WO1998038430A1

WO1998038430A1 - Pilot stop valve

Info

Publication number: WO1998038430A1
Application number: PCT/DE1998/000111
Authority: WO
Inventors: Heinz Schulte
Original assignee: Mannesmann Rexroth Ag
Priority date: 1997-02-27
Filing date: 1998-01-13
Publication date: 1998-09-03
Also published as: EP0963518A1

Abstract

The invention relates to a pilot stop valve comprising a pilot element (540) in a main piston (520) by means of which the ratio between the hydraulic resistance of a first nozzle device (122, 541, 543a, 543b, 524) in the main piston and the hydraulic resistance of a second nozzle device (123) in the main piston can be modified. The first nozzle device is linked to a connection which is preferably attached to a pump, and the second nozzle device is joined to a connection which is preferably attached to an actuator cylinder of a consumer element. By appropriately controlling the pilot element (540) the ratio between the hydraulic resistances of the respective nozzle devices can be modified and as a result the actuator cylinder can be moved in and out rapidly or slowly.

Description

description

Pilot operated check valve

The present invention relates to a pilot operated check valve that can be used, for example, in mobile hydraulics.

The use of hydraulics in moving machines has increased in recent years. This is especially true for earth-moving machines, industrial trucks, agricultural tractors and self-propelled harvesting machines. Since hydrostatic travel drives allow speed control without shifting, but are not very efficient, hydraulic drives are not primarily geared towards the forward movement. The main area of application of hydraulic drives can be seen in the operation of work organs.

In the case of agricultural vehicles, the working elements can be provided both on the agricultural tractor, which is used for pushing, carrying and driving agricultural and forestry equipment, and on the agricultural and forestry equipment itself. The use of hydraulically controlled working cylinders in the hoist is particularly important. Here, e.g. in the case of plowing the lifting mechanism on the tractor and in the case of plowing a lifting mechanism hydraulically fed by the tractor on the harrow. The cylinder is either extended or retracted depending on the operating mode.

In order to shut off the working group under pressure and to avoid creeping movements of the working cylinder, an unlockable one is installed between the pump and the working cylinder

Stop valve switched. This check valve can either can be unlocked hydraulically or electromagnetically. The advantage of electromagnetic unlocking is that the unlocking can be carried out optimally over time and that the energy loss is lower with frequently changing operating states.

European patent application 90 312 061.6 discloses a solenoid valve which is constructed similarly to a simple check valve, but which has the following special feature: the pressure at the working connection, which acts in a pressure chamber, acts on the base of the piston of the solenoid valve. A pilot control chamber is formed in the piston as a chamber which is connected to the pressure chamber via a recess in the base of the piston. The pressure of the pressure connection is applied to the piston skirt. A connection recess between the space and the pressure connection via the wall of the piston skirt is not provided. The valve can thus only be opened by lifting the piston off a seat edge, as a result of which a certain fluid flow suddenly flows through the shut-off valve. Proportional control with predetermined behavior cannot be carried out for low volume flows.

From the German patent application 196 46 425.0 a check valve for a safety circuit is known which has two flow positions. The check valve is located in front of a working cylinder. To slowly extend the working cylinder, an electromagnet in the non-return valve is fully energized so that the fluid between the pump and working cylinder can flow through two bores, one of which throttles more. The electromagnet is not energized to quickly extend the working cylinder, which means that the valve works as a simple check valve. To slow down, a small current is applied to the electromagnet, - 2.- so that the fluid between the pump and the working cylinder can flow through two holes, the other of the holes throttling more. The electromagnet is fully energized for rapid lowering, so that the same opening of the two holes results as when slowly extending. In the case of rapid lowering, however, the non-return piston also rises. The volume flow through the valve is thus controlled by setting two flow positions through the electromagnet.

From the document DE 40 30 952 AI, a finely controllable shut-off valve for a hydraulic working cylinder is known, in which the lowering of the working cylinder can take place proportionally. This lowering brake valve throttles the pressure medium flowing back from the working cylinder in order to prevent the load on the working cylinder from leading ahead or "jerking" of the working cylinder.

As shown in FIG. 1, 13 cylinder spaces 42, 43, 44 are located axially one behind the other in a valve housing 21 of the known valve 13. The valve housing 21 also has a valve seat 24 with which a valve member 35 can be in contact. The cylinder space 43 is connected to the working cylinder 14. The cylinder space 42 can optionally be connected to a pump 10 or a tank 11 via a 3/2-way valve 12. The operation of the valve 13 is controlled by energizing a proportional magnet 32.

The function of the finely controllable shut-off valve 13 is described below.

When lifting, the valve member 35 has the function of the piston of a simple check valve, ie that the valve member 35 from a certain pressure in the pressure chamber 42nd - - takes off from valve seat 24. As a result, the working cylinder 14 extends. A pressure chamber 47 of the valve member 35 is supplied with pressure fluid from the pressure chamber 43 via a bore 51 in the valve member 35, which serves to dampen the opening movement of the valve member 35. The opening movement of the valve member 35 is not controlled via the proportional magnet 32.

When lowering, which can be controlled proportionally in contrast to lifting, a voltage is applied to the proportional magnet 32, which causes a plunger 34 to move upwards and a control sleeve 53 is raised by the movement of its cross pin 59. As a result, a transverse bore 49 and a fine control notch 50 in the valve member 35 are exposed as a function of the voltage level at the proportional magnet 32. The fluid from the working cylinder 14 can therefore flow via the pressure chamber 43, the bore 51, the pressure chamber 47, the transverse bore 49 and the fine control notch 50 into a stepped bore 58 and via a notch 60 into a control sleeve 53 into the pressure chamber 42, the latter takes up low volume flow of the fluid, the fluid being returned to the tank 11 via the position I of the valve 12.

If the voltage on the proportional magnet 32 is increased, the pressure in the pressure chamber 42 increases. From a certain pressure level, the valve member 35 opens with respect to the valve seat 24 due to the pressure on the valve member 35. At the same time, the opening cross section of the transverse bore 49 and the fine control notch 50 decreases.

With this check valve, proportional control of the speed of the load is only possible when the working cylinder 14 is lowered. The object of the present invention is to better adapt the speed control to a desired behavior of the working cylinder, both when retracting and when extending a working cylinder. In addition, the shut-off valve should have a simple structure, switch effectively with little effort in terms of activation, and switch with high security in the case of dirt particles in the fluid.

This object is achieved by the check valve from claim 1.

A port A and port B can be connected to one another by a main piston in the check valve. For this purpose, there is a pilot control element in the main piston, by means of which a ratio of the hydraulic resistance of a first nozzle device, which connects port A to a rear control chamber on the main piston, to the hydraulic resistance of a second nozzle device, which connects the rear control chamber to port B, can be influenced . In the starting position of the pilot control element, the first nozzle device is closed and the second is open. In a first actuation position of the pilot control element after an initial stroke of the pilot control element, such a ratio of the hydraulic resistances is set that the main piston remains closed. When the pilot control element is actuated further, the ratio of the hydraulic resistances increases, so that the main piston opens from a predetermined actuation position. Thus, with a pump at port A and a consumer at port B, such a mode of operation can be used to slowly lift a working cylinder of a consumer. - έ -

In the first exemplary embodiment of the pilot-operated check valve according to the present invention, there is a first recess in a main piston as the first nozzle device and a control piston. When the control piston is actuated, a control edge on the control piston can change, in particular open, the opening cross section of a second recess as a second nozzle device in the main piston, the first recess being open. If the second recess is connected to a pressure chamber of the working cylinder via a connection B and the pressure from the pump is present at the first recess via a connection A, the extension of the working cylinder can be done by changing the position of the control edge and exposing it the second recess in the main piston can be controlled proportionally. As a result, the application range of the check valve can be expanded, in particular in agricultural vehicles, and the operational safety of the working cylinder can be increased at the same time.

Such a shut-off valve is actuated as follows for the proportional extension of the working cylinder: from a rest position of the control piston in which the first recess is closed, the second recess in the main piston is closed by the control collar of the control piston and the first recess is opened, ie that the control piston is in a first actuation position. If the control piston is then continuously moved away from the end of the main piston, the second recess opens in proportion to the stroke of the control piston until a second actuation position is reached. When the control piston is actuated in this way, fluid flows through the check valve and causes the working cylinder to extend slowly. When the control piston is actuated further beyond the second actuation position, the main piston is released from the Seat edge and moves substantially synchronously with the control piston, whereby a larger fluid flow can be controlled proportionally via the check valve.

The working cylinder is extended at maximum speed as follows: the control piston is not moved and the check valve works as a simple check valve; or alternatively, the control piston is moved to a maximum, the first recess in the main piston being open and the main piston following the control piston.

It is advantageous if the first recess can be closed by a tappet in the control piston, the first recess is provided in the base of the main piston, the second recess is provided radially and the first control edge is designed as a peripheral edge of a radial shoulder of the control piston. This arrangement forms the preferred exemplary embodiment of the invention and, when the first recess is closed by the tappet, ensures that the check valve works as a simple check valve.

In a further embodiment, a second control edge is provided on the control piston in the axial direction of the shut-off valve opposite to the first control edge mentioned above. By moving this second control edge, which is preferably part of a radial pilot bore, the proportional retraction of a working cylinder can be carried out. Thus, by using the shutoff valve according to the invention, both a proportional extension and a proportional insertion of a working cylinder is possible.

It is particularly advantageous if there is between the first control edge and the second control edge on the main - β - piston is a control collar, through which the second recess in the main piston can be closed. This control collar improves the behavior of the check valve when it is controlled to extend the working cylinder. In particular, the extension of the working cylinder is carried out more uniformly.

At one end of the tappet according to the first exemplary embodiment, a pilot control cone can be provided, through which the first recess in the base of the main piston can be effectively closed.

According to a second and third exemplary embodiment, an extension with the first cone section, the first cylinder section and the second cone section can be provided at one end of the tappet toward the bottom surface of the main piston. The first cone section and the second cone section are designed such that they can close the first recess. This means that the opening cross sections of the first recess and the second recess are adequately defined even when the working cylinder is slowly extended.

If the second cone section in the second and third exemplary embodiments is followed by a second cylinder section which has a smaller diameter than the second recess, the behavior of the check valve when the working cylinder is rapidly extended when the solenoid coil is fully energized is similar to the behavior when the working cylinder is rapidly extended can be designed without energizing the solenoid. Furthermore, the diameter relation between the second cylinder section and the first recess enables the extension to be inserted into the first recess without problems when the check valve is assembled. - 3-

It is advantageous if the second cylinder section has a chamfered section which allows the extension of the plunger to be securely inserted into the first recess.

In the third exemplary embodiment, no control piston is used, as a result of which a movable component has to be provided less and nevertheless essentially the same function as in the second exemplary embodiment is carried out. In the third exemplary embodiment, the second nozzle device is a fixed nozzle in the same way as in the fourth and fifth exemplary embodiments.

A shut-off valve with the extension described above is operated in accordance with the second exemplary embodiment for the proportional extension of the working cylinder as follows: from a rest position of the control piston in which the first recess is closed, the second recess in the main piston is made by the control collar of the control piston closed and the first recess opened, ie that the control piston is in a first actuating position. If the control piston is then continuously moved away from the base of the main piston, the second recess opens in proportion to the stroke of the control piston and closes the first recess in proportion to the stroke of the control piston until a second actuation position is reached. When the control piston is actuated in this way, fluid flows through the check valve and causes the working cylinder to extend slowly. When the control piston is actuated further beyond the second actuation position, the main piston releases from the seat edge and moves essentially synchronously with the control piston, as a result of which a larger fluid flow can be controlled proportionally via the check valve. -Λ o -

A check valve according to the fourth exemplary embodiment has an insert element connected to the main piston and having a third recess, which forms part of the first nozzle device, between the main piston and the tappet. This third recess and the first recess can be closed by means of an extension on the tappet, the extension in the direction of the bottom surface of the main piston toward a second cylinder section, a second cone section, a first cylinder section with a large diameter compared to that of the second cylinder section and one has first cone section. For the slow extension of a working cylinder at port B, the second cone section interacts with the third recess; the first cone section interacts with the first recess for slow retraction. For rapid extension, either the first cone section is in the first recess or the first cylinder section is in the third recess; the second cylinder section is located in the third recess for rapid retraction. The first recess can thus be designed to be more oriented towards the hydraulic requirements, with a reduction in the opening cross section of the first recess causing a reduction in the opening force of the tappet.

According to a fifth exemplary embodiment of the present invention, there can be only one tappet in the main piston, a pilot control cone for closing the first recess being formed on the end face of this tappet and a device on the outer circumference of a cylinder section together with a device on the inner bore of the tappet a third recess specifies which, together with the first recess, represents the first nozzle device. The device on the outer circumference of the cylinder section or on the - λ λ -

Inner bore of the tappet can have control edges or notch sections, which are preferably bevelled. The kerf sections are preferably formed in pairs on opposite sides of the tappet or opposite sides of the inner bore.

Consequently, according to the fourth and fifth exemplary embodiments, a check valve is possible which enables slow and rapid extension and retraction of a working cylinder at the connection and in which the first recess can only be designed in accordance with hydraulic requirements and not taking mechanical devices on the tappet into account.

A shut-off valve with the extension described above is operated in accordance with the third to fifth exemplary embodiments to slowly extend the working cylinder as follows: from an initial position of the ram in which the first nozzle device is closed, the first nozzle device is opened, ie the plunger is in a first actuation position. If the plunger is then continuously moved away from the bottom of the main piston, the first nozzle device closes in inverse proportion to the stroke of the plunger until a second actuation position is reached. When the tappet is actuated in this way, fluid flows via the pilot control channel of the check valve and causes the working cylinder to extend slowly. When the plunger is actuated further beyond the second actuation position, the main piston releases from the seat edge and moves essentially synchronously with the plunger, as a result of which a larger fluid flow can be controlled via the shut-off valve.

The plunger is preferably moved by energizing a coil winding. This can then in the first and second embodiment move the control piston. The movement of the plunger can be controlled with a high degree of accuracy by a corresponding selection of the control current. Furthermore, compared to the hydraulic control of the control piston and the plunger, the material expenditure is lower.

A stop for the main piston is preferably provided on the housing of the check valve. This prevents an unpredictable movement of the main piston and increases operational safety.

According to the first and second exemplary embodiment, a spring plate is provided on the pole housing of the coil winding, with which pretensioning springs for the control piston and for the main piston are in contact. These biasing springs ensure in the depressurized state and in the case in which the coil winding is not energized, that the main piston is biased against a seat edge of the check valve and the control piston is biased against a retaining ring on the tappet, that is to say that these are in predetermined starting positions are located, from which a controlled movement is possible. The operative connection between the tappet and the control piston enables the control piston and the tappet to be controlled together.

According to the third to fifth exemplary embodiment, a spring plate is provided on the pole housing of the coil winding, with which the biasing spring for the main piston is in contact. In the depressurized state and in the case in which the coil winding is not energized, this prestressing spring ensures that the main piston is prestressed against a seat edge of the check valve. This contributes to operational security. - 43-

The shut-off valve according to the invention is preferably used in the lifting mechanism of a tractor, the advantages of a shut-off valve becoming particularly clear in this application, but at the same time a proportional control when retracting and extending the working cylinder can be ensured.

Developments of the present invention are the subject of the dependent claims.

The invention is described below with reference to the accompanying drawings. Show it:

1 is a pilot operated check valve according to the prior art,

2 is a sectional side view of a check valve according to a first embodiment of the present invention with the valve seat omitted;

3 shows a partial view of the check valve according to the first exemplary embodiment of the present invention, the main piston and the associated seat edge being shown in particular,

4 to 6 individual steps of actuation of the check valve according to the first embodiment of the present invention when slowly extending a working cylinder,

7 and 8 show two alternatives for the actuation of the shut-off valve according to the first exemplary embodiment of the present invention for the rapid extension of a working cylinder, Ik-

9 and 10 individual steps of the actuation of the shut-off valve according to the first exemplary embodiment of the present invention during the rapid retraction of a working cylinder,

11 shows the actuation of the shut-off valve according to the first exemplary embodiment of the present invention when a working cylinder is slowly retracted,

12 shows a control circuit in which the shut-off valve according to the invention is used to control the lifting mechanism of an agricultural tractor,

13 shows a second exemplary embodiment according to the present invention, in which the pilot control element on the tappet has been modified,

14a to 14e a check valve according to a third embodiment of the present invention, a plunger being shown in different positions,

15a to 15e a shut-off valve according to a fourth exemplary embodiment of the present invention, a plunger being shown in different positions, and

16a to 16e a shut-off valve according to a fifth exemplary embodiment of the present invention, a plunger being shown in different positions.

The following is a detailed description of the five exemplary embodiments of the present invention, - λ S - wherein elements which are not provided with a reference symbol deviating from the first exemplary embodiment in the second to fifth exemplary embodiment and whose function can be found in the description of the first exemplary embodiment.

First exemplary embodiment

2 and 3 show a sectional side view or a sectional partial view of a proportionally adjustable pilot operated check valve 105 according to a first embodiment of the present invention.

The check valve 105 is designed as a cartridge-type built-in valve and, according to FIG. 3, has a cartridge housing 160 and a pole tube 147 which are detachably connected to one another via threaded sections.

In the cartridge housing 160, a pressure chamber 165, which is connected to a connection A of the check valve, and an annular pressure chamber or annulus 126, which is connected to a connection B of the check valve, are formed axially one behind the other. The diameter of the pressure space 165 is equal to the inner diameter of the annular space 126, a shoulder 161 being defined between them. A radial bore star 163 is located in the cartridge housing 160 near the shoulder 161.

The radial bore star 163 establishes a fluid connection between the annular space 126 and an annular space which is located radially outside of the radial bore star 163 and is formed around the latter. This annular space can be connected to a pressure chamber of a working cylinder and is sealed by means of sealing rings, of which the sealing ring 164 is shown. The pressure chamber 165 in λ (o -

Cartridge housing can optionally be connected to a pump or a tank in order to be able to control the extension and retraction of the working cylinder via the check valve 105.

The section of the cartridge housing 160 in which the pressure chamber 165 is formed can be provided with a thread on its outer circumference in order to screw the cartridge housing 160 into a screw-in section in a receiving bore. This receiving bore can be provided in a valve block for a large number of further valves.

An axially displaceable main piston 120, which has a main cone 121 with a cone surface 124, is located within the cartridge housing 160. In the closed position shown, the conical surface 124 is in contact with a seat edge 162, which is formed on the radially innermost section of the shoulder 161 in the cartridge housing 160. A first nozzle 122 is formed in the center of the bottom of the main piston 120 and can produce a fluid connection between the pressure chamber 165 and an inner bore 127 in the main piston 120. The main piston 120 is provided with a radial shoulder at an axial distance from the conical surface 124, so that an annular surface 125 is formed. The radial shoulder forms a difference in area between the area at the valve seat and the cross-sectional area of the main piston 120, which is delimited by the outer circumference, via which the lifting of the main piston 120 is supported. In the cylindrical section of the main cone 121, ie between the first nozzle 122 and the annular surface 125, a second nozzle 123 is provided, via which fluid connection can be established between the inner bore 127 in the main piston 120 and the annular space 126. In the inner bore 127 of the main piston 120 there is a control piston 130 which is axially displaceable relative to the main piston 120. The control piston 130 has a hollow cylinder-like section 137 adjacent to the first nozzle 122, which ends at a shoulder 128 facing a bottom surface of the inner bore 127 and delimits a space 135. A section with an axial bore 136 adjoins the hollow cylindrical section of the control piston 130.

A plurality of pilot bores 131 extending in the radial direction are formed in the jacket of the hollow cylinder-like section 137, which can be connected to the first nozzle 122 via the space 135 and open out into an annular groove 129 of the control piston 130. The annular groove 129 is delimited by a second control edge 133, which is closer to the open end of the control piston 130 compared to the position of the central axis of the pilot bore 131. By axially displacing the control piston 130, the open cross section of the second nozzle 123 can be reduced in order to restrict the fluid flow through this nozzle 123. The lower end portion of the control piston 130 in FIG. 2 is stepped back radially, so that a first control edge 134 is formed, via which the second nozzle 123 can be opened and closed when the control piston 130 is axially displaced. Between the first control edge 134 and the second control edge 133 there is a control collar 132 which has dimensions such that it can completely close the second nozzle 123. Since in this position of the control piston 130 the first nozzle 122 is opened at the same time, the pressure in the space 135 is the same as in the pressure space 165.

In the axial bore 136 of the control piston 130, a plunger 140 is provided axially in the center, on one of which

There is a pilot cone 141 at the end, the outer diameter is designed so that it can close the first nozzle 122. The tappet 140 is coupled to the control piston 130 via a retaining ring 143 which is not completely closed, so that when the tappet 140 moves away from the first nozzle, this movement is transmitted to the control piston 130. The diameter of the axial bore is continuously larger than the diameter of the tappet 140. Because of this design and because the retaining ring 143 is not completely closed, there is an open connection between the space 135 and the rear of the main piston 120 Outside diameter of the annular surface 125 determined area by the pressure in the rear control recess 138 in the closing direction, wherein all cavities in which the control pressure prevailing between the two nozzles 122 and 123 can be considered as the rear control chamber.

The other end of the plunger 140 is connected via a retaining ring 142, which is also not closed, to a magnet armature 146 which is located in the pole tube 147. The magnet armature 146 is moved by energizing a coil winding 144 provided outside the pole tube 147. There is also control pressure in the entire anchor space.

If the magnetic armature 146 moves upward in FIG. 2, it causes the plunger 140 to be taken along due to the coupling via the holding ring 142.

The main piston 120 is biased into the starting position shown in FIG. 2 via a weak biasing spring 152 and the control piston 130 is biased via a biasing spring 153. The two biasing springs 152, 153 are supported with their upper end sections shown in FIG. 2 on a spring plate 151, which in turn is also supported a radial shoulder of the pole tube 147 is in contact. Thus, the main piston 120 is biased by the biasing spring 152 against the seat edge 162 and the control piston 130 by the biasing spring 153 toward the bottom surface of the inner bore 127 in the main piston 120. The plunger 140 and the magnet armature 146 are also prestressed downward by the prestressing spring 153 in FIG. 2, the cone 141 of the plunger 140 being seated on a seat edge on the nozzle 122 in the absence of other forces. There is then a distance between the control piston 130 and the bottom surface of the inner bore 127.

The coil winding 144 is surrounded by a housing 145, which largely prevents the coil winding 144 from being influenced from the outside. A device for electrically connecting the coil winding 144 is formed at the upper end of the pole tube 147.

The main piston 120 is biased against the pole tube 147 by the biasing spring 152 against the seat edge 162. A movement of the main piston 120 away from the shoulder 161 can only be caused by an imbalance of forces, which is caused by the pressure on the surface of a main cone 121 of the main piston 120, which faces the pressure chamber 165, and the pressure in the annular chamber 126, on the one hand, and by the pressure in the rear control chamber 138 and is caused by the biasing spring 152.

The control piston 130 is biased by the spring 153. Movement of the pressure-balanced control piston 130 away from the first nozzle 122 is caused by energizing the coil winding 144 of the proportional magnet.

In the subsequent functional description of the check valve according to the first embodiment there is a working cylinder through the second port B in fluid communication with the radial bore star 163 and is connected to the pressure chamber 165 through the first port A a pump when extending the working cylinder and a tank when retracting the working cylinder.

First, a slow extension of the working cylinder controlled by the check valve 105 will be described with reference to FIGS. 4 to 6.

At the beginning of the extension, the shut-off valve is in the idle state shown in FIG. 3, i.e. that the cone surface 124 is on the seat edge 162 and that when the coil winding 144 is not energized, the pilot cone 141 of the plunger 140 closes the first nozzle 122. As a result, the pilot bores 131 are connected to the second nozzle 123, as a result of which there is a fluid connection between the rear control space 138 and the annular space 126 and load pressure is present in the rear control space as well as in the annular space 126.

The coil winding 144 is now energized in such a way that the control collar 132 on the control piston 130 closes the second nozzle 123 and the first nozzle 122 is opened by lifting off the pilot cone 141 of the plunger 140, as shown in FIG. 4. If the pressure chamber 165 is now connected to a pump via the connection A and, for example, a directional control valve, the pressure in the control chamber 138 becomes equal to the pump pressure prevailing in the pressure chamber 165 due to the closed nozzle 123 Δp is above the load pressure. The main piston 120 remains closed because the sum of the forces caused by the pump pressure on the surface enclosed by the seat edge 162 and by the load pressure on the ring surface lying between the seat edge 162 and the outer diameter of the main piston. before being generated in the opening direction, is smaller than the force which is generated by the pump pressure prevailing in the rear control chamber 138 on an active surface determined by the outer diameter.

If, as shown in FIG. 5, the coil winding 144 is energized more intensely, the control piston 130 moves away from the first nozzle 122 and the first control edge 134 opens a cross section at the second nozzle 123. Oil now begins over the Feed forward flow. The pressure in the control chamber 138 drops to a value between the pump pressure and the load pressure. This value is still so high that the main piston remains closed.

When the coil winding 144 is energized even more, the pressure in the control chamber 138 drops further, the oil flow increasing via the pilot control. Finally, the second nozzle 123 is so wide open that the forces which are generated by the load pressure and the pump pressure on the one hand and by the pressure in the control chamber 138 and the weak biasing spring 153 are on the other. Apart from the slight influence of the biasing spring 153, the movement of the control piston 130 follows from there on the main piston 120, as shown in FIG. 6, wherein - assuming load-sensing control - the level of the pressure in the control chamber 138 remains the same with regard to the load pressure and the pump pressure. A flow cross-section opens continuously between the conical surface 124 of the main piston 120 and the seat edge 162 of the cartridge housing 160.

With this shut-off valve, it is thus possible, depending on the energization of the coil winding 144, to proportionally control the volume flow between the pressure space 165 and the annular space 126 as desired. So is a Slow extension of the working cylinder possible with the desired behavior.

Secondly, a rapid extension of the working cylinder controlled by the check valve 105 is described in the form of two variants with reference to FIGS. 7 and 8.

a) First variant (Fig. 7) In this operating mode, the proportionally adjustable pilot operated check valve is used as a simple check valve, as shown in Fig. 7. This means that the pilot cone 141 keeps the first nozzle 122 closed and the pump pressure at port A lifts the main piston 120 against a load pressure acting on a non-pressure-equalized surface of the same size and against the biasing springs 152 and 153 from the seat edge 162.

b) second variant (FIG. 8)

In this operating mode, the coil winding 144 is fully energized based on the control for slowly extending the working cylinder. As a result, the first nozzle 122 is opened completely; the first control edge 134 opens the second nozzle 123 so that a maximum pilot oil flow flows. The control pressure on the rear of the main piston thus approaches the load pressure, which the control pressure cannot fall below. When the second nozzle 123 is fully open, its opening cross-section is much larger than that of the nozzle 122. The very different pressure drops at the nozzles 122 and 123 now cause the main piston 120 to open. The main piston 120 thus lifts off the seat edge 162 and opens fully, allowing a large volume flow from port A to port B and the working cylinder extends at maximum speed.

Third, rapid retraction of the working cylinder controlled by the check valve 105 will be described with reference to FIGS. 9 and 10.

A current is supplied to the coil winding 144 such that the plunger 140 lifts off and the first nozzle 122 opens, as shown in FIG. 9. At the same time, the axial cross-section of the control piston with the second control edge 133 reduces the flow cross section of the second nozzle 123, which results in a reduction in the pressure in the control chamber 138. The pressure at port B is applied to the annular surface 125 of the main piston 120. By opening the first nozzle 122, the pressure in the control chamber 138 is reduced towards the port A, so that the main piston 120 can be lifted off its seat edge 162 by the pressure acting on the annular surface 125, as shown in FIG. 10. The fluid then flows back quickly from the working cylinder to the tank, which is connected to the pressure chamber 165 - the working cylinder retracts.

Fourth, slow retraction of the working cylinder controlled by the check valve 105 will be explained with reference to FIG. 11.

In this operating mode, the coil winding 144 is supplied with less current than during rapid retraction. As a result, the plunger 140 opens the first nozzle 122 only slightly. The second nozzle 123 has a large flow cross section due to the small axial displacement of the control piston 130. Therefore, the pressure in control chamber 138 drops only slightly below the load pressure at port B, so that the main piston remains closed. Via the nozzles 122 and 123 flows only a small volume flow from the consumer to the tank connected to the pressure chamber 165. The stroke of the plunger 140 can be regulated via the energization of the coil winding 144, as a result of which a proportional speed control is made possible when retracting.

In the aforementioned valve structure in accordance with the first exemplary embodiment, when a working cylinder which is located at port B is extended, the opening cross section of the nozzle 123 must be substantially larger than the opening cross section of the nozzle 122 when the opening is fully open. To illustrate this, the equilibrium of forces is subsequently established on the main piston 120 for extending the working cylinder, the spring force of the relatively weak spring 152 and the overlap area of the plunger 141 and the nozzle 122 being disregarded.

In the rear control chamber, the control pressure P _S f acts on a surface A2, which is calculated with the main piston radius r2. The pump pressure P _p acts on the surface A] _, which is delimited by the seat edge 162 and which has the radius r ^. The load pressure P _L acts on the ring surface 125 with the surface area A2-A _] _.

The balance of forces at the main piston 120 is therefore:

A _X • P _p + (A ₂ - AT - P _L = P _st • A ₂

If it is now assumed that the ring area (A ₂ - A _] _) is significantly larger than the area A ^, for example r ^ / r ₂ - 1/2 behave, the balance of forces is changed to the control pressure P _st :

'st = PL + (Pp- ^P L) The control pressure is thus closer to the load pressure. However, since the same amount of fluid flows through the nozzles 122 and 123, the opening cross section of the nozzle 123 must be substantially larger than that of the nozzle 122. In the exemplary embodiment mentioned above, this can be implemented in that the opening cross section of the nozzle 122 is made small. However, this increases the risk of constipation.

The necessary difference between the opening cross-sections of the nozzles 122 and 123 can be achieved with a significantly lower tendency to clog by providing the plunger 140 with an extension 241, as shown in the second exemplary embodiment, which is shown in FIG. 13.

Second embodiment

In the arrangement according to the second exemplary embodiment shown in FIG. 13, the base area of a first cone section 242 is located on the cylinder section of the tappet 240. The tip of the first cone section 242 merges into a first cylinder section 244 and then into a second cylinder section 243, the tip of which also coincides is connected to the first cylinder section 244. On the base surface of the second cone section 243 there is a second cylinder section 245, which is followed by a chamfered section 246. This chamfered section 246 serves to be able to insert the extension 241 through the first nozzle 122 when the valve is assembled. For this purpose, the diameter of the cylinder section 245 and the diameter of the base of the second cone section 243 must be smaller than the inside diameter of the first nozzle 122. - IQ, -

With this extension 241, the fluid flow through the nozzle 241 changes in comparison with the previous exemplary embodiment during slow and fast extension. The different relative cross sections of the second nozzle 123 are assigned the following relative positions of the extension 241 in the first nozzle 122:

If the second nozzle 123 is not yet completely closed by the second control edge 133, then the first cone section 242 is located in the first nozzle 122 and throttles the fluid flow. The gradual opening of the first nozzle 122 is accompanied by a gradual closing of the second nozzle 123.

When the control collar 134 is in front of the second nozzle 123, the first cylinder section 244 is in the first nozzle 122 and allows maximum fluid flow.

If the opening cross section of the second nozzle 123 is reduced via the first control edge 134, the second cone section 243 is located in the first nozzle 122 and throttles the fluid flow. The gradual opening of the second nozzle 123 is accompanied by a gradual closing of the first nozzle 122.

The difference in the opening cross sections of the nozzles 122 and 123 is thus without both when the working cylinder is retracted and when the working cylinder is extended

Get trouble. The main piston 120 can therefore be safely controlled in both cases.

8 using extension 241 according to FIG. 13 with similar opening cross sections of nozzles 122 and 123 as that -2 - rapid extension according to Fig. 7 instead. In contrast to the case in which a pilot control cone 141 was present on the tappet 140, now when the nozzle 122 is closed by the second cylinder section 245, the control pressure on the rear side of the main piston 120 becomes equal to the load pressure, ie lower than in the case of the Existing pilot cone 141. The main piston opens earlier and the functional reliability of the valve can be increased.

Functional considerations for the first and second design examples1

With the first and the second exemplary embodiment, there are check valves in which a pilot element in the main piston 120 consists of a plunger 140 or 240 and a control piston 130, in which the opening cross section of a first nozzle device via the relative position of the plunger 140 or 240 with respect to the first Nozzle 122 is adjustable and in which the opening cross section of a second nozzle device can be set via the relative position of the control piston 130 with respect to the second nozzle 123.

With proportional lifting, an initial position of the pilot control element is provided at the beginning, in which the first nozzle device is closed and the second nozzle device is open. By lifting the pilot control element into a first actuation position, the first nozzle device is opened and the second nozzle device is closed, the main piston 120 being located on the seat edge 162.

If a further stroke of the pilot control element then moves it towards a second actuation position, from which the main piston of the stroke movement - 2 g - follows the pilot control element, the opening cross section of the second nozzle device increases with respect to the opening cross section of the first nozzle device.

In the first exemplary embodiment, the opening cross section of the second nozzle device is only enlarged, while the opening cross section of the first nozzle device remains constant. In the second exemplary embodiment, the opening cross section changes relative to one another more rapidly, the opening cross section of the second nozzle device being enlarged and that of the first nozzle device being reduced at the same time.

Common functional analysis of the first to fifth exemplary embodiments

As a generalized functional principle, it can be derived from the first and second exemplary embodiments that during proportional lifting in the first actuation position of the pilot control element, such pressure must be present in the rear control chamber 135 that the main piston 120 is in contact with the seat edge 162. With the first and second surfaces on the main piston of the same size, this can be implemented by a smaller opening cross section of the second nozzle device in relation to that of the first nozzle device. For the movement of the pilot control element into the second actuation position, the pressure in the control chamber 135 must decrease, which can be implemented by increasing the opening cross section of the second nozzle device in relation to that of the first nozzle device.

Special functional analysis of the third to fifth exemplary embodiments - 2. 3

Since the changes in the opening cross section and thus the hydraulic resistance of the first and second nozzle devices for setting the first actuation position and for transitioning to the second actuation position are relative changes in the opening cross sections of the first and second nozzle devices, it is not necessary to change the opening cross section of the two Change nozzle facilities. A nozzle device can thus be a fixed nozzle.

Since the magnet armature 146 causes a movement in the axial direction of the pilot control element through the coil winding 144, it is advantageous in terms of better controllability to use this movement to change the opening cross section of an axial recess in the main piston and thus the first nozzle device. Consequently, the second nozzle device is preferably the fixed nozzle.

Different configurations of the first nozzle device are now examined in the third to fifth exemplary embodiments, in which there are different hydraulic properties of the check valve and structural requirements for this.

Third embodiment

The third exemplary embodiment shown in FIGS. 14a to 14e differs from the second exemplary embodiment in that no control piston is provided in the third exemplary embodiment. The pilot control element is formed solely by a plunger 240, on which an extension 341 is provided, as in the second exemplary embodiment, and on which a first cone section 342, a first cylinder section 344, a second cone section 343, is provided in the direction of the first surface 324a second Cylinder section 345 and a chamfered section 346 are located.

Thus, the third exemplary embodiment has a simpler structure than the first and second exemplary embodiments, the lack of a control piston requiring less movable element in the check valve and consequently reducing the production costs.

In this exemplary embodiment, it is preferred that the first surface 324a of the main piston 320, which points to the connection A, has approximately the same size as the second surface 125 on the main piston 320. So if the control pressure in the rear control chamber 335 is between the pressure at port A and the pressure at port B and the opening cross section of the first nozzle device is equal to the opening cross section of the second nozzle device, there is a balance between the force caused by the pressure at the first Surface 324a and the pressure on the second surface 125, and the force caused by the pressure in the control chamber 335.

To open the fluid connection via a gap between the main piston 120 and the seat edge 162 when lifting, the opening cross section of the first nozzle device must now be reduced from this state of equilibrium. To open this fluid connection when lowering, however, the opening cross section of the first nozzle device must be enlarged.

In the case of a check valve in accordance with the third exemplary embodiment, the slow extension is not proportional lifting, but instead there is a gradual reduction in the volume flow at the first nozzle device. tung instead. The speed of the hydraulic consumer only increases again when the main piston moves away from the seat edge. If a small speed range is sufficient during slow extension, a relatively small stroke of the pilot control element does not have a negative effect on the movement from the first actuation position to the position in which the main piston lifts off the seat edge.

The opening force that is to be transmitted from the coil winding 144 to the plunger 340 is determined in the lowering operating mode by the load pressure acting on the extension 341 at the first cone section 342. In order to keep this opening force as small as possible, the diameter of the first recess 122 must be made small. For reasons of stability and production with regard to the first cylinder section 344, however, a certain minimum dimension cannot be undershot. This caused problems when lowering.

These problems can be solved by interchanging the two nozzle sections on the tappet, as is shown below in the fourth and fifth exemplary embodiment.

Fourth embodiment

In the shutoff valve according to the fourth exemplary embodiment shown in FIGS. 15a to 15e, the pilot control element is designed in the form of a plunger 440 which has a cylinder section 440a molded from plastic, in the front end section of which a plunger tip 440b made of metal is cast. Two sections 440bl, 440b2 with a larger diameter on the plunger tip 440b ensure a positive, fixed connection between the cylinder section 440a and the plunger tip 440b. Furthermore, the plunger tip 440b has an extension 441 which is not covered by the cylinder section 440a. The following sections are provided in order from the cylinder section 440a on the extension 441 of the tappet tip 440b: a second cylinder section 444, the function of which corresponds to that of the first cylinder section 344 in the third exemplary embodiment, a second cone section 443, the function of which corresponds to that of the second cone section 343 in the Corresponds to the third exemplary embodiment, a first cylinder section 445, the function of which corresponds to that of the second cylinder section 345 in the third exemplary embodiment, and a first conical section 442, the function of which corresponds to that of the first conical section 342 in the third exemplary embodiment.

Between the plunger 440, which is inserted into an inner bore in the main piston 420, and the main piston 420, there is an insert element 470 which, in this order, has a direction towards the plunger tip 440b: a cylinder section 470a with a large inner diameter, a section 470c with connecting recesses, which establish fluid communication between the rear control chamber 435 and the second nozzle device 123, and a section 470b with a large inner diameter, in the center of which a third recess 471 is provided which together with the first recess 122 forms the first nozzle device. Between the inner bore of the main piston 420 and the outer circumference of the section 470b with a large inner diameter, a seal 476 is provided, which prevents fluid flow between the first recess 122 and the second nozzle device 123 via sections other than the third recess 471. Axial movement of the insert element 470 with respect to the main piston 420 is prevented by a snap ring 475, which is located on a small diameter opposite the end face on the section 470b. End portion of the insert member 470 is located in an annular recess in the inner bore of the main piston 420. In order to enable the snap ring 475 to be attached easily, an annular space 477 of small dimensions must be provided between the bottom surface of the inner bore of the main piston 420 and the end face of the section 470b with a small diameter.

In the same way as in the first to third exemplary embodiments, the pressure in the rear control chamber 435 lies both near the bottom section of the inner bore in the main piston 420, and in this case also on the insert element 470, and also on the end face of the main piston opposite to the first surface 424a 420 so that the pressure in the rear control chamber 435 acts on a surface on the main piston 420, the surface area of which is the sum of the first surface on which the pressure is present at port A and the second surface on which the pressure is present at port B on Main piston 420 corresponds.

As in the third exemplary embodiment, the surface area of the first surface 424a is also approximately equal to the surface area of the second surface 425, as in the case of the shutoff valve in accordance with the fourth exemplary embodiment, so that an equilibrium state results with the same opening cross section of the first and second nozzle devices.

The various positions of the plunger tip 440b with respect to the main piston 420 with the insert element 470 are described below.

In the position shown in FIG. 15a, the first cone section 442 is located in the first recess 122 and thus blocks the fluid connection via the first - 3H -

and second nozzle means through the main piston 420.

In the position shown in FIG. 15b, a control of the first nozzle device proportional to the stroke of the plunger 440 is made possible, in which the first recess 122 is opened via the first cone section 442 and the opening cross section of the third recess 471 remains constant. The space between the end face of the cylinder section 440a of the tappet 440 and the insert element 470 is designed such that no additional throttling of the fluid flow occurs.

With the position shown in FIG. 15c, the maximum possible opening cross section of the first nozzle device is reached, since the second cylinder section 444 is still in the third recess 471 and there is a large opening cross section between the first recess 122 and the first cone section 442.

In the position shown in FIG. 15d, the second cone section 443 is in the third recess 471. The first recess 122 is even more open than in the position in FIG. 15c. Overall, however, a stronger throttling effect occurs in the first nozzle device due to the smaller opening cross section of the third recess 471 compared to the position in FIG. 15c than in the position in FIG. 15c.

In the position shown in FIG. 15e, the third recess is closed by the first cylinder section 445, but an annular gap of small dimensions is present around the cylinder section 445 in order to allow the plunger 440 to slide. In the position corresponding to FIG. 15e, there is therefore an almost completely closed first nozzle device. It is advantageous in the fourth embodiment that the cross section of the first recess 122 does not depend on the dimensions of the plunger tip 440b. The seat diameter can be chosen to be much smaller than in the third exemplary embodiment in coordination with the second nozzle device, which as a further exemplary embodiment can also be variable in the opening cross section. The magnetic device for actuating the tappet therefore does not have to be dimensioned larger for high load pressures.

Furthermore, the prevention of constrictions in the opening cross section due to dirt particles can be taken into account when selecting the cross sections of the nozzle devices.

The disadvantage here, however, is the need to provide the insert element 470 and the recess for the snap ring 475 in the inner bore of the main piston 420. This not only results in higher production costs, but also ensures the functional reliability of a further component in the main piston 420.

This disadvantage can be eliminated by a check valve according to the fifth embodiment of the present invention.

Fifth embodiment

The shutoff valve shown in FIGS. 16a to 16e according to the fifth exemplary embodiment, just like the third exemplary embodiment, has only one component, namely a tappet 540, in the main piston 520. The plunger 540 has, in order to the first surface 524a on the main piston 520, a shaft portion 548 with an outer diameter that is smaller than the inner diameter of the inner bore of the main piston 520, a cylinder portion 543, the outer diameter of which is also smaller than the inner diameter of the inner bore of the main piston 520 and on the circumference of which a throttling device is provided, a cone section 542 and a pilot cone 541, by means of which the first recess 122 can be closed. The shaft section 548 and the cylinder section 543 can also be formed with the same diameter. The throttling device consists of notch sections 543a, 543b, 543c and 543d, which are each provided in pairs (543a, 543b; 543c, 543d) on opposite circumferential sections of the cylinder section 543 and which, as can be seen in FIG. 16a from the illustration of the notch section 543c , Have a recess 543c2 with a cylindrical cross section and then a recess 543cl with a conical cross section.

The main piston 520 has a cylindrical inner recess 521 at the bottom portion of the inner bore, the inner diameter of which is larger than that of the inner bore, so that an annular control edge 524 is present between the inner bore of the main piston and the cylindrical inner recess 521.

The control edge 524 is preferably beveled and forms the third recess together with the notch sections 543a, 543b, 543c, 543d. The first nozzle device thus consists of the recess 122, which can be closed by the pilot cone 541, and the recesses, which define the control edge 524 and the kerf sections. The second nozzle device is, as in the third The third and fourth exemplary embodiments are formed by a fixed nozzle 123.

As an alternative to this, the third recess can also be formed by a cylinder section 543 without notch sections and opposing depressions on the inner bore of the main piston 520, the depressions, however, in analogy to the cross-sectional area of the notch sections, in the reverse order to the first surface 524a of the main piston, and a cylindrical cross section away from this surface 524a have a conical cross section.

When designing the notch sections and the control edge, it is important that with a predetermined stroke (e.g. 1 mm) of the ram a predetermined change in area (e.g.

0, 7mm.2) can be realized with the opening cross section of the third recess.

In this exemplary embodiment too, the area of the first area 524a on the main piston is preferably approximately equal to the area of the second area on the latter.

The various positions of the ram are explained below.

In the position shown in FIG. 16 a, the first recess is closed by the pilot cone 541 and the third recess is open.

In the position shown in FIG. 16b, a proportional opening of the first recess 122 is possible, while the third recess still allows a maximum fluid flow. In the position shown in FIG. 16c, the first nozzle device is open to a maximum, the first and the second recess having a large opening cross section.

In FIG. 16d the opening cross section of the third recess is reduced, while in FIG. 16e the third recess is completely closed except for the annular gap around the cylinder section 543.

In the fifth embodiment, it is advantageous that only the inner recess 521 has to be provided in the main piston 520 and no other components apart from the tappet 541 need to be inserted into the main piston 520. The opening cross section of the third recess can be influenced via the design of the ker portions, which can be provided on the outer circumference of the plunger 540 in a simple manner.

The fifth exemplary embodiment thus results in a cost-effective implementation of the principle of the present invention, the function in the individual positions being easily predictable.

Detailed functional analysis of the third to fifth exemplary embodiments

Thus, in the third to fifth exemplary embodiment, when slowly lifting from the initial position shown in FIGS. 14a, 15a, 16a, in which the first nozzle device is closed, the first actuating position shown in FIGS. 14c, 15c, 16c is assumed which is the maximum opening cross section of the first nozzle device. The pressure in the rear control chamber is reduced via the reduction in the opening cross section of the first nozzle device shown in FIGS. 14d, 15d, 16d. -> 3 - lowers until the main piston, in extreme cases at a position of the pilot element as shown in FIGS. 14e, 15e, 16e, moves synchronously with the stroke of the pilot element, as a result of which a fluid flow between the connection A and the connection B via a Gap between the main piston and the seat edge is made possible.

To quickly lift the load, either the position shown in FIGS. 14a, 15a, 16a or the position of the pilot element shown in FIGS. 14e, 15e, 16e in the main piston is assumed, the first nozzle device being closed. As a result, the check valve according to the invention acts like a check valve without a proportional function. Because of the sealing seat in FIGS. 14 a, 15 a, 16 a, seating of the first conical section 342 on the first nozzle 122 is preferred.

To quickly lower the load, the first nozzle device is opened to the maximum, as shown in FIGS. 14c, 15c, 16c. As a result, the volume flow through the second and the first nozzle device assumes a maximum value, which results in a rapid lifting of the main piston from the seat edge 162.

For slowly lowering the load, the pilot element is moved from the position shown in FIGS. 14a, 15a, 16a, in which the first nozzle device is closed, to the position shown in FIGS. 14b, 15b, 16b, in which a proportional increase in the Opening cross-section of the first nozzle device takes place, actuated towards the position shown in FIGS. 14c, 15c, 16c. As a result, the timing of the main piston lifting off the seat edge 162 can be accurately determined. - HO -

The invention thus provides a shut-off valve which effectively enables a connected working cylinder to retract and extend slowly, the retraction or extension speed being adjustable manually or electronically. At the same time, the check valve performs the function of a simple check valve even when there is no electrical excitation. The check valve according to the invention is therefore suitable for the most effective control of a working cylinder in a wide variety of applications with low material expenditure.

The main piston 120 of the check valve according to the invention can preferably be moved against a stop on the cartridge housing both when retracting and when extending a connected working cylinder, as a result of which material deformations and uncontrolled operation of the check valve can be prevented.

With regard to the design of the drive of the tappet or the combination of tappet and control piston and other features of the pilot operated check valve, reference is made to the application filed on December 5, 1997 with the internal file number MA7237.

Fig. 12 shows the use of the check valve 105 according to the invention in a hoist control of a tractor.

In this control circuit, a constant pump 101 is located on the pressure chamber 165 of the check valve 105, to which a 3-way pressure compensator 110 is connected in parallel via a pressure connection and drain connection. The annular space 126 of the check valve is connected to a pressure space 104 of a working cylinder 103. Between the pressure chamber 104 of the working cylinder 103 and the inlet of the pressure compensator 110, a metering orifice 106 and a simple check valve 107 are provided. Furthermore, a spring-side control connection of the pressure compensator 110 is connected to the line section lying between the measuring orifice 106 and the check valve 107 and via a valve 109 to the tank 102.

When the working cylinder 103 is extended, the system is used as a load-sensing system. The pump pressure Pp is above the load pressure PL by Δp ^ i since the valve 9 is switched to the position b in which the connection between the control connection of the pressure compensator HO and the tank 102 is interrupted.

When the working cylinder 103 is retracted, the valve 109 is switched to the position a, in which there is a connection between the control connection of the pressure compensator 110 and the tank 102. As a result, the tank pressure is present at the control connection of the pressure compensator 110, as a result of which the pressure compensator 110 is activated in order to return the fluid in the working cylinder 103 and the delivery quantity of the pump to the tank 102.

When retracting and extending the working cylinder 103, the user can carry out any proportional actuation of the check valve 105, which is adapted to the desired behavior of the working cylinder 103. However, it is preferably controlled electronically in order to implement a complex interaction with other hydraulic components.

For example, when the above-mentioned control is used when lifting a plow, a setpoint is specified and actual values are read in from position sensors or force sensors. These values become necessary control signal for the check valve 105 is calculated.

It is thus possible with such a control circuit to avoid creeping movements of the working cylinder due to the absolutely leakage-free blocking of the blocking valve and, at the same time, to carry out a proportional activation both when retracting and when extending a working cylinder.

In the first and second exemplary embodiments, the invention thus relates to a pilot-operated check valve with a main piston which can be in contact with a seat edge and which has a radial recess and an axial recess, a control piston which is movable in the main piston and has a first control edge, which points in the direction of the piston end of the main piston, and a plunger arranged in the control piston, through which the control piston can be moved. A control collar and a second control edge are preferably formed adjacent to the first control edge. The pilot control of the shut-off valve takes place by exposing and covering the cross-sectional areas of the axial recess and the radial recess via the first control edge, the second control edge, the control collar or via a pilot control cone on the tappet, whereby this pilot control causes a fluid flow via the axial recess and the radial recess can be created in the main piston and / or the main piston can be brought into distance from the seat edge.

A pilot operated check valve according to the present invention accordingly has a pilot element in a main piston, via which the ratio of the hydraulic resistance of a first nozzle device in the main piston to the hydraulic resistance of a second one Nozzle device in the main piston is changeable. The first nozzle device is connected to a connection at which there is preferably a pump, and the second nozzle device is connected to a connection at which there is preferably a working cylinder of a consumer. Appropriate control of the pilot control element enables a slow and fast extension and a slow and fast extension of the working cylinder by changing the ratio of the hydraulic resistances.

Claims

Expectations

1. Pilot-operated check valve (105; 305; 405; 505), comprising: a main piston (120; 320; 420; 520), via which a connection between a first connection (A) and a second connection that can be connected to a hydraulic consumer (B) can be controlled and the pressure prevailing on a first surface (124a) from the first connection (A) and on an annular, second surface (125) the load pressure of the hydraulic consumer in the opening direction and from one in a rear control chamber (135; 335 ; 435; 535) prevailing control pressure can be applied in the closing direction, a pilot control element (130, 140; 130, 240; 340; 440; 540), which is coaxially movable with respect to the main piston (120; 320; 420; 520), one in the main piston (120; 320; 420; 520) provided first nozzle device (122; 122, 471; 122, 524, 543), via which the rear control chamber (135; 335; 435; 535) can be connected to the first connection (A) is provided in the main piston (120; 320; 420; 520) ne second nozzle device (123) via which the rear control chamber (135; 335; 435; 535) can be connected to the second connection (B), characterized in that, starting from an initial position of the pilot control element (130, 140; 130, 240; 340; 440; 540), in which the first nozzle device is closed and the second nozzle device is open , for a pressure medium flow from the first port (A) to the second port (B), the first nozzle device is opened by an initial stroke of the pilot element (130, 140; 130, 240; 340; 440; 540) into a first actuating position, such a ratio the hydraulic resistance of the first nozzle device (122; 122, 471; 122, 524, 543) to the hydraulic resistance of the second nozzle -1 + 5 ^" - device (123) is set so that the resulting control pressure keeps the main spool (120; 320; 420; 520) closed, and that when the pilot element (130, 140; 130, 240; 340; 340; 440; 540), the ratio of the hydraulic resistance of the first nozzle device to the hydraulic resistance of the second nozzle device increases beyond the first actuation position.

2. Pilot-operated check valve (105) according to claim 1, wherein the pilot control element has a control piston (130), the first nozzle device has a first recess (122) and the second nozzle device has a second recess (123), and wherein the check valve (105) has a control device (133, 134) on the control piston (130), via which an opening cross section between the rear control chamber and the second recess (123) can be continuously adjusted.

3. shut-off valve according to claim 2, wherein the control device has a first control edge (134), via which the second recess (123) can be opened continuously when the control piston (130) is activated.

4. shut-off valve according to claim 3, wherein in the starting position of the control piston (130) the first recess (122) is closed, in the first actuating position of the control piston (130) the first recess (122) is open and the second recess (123) is closed , with subsequent continuous movement of the control piston (130), the first recess (122) is open and the opening cross section of the second recess (123) increases over the first control edge (134) until a second actuation position of the control piston (130) is reached , and When the control piston (130) moves continuously from the second actuation position, the main piston (120) essentially follows the movement of the control piston (130) and moves away from a seat edge (162) of the check valve.

5. Pilot-operated check valve (105) according to claim 3, wherein the pilot element has a plunger (140) which is provided coaxially to the control piston (130), through which the first recess (122) can be closed, the first recess (122) in Main piston (120) is designed as an axial bore and the second recess (123) in the main piston (120) is designed as a radial bore, and wherein the first control edge (134) is designed as a peripheral edge of a radial shoulder of the control piston (130).

6. shut-off valve according to claim 5, wherein the control device has a second control edge (133), via which the second recess (123) is continuously controllable upon axial movement of the plunger (140) to open the first recess (122), the second control edge ( 133) is arranged axially behind the first control edge (134) in the opening direction of the tappet.

7. Check valve according to claim 6, wherein a control collar (132) is provided on the control piston (130) between the first control edge (134) and the second control edge (133), through which the second recess (123) can be completely closed.

8. shut-off valve according to claim 7, wherein the plunger (140) has a pilot cone (141), via which the first recess (122) in the main piston (120) can be closed.

9. shut-off valve according to claim 1, wherein the first nozzle device has a first recess (122), the second nozzle device is a fixed nozzle in the form of a second recess (123) and the pilot element is a plunger (340; 440; 540) through which the first recess (122) can be closed.

10. shut-off valve (305; 405; 505) according to claim 9, wherein the first recess (122) in the main piston (320; 420; 520) is designed as an axial bore and the second recess (123) in the main piston (320; 420; 520) is designed as a radial bore.

11. shut-off valve according to claim 5, 6, 7, 9 or 10, wherein the plunger (240; 340) an extension (241; 341) with a first conical section (242; 342), the base of which is connected to the cylindrical section of the plunger (240; 340), and having a second cone section (243; 343), the tip of which is connected to the tip of the first cone section (242; 342) via a first cylinder section (244; 344), the first recess (122) can be closed by the extension (241; 341).

12. A check valve according to claim 11, wherein a second cylinder section (245; 345) is formed on the base surface of the second cone section (243; 343), the diameter of which is not greater than the diameter of the first recess (122).

13. Check valve according to claim 12, wherein a chamfered section (246; 346) is formed on the second cylinder section (245; 345).

14. Check valve according to claim 3 or one of claims 11 to 13, if these depend on claim 2, wherein in the starting position of the control piston (130) the first recess (122) is closed, in the first actuating position of the control piston (130) the first recess (122) is open and the second recess (123) is closed, with subsequent continuous movement of the control piston ( 130) the opening cross section of the first recess (122) decreases and the opening cross section of the second recess (123) increases over the first control edge (134) until a second actuation position of the control piston (130) is reached, and the main piston (120) further continuous movement of the control piston (130) from the second actuation position essentially follows the movement of the control piston (130) and moves away from a seat edge (162) of the check valve.

15. The shut-off valve according to claim 9 or 10, which has an insert element (470) which is provided between the main piston (420) and the tappet (440), is arranged coaxially with respect thereto and is mechanically connected to the main piston (420) or is formed in one piece , wherein the first nozzle device has a third recess (471), which is provided centrally in the longitudinal direction of the insert element (470), the plunger (440) being an extension (441) with a first cone section (442), the base of which is the base of a is connected to the second cone section (443), the tip of which is in turn connected to a cylinder section (440a) of the tappet (440), the first recess (122) and the third recess (471) being dependent on the extension (441) can be closed from the relative position of the extension (441) with respect to the respective recess.

16. shut-off valve according to claim 15, wherein the base of the first cone section (442) is connected to the base of the second cone section (443) via a first cylinder section (445), the diameter of which is not greater than the diameter of the third recess (471), and wherein the tip of the second Tapered section (443) is connected to a cylinder section (440a) of the plunger (440) via a second cylinder section (444).

17. Check valve according to claim 9 or 10, wherein the tappet (540) has a pilot cone (541), via which the first recess (122) in the main piston (520) can be closed, wherein the first nozzle device is a first device (543) for influencing the volume flow , which is located on the outer circumference of a cylinder section (543) which is connected to the base of the pilot cone (541), and a second device (524) for influencing the volume flow, which is provided in the main piston (520) coaxially to the tappet (540), and an opening cross-section between the first recess (122) and the second recess (123) can be set via the relative position of the first device (543) for influencing the volume flow and the second device (524) for influencing the volume flow.

18. The shut-off valve according to claim 17, wherein the first device (543) for influencing the volume flow has notch sections (543a, 543b, 543c, 543d), which are provided in pairs opposite to each other on the outer circumference of the cylinder section (543) in the longitudinal direction of the tappet (540), wherein the second device (524) for influencing the volume flow has an annular control edge (524) whose radial section faces the first surface (524a) of the main piston (520). -c O -

19. The shut-off valve according to claim 17, wherein the second device for influencing the volume flow has notch sections which are arranged in pairs opposite each other on the inner circumference of a cylindrical inner recess (535) in the main piston (520) in which the tappet (540) is located, in the longitudinal direction of the Tappet (540) are provided, the first device for influencing the volume flow having an annular control edge which is located on the outer circumference of the cylinder section (543) and whose radial section points in the opposite direction with respect to the pilot cone (541) of the tappet (540).

20. Check valve according to claim 18 or 19, wherein the notch portions (543a, 543b, 543c, 543d) and / or the annular control edge (524) are chamfered.

21. shut-off valve according to one of claims 11 to 13, if they depend on claim 9 or 10, or according to one of claims 15 to 20, wherein in the starting position of the plunger (340; 440; 540) the first nozzle device is closed, in which the first actuating position of the tappet (340; 440; 540) the first nozzle device is open, with subsequent subsequent movement of the pilot element (340; 440; 540) the opening cross section of the first nozzle device is reduced until a second actuating position of the tappet (340; 440; 540 ) has been reached, and the main piston (320; 420; 520) continues to follow the movement of the tappet (340; 440; 540) from the second actuation position and continues to move as the plunger (340; 440; 540) continues to move from a seat edge (162) of the check valve.

22. Check valve according to one of claims 5 to 21, if claim 14 depends on claim 5, wherein the tappet is connected to a magnet armature (146) which is movable with respect to a pole tube (147) by energizing a coil winding (144) so that the plunger is movable with respect to the main piston (120).

23. Check valve according to claim 22, wherein at least one stop is provided on the housing of the check valve, with which the main piston (120) can be caused by movement of the armature (146) in contact.

24. Stop valve according to claim 22 or 23, wherein a biasing spring (152) for the main piston (120) is supported on a spring plate (151) attached to the pole tube (147) and the main piston (120) against the seat edge (162) of the Bias valve preloaded.

25. Blocking valve according to claim 24, if this depends on claim 5, wherein a biasing spring (153) for the

Control piston (130) is supported on the spring plate (151) and prestresses the control piston (130) against a retaining ring (143) on the tappet (140).

26. Stop valve according to one of the preceding claims, which can be used to control the lifting mechanism of a tractor.