US 4,586,332 AGranted

Hydraulic swing motor control circuit

AssigneeCaterpillar Tractor Co.

InventorLawrence F. Schexnayder

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Abstract

Hydraulic motors are conventionally employed in rotating the upper structure of excavators and the like. Protection from inertia induced hydraulic shock loads of some hydraulic control circuits involves the use of a separate bypass valve which continuously interconnects the motor conduits. The subject control circuit includes a pair of shunt valves each of which establishes restricted communication between the first and second motor conduits in a particular direction at their normal spring biased position. This allows limited free swing of the upper structure when the directional control valve is shifted from an operating position to the neutral position. However, shifting the directional control valve to an operating position causes the appropriate one of the shunt valves to shift to a blocking position so that no interconnection between the motor conduits exist. Thus, the disclosed control circuit causes all pressurized fluid directed into one of the motor conduits to be transmitted to the hydraulic motor for maximum efficiency.

Claims6

Dependent claims

In a control circuit having a hydraulic motor, a pump, a directional control valve connected to the pump, and first and second motor conduits connecting the control valve with opposite sides of the hydraulic motor, said directional control valve being movable between a first position at which pressurized fluid is directed through the first motor conduit to the motor and a second position at which pressurized fluid is directed through the second motor conduit to the motor, said directional control valve having an intermediate position at which the first and second motor conduits are blocked from each other and from the pump, the improvement comprising;

a first shunt valve connected between the first and second motor conduits and being movable between a first position at which restricted communication is established therethrough in a direction from the first motor conduit to the second motor conduit and a second position at which communication through the first shunt valve is blocked;
first means for moving the first shunt valve to the second position in response to the directional control spool being moved to the first position;
a second shunt valve connected between the first and second motor conduits and being movable between a first position at which restricted communication is established therethrough in a direction from the second motor conduit to the first motor conduit, and a second position at which communication through the second shunt valve is blocked;
and
second means for moving the second shunt valve to the second position in response to the directional control valve being moved to the second position.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/672,723Filed 19 Nov 1984
Granted: 6 May 1986
Term ends: Not estimatedThe source records don’t support an estimate.

Classification17 codes

E02F 9/28
Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00: small metalwork…
E02F 9/123
Turntables, i.e. structure rotatable about 360°: drives or control devices specially adapted therefor
E02F 9/128
Turntables, i.e. structure rotatable about 360°: braking systems
F15B 11/0445
By means in the return line: with counterbalance valves, e.g. to prevent overrunning or for braking