Patent GB-1180950-A (GB)
Title: Machine Immobilisation Device.
Inventor: HANNAM PETER
IPC: A61B5/18
Filed: 1967-10-17
Abstract: 1,180,950. Determining reaction times. P. HANNAM. 17 Oct., 1968 [17 Oct., 1967], No. 47247/67. Heading A5K. [Also in Divisions F1 and F2] A device for preventing starting of a motor vehicle engine, or other machine, if the reaction time of an operator exceeds a predetermined value, (e.g. 0.3 secs.) comprises electronic circuitry arranged so that a visual or other signal is given to the operator at a random time interval after actuation of an ignition switch, the engine or machine being prevented from starting if the operator does not actuate the starter switch within the predetermined time after the signal. In the case of a motor vehicle, the device is arranged so that should the engine stall or fail to start even though the driver has successfully passed the reaction test, he can attempt to restart the vehicle within a predetermined interval (e.g. 10 mins.) without further tests. The circuitry of the device comprises an ignition switch A1 which when operated energises a transistor mono-stable circuit or trigger pulse generator A2 which in turn provides a pulse to rotate the shaft of an electric motor A3 through an appreciable angle. Associated with the motor is an oscillator B2 whose frequency is controlled by several iron-cored coils B1 connected in series and/or parallel, the coils being mounted radially inside a cylindrical casing and the number of turns on the coils differing from each other. The shaft of the motor 3A sweeps a magnetic element, e.g. a magnet or ferromagnetic core, over the coils B1 so that the total inductance, and thus the frequency of the oscillator B2, depends upon the stopping position of the magnetic element. The oscillator frequency is therefore random and unpredictable in all circumstances. The output of the oscillator B2 is fed to a pulse counting or frequency discriminator B3 which provides a voltage output proportional to the oscillator frequency. The voltage output is fed to a timer B4 comprising a resistorcapacitor circuit connected to control the conduction of a transistor. The time taken by the capacitor to charge sufficiently to allow the transistor to conduct after operation of the ignition switch Al will depend on the time constant of the R-C combination and the output voltage of the discriminator B3. When conduction occurs, the timer B4 simultaneously energises an indicator lamp B5, to provide a signal to the driver, and a reaction timing device B6 and sends an "ON" signal to a logic switch device B7. The reaction timer B6 comprises an R-C circuit for controlling the conduction of a transistor, the time constant of the R-C circuit being about 0.3 secs., i.e. the maximum reaction time for safe driving. When conduction occurs, the reaction timer B6 transmits an "OFF" signal to the logic switch B7. The latter is a transistor switching circuit which passes the "ON" signal from timer B4 to energise a monostable transistor circuit B8 providing the "OFF" signal from reaction timer B6 is not present or is overridden. The monostable circuit B8 is connected to be triggered by a pulse from a single shot pulse generator B9, and thereupon to pass a pulse of ample duration to start the car engine to a silicon control rectifier circuit B10 connected to the engine starter motor. The pulse generator B9 provides a single pulse each time the starter switch is operated, and providing the driver effects this operation before the "OFF" signal de-energises monostable circuit B8 (i.e. within about 0.3 secs. after the lighting of lamp B5) the starter motor will rotate to start the engine. The pulse generator B9 comprises a parallel-tuned LC circuit shunted by a diode and connected in series with the transistor energised by the starter switch. The S.C.R. circuit B10 includes an R-C. circuit having a time constant of 600 sees and a relay arranged so that when the monostable circuit B8 transmits a starting signal to the S.C.R. circuit the relay closes causing the capacitor to charge substantially instantaneously. When B8 returns to its quiescent state, the relay disconnects the power supply from the capacitor and the R-C circuit sends an "off-cancelling" signal to the logic switch B7 for about 10 minutes. Thus any "OFF" signal from the reaction timer B6 is overridden so that if the engine fails to start at the first attempt, providing the driver has passed the reaction test, further attempts can be made to start the engine within the 10 minute period without taking further reaction tests. An R-C circuit B11 is is connected to receive a voltage from the engine driven dynamo so that the capacitor is charged when the engine starts. The time constant of the circuit is again 600 secs. so that, when the capacitor is charged the circuit maintains an "off-cancelling" signal at the logic switch B7. Thus the engine can be restarted within a 10 minute period without further reaction tests if it stalls. The pulse generator B9 may also be connected to the logic switch B7 in such a way that the switch B7 cannot energise the monostable circuit B8 unless the switch receives the "ON" signal from timer B4 before receiving a signal from the pulse generator B9. This arrangement would prevent an incapable driver from starting the engine by repeatedly operating the starter switch before he sees the indicator lamp B5 light. In applications to machines other than vehicle engines, the lamp B5 could be replaced by an indicator giving signals with heat, sound, electricity, or magnetism.