Hydraulic control device

Claim 2

A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages; a reversing valve mounted on said housing and communicating with said guide; at least one anticipatory control-pressure valve mounted on said housing and communicating with said guide; said reversing valve controlling displacement of said main control valve to open and close a first channel connecting the passage for connection of a source of hydraulic medium under pressure to the passage for connection to a pusher consumer, and controlling opening and closing of a second channel connecting the passage for connection to a pressure consumer to the passage for connection to a return flow collector; each anticipatory control pressure valve being operable to effect a further displacement of said main control valve to determine the effective flow area of each of said channels; an auxiliary piston displaceable in a chamber in said housing which is coaxial with said guide, said auxiliary piston being operatively associated with said main control valve; and an adjustable feeler extending coaxially into said chamber for said auxiliary piston and engageable with said auxiliary piston to limit movement of said auxiliary piston and said main control valve in one axial direction to determine the minimum flow area of said second channel.

Claim 3

A hydraulic control device, as claimed in claim 1, in which each anticipatory control valve is manually adjustable.

Claim 4

A hydraulic control device, as claimed in claim 1, including electric means operable to adjust automatically each anticipatory control pressure valve.

Claim 5

A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages, said passages including, considered axially of said guide, a first end passage for connection to a source of hydraulic medium under pressure, a second intermediate passage for connection to a pressure consumer, and a third end passage for connection to a return flow collector; said bore being radially enlarged at axially spaced locations therealong to form first, Second and third chambers communicating, respectively, with said first end passage, said second intermediate passage and said third end passage; said main control valve being formed with a land, intermediate its length, controlling communication between said first end passage and said second intermediate passage, and controlling communication between said second intermediate passage and said third end passage; said main control valve being formed with two end lands spaced axially in opposite directions from said intermediate land; said main control valve being formed with a first annular groove extending between one end land and said intermediate land and a second annular groove extending between said intermediate land and the other end land; said first annular groove, in a selected position of said valve, defining a flow channel interconnecting said first and second chambers, and said second annular groove, in the opposite position of said main control valve, defining a flow passage interconnecting said second and third chambers; said guide being formed with a fourth chamber adjacent one end of said main control valve and with a fifth radially enlarged chamber adjacent the opposite end of said valve; an auxiliary piston reciprocable axially in said fifth chamber and having a stem extending into said bore; a spring seated in said opposite end of said main control valve and engaged with said stem; and an adjustable tubular feeler projecting into said fifth chamber and engageable with the outer end of said auxiliary piston, to limit displacement of said main control valve toward said fifth chamber.

Claim 6

A hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages, said passages including, considered axially of said guide, a first end passage for connection to a source of hydraulic medium under pressure, a second intermediate passage for connection to a pressure consumer, and a third end passage for connection to a return flow collector; said bore being radially enlarged at axially spaced locations therealong to form first, Second and third chambers communicating, respectively, with said first end passage, said second intermediate passage and said third end passage; said main control valve being formed with a land, intermediate its length, controlling communication between said first end passage and said second intermediate passage, and controlling communication between said second intermediate passage and said third end passage; said main control valve being formed with two end lands spaced axially in opposite directions from said intermediate land; said main control valve being formed with a first annular groove extending between one end land and said intermediate land and a second annular groove extending between said intermediate land and the other end land; said first annular groove, in a selected position of said valve, defining a flow channel interconnecting said first and second chambers, and said second annular groove, in the opposite position of said main control valve, defining a flow passage interconnecting said second and third chambers; said guide being formed with a fourth chamber adjacent one end of said main control valve and with a fifth radially enlarged chamber adjacent the opposite end of said valve; an auxiliary piston reciprocable axially in said fifth chamber and having a stem extending into said bore; a spring seated in said opposite end of said main control valve and engaged with said stem; and an adjustable tubular feeler projecting into said fifth chamber and engageable with the outer end of said auxiliary piston, to limit displacement of said main control valve toward said fifth chamber.

Claim 7

A hydraulic control device, as claimed in claim 4 including an electromagnetically operated reversing valve mounted on said housing; passage means in said housing connecting said reversing valve to said first and fourth chambers for supply thereto and exhaust therefrom of a pressure medium to control displacement of said main control valve; at least one anticipatory control pressure valve mounted on said housing; and further passage means connecting said anticipatory control pressure valve to said fourth chamber to supply operating fluid under pressure thereto or to exhaust operating fluid therefrom to modulate the axial position of said main control valve as set by said reversing valve to vary the effective cross-sectional area of said channels; said main control valve being formed with an axial passage therethrough extending from said opposite end thereof and communicating, through a cross bore, with said second chamber; said auxiliary piston being formed with passage means therethrough interconnecting the portions of said fifth chamber on opposite sides of said auxiliary piston.

Claim 8

A hydraulic control device, as claimed in claim 5, in which said housing comprises a single valve body acting as a slide valve housing; each anticipatory control-pressure valve, said electromagnetically operated reversing valve and said auxiliary piston acting conjointly with said single main control valve and said single valve body to perform, selectively, the following functions: a. establishment of a connection between a source of hydraulic medium under pressure and a pressure consumer by establishing a connection between said first and second chambers; b. reduction of the pressure of the hydraulic medium or the amount of the hydraulic medium in a line connected to said second intermediate passage and to the pressure consumer, to an infinitely variable and predetermined value; c. interruption of the connection between a source of hydraulic medium under pressure and the pressure consumer by interrupting communication between said first and second chambers; d. simultaneously with such interruption establishing a connection between the pressure consumer and the flow connector by establishing a connection between said second and third chambers; and e. production of an infinitely variable and predeterminable resistance between said second chamber, connected to the pressuRe consumer, and said third chamber, connected to the return flow collector, with the hydraulic medium being displaced from the pressure consumer into said second intermediate passage and said second chamber by an external force acting on the pressure consumer.