US 4,066,006 AGranted

Flow regulating system

AssigneeRobert Bosch GmbH

InventorJoachim Heiser

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Abstract

A main valve controls the flow to a load in a first or second direction depending upon the signal applied to a pilot valve. A spool of the main valve is biased to a central position blocking flow by springs. A throttle valve having an adjustable restrictor area is connected in one line between the main valve and the load. The restrictor area is adjusted in correspondence to an input signal. The spool is moved to a first or second extreme position by the pilot valve. The pressure difference developed across the throttle valve is applied to the spool in a direction to force the spool towards the central position. The spool is balanced at a predetermined pressure difference across the throttle valve. A relief valve is furnished in an inlet line to the main valve so that a reversal of pressure medium flow through the load causes an excess pressure difference across the throttle valve and thereby moves the main valve spool to the other of its two operating positions in turn causing a substantial pressure increase in the inlet line causes operation of the relief valve and thereby braking of the load.

Claims15

Dependent claims

In combination with a pressure-responsive actuator having a pair of connections pressurizable for operating said actuator, a hydraulic system comprising:

first and second load supply lines each connectable to a respective one of said connections;
a source of fluid under pressure having a high-pressure side and a low-pressure side;
a main control valve connected between said load supply lines and said source and having a movable control member displaceable between a first end position connecting said first line to said high-pressure side and said second line to said low-pressure side, a second end position connecting said second line to said high-pressure side and said first line to said low-pressure side, and an intermediate central position blocking fluid flow between said high-pressure and low-pressure sides and said supply lines, said control valve having means including a pair of oppositely effective springs bearing on said member for urging said member into said central position;
means responsive to a direction signal and including a pilot valve connected to said member of said main control valve for displacing same into one of said end positions in dependence upon said direction signal;
a restriction in one of said load supply lines and forming a variable flow passage displaceable between a relatively wide position and a relatively narrow position, whereby the pressure differential across said restriction is greater in said narrow position than in said wide position;
pressure-responsive means connected to said one load supply line to both sides of said restriction and connected to said main control valve for applying the pressure differential across said restriction to said main control valve in said first position thereof in a direction urging said main control valve into said second position and in said second position thereof in an opposite direction urging said main control valve into said first position, said pressure-responsive means including a pair of pistons bearing each in a respective direction through a respective spring on said member and each having an inner face turned toward said member and engaging the respective spring and an outer face turned away from said member, a pair of inner chambers each between a respective inner face and said member, and a pressure line between each of said inner chambers and a respective side of said restriction;
and
electrical actuating means connected to said restriction for generating an input signal and displacing said restriction between said wide and narrow positions therewith, said direction signal responsive means including a pair of outer chambers each at a respective outer piston face and a pressure line between each of said outer chambers and a respective portion of said pilot valve.

5 more elements

In a combination with a pressure-responsive actuator having a pair of connections pressurizable for operating said actuator, a hydraulic system comprising:

first and second load supply lines each connectable to a respective one of said connections;
a source of fluid under pressure having a high-pressure side and a low-pressure side;
a main control valve connected between said load supply lines and said source and having a movable control member displaceable between a first end position connecting said first line to said high-pressure side and said second line to said low-pressure side, a second end position connecting said second line to said high-pressure side and said first line to said low-pressure side, and an intermediate central position blocking fluid flow between said high-pressure and low-pressure sides and said supply lines, said control valve having means including at least one spring bearing on said member for urging said member from a one of said end positions into said central position;
means responsive to a direction signal and including a pilot valve connected to said member of said main control valve for displacing same into one of said end positions in dependence upon said direction signal;
a restriction in one of said load supply lines forming a variable flow passage therein and displaceable between a relatively wide position and a relatively narrow position, whereby the pressure differential across said restriction is greater in said narrow position than in said wide position;
pressure-responsive means connected to said one load supply line to one side of said restriction and connected to said main control valve for applying the pressure at said one side of said restriction to said main control valve in said one end position thereof in a direction urging said main control valve into the other end position, said pressure-responsive means including a piston having an inner face bearing via said spring on said member and an outer face turned away from said member, an inner chamber between said inner face and said member, and a pressure line between said inner chamber and said one side of said restriction;
and
electrical actuating means connected to said restriction for generating an input signal and displacing said restriction between said wide and narrow positions therewith, said direction signal responsive means including an outer chamber at said outer piston face and a pressure line between said outer chamber and said pilot valve.

5 more elements

Dependencies are inferred from the claim text.