Patent ID: 7497524
Filing Date: 2009-03-03
Classification: B60T

Abstract:
1. A motor vehicle comprising: a park brake operable by an operating device for selectively locking and unlocking wheels on which the vehicle travels; a pressurized air source; an air circuit for causing the operating device a) to operate the park brake to unlock the wheels when pressurized air from the pressurized air source, that acts on the operating device through an air line leading to the operating device, acts on the operating device with a nominal pressure that is sufficient to assure unlocking of the wheels and b) to operate the park brake to lock the wheels when air pressure acting through the air line on the operating device is less than some minimum pressure for keeping the wheels locked; a lift platform and associated lift mechanism that are selectively positionable c) to a deployed position that allows the lift platform to be raised and lowered by the lift mechanism when the vehicle is parked and d) to a stowed position that does not allow the lift platform to be raised and lowered by the lift mechanism; a selectively operable interlock valve connected in the air circuit for allowing pressurized air from the pressurized air source to act through the air line on the operating device whenever the lift platform and associated lift mechanism are indicated by an indicating device to be in the stowed position and for disallowing pressurized air from the pressurized air source to act through the air line on the operating device whenever the lift platform and associated lift mechanism are indicated by the indicating device not to be in the stowed position; a pressure-sensitive device for sensing air pressure in the air line leading to the operating device; and an indicator operated by the pressure-sensitive device when air pressure in the air line leading to the operating device has decreased significantly enough from the nominal pressure, but is still greater than the minimum pressure, to indicate the possibility of imminent locking of the wheels.