Ride control circuit for a work machine

A hydraulic ride control circuit for a machine having a loader arm, the circuit including:

• a hydraulic ram having first and second chambers, the ram being adapted to raise and lower the loader arm;
• a first control valve connected to the first and second chambers and adapted to feed pressurized fluid to one of the first and second chambers so as to selectively raise or lower the loader arm;
• a load hold valve located between the first control valve and first chamber, the load hold valve having a hydraulic control surface and being movable between a first position in which fluid flow from the first chamber to the first control valve is prevented, and a second position in which fluid flow from the first chamber to the first control valve is permitted;
• a pressure-monitoring line connecting the second chamber and the control surface of the load hold valve such that fluid pressure in the second chamber can act upon the control surface and move the load hold valve into the second position;
• a first hydraulic accumulator connected to the first chamber and located between the first control valve and the load hold valve;
• a second control valve connected between the first accumulator and the first chamber and movable between a first position in which fluid flow from the accumulator to the first chamber is prevented and a second position in which fluid flow from the accumulator to the first chamber is permitted;
• a third control valve connected between the second chamber and the control surface of the load hold valve and movable between a first position in which fluid flow between the second chamber and the control surface in both directions is permitted, and a second position in which fluid flow between the second chamber and the control surface is prevented;
• and
• pressure-monitoring means located between the first accumulator and the load hold valve.

A machine having a loader arm and a hydraulic ride control circuit for the loader arm, the circuit including:

• a hydraulic ram having first and second chambers, the ram being adapted to raise and lower the loader arm;
• a first control valve connected to the first and second chambers and adapted to feed pressurized fluid to one of the first and second chambers so as to selectively raise or lower the loader arm;
• a load hold valve located between the first control valve and first chamber, the load hold valve having a hydraulic control surface and being movable between a first position in which fluid flow from the first chamber to the first control valve is prevented, and a second position in which fluid flow from the first chamber to the first control valve is permitted;
• a pressure-monitoring line connecting the second chamber and the control surface of the load hold valve such that fluid pressure in the second chamber can act upon the control surface and move the load hold valve into the second position;
• a first hydraulic accumulator connected to the first chamber and located between the first control valve and the load hold valve;
• a second control valve connected between the first accumulator and the first chamber and movable between a first position in which fluid flow from the accumulator to the first chamber is prevented and a second position in which fluid flow from the accumulator to the first chamber is permitted;
• a third control valve connected between the second chamber and the control surface of the load hold valve and movable between a first position in which fluid flow between the second chamber and the control surface in both directions is permitted, and a second position in which fluid flow between the second chamber and the control surface is prevented;
• and
• a second hydraulic accumulator connected to both the second chamber and the third control valve, the second accumulator adapted to receive fluid flow from the second chamber, and wherein the third control valve prevents fluid flow from the second accumulator to the control surface when in its first position and permits fluid flow from the second accumulator to the control surface in its second position.