Tyre pressure alarm equipment incorporating a magnetic responsive element

Claim 1

66 328n4 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Tyre pressure alarm equipment comprising a transmitter, for mounting on a wheel rim of a vehicle and so constructed as to produce changes in outwardly radiated magnetic flux when the air pressure of the tyre is lowered below a prescribed value, a magnetic responsive element, sensitive to said magnetic flux, a casing for housing for said magnetic responsive element, consisting of non-magnetic material and intended for mounting on a station- ary part of a vehicle, adjacent to the wheel rim, said magnetic responsive element being arranged within the casing of non-magnetic material so that it will not be in contact with the casing, the space between said element and the casing being filled with an electric insulating filler, said filler having a buffer action against a shock, said magnetic responsive element including or having connected thereto a lead wire which is arranged within said casing and a hardenable electric insulating filler fills the space within'the casing around the lead wire an&dan actuating circuit, connected with said magnetic responsive element for controlling an alarm device for indication of the lowering of the air pressure in the tyre below the prescribed value such that when the air pressure in the tyre is lowered below a prescribed value the change in magnetic flux causes said magnetic responsive element to become conductive and thereby send a signal to said actuating circuit which in turn energises the alarm device which indicates the said air pressure in the tyre is below the prescribed value. 21. 486,277 66 328 n74 2. Tyre pressure alarm equipment according to claim 1, wherein the filler includes a pipe of electric insulating soft material fitted around the magnetic responsive element. 3. Tyre pressure alarm equipment according to any one of claims 1 or 2 wherein the magnetic responsive element is mounted between an insulating plate and the inner face of the casing, and is connected with a lead wire passing through said insulating plate. 4. Tyre pressure alarm equipment according to any one of claims 1 to 3, wherein a bracket is provided for clamping said casing, and a lead wire for connet.i.ng said magnetic responsive element with the actuating circuit to the stationary part of the vehicle. Tyre pressure alarm equipment according to any one of claims 1 to 4, wherein said magnetic responsive element is a generator coil, a magnetic diode, or a hall generator. 6. Tyre pressure alarm equipment according to any one of claims 1 to 5, wherein said magnetic responsive element is a reed switch. 7. Tyre pressure alarm equipment, according to claim 6 wherein said actuating circuit includes a thyristor, the gate of which is connected with on end of said reed switch, while one end of the alarm device and the anode of the thyristor are connected with the other end of said reed switch, so that almost no current will flow through the reed switch when the reed switch is closed and the alarm device will be actuated by the turning-on of the thyristor. 22 486,277 66 328 74 8. Tyre pressure alarm equipment according to claim 7, wherein a condenser is connected in parallel between the anode and the cathode of said thyristor, so that when the reed switch is closed, a discharge current will flow from said condenser to the gate of the thyristor through the reed switch to help the turning-on of the thyristor. 9. Tyre pressure alarm equipment according to claim 7 or claim 8 wherein a circuit for causing the gate .to be actuated only by intermittent switching of the reed switch is inserted between the reed switch and the gate of the thyristor. Tyre pressure alarm equipment according to claim 9, wherein said multiple switching circuit is an integrating circuit. 11. Tyre pressure alarm equipment according to any one of claims 1 to 10 wherein the said stationary part of a vehicle is the back plate of a brake drum or the buffer plate of a disc brake. DATED this 28th day of July, 1977. KANTO SEIKI CO. LTD. By its Patent Attorneys: CLEMENT HACK CO. Fellows Institute of Patent Attorneys of Australia. 23 486,277 66-3 28 n4 Ila 11 ~A)2 19a 3b1 3I~j 25 4 86277 66 328n4 43 27 27 4 86277 6 612 8 n4. Cc cc Ln do C-1 ce C=l Cj -29 9~4 8 6,277