Valve assembly with load holding, pressure compensator and copy valve

Abstract

Valve assembly (10) with a housing (20) which has a first and a second working connection (21; 22), a pump channel (23) and at least one tank channel (24), wherein a first control slide (30) is received in the housing (20) so as to be linearly movable with respect to a longitudinal axis (14), wherein the first control slide (30) has a first and a second annular groove (31; 32) which are spaced apart from one another in the direction of the longitudinal axis (14), wherein the first and the second annular groove (31; 32) together with the housing (20) each form two oppositely adjustable first main orifices (33), wherein a second control slide (50) is received in the housing (20) so as to be linearly movable and together with the housing (20) forms an adjustable second main orifice (51), wherein a first and a second check valve (71;72), characterized in that a first fluid flow path starting from the pump channel (23) via the second main orifice (51), further via a first control point (11), further via the first check valve (71), further via the first annular groove (31) to the first working connection (21), wherein a second fluid flow path leads from the pump channel (23) via the second main orifice (51), further via the first control point (11), further via the second check valve (72), further via the second annular groove (32) to the second working connection (22), wherein the first and the second check valve (71; 72) each exclusively direct a fluid flow to the respectively assigned first or second working connection (21;22), wherein a third fluid flow path leads from the first working connection (21) via the first annular groove (31) to an associated tank channel (24), wherein a fourth fluid flow path leads from the second working connection (22) via the second annular groove (32) to an associated tank channel (24), wherein a third control slide (60) is accommodated in the housing (20) in a linearly movable manner, which together with the housing (20) forms an adjustable third main aperture (61), wherein the housing (20) delimits a second control point (12) in sections, which is also delimited by the first control slide (30), wherein in the interior of the first control slide (30) there are first and second control channels (35;36) are provided, wherein the first control channel (35) is designed such that it establishes a fluid connection from the first working connection (21) to the second control point (12) only when the first fluid flow path is open, wherein the second control channel (36) is designed such that it establishes a connection from the second working connection (22) to the second control point (12) only when the second fluid flow path is open, wherein the pressure at the second control point (12) acts on the third control slide (60) in the opening direction of the third main orifice (61);

Description

[0001] The invention relates to a valve assembly according to the preamble of claim 1.

[0002] From US 5 305 789 A, a valve assembly is known which has a first and a second control disc. A first and a second check valve ensure load holding. The second control spool is designed such that it regulates the pressure downstream of a main control orifice to a maximum load pressure or LS pressure. It is therefore referred to as a downstream pressure compensator. The first control spool has a first and a second annular groove, each forming two first orifices that can be adjusted in opposite directions. The direction of movement of the actuator connected to the first and second working ports is adjusted by means of the first and second annular grooves. The main control orifice, with which the movement speed of the actuator is adjusted, is formed by further annular grooves on the first control spool.

[0003] From DE 198 02 430 A1 a valve assembly is known in which the first main orifices are arranged on two separately formed first control slides so that they can be adjusted independently of each other.

[0004] An advantage of the present invention is that the main spool only needs to be provided with the first and second annular grooves and the control orifices located there, eliminating the need for the aforementioned separate main control orifice. Accordingly, it is easy to manufacture, and the valve assembly requires little installation space. Nevertheless, the valve assembly according to the invention has essentially the same functionality as the known valve assembly. Furthermore, the valve assembly according to the invention is particularly well-suited for moving very large masses that have a correspondingly high inertia. For example, the slewing gear of a hydraulic excavator, via which the heavy superstructure is moved, is considered. With the known valve assembly, accelerating the mass from a standstill would result in very high pressures and a correspondingly jerky movement.In contrast, the valve assembly according to the invention enables smooth and vibration-free start-up. Furthermore, the valve assembly according to the invention can be easily combined with the known valve assembly in a valve block, with all valve assemblies being able to control actuators in parallel.

[0005] According to the independent claim, it is proposed that a first fluid flow path leads from the pump channel via the second main orifice, further via a first control point, further via the first check valve, further via the first annular groove to the first working connection, wherein a second fluid flow path leads from the pump channel via the second main orifice, further via the first control point, further via the second check valve, further via the second annular groove to the second working connection, wherein the first and the second check valve each only allow a fluid flow to the respectively associated first and second working connection, wherein a third fluid flow path leads from the first working connection via the first annular groove to an associated tank channel, wherein a fourth fluid flow path leads from the second working connection via the second annular groove to an associated tank channel.The elements known per se are therefore connected differently, whereby in addition to the first main orifices on the first and second annular grooves, no further continuously adjustable orifices are provided which are located in the flow path from the pump channel to the first and / or second working connection.

[0006] The first and second fluid flow paths preferably coincide between the pump channel and the first control point. The first and / or second main orifice are preferably continuously adjustable. The first and third fluid flow paths preferably lead via different first main orifices on the first annular groove. The second and fourth fluid flow paths preferably lead via different first main orifices on the second annular groove. The housing preferably comprises a one-piece base body, which is most preferably manufactured using a casting process. Other parts, which are also part of the housing, can be permanently installed in the base body. For example, the third main orifice mentioned below is delimited by a separate sleeve, which is permanently installed in the base body.

[0007] The second control disc is preferably designed and connected to the remaining valve assembly in such a way that the pressure drop at the respectively active first main orifice in the first or second fluid flow path is regulated to a predetermined value.

[0008] The valve assembly is preferably designed in the manner of a valve disc, so that several separate valve assemblies can be attached to one another to form a valve block. The pump channel, the at least one tank channel, and the load signaling channel discussed below preferably each form a channel that extends through the entire valve block.

[0009] The first control slide can be acted upon by at least one first spring, preferably in such a way that it is pre-tensioned into a central position in which most preferably all the first main orifices are closed.

[0010] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0011] According to the invention, a third control slide is accommodated in the housing in a linearly movable manner, which third control slide together with the housing forms an adjustable third main orifice, wherein the housing delimits a second control point in sections, which is also delimited by the first control slide, wherein a first and a second control channel are provided in the interior of the first control slide, wherein the first control channel is designed such that it establishes a fluid connection from the first working connection to the second control point only when the first fluid flow path is open, wherein the second control channel is designed such that it establishes a connection from the second working connection to the second control point only when the second fluid flow path is open, wherein the pressure at the second control point acts on the third control slide in the opening direction of the third main orifice.This preferably provides a load signal to the second control spool. No pressure fluid can escape from the second control point, which can be connected to the two working ports, because the corresponding flow path is blocked by the third control spool. This ensures that the load holding system mentioned above operates completely leak-free.

[0012] The third control disc is preferably designed and connected to the rest of the valve assembly in such a way that it regulates the pressure on a side of the second control slide provided with a second spring to the pressure at the second control point. The second control point is preferably designed in the form of an annular groove in the housing surrounding the first control slide. The third main orifice is preferably continuously adjustable.

[0013] It can be provided that the pressure at the first control point acts on the second control disc in the closing direction of the second main orifice, with the second control disc being acted upon by a second spring in the opening direction of the second main orifice. This ensures that the movement speed of the actuator connected to the valve assembly depends solely on the setting of the first control slide, but not on the load acting on the actuator.

[0014] A fifth fluid flow path may be provided, leading from the first control point via the third main orifice, then via a third control point to a side of the second control spool loaded with a second spring. This indirectly reports the load acting on the actuator to the second control spool.

[0015] It can be provided that the pressure at the third control point acts on the third control disc in the closing direction of the third main orifice. A third spring can be assigned to the third control disc, which acts on it in the closing direction of the third main orifice. The preload force of the third spring is preferably designed to be so small that it essentially does not affect the pressure regulation, while moving the third control disc to a defined position in the depressurized state.

[0016] The housing can be provided with a load-sensing channel, the pressure at the third control point being connected to the load-sensing channel via a third check valve, the third check valve only permitting fluid flow from the third control point to the load-sensing channel. If the load-sensing channels of several valve assemblies are directly connected to one another, the highest load pressure of all valve assemblies is present in the load-sensing channel. The present valve assembly can also be combined with valve assemblies designed according to US Pat. No. 5,305,789 A, the pressure in the load-sensing channel being designated "LS pressure" therein.

[0017] It can be provided that the third control point is connected to a respective associated tank channel via at least one secondary orifice, wherein the secondary orifices are connected in parallel if multiple secondary orifices are provided. The secondary orifices can be used to influence the pressure at the third control point so that the valve assembly exhibits the desired operating behavior. In particular, smooth acceleration of large masses can be achieved.

[0018] It can be provided that the at least one secondary orifice comprises a first secondary orifice which is continuously adjustable and has a smallest opening cross-section that is different from zero. Thus, pressurized fluid continuously flows from the third control point. If the pressure at the second control point drops, it is ensured that the pressure at the third control point also drops, so that the two pressures equalize. The first secondary orifice is preferably defined by a linearly movable fourth control slide. The fourth control slide is preferably biased by a fourth spring in the direction of increasing the size of the first secondary orifice.

[0019] It can be provided that the at least one secondary orifice comprises a second secondary orifice, which is a component of a pressure relief valve. This allows the pressure at the third control point and thus the pressure reported in the load signaling channel to be limited to a predetermined upper limit. The minimum flow resistance of the second secondary orifice is preferably smaller than the minimum flow resistance of the other secondary orifices, most preferably significantly smaller.

[0020] It can be provided that the position of the first control spool is adjustable by means of a first and a second control pressure. The first control spool is preferably biased by at least one first spring into a central position, in which most preferably all of the first main orifices are closed. The first and / or the second control pressure act on the first control spool, preferably in the direction of the longitudinal axis.

[0021] It can be provided that the first secondary orifice is adjustable such that its opening cross-section depends on the first and / or the second control pressure.

[0022] It can be provided that the opening cross-section of the first secondary orifice becomes smaller when the higher of the two pressures, first and second control pressure, increases.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0024] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 shows a circuit diagram of a valve assembly according to the invention; Fig. 2 a longitudinal section of the valve assembly according to Fig. 1, wherein the cutting plane passes through the first and second control slides; Fig. 2a one of the Fig. 2 corresponding representation, wherein the first and second control slides are shown in section; Fig. 3 another longitudinal section of the valve assembly according to Fig. 1, wherein the section plane passes through the third and fourth control slide; and Fig. 4 an enlarged section of Fig. 3 in the area of ​​the third control slide.

[0025] Fig. 1 shows a circuit diagram of a valve assembly 10 according to the invention. The valve assembly 10 is intended for use in a valve block, wherein it is preferably designed in the manner of a valve disc. It is penetrated by a pump channel 23, two tank channels 24 and a load-sensing channel 25, each of which is designed such that a continuous channel results across the entire valve block. Preferably, the valve block primarily comprises valve discs constructed in accordance with US 5 305 789 A, wherein only individual valve discs are designed according to the present invention. The present invention and US 5 305 789 A differ primarily in the manner in which load compensation is realized by means of the second control spool 50.

[0026] The valve assembly 10 has a first control spool 30, which adjusts the direction and speed of movement of the actuator 90, which is connected to the first and second working ports 21; 22. The actuator 90 can be a hydraulic cylinder or a hydraulic motor. The first control spool 30 is biased by two first springs 34 into a central position, in which the actuator 90 does not move. In this position, no pressurized fluid can flow from the pump channel to the actuator, which is why it is referred to as a closed-center system. The pressurized fluid is preferably a liquid, most preferably hydraulic oil.

[0027] The first control slide is moved hydraulically, namely with the first and second control pressures 37; 38, which move the first control slide 30 relative to a longitudinal axis (No. 14 in Fig. 2) in the opposite direction. The first and second control pressures are preferably supplied by an electromagnetically operated pilot valve (No. 92 in Fig. 2). They are preferably connected on the inlet side to a shuttle valve 91, at the outlet of which a third control pressure is applied, which is equal to the higher of the two pressures, the first and second control pressures 37; 38.

[0028] The aforementioned load compensation is achieved with a second control spool 50, which is arranged upstream of the first main orifices of the first control spool 30 in the flow direction. This is therefore also referred to as an upstream pressure compensator, although US 5 305 789 A uses a downstream pressure compensator that operates hydraulically significantly differently.

[0029] Furthermore, a load holding device is provided, which is realized with a first and a second check valve 71; 72, each of which only allows a fluid flow from the pump channel to the actuator 90. The two separate check valves 71; 72 are due in particular to the particularly space-saving design of the first control slide 30, which with reference to Fig. 1 is explained in more detail. In a conventional system with an upstream pressure compensator, a single check valve would suffice.

[0030] Furthermore, a third control spool 60 is provided, via which the load signal is transmitted from the actuator 90 to the second control spool 50. The third control spool 60 separates the second control point 12, to which the actual load pressure from the actuator 90 is directly applied, from the third control point 13, whose pressure directly acts on the second control spool 50. The third control spool 60 is designed such that the pressures at the second and third control points are generally essentially equal. In this case, the option of reducing the pressure at the third control point below the pressure at the second control point is preferably deliberately utilized when this is advantageous.

[0031] The third control spool 60 is completely missing in a conventional system with an upstream pressure compensator. The aim of the present invention is to prevent a significant amount of pressurized fluid from flowing away from the actuator 90 via the load sensor, which would impair the fully effective load holding described above. At this point, it should be noted that a significant fluid flow can flow into the load sensor in order to adjust the displacement volume of the hydraulic pump connected there. Furthermore, the fourth control spool 81 is to be used within the scope of the present invention, via which pressurized fluid can also flow away from the load sensor to the tank channel 24. The two aforementioned fluid flows currently flow from the third control point 13, but not from the second control point 12.

[0032] The fourth control spool 85 is primarily intended for applications where very large masses are to be moved with the actuator 90, for example, the slewing gear of a hydraulic excavator. In this case, the existing load compensation would result in the pressure in the load-sensing channel 25 reaching very high values. This can be mitigated by opening the corresponding first secondary orifice 81. The first secondary orifice 81 is closed further, the higher the active first or second control pressure 37; 38 is.

[0033] Finally, attention should be drawn to the pressure relief valve 84, which can be used to limit the pressure at the third control point 13 to a predetermined upper value. The pressure relief valve 84 preferably comprises a second secondary orifice 82, which opens when the specified pressure limit is exceeded.

[0034] The pressure at the third control point 13 is connected to the load-sensing channel 25 via the third check valve 73. This only allows fluid flow from the third control point 13 to the load-sensing channel 25. As a result, the highest load pressure of all valve discs is present in the load-sensing channel 25. The discharge pressure of the hydraulic pump connected to the pump channel 23 is preferably set so that it is higher than the pressure in the load-sensing channel 25 by a predetermined pressure difference.

[0035] At this point, it should be noted that a special feature of the system according to US Pat. No. 5,305,789 A is that the load signal is transmitted via a load signaling channel that runs through the entire valve block. The valve disc in question is intended to be compatible with this system. The shuttle valve cascade, typically used in conjunction with an upstream pressure compensator, is not intended to be used.

[0036] Finally, the leakage oil connection 27 (see also Fig. 3), through which in particular the leaks at the fourth control slide 85 can be discharged.

[0037] Fig. 2 shows a longitudinal section of the valve assembly according to Fig. 1, wherein the cutting plane passes through the first and second control slides 30; 50. Fig. 2a shows one of the Fig. 2, with the first 30 and the second control slide 50 shown in section. For clarity, some reference numbers are shown in only one of these two figures.

[0038] The valve assembly 20 has a housing 20 which comprises a base body 26, which is preferably manufactured by casting and is subsequently machined. The base body 26 is penetrated by a circular-cylindrical bore relative to a longitudinal axis 14, in which bore the first control spool 30 is received for linear movement, wherein it is adapted to the bore in a largely leak-free manner. The first control spool 30 has a first and a second annular groove 31; 32 which run in a ring-like manner around the longitudinal axis 14. The two side edges of each annular groove 31; 32, which are opposite one another in the direction of the longitudinal axis 14, together with the base body 26, each form a first main orifice 33. The first main orifices 33 each comprise a plurality of fine control notches on the first control spool 30, so that their opening cross-section can be finely adjusted by moving the one-piece first control spool 30.

[0039] The two opposite ends of the first control spool 30 extend into a respective, separate control cover 93, which is firmly connected to the base body 26. The first and second control pressures 37; 38 are present in the two control covers 93, respectively, and act on the front side of the first control spool 30. At least one pilot valve 92 is screwed into one of the two control covers 93, which provides the two control pressures 37; 38. Two separate or a single pilot valve 92 can be provided. Furthermore, a separate first spring 34 is each accommodated in the two control covers 93, which preloads the first control spool 30 into its center position.

[0040] The second control spool 50 is accommodated in the base body 26 for linear movement, with its direction of movement running transversely to the longitudinal axis 14. The second control spool 50 is provided with a longitudinal bore 53 which is open towards the first control spool 30 and closed in the opposite direction. The interior of the longitudinal bore 53 is fluidically connected directly to channels in the base body 26 via elongated holes 54 in the second control spool 50, this region forming the first control point 11. In the context of the present application, a control point is understood to be a coherent cavity in which essentially the same pressure prevails throughout. A control point is delimited in particular by orifices at which a pressure drop occurs at least in some operating states of the valve assembly.The aforementioned elongated holes 54 do not act as orifices, since they release a large flow cross-section in every position of the second control slide 50.

[0041] In the area of ​​the longitudinal bore 53, several radial bores are provided in the second control slide 50, which together with a control edge on the base body 26 form a second main orifice 51, which is continuously adjustable. Fig. 2 or 2a, the second main orifice 51 is maximally open. When the pressure at the first control point 11 increases, the second control slide 50 is displaced against the force of the associated second spring 52, thereby reducing the opening cross-section of the second main orifice 52; in extreme cases, it may be completely closed.

[0042] A first fluid flow path leads from the pump channel 23 past the first control spool 30, via the second main orifice 51, further via the first control point 11, further via the first check valve 71, back to the first control spool 30, there via a first main orifice 33 at the first annular groove 31 to the first working port 21. The pressurized fluid, which typically flows back from the actuator at the same time, flows along a third fluid flow path from the second working port 22 via a first main orifice 33 at the second annular groove 32 to an associated tank channel 24.When the direction of movement of the actuator is reversed, the pressure fluid flows along a second fluid flow path from the pump channel 23 past the first control spool 30, via the second main orifice 52, further via the first control point 11, further via the second check valve 72, back to the first control spool 30, there via a first main orifice 33 at the second annular groove 32 to the second working port 22. The pressure fluid flowing back from the actuator at the same time flows along a fourth fluid flow path from the first working port 21 via a first main orifice 33 at the first annular groove 31 to an associated tank channel 24. The first and second check valves 71; 72 each only allow a fluid flow from the pump channel 24 to the respectively associated working port 21; 22, but not in the opposite direction, so that a load is maintained. That is,The actuator does not move in the opposite direction to the desired direction even if the pressure in the pump channel 24 is not sufficient to hold the load on the actuator.

[0043] The respectively effective load pressure is applied to the second control point 12, which comprises an annular groove in the base body 26, which surrounds the first control spool 30 in a ring-like manner. The load signal comprises a first and a second control channel 35; 36, which run concentrically to the longitudinal axis 14 in the first control spool 30. These are each designed as a blind hole drilled from an end face of the first control spool 30. The openings there are each closed fluid-tight with screw plugs 40. There is no fluid connection between the first and the second control channel 35; 36, wherein in particular the first radial bores 41 are arranged such that either the first or the second control channel 35; 36 is connected to the second control point 12.The second radial bores 42 are arranged such that the working connection 21; 22 connected to the pump channel 23 is connected to the respective associated control channel 35; 36, wherein this control channel 35; 36 is connected to the second control point 12. The third radial bores 43 are arranged such that the respective other control channel 36; 35 is connected to an associated tank channel 24.

[0044] Immediately adjacent to the annular grooves 31; 32, an associated first and second working connection 21; 22 is arranged on the housing 20. The two working connections 21; 22 are closed by covers that are removed during operation.

[0045] Fig. 3 shows a further longitudinal section of the valve assembly according to Fig. 1, wherein the cutting plane passes through the third and fourth control slide 60; 85;. The cutting plane runs parallel to the cutting plane of the Fig. 2 and is in the direction of view of the Fig. 2 arranged in front of the cutting plane there.

[0046] You can see the hole, which is part of the second control point 12, and which is inserted into a recess on the corresponding annular groove in Fig. 2. The pressure there acts on the third control slide 60 at the front, with further details Fig. 4 will be explained.

[0047] The third control point 13 is formed by a channel system, with all corresponding holes in Fig. 3 are marked with the reference number 13. Particular attention should be paid to the bore 13a, through which the third control point 13 is connected to the spring side of the second control slide (No. 50 in Fig. 2) is connected.

[0048] The third control point 13 is connected to a tank channel 24 via the pressure relief valve 84 already mentioned.

[0049] Furthermore, the third control point 13 is connected via the fourth control slide 85 to an associated tank channel 24, whereby the connecting hole 28 shown in dashed lines is located away from the cutting plane of the Fig. 3 is arranged. The fourth control spool 85 forms a continuously adjustable first secondary orifice 81, which is maximally open in the illustrated end position preloaded by the fourth spring 86. The third control pressure 39 acts on the fourth control spool 85 against the fourth spring 86 in the direction of reducing the size of the first secondary orifice 81. The free cross-section of the first secondary orifice 81 therefore decreases when the first control spool is hydraulically actuated. The first secondary orifice is designed such that a very small residual opening always remains, so that at least some pressurized fluid always flows from the third control point 13 via the first secondary orifice 81 to the tank channel 24. As a result, the pressure at the third control point 13 drops as long as no pressurized fluid flows to the third control point 13 via the third control spool 60.

[0050] The leakage oil connection 27 in the area of ​​the fourth spring 86 is permanently connected to a tank.

[0051] Fig. 4 shows an enlarged section of Fig. 3 in the area of ​​the third control slide 60. The third control slide 60 is accommodated in a separate sleeve 63 for linear movement, which is fixedly accommodated in an associated bore of the base body 26. The sleeve 63 is preferably held there by a (not shown) retaining screw, which is screwed into the internal thread 65, into which the locking screw (No. 64 in Fig. 3) is screwed in, with which the third control point 13 is closed to the outside.

[0052] The first control point 11 is connected to the sleeve 63 on the peripheral side. Radial bores 66 are provided in the sleeve 63, which, together with an annular groove on the third control slide 60, form a continuously adjustable third main orifice 61. The Fig. The position of the third control slide 60 shown in Figure 4 is preloaded by a third spring 62, which is so weak that it essentially does not affect the control processes explained below. In this position, the third main orifice 61 is completely closed.

[0053] The pressure at the second control point 12 acts on the front side of the third control spool 60 in the direction of enlarging the third main orifice 61, whereas the pressure at the third control point 13 acts on the third control spool 60 in the opposite direction. The hydraulically effective area is the same in both cases. The third main orifice 61 is connected to the third control point 13 via bores 68 in the third control spool 60. The third main orifice 61 subsequently opens when the pressure at the second control point 12 is greater than the pressure at the third control point 13. This releases a connection between the first and third control points 13, so that the pressure at the third control point 13 increases. It should be noted that the wiring described above means that the pressure at the first control point 11 is higher than the pressure at the second control point in almost all operating states.Something different only applies when the load holding explained above is activated.

[0054] If the pressure at the second control point 12 is lower than the pressure at the third control point 13, the third main orifice 61 is closed. At the same time, the pressure flows through the first sub-orifice (No. 71 in Fig. 3) Pressure fluid from the third control point 13, so that the pressure at the third control point 13 decreases. The pressure at the third control point 13 will therefore approach the pressure at the second control point 12. The time course of this approach depends on the fourth control slide (No. 85 in Fig. 3) from the first and second control pressure (No. 35; 36 in Fig. 1) off. Reference symbol 10 Valve assembly 11 first control point 12 second control point 13 third control point 13a Bore, which is part of the third control point 14 Longitudinal axis 20 housings 21 first working connection 22 second working connection 23 Pump channel 24 tank channel 25 load reporting channel 26 basic bodies 27 Leakage connection 28 connecting hole 30 first control slide 31 first annular groove 32 second ring groove 33 first main aperture 34 first spring 35 first control channel 36 second control channel 37 first tax print 38 second control pressure 39 third tax pressure 40 locking screw 41 first radial bore 42 second radial bore 43 third radial bore 50 second control slide 51 second main aperture 52 second spring 53 Longitudinal bore 54 elongated holes 60 third control slides 61 third main aperture 62 third spring 63 sleeve 64 locking screw 65 threads 66 Radial bore 67 Ring groove 68 Hole in the third control spool 71 first check valve 72 second check valve 73 third check valve 81 first secondary aperture 82 second sub-aperture 84 Pressure relief valve 85 fourth control slide 86 fourth spring 90 Actuator 91 shuttle valve 92 pilot valve 93 control cover

Claims

[1] Valve assembly (10) with a housing (20) having a first and a second working connection (21; 22), a pump channel (23) and at least one tank channel (24), wherein a first control slide (30) is accommodated in the housing (20) for linear movement relative to a longitudinal axis (14), wherein the first control slide (30) has a first and a second annular groove (31; 32) which are spaced apart from one another in the direction of the longitudinal axis (14), wherein the first and the second annular groove (31; 32) each form, together with the housing (20), two counter-adjustable first main orifices (33), wherein a second control slide (50) is accommodated in the housing (20) for linear movement, which, together with the housing (20), forms an adjustable second main orifice (51), wherein a first and a second check valve (71; 72) are accommodated in the housing (20), characterized bythat a first fluid flow path starting from the pump channel (23) via the second main orifice (51), further via a first control point (11), further via the first check valve (71), further via the first annular groove (31) to the first working connection (21), wherein a second fluid flow path leads from the pump channel (23) via the second main orifice (51), further via the first control point (11), further via the second check valve (72), further via the second annular groove (32) to the second working connection (22), wherein the first and the second check valve (71; 72) each exclusively direct a fluid flow to the respectively assigned first or second working connection (21;22), wherein a third fluid flow path leads from the first working connection (21) via the first annular groove (31) to an associated tank channel (24), wherein a fourth fluid flow path leads from the second working connection (22) via the second annular groove (32) to an associated tank channel (24), wherein a third control slide (60) is accommodated in the housing (20) in a linearly movable manner, which together with the housing (20) forms an adjustable third main aperture (61), wherein the housing (20) delimits a second control point (12) in sections, which is also delimited by the first control slide (30), wherein in the interior of the first control slide (30) there are first and second control channels (35;36) are provided, wherein the first control channel (35) is designed such that it establishes a fluid connection from the first working connection (21) to the second control point (12) only when the first fluid flow path is open, wherein the second control channel (36) is designed such that it establishes a connection from the second working connection (22) to the second control point (12) only when the second fluid flow path is open, wherein the pressure at the second control point (12) acts on the third control slide (60) in the opening direction of the third main orifice (61); [2] Valve assembly according to claim 1, wherein the pressure at the first control point (11) acts on the second control disc (50) in the closing direction of the second main orifice (51), wherein the second control disc (50) is acted upon by a second spring (52) in the opening direction of the second main orifice (51). [3] Valve assembly according to one of the preceding claims, wherein a fifth fluid flow path leads from the first control point (11) via the third main orifice (61), further via a third control point (13) to a side of the second control slide (50) which is acted upon by a second spring (52). [4] Valve assembly according to claim 3, wherein the pressure at the third control point (13) acts on the third control disc (60) in the closing direction of the third main orifice (61). [5] Valve assembly according to one of claims 3 or 4, wherein the housing (20) has a load sensing channel (25), wherein the pressure at the third control point (13) is connected to the load sensing channel (25) via a third check valve (73), wherein the third check valve (73) only allows a fluid flow from the third control point (13) to the load sensing channel (25). [6] Valve assembly according to one of claims 3 to 5, wherein the third control point (13) is connected to a respective associated tank channel (24) via at least one secondary orifice (81; 82), wherein the secondary orifices (81; 82) are connected in parallel if a plurality of secondary orifices (81; 82) are provided. [7] Valve assembly according to claim 6, wherein the at least one secondary orifice comprises a first secondary orifice (81) which is continuously adjustable and has a smallest opening cross-section other than zero. [8] Valve assembly according to claim 6 or 7, wherein the at least one secondary orifice comprises a second secondary orifice (82) which is part of a pressure relief valve (84). [9] Valve assembly according to one of the preceding claims, wherein the position of the first control slide (30) is adjustable by means of a first and a second control pressure (37; 38). [10] Valve assembly according to claim 9, dependent on claim 7, wherein the first secondary orifice (81) is adjustable such that its opening cross-section depends on the first and / or the second control pressure (37; 38). [11] Valve assembly according to claim 10, wherein the opening cross-section of the first sub-orifice (81) becomes smaller as the higher of the two pressures, first and second control pressure (37; 38), increases.

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