Loading pressure compensation type logic valve

• US 5,174,329 A
• Filed: 10/16/1991
• Issued: 12/29/1992
• Est. Priority Date: 10/18/1990
• Status: Expired due to Fees

• Current Assignee: Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Original Assignee: Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Inventors: Shimada, Yoshiyuki, Yoshino, Kazunori
• Primary Examiner(s): Michalsky, Gerald A.
• Application Number:
  US07/778,349
• Time in Patent Office: 440 Days
• Field of Search: 91/446, 137/501, 137/614.18, 137/625.3, 251/29
• US Class Current: 137/501
• CPC Class Codes: G05D 16/187 using pistons within the main valve
• CPC Class Codes: Y10T 137/7788 Pressures across fixed choke
• CPC Class Codes: Y10T 137/86734 With metering feature
• CPC Class Codes: Y10T 137/88038 One valve head carries other valve head

Abstract

A fluid-operated valve includes a control spool, actuated by a source of pilot pressure to control a pilot flow of fluid from a loading pressure inlet port to a drain line. The pilot flow passes a throttle which reduces the fluid pressure acting in one direction, thereby performing stroke compensation of the actuation of a valve poppet. A differential pressure compensation valve is moved to partially block fluid flow to a rate control orifice group in response to a difference in pressure on the two sides of the rate control orifice group to control further the actuation of the valve poppet, whereby differential pressure is compensated.

Claims

1. A loading pressure compensation logic valve comprising:

a housing;

a valve poppet slidably fitted in said housing;

a flow rate control orifice group in a cylindrical portion movable with said valve poppet;

a loading pressure chamber facing an end of said valve poppet where said cylindrical portion is located;

a loading pressure inlet port connected to said loading pressure chamber;

a poppet spring chamber facing an opposed end of said valve poppet;

an orifice connecting said loading pressure inlet port to said poppet spring chamber;

a poppet spring in said poppet spring chamber;

said poppet spring being preloaded to urge said valve poppet toward a poppet seat;

a flow rate control chamber within said flow rate control orifice group;

a drain chamber on a side of said poppet seat opposite to said flow rate control chamber;

a control spool;

a spool seat in said valve poppet;

a spool spring effective for urging said control spool into sealing contact with said spool seat;

means for controlling a force on said control spool in response to an outside pilot pressure;

said control spool being exposed to a pressure in said poppet spring chamber;

a pressure transfer spool in said valve poppet for conveying a force developed by pressure from said loading pressure chamber to said control spool;

a differential pressure compensation orifice in said valve poppet, at a position closer to the loading pressure inlet port than is said flow rate control orifice group;

a valve spring chamber connecting said differential pressure compensation orifice to said flow rate control orifice group;

a differential pressure compensation valve radially disposed between said pressure transfer spool and said flow rate control orifice group;

a valve spring in said valve spring chamber;

said differential pressure compensation valve being slidable in an axial direction and pushed by said valve spring in a direction effective to open said differential pressure compensation orifice, thereby controlling a degree of opening of said differential compensation orifice;

a larger diameter pressure chamber adjacent an end of said differential pressure compensation valve, facing in a direction of urging of said valve spring;

means for connecting said larger diameter pressure chamber to said valve spring chamber; and

a smaller diameter pressure chamber adjacent another end of said differential pressure compensation valve and connected to said flow rate control chamber through an orifice.

2. A loading pressure compensation valve comprising:

means for admitting a loading pressure to said loading pressure compensation valve;

a control spool;

means for applying equal forces in opposed directions on said control spool in the absence of flow through said loading pressure compensation valve;

said means for applying equal forces including a direct means in a first direction, and a throttled means in a second direction;

a spool seat;

resilient means for urging said control spool into sealing contact with said spool seat;

a drain past said spool seat;

means, responsive to an external pilot pressure for urging said spool out of contact with said spool seat, whereby a fluid is permitted to flow from said means for admitting a loading pressure to said drain;

said throttled means reducing a pressure in said second direction, whereby said direct means tends to urge said control spool in a direction opposing action of said external pilot pressure;

a valve poppet axially movable in said loading pressure compensation valve;

a poppet seat sealingly seating said valve poppet;

a flow rate control chamber on a first side of said poppet seat;

a drain port on a second side of said poppet seat;

a valve spring effective for urging said valve poppet into sealing contact with said poppet seat;

a rate control orifice group in a cylindrical portion of said poppet;

a differential pressure compensation valve in said cylindrical portion;

a valve spring chamber in said cylindrical portion surrounding a portion of said differential pressure compensation valve;

said rate control orifice group being effective, when said valve poppet is moved axially, for permitting fluid flow from said valve spring chamber to said flow rate control chamber;

a larger diameter portion in a larger diameter pressure chamber at a first end of said differential pressure compensation valve;

a smaller diameter portion in a smaller diameter pressure chamber at a second end of said differential pressure compensation valve;

said valve spring chamber being disposed between said larger diameter portion and said smaller diameter portion;

means for blocking said rate control orifice group when said valve poppet is in its sealing position against said poppet seat;

first and second areas on said valve poppet;

said first and second areas being substantially equal;

means for exposing said first area to said loading pressure;

means for exposing said second area to said throttled means, whereby said valve remains balanced in an absence of fluid flow past said control spool, and becomes unbalanced in the presence fluid flow past said control spool;

an orifice connecting said loading pressure to said spring chamber; and

means, in the presence of a pressure difference in said spring chamber and said flow rate control chamber, to move said differential pressure compensation valve in a direction effective to permit said larger diameter portion to block said orifice, whereby a fluid pressure in said spring chamber is reduced, and differential pressure is compensated.