Hydraulic control device

• US 4,119,016 A
• Filed: 07/01/1976
• Issued: 10/10/1978
• Est. Priority Date: 07/24/1975
• Status: Expired due to Term

• Current Assignee: Komatsu Dresser Company (Komatsu Ltd.)
• Original Assignee: International Harvester Co. (CNH Industrial N.V.)
• Inventors: Pfeil, Christian, Breidenbach, Hans
• Primary Examiner(s): Cohen, Irwin C.
• Application Number:
  US05/701,475
• Time in Patent Office: 831 Days
• Field of Search: 417/211.5, 417/309, 417/307, 417/299, 137/399, 137/389, 137/413, 60/403, 60/468, 60/494, 91/442, 91/268, 91/461, 91/304, 91/452, 91/449, 91/438, 91/450
• US Class Current: 91/449
• CPC Class Codes: F04B 49/025 by means of floats
• CPC Class Codes: F15B 1/26 Supply reservoir or sump assemblies
• CPC Class Codes: Y10T 137/7297 With second diverse control
• CPC Class Codes: Y10T 137/7326 Low level safety cut-off
• CPC Class Codes: Y10T 137/7371 Fluid pressure

Abstract

A hydraulic control device for use in a hydraulic system having a pump supplying fluid from a reservoir to a working circuit. The control device detects leaks in the working circuit by monitoring the level of hydraulic fluid in the reservoir. In the event of a drop in the level of hydraulic fluid beyond a predetermined low level, the control device automatically diverts the fluid output side of the pump to the fluid input side to prevent further loss of fluid in the working circuit and to safeguard against cavitation in the pump due to the low level of fluid in the reservoir. The control device also senses excessive pressure peaks in the working circuit and operates to relieve the excessive pressure peaks by automatically venting a portion of the fluid on the output side of the pump to the reservoir.

Claims

1. A hydraulic power system of the type comprising a hydraulic power consumer unit, a hydraulic power source having fluid delivery and suction sides, a fluid reservoir including fluid therein at a predetermined system operational level, a float valve positioned in the reservoir and having a plunger valve linked by a lever arm to a float member, the plunger valve having a closed position when the fluid in the reservoir is at the system operational level and an open position when the fluid in the reservoir drops below the system operational level, a suction conduit having an open end positioned in the fluid in the reservoir below the operational level thereof and an opposite end connected to the suction side of the source, CHARACTERIZED BY:

a two position fluid flow diverter valve having a fluid inlet line connected to the fluid delivery side of the source and a fluid feed line connected to the unit and a fluid short circuit means connected to the suction side of the source, the diverter valve having an axially moveable valve spool means acted upon at one side by a spring and acted upon at an opposite side by fluid pressure in a chamber in the diverter valve whereby when the fluid pressure in the chamber exceeds the force of the spring it shifts the valve spool means to the first position of the diverter valve against the force of the spring and connects the inlet line to the fluid feed line and when the force of the spring exceeds the pressure of the fluid in the chamber it shifts the valve spool means to the second position of the diverter valve and connects the inlet line to the fluid short circuit means;

an axially adjustable stop means in the diverter valve chamber for limiting the axial displacement of the valve spool means in the second position of the diverter valve thereby controlling the rate of fluid flow from the inlet line to the short circuit means in said second position of the diverter valve;

a first control line including fluid flow restriction means therein restrictively connecting the delivery side of the source to the diverter valve chamber; and

a second control line connecting the diverter valve chamber to a float valve chamber;

the plunger valve closing the float valve chamber from communication with the reservoir in the closed position of the float valve and opening communication in the open position thereof whereby the diverter valve chamber is depressurized and the valve spool means is shifted by the spring to the second position of the diverter valve;

the valve spool means having three control surfaces arranged at axially spaced-apart intervals to each other, one control surface arranged on the spring side of the diverter valve and having an opening therethrough connecting the spring side to the suction side of the source, a second control surface arranged on the chamber side of the diverter valve and interacting with the stop means, and the third control surface arranged between the other two control surfaces controlling fluid flow at the delivery and suction sides of the source.