GB2121108A

GB2121108A - Preventing unauthorised use of i.c. engines

Info

Publication number: GB2121108A
Application number: GB8315242A
Authority: GB
Inventors: Colin Rochard Moitie
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-03
Filing date: 1983-06-03
Publication date: 1983-12-14
Also published as: AU1524983A; GB8315242D0

Abstract

The engine ignition circuit is rendered inoperative when, with a switch 10 operative, a switch 14, responsive to build-up of manifold vacuum or attainment of a predetermined engine speed after starting, is operated. The switch 14 may be operated by a diaphragm (17, Fig. 1) in a vacuum chamber 18 with an adjustable air bleed (21). <IMAGE>

Description

SPECIFICATION Anti-start devices for electrical ignition, e.g. to prevent theft.

This invention relates to anti-start devices for eiectric-ignition engines. Such devices are primarily intended to prevent or deter theft in the case of vehicle engines, or merely as safeguard against unauthorised starting, in the case of stationary engines.

The present invention is almost wholly concerned with car engines and the problem of car theft, and therefore will be described herein primarily in terms of that specific application.

An obvious object of the invention is to prevent a car engine from being started so as to deter theft. A iess obvious but equally important object is to confuse the intending thief by making it appear that the engine's ignition system is intact and fully operative, notwithstanding the thief's inability to get the engine running, thus to reduce the possibility of damage to engine wiring, the engine itself and the vehicle structure.

This confusion is established by reason of the device subject hereof enabling the car engine, upon closure of its ignition circuit, to start turning over and possibly fire, but then almost immediately go dead.

In summary, the invention provides an antistart device for engines having an electrical ignition circuit; said device comprising: a sub-circuit connected to said ignition circuit so as to leave said ignition circuit in normal operative condition at least until the engine starts turning over, and switch means in said sub-circuit which operate in response to initiation of rotary motion on the part of said engine in consequence of an attempted starting thereof, to render said ignition circuit inoperative.

Examples of the invention are illustrated, mainly diagrammatically, in the drawings herewith.

Fig. 1 is a sectional side elevation showing switch means and vacuum operated means governing actuation thereof.

Fig. 2 is a wiring diagram which includes the matter of Fig. 1 and shows the circuiting means in readiness for an authorised engine start.

Fig. 3 substantially repeats Fig. 2 except for showing the system in relation to a vehicle bulkhead and so conditioned as to be armed against unauthorised starting.

Fig. 4 shows a simplified arrangement, in armed condition as in Fig. 3, which can be installed in a vehicle without any alteration of its existing wiring arrangements.

Referring to Figs. 1 and 2, the ignition circuit runs conventionally from battery 5, starter switch 6, induction coil 7 and distributor 8. The circuit includes main switch 9 as one pole of a two-pole switch 10. The other pole of this switch is a warning switch 11, and the two switches are jointly operable by pressing a concealed pressbutton or by use of a second "ignition" key for use in a hidden key-hole location on the vehicle.

With the parts conditioned as indicated in Fig.

2, the engine may be started in usual fashion by closure of ordinary ignition switch 6. Switch 11 being closed causes warning light 12 to be illuminated thus telling the driver that the theftdeterrent means are "off".

The sub-circuit 1 3 includes a normally-closed switch 14 which is preferably a micro switch as indicated in Fig. 1. Switch 14 is operable by a rod 1 5 slidable in casing 16 and is mounted on a flexible diaphragm 1 7 which constitutes one wall of a vacuum chamber 18. This chamber 18 is pipe-connected (1 9to the intake manifold of the engine, or other part thereof subject to pressure reduction in consequence of engine turn-over.

Switch 1 4 is normally kept closed by compression spring 20, and chamber 18 is furnished with an adjustable bleed valve 21 which, following loss of air pressure in chamber 18 enables ambient pressure to be re-established therein (so closing switch 14) at some selected slow rate.

Virtually the same arrangement as that described above is repeated in Fig. 3 except for inclusion of vehicle bulk-head 22 and the showing of switch 10 in deterrent position. That is, with main switch 9 closing sub-circuit 13 and opening switch 11 so that light 12 is out so signifying that the deterrent is "on".

If starter switch 6 is now closed, the distributor 8 will be energised, thus to cause the engine to start turning over; but as soon as this motion of the engine creates a sufficient vacuum in chamber 18 as will cause the diaphragm to open switch 14 (against the loading of spring 20) the ignition circuit is thus opened and the engine then goes dead.

It will be appreciated that vacuum operation of a switch such as 14 is a preferabie way of opening the ignition circuit when required; however, there are other ways in which this switch may be opened. For example an ordinary engine centrifugal governor may be used so that switch 14 will be opened in response to the engine reaching a selected speed upon an attempted start.

Fig. 4 shows a system which is much the same as that described in relation to Figs. 1 to 3 in that it includes the items numbered 5 to 1 2 in Figs. 1 to 3. The main difference is that in the earlier form of the invention opening of the switch 14 opened the circuit of distributor 8 whereas in the Fig. 4 arrangement, virtually the same thing is effected by shorting the induction coil 7 directly to earth.

This will be apparent from Fig. 4 where the switch 10 has been left in armed condition so that lamp 12 is off as described in relation to Fig. 3. If the ignition switch 6 is now closed the engine will start turn-over so creating a vacuum in chamber 1 8 so that switch 14 is actuated to earth the coil 7 by way of sub-circuit consisting of parts 23, 24 and 25.

It will be appreciated that while the invention is described herein in terms of petrol-powered engines, it is equally applicable to gas engines, or engines fuelled otherwise than by petrol; provided they include an electrical ignition system for firing.

Claims

1. An anti-start device for an engine having an electrical ignition circuit; said device comprising: a sub-circuit connected to said ignition circuit so as to leave said ignition circuit in normal operative condition at least until the engine starts turning over, and switch means in said sub-circuit which operate in response to initiation of rotary motion on the part of said engine in consequence of an attempted starting thereof, to render said ignition circuit inoperative.

2. An anti-start device according to claim 1 wherein said switch means are operated to render said ignition circuit inoperative in response to a vacuous condition established by turning-over of said engine.

3. An anti-start device according to claim 1 wherein said switch means are operated to render said ignition circuit inoperative in response to turning-over of said engine at a selected minimum -speed.

4. An anti-start device according to claim 2 wherein said switch means are operated by a spring-loaded rod mounted on a flexible diaphragm forming one wall of a vacuous chamber pipe-connected to a vacuum-providing portion of said engine.

5. An anti-start device according to claim 4 wherein said vacuous chamber is furnished with a bleed valve which, following reduction of pressure within said chamber allows ambient pressure to be re-established therein.