Vehicle tire pressure warning system

Claim 2

For use with a vehicle having a wheel mounted inflatable tire pressure sensing means adapted to be mounted on a wheel for rotation therewith; said pressure sensing means comprising sealed chamber means for communication with the tire chamber, said sealed chamber means defining one fixed wall and a confronting movable wall each of non-magnetic material, means normally urging said movable wall toward said fixed wall, magnet means mounted on said movable wall for rectilinear movement relative to said fixed wall, said magnet means being urged away from said fixed wall by the pressure within said chamber, and a magnetic shunt member of ferromagnetic material mounted adjacent to said fixed wall for concentrating the magnetic flux of said magnetic means; a magnetic operated switch adapted to be mounted on the vehicle in proximity to the plane of rotation of said sensing means fixed wall; said switch means being operated in reSponse to the magnetic field produced by said pressure sensing means when said magnetic means lies adjacent to said fixed wall; and circuit means for connection to a source of electrical energy including said magnetically operated switch and an electrically operated warning device.

Claim 3

Apparatus as set fourth in claim 1 wherein said sealed chamber means is defined by a cup-shaped case and a bellows mounted in sealed relation at the open end of said case and extending into the case chamber, said bellows defining said movable wall; and spring means mounted within said bellows urging said bellows and the magnet means mounted thereon into said case toward the fixed wall defined by a base wall of said cup-shaped case.

Claim 4

Apparatus as set forth in claim 2 wherein said magnetic shunt member comprises a bar of magnetizable metal mounted on the exterior surface of said fixed wall.

Claim 5

Apparatus as set forth in claim 1 wherein said magnet means defines magnetic poles spaced transversely relative to the direction of rectilinear movement of said magnet; and wherein said magnetic shunt means is defined by a bar of ferromagnetic material oriented relative said poles to concentrate the magnetic flux produced by said magnet means adjacent to the plane of said fixed wall.

Claim 6

Apparatus as set forth in claim 1 wherein said circuit means includes an electronic switching device connecting said warning device in series with said source of electrical energy, and a branch circuit connecting said magnetically operated switch in series with said electronic switching device and said source of electrical energy to effect the switching of said electronic switching device.

Claim 7

Apparatus as set forth in claim 5 wherein said electronic switching device comprises a transistor; and wherein said branch circuit includes a capacitor connected in series with said magnetically operated switch and the base electrode of said transistor to control the switching voltage of the transistor.

Claim 8

In combination with a vehicle having a plurality of rotatable wheels each carrying an inflatable tire; a pressure sensing device mounted on each wheel for rotation therewith; conduit means communicating each pressure sensing device with a respective tire chamber; each pressure sensing means comprising a sealed housing providing one fixed wall and the confronting movable wall each of non-magnetic material, spring means urging said movable wall toward a fixed wall, a permanent magnet mounted on said movable wall for rectilinear movement toward and away from said fixed wall, and a magnetic shunt member of ferromagnetic material mounted on said fixed wall; a plurality of magnetically operated switches mounted on said vehicle, one switch being mounted adjacent each of said wheels in proximity to the plane of rotation of the respective sensing device fixed wall; each of said switches being operated in response to the magnetic fields produced by a sensing device when a respective magnet means is positioned adjacent to the fixed wall; and circuit means including an electrically operated warning device and an electronic switching device for connection to the vehicle source of electrical energy; and each of said magnetically operated switches being connected to said electric switching device for actuating said switching device.

Claim 9

In combination with a vehicle having a plurality of rotatable wheels each carrying an inflatable tire; a pressure sensing device mounted on each wheel for rotation therewith; conduit means communicating each pressure sensing device with a respective tire chamber; each pressure sensing means comprising a sealed housing providing one fixed wall and the confronting movable wall each of non-magnetic material, spring means urging said movable wall toward a fixed wall, a permanent magnet mounted on said movable wall for rectilinear movement toward and away from said fixed wall, and a magnetic shunt member of ferromagnetic material mounted on said fixed wall; a plurality of magnetically operated switches mounted on said vehicle, one switch being mounted adjacent each of said wheels in proximity to the plane of rotation of the respective sensing device fixed wall; each of said switches being operated in response to the magnetic fields produced by a sensing device when a respective magnet means is positioned adjacent to the fixed wall; and circuit means including an electrically operated warning device and an electronic switching device for connection to the vehicle source of electrical energy; and each of said magnetically operated switches being connected to said electric switching device for actuating said switching device.

Claim 10

Apparatus as set forth in claim 7 wherein each pressure sensing means comprises a cup-shaped housing defining the one fixed wall and a bellows closing the open end of the housing and defining the movable wall carrying said magnet; said cup-shaped housing and bellows being fabricated of a non-magnetic material; and said circuit means including said electrically operated warning device and said electronic switching device in series with the vehicle source of electrical energy, said electronic switching device comprising a transistor; said plurality of magnetically operated switches being connected in parallel with each other; and said pArallel connected magnetically operated switches being connected in series with the transistor base electrode and said vehicle source of electrical energy for controlling the switching voltage of said transistor.

Claim 11

A pressure sensing device, adapted for connection to an inflatable chamber, for use with a magnetically operated switch comprising means defining a sealed chamber providing a fixed wall and a confronting movable wall each of non-magnetic material; spring means normally urging said movable wall toward said fixed wall; a permanent magnet mounted on said movable wall for rectilinear movement toward and away from said fixed wall, said magnet being urged away from said fixed wall by the pressure within said chamber means; and a shunt member of ferromagnetic material mounted on said fixed wall for concentrating the magnetic flux produced by said magnet.

Claim 12

A pressure sensing device, adapted for connection to an inflatable chamber, for use with a magnetically operated switch comprising means defining a sealed chamber providing a fixed wall and a confronting movable wall each of non-magnetic material; spring means normally urging said movable wall toward said fixed wall; a permanent magnet mounted on said movable wall for rectilinear movement toward and away from said fixed wall, said magnet being urged away from said fixed wall by the pressure within said chamber means; and a shunt member of ferromagnetic material mounted on said fixed wall for concentrating the magnetic flux produced by said magnet.

Claim 13

Apparatus as set forth in claim 9 wherein said sealed chamber is defined by a cup-shaped housing, providing said fixed wall and a bellows mounted in the open end of said cup-shaped housing, providing said movable wall; said housing and bellows being fabricated of non-magnetic materials; said magnet providing poles spaced transversely relative to the direction of rectilinear movement of said magnet; and said magnetic shunt member being disposed in a plane normal to said direction of rectilinear movement.