Method of operating a hydraulic system for a loader machine

Abstract

A method of operating a hydraulic system of a loader arm carrying a working implement, the system having a ride improvement system and a selection valve connected to first and second chambers of a ram which operates the loader arm. A check valve assembly is provided, with the check valve assembly being responsive to pressure changes in the second chamber. The check valve assembly, when closed, prevents fluid from passing between the first chamber to the selection valve. Means are provided communicating the fluid pressure in the second chamber to the check valve, with the means responsive to pressure changes in the second chamber to open the check valve. The selection valve is operable to raise the loader arm with the system arranged to permit passage of fluid between the first chamber and the accumulator while permitting fluid to pass from the second chamber to a low pressure region.

1 - 6 . (canceled)  
   
   
       7 . A hydraulic system for a wheeled loader having a loader arm assembly which is movable between raised and lowered positions by means of a hydraulic actuator device, the system comprising: 
 a selection valve having first and second ports for directing hydraulic fluid to a cylinder, the cylinder having first and second chambers, the first chamber connected to the first port and the second chamber connected to the second port;    a hydraulic accumulator connected to the hydraulic actuator device between the first port and the first chamber;    a first control valve connected to the hydraulic actuator device between the hydraulic accumulator and the first chamber;    a second control valve connected to the hydraulic actuator device between the second port and the second chamber, the second control valve further connected to a hydraulic reservoir; and    a hose burst check valve connected to the hydraulic actuator device between the first port and the hydraulic accumulator;    wherein the first control valve is movable between a first position in which passage of hydraulic fluid is permitted only from the hydraulic accumulator toward the first chamber and a second position in which passage of hydraulic fluid is permitted in bi-directionally between the hydraulic accumulator and the first chamber,    the second control valve is movable between a first position in which passage of hydraulic fluid through the second control valve is prevented and a second position in which passage of hydraulic fluid through the second control valve is permitted, and    the hose burst check valve normally allows one-way hydraulic fluid flow from the first port to the first chamber, but the hose burst check valve is arranged to permit two-way hydraulic fluid flow between the first chamber and the first port when hydraulic fluid is directed from the second port to the hose burst check valve.    
   
   
       8 . The system according to  claim 7  wherein the hose burst check valve is a pilot valve.  
   
   
       9 . The system according to  claim 7  wherein the selection valve is manually operable.  
   
   
       10 . The system according to  claim 7  wherein the first and second control valves are electrically operated solenoid valves to which current is supplied by a manually operable switch means.  
   
   
       11 . The system according to  claim 7  wherein the first and second control valves are biased towards the first position.  
   
   
       12 . The system according to  claim 11  wherein the first and second control valves are spring biased towards the first position.  
   
   
       13 . The system according to  claim 7  wherein at least one of said accumulator, control valves, check valve assembly and connecting pipes are made of metal.