Patent ID: 7850195

Claim:
A tandem suspension for connecting a chassis of a vehicle to front and rear axles, the front and rear axles being steerable, the tandem suspension comprising, on each side of the vehicle: a front leaf spring linking the chassis and the front axle, the front leaf spring having first and second extremities and the front axle being mounted therebetween, the first extremity of the front leaf spring engaging the chassis; a rear leaf spring linking the chassis and the rear axle, the rear leaf spring having first and second extremities and the rear axle being mounted therebetween, the first extremity of the rear leaf spring engaging the chassis; an equalizer assembly mounted to the chassis for equalizing the front and rear axles, the equalizer assembly linking the respective second extremities of the front and rear leaf springs; a front air spring disposed between the chassis and the front axle; a rear air spring disposed between the chassis and the rear axle; a pneumatic control system pneumatically linked to the front and rear air springs for supplying pressurized gas thereto and operable to selectively unload one of the front and rear air springs such that the one of the front and rear air springs does not take the load of the vehicle, the pneumatic control system comprising: a) a pneumatic distributing device for receiving the pressurized gas from a reservoir and distributing it to the front and rear air springs; and b) a three-way valve comprising: an output in fluid communication with the one of the front and rear air springs for supplying pressurized gas thereto; a first input in fluid communication with the distributing device for receiving pressurized gas therefrom; and a second input in fluid communication with the reservoir for receiving pressurized gas which has bypassed the distributing device; the three-way valve being operable in either a first mode of operation wherein the first input and the output are connected, or a second mode of operation wherein the second input and the output are connected; and a switch for sending a control signal to the pneumatic control system in response to an action by an operator, the pneumatic control system being responsive to the sending of the control signal by selecting the second mode of operation of the three-way valve and thereby selectively unloading the one of the front and rear air springs.