Abstract:
A vehicle anti-theft device for controlling the operation of an electric fuel pump in the fuel tank of motor vehicles which includes a relay that is located in the fuel pump assembly and controlled by a radio-frequency receiver. The radio frequency-receiver is controlled by an input signal transmitted from a hand-held remote transmitter. As a safety precaution, an under-dash relay is provided so that system switching can only occur when the ignition switch is off. The relay in the fuel pump assembly also controls the illumination of an indicator light in the dashboard of the vehicle which indicates fuel pump status to the vehicle operator. Also mounted in the dashboard of the vehicle is an emergency plug into which the hand-held remote control transmitter can be inserted if the battery therein runs down.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to vehicle anti-theft devices and more particularly to a device which selectively disables the fuel pump of a motor vehicle. 
     Anti-theft devices for motor vehicles that include dash-mounted remote keypads with associated harness and fuel cut-off valves are known in the art. Such anti-theft devices require an operator of a motor vehicle to memorize a numeric code that has to be punched into the keypad. Moreover, such devices can include functional components such as cut-off valves that may be accessible to thieves who would have the opportunity to circumvent or disable the anti-theft devices. 
     The present invention provides an motor vehicle anti-theft device that includes a transmitter operated relay unit that is installed in the fuel pump housing of a vehicle and is therefore in the fuel tank and inaccessible to thieves. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a simple and cost-effective method of effecting complete immobilization of a vehicle so as to prevent theft of the vehicle. The invention involves the use of electronic circuitry similar to that utilized in present-day vehicles. The unit would be installed in the fuel pump assembly housing of a vehicle having the fuel pump in the fuel tank. The invention provides a simple means of shutting down the fuel supply to the engine of a vehicle without requiring a dash-mounted remote keypad (with associated harness) or a fuel cut-off valve, as required in previous anti-theft devices. 
     The supply voltage used to turn the fuel pump on or off would be controlled by electronic circuitry all contained within the fuel tank. Therefore, the anti-theft device would be essentially tamper-proof. The only recourse for a vehicle thief would be to connect a separate fuel tank and fuel pump to the engine fuel supply line, which would be prohibitive, messy, dangerous and time consuming. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The operation of the anti-theft device can be understood with reference to the following drawings: 
     FIG. 1 is an overall block diagram of the anti-theft device according to the present invention; 
     FIG. 2 is the schematic diagram of the under-dash relay circuit; 
     FIG. 3 is a schematic diagram of the circuitry enclosed within the fuel pump assembly housing in the fuel tank; 
     FIG. 4 is a diagram of the hand-held remote transmitting unit showing the emergency auxiliary power plug provided in the dash of a vehicle; 
     FIG. 5 is a diagram of the external antenna connected to the signal input of the receiver module in the fuel tank. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, the anti-theft device of the present invention includes: 
     A hand-held remote control transmitter of the type presently used to lock/unlock automobile doors and trunk lids; 
     An integrated fuel-pump relay and receiver module that are located within the fuel tank; 
     An antenna that is connected to the signal input of the receiver module in the fuel tank and located in an external location from the fuel tank; 
     Electrical leads connected to the components located within the fuel tank (four additional electrical leads than typically used for vehicles that do not include the anti-theft device of the present invention); 
     An indicator light that is mounted on the dashboard of the vehicle; and 
     A dashboard plug for receiving the hand-held remote control transmitter and supplying emergency power thereto if the batteries of the hand-held remote control transmitter should fail and/or need to be recharged. 
     In use, when the anti-theft device of the present invention is activated, power supply to the fuel pump in the fuel tank is turned off so that the fuel pump is rendered inoperative from within the fuel tank. Accordingly, the present invention does not require or effect any alterations to any of the external fuel lines (vapor, return and fuel-feed) of a vehicle. 
     Switching the fuel pump between an operative and inoperative mode is controlled using the hand-held remote control transmitter which can be conveniently carried in a handbag or pocket of the vehicle operator. According to one embodiment of the present invention, the hand-held remote control transmitter can be of a conventional design that includes buttons to lock and unlock the doors and/or trunk of a vehicle. In this embodiment, such a hand-held unit would merely include an extra button for activating/deactivating the anti-theft device of the present invention. According to another embodiment, the hand-held remote control transmitter can be a separate remote hand-held unit with a single button for activating/deactivating the anti-theft device of the present invention. 
     In the event of battery failure in the hand-held remote control transmitter when the antitheft device is activated, the operator would insert the hand-held unit onto an auxiliary plug provided on the dashboard of the vehicle. The auxiliary plug would provide the proper voltage (derived from the vehicle battery) to the hand-held unit for emergency use when the ignition is off. 
     The following explanation of the anti-theft device and its operation can be understood by referring to FIGS. 1 through 5. 
     FIG. 1 is an overall block diagram showing the anti-theft device according to the present invention. As depicted in FIG. 1, a second relay  1  is provided with input feeds  10  and  12 . As discussed in more detail below, input feed  10  is coupled to the vehicle&#39;s ignition system so that, a positive voltage is fed therethrough to second relay  1  when the vehicle&#39;s ignition system is on. When the vehicle&#39;s ignition system is off, no voltage is fed through input feed  10 . Input feed  12  is coupled to the vehicle&#39;s battery and is used to supply positive voltage to both receiver module  14  in fuel tank  16  and an indicator light  18  that is provided in the dash of the vehicle as discussed below. Second relay  1  includes an output feed  11  that is used to power receiver module  14  as discussed below. A positive voltage to indicator light  18  can be used to provide a visual signal that the anti-theft device is activated and that the fuel pump  20  is turned off. The hand-held remote control transmitter  22  depicted in FIG. 1 is used to cycle the state of first relay  2  with each successive push of button  24 . In this regard, when hand-held remote control transmitter  22  is activated, it transmits a coded signal  26  that is received by antenna  28  of receiver module  14 , as discussed below. Signal  26  is received by the receiver module  14 , via antenna  28  as indicated in FIG.  1 . 
     Receiver module  14  receives output feed  11  from second relay  1  as a positive input feed and a negative input feed  30 . The use of both positive and negative feeds to receiver module  14  allows the output feed  34  therefrom to be cycled between a positive and a negative output. The output feed  34  from receiver module  14  serves as an input feed to first relay  2 . 
     As discussed below, relay  2  includes an input feed  36  that is coupled to the vehicle&#39;s battery and is used to supply positive voltage to indicator light  18  depending on the state of first relay  2 . First relay  2  includes another input feed  38  that is coupled to the vehicle&#39;s ignition system so that, a positive voltage is fed therethrough to first relay  2 . First relay  2  also includes an output feed  40  that is connected to indicator light  18  and another output feed  42  that supplies power to fuel pump  20 , depending on the state of first relay  2 . 
     FIG. 2 is a schematic diagram of the under-dash relay circuit used according to the present invention. It is noted that first relay  1  would be the same as relays that are conventionally used in present-day vehicles. As indicated above, a positive voltage supply input feed  12  is continuously supplied from the vehicle battery to second relay  1  and a second input feed  10  is coupled to the vehicle&#39;s ignition system so that, a positive voltage fed therethrough to first relay  2  would only be present when the vehicle is in operation (when the ignition is on). A negative input feed  46  is supplied from the negative return vehicle battery voltage which is typically the chassis ground of the vehicle. The vehicle battery voltage would be within the operating voltage range of the relay coil of second relay  1 . When the vehicle&#39;s ignition is off, second relay  1  is not energized through input feed  10 . However, a positive voltage is supplied through input feed  12  to second relay  1  and across pins # 1  and # 2  and to receiver module  14  via output feed  11 . Receiver module is located in the fuel tank  16  as indicated. When the vehicle&#39;s ignition system is on, second relay  1  breaks the connection between pins # 1  and # 2  and connects pins # 1  and # 3 . In this switched configuration, voltage is disconnected from the receiver module  14  in the fuel tank  16 . Therefore, the state of first relay  2  (energized or de-energized) in the fuel tank cannot be changed when the ignition is on. If the vehicle engine is operating normally, the fuel to the engine could not be interrupted by accidently pushing the button of the hand held remote control transmitter  22 . When the ignition is off, a positive voltage supply from the vehicle&#39;s battery could be connected to an auxiliary power plug (see FIG. 4) provided in the dash for emergency use in the case of a run-down battery in the handheld remote control transmitter  22 . It could also be used to charge the battery in the hand-held remote control transmitter  22  if equipped with a rechargeable battery. 
     FIG. 3 is an electrical schematic diagram of the switching and components located in the fuel pump assembly housing in the fuel tank  16  (except for the external antenna connected to the signal input of receiver module  14 ). First relay  2  is a latching relay which would hold its lastordered state (preventing first relay  2  from de-energizing when the power supply from the receiver module  14  is removed, as when the vehicle&#39;s ignition is turned on). 
     As discussed above, the receiver module  14  receives output feed  11  from second relay  1  as a positive input feed and a negative input feed  30 . The use of both positive and negative feeds to receiver module  14  allows the output feed  34  therefrom to be cycled between a positive and a negative output. The coil of relay  2  is shown as being energized by receipt of a momentary ground from the receive module  14 . If the receiver module  14  were to be provided with a positive momentary signal, the other side of the coil would simply be connected to ground or negative voltage supply. The vehicle battery voltage should be within the operating voltage range of the relay coil of first relay  2 . 
     When first relay  2  is energized from its state depicted in FIG. 3, positive voltage supplied though input feed  36  becomes an output from first relay  2  from pin # 3  and is supplied to indicator light  18  to provide visual indication of the system state whether the ignition is on or off. Preferably the indicator light  18  would be a large flashing red display with an imprinted message, such as “DO NOT START” or “FUEL TANK LOCKED.” Here it is noted that attempting to start the vehicle engine while the fuel pump is inoperative would cause no damage—the engine would start momentarily and then quit, and it would be impossible to restart the engine. 
     When first relay  2  is de-energized, the positive voltage from input feed  38  (with ignition on) is connected to the fuel pump  20  through pins # 4  and # 5  of first relay  2 , and the vehicle engine operates in the normal manner. 
     The receiver module  14  accepts a radio frequency (RF) coded transmission from the hand-held remote control transmitter  22  and provides a single positive or negative trigger output to the coil of first relay  2 . The receiver module  14  and first relay  2  would be miniaturized and installed in the fuel pump assembly housing, which is installed inside the fuel tank  16 . 
     FIG. 4 illustrates a hand-held remote control transmitter  22  with a connecting port  48  for connecting to the auxiliary power plug in an emergency. The auxiliary power plug would provide power for the hand-held remote control transmitter  22  only when the ignition is off, as shown in FIG.  2 . 
     FIG. 5 is a diagram of the external antenna connected to the signal input of the receiver module in the fuel tank. The antenna  28  would be a stub antenna approximately six inches long and insulated outside the fuel tank  16 . It would be mounted in the trunk above the fuel tank in a concealed position. Alternatively, the antenna  28  could be mounted near the fuel tank  16  but not in the vehicle&#39;s trunk, if the trunk provided excessive RF shielding. The coaxial cable  50  connecting the antenna  28  to the receiver module  14  in the fuel tank  16  would have its outer conductor grounded to the vehicle&#39;s chassis at any point along its length. 
     Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications may be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described by the claims which follow.