Tandem suspension for steerable axles

A method of installing a tandem suspension in a vehicle having a first steerable axle and a first leaf spring linking the chassis and the first axle, the first leaf spring having first and second extremities, the first extremity engaging the chassis, the method comprising steps of:

• providing a second steerable axle for positioning behind the first axle in a tandem configuration therewith;
• linking the chassis and the second axle with a second leaf spring, the second leaf spring having first and second extremities, the first extremity for engaging the chassis, the second axle being mounted between the first and second extremities;
• installing an equalizer assembly for equalizing the front and rear axles, the equalizer assembly operable to be mounted to the chassis and to link the respective second extremities of the front and rear leaf springs;
• installing a front air spring between the chassis and the first axle;
• installing a rear air spring between the chassis and the second axle;
• installing a pneumatic control system operable to be 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
• installing 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.

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 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 pneumatically balance the front and rear air springs, the pneumatic control system being further 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.