Method and apparatus for sensing air pressure in pneumatic suspension units for vehicles

Claim 3

A device as claimed in claim 1 wherein said air pressure sensor means comprises normally-closed switches which are closed when the pressures in said pneumatic suspension units are in a normal pressure range and which are opened when the pressures in said pneumatic units are below the normal pressure range, said vehicle speed sensor means comprising a vehicle speed sensing circuit which generates an output signal of relatively low level when the vehicle speed is below a predetermined level, and generates an output signal of relatively high level when the vehicle speed exceeds said predetermined level, said signal processor means comprising a first circuit for regulating output signals from said air pressures sensors to a relatively low level when said normally-closed switch is closed, and to a relatively high level when said normally-closed switch is opened, a second circuit which receives an output signal from said first circuit and an output signal from said vehicle speed sensor means and which generates a signal of a relatively high level, only when both of the output signals from said first circuit and said vehicle speed sensor means are at said relatively high levels, and a third circuit which receives an output signal from said second circuit and which generates an output signal for actuating said indicating means when said second circuit produces an output signal of a relatively high level continuously for more than a predetermined period of time.

Claim 4

A device as claimed in claim 1 wherein said signal processor means includes a fault checking circuit which permits checking normal operation of said indicating means by automatically supplying electric current to said indicating means for a predetermined period of time when said signal processor means is actuated.

Claim 5

A device as claimed in claim 1 wherein said signal processor means includes timer means for establishing said period of time beyond which the output from the signal processor means must be continued in order for the indicating means to be energized.

Claim 6

A device as claimed in claim 1 wherein said air pressure sensor means comprises two air pressure sensors connected to respective pneumatic suspension units, said signal processor means comprising a first circuit means connected to said air pressure sensors to produce a signal when at least one of said air pressure sensor means is at a level below said predetermined level, and a second circuit means connected to said first circuit means and to said vehicle speed sensor means and including time delay means for producing a signal when the first circuit means and said vehicle speed sensor means both produce output signals for more than said predetermined period of time.

Claim 9

A device as claimed in claim 6 wherein said air pressure sensor means comprises normally-closed switches which are closed when the pressures in said pneumatic suspension units are in a normal pressure range and which are opened when the pressures in said pneumatic units are below the normal pressure range, said vehicle speed sensor means comprising a vehicle speed sensing circuit which generates an output signal of relatively low level when the vehicle speed is below a predetermined level, and generates an output signal of relatively high level when the vehicle speed exceeds said predetermined level, said signal processor means comprising a first circuit for regulating output signals from said air pressure sensors to a relatively low level when said normally-closed switch is closed, and to a relatively high level when said normally-closed switch is opened, a second circuit which receives an output signal from said first circuit and an output signal from said vehicle speed sensor means and which generates a signal of a relatively high level, only when both of the output signals from said first circuit and said vehicle speed sensor means are at said relatively high levels, and a third circuit which receives an output signal from said second circuit and which generates an output signal for actuating said indicating means when said second circuit produces an output signal of a relatively high level continuously for more than a predetermined period of time.

Claim 10

A device as claimed in claim 6 wherein said signal processor means includes a fault checking circuit which permits checking normal operation of said indicating means by automatically supplying electric current to said indicating means for a predetermined period of time when said signal processor means is actuated.

Claim 11

A device as claimed in claim 6 wherein said signal processor means includes timer means for establishing said period of time beyond which the output from the signal processor means must be continued in order for the indicating means to be energized.

Claim 12

A device as claimed in claim 6 wherein said air pressure sensor means comprises two air pressure sensors connected to respective pneumatic suspension units, said signal processor means comprising a first circuit means connected to said air pressure sensors to produce a signal when at least one of said air pressure sensor means is at a level below said predetermined level, and a second circuit means connected to said first circuit means and to said vehicle speed sensor means and including time delay means for producing a signal when the first circuit means and said vehicle speed sensor means both product output signals for more than said predetermined period of time.