Lift suspension system with offset control arms

1. An axle lift system for a suspension for a vehicle, the vehicle having a chassis, an axle having a first end and a second end, an upper control arm and a lower control arm pivotally attached at a first end of each control arm to the axle at a point on the axle and pivotally attached a second end of each control arm to the chassis, with the upper control arm substantially above the lower control arm, the axle lift system comprising:

an upper air bag bracket attached to the upper control arm,

a lower air bag bracket attached to the lower control arm,

a lift air bag attached between the upper air bag bracket and the lower air bag bracket,

wherein the longitudinal axis of the lift air bag is disposed at an angle to the longitudinal axis of the control arms.

2. The axle lift system of claim 1 wherein the control arms are disposed at a first angle to the axle such that the first end of each control arm is offset from the second end thereof with respect to the centerline of the chassis.

3. The axle lift system of claim 2 wherein the upper control arm comprises a first portion and a second portion disposed at an angle to each other along the longitudinal axis of the control arm; and

the lower control arm comprises a first portion and a second portion disposed at an angle to each other.

4. The axle lift system of claim 3 wherein the upper air bag bracket is attached to the second portion of the upper control arm; and the lower air bag bracket is attached to the first portion of the lower control arm.

5. The axle lift system of claim 4 wherein the upper air bag bracket comprises an air bag seat and at least one rib attaching the air bag seat to the upper control arm, and wherein the lower air bag bracket comprises an air bag seat and at least one rib attaching the air bag seat to the lower control arm.

6. The axle lift system of claim 4 wherein the control arms are disposed such that the first end of each control arm is offset from the second end thereof in an outboard direction with respect to the centerline of the chassis.

7. The axle lift system of claim 4 wherein the control arms are disposed such that the first end of each control arm is offset from the second end thereof in an inboard direction with respect to the centerline of the chassis.

8. The axle lift system of claim 6 wherein the longitudinal axis of the lift air bag is disposed outboard of the control arms.

9. The axle lift system of claim 6 wherein the longitudinal axis of the lift air bag is disposed inboard of the control arms.

10. A suspension system for a vehicle having a chassis, the suspension system comprising:

an axle;

an upper control arm and a lower control arm pivotally attached at a first end of each control arm to the axle at a first point on the axle, with the upper control arm substantially above the lower control arm;

an upper air bag bracket attached to the upper control arm;

a lower air bag bracket attached to the lower control arm;

a lift air bag attached between the upper air bag bracket and the lower air bag bracket,

wherein the second ends of the control arms are pivotally attached to at least one hanger bracket attached to the chassis;

wherein each of the control arms is disposed at a first angle to the axle such that the first end of each control arm is offset from the second end thereof with respect to the centerline of the chassis;

wherein the lift air bag is disposed at a second angle to the control arms; and

wherein the center axis of the lift air bag is substantially offset from the axis of the control arms.

11. The suspension system of claim 10 , wherein the center axis of the lift air bag is disposed outboard of the longitudinal axis of the control arm to which it is attached.

12. The suspension system of claim 10 , wherein the center axis of the lift air bag is disposed inboard of the longitudinal axis of the control arm to which it is attached.

13. A method for using the axle lift system of claim 1 , comprising the steps of:

inflating the lift air bag until the upper and lower control arms pivot upwardly sufficiently to raise the axle a desired distance to a lifted position;

operating the vehicle with the axle in the lifted position;

deflating the lift air bag until the upper and lower control arms pivot downwardly sufficiently to lower the axle a desired distance to a lowered position;

operating the vehicle with the axle in the lowered position.

14. The method of claim 13 wherein the lifted position comprises a position wherein a tire mounted on the axle is not in contact with the ground, and the lower position comprises a position wherein a tire mounted on the axle is in contact with the ground.

15. The method of claim 14 wherein the vehicle is provided with a suspension air bag for supporting the axle beneath the chassis, the method further comprising the steps of:

deflating the suspension air bag before or simultaneously with the step of inflating the lift air bag; and

inflating the suspension air bag after or simultaneously with the step of deflating the lift air bag.