Fail-safe circuit for multiple channel vacuum modulated adaptive braking system

Abstract

Abstract A FAIL-SAFE CIRCUIT WHICH IS SUITABLY USED IN AN ADAPTIVE BRAKING SYSTEM. NORMALLY, IN KNOWN ADAPTIVE BRAKING SYSTEMS A CONTROL SIGNAL IS APPLIED TO A BRAKE PRESSURE MODULATOR WHICH IS THEREBY CAUSED TO OPTIMIZE THE BRAKING CHARACTERISTICS OF A WHEELED VEHICLE DURING THE TIME THE VEHICLE IS BEING BRAKED. IN THE PRESENT INVENTION A NORMALLY CLOSED MODULATOR LIMIT SWITCH IS PROVIDED WHICH OPENS WHENEVER THE MODULATOR ATTEMPTS TO CONTROL THE VEHICLE BRAKING CHARACTERISTICS. A NORMALLY OPEN BRAKE SWITCH IS CONNECTED ACROSS THE MODULATOR SWITCH THUS SHUNTING THIS LATTER SWITCH WHENEVER THE BRAKE PEDAL IS DEPRESSED. A LATCHING CIRCUIT WHICH IS LATCHED WHEN THE VEHICLE STARTER IS ENERGIZED AND WHICH SUPPLIES POWER TO THE MODULATORS WHENEVER LATCHED, IS SERIALLY CONNECTED TO THE SHUNTED COMBINATION OF BRAKE SWITCH AND MODULATOR LIMIT SWITCH. ADDITIONALLY THE CONTROL SIGNAL IS SAMPLED AT THE LOW VOLTAGE END OF THE LATCHING CIRCUIT BY AN RC CIRCUIT. IF THE DURATION OF THE ERROR SIGNAL IS EXCESSIVE THE VOLTAGE AT THE LOW VOLTAGE END OF THE LATCHING CIRCUIT, THAT IS, THE VOLTAGE ACROSS THE RC CIRCUIT, WILL BUILD TO A LEVEL TO UNLATCH THE LATCHING CIRCUIT. WHEN THE LATCHING CIRCUIT IS UNLATCHED, WHETHER BY THE OPENING OF THE LIMIT SWITCH WHILE THE BRAKE SWITCH IS OPEN OR BY VOLTAGE ACROSS THE RC CIRCUIT, POWER IS REMOVED FROM THE MODULATOR WHICH WILL THUS RETURN TO A NORMAL POSITION AND RESTORE NORMAL VEHICLE BRAKING.

Inventors

• 👤 Donald W Howard

Bibliographic Details