US 4,658,970 A · Deflection reduction module for boom hoist cylinder of mobile crane

Abstract

A mobile crane comprises a vehicle chassis mounted on balloon tires, a crane boom pivotally mounted on the chassis, and a double-acting boom hoist cylinder connected between the chassis and the boom for raising and lowering the boom. As the mobile crane traverses rough terrain or accelerates or decelerates, its mass causes the chassis to deflect (bounce or porpoise) relative to the terrain. A deflection reduction system, which presupposes that the boom is unrestrained and free to pivot (deflect) relative to the chassis, comprises a deflection reduction module mechanically mounted on the outside of the boom hoist cylinder and selectively operable valves for hydraulically connecting the module thereto. The module comprises a gas barrel containing compressed gas, a gas piston slidably mounted therein, a hydraulic fluid barrel axially aligned with the gas barrel, a hydraulic fluid piston (of smaller area than the gas piston) slidably mounted therein and connected to the gas piston, and a helical compression spring in the gas barrel for biasing the pistons in the same direction as the compressed gas. Operation of a first solenoid valve mounted on the outside of the boom hoist cylinder isolates the double-acting boom hoist cylinder and interconnects its opposite ends in a closed circuit. Simultaneous operation of a second solenoid valve mounted on the outside of the module connects the closed circuit to a fluid inlet/outlet port in the hydraulic fluid barrel. As a result, boom deflection causes hydraulic fluid flow into and out of the hydraulic fluid barrel. The resulting reaction of the spring and the compressed gas reduces deflection of the chassis.

Claims22

Dependent claims

A deflection reduction module for mechanical and hydraulic connection to a boom hoist cylinder which is connected between the chassis of a vehicle and a boom pivotably mounted on said chassis, comprising:

a gas barrel for containing gas;
a gas piston slidably mounted in said gas barrel and adapted to be biased in one direction by said gas acting thereon;
a hydraulic fluid barrel;
a hydraulic fluid piston slidably mounted in said hydraulic fluid barrel;
said hydraulic fluid barrel having a hydraulic fluid port therein for ingress and egress of hydraulic fluid from said boom hoist cylinder;
means for connecting said gas piston and said hydraulic fluid piston so that the pistons move in unison;
and a spring for biasing said pistons in said one direction;
said module being operable so that ingress and egress of hydraulic fluid through said port into and out of said hydraulic fluid barrel from said boom hoist cylinder effects compression and expansion, respectively, of said spring and said gas.

5 more elements

In a mobile machine:

a vehicle chassis deflectable relative to terrain over which it travels;
a load-handling boom pivotably mounted on said chassis and deflectable relative to said chassis;
a double-acting boom hoist cylinder for raising and lowering said boom and connected between said chassis and said boom, said boom hoist cylinder comprising a boom hoist cylinder housing, a boom hoist piston slidably mounted in said housing and dividing said housing into two chambers on opposite sides of said boom hoist piston, and a boom hoist piston rod connected to said boom hoist piston;
means for operating said boom hoist cylinder comprising a source of hydraulic fluid, a selectively operable boom hoist control valve connected to said source and operable to extend and retract said boom hoist cylinder, a holding valve operable to maintain said boom hoist cylinder in a raised position;
and a deflection reduction system for preventing deflection of said chassis and responsive to deflection of said boom and comprising:
a deflection reduction module for mounting on said boom hoist cylinder and comprising a hydraulic fluid cylinder having a hydraulic fluid piston therein, a gas cylinder having a gas piston and compressed gas therein for biasing said gas piston in one direction, said pistons being interconnected so that they are movable in unison, and a spring for biasing said pistons in said one direction;
and valve means selectively operable to by-pass said boom hoist control valve and said holding valve and to interconnect said two chambers of said boom hoist cylinder in a closed circuit and to connect said closed circuit to said hydraulic fluid cylinder.

4 more elements

Dependencies are inferred from the claim text.

Deflection reduction module for boom hoist cylinder of mobile crane

Life of this patent

Deflection reduction module for boom hoist cylinder of mobile crane

Life of this patent

Abstract

Claims22