Hydraulic control

Abstract

Disclosed is a hydraulic control system that serves to supply a differential cylinder. An active logic valve designed as a 2 / 2-way valve is arranged in the line supplying the annular space of the differential cylinder. This valve enables active opening, active shutoff, and a check function in a differential circuit of the control system according to the invention. The opening pressure of the check function is determined by a pressure relief valve connected to the active logic valve. The opening, shutoff, and check functions are controlled by a pilot valve.

Description

The present invention relates to a hydraulic control for a differential cylinder according to the preamble of claim 1.In such hydraulic controls, the differential cylinder moves, for example, an upper tool so that it hangs on the differential cylinder. At this time, as various operating conditions of the upper tool, at least one of "down-going", "down-going", and "up-going" are required. The rapid traverse requires less pressure than the operation.Due to the different sizes of the piston crown surface and the annular surface on the cylinder piston or due to the different sizes of the piston crown space and the annular space of the differential cylinder, a pressure medium difference between the entering and the exiting pressure medium always results during each movement of the cylinder piston. If, for example, the cylinder piston is moved in such a way that the piston crown space is emptied, a pressure medium excess results which corresponds to the volume of the retracted section of the piston rod. When the annular space is emptied, a pressure medium deficiency results which corresponds to the volume of the extended section of the piston rod.US 6 003 429 A discloses a hydraulic cylinder device which can be moved at high speed and high load.The object of the invention is to provide a hydraulic control which, with a simple valve technology from a device standpoint, enables a rapid movement and an operation in an extension direction and a rapid movement in a retraction direction of a differential cylinder.This object is achieved by a hydraulic control having the features of claim 1.Further advantageous embodiments of the invention are described in the dependent claims.The claimed hydraulic control is used for supplying a differential cylinder, wherein a first working connection of the control can be connected to a piston crown space and a second working connection of the control can be connected to an annular space of the differential cylinder. A pump connection of the control can be connected to a pump and can be connected to the second working connection via a supply line. According to the invention, an active logic valve designed as a 2 / 2-way built-in valve with a large nominal width is arranged in the supply line or in its branch assigned to the second working connection. Via this, an active opening and an active shut-off of the supply line or of the branch and a passive recoil function in a differential circuit of the control according to the invention are possible. An opening pressure of the check function is determined by a pressure limiting valve which is connected to the active logic valve.The hydraulic control according to the invention, with the aid of a single 2 / 2-way built-in valve of large nominal size, fulfills the limitation of a system pressure (in the differential circuit) and the active blocking and the active opening (in all other operating modes) and thus simultaneously replaces two 2-way built-in valves of the prior art. This creates a hydraulic control which, with a simple valve technology from a device standpoint, enables a rapid traverse and an operation in an extension direction and a rapid traverse in a retraction direction of the differential cylinder in question. More specifically, the active logic valve allows the fast motion in the direction of retraction by its non-return function in differential connection with the control and the operation in the direction of extension by its shut-off and the fast motion in the direction of retraction by its orifice.The controller is preferably a press controller (e.g. scrap press controller) and the differential cylinder is an upper press cylinder. Then, the extension direction is directed downward and the retraction direction is directed upward.In a particularly preferred development, the active logic valve has a first connection and a second connection, both of which are connected to the supply line or the branch. Furthermore, the active logic valve has a control slide, by means of which the two connections can be disconnected from one another and connected to one another. A piston is fastened to the control slide, which piston delimits an annular space and a piston base space. The piston crown space is connected to an inlet of the pressure limiting valve. The size ratios of an annular surface of the annular space, an end surface at the first connection and a piston crown surface of the piston crown space also determine the opening pressure of the active logic valve in its non-return function.The piston head space can be further developed as a spring space with spring, so that the control slides initially shut off the two connections.In a particularly preferred embodiment, the end face of the control slide which is assigned to the first connection and acts in the opening direction and the annular face of the piston which is arranged in the annular space and acts in the opening direction are together as large as the piston face of the piston which acts in the closing direction in the piston crown space. Thus, the opening pressure of the active logic valve in its non-return function is determined by the pressure limiting valve in a pressure ratio of 1:1.The shut-off and the opening of the connections can be produced via respective switching positions of a pilot control valve which has a pump connection, a tank connection, a first control connection and a second control connection. The first control connection is connected to the piston crown space and the second control connection is connected to the annular space.The non-return function of the active logic valve in the differential circuit of the control according to the invention can be generated via a basic position or idle position of the pilot control valve, in which the two control connections and the pump connection are connected to one another. Preferably, the tank connection is shut off.A preferred development of the control according to the invention has a shuttle valve, the output of which is connected to the pump connection of the pilot control valve, and the first input of which is connected to the first connection of the active logic valve, and the second input of which is connected to the pump connection of the control.The supply line may have a common part which supplies both working connections of the controller and has a branch which is connected via a first branch to the first working connection and via the second branch to the second working connection. Then, the active logic valve is arranged in the second branch to control the second working port.In order to be able to report this to the pilot valve at high pressure at the second working port, a connection of the first inlet of the shuttle valve to a point of the second branch which is situated between the first port of the active logic valve and the second working port is preferred.For weight compensation, it is particularly preferred if a switchable pressure limiting valve is connected at a point of the second branch which lies between the first connection of the active logic valve and the second working connection. This can be activated in the working step of the differential cylinder.For controlling the second working connection, it is preferred if a first shut-off valve is arranged in the first branch.For controlling the second working connection, it is furthermore preferred if a line to a tank in which a second shut-off valve is arranged is connected in the first branch between the first shut-off valve and the first working connection. This is opened when the differential cylinder retracts.If a shut-off valve is arranged between a pump and the pump connection of the control, the cylinder piston can be stopped by closing it.An exemplary embodiment of a hydraulic control according to the invention is illustrated in the figure. The invention will now be explained in more detail with reference to the Figure.The FIGURE shows a circuit diagram of the exemplary embodiment of the hydraulic control according to the invention for supplying a differential cylinder 1 of a press.An upper tool 3 is rigidly connected to the cylinder piston 4 of the differential cylinder 1 and operates (rapidly travelling, reforming, punching or cutting) with suspended mass in a closing movement downwards.The suspended mass is the sum of the masses of the upper tool 3 and the cylinder piston 4 including a piston rod of the differential cylinder 1. The weight and an annular surface in the annular space 5 result in an acting load pressure.When the connection of a hydraulic energy supply via a supply line 7, in particular via its first branch 7 a, to a piston crown space 2 is enabled, the working pressure force of the prevailing pressure in the piston crown space 2 acts. When the connection of the hydraulic energy supply via the supply line 7, in particular via its second branch 7 b, to the annular space 5 is disconnected, the lifting force of the prevailing pressure in the annular space 5 acts. The piston crown surface of the piston crown space 2 is larger than the annular surface of the annular space 5.The hydraulic control according to the invention has a first working connection X 1 connected to the piston crown space 2, a second working connection X 2 connected to the annular space 5 and a pump connection P. The supply lines 7 extend therebetween with their branches 7 a, 7 b. The hydraulic energy supply, consisting of an adjustable pump 6, a pump pressure protection 8 and a shut-off valve 10 for energy isolation, is connected to the pump connection P. The hydraulic energy supply delivers an adjustable volume flow at a fixed operating pressure to the pump connection P.The working port X 2 is connected to a first port A of an active logic valve 12. The active logic valve 12 is incorporated in the hydraulic controller. A second port B of the active logic valve 12 is directly connected to the P port of the controller. A control slide 22 of the active logic valve 12 receives the main volume flow in both directions. More specifically, the main flow rate may be directed from the first port A to the second port B when the cylinder piston 4 descends, or directed from the second port B to the first port A when the cylinder piston 4 ascends.The second working connection X 2 is connected to a first inlet Z 1 of a shuttle valve 14. A second inlet Z 2 of the shuttle valve 14 is connected directly to the pump connection P. The shuttle valve 14 connects its first inlet Z 1 or its second inlet Z 2 to a control connection P of a pilot control valve 16, which is designed as a 4 / 3-way switching valve, due to the pressure.The working connection X 2 is connected to a switchable pressure limiting valve 18. In its basic position, the blocking function is effective and the pressure limiting valve is ineffective. In the excited state, the pressure limiting valve serves for weight compensation.The working connection X 2 is connected to a further pressure limiting valve 20. The pressure limiting valve 20 serves for pressure protection against pressure transmission in the event of a blocked malfunction of the active logic valve 12 or of the switchable pressure limiting valve 18. The pressure limiting valve 20 should be set at least 10% higher than the operating or load pressure required for startup.The control slide 22 of the active logic valve 12 is guided in a bushing and a piston of the control slide 22 is enlarged in diameter with respect to the bushing and is accommodated in a control cover. The active logic valve 12 has a control port A 1, via which a piston crown space 24 of the active logic valve 12 is connected to a control port A of the pilot control valve 16. The active logic valve 12 has a control connection B 1, via which an annular space 26 of the active logic valve 12 is connected to a control connection B of the pilot control valve 16. The two chambers 24, 26 are separated from each other by the piston of the control slide 22.The difference between the piston surface of the piston of the control slide 22 in the piston crown space 24 acting under pressure in the closing direction and the annular surface of the piston of the control slide 22 in the annular space 26 acting under pressure in the opening direction is equal to the end surface of the control slide 22 at the connection A acting under pressure in the opening direction. The control slide 22 is pressed into its rest position by a spring which is installed in the piston crown space 24 developed as spring space 24. In the rest position, the control slide 22 blocks the connection between the two connections A and B of the active logic valve 12.On the control slide 22, a seal is provided between the connection B and the annular chamber 26 for leakage-free separation. On the piston of the control slide 22, a seal for leakage-free separation is provided between the annular chamber 26 and the spring chamber 24.The active logic valve 12 is connected via its control connection A 1 to an inlet of a pressure limiting valve 30 and to the control connection A of the pilot control valve 16. The active logic valve 12 is connected via its second connection B to an outlet of the pressure limiting valve 30 and to an inlet of a first shut-off valve 28, which is designed as a switching valve, and to the second inlet Z 2 of the shuttle valve 14 and to the pump connection P of the control.At pilot valve 16, solenoids a, b can displace a spool and hydraulically act on the opening and blocking of ports A, B of active logic valve 12. Two equally strong springs of the pilot valve 16 act against one another and bias the slide piston in a rest position in which the control connections P, A and B are connected to one another while the connection T is disconnected therefrom. In this rest position, the pressure limitation by the pressure limiting valve 30 of the control according to the invention acts in its differential circuit.When the solenoid a pushes the slide piston of the pilot control valve 16 into a switching position in which, on the one hand, the connections P and B and, on the other hand, the connections A and T are connected, the active logic valve 12 is actively opened.When the solenoid b pushes the slide piston of the pilot control valve 16 into a switching position in which, on the one hand, the connections P and A and, on the other hand, the connections B and T are connected, the active logic valve 12 is actively blocked.During the closing downward movement of the cylinder piston 4, the pressure limiting valve 30 serves to compensate the load pressure in the annular chamber 5 of the differential cylinder 1. When the setting pressure is undershot, it closes. The pressure limiting valve 30 must be set higher than the load holding pressure.At the first shut-off valve 28, a magnet pushes a slide piston into an open position. A strong spring acts against the magnet and urges the spool to a rest position in which the pump port P of the controller is disconnected from the first working port X1.Between the first shut-off valve 28 and the first working connection X 1, a second shut-off valve 32 designed as a switching valve is connected. At the shut-off valve 32, a magnet pushes a slide piston into the closed position. A strong spring acts against the magnet and stresses the slide piston in the rest position, in which the first working connection X 1 is connected to the tank T.During operation of the control according to the invention in differential gear, a standstill of the cylinder piston 4 is initially assumed. All solenoid operated valves are at rest. All the slide pistons and the slide have reached their rest position.The actuated magnet on the second shut-off valve 32 closes this, working connection X 1 and tank T are disconnected. The actuated solenoid on the first shut-off valve 28 opens the latter.The shut-off valve 10 for energy isolation is deactivated. The adjustable pump 6 supplies the piston crown space 2 of the differential cylinder 1 and determines the travel speed of the cylinder piston 4 with the tool 3 downwards.The oil volume from the annular chamber 5 to the connection A of the active logic valve 12 is compressed. The pressure of the annular chamber 5 acts at the connection A of the active logic valve 12.At the same time, an unequal pressure ratio arises between the first inlet Z 1 (pressure of the second working port X 2) and the second inlet Z 2 (pressure of the first working port X 1) of the shuttle valve 14. The pressure of the second working port X 2 acts on the control port P of the pilot valve 16.The rest position of the slide piston of the pilot control valve 16 connects the spring chamber 24 and the annular chamber 26 of the active logic valve 12 to the inlet of the pressure limiting valve 30.The pressure of the second working connection X 2 also prevails in the spring chamber 24 and in the annular chamber 26 of the active logic valve 12. the hydraulic force in the spring chamber 24 acts against the hydraulic force in the annular chamber 26 and at the connection A of the active logic valve 12.As a result, the pressure limiting valve 30 can be set to the load pressure without a factor. When the setting pressure at the pressure limiting valve 30 is undershot, the control slide 22 of the active logic valve 12 remains in the closed idle position. The pressure medium in the second working connection X 2 is compressed. When the setting pressure at the pressure limiting valve 30 is exceeded, it opens and the control slide 22 of the active logic valve 12 opens from port A to port B at a limited pressure at the second working port X 2 corresponding to the set pressure of the pressure limiting valve 30, The pressure medium in the annular chamber 5 of the differential cylinder 1 continues to flow, in a pressure-limited manner, into the piston crown chamber 2. Thus, the control according to the invention is in differential connection.In operation without differential switching, the second shut-off valve 32 is shut off. The first shut-off valve 28 is open. The pressure limiting function is enabled at the switchable pressure limiting valve 18. The shut-off valve 10 for energy isolation is deactivated. The variable displacement pump 6 supplies the piston head space 2 of the differential cylinder 1 and determines the downward travel speed. The actuated solenoid b on the pilot valve 16 connects on the one hand the control ports P and A and on the other hand the control port B to the tank T.The pressure of the working connection X 2 prevails in the spring chamber 24 of the active logic valve 12, while the annular chamber 26 is pressureless. An unequal force ratio is obtained between the connection A and the spring chamber 24 on the control slide 22, the control slide 22 closing. The connections A and B of the active logic valve 12 are separate.As a result, the pressure limiting valve 30 closes because the opening pressure (=adjusted load pressure plus pressure at the first working connection X 1) is undershot. The pressure medium at the working connection X 2 is compressed.When the setting pressure at the pressure limiting valve 18 is exceeded, it opens and limits the pressure at the working connection X 2 in accordance with the set pressure. The pressure medium from the annular chamber 5 of the differential cylinder 1 flows back in the pressure-limiting direction of the tank T. Thus, the control according to the invention is without differential switching.Decompression is effected by opening both shut-off valves 28, 32. The pressure at the working connection X 1 decreases. The hydraulic energy supply is pressureless. When the setting pressure at the switchable pressure limiting valve 18 falls below, it closes. The cylinder piston 4 is stationary.After decompression, the cylinder piston 4 is raised by the first working connection X 1 being relieved of load via the second shut-off valve 32 to the tank T. At the first shut-off valve 28, the magnet is de-energized, the slide piston pushes into the closed locking position by the spring force. The working connection X 1 is pressureless.The pressure limiting function is switched off at the switchable pressure limiting valve 18. The actuated solenoid a on the pilot valve 16 pushes the slide piston into the switching position in which, on the one hand, P and B and, on the other hand, A and T are connected.The shut-off valve 10 is deactivated. The adjustable pump 6 acts on the second port Z 2 of the shuttle valve 14. When the load-holding pressure is exceeded from the annular chamber 5 of the differential cylinder 1, the piston of the shuttle valve 14 pushes in the direction of the first inlet Z 1 (pressure at the second working port X 2) and blocks it. The second inlet Z 2 of the shuttle valve 14 is then connected to the control connection P of the pilot control valve 16. The pressure of the pump 6 thus prevails in the annular chamber 26 of the active logic valve 12, while the spring chamber 24 is pressureless. An unequal force ratio results and the control slide 22 opens actively. The pressure medium flows from the connection B to the connection A of the active logic valve 12.The variable displacement pump 6 supplies the annular chamber 5 of the differential cylinder 1 and determines the upward travel speed. The pressure medium of the piston crown space 2 flows in a non-pressurized manner to the tank T.To achieve a standstill after the start-up, the shut-off valve 10 disconnects the energy supply from the controller. The first shut-off valve 28 is closed. The second shut-off valve 32 is open. The spool of the pilot valve 16 goes to the rest position, the control ports P, A and B are connected, and the tank port T is disconnected therefrom.The pressure medium from the annular chamber 5 to the first connection A of the active logic valve 12 is compressed by the load pressure. The hydraulic force acts on the first connection A. At the same time, the pressures at the two inputs Z 1, Z 2 of the shuttle valve 14 are balanced. The piston on the shuttle valve 14 closes off the second inlet Z2. The first inlet Z 1 is connected to the control port P of the pilot valve 16. The load pressure at the second working port X 2 acts at the control port P of the pilot valve 16.The load pressure prevails in the spring chamber 24 and the annular chamber 26 of the active logic valve 12. The valve spool 22 closes. The connections A and B of the active logic valve 12 are separated without leaking oil. The cylinder piston 4 is stationary.A hydraulic control system is disclosed which serves to supply a differential cylinder. In its line supplying the annular chamber of the differential cylinder, an active logic valve designed as a 2 / 2-way valve is arranged. Via this, an active opening and an active shut-off and a recoil function in a differential circuit of the control according to the invention are possible. An opening pressure of the check function is determined by a pressure limiting valve which is connected to the active logic valve. The opening, the shut-off and the non-return function are switched by a pilot valve.List of reference characters1 Differential cylinder 2 Piston crown space 3 Upper tool 4 Cylinder piston 5 Annular space 6 Adjustable pump 7 Supply line 7 aFirst branch 7 bSecond branch 8 Pump pressure protection 10 Shut-off valve 12 Active logic valve 14 Shuttle valve 16 Pilot valve 18 Switchable pressure limiting valve 20 Pressure limiting valve 22 Control slide 24 Piston crown space / spring space 26 Annular space 28 First shut-off valve 30 Pressure limiting valve 32 Second shut-off valve a, b Magnet A First connection / First control connection B Second connection / Second control connection A 1 First control connection B 1 Second control connection P Pump connection / control connection X 1 First working connection X 2 Second working connection Z 1 First input Z 2 Second input T Tank / tank connection g Acceleration due to gravity

Claims

Hydraulic control for a differential cylinder (1), wherein a first working connection (X1) of the control can be connected to a piston crown space (2) and a second working connection (X2) of the control can be connected to an annular space (5) of the differential cylinder (1), and wherein a pump connection (P) of the control can be connected to the second working connection (X2) via a supply line (7, 7b), characterized in that an active logic valve (12) is arranged in the supply line (7b), via which active opening of the supply line (7b) and active blocking of the supply line (7b) and a passive non-return function are possible, wherein an opening pressure of the non-return function is determined by a pressure limiting valve (30).Control according to claim 1, wherein the active logic valve (12) has a first port (A) and a second port (B), both of which are connected to the supply line (7b), and wherein the active logic valve (12) has a control slide (22), via which the two ports (A, B) can be separated from one another and connected to one another, and wherein a piston which delimits an annular space (26) and a piston crown space (24) is fastened to the control slide (22), wherein the piston crown space (24) is connected to the pressure limiting valve (30).Control according to claim 2, wherein an end face of the control slide (22) which is arranged on the first connection (A) and acts in the opening direction and an annular surface of the piston which is arranged in the annular space (26) and acts in the opening direction are together as large as a piston surface of the piston which acts in the closing direction in the piston base space (24).Control according to one of Claims 2 or 3, wherein the shut-off and the opening of the connections (A, B) can be produced via respective switching positions of a pilot control valve (16) which has a pump connection (P), a tank connection (T), a first control connection (A) and a second control connection (B), wherein the first control connection (A) is connected to the piston crown space (24), and wherein the second control connection (B) is connected to the annular space (26).Control according to Claim 4, wherein the non-return function can be generated via a basic position or rest position of the pilot control valve (16), in which the two control connections (A, B) and the pump connection (P) are connected to one another.Controller according to Claim 4 or 5, having a shuttle valve (14), the output of which is connected to the pump connection (P) of the pilot valve (16), a first input (Z1) of the shuttle valve (14) being connected to the first connection (A) of the active logic valve (12), and a second input (Z2) of the shuttle valve (14) being connected to the pump connection (P) of the controller.Controller according to one of the preceding claims, wherein the supply line (7, 7a, 7b) has a branch which is connected via a first branch (7a) to the first working connection (X1) and via a second branch (7b) to the second working connection (X2), and wherein the active logic valve (12) is arranged in the second branch (7b).Controller according to Claim 7, wherein the first inlet (Z1) of the shuttle valve is connected to a point of the second branch (7b) which is situated between the first connection (A) of the active logic valve (12) and the second working connection (X2).Controller according to Claim 7 or 8, wherein a switchable pressure limiting valve (18) is connected to a location of the second branch (7b) which is situated between the first connection (A) of the active logic valve (12) and the second working connection (X2).Controller according to one of Claims 7 to 9, wherein a first shut-off valve (28) is arranged in the first branch (7a).Controller according to claim 10, wherein in the first branch (7a), between the first shut-off valve (28) and the first working port (X1), a line is connected to a tank (T) in which a second shut-off valve (32) is arranged.Controller according to one of the preceding claims, wherein a shut-off valve (10) is arranged between a pump (6) and the pump connection (P) of the controller.

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