Abstract:
The present invention provides an apparatus for determining a seat belt tension is within a proper range. The apparatus is designed to be easily adapted to existing vehicle safety belt systems. Three points of contact with the safety belt allow the apparatus to be used in portable applications including installing child seats. Generally, two of the contact points support the belt while the third contact point is accomplished using a member responsive to the tension of the seat belt. The response of the member is in communication with a device to indicate the amount of tension present in the seat belt. A visual or audible signal is provided to the operator when sufficient tension has been reached and maintained. The apparatus can be mechanical or electro-mechanical in nature. The apparatus provides the general public with the capability to periodically or continuously monitor the seat belt tension and can be used to secure a child seat alerting the operator when the belt tension is within or outside predefined installation limits.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an apparatus for use in automotive applications, to determine if a seat belt tension is within a predetermined range.  
       BACKGROUND OF THE INVENTION  
       [0002]     Automotive crash protection systems are well-known in the automotive industry. Crash protection systems generally fall into one of two categories; namely, active and passive restraints. Passive restraints include systems such as air bags where the deployment of the crash protection mechanism is initiated by the system. Active restraints, for instance manual type seat belts, are not deployed on initiative of the crash protection system, but are engaged by the operator. Both passive and active restraint systems are optimized to protect a range of adult occupant sizes. To service the need of protecting children in the event of a crash, child seats were developed to be used in conjunction with seat belt systems to properly restrain children. One of the most important parameters in installing child seats is the tension on the seat belt used to fasten the child restraint in the vehicle. However, the general public does not have a convenient means to determine if proper seat belt tension is provided upon installation of a child seat.  
         [0003]     Typically, a seat belt system is provided for restraining a child seat having an automatic locking retractor (ALR) function. This mode causes the retractor to act as a one-way clutch, allowing the belt to be retracted but not extended from the retractor. Proper belt tension is achieved by feeding the webbing into the retractor, thus compressing the seat cushion until the proper tension level is achieved.  
         [0004]     National statistics show that over 80% of the child seat installations made today are made incorrectly. It is estimated that over one third of incorrectly installed child seats are the result of improper seat belt tension. Seat belts in automobiles are designed to restrain the passenger within the vehicle. Sufficient belt tension is required to ensure that the child seat does not move, rock, or rotate out of the preferred installation position, and to ensure that the child seat operates properly in a dynamic crash event. Currently, child seat installations are judged acceptable based on a feeling, not a measurement. The general public is faced with the problem of not objectively knowing when adequate belt tension has been applied. Ideally, a system for measuring seat belt tension would be useable for existing vehicles without requiring that it be especially adapted for a specific vehicle design.  
       SUMMARY OF THE INVENTION  
       [0005]     In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a tension indicator apparatus for determining a seat belt tension is within a predetermined range.  
         [0006]     An embodiment of the present invention includes an S-clip and a displacement sensor. The vehicle seat belt is interwoven with the S-clip in a serpentine fashion. The S-Clip has three points of contact with the seat belt. Tension applied to the seat belt causes deformation of the S-clip, which is measured by a force sensing device. The force sensing device provides an output of the deformation and tension level.  
         [0007]     A visual or audible signal is provided to the operator when sufficient seat belt tension has been reached and maintained. The force sensing device can be mechanical or electro-mechanical in nature. Additionally, the tension indicator provides the general public with the capability to periodically or continuously monitor the seat belt tension and can be used to secure a child seat alerting the operator when the belt tension is within predefined installation limits.  
         [0008]     Child seats are purchased independent of automobiles and are often moved between vehicles. A significant benefit of the present invention includes that the apparatus is portable. The S-clip design allows the apparatus to be easily adapted to any existing vehicle safety belt systems.  
         [0009]     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an isometric cut away view of the apparatus for measuring belt tension according to the present invention;  
         [0011]      FIG. 2  is an isometric view of the apparatus for measuring belt tension illustrating the torsion created in the center section according to the present invention;  
         [0012]      FIG. 3  is a side cut away view of a mechanical embodiment of the apparatus according to the present invention;  
         [0013]      FIG. 4  is a side view of another mechanical embodiment of the apparatus according to the present invention; and  
         [0014]      FIG. 5  is an isometric cutaway view of another mechanical embodiment of the apparatus according to the present invention; and  
         [0015]      FIG. 6  is a side view of the mechanical embodiment illustrated in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring now to  FIGS. 1 and 2 , an apparatus, specifically a seat belt tension indicator, adapted to determine if seat belt tension is within a predetermined range embodying the principles of the present invention is illustrated therein and designated at  10 . As its primary components, the seat belt tension indicator  10  includes an S-clip  15  and a force sensing device  20 .  
         [0017]     As illustrated, the S-clip  15  includes first, second, and third sections or members, in the form of first and second legs  4  and  16 , and center section  18 . The first leg  14  and second leg  16  of the S-clip  15  extend from opposite ends of center section  18 . The center section  18  is located between the first leg  14  and the second leg  16 . The S-clip  15  is designed to have the belt  12  interwoven between the center section  18  and legs  14 ,  16  in a serpentine fashion. Each leg  14  and  16  forms a tooth  21  to retain the seat belt  12  in the S-clip  15 . The first leg  14  and second leg  16  contact the bottom web surface  19  of the seat belt  12  while the base plate  18  contacts the top web surface  17  of the seat belt  12 . Since S-clip  15  is flat, the belt  12  must follow a serpentine path as it is woven into the S-clip. The configuration of the S-clip  15  causes it to be exposed to deformation stress in response to the seat belt tension. Additionally, the configuration shown allows the tension indicator  10  to respond independent of any other mechanism contacting the seat belt  12 .  
         [0018]     As shown in  FIG. 2 , the attachment of the first leg  14  to the center section  18  at one end of the center section causes a first force F 1  to be created by the tension in the seat belt  12 . Conversely, the second leg  16  being attached to center section  18  on the opposite end causes the tension of the seat belt  12  to produce a second force F 2  in a direction opposite the first force F 1 . The first and second forces F 1  and F 2  cooperate to create a torsion stress and resulting strain in the center section  18 . The torsion in the center section  18  can be sensed using a torsion sensing device  20 .  
         [0019]     The force sensing device  20  includes a strain sensor element  22 , an electronic assembly  25 , and leads connecting the strain sensor element  22  to the electronic assembly  25 . Strain sensor element  22  creates an electrical signal based on the torsional strain of the center section  18 . A conventional resistance type strain gage may be used in this application. The electrical signal is communicated to the electronic assembly  25  through the leads  24 .  
         [0020]     The leads  24  are connected to a printed circuit board  26  included in the electronic assembly  25 . The electrical signals are communicated through the printed circuit board  26  to an integrated circuit (not shown). The integrated circuit interprets the electronic signals and determines whether the seat belt  12  has a tension in a predetermined range. If the seat belt has a tension within the predetermined range, the integrated circuit will illuminate a green LED  32 , otherwise the integrated circuit will illuminate a red LED  30 . Similarly, the integrated circuit can communicate an electrical signal with a tone generator  34  to create an audible alert indicating whether proper tension exists in the seat belt  12 . If the electrical signal cannot be interpreted by the integrated circuit, a yellow fault LED  28  will be illuminated. A button  40  is also coupled to the integrated circuit for clearing faults or providing a zero/reference tension. Additional buttons  36 ,  38  are also provided to power on or power off the electronic assembly  25 . A bracket  42  is attached to the S-clip  15  to support the electronic assembly  25 . The bracket  42  prevents stress from being introduced into the leads  24  connecting the strain element  22  to the printed wiring board  26 . A cover  44  is attach to the bracket  42  serving to protect the electronic assembly  25  from external environmental conditions.  
         [0021]     Now referring to  FIG. 3 , the present invention also provides for a mechanical implementation of the apparatus which does not require an electronic assembly. The mechanical implementation, incorporates an S-clip  45  substantially identical with that shown in  FIGS. 1 and 2  having a first leg  14  and second leg (not shown). The responsive member  46  is shown as a guide plate  46 . The seat belt  12  is interwoven between the two legs and the guide plate  46 . The two legs contact the bottom web surface  19  of the seat belt  12  while the guide plate  46  contacts the top web surface  17  of the seat belt  12 . The guide plate  46  is supported by a biasing member  48 . The biasing member  48  is illustrated as a leaf spring  48 . The leaf spring  48  biases the guide plate  40  away from the S-clip  45  and against the tension of the seat belt  12 . The leaf spring  48  should be capable of providing between 30 and 50 lbs. of force to the guide plate  46 . A button  50  is supported by the leaf spring  48  and translated as the tension of the seat belt  12  forces the guide plate  46  to compress the leaf spring  48 .  
         [0022]     A belt guide  52  is attached to the S-clip  45 . The button  50  protrudes through a bore  51  in the center section of S-clip  45  and a belt guide  52 . The belt guide  52  includes a lip  54  around the bore  51 . The button  50  has a first colored ring  56  on the end of the button  50  opposite leaf spring  48 . A second colored ring  58  is located adjacent to the first colored ring  56 . When the tension in the seat belt  12  is less than the predetermined range, only the first colored ring  56  of the button  50  is visible over the lip  54 . As the tension from the seat belt  12  results in the translation of the button  50 , the second colored ring  58  becomes visible over the lip  54  indicating the seat belt  12  has a tension in the predetermined range.  
         [0023]     Now referring to  FIG. 4 , another mechanical configuration of the present invention provides for a first member  61  and a second member  63  located to engage with the seat belt  12 . The first and second member  61 ,  63  are shown as a first roller  61  and a second roller  63 . The first roller  61  is attached to the bottom of a base plate  76  by a standoff  78 . Likewise, roller  63  is attached to the bottom of the base plate  76  by a standoff  80 . A third member  65  is located between roller  61  and roller  63 . The third member  65  is shown as a pin assembly  65 . The two rollers  61 ,  63  in cooperation with the pin assembly  65  forms an “S” shaped configuration such that the rollers  61 ,  63  are oriented parallel to each other but are attached to opposite ends of the base plate  76 .  
         [0024]     The seat belt  12  is interwoven between the two rollers  61 ,  63  and the pin assembly  65 . The roller  61 ,  63  contacts the bottom web surface  19  of the seat belt  12  and the pin assembly  65  contacts the top web surface  17  of the seat belt  12 . The pin assembly  65  includes a rounded head  64  for contacting the seat belt  12 , a shaft  62  protruding through a bore  66  in the base plate  76 , and a colored head  68  located on the top side of the base plate  76 . A biasing member  60  is illustrated as a spring  60  surrounding the shaft  62 . The spring  60  is compressed between the rounded head  64  and the base plate  76  to bias the pin assembly  65  against the seat belt  12 . As the tension of the seat belt  12  increases, the pin assembly  65  translates causing colored head  68  to move away from base plate  76 . A scale  69  is attached to the base plate  76 . The scale  69  has a red section  74 , a yellow section  72 , and a green section  70 . If the colored head  68  aligns with a red section  74 , minimum tension is present in the seat belt  12 . When the colored head  68  is aligned with the yellow section  72 , average tension is present in the seat belt  12 . However, when the colored head  68  is fully extended, the head  68  is aligned with the green section  70  indicating proper tension exists in the seat belt  12 .  
         [0025]     Now referring to  FIGS. 5 and 6 , another mechanical configuration of the present invention provides for a first member  90  and a second member  92  located to engage with the seat belt  12 . The first and second member  90 ,  92  are shown as a first roller  90  and a second roller  92 . The first roller  90  is attached to a base roller  94  by a first arm  96 . Likewise, roller  92  is attached to the base roller  94  by a second arm  98 . Similar to previous embodiments, the first and second roller  90 ,  92  in cooperation with the base roller  94  form an “S” shaped configuration. The first and second roller  90 ,  92  are oriented parallel to each other but are connected to the base roller  94  at opposite ends. The seat belt  12  is interwoven between the two rollers  90 ,  92  and the base roller  94 . The first roller  90  and the second roller  92  contact the bottom web surface of the seat belt  12 , while the base roller  94  contacts the top web surface of the seat belt  12 . End caps  100  and  102  act to retain the seat belt  12  in alignment with rollers  90  and  92 .  
         [0026]     A biasing member  104  is shown as a torsional spring  104 , however, other biasing members, for example a coil spring could be used. The torsional spring  104  is located inside the base roller  94 . The first arm  96  has a hub  112  including a slot  110  for receiving the torsional spring  104 . Similarly, the second arm  98  has a hub  106  including a slot  108  also for receiving the torsional spring  104 . The first arm  96  includes a first plate  114 . Similarly, the second arm  98  includes a second plate  116 . The first and second plates  114 ,  116  are oriented parallel to each other but perpendicular to the base roller  94 . Each plate  114 ,  116  pivots in opposite directions and relative to the amount of applied belt tension or load. The base roller  94  serves as the pivot center. The plates  114 ,  116  pivot outward as belt tension/load increases and pivot inward when it decreases.  
         [0027]     Secured into the first plate is an indicator pin  118  that extends the length of the base roller  94  and through a slot  120  in the second plate  116 . The second plate  116  has a red mark  122 , a yellow mark  124 , and a green mark  126  near where the indicator pin  118  extends through the second plate  116 . The alignment of the pin  118  with the markings  122 ,  124 ,  126  indicates the level of belt tension or load. The indicator pin  118  aligning with the red marking  122  indicates insufficient load. The indicator pin  118  aligning with the yellow marking  124  indicates adequate load. While the indicator pin  118  aligning with the green marking  126  indicates sufficient load. The markings  122 ,  124 ,  126  are located relative to the amount of load and corresponding outward pivoting movement between the first and second plates  114 ,  116 .  
         [0028]     As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from spirit of this invention, as defined in the following claims.