Roll-resistant hydraulic suspension system, kit and method for load handling vehicles

A method of adjusting a height of a vehicle, the vehicle having a body, at least one axle and a suspension system that suspends the body over the at least one axle, the suspension system having:

• a first hydraulic circuit including a first hydraulic cylinder coupled to the axle and to a first side of the body, and a first counterbalance valve connected to the first hydraulic cylinder,
• a second hydraulic circuit including a second hydraulic cylinder coupled to the axle and a second side of the body, and a second counterbalance valve connected to the second hydraulic cylinder, and
• a three-position leveling valve positioned on a line connecting the first and second hydraulic circuits, the leveling having a first neutral position, a second lowering position and a third raising position,
• the method comprising:
• moving the leveling valve from the neutral position to either the lowering position or the raising position, thereby connecting the first and second counterbalance valves together;
• adjusting the pressure of working fluid within the suspension system to respectively lower or raise the body of the vehicle with the first hydraulic cylinder and the second hydraulic cylinder acting together;
• and
• returning the leveling valve to the neutral position to thereby disconnect the first counterbalance valve and the second counterbalance valve from each other when a desired vehicle height is reached.

A suspension system for a vehicle, comprising:

• a first hydraulic circuit operatively coupleable to a first side of the vehicle, the first hydraulic circuit being selectively controllable to move the first side of the vehicle, the first hydraulic circuit comprising a first hydraulic cylinder having a body end that attaches to the first side of the vehicle and an axle end that attaches to a common axle of the vehicle, a first accumulator connected to the first hydraulic cylinder and a first check valve connected to the first accumulator;
• a second hydraulic circuit operatively coupleable to a second side of the vehicle, the second hydraulic circuit being selectively controllable to move the second side of the vehicle, the second hydraulic circuit comprising a second hydraulic cylinder having a body end attached to the second side of the body and an axle end attached to the common axle, a second accumulator attached to the second hydraulic cylinder, a second check valve attached to the second accumulator;
• and
• a connection between the first hydraulic circuit and the second hydraulic circuit,
• wherein the first hydraulic circuit and the second hydraulic circuit operate together in a first mode when the connection between the first hydraulic circuit and the second hydraulic circuit is open to move the first and second sides of the vehicle in a same direction,
• wherein the first hydraulic circuit and the second hydraulic circuit operate independently of each other in a second mode when the connection is closed, and
• wherein the first check valve and the second check valve are arranged in a back-to-back relationship with a common drain line extending downstream, thereby allowing the first accumulator and the second accumulator to be drained by alternatingly depressurizing the first accumulator and the second accumulator.