, the tensioning strap is pulled to place the shoulder straps in tension so that they fit securely against the anterior aspect of the upper torso of the seat occupant. Any significant slack in the shoulder straps can increase the risk of injury by subjecting the seat occupant to an initial rapid, unrestrained acceleration before the shoulder straps are tensioned by the forward movement of the seat occupant and bring the seat occupant to an almost instantaneous stop. 
         [0002]    At present, child safety seats do not incorporate a reliable means to determine whether the shoulder straps have been properly tensioned. Some proposals for placing tension sensors in the latch or elsewhere require wiring in the crotch strap or in other locations in the seating area. This wiring may be subject to wear or exposure to moisture during use or cleaning, and thus may be less than fully desirable for use in situations, such as child safety seats, that should be cleaned periodically, or are subject to wetting from spilled drinks or other liquids. 
         [0003]    Also, it may not be fully apparent in all cases that the shoulder straps have not been fully latched. Thus, inadequate tension on the shoulder straps may be the result of simple failure to sufficiently tighten the shoulder straps, or because the shoulder straps have not been properly latched. In the case of improper latching, the seat occupant is essentially unprotected in the event of an impact, since the latch members will exit the latch and prevent any significant tension at all on the straps during the initial phase of the impact. 
         [0004]    In addition, present child safety seats to not provide a positive means of indicating that the seat has been subjected to a load of sufficient severity to require that the seat not be further used. A severe impact may stretch the shoulder straps beyond their elastic limit, warp or damage plastic seat parts, or otherwise render the seat unsafe for further use. In many cases the damage will not be readily visible and, in any event, it may not be apparent to the user that the damage is severe enough to require seat replacement. 
       SUMMARY OF THE INVENTION 
       [0005]    Therefore, it is an object of the invention to provide a harness tension sensor and related apparatus for a child safety seat. 
         [0006]    It is another object to provide a child safety seat that has a sensor that detects both that the seat is properly latched and that the shoulder straps have been properly tensioned. 
         [0007]    It is another object to provide a child safety seat that has a sensor that detects that the seat is properly latched and that the shoulder straps have been properly tensioned, wherein the operative elements of the sensor and related parts are under the seat and away from wear and liquids. 
         [0008]    It is another object to provide a child safety seat that has a sensor that detects that the seat has been subjected to a load of sufficient severity that further use of the seat should not be permitted. 
         [0009]    These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a child safety device for a vehicle including a seat including a shell, a harness including at least one strap for retaining an occupant in the seat, and a sensor between a device on the strap and the seat shell for indicating whether the harness is sufficiently tensioned. 
         [0010]    According to another preferred embodiment of the invention, the harness includes shoulder straps and a crotch strap. 
         [0011]    According to another preferred embodiment of the invention, the device on the strap includes a strap buckle or slide. 
         [0012]    According to another preferred embodiment of the invention, the sensor is positioned on a shell bottom. 
         [0013]    According to another preferred embodiment of the invention, a child safety device for a vehicle includes a seat including a shell, a harness including at least one strap for retaining an occupant in the seat, and a sensor including crushable members between a device on the strap and the seat shell for indicating whether the harness has been severely tensioned. 
         [0014]    According to another preferred embodiment of the invention, the crushable members are calibrated to crush at 500-700 pounds of load. 
         [0015]    According to another preferred embodiment of the invention, the crushable members comprise ribs or thin walls. 
         [0016]    According to another preferred embodiment of the invention, the sensor is a one use, one way type. 
         [0017]    According to another preferred embodiment of the invention, a child safety device for a vehicle includes a seat including a shell and a harness including a strap for retaining an occupant in the seat. The device further includes a sensor between a device on the strap and the seat shell for indicating whether the harness is sufficiently tensioned, and a sensor including crushable members between the device on the strap and the seat shell for indicating whether the harness has been severely tensioned. 
         [0018]    According to another preferred embodiment of the invention, both sensors are positioned under the seat shell. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Embodiments of the invention may be best understood by reference to the following description in conjunction with the accompanying drawing figures in which: 
           [0020]      FIG. 1  is front perspective view of an embodiment of a child safety seat; 
           [0021]      FIG. 2  is side view of the embodiment of the child safety seat; 
           [0022]      FIG. 3  is an enlarged view of an embodiment of a crash occurrence assembly for the child safety seat; 
           [0023]      FIG. 4  is a top view of an embodiment of a sensor housing; 
           [0024]      FIG. 5  is a side view of the sensor housing of  FIG. 4  showing crash occurrence and belt tension sensors; 
           [0025]      FIG. 6  is an enlarged side view of an embodiment of a belt tension sensor in a closed state; 
           [0026]      FIG. 7  is an enlarged side view of an embodiment of a crash occurrence sensor in an open state; 
           [0027]      FIG. 8  is a side view of the crash occurrence sensor of  FIG. 7  in the closed state; 
           [0028]      FIG. 9  is an enlarged side view of an embodiment of a belt tension sensor in an open state; 
           [0029]      FIG. 10  is a side view of the belt tension sensor of  FIG. 9  in the closed state; 
           [0030]      FIG. 11  is an enlarged side view of an embodiment of a combined belt tension and crash occurrence sensor showing the belt tension sensor in a closed state; and 
           [0031]      FIG. 12  is a side view of the embodiment of  FIG. 11  showing the crash occurrence sensor in a closed state. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]      FIGS. 1-3  show a child safety seat  12  and harness  20  including a pair of shoulder straps  23  and  25  for insertion into a buckle  22  fixed to a crotch strap  26  that passes through a slot  29  in a seat shell  14  and is fixed at a distal end to a three bar slide  27 . A sensor housing  18  is positioned between the seat shell  14  and the three bar slide  24 . 
       Tension Sensor 
       [0033]    As shown in  FIGS. 1-6  and  9 - 11 , the tension sensor  10  is designed to insure that sufficient tension is present in a harness  20  for a child safety seat  12 . The sensor  10  may be associated with a buckle  22  or three bar slide  24  that captures one end of the crotch strap  26 . The buckle  22  or three bar slide  24  is sufficiently large to retain the crotch strap  26  in the correct position between the legs of the seat occupant by bearing against the underside or bottom of the plastic seat bottom shell  14  with the strap  26  itself extending through the slot  29  and into the crotch area of the seat occupant. 
         [0034]    In one embodiment shown in  FIGS. 1-3 , the sensor  10  sits between the crotch strap buckle  22 , or, a three-bar slide  24 , and the plastic seat bottom shell  14 . When sufficient tension is on the harness  20 , the crotch strap  26  or three bar slide  24  is pulled upwardly thorough the slot  29  in the seat  12  bottom, and the buckle  22  or three bar slide  24  presses the sensor  10  against the seat bottom shell  14 . 
         [0035]    In one embodiment, a plunger  42  or other mechanism urges the sensor  10  from a normally open position to a closed position when there is too little tension on the harness  20 . Closing the circuit allows a current to flow to a device such as a microprocessor that can activate any conventional alert means, such as a bell, buzzer, light, etc. that the harness needs to be further tightened. Latching the harness correctly and/or further tightening the harness  20  opens the circuit and deactivates the alert. 
         [0036]    Conversely, the circuit can be designed so that the circuit is normally closed when the tension is correct, as shown in  FIGS. 6 and 10 , and in the open condition when the tension must be increased, as shown in  FIGS. 5 and 9 . The open circuit is sensed and a microprocessor generates the alert, as described above. 
         [0037]    The sensor may be any suitable pressure-sensitive on-off type switch, for example, spring-loaded contacts  13  that engage a complementary contact  15  in order to close the circuit, as shown in FIGS.  5  and  9 - 12 . 
       Crash Occurrence Sensor 
       [0038]    As shown in  FIGS. 1-5 ,  7 - 8  and  11 - 12 , in another aspect of the invention, the child safety seat  12  has a sensor  11  that detects that the seat  12  has been subjected to a load of sufficient severity that further use of the seat  12  should not be permitted. This crash occurrence sensor  11  may be used together with or separate from the tension sensor  10  described above.  FIG. 11  shows an embodiment of the invention wherein a plunger  42  indicates first that belt tension is sufficient and also indicates when the harness  20  has been subjected to a more severe load. 
         [0039]    In general, the crash occurrence sensor  11  is a “one use, one way” sensor. When it detects a severe load on a single occasion, it closes a circuit that provides an alert that the seat  12  has potentially been subjected to sufficient damage that the seat  12  should be discarded and not further used. The circuit is designed not to return to a normal state. 
         [0040]    More specifically, the crash occurrence sensor  110  includes crushable members  77  that are calibrated to crush at, for example, 500-700 lbs. of load. Crushing of the crushable members  77 , as shown in  FIGS. 8 and 12 , closes a circuit. The crushable members  77  may be ribs, thin walls, foam or honeycomb materials, or any other suitable material that has the ability to resist crushing up to a predetermined point, and then reliably crush to a degree sufficient to close a circuit. 
         [0041]    As also shown in the attached drawings, the crushable members  77  may be positioned on an upper surface of the crotch strap buckle  22 , or a three-bar slide  24 , so that in the event of a severe load, the buckle  22  or slide  24  is pulled upwardly against the plastic shell  14  of the seat by the crotch strap  26  so severely that the crushable members  77  are crushed against the plastic shell  14 , engaging the contact  17  and  19  to close a circuit. With less severe loads, the crushable members  77  do not crush to any appreciable degree. 
         [0042]    As is apparent from the foregoing, all of the electronic features of both the tension sensor  10  and the crash occurrence sensor  11  may be placed under the seat shell  14  away from the seat occupant and possible wear and damage.