Pneumatic tire low pressure monitoring and warning system

Claim 2

A pneumatic tire low pressure monitoring and warning system comprising, means sensing a low pressure condition in a pneumatic tire supported on an associatEd vehicle by a rotatable support, a transmitter fixed off center to said rotatable support and being rotatable therewith at a distance from the central axis of rotation, said transmitter being actuated by said sensing means to generate output signals at a radio frequency in response to said low pressure condition, a receiving antenna attached at a fixed position on said vehicle adjacent said tire within the near field of said transmitter, the coupling between said transmitter and said receiving antenna being subject to large variations resulting from differences in distance, orientation and shielding between said transmitter and said receiving antenna, said antenna receiving only usable radio frequency signals during a portion of each complete rotation of said transmitter therepast when said coupling is maximized, a receiver, means operatively connecting said receiving antenna to said receiver, said receiver generating a discontinuous control signal indicating means operatively connected to said receiver and being activated by said control signal, and means in said receiver for increasing the effective time periods of said control signals to exceed the useful time periods of said radio frequency signals, said increasing means assuring said indicating means is effectively activated in response to said low pressure condition.

Claim 3

A system as set forth in claim 1 in which said sensing means comprises a pneumatic pressure actuated electrical switch.

Claim 4

A system as set forth in claim 1 in which said sensing means comprises a pneumatic pressure actuated switch, said transmitter is in the form of an oscillator tuned to oscillate within a preselected band, and further comprising a battery as a power source for said oscillator.

Claim 5

A system as set forth in claim 3 in which said sensing means, oscillator, and battery are provided as an assembly, said assembly being detachable fixed to said rotatable support and thus carried thereby.

Claim 6

A system as set forth in claim 1 in which said transmitter comprises a self-pulsed transistor oscillator which provides said output signals as pulse modulated output signals, said pulse modulated signals having a pulse repetition rate within a pulse frequency band, and said receiver comprising an LF amplifier which selectively amplifies pulse signals within said pulse frequency band and attenuates signals outside said pulse frequency band, a rectifier integrating the rectifier pulse thereby generating said control signal.

Claim 7

In combination: a vehicle having a plurality of rotatable supports each supporting an associated pneumatic tire and being rotatable about an associated central axis of rotation and a system for detecting the presence of a low pressure condition in any one of the pneumatic tires, said system comprising, means sensing a low pressure condition in each pneumatic tire, a plurality of transmitters each carried off center by an associated rotatable support and being rotatable therewith at a distance from the central axis of rotation, each transmitter being actuated by its associated sensing means to provide pulse modulated output signals at a radio frequency in response to a low pressure condition in its associated tire, said pulse modulated signals having a pulse modulation rate within a preselected pulse frequency band, a plurality of receiving antennas each attached at a fixed position on said vehicle adjacent an associated tire within the near field of each of said transmitters, the couplings between said transmitters and said receiving antennas being subject to large variations resulting from differences in distance, orientation and shielding between said transmitters and said receiving antennas, said receiving antennas only receiving usable radio frequency signals during a portion of each complete rotation of an associated transmitter therepast when said coupling is maximized, a receiver, said receiver comprising an LF amplifier which selectively amplifies pulse signals within said pulse frequency band, a rectifier integraTing the rectifier pulse thereby generating a control voltage, means operatively connecting each receiving antenna to said receiver, an indicator operatively connected to said receiver and being activated by said control voltage, and means in said receiver for increasing the effective time periods of said usable control signals to exceed the useful time periods of said radio frequency signals, said increasing means assuring said indicator is effectively activated in response to a low pressure condition in any one of said tires.

Claim 8

In combination: a vehicle having a plurality of rotatable supports each supporting an associated pneumatic tire and being rotatable about an associated central axis of rotation and a system for detecting the presence of a low pressure condition in any one of the pneumatic tires, said system comprising, means sensing a low pressure condition in each pneumatic tire, a plurality of transmitters each carried off center by an associated rotatable support and being rotatable therewith at a distance from the central axis of rotation, each transmitter being actuated by its associated sensing means to provide pulse modulated output signals at a radio frequency in response to a low pressure condition in its associated tire, said pulse modulated signals having a pulse modulation rate within a preselected pulse frequency band, a plurality of receiving antennas each attached at a fixed position on said vehicle adjacent an associated tire within the near field of each of said transmitters, the couplings between said transmitters and said receiving antennas being subject to large variations resulting from differences in distance, orientation and shielding between said transmitters and said receiving antennas, said receiving antennas only receiving usable radio frequency signals during a portion of each complete rotation of an associated transmitter therepast when said coupling is maximized, a receiver, said receiver comprising an LF amplifier which selectively amplifies pulse signals within said pulse frequency band, a rectifier integraTing the rectifier pulse thereby generating a control voltage, means operatively connecting each receiving antenna to said receiver, an indicator operatively connected to said receiver and being activated by said control voltage, and means in said receiver for increasing the effective time periods of said usable control signals to exceed the useful time periods of said radio frequency signals, said increasing means assuring said indicator is effectively activated in response to a low pressure condition in any one of said tires.

Claim 9

A combination as set forth in claim 6 in which each transmitter is mounted off center from an axis of rotation of its associated rotatable support thereby providing said useable output signals only during an angular portion of each complete rotation of a support and its transmitter past an associated receiving antenna.

Claim 10

A combination as set forth in claim 7 in which each of said transmitters comprises a self-pulsed transistor oscillator.

Claim 11

A combination as set forth in claim 7 in which said indicator is in the form of a visual indicator.

Claim 12

A combination as set forth in claim 7 in which said means operatively connecting each receiving antenna to said receiver comprises a plurality of cable means each connecting an associated receiving antenna to said receiver.

Claim 13

A combination as set forth in claim 6 in which each of said supports comprises a mounting hub supporting an associated tire in the form of a tubeless tire and each of said transmitters is detachable fixed to an associated hub.

Claim 14

A combination as set forth in claim 10 in which said LF amplifier has a plurality of cooperating transistor-amplifiers the last of which also serves as a high-pass active filter.

Claim 15

A pneumatic tire low pressure monitoring and warning system comprising, means sensing a low pressure condition in a pneumatic tire supported on an associated vehicle by a rotatable support, a transmitter fixed to said rotatable support and being rotatable therewith, said transmitter being actuated by said sensing means and provides pulse modulated output signals at a predetermined radio frequency in response to said low pressure condition, said pulse-modulated signals having a pulse repetition rate within a pulse frequency band, a receiving antenna attached at a fixed position on said vehicle and receiving said output signals, a receiver having a detector which detects said signals from said transmitter, said receiver further comprising an LF amplifier which selectively amplifies pulse signals within said pulse frequency band and attenuates signal outside said pulse frequency band, a rectifier integrating the rectifier pulses thereby generating a control voltage, means operatively connecting said receiving antenna to said receiver, and indicating means operatively connected to said receiver and being activated by said control voltage.

Claim 16

A pneumatic tire low pressure monitoring and warning system comprising, means sensing a low pressure condition in a pneumatic tire supported on an associated vehicle by a rotatable support, a transmitter fixed to said rotatable support and being rotatable therewith, said transmitter being actuated by said sensing means and provides pulse modulated output signals at a predetermined radio frequency in response to said low pressure condition, said pulse-modulated signals having a pulse repetition rate within a pulse frequency band, a receiving antenna attached at a fixed position on said vehicle and receiving said output signals, a receiver having a detector which detects said signals from said transmitter, said receiver further comprising an LF amplifier which selectively amplifies pulse signals within said pulse frequency band and attenuates signal outside said pulse frequency band, a rectifier integrating the rectifier pulses thereby generating a control voltage, means operatively connecting said receiving antenna to said receiver, and indicating means operatively connected to said receiver and being activated by said control voltage.