Abstract:
An alarm system for use with a motor vehicle to sound an alert whenever child passengers are left unattended and belted in a parked motor vehicle, including a transmitter for generating a radio signal characterized by a predetermined frequency, a receiver for receiving and rectifying the radio signal, a sensor for sending an ignition status signal to the receiver if the vehicle ignition is on, a timer for sending an activation signal in response to the receiver receiving the radio message and the ignition status signal, and an alarm for generating an audible signal in response to receipt of the activation signal.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to safety devices and, more particularly, to an alarm system to alert drivers when a child passenger&#39;s seatbelt remains fastened after the automobile is parked and the engine turned off. 
     BACKGROUND OF THE INVENTION 
     Unfortunately, a number of infants and small children are inadvertently left buckled in their car seats in parked automobiles. In most of these cases, the drivers are parents or other caretakers who are breaking their normal (usually early morning) routines by taking the child along. The driver, presumably feeling the distracting effects of fatigue, stress, or the like, simply forgets the child is in the car seat and leaves the parked vehicle with the child still inside. The likelihood of this event occurring increases with the presence of other factors, such as if the child is sleeping or otherwise silent, if the child is one of many children and gets ‘lost in the shuffle’, or the like. 
     There is thus a need that the driver be reminded of the presence of child passengers in the vehicle who cannot otherwise speak up for themselves. The present invention addresses this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to method and apparatus for generating an alarm signal in the event a child is left belted in a parked vehicle. One object of the present invention is to provide an improved vehicle alarm design. Related objects and advantages of the present invention will be apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first embodiment of a safety alarm belt assembly of the present invention. 
         FIG. 2  is an enlarged perspective schematic view of a child passenger engaged in a portion of the assembly of  FIG. 1 . 
         FIG. 3A  is an enlarged partial perspective schematic view of the belt portion of the assembly if  FIG. 1  with the buckle portions engaged. 
         FIG. 3B  is an enlarged partial perspective schematic view of the belt portion of the assembly if  FIG. 1  with the buckle portions disengaged. 
         FIG. 4  is a schematic diagram of a first embodiment analog circuit usable with the embodiment of  FIG. 1 . 
         FIG. 5  is a flow chart diagram of the logic of a second embodiment digital circuit usable with the embodiment of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
       FIGS. 1-4  relate to a first embodiment of the present invention, a safety alarm system  10  for preventing the accidental leaving of a child passenger in a vehicle, such as an automobile, once the vehicle has been parked and the engine turned off. The safety alarm system  10  generally includes a seat belt sensor assembly  12 , a vehicle status sensor assembly  14 , a power source or battery  16 , and an audible alarm generator or horn  18 . The alarm generator  18  is typically the horn of the vehicle, but may also be a key fob, cell phone, vibrating alarm, or the like. 
     As shown schematically in  FIGS. 1 and 2 , the safety alarm system  10  includes a seat belt status sensor assembly  12  connected to a seat belt  20  to be worn by a child passenger. The seat belt  20  typically includes a first belt portion  22  and a second belt portion  24 . More typically, as shown in detail in  FIGS. 3A and 3B , a first buckle portion  26  is connected to the first belt portion  22  and a second buckle portion  28  is connected to the second belt portion  24 . The sensor assembly  12  is typically operative to generate a first signal when the seat belt  20  is fastened (i.e., the buckle portions  26 ,  28  are engaged with each other) and a second signal when the seat belt  12  is unfastened (i.e., the buckle portions  26 ,  28  are disengaged from each other). 
     Referring again to  FIGS. 3A and 3B , the sensor assembly  12  includes status signal generator  32  coupled to one seat belt buckle portion  26 ,  28  and a receiver  34  coupled to the other seat belt buckle portion  28 ,  26  such that a short range signal generated by the signal generator  32  may be detected by the receiver  34  when the seatbelt  12  is latched. The signal generator  32  and receiver  34  are connected in electric communication with the power source  16 ; the receiver  34  is likewise in electric communication with the horn  18 . The system  10  further includes an engine status sensor assembly  14  operationally connected to the vehicle&#39;s engine or ignition for providing a first engine status signal when the engine is running and a second engine status signal when the engine is turned off. The first and second engine status signals may both be positive signals, or one may be a null signal. 
     Referring to  FIG. 4 , one possible circuit diagram for a first embodiment alarm system  10  of the present invention is shown in detail. The circuit diagram includes two (2) subassemblies—a signal generator/transmitter subassembly  32  and a receiver/alarm subassembly  34 . The signal generator/transmitter subassembly  32  includes a first resistor  40  electrically connected to a first node  42 . A second resistor  44  is electrically connected between the first node  42  and a second node  46 . A third resistor  48  is electrically connected between the second node  46  and a first voltage source  50 . A fourth resistor  52  is electrically connected between the second node  46  and a ground potential  54 . A first operational amplifier (op amp)  58  is provided having a noninverting input  60  electrically connected to the first node  42 , an inverting input  62  electrically connected to a third node  64  and an output  66  electrically connected to a fourth node  68 . A fifth resistor  70  is electrically connected between the third node  64  and the fourth node  68 . A first capacitor  72  is electrically connected between the third node  64  and ground  54 . A second capacitor  74  is electrically connected between the fourth node  68  and a first inductor  76 ; the first inductor is electrically connected between the second capacitor  74  and ground  54 . 
     The receiver/alarm subassembly  34  includes a sixth resistor  80  electrically connected between a second voltage source  82  and a fifth node  84 . A seventh resistor  86  is electrically connected between the fifth node  84  and ground  54 . An eighth resistor  88  is electrically connected between the fifth node and a sixth node  90 . A ninth resistor  92  is electrically connected between the sixth node  90  and a seventh node  94 . A second op amp  96  is provided having a noninverting input  98  electrically connected to the sixth node  90 , an inverting input  100  electrically connected to an eighth node  102  and an output  104  electrically connected to the seventh node  94 . A tenth resistor  106  is electrically connected between the seventh node  94  and the eighth node  102 . A third capacitor  108  is electrically connected between the eighth node  102  and ground  54 . An eleventh resistor  110  is electrically connected between the seventh node  94  and the base  112  of a first transistor  114 . The transistor further includes an emitter  116  electrically connected to ground  54  and a collector  118  electrically connected to one terminal  120  of a speaker  122 . The speaker  122  includes a second terminal  124  electrically connected to a third voltage source  126 . 
     A second transistor  130  is provided, and includes a drain  132  electrically connected to the sixth node  90 , a source  134  electrically connected to ground  54 , and a gate  136  electrically connected to the output  138  of a third op amp  140 . The third op amp  140  also includes a noninverting input  142  electrically connected to a ninth node  144  and an inverting input  146  electrically connected to a tenth node  148 . A twelfth resistor  150  is electrically connected between the ninth node  144  and a fourth voltage source  152 . A thirteenth resistor  154  is electrically connected between the ninth node  144  and ground  54 . A third transistor  156  is provided having a drain  158  electrically connected to the tenth node  148 , a source  160  electrically connected to ground  54 , and a gate  162  electrically connected to the vehicle ignition sensor assembly  14 . 
     A fourteenth resistor  166  is electrically connected between the tenth node  148  and an eleventh node  168 ; a fifth voltage source  170  is electrically connected to the eleventh node  168 . A fourth capacitor  172  is electrically connected between the tenth and eleventh nodes  148 ,  168 . A fourth transistor  176  is provided, and includes a drain  178  electrically connected to the tenth node  148 , a source  180  electrically connected to ground  54 , and a gate  182  electrically connected to the output  184  of a fourth op amp  186 . The fourth op amp  186  further includes a noninverting input  188  electrically connected to a twelfth node  190  and an inverting input  192  electrically connected to a thirteenth node  194 . A fifteenth resistor  196  is electrically connected between the thirteenth node  194  and ground  54 . A sixteenth resistor  198  is electrically connected between the twelfth node  190  and ground  54 . A seventeenth resistor  200  is electrically connected between the twelfth node  190  and a sixth voltage source  202 . A fifth capacitor  204  is electrically connected between the thirteenth node  194  and ground  54 . A first rectifying diode  206  is electrically connected between the thirteenth node  194  and a fourteenth node  208  and is oriented to allow current to flow from the fourteenth node  208  to the thirteenth node  194 . A second inductor  210  is electrically connected between the fourteenth node  208  and ground  54  and a sixth capacitor  212  is electrically connected between the fourteenth node  208  and ground  54 . 
     In operation, the seat belt sensor assembly  12  operates to generate a “seatbelt fastened” signal when the seatbelt  20  is buckled (i.e., when the buckle portions  26 ,  28  are engaged) and the vehicle status sensor assembly  14  operates to send a “vehicle off” signal when the vehicle is turned off or deactivated (such as when the motor is not running or when the ignition is off). When these two conditions coincide for a predetermined amount of time, the audible alarm generator  18  is actuated. The alarm generator  18  is deactuated when either the vehicle is restarted or the seatbelt  20  is unfastened. Thus, when a child passenger is left in a (presumably) parked and deactivated vehicle for more than a predetermined amount of time, the alarm  18  will sound to signal for help. 
     More specifically, the first embodiment of the present invention includes the signal generator/transmitter subassembly  32  which typically functions as a low power oscillator and transmitter antenna combination that creates and transmits an electromagnetic field that the receiver  34  can sense when the seatbelt  20  is latched (i.e., when the buckle portions  26 ,  28  are sufficiently near one another for the signal to be received). This can be the seatbelt  20  from the baby seat, a booster seat, the automobile&#39;s OEM seatbelt system, or the like. As stated above, the field generator subassembly  32  is typically located in one portion  26 ,  28  of the seat belt latch or buckle and the receiver subassembly  34  is typically located the other portion  28 ,  26  of the seat belt latch or buckle. The electromagnetic field generator  32  consists of an oscillator sub-circuit  220  (i.e., the op amp  58  and its surrounding components) and the first resonant tank  222  (i.e., the capacitor  74 /inductor  76  pair). The oscillator circuit  220  couples to the first resonant tank  222  and generates a magnetic field at the resonant frequency determined by the values chosen for the capacitor  74  and the inductor  76  elements. This resonant tank  222  is tuned to the frequency of the oscillator (F osc ) according to the relation 
             Fosc   =     1   /     L1C1             
where L1 is the inductance of inductor  76  and C1 is the capacitance of capacitor  74 . The second inductor  210  and the sixth capacitor  212  pair to form a parallel resonant tank  224  that may receive the electromagnetic field generated by the signal generator  32  when in reasonable proximity thereto. Reception of the signal from the generator  32  by the receiver  34  is taken to mean the belt  20  remains latched and, by extension, the child passenger is taken to still remain in the vehicle (although the signal may be received if the buckle portions  26 ,  28  are unlatched but in close proximity to one another, a false positive reading so generated errs on the side of child safety). The electromagnetic field from the generator subassembly  32  diminishes in intensity in proportion to the third power of distance. As both tanks  222 ,  224  are in tune with one another (typically to the frequency of the oscillator  220 ), such tuning (in conjunction with the strong signal dependence on proximity) minimizes the possibility of false triggering (that is the alarm going off when the buckle portions  26 ,  28  are not coupled).
 
     The first diode  206  and the capacitor  204  operate together to rectify the AC (F osc ) waveform from the receiving antenna (i.e., inductor  210 ). The voltage of the rectified waveform is compared to a fixed reference voltage generated by the voltage divider defined by resistors  198  and  200 . If the rectified signal received by the receiver subassembly  32  has a higher voltage than the reference voltage (this is the condition when the belt  20  is buckled), then the comparator  140  output is low (and the belt  20  is assumed to be latched). Transistors  156  and  176  operate together to represent the alarm logic assembly  228 . If either gate  162 ,  182  is high, the shared drain load resistor  166  is pulled low (that is the respective drains  158 ,  178  are pulled essentially to ground potential  54 ). On the other hand, both gates  162 ,  182  need to be low for the drains  158 ,  178  to be held at Vcc  170  (both transistors  156 ,  176  off). On the transition between these states, the node  148  that the drains  158 ,  178  share drifts from ground  54  to Vcc  170  at a rate determined by circuit elements resistor  166  and capacitor  172  operating together. This transition begins when the output of op amp  140  is low (this means the belt  20  is still connected) and the signal from the ignition  14  is low (this means the vehicle&#39;s ignition  14  is off). 
     When those conditions are met, the voltage at the drains  158 ,  178  rises according to the following equation: 
             V142   =     Vcc   ⁡     (     1   -     ⅇ       -   t     /   R166C172         )             
When this voltage (V 142  is defined as the voltage on the noninverting input  142  of op amp  140 ) exceeds that of the voltage divider element (defined by resistors  150  and  154 ), op amp  140  changes state by switching its output from high to low. This turns on the oscillator formed by op amp  96  and its surrounding circuitry (designated oscillator  230 ). The oscillation frequency of oscillator  230  is in the audible range and is fed to the speaker/horn/sound generator  18  by the current amplifier element  114 .
 
     Circuit elements resistor  166  and capacitor  172 , in conjunction with resistors  150  and  154 , operate together to define a timer  236 . The values of the timer  236  circuit elements resistor  166  and capacitor  172  (as well as the values of resistors  150  and  154 ) determine the predetermined time interval that must elapse before the alarm sounds and may be chosen to have the alarm go off any time between seconds and tens of minutes after the alarm condition is met (i.e., the ignition  14  is off and buckle portions  26 ,  28  of the passenger seat belt  20  remain connected). Changing either condition (ignition  14  on or belt portions  26 ,  28  disconnected) resets the timer  236  such that the full timer interval will have to pass after the trigger event for the alarm to go off. Restoration of the ignition  14  (car on) or unlatching the belt  20  resets the alarm. 
       FIG. 5  relates to a second embodiment circuit of the present invention, a flow diagram relating to the logic for a digital control circuit  300 . The logic flows as follows: the program is initiated by a start  302  event, such as activation of a microprocessor or energizing the circuit. The circuit first queries  304  whether or not the seat belt buckle portions  22 ,  24  are coupled, i.e., whether the receiver  34  is receiving a first signal from the signal generator/transmitter  32 . If no  306  (i.e., the first signal is no longer received), the logic returns to repeat the first query  304 . If yes  308 , the circuit performs a second query  310  to determine whether the vehicle engine is on, i.e., whether a first status signal is being received from the vehicle sensor assembly  14 . If yes  312 , the logic returns to repeat the first query  304 . If no  314 , the logic proceeds to initiate the alarm timer  316 , which is set to generate an elapsed time signal  318  after a predetermined period of time has elapsed. The logic next generates a third query  320  to determine if the seat belt buckle portions  22 ,  24  remain coupled, i.e., whether the receiver  34  is still receiving a first signal from the signal generator/transmitter  32 . If no  322  (i.e., the first signal is no longer received), the logic returns to repeat the first query  304 . If yes  324 , the logic generates a fourth query  326  to check whether the timer has timed out (i.e., whether the timer  316  has completed its count sequence and an elapsed time signal  318  has been generated). If no  328 , the logic returns to repeat the third query  320 . If yes,  330 , the logic generates an actuation signal  332  to the alarm device  18 . The logic then proceeds to generate a fifth query  334  to determine whether the alarm system  10  was reset. If no  336 , the logic returns to the fifth query  334 . If yes  338 , the logic returns to the first query  304 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the invention are desired to be protected