Low tire pressure indicating and warning means

Claim 2

Low tire pressure indicating and warning means in accordance with claim 1 in which the hollow casing of said at least one switch is of cylindrical shape and enclosed at one end so as to afford weather and dust protection for said built-in electrical contact members and said dust cap is of an electrically conductive material, and which has an electrical conductor connecting said other electrical contact of said switch to said dust cap, whereby the flow of electric current from the switch to the metal frame of said vehicle proceeds from the dust cap through the hub of said wheel, then through the wheel bearings, axle and vehicle springs to said frame.

Claim 3

Low tire pressure indicating and warning means in accordance with claim 2 adapted to provide warning of tire pressure below said predetermined level in any tire on any nonrotating axle on said vehicle; said annunciator means is a bank of signal lights, each light being connected in circuit with the appropriate electrical fittings on a separate wheel and the valve stem of the tire on that wheel so that it can give warning of low pressure in that tire; and said bank of signal lights is positioned where it can be readily seen by the driver in charge of said vehicle; whereby the driver can tell by a warning signal from any given signal light which vehicle axle, and which end of said axle, has a low pressure tire.

Claim 4

Low tire pressure indicating and warning means in accordance with claim 1 in which said resilient pickup contact is formed from a strip of thin, springy metal; and the pickup contact has a base segment by means of which it is securable to the side wall of said dust cap, in the space within the dust cap, and a leaf segment separated from the base segment by a sharp bend, said leaf segment being sized and shaped to extend into said space and bear resiliently against said electrical contact point attached to said axle, when said base segment is secured in proper position to said side wall of said dust cap.

Claim 5

Low tire pressure indicating and warning means in accordance with claim 1 in which said electrical contact members of said switch are formed of thin strips of suitably conductive metal, mounted in parallel and diametrically opposite relationship within the switch; said elongate segment of the second contact member is designed to extend substantially across the interior space within said hollow casing; and said first electrical contact is positioned to receive the outer end of said elongate segment in bearing contact, to close said switch, when the latter is disposed in its normal position within said casing.

Claim 6

Low tire pressure indicating and warning means in accordance with claim 2 adaptable for use on vehicles with dual wheels in which each of the tire valve stems on each pair of dual wheels is fitted with the tire pressure indicating means and switch components of said low tire pressure indicating and warning means, and the switch on each wheel has an electrical conductor joining one of its electrical contacts with a dust cap common to said pair of dual wheels, whereby a pressure drop below said predetermined level in the tire on either of the wheels causes actuation of said annunciator unit.

Claim 7

Low tire pressure indicating and warning means in accordance with claim 3 in which said vehicle is a trailer and said driver is the driver of a tow vehicle for said trailer; said source of electric energy is the tow vehicle battery; and including a disconnect plug; whereby said signal lights can be installed in said tow vehicle and connected respectively in circuit with the electrical contact points on the ends of each nonrotating axle on said trailer through said disconnect Plug.

Claim 8

Low tire pressure indicating and warning means in accordance with claim 7 in which said disconnect plug has terminals for connecting wire leads from the frames of the tow vehicle and trailer to assure good electrical contact therebetween.

Claim 9

Low tire pressure indicating and warning means in accordance with claim 7 in which said electrical conductor means includes a bridging wire for connecting each nonrotating axle on said trailer with said trailer frame to assure unhindered current flow between said switch and said trailer frame when the switch is closed.

Claim 10

In combination, vehicle means having at least one nonrotating axle and adapted to roll on wheels with pneumatic tires, and low tire pressure indicating and warning means comprising: at least one annunciator unit capable of giving a warning signal when energized by an electric current; at least one electrical contact point designed for insulated attachment to one end of a nonrotating vehicle axle fitted with a wheel on which is mounted a pneumatic tire; resilient pickup contact means designed for attachment to the dust cap of the hub of said wheel so as to rotate with the wheel while maintaining electrical contact with said electrical contact point attached to said axle; at least one tire pressure indicating means adapted for threaded engagement with the valve stem of said tire and having a housing, a piston head plunger with an integral shaft and biasing means for said plunger; and at least one switch having a hollow casing adapted to fit snugly onto said low tire pressure indicating means; the housing for said low tire pressure indicating means being hollowed to receive said piston head plunger and permit movement of the latter between a retracted position, in which it is disposed substantially entirely within said housing, and an extending position, in which a portion of its shaft extends out of said housing, and said biasing means being resiliently adaptable to hold said plunger in said retracted position at all counterpressures on its piston head below a predetermined level; said low tire pressure indicating means being adapted, when in threaded engagement with said valve stem, to depress the tire valve plunger and thereby permit pressurized air from said tire to act in opposition to said biasing means on said piston head plunger, whereby the air pressure urges the piston head plunger away from said retracted position toward said extending position when said pressure exceeds said predetermined level, but the biasing means urges the piston head plunger back to said retracted position if the air pressure falls below said predetermined level; the manner in which the casing of said switch fits onto said low tire pressure indicating means being such that its hollow interior receives the shaft of said piston head plunger when it extends from said housing in its extending position; said switch having a pair of built-in electrical contact members, a first one of which has a terminal end of fixed position within said casing to form a first electrical contact and the second of which has an elongate segment resiliently movable about a bend spaced from said first electrical contact within said casing, said resilient elongate segment being self-biased into bearing contact, at its outer end, with said first electrical contact; said switch being designed to cooperate, in use, with said low tire pressure indicating means in such fashion that outward extension of the shaft of the piston head plunger of the latter, under the influence of tire air pressure, brings said shaft into switch-opening contact with the resiliently movable elongate element of the second electrical contact member, and movement of the piston head plunger to its retracted position within said housing, as a result of a drop in tire air pressure below said predetermined level, carries the plunger shaft out of contact with said elongate segment so that the latter biases itself into bearing contact With said first electrical contact to effect automatic closure of the switch; and the above-claimed components of said low tire pressure indicating and warning means cooperating with one another to provide said low tire pressure indicating and warning means for at least one tire on said vehicle means when installed in combination with a source of electric energy and electrical conductor means in a vehicular environment comprising said vehicle means, and said electrical conductor means is adapted to connect said components in circuit and permit the flow of electric current from the source of electric energy through said annunciator unit to said electrical contact point on the end of a nonrotating axle on said vehicle, then through said resilient pickup contact means attached to the dust cap on the wheel hub of said vehicle to one of said electrical contacts of said switch, then through the other electrical contact of said switch, when the switch is closed, to the metal frame of the vehicle means and from this frame back to said source of electric energy; whereby the circuit remains open so long as the air pressure in said tire is above said predetermined level to urge the piston head plunger of said low tire pressure indicating means into switch-opening contact with the resiliently movable segment of said second electrical contact in said switch, but closes when said air pressure drops below said predetermined level so that current flows through the circuit to actuate said annunciator unit to actuate it and give warning of the air pressure drop within the tire.