GB2090033A - Vehicle Anti-theft System - Google Patents

Abstract

Antitheft device incorporating a sequential logic circuit or path so arranged that it automatically sets or arms when a protected space such as a vehicle is vacated and the last opening member such as a door is shut. And gate 26 is fed from three flip flops 20, 22 and 24, 22 also sets 24 and through 28 helps to activate 20. 20, 22 and 24 are all reset from (C). By delaying the signal from (A) in two places (16 and 18) and gates 28 and 30 respond to combination signals (B+A) in the required manner activating 22 and hence 24 which with 22 Q locked in high leaves 28 to monitor any change in signal (A). When 28 receives two high signals it triggers 20 which sends 20Q high and locks. Three locked signals to 26 send the alarm signal. And gate 32 prevents alarm setting after disarm if a body is on the seat. And gate 34 monitors the armed state. <IMAGE>

Description

SPECIFICATION Anti-theft System for a Vehicle The present invention relates to an alarm system which can be installed in a vehicle, such as a motor car, so as to activate an alarm when the vehicle is opened by an unauthorised person.

In known types of alarm systems, it has always been necessary to set the alarm by means of a key or similar means possessed by the authorised user of the vehicle, and this has had the disadvantage that the driver using the car may forget to set the alarm before he leaves it.

According to the present invention in its broadest aspect, there is provided a system for installation in a motor vehicie, which comprises a signal device tobe attached to each door or other opening member of the vehicle to sense the closing of that member, a device to sense the presence of a person in the driving seat, and a sequential logic circuit, having inputs for receipt of signals from the aforesaid devices, the circuit being arranged to activate an alarm signal when any opening member of the vehicle is opened after the circuit has been activated or "set", the circuit being set when the last opening member is closed and the device does not sense any person being present in the driver's seat at the time that the last member is closed.

The device for attachment to the opening members (such as doors, sliding roof, boot, bonnet or tailgate) of the vehicle can be a switch.

The device to sense the presence of a person in the driver's seat can be conveniently a switch actuated by a pressure pad under the seat, but other means such as a photoelectric cell or ultrasonic sensor could be used.

The logic circuit is set or armed when the last door of the vehicle is closed, except when at the time of the door closing a person is sitting on the driver's seat, but it is designed not to set when the alarm would not be desired to be set, for instance when the driver takes his weight temporarily from the driver's seat having previously shut the door whilst sitting on the seat.

If the driver disarms the alarm and opens the door, then sits on the seat and gets up from the seat to shut the door from the outside, the alarm will set as he shuts the door, assuming that no other door is open.

Most importantly, if the alarm has been set or armed by the shutting of the last door whilst the driver's seat is unoccupied it will not be disarmed by the subsequent application of weight on the driver's seat by, for instance, an occupant left in the car, be this dog, child or adult.

If the alarm is triggered or fired so that the alarm is sounded it cannot be turned off by shutting the door or sitting on the seat as it locks on until disarmed by a pulse generated from a key, switch or other signal device such as microwave, radio or similar sensing device. In practice it is sensible to limit the duration of the time that the alarm sounds by the addition of a timing circuit which resets the alarm after about five to seven minutes (not shown in the circuit).

The logic circuit can be constructed from known integrated circuit (I.C.S.) components comprising "and" gates, flip flops, inverters and schmit triggers, which are activated only by high or low electrical signals.

The audio alarm signal can be the horn of the vehicle.

The logic circuit can be arranged, for maximum security, in the boot of the car in a separate locked compartment and fed from a separate battery (which may be charged from the vehicle's engine), and may have a separate buzzer as an additional alarm.

Preferably a pair of signal lights (e.g. red and green) are provided inside a window to indicate to the user whether the alarm is set. A key (or magnetic pad) is used to deactivate the alarm before a door is opened by the user of the vehicle.

The circuit can inciude means (including a timer) such that after the last door has been closed so as to set the alarm, the alarm signal (horn and/or buzzer) sounds for a brief period so as to confirm that the alarm system is in working order.

The invention will now be described with reference to a preferred embodiment thereof as shown in the accompanying single figure, which is a circuit diagram.

Referring to the drawing, it is seen that briefly on the left are three input signals each of which can be high or low and which originate from (A) the door signal device, (B) the seat signal device, and (C) the key (disable) signal device. In each case the signal is passed through a schmit trigger to make the signal clean and without ripples.

(Ripples can be caused by mechanical switches bouncing.) These schmit triggers are also inverters, i.e. they give an opposite signal on the output to that on the input. The schmit triggers are marked 10,12,14.

On the right are three output signals (X) The alarm signal which sounds the alarm; (Y) The alarm set or armed signal which sounds a buzzer and lights a red L.E.D. to visually indicate that the alarm is set; and (Z) A signal which lights a green L.E.D. to indicate that the alarm is disabled.

Between the input signals on the left and the output signals on the right is a sequential logic circuit which gives the results described previously.

The sequential logic circuit is basically a combination of "and" gates and flip flops, with some of the signals and combinations of signals being delayed by timing circuits so that they arrive at the components in the required order.

These timing circuits are marked 16 and 18.

"And" gates as drawn and used in this circuit will only pass a high signal to the right when the two or three inputs on the left of the "and" gate are all high.

Flip flops as used and drawn have two outputs, Q and 0. Q and Q are always opposite in value, high or low. Q will change to the same signal as that at (D) or data terminal when a high pulse is applied atthe C.P. or clock pulse terminal. Q will change to low when a low pulse is applied to the R.D. or reset terminal. The flip flops are marked 20, 22 and 24. 0 will stay at the value or signal passed until a pulse as described is applied at either C.P. or R.D.

To obtain a high signal at (X), the alarm signal, all three inputs to the left of "and" gate 26 have to be high, as drawn the top one from flip flop 20 terminal 0 is in effect the signal which fires the alarm.

On flip flop 20 terminal D is permanently connected to high. When a high pulse is applied to C.P. the output at O will lock high, when a low pulse is applied to R.D., O will lock low. To obtain a high pulse at C.P. "and" gate 28 has to have two high inputs on the left. One of these inputs comes from the door signal (A) and is the same as the door signal (having been inverted twice through 10 and 38). The other input comes from the output from flip flop 22 (output Q). As the output from flip flop 22 Q is the result of a high signal at the C.P. terminal on 11 (D connected as in 20), which in turn comes from "and" gate 30 which in turn is a combination of a signal from the door (A) and the seat (B) (due to a triple inversion 10, 1 6 (timer) and 40 a low signal at (A) gives a high signal at the top of 30).A low signal at (B) (off seat) inverted at 12 gives high at "and" gate 32 which is met by a delayed high signal from (A) through timer 1 8. This then gives a high at the bottom of 30 and therefore a high on the right of 30 and at C.P. of 22, Q of 22 and bottom of "and" gate 28 and locked to the middle of "and" gate 26. It can be seen, therefore, that as the door shuts and if the driver's seat has no weight on it that flip flop 22 locks with output 0 at high. This high signal fulfuls a number of functions as follows: To partially arm "and" gate 26; To partially arm "and" gate 28; To partially arm "and" gate 34; and To apply a positive clock pulse to flip flop 24.

Flip flop 24 has the signal inverted from the seat applied at terminal D (data). So, when no one is on the seat, a high signal is applied at D (data).

It follows that when the door shuts with the seat empty the resultant high at the clock pulse terminal gives a high at 0 24. This signal is then locked and goes to the bottom of "and" gate 26 and to the bottom of "and" gate 34. When this sequence has been completed "and" gate 26 has two highs locked on and is awaiting a high from flip flop 20 to fire the alarm. "And" gate 34 has two highs which allow a high to light the red L.E.D. and sound the buzzer for a short period.

This period is determined by timer 36. The red L.E.D. stays on to indicate that the alarm is set (Y).

To disarm the alarm a high signal from (C) is inverted and fed into each R.D. (reset) terminal on 20, 22, 24, 16, 18, 36. This disarm signal on flop flop 24 will put a high toO which is fed to a green L.E.D. (Z) to indicate that the alarm is disarmed.

The red L.E.D. (Y) is extinguished at this time.

The three illustrated flip flops and two timers have been marked with the commercial designations 7474 and 555 respectively, but any equivalent components can be used.

The same logic path can also be implemented using a microprocessor in place of the above integrated circuit components.

Claims (12)

Claims

1. An antitheft device incorporating a sequential logic circuit or path which monitors the status of the opening members e.g. the doors of a protected space such as a vehicle and the presence or absence in the protected space of a body, and which will automatically set or arm when the space is vacated and the last opening member is closed and which can be disarmed by a pulse generated from a security key and lock, magnetic pad or other method of pulse generation, and which will trigger or fire (when set) when an opening member is opened before the device has been disarmed.

2. A device as claimed in claim 1 which locks or latches on when triggered or fired.

3. A device as claimed in claim 1 which having been triggered or fired will automatically reset or rearm after a preset period if the protected space is vacated and the opening members are closed.

4. A device as claimed in claim 1 which holds its 'set or armed' state unless triggered or fired even if the monitored conditions inside the protected space alter after the device has set or armed and before it is legally disarmed.

5. A device as claimed in claim 1 which does not set or arm when the device has been legally disarmed and the protected space entered until the protected space has been vacated again and the last opening member closed, regardless of the entering body's actions whilst in the protected space.

6. A device as claimed in claim 1 which when triggered or fired generates a signal which can operate a) its own attention attracting devices and/or b) remote attention attracting devices and/or c) identification devices and/or d) immobilisation devices

7. A device as claimed in any one or all of the claims 1 to 6 which uses a sequential logic circuit or path constructed or generated using integrated circuits and discrete components either on their own or with microprocessors or with microprocessors singular or in a plurality to generate the sequential logic path.

8. A device as claimed in any preceeding claim which is powered by its own battery or power supply.

9. A device as claimed in any preceeding claim which is protected by its own lockable compartment.

10. A device as claimed in any preceeding claim which uses contact switches, ultrasonic sensing devices, infrared sensing devices, microwave sensing devices, light sensing devices, or any other sensing devices in any combination singularly or as a plurality to activate the sequential logic path.

11. A device as claimed in any preceeding claim which has a visible or audio or other generated signal to indicate the logic state.

12. The improvement claimed over existing alarm circuits lies in the sequential logic path referred to in claims 1 to 11 as characterized by the path taken by the logic in the sequential logic circuit in Figure 1 and is shown as such for clarity.

The same logic path can readily be generated in a microprocessor and claim is laid for both such methods of generation.

N.B. The word 'legally' has been used in the context of 'authorised disarming of the alarm'.