US 3,977,301 AGranted

Low-effort proportional control valve

AssigneeCaterpillar Tractor Co.

InventorsNeil W. Kroth, Kenneth R. Lohbauer, James E. Scheidt

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Abstract

A fluid control circuit for regulating fluid flow between a pressurized fluid source and a hydraulic motor, including a control valve having a movable spool for communicating fluid entering an inlet chamber from the source with service chambers in communication with the motor, a dump valve limiting communication of the inlet chamber with a drain in response to spring means and fluid communicated to the dump valve through a passage open to either of the service chambers when it is placed in communication with the inlet chamber by the control valve spool, the passage otherwise communicating the dump valve with a drain so that fluid communication between the inlet chamber and drain is limited only by the spring means. The force of the spring means may also be varied in certain embodiments of the invention. During operation of a second hydraulic motor by an additional control valve in communication with the inlet chamber, the dump valve is conditioned to provide pressure modulation in the inlet chamber by means of a bypass valve responsive to the additional control valve.

Claims11

Dependent claims

A fluid control circuit for regulating operation of a double-acting hydraulic motor and including first hydraulic motor means, a source of fluid under pressure, a control valve body defining a bore, an inlet chamber being in communication with the bore and the source, service chambers being respectively in communication with the control valve bore in axially spaced apart relation on opposite sides of the inlet chamber, drain means also being in communication with the control valve bore and a spool reciprocably arranged in the control valve bore and having a neutral position wherein the spool blocks the inlet chamber from communication with both service chambers, the spool being movable in opposite directions from its neutral position for respectively communicating the inlet chambers with the service chambers and drain means and comprising:

a dump valve forming a bore having one end in free communication with the inlet chamber, a dump spool being movably arranged in the dump valve bore for separating its one end from its other end, the dump valve bore having an opening in communication with drain, the dump spool being movable toward the one end of the dump valve bore to block the inlet chamber from the drain opening and toward the other end of the dump valve bore to communicate the inlet chamber with the drain opening, spring means urging the dump spool toward the one end of the dump valve bore;
means forming passages for communicating the other end of the dump valve bore with the service chambers and with the drain;
regulating means being movable with the control valve spool and in regulating communication with the passages to communicate the other end of the dump valve bore with the respective service chambers when they are placed in communication with the inlet chamber by the control valve spool and to communicate the other end of the dump valve bore with the drain when the control valve spool is in its neutral position;
and
second hydraulic motor means having an inlet passage in communication with the inlet chamber of the control valve, a bypass valve in responsive communication with the second motor means and normally providing communication for the passages from the service chambers with the other end of the dump valve bore, the bypass valve functioning in response to operation of the second motor means for directly communicating the other end of the dump valve bore with its one end, the dump valve then functioning as a pilot operated relief valve during operation of the second motor means.

2 more elements

A fluid control circuit for independently regulating operation of a first hydraulic motor and a second hydraulic motor, the circuit including a source of fluid under pressure, a first control valve having an inlet chamber in communication with the source, a service chamber in communication with the first motor and movable spool means for selectively communicating the inlet and service chambers, second control valve means in communication through the inlet chamber of the first control valve with the source and in operative communication with the second motor, comprising

a dump valve in communication with drain means and having a first chamber, a second chamber and piston means arranged therebetween the piston means being responsive to fluid pressure in the first chamber for tending to communicate the first chamber with the drain, spring means arranged for interaction with the piston means, the piston means tending to block communication between the first chamber and the drain in response to interaction with the spring means and also in response to fluid pressure in the second chamber,
regulating means operatively coupled with the spool means and in communication with the second chamber of the dump valve, the regulating means communicating the second chamber with the service passage when the spool means communicates the inlet and service chambers, and
bypass valve means in responsive communication with the second control valve means and in communication with the first and second chambers of the dump valve, the bypass valve means functioning in response to operation of the second motor by the second control valve means for communicating the second chamber with the first chamber and conditioning the dump valve for operation as a pilot-operated relief valve.

Dependencies are inferred from the claim text.

Facts

Application: 05/546,013Filed 31 Jan 1975 · division
Priority: 24 Apr 1974
Granted: 31 Aug 1976
Term ends: Not estimatedThe source records don’t support an estimate.

Classification27 codes

E02F 9/2267
Arrangements or adaptations of elements for hydraulic drives: valves or distributors
E02F 3/84
Component parts: drives or control devices therefor , e.g. hydraulic drive systems
E02F 9/2271
Arrangements or adaptations of elements for hydraulic drives: actuators and supports therefor and protection therefor
E02F 9/2285
Hydraulic circuits: pilot-operated systems

Family

Serial463,561Parent of this division · filed 24 Apr 1974
Serial211,333Parent of this division · filed 23 Dec 1974
3903787Parent of this division
3847180Parent of this division
US 3,977,301 AThis patent

From the US filing history. Foreign family members aren’t listed.