Abstract:
A seat belt alarm, for use with an existing seat belt having a tongue having a tongue flange extending laterally outward, and a buckle having a buckle housing, a front face having a slot for accepting the tongue and locking the tongue therein. The seat belt alarm has an L-shaped housing that selectively attaches beneath the buckle housing and extends alongside the buckle housing. When the L-shaped housing is so positioned, a plunger extends forwardly alongside the buckle housing so that when the tongue is within the slot the tongue flange keeps the plunger inward. If the seat belt is suddenly released and the tongue flange moves away from the front face, a switch in cooperation with the plunger triggers an audible warning.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a seat belt alarm. More particularly, the invention relates to a system that warns a parent when the child has released the seat belt. 
   Highway safety statistics comparing accident victims who were wearing seat belts to those who were not are hard to ignore. In particular, it is quite clear that wearing a seat belt is a simple step that could easily save the life of a passenger. Accordingly, most adults wear seat belts. 
   Seat belt usage is particularly important for children. For this reason, it is in most respects mandatory for children to wear their seat belt when traveling in an automobile. Unfortunately, children typically do not like wearing a seat belt. It prevents them from following their natural, child impulses, and constrains their movements. As a result, it is common that a child will release his/her seat belt while the vehicle is in motion. The parents, however, are often unaware that their child is no longer restrained, and might suffer significant injury or worse if there was an accident. 
   For this reason, some have proposed alarms that seek to notify a parent that the child has released the seat belt. 
   For example, U.S. Pat. No. 5,944,135 to Blackburn et al., U.S. Pat. No. 6,002,325 to Conaway, and U.S. Pat. No. 6,175,304 to Becker each disclose a system which is incorporated into the seat belt buckle which detects the presence or absence of the seat belt tongue therein. These references propose improved seat belt devices that can be incorporated into newly manufactured cars. Unfortunately, these references will not work with existing seat belt systems. 
   In this regard, U.S. Pat. No. 5,596,312 to Fowler et al., and U.S. Pat. No. 6,351,210 to Stewart both disclose systems which have a slot for accepting the tongue of the existing seat belt and locking the tongue therein, and then have an auxiliary tongue which is to be used with the existing buckle, for producing an alarm when the auxiliary tongue is released. These devices, however, are unnecessarily complex, and can be easily defeated by a clever child by simply unlocking the tongue of the existing belt from the slot. 
   U.S. Pat. No. 6,339,371 to Baggelaar et al. discloses a self contained, buckle attachable and actuated alarm device, which attaches beneath the seat belt buckle, and has a metal plate which is trapped between the seat belt tongue and the buckle, so that when the tongue is released, the plate will fall away and release a switch to trigger an alarm. Once again, Baggelaar et al. unnecessarily complicates the usage of the seat belt, and requires a plate that is easily lost when the seat belt is released. 
   While these units may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present invention as disclosed hereafter. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to produce a seat belt alarm that effectively warns a parent when the child has unexpectedly released his/her seat belt. Accordingly, the device is configured to sound an alarm when the seat belt is suddenly released. 
   It is another object of the invention to provide a seat belt alarm that is adaptable to existing seat belt systems. Accordingly, the device is self-contained, and attaches to existing seat belt buckles. 
   It is yet another object of the invention to provide a seat belt alarm that is integrated within a one-piece device. Accordingly, the alarm has an L-shaped housing including a flange which adheres beneath the buckle and a switch which extends alongside the buckle to which the alarm housing is attached, so as to be responsive to the presence of the seat belt tongue flange, and to react upon the sudden absence of the seat belt tongue flange, indicating that the seat belt has been suddenly released. 
   It is a further object of the invention to employ a switch that triggers an audible warning upon the sudden release of the plunger by making a momentary contact with the outward movement of the plunger. The warning continues for a predetermined period. 
   The invention is a seat belt alarm, for use with an existing seat belt having a tongue having a tongue flange extending laterally outward, and a buckle having a buckle housing, a front face having a slot for accepting the tongue and locking the tongue therein. The seat belt alarm has an L-shaped housing that selectively attaches beneath the buckle housing and extends alongside the buckle housing. When the L-shaped housing is so positioned, a plunger extends forwardly alongside the buckle housing so that when the tongue is within the slot the tongue flange keeps the plunger inward. If the seat belt is suddenly released and the tongue flange moves away from the front face, a switch in cooperation with the plunger triggers an audible warning. 
   To the accomplishment of the above and related objects the invention may be embodied in the form illustrated in the accompanying drawings. Attention is called to the fact, however, that the drawings are illustrative only. Variations are contemplated as being part of the invention, limited only by the scope of the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, like elements are depicted by like reference numerals. The drawings are briefly described as follows. 
       FIG. 1  is an assembly view, illustrating the invention, and its installation to a seat belt buckle, for use in conjunction with the seat belt tongue associated with the seat belt buckle. 
       FIG. 2  is a diagrammatic perspective view, illustrating the invention installed upon a seat belt buckle, wherein the seat belt tongue is about to be inserted into the seat belt buckle. 
       FIG. 3  is a diagrammatic perspective view, illustrating the seat belt tongue engaged with the buckle, wherein the tongue flange is holding the plunger of the present invention in its retracted position. 
       FIG. 4  is a side elevational view, with parts broken away, illustrating the switch in an open circuited condition as the plunger is in the retracted position because the tongue flange is pressing against the plunger. 
       FIG. 5  is a side elevational view, with parts broken away, wherein the seat belt has been released, releasing the tongue, and thereby extending the plunger, the plunger contact makes a momentary electrical connection with the camming contact. 
       FIG. 6  is a side elevational view, with parts broken away, wherein the plunger is fully extended, such that as the plunger contact moved past the camming contact it moved the camming contact into a position such that it will not make an electrical connection with the plunger contact when the plunger is once again retracted. 
       FIG. 7  is a block diagram, illustrating functional interconnection of components of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a seat belt assembly  10 , comprising a buckle  20  and a tongue  30 . The seat belt assembly  10  of course includes an actual seat belt  12 , which is bisected such that one portion is permanently attached to the buckle  20 , and the other portion is permanently attached to the tongue  30 . The buckle  20  has a housing  22 , including a front face  22 F, a top  22 T, a bottom  22 B, and a pair of sides  22 S. The housing  22  has a slot  24  that is accessed at the front face  22 F for accommodating the tongue  30 , and locking the tongue when fully inserted therein. The buckle  20  further has a release button  26  for releasing the tongue  30  and allowing it to be removed from the slot  24  by pressing the release button  26 . The tongue  30  has a tongue flange  32  that extends laterally from the tongue  30 , such that when the tongue  30  is engaged within the slot  24 , the tongue flange  32  extends laterally beyond the sides  22 S of the buckle. The tongue flange  32  facilitates safe handling of the tongue  30  and allows the belt  12  attached thereto to be wider than the tongue  30 . Accordingly, this feature is typical, and probably standard, among conventional seat belt assemblies  10  in common usage in modern domestic and foreign automobiles, and is key to the functionality of the present invention, as will be described in detail hereinafter. 
     FIG. 1  also illustrates a seat belt alarm  50  having a switch housing  58 , an alarm housing  52  attached to the switch housing  58 , and a bottom plate  54  which extends at a substantially right angle from the switch housing  58 . The switch housing  58  incorporates a switch  57 , including a plunger  60 . The switch housing  58  has a front  58 F from which the plunger  60  extends. The bottom plate  54  and switch housing  58  together form a one-piece, L-shaped device. In particular, the bottom plate  54  has a top surface  54 T with an adhesive pad  56  mounted thereon. Prior to installation, the adhesive pad  56  has a backing strip  59  present thereon to prevent the adhesive pad  56  from inadvertently adhering to objects prior to installation of the invention. To install the invention, the backing strip  59  is peeled from the adhesive pad  56 , the switch housing front  58 F is aligned with the buckle housing front face  22 F and the adhesive pad is adhered to the buckle housing bottom  22 B such that the alarm housing  52  extends along one of the sides  22 S of the buckle housing  22 , and the plunger  60  projects forwardly beyond the buckle housing front face  22 F. 
   Referring now to  FIG. 2 , the seat belt alarm  50  is indeed attached to the buckle  20 , wherein the front  58 F of the switch housing  58  is aligned (flush) with the front face  22 F of the buckle housing  22 . The plunger  60  is fully extended, as no external force is acting thereupon. Also illustrated, the tongue  30  is about to be engaged with the slot  24 . When the tongue  30  is fully inserted into the slot  24 , the tongue ‘clicks’ and locks into place—as with most or all conventional seat belt assemblies  10 . In addition, as illustrated in  FIG. 3 , the tongue flange  32  pushes (retracts) the plunger  60  substantially into the switch housing  58 , as the seat belt flange substantially extends laterally beyond the sides  22 S of the buckle housing  22  at the front face  22 F thereof. As long as the seat belt tongue  30  remains engaged with the slot  24 , the plunger  60  will remain fully within the switch housing  58 . 
   Now that the structure has been adequately described, the manner of operation of the present invention  50  is now described with reference to  FIG. 7 , as well as  FIGS. 2 and 3 . In particular, within the alarm housing  52  adjacent to the switch  57  is an annunciator  80 , capable of generating the audible warning signal. A battery  82  supplies power to a latch/timer unit  84  and to the switch  57 . The latch/timer unit  84  has a trigger input  85 . In response to power being applied to the trigger input  85 , the annunciator  80  is activated/enabled to provide an audible warning to a parent. The latch/timer unit  84  will maintain such warning for a predetermined interval—perhaps fifteen to sixty seconds. Accordingly to  FIG. 7 , it is apparent that the triggering of the latch/timer unit  84  and the warning signal subsequently generated occurs in response to an electrical connection provided by the switch  57 . 
   Thus, in furtherance of the goals of the present invention, and in a manner described in the discussion of  FIG. 4 through 6  hereinafter, the switch  57  is configured so that is will provide a momentary electrical connection between the battery  82  and trigger input  85  to trigger the latch/timer unit  84  when the plunger  60  is suddenly extended, but does not create any such electrical connection when the plunger  60  is fully extended, fully retracted, or being retracted. Accordingly, the annunciator  80  will only be activated when the seat belt is suddenly released. Accordingly, when the seat belt tongue  30  is inserted into the slot  24 , the plunger is fully depressed (retracted) by the tongue flange  32  pressing against said plunger  60 . When a child presses the release button  26 , the tongue  30  is released from the slot  24  and the tongue flange  32  naturally moves away from the buckle front face  22 F of the buckle housing such that it no longer presses the plunger  60  inward. Accordingly, under spring biasing, the plunger  60  extends outward from the switch housing  58 , close circuiting the switch and triggering the alarm and the sounding of an audible warning signal. 
     FIG. 4  illustrates the switch  57  with parts of the switch housing  58  broken away. The switch housing  58  has a rear  58 R, and a spring  62  biased between the rear  58 R and the plunger  60 . The plunger has a plunger contact assembly  64 , which includes an electrically insulative body  66 , and an electrically conductive plunger contact  68 . The insulative body  66  has a convex forward portion  66 F, a substantially flat and horizontal top  66 T, and a substantially flat and horizontal top  66 B. The top  66 T and bottom  66 B of the insulative body  66  are substantially parallel to each other and to the direction of motion of the plunger. The plunger contact  68  is located on the forward portion  66 F of the insulative body, near the bottom  66 B. 
   The switch  57  also includes a movable contact  70  that is electrically conductive and is substantially boomerang shaped, having a short leg  72  and a long leg  74 . The movable contact  70  is pivotally mounted adjacent to the plunger  60  at a movable contact pivot point  76  that is above the top  66 T of the insulative body  66 . The short leg  72  of the movable contact  72  is located forward of the movable contact pivot point  76  and the long leg  74  is located rearward thereof. The movable contact  70  selectively makes physical contact with the plunger contact assembly  64  as the plunger is extended and withdrawn. The switch  57  is configured so that contact between the movable contact  70  and the plunger contact  68  will close circuit the switch  57 . 
   The movable contact  70  is substantially ‘boomerang’ shaped—except that the long leg  74  is longer than the short leg  72 . In particular, the geometry of the movable contact  70  is such that when the plunger  60  is being retracted the top  66 T of the insulative body  66  touches the long leg  74  and pushes said long leg  74  upward to pivot the short leg downward so that it is in the path of the plunger contact  68 . Accordingly, referring to  FIG. 5 , when the tongue  30  is suddenly released from the buckle  20 , the tongue flange  32  releases the plunger  60 , such that the spring  62  expels the plunger  60  outward. While moving outward with the plunger  60 , the forward portion  66 F of the insulative body  66 , and thus the plunger contact  68  thereon touches the short leg  72  of the movable contact  70  and thereby makes a momentary electrical connection with the movable contact  70 , triggering the alarm. Then, as the plunger  60  continues outward, the convex forward portion  66 F of the insulative body  66  immediately above the plunger contact  68  pushes against the short leg  72 , pivoting the long leg  74  downward as seen in FIG.  6 . Accordingly, when the plunger  60  is once again pressed inward, the short leg  72  will not make contact with the plunger contact  68 , and the insulative body  66  will strike the long leg  74 , once again pivoting the short leg  72  downward after the forward portion  66 F (and plunger contact  68  thereon) is already rearward of the short leg  72 . Accordingly, the switch  57  operates such that that no electrical connection is made during the inward motion (retraction) of the plunger  60 . Upon the sudden expulsion (extension) of the plunger  60 , however, momentary electrical contact will once again occur between the movable contact  70  and the plunger contact  68  to trigger the alarm. 
   By way of equivalent variation of the structure of the switch  57  described immediately above, it should be appreciated that only the short leg  72  need be electrically conductive. In addition, if the long leg  74  is electrically insulative, then the insulative body  66  is less important as the plunger contact could then safely contact the long leg  74  without close circuiting the switch. 
   In conclusion, herein is presented a system for providing a simple alarm device that may be readily attached to existing seat belt assemblies to provide an audible warning when the seat belt is suddenly released. The invention is illustrated by example in the foregoing description and in the appended drawing figures. Such is illustrative only of the numerous variations possible of the inventive concept. Such variations are contemplated as being a part of the present invention.