EP1481167B1 - Valve arrangement - Google Patents

Description

The invention relates to a valve arrangement for load pressure independent driving of consumers.

Such valve arrangements are used for example in LUDV systems, as they are known from WO 95/32364 A1 and the data sheet RD 64 127 / 04.98 (Hydro valves for mobile applications) are known. For example, a LUDV system includes a variable displacement pump that can be controlled to produce at its output a pressure that is above the highest load pressure of all hydraulic consumers by a certain amount.

Each of the consumers is associated with an adjustable Zumeßblende downstream pressure scale, the latter keeps the pressure drop across the Zumeßblende constant, so that the flow to the corresponding hydraulic load fluid quantity depends solely on the opening cross-section of Zumeßblende and not the load pressure of the consumer or the pump pressure. By the pressure compensators of the system is achieved that in the case where the hydraulic pump has been adjusted to the maximum displacement and the pressure medium flow is insufficient to maintain the predetermined pressure drop across the Zumeßblenden, the pressure compensators adjusted all actuated hydraulic consumers in the closing direction be so that all pressure medium flows are reduced by the same percentage. Due to this load-independent flow distribution (LUDV), all actuated consumers move at a speed that is reduced by the same amount.

In the solution according to the WO 95/32364 A1 it may happen with prolonged support of a consumer that it drops due to a low leakage flow between the pressurized fluid working port and the pressure fluid tank of the system.

To avoid such leakage flow is in the DE 196 46 447 A1 proposed to use in the respective work connection an openable check valve, which allows a leak-free shut-off leading to the consumer, pressurized working line. The disadvantage of this solution is that considerable space is required by placing the check valve on the working connection.

Instead of the attached check valve could run the designed in disc design valve housing with integrated check valve. Since such leak-free designs in comparison to the conventional embodiments described above only relatively rarely apply, such a custom-made could be realized only with relatively high financial cost. Such a valve arrangement is also in DE10033757 disclosed.

In contrast, the invention has for its object to provide a compact valve assembly that can be produced with minimal effort.

This object is achieved by a valve arrangement having the features of patent claim 1.

In the case of the valve arrangement according to the invention, the shut-off valve which enables the leak-free shut-off is designed with a pilot valve via which the shut-off valve can be opened to allow a pressure medium flow to the tank. According to the invention, the pilot valve actuated by an actuating movement of a main spool of a main valve, via which the working connections of the valve arrangement connected to the consumer can be connected to a pressure medium tank or a pressure channel leading to the pump pressure. According to the pilot valve is arranged substantially coaxially with the main slide of the pressure fluid flow direction determining main valve and is in operative connection with this, so that the valve assembly is very compact buildable. The solution according to the invention with the directly operated via the main valve pilot valve makes it possible to attach to a standard disc laterally a valve housing in which the pilot valve, the associated check valve and the associated working port are formed.

According to the invention it is preferred if the end face of the main valve of the main valve is formed a plunger, which lifts the pilot piston from its pilot seat with appropriate control of the main spool, so that an effective in the closing direction control surface of the check valve is relieved.

The main slide is particularly simple when the plunger is used as an insert in the main slide.

The laterally mounted valve housing can be particularly compact build by the axis of the pilot valve in parallel distance from the axis of the check valve.

In a particularly simple design solution, the effective in the closing direction control surface of the check valve is connected via the pilot valve with a control terminal, which in the above-described axial displacement of the main spool of the main valve comparatively low, for example, the tank pressure corresponding pressure leads.

In order to prevent a sudden rupture of the check valve, the pilot piston of the pilot valve is preferably provided with Feinsteuernuten over which the connection to the low pressure port, such as the control port described above, is gradually turned on.

To avoid pressure peaks and cavitation phenomena, a pressure relief / suction valve is assigned to the check valve. One connection of this valve is connected via a tank channel to a tank connection of the valve arrangement. The structure of the laterally mounted valve housing is particularly simple if this tank channel surrounds a housing cartridge of the check valve as an annular channel, which preferably extends from the laterally mounted valve housing into the valve disc.

The main slide is biased by a return spring means in its neutral position. This return spring device is designed such that the counteracting the direction of adjustment for actuating the pilot valve effective return spring is effective only after a predetermined initial stroke of the main spool, so that the main spool initially only has to be moved substantially against the force acting on the pilot piston force.

This is achieved in a preferred embodiment, characterized in that the relevant return spring is supported on a spring plate, which runs only after the aforementioned initial stroke on a support shoulder, so that after emergence, the further axial displacement the main slide against the force of the return spring takes place.

In a preferred embodiment, the main valve forms a variable Zumeßblende, which is connected downstream of a two working ports common pressure balance, the axis of which can be accommodated preferably perpendicular to the axis of the main valve in the valve disc.

Other advantageous developments of the invention are the subject of the other dependent claims.

• Figur 1 ein stark vereinfachtes Schaltschema der erfindungsgemäßen Ventilanordnung;
• Figur 2 einen Schnitt durch eine erfindungsgemäße Ventilanordnung in Scheibenbauweise und
• Figur 3 eine Teildarstellung der Ventilanordnung aus Figur 2.

In the following a preferred embodiment of the invention will be explained in more detail with reference to schematic drawings. Show it:

• FIG. 1 a highly simplified circuit diagram of the valve assembly according to the invention;
• FIG. 2 a section through a valve assembly according to the invention in disc design and
• FIG. 3 a partial view of the valve assembly FIG. 2 ,

The valve assemblies described below are used to control mobile equipment, such as shovels and are usually designed in disc design. In this case, several of the valve discs are combined to form a control block, wherein the valve elements for each function (operate bucket, travel drive, lifting / lowering) are each combined in a valve disc.

FIG. 1 shows a highly simplified hydraulic diagram of a directional control valve element 2 for controlling a double-acting hydraulic cylinder 4th

The directional control valve element 2 is designed with a pressure connection P, a tank connection T, two working connections A, B, one LS connection (not shown) and two control connections a, b. The working port A is connected to a piston bottom side cylinder chamber 6 and the other working port B with an annular space 8 of the hydraulic cylinder. The directional control valve element 2 comprises a main valve 10 designed as a continuously adjustable directional control valve whose main slide 12 is biased by a return spring device 14 into the illustrated zero position. The displacement of the main spool 12 is effected by applying a control pressure via the two control terminals a, b. As will be explained in more detail below, the main valve 10 is provided with a speed part forming a metering orifice (in FIG FIG. 1 not shown) and a pressure medium flow to or from the spaces 6, 8 determining direction part executed. The metering orifice is a in FIG. 1 schematically indicated pressure compensator 16 downstream, which is acted upon in the opening direction by the pressure at the outlet of Zumeßblende and in the closing direction of the load pressure at the consumer (hydraulic cylinder 4). As mentioned above, the downstream pressure compensator 16 keeps the pressure drop across the metering diaphragm formed by the main valve 10 constant, so that a load pressure-independent flow distribution (LUDV) is made possible. Such LUDV controls are from the prior art, for example the WO 95/32364 A1 known, so that further explanations are unnecessary.

In the event that the hydraulic cylinder 4 is to be kept in an extended position, the pressure medium be clamped leak-free in the cylinder chamber 6. For this purpose, a pilot operated check valve 18 is provided in the directional control valve element 2, whose pilot valve 20 is arranged approximately coaxially with the valve axis of the main valve 10. That is, check valve 18 and pilot valve 20 are arranged separately from one another in the variant according to the invention. The check valve 18 allows a flow of pressure medium from the main valve 10 to the working port A; a pressure medium flow in the reverse direction is possible only when the pilot valve 20. About the pilot valve 20 can be relieved in the closing direction of the check valve effective control surface, so that the check valve 18 is controlled by the pressure in the cylinder chamber 6 and a flow of pressure medium from the cylinder chamber 6 toward the tank connection T is possible. The actuation of the pilot valve 20 according to the invention via a plunger 22 of the main slide 12, via which a pilot piston 24 can be lifted from a valve seat, so that the pressure acting on the effective in the closing direction control surface of the check valve 18 pressure means to the control port a can be relaxed. This leads to a displacement of the main spool 12 to the pilot valve 20 toward a control pressure that corresponds approximately to the tank pressure.

In a working channel 26 between the working port A and the main valve 10, a pressure / Nachsaugventil 28 is arranged, on the one hand limits the pressure in the working channel 26 to a maximum value and on exceeding a pressure leading to the tank port T tank channel 30 aufsteuert and in the case a very rapid extension movement of the hydraulic cylinder 4, for example, caused by driving movements, etc., a suction of pressure medium from the tank channel 30 allows.

In a leading to the working port B further working channel 32 is a pilot operated pressure / feed valve 34 is provided, via which the pressure in the further working channel 32 can be limited to a variable maximum value and can be fed via the pressure medium from the tank channel 30 into the further working channel 32.

By combining several of the above-described directional control valve elements 2 with an input element and a closure plate can be a very compact control block to solve mobile hydraulic tasks put together, which can be easily adapted to different operating conditions due to the sandwich construction.

In FIG. 2 is a sectional view of a directional control valve element 2 according to FIG. 1 shown. Such designed in disc design way valve element has a valve disc 36, which is essentially a standard component, as described for example in the data sheet RD 64 127 / 04.98 the applicant. Laterally to the valve disc 36, a valve housing 38 is attached, in which those valve elements are summarized, which are not available in a standard version according to the aforementioned data sheet.

In the valve disc 36, the working port B, the pressure port P, the tank port T, the control port b, not shown, and the LS port are formed. The valve disc 36 is penetrated by a valve bore 40 in which the main spool 12 of the main valve 10 is guided. In the valve bore 40 open in the radial direction, a central pressure chamber 42, a pressure compensator channel 44, two connecting channels 46, 48, the working channel 26, the other working channel 32 and tank channel sections 50, 52. The main slide 12 is at its left end portion with a frontal annular collar 54 and formed at its right end portion with a collar 56. Furthermore, the main spool 12 has two control collars 58, 60 of the directional part, wherein the control collar 58 is assigned to the working port A and the control collar 60 to the working port B. Between the two control collars 58, 60 is located at Meßblendenbund 62, which is provided in both annular end faces with fine control grooves 64.

In the illustrated basic position of the main slide 12, the end-side annular collars 54, 56 close the tank channel sections 50, 52, the control collars 58, 60 the two connection channels 46, 48 and the fine control grooves 64 of the Meßblendenbundes 62 are shut off by the central web of the valve bore 40.

On the in FIG. 2 right side surface of the valve disc 36, the return spring means 14 is placed. This has a return spring 68, whose in FIG. 2 right end portion is supported on a spring plate 70 which is guided axially displaceably on a front side inserted into the main slide 12 sliding guide 72. This slide has a radial shoulder 74 against which the spring plate 70 is biased by the force of the return spring 68 to the right.

The other end of the return spring 68 is supported on a further spring plate 76, which in turn is biased by the return spring 68 against the end face of the main spool 12. In this basic position is located between the in FIG. 2 left end face 78 of the spring plate and an abutment shoulder 80 a game S. as off FIG. 2 As can be seen, the further spring plate 76 is slidably guided on the right-hand annular collar 56 of the main slide 12 and on the sliding guide 72. The spring plates 70, 76 can thus move toward one another during an axial displacement of the main slide 12. Which the return spring 68 and the spring plate 70, 76th receiving spring chamber 82 is encompassed by a cap 84 and can be acted upon by the pressure at the control terminal b.

As based on FIG. 1 explained, the working port 32 associated with the working port B can be connected via the pressure / feed valve 34 to the tank channel T to limit the pressure in the working channel 26 or to suck pressure medium from the pressure tank. This in FIG. 2 illustrated pressure / feed valve is designed with pilot control. It is a standard executed in cartridge design standard component, so that further explanations are unnecessary.

In the pressure compensator duct 44, the pressure compensator 16 is used, the valve axis extends at right angles to that of the main valve 10. The pressure compensator piston 82 is acted upon in the opening direction by the pressure downstream of the orifice 82 defined by the Meßblendenbund 62 and in the closing direction by the pressure on the LS channel and the force of a control spring.

The output terminal 84 of the pressure compensator 16 is connected via a respective load-holding valve 86, 88 with the connection port 46 assigned to the working connection A or the connection port 48 assigned to the working connection B. Such a load-holding valve 86 is, in principle, a check valve which allows a flow of pressure medium from the output connection 84 of the pressure compensator 16 to the associated channel 44 or 46 and shuts off in the opposite direction.

At the in FIG. 2 illustrated embodiment of the provided at the standard valve disc 36 working port A is shut off with a closure member 90. The working connection A is in the laterally attached Valve housing 38 is formed. In this valve housing 38 coaxial with the main valve 10 formed pilot valve 20, the associated therewith the check valve 18 and the working port A associated pressure / Nachsaugventil 28 are added, the axes of these valve elements parallel (18, 28) and coaxial (20) Axle of the main valve 10 run.

Details of the valve housing will be described below with reference to the partial view FIG. 3 explained.

The check valve 18 has a housing in a cross-bore 96 cartridge 92, the valve housing 38 in the horizontal direction (view FIG. 3 ) and whose end portion 94 dips into an associated with the working channel 26 extension of the transverse bore 96 in the valve disc 36.

The housing cartridge 92 has a stepped axial bore 98, on which a valve seat 100 is designed, against which a cone 102 of the check valve 18 is biased by a compression spring 104. This is based on a screwed into the housing cartridge 92 screw plug 106 from.

In the axial bore 98 opens a radial bore star 108 of the housing cartridge 92, which in turn is connected to a leading to the working port A channel 110. In the region of the radial bore star 108, a connecting bore 109 is formed in the jacket of the cone 102, via which a pressure spring 104 receiving spring chamber 105 is connected to the channel 110, so that the check valve in addition to the force of the compression spring 104 by the pressure in the channel 110 against the Valve seat 100 is biased.

In the valve housing 38 of a further designed as an angular bore tank bore 112 is further formed, the horizontal limb (view FIG. 3 ) does not intersect the channel 110. This can be achieved, for example, by the tank bore 112 being offset from the channel 110. Furthermore, both the working channel and the tank channel can be formed by parallel holes.

In the illustrated embodiment, the tank bore 112 is formed by a vertical bore and a horizontal bore intersecting the latter, the vertical bore being closed by a closure member 114, while the pressure / suction valve 28 is inserted into the horizontal bore. According to FIG. 3 The tank bore 112 opens into an annular space 116, which is delimited by a radially widened part of the transverse bore 96 of the valve housing 38 and the outer circumference of the end portion 94 of the housing cartridge 92. In this annular space 116 of the tank passage portion 50 opens, so that the tank bore 112 is connected to the tank port T.

According to FIG. 3 For example, the pressure / suction valve 28 has a suction piston 118 which is biased against a seat 122 by a spring 120. In Nachsaugkolben 118, a pressure limiting piston 124 is guided, which is biased by a pressure limiting spring 126 against a valve seat, not shown in the Nachsaugkolben 118. In the illustrated embodiment, the pressure limiting spring 126 engages a plate 128, which is formed on a projecting in the spring chamber portion of the pressure-limiting piston 124.

In the valve housing 38, a control channel 130 is further formed, on the one hand in a radial bore 132 of the housing cartridge 92 and on the other hand in a Pilot valve 20 receiving graduated pilot bore 134 opens. In this, the pilot piston 24 is biased by a pilot spring 136 against a pilot seat 138, wherein the pilot spring 136 is supported on a closure piece 140. About this valve seat 138, the pilot hole 134 opens into a control chamber 142, in which the left annular collar 54 of the main spool 12 is immersed and which is connected to the control terminal a. In the end face of the annular collar 54, a tappet 22 carrying insert 144 is inserted, wherein the plunger 22 is formed such that it can dip into the pilot seat 138 to lift the pilot piston 24 against the force of the pilot spring 136 from the pilot seat 138. The pilot piston 24 is designed as a stepped piston, wherein the co-operating with the pilot seat 138 cone of the pilot piston 24 has a substantially smaller diameter than the adjacent annular end face 135 or the rear end face 137 of the pilot piston 24. On the outer circumference of the pilot piston 24 Feinsteuerkerben 139 are formed, via which a of the annular end face 135 and the pilot seat 138 limited pressure chamber is connected to the control channel 130. The voltage applied in this pressure chamber pressure is tapped via a pilot piston 24 passing through the compensating bore 152 and reported in the spring chamber 136, so that the end faces of the pilot piston 24 are substantially pressure balanced.

The opening into the pilot hole 134 section of the control channel 130 is in turn formed by a bore which is closed by means of a closure member 146.

To extend the hydraulic cylinder 4, a control pressure is applied to the control terminal a, while the control terminal b is connected to the tank or other low-pressure source. Through the on the faces acting pressure difference, the main spool 12 from its spring-biased home position ( FIG. 2 ) moved to the right. In this case, the connection between the pressure chamber 42 and the pressure compensator channel 44 is opened via the fine control grooves 64 - the Zumeßblende 82 is opened and pressure medium can flow to the input port of the pressure compensator 16. As stated above, this arises in response to the load pressure acting and the pressure downstream of the orifice 82 in a control position, in which the pressure drop across the orifice 82 is held constant load pressure independent. The pressure medium flows from the pressure compensator 16 via the load-holding valve 86 into the connection channel 46. Due to the axial displacement of the main spool 12 has formed by the control collar 58 control edge, the connection between the connecting channel 46 and the other working channel 32 so that the pressure medium via the working channel 26 can flow into the axial bore 98 of the housing cartridge 92 of the check valve 18. The pressure of the pressure medium is so great that the cone 102 is lifted against the force of the compression spring 104 and the low pressure force in the spring chamber 105 from the valve seat 100 and the pressure fluid via the radial bore star 108 and the channel 110 to the working port A and from there via a working line 148 ( FIG. 1 ) can flow into the cylinder chamber 6 - the piston of the hydraulic cylinder 4 extends. The pressure medium displaced from the annular space 8 flows via the line 150 (FIG. FIG. 1 Due to the axial displacement of the main spool 12, the right-hand end annular collar 56 with a control edge on the connection between the working channel 26 and the tank channel section 52 aufgesteuert so that the pressure fluid from the working channel 32 to the tank port T. can flow out.

When exceeding a set via the pressure / Nachsaugventil 28 maximum pressure of the smaller pressure relief piston 124 is lifted from its seat in Nachsaugkolben 118 against the force of the pressure relief spring 126 (to the right), so that the connection to the tank bore 112 is opened and pressure medium through the tank bore 112th , the annular space 116 and the tank channel portion 50 can flow out to the tank port T out until the pressure at the working port A has fallen below the maximum set pressure.

The pressure / feed valve 34 is known to be designed with a Nachsaugfunktion, so that can be fed from the tank channel section 52 into the working channel 26 to avoid cavitation pressure medium.

When extending the hydraulic cylinder 4, the pilot valve 20 is closed, since this is biased by the force of the pilot spring 136 against the pilot seat 138. The pressure forces acting on the pilot piston 24 are substantially balanced, since the valve seat has a substantially smaller cross-section with respect to the end faces of the pilot piston and the end face portions of the pilot piston (apart from the surface of the pilot seat 138) are subjected to the same pressure.

After the initial stroke S of the spring plate 76 runs on the abutment shoulder 80, so that the further axial displacement of the main slide 12 is then possible only against the force of the biased return spring 68. After passing through this initial stroke S, the pilot piston 24 is turned on so far that this is completely pressure balanced, so that the force acting on the main spool 12 from the side of the pilot valve 20 is negligible and thus its axial displacement only by the pressure at the control terminal b and Force of the return spring 68 (also about 5 bar) is affected. By this initial stroke S is thus effected that the main spool when opening the pilot valve and the corresponding omission of the pressure force (5 bar) is not abruptly moved to the left, so that a continuous control is ensured.

The Feinsteuerkerben 139 ensure that the check valve 18 is relieved only gradually, so that a sudden lowering of the load can be prevented.

In the case in which the pressure in the channel 110 drops below the tank pressure (risk of cavitation), the suction piston 118 lifts off from its seat 122 against the force of the spring 120, so that pressure medium can be fed into the channel 110 via the tank bore 112.

To hold the load, the main valve 10 is moved back to its neutral position, so that the check valve 18 is moved back by the force of the compression spring 104 in its locking position in which the cone 102 rests on the valve seat 100 and the pressure medium is clamped in the cylinder chamber 6 leakage-free.

To lower the load of the control terminal a is connected to the tank or a low pressure source, while the control terminal b is applied a control pressure over which the main spool 12 is moved to the left. Due to the game S set via the spring plate 56, the main slide 12 initially performs an initial stroke in which the restoring spring 68 still has no effect. During this initial stroke of the plunger 22 runs on the pilot piston 24, so that its closing cone forming an axial projection is lifted from the pilot seat 138. That is, during this initial stroke, the axial displacement of the main spool 12 takes place against the force of Pilot spring 136, which corresponds for example to about 5 bar pressure. Due to the axial displacement of the pilot piston 24, the connection between the pilot seat 152 and the control channel 130 is gradually opened via the Feinsteuerkerben 139, so that pressure medium from the spring chamber 105 of the check valve 18 via the radial bore 132, the control channel 130, the fine control notches 139, the pilot seat 138 and the control chamber 142 can flow to the connected to the pressure medium tank control port a back - the check valve 18 is relieved on the back. Then, the cone 102 can be lifted by the force acting on its annular surface 154 load pressure from the valve seat 100, so that the pressure fluid from the working port A via the channel 110, the axial bore 98, the other working channel 32 and the annular collar 54 controlled tank passage portion 50 to the tank port T. flow out. At the same time, the pressure medium via the Zumeßblende 82, the pressure compensator 16, the connecting channel 48 and the controlled by the control collar 60 working channel 26 to the working port B and from there into the annulus 8 - the hydraulic cylinder 4 retracts.

Disclosed is a valve arrangement for load pressure independent driving of consumers with a main valve having a directional part and a Zumeßblendenteil. The valve arrangement has a shut-off valve for the leak-free shut-off of a working line leading to the consumer. This check valve is designed with a pilot valve, via which an effective in the closing direction pressure chamber of the check valve to a tank or a low pressure source is relieved. The pilot valve is opened according to the invention by a main spool of the main valve.

LIST OF REFERENCE NUMBERS

2

Way valve element

4

hydraulic cylinders

6

cylinder space

8th

annulus

10

main valve

12

main slide

14

Return spring means

16

pressure compensator

18

check valve

20

pilot valve

22

tappet

24

pilot piston

26

working channel

28

Pressure / anti-cavitation valve

30

tank channel

32

further working channel

34

Printing / feed

36

valve disc

38

valve housing

40

valve bore

42

pressure chamber

44

Pressure balance channel

46

connecting channel

48

connecting channel

50

Tank channel section

52

Tank channel section

54

frontal collar (left)

56

frontal collar (right)

58

control collar

60

control collar

62

Meßblendenbund

64

fine control

68

Return spring

70

spring plate

72

slide

74

radial shoulder

76

another spring plate

78

left end face spring plate

80

contact shoulder

82

orifice

84

output terminal

86

Load-holding valve

88

Load-holding valve

90

Screw

92

housing cartridge

94

end

96

cross hole

98

axial bore

100

valve seat

102

cone

104

compression spring

105

spring chamber

106

Screw

108

Radial bore star

110

channel

112

tank bore

114

closing piece

116

annulus

118

Nachsaugkolben

120

feather

122

Seat

124

Pressure limiting piston

126

Pressure relief spring

128

Plate

130

control channel

132

radial bore

134

pilot drilling

135

Annular face

136

pilot pen

137

face

138

pilot seat

139

Metering notches

140

closing piece

142

control room

144

insert

146

closing part

148

working line

150

management

152

compensating bore

154

ring surface

Claims (12)

1. Valve assembly for load pressure-independent control of consumers (4), including a main valve (10) for regulating a pressure medium flow to or from the consumer, wherein in a pressure medium flow path between a work port (A) and the main valve (10) a shut-off valve (18) is arranged which permits a pressure medium flow to the work port (A) and which is capable of being controlled open in the opposite direction through the intermediary of a pilot valve (20) having a valve axis arranged at a parallel distance from the axis of the shut-off valve (18), wherein a pilot piston (24) of the pilot valve (20) is adapted to be raised from a pilot control seat (138) by displacing a main slide (12) of the main valve (10), characterized in that the valve axis of the pilot valve (20) is arranged about coaxially with the axis of the main valve (10), with the main slide (12) and the pilot piston (24) being in operative connection through a tappet (22).
2. Valve assembly in accordance with Claim 1, wherein the tappet (22) is formed on an insert member (144) inserted in an end face of the main slide (12).
3. Valve assembly in accordance with any one of the preceding claims, wherein the pilot valve (20) and the shut-off valve (18) are arranged in a common valve housing (38) that is added on to an end face of a valve disc (36) accommodating the main valve (10).
4. Valve assembly in accordance with Claim 3, wherein at least one work port (A) is formed at the valve housing (38).
5. Valve assembly in accordance with any one of the preceding claims, wherein a spring chamber (105) of the shut-off valve (18) is capable of being connected via the pilot valve (20) with a low-pressure port, preferably a control port (a) conducting the control pressure that acts on the main slide (12) in a direction away from the pilot valve (20).
6. Valve assembly in accordance with Claim 5, wherein the pilot piston (24) includes fine-control notches (139) for gradually opening the connection to the low-pressure port (a).
7. Valve assembly in accordance with any one of the preceding claims, wherein the shut-off valve (18) is followed downstream by a pressure/anti-cavitation valve (28).
8. Valve assembly in accordance with Claim 7, wherein a port of the pressure/anti-cavitation valve (28) is connected via a tank bore (112) with a tank port (T), the tank bore (112) encompassing a housing cartridge (92) of the shut-off valve (18) as an annular chamber (116).
9. Valve assembly in accordance with any one of the preceding claims, wherein there is associated to the main slide (12) at least one reset spring means (14) acting, after a predetermined initial stroke (S) of the main slide (12), contrary to the actuation force necessary for actuation of the pilot piston (24).
10. Valve assembly in accordance with Claim 9, wherein the reset spring means (14) comprises a reset spring (68) supported on a spring cup (76) that enters into contact against a contact shoulder (80) following the initial stroke (S).
11. Valve assembly in accordance with Claim 3 and 8, wherein the housing cartridge (92) merges into a work passage (26) of the valve disc (36).
12. Valve assembly in accordance with Claim 3, wherein with the aid of the main valve (10) a variable metering throttle (82) is formed, downstream from which a pressure compensator (16) accommodated in the valve disc (36) is arranged.

Images