EP2799722B1 - Hydraulic control device - Google Patents

Description

The invention relates to a hydraulic control according to the preamble of claim 1.

A generic hydraulic control according to EP 24 66 153 A1 provides for the hydraulic consumer in an open neutral position of the three-position proportional directional slide a floating position in which the load-holding valves are acted upon at their Aufsteuerseiten simultaneously with the same control pressures that are tapped by Druckvorsteuerungen the directional slide when both proportional magnets are energized simultaneously and the same. By contrast, the hydraulic consumer is hydraulically blocked in the open neutral position of the directional slide, that the Aufsteuerseiten the load-holding valves remain pressure-relieved and shut off the load-holding valves, the proportional solenoids are not energized. If the hydraulic consumer is controlled in one direction or the other, only a load-holding valve is acted upon on its control side with a control pressure, which is tapped from the pressurized working line and relatively high. In order to fully open up the two load-holding valves even in the floating position, the simultaneously acting control pressures from the pressure pilot controls of the directional slide should also be relatively high, for example about 60 bar, ie, for which both proportional magnets must be energized at the same time and at the same time relatively strong to maximum. This can lead to inappropriate floatation due to improper heating by the proportional solenoids. Although it would be possible to select the so-called open-circuit ratio of the load-holding valves at considerable expense such that they can already be opened with relatively low control pressures of approximately 20 bar from the pressure pilot controls of the proportional directional slide. Here, although the heat development of the simultaneously energized proportional solenoid would be lower, but would be in a direction control of the hydraulic consumer of relatively high, tapped from the pressurized working line control pressure the respective a load-holding valve inadvertently quickly or abruptly aufsteuern, because for its pressure value, the open-loop ratio would be too high. There would also be a risk of instabilities in switching operations.

Out EP 12 81 872 A and EP 20 31 256 A known hydraulic controls that can be set in addition to the direction control of the hydraulic consumer whose hydraulic blocking but also a floating position, require a structurally complex and expensive four-position proportional directional slide. In the floating position connects the in an open Neutral position switched directional slide directly a control pressure supply with the Aufsteuerseiten of the two load-holding valves to jointly aufzusteuern this. The hydraulic blocking is controlled in a closed neutral position.

Out BE 656 144 A For example, a logic element for fluids is known that is equipped to provide a NOT function or an "EQUALITY function" with two different sized spools. In an embodiment with three spool pistons of different sizes, a "NEVER-NOCH-function" is achieved. In the "NOT function," a fluid connection is released from an inlet to an outlet if there is no control pressure or the control pressure does not exceed a certain size. In the "EQUALITY function", a flow connection from the inlet to the outlet is released when a control pressure applied is equal to the inlet pressure. With the "NO-NOR-function" a flow connection from the inlet to the outlet is then released, if neither a first nor a second control pressure is applied.

Further prior art can be found in EP 1 106 840 A2 . US 3,547,156 A . FR 1 500 028 A . WO 2009/003500 A1 and US 2005/242312 A1 ,

The invention has for its object to provide a hydraulic control that is inexpensive and reliable. The hydraulic control should allow the floating position and the hydraulic blocking of the hydraulic consumer with a cost-effective and small-sized three-position proportional directional slide and simple load-holding valves.

The stated object is achieved with the features of claim 1.

Since in the hydraulic control the floating position is set by simultaneous and equal energization of the proportional solenoids of the three-position directional valve, however, the control pressures set by the proportional solenoids are not transmitted to the load-holding valves, but only to the and-logic element in the control pressure circuit, and the logic element responds, To connect the Aufsteuerseiten both load-holding valves directly to the control pressure supply, is used to open the relatively high and constant control pressure from the control pressure supply, while sufficient to switch the logic element relatively moderate control pressures, as it is not primarily on the pressure level, but on the simultaneous concerns of both control pressure signals arrives. These moderate or low control pressures require only a relatively weak energization of the two proportional magnets, so that no more heating problem occurs by them even with longer held floating position. Since the proportional solenoids are designed so that one alone maximum energized Even if no heating problem is caused over a longer period of time, both proportional magnets can be energized simultaneously, for example at about half maximum intensity or less, which will not cause any heating problems even with a longer energizing time since this generates approximately the same heat as a maximum energized one Proportional magnet alone. The hydraulic and logic element links, so to speak, the two simultaneously occurring control pressure signals which generate the two proportional solenoids in the directional slide in order to connect the control pressure supply to the control sides of the load-holding valves. If only one control pressure signal from a proportional solenoid is present, the logic element interrupts a pressure transmission between the control pressure supply and the control sides of the load-holding valves. The and logic element is structurally simple and reliable and can be easily integrated into the control pressure circuit of the hydraulic control. Simple load-holding valves can be used. The control behavior is stable and yet sensitive.

In an expedient embodiment of the hydraulic control, the same control pressures are set on the control sides of the two load-holding valves and thus the load-holding valves are opened in the same way.

In another embodiment, on the other hand, unequal control pressures are set on the control sides of the load-holding valves in order to control the load-holding valves differently and / or differently from one another, if appropriate also in the direction control of the hydraulic consumer, and not only in the floating position. This is preferably accomplished via different nozzle populations in the connections and optionally also in discharge lines connected to the connections to the tank. This means that, although the responsive logic element first receives the high control pressure from the control pressure supply, e.g. about 60 bar, releases, but this control pressure is modulated or reduced on the way to Aufsteuerseite. With the nozzle assembly, for example, a user-specific adjustment of the Aufsteuerverhaltens and / or maximum Aufsteuerquerschnitts each load-holding valve can make.

In an expedient embodiment, the and logic element is associated with a discharge relief to the tank comprehensive pressure relief at least for the connections to the Aufsteuerseiten the load-holding valves. About this pressure relief at least the Aufsteuerseiten the load-holding valves are relieved, for example, when the hydraulic consumer must be hydraulically blocked, ie the load-holding valves or one must reliably hold a load.

Particularly expediently, the pressure relief is even incorporated into the logic element and so that the logic element in the control pressure circuit fulfills a further function, in which it also provides for the pressure relief when the operating situation requires it. This is effected particularly advantageously by means of a discharge function monitoring, derived from the response of the logic element on the two simultaneously applied control pressure signals slide function in the logic element. For example, if the float position is set, the discharge line is automatically disconnected from the tank.

Alternatively, however, the pressure relief could also take place in another way and separated from the logic element, for example with a nozzle in the discharge line and / or with a relief switching valve, which is deliberately actuated to relieve.

In particular, in an embodiment in which for the floating position the control sides of both load-holding valves are acted upon with substantially the same control pressure from the control pressure supply, in a particularly advantageous embodiment in each load-holding valve an application-specific selectable mechanical limit of the Aufsteuerquerschnitts is incorporated. After usual handling limiting hydraulic and / or mechanical devices are provided separately from the load-holding valves in parallel loops. Its purpose is to limit, for example, the lowering rate of the hydraulic consumer to a value desired by the user, which the fully opened load-holding valve could not limit because its full control cross section would be too large. By incorporating the limitation directly into the load-holding valve assemblies and additional equipment can be saved.

A particularly cost-effective and simple limitation has, for example, a screw-adjustable limit stop for the opening stroke of the load-holding valve, which is optionally adjustable from the outside, or a replaceable but built-in limit stop, such as a spacer or a spacer.

In an advantageous embodiment, an unlocking plunger is loaded by spring force in the closing direction of the check valve, and is provided between the actuating piston a relative idle stroke between these limiting coupling. To unlock the check valve, this idle stroke must first be overcome by the other actuating piston.

In a preferred embodiment, the one actuating piston is a pot piston which can be moved in a first control pressure chamber over a limited stroke and which preferably carries the other one designed as a solid piston, actuating piston axially slidably receives in a limited between the actuating piston second control chamber and contains a Leerhubanschlag for the other actuating piston as a coupling. The other actuating piston ultimately actuates the plunger to unlock the check valve, but only if both actuating pistons are simultaneously acted upon in each case with a control pressure signal in the first and second control pressure chamber. The series arrangement of the actuating piston ensures that when only applying a control pressure, the check valve is not unlocked.

A particularly expedient embodiment is characterized by a 2/2-way slide function, which is incorporated for the one actuating piston in the and logic element. This slide function is used to release a pressure relief to the tank when the check valve is not or no longer unlocked. Pressure medium from control pressure lines, which must be relieved of pressure in this phase of operation, takes the path via the open slide function through the logic element to the tank. For this purpose, the first control pressure chamber may be provided with a spool bore portion for a spool end of the one actuating piston. The spool bore portion may be bounded by a sealing ring in the axial direction. At this slide bore section of the tank and a discharge relief required for discharge or one side of the check valve are connected. Via the slide function, the discharge line and the tank can be connected or disconnected. In this way, the logic element in a hydraulic control assumes another function.

Suitably, the check valve is acted upon in the reverse direction with control pressure from a control pressure supply to a hydraulic control. As soon as the non-return valve is unlocked via both actuating pistons, it connects the control pressure supply with at least one connection to a pressure-dependent operable valve, preferably a load-holding valve openable against spring force in the hydraulic control. This offers the advantage that the two actuating pistons reliably unlock the check valve when relatively low control pressure signals are present at the same time. The unlocked check valve, however, releases a higher or functionally necessary high control pressure, as the two control pressure signals.

Structurally and manufacturing technically simple and logic element is designed as Einschraubventil that can be used in a block bore. Alternatively, the and logic element can of course be designed in block design as a separate assembly.

Fig. 1

ein Blockschaltbild einer ersten Ausführungsform einer Hydrauliksteuerung,

Fig. 2

einen Längsschnitt einer Ausführungsform eines Lasthalteventils, wie es beispielsweise in Fig. 1 in symbolischer Darstellung vorgesehen ist,

Fig. 3

ein Blockschaltbild einer weiteren Ausführungsform einer Hydrauliksteuerung, und

Fig. 4

einen Längsschnitt eines hydraulischen Und-Logikelementes, das beispielsweise in den Hydrauliksteuerungen der Fig. 1 und 3 verwendet ist, aber auch in anderen sicherheitsrelevanten Einsatzfällen brauchbar ist, und u.a. aus diesem Grund eigenständige erfinderische Bedeutung hat.

With reference to the drawings, embodiments of the subject invention will be explained. Show it:

Fig. 1

a block diagram of a first embodiment of a hydraulic control,

Fig. 2

a longitudinal section of an embodiment of a load-holding valve, as for example in Fig. 1 is provided in symbolic representation,

Fig. 3

a block diagram of another embodiment of a hydraulic control, and

Fig. 4

a longitudinal section of a hydraulic And logic element, for example, in the hydraulic controls of Fig. 1 and 3 is used, but is useful in other security-related applications, and has, inter alia, for this reason independent inventive importance.

In the block diagram of Fig. 1 is of a hydraulic control H, which optionally has a plurality of sections and for the sections together a pump line P, a return line R (to a pump / tank assembly) and to a control pressure supply (not shown) connected control pressure line Z, a section for controlling a double-acting hydraulic consumer V, eg a hydraulic cylinder shown. The control pressure line Z is for example from a (not shown) control pressure pump or via a (not shown) Pressure reducing valve supplied by the pump line P with a substantially constant control pressure of eg about 60 bar, with which a control pressure circuit 10 is fed.

The hydraulic consumer V can be connected to at least P, R via working lines A, B and a three-position-way proportional slide W (4/3 slide valve). The directional slide W has two proportional magnets 4, 6, each of which actuate a pressure feedforward control 5, 6 for adjusting a piston slide between three control positions or from a neutral position into two control positions and against the force of a spring arrangement fixing the piston slide in the middle neutral position. In the pressure feedforward controls 5, 7, for example, pressure reducing valves (not shown) are included, which set in accordance with the energization of the respective proportional solenoid 4, 6 on the spool a certain control pressure, which is regulated for example between 0 and about 60 bar. The control pressure acting on the piston slide can be lower than that of the control pressure supply Z even at maximum current supply. The pressure pilot controls 5, 7 are connected via a control line 8 to the control pressure supply.

From taps of Druckvorsteuerungen 5, 7 on directional slide W lead two control lines 1, 2 to a hydraulic And logic element L in the control pressure circuit 10. To And logic element L leads from the control pressure supply Z a control line 9. Between the pump line P and the directional slide W can , Preferably, for the purpose of load independence, a feed regulator 3 may be provided. In each working line A, B, a load-holding valve 11 and 12 is arranged, which is bypassable in the flow direction to the hydraulic consumer V by a check valve 13 and 14 respectively. Each load-holding valve 11, 12 is pressure-controlled upstream and downstream, acted upon by a spring 35 in the reverse direction, and connected to the control pressure circuit 10 at a control side 47 and 48, respectively.

From each working line A, B leads between the load-holding valve 11, 12 and the directional slide W a control line 15 and 16 to a shuttle valve 17 and 18, from which control lines 19 and 20 lead to the Aufsteuerseiten 47, 48. To the shuttle valves 17, 18 control lines 23, 24 are further connected, which are connected together via a control line 25 to the logic element L and in which a pilot-operated check valve 26 is included. Further, a pressure relief D is provided, which includes a leading to the tank R control line 21, 22 respectively to the control lines 15, 16 and a discharge line 49 to or from the and-logic element L.

In the control lines 19, 20, 15, 16 and 21, 22 each nozzle can be arranged.

In the in Fig. 1 shown embodiment, a mechanical limit 27 for the maximum Aufsteuerquerschnitt the load-holding valve is incorporated in each load-holding valve 11, 12, for example, based on Fig. 2 will be explained.

Instead of in the load-holding valves 11, 12 directly integrated mechanical limitations 27 could be arranged in separate loops Senkbremsventile, biasing valves or damping valves that limit a maximum flow rate and thus adjustment of the hydraulic consumer V user-specific, as well as the mechanical limit 27 in Fig. 1 accomplished.

By means of the directional slide W, the hydraulic consumer V is controllable in both directions of movement with adjustable speed. For this purpose, either the proportional solenoid 4 or the proportional solenoid 6 is energized. The movement speed is proportional to the current supply. To the hydraulic consumer V in Fig. 1 For example, to adjust to the right, the proportional solenoid 6 is energized, via the pressure feedforward 7, the spool up from the in Fig. 1 adjusted neutral position, so that the working line A with P and the working line B is connected to R. About the opening check valve 13, the left admission space of the hydraulic consumer V is pressurized. From the pressure in the working line A is via the control line 15, the shuttle valve 17, which then locks to the control line 23, and the control line 19 control pressure to the control side 48 of the load-holding valve 12 in the working line B, which opens the load-holding valve 12, so that despite the blocking check valve 14 pressure medium from the right Beaufschlagungskammer the hydraulic consumer V is pushed out through the working line 13 and drained via the directional slide W to the tank R. At the same time, the control pressure applied via the proportional magnet 6 is brought via the control line 1 to the logic element L, while the control line 2 remains unpressurized. Since it is an AND logic element L, the pressure-dependent only responds, if both control lines 1, 2 at the same time and approximately the same control pressures, the AND logic element L does not respond.

The direction control of the hydraulic consumer V in FIG. 1 to the left is effected by energizing the other proportional magnet 4, so that the load-holding valve 11 is opened by control pressure in the control line 16 tapped off from the working line B. Again, the AND logic element L does not respond, because then only the control line 2 control pressure leads, while the control line 1 is depressurized.

In order to stop and hydraulically block the hydraulic consumer V, none of the proportional magnets 4, 6 is energized, so that the piston valve assumes the neutral position shown, in which the working lines A, B downstream of the load-holding valves 11, 12 are connected to the tank R (open neutral position), and the working pressures of the hydraulic consumer V of the standing in their blocking positions load-holding valves 11, 12 and the check valves 13, 14 are held. The load-holding valves 11, 12 are therefore in their blocking positions because the Aufsteuerseiten 47, 48 are relieved of pressure via the control lines and the discharge line 49 to the tank R (is based Fig. 4 illustrated).

The hydraulic control H of Fig. 1 (and Fig. 3 ) is used, for example, in a piste grooming vehicle, a winter utility vehicle, an agricultural vehicle, or the like, to adjust, for example, by means of the hydraulic consumer V an attachment such as a shield, a roller, a plow, or the like. In certain operating conditions, a floating position is required for the hydraulic consumer V or the implement operated by it, ie, both admission chambers of the hydraulic consumer V are to be connected to the tank R. Although the hydraulic control H contains only a three-position directional slide W, this fourth position is still adjustable as a floating position on the open neutral position by both load-holding valves 11, 12 are turned on. This is done by the and logic element L.

In order to set the floating position, both proportional magnets 4, 6 are energized simultaneously and at least approximately equal, for example with at most half maximum current intensity or less, so that in both control lines 1, 2 control pressure is present, which is lower than the control pressure of the control pressure supply Z, For example, in the control line 9. Only at the same time and in about the same control pressure signals in the control lines 1, 2 adds the And logic element L this control pressure signals and unlocks the check valve 26 so that the control pressure from the control line 9 from the logic element L on the Control line 25, the control lines 23, 24, which then switching switching shuttle valves 17, 18 and the control lines 19, 20 is brought to the Aufsteuerseiten 47, 48, and the load-holding valves 11, 12 aufsteuert (floating position).

Since the control pressure of the control pressure supply Z can be about the same as the direction control of the hydraulic consumer V from the working line A or B for controlling a load-holding valve 11 or 12 tapped control pressure in the lines 15 or 16, the load-holding valves 11, 12 at least largely fully open. However, since user-specific specifications may require limiting a particular cross-sectional size, the mechanical limitations 27 of the load-holding valves 11, 12 are preferably effective, as well as in the direction control of the hydraulic consumer. That is, the load-holding valves 11, 12 are only turned on as far as the limitations allow 27. there For example, the limits 27 on the load-holding valves 11, 12 can be set the same or different.

If the floating position abandoned, for example, to make a hydraulic blockage of the hydraulic consumer V again or to initiate a directional control (to the left or to the right), then the control pressures on both Aufsteuerseiten 47, 48 or only on a control side via the control lines and the discharge line 49 of Pressure relief D to tank R relieved.

Fig. 2 shows in section an embodiment of a load-holding valve 11 (12) with, optionally, integrated mechanical limit 27, as symbolically in FIG Fig. 1 indicated. The load-holding valve 11 (12) has a valve cone 28, which here has a conical sealing surface 29 for cooperation with a seat 30 in a ring insert 33. The ring insert is penetrated by axial bores 32, which are part of the check valve 13 (14), which is equipped with a spring-loaded lock plate 31. The seat 30 is disposed in the working line A or B between the side of the hydraulic consumer V and the side of the pump / tank assembly P, R. With the valve plug 28, a spring abutment 34 cooperates, which is acted upon by the spring 35 and presses the valve plug 28 in the shut-off position shown. The bias of the spring 35 is adjusted for example by a replaceable insert 36. Alternatively, a screw-adjustable spring abutment (not shown) could be provided here.

The integrated into the load-holding valve 11 (12) mechanical limit 27 comprises a lock nut 40 securable bolt 38 which forms a stop 39 for the spring abutment 34 with its end and limits the opening stroke or opening cross-section of the valve plug 28 in the seat 30. The stop can thus be adjusted from the outside. Alternatively, a built-in disk or the like could serve as a stop 39.

In the Fig. 3 shown embodiment of the hydraulic control H differs from that of Fig. 1 in just a few details, which will be discussed below. The load-holding valves 11, 12 are in Fig. 3 , optionally, designed without mechanical limitations 27. Further lead from the control lines 23 and 24 control lines 43 and 44 to the tank in which nozzles 45, 46 are included. Furthermore, between the control line 25 and the branches of the control lines 43, 44 of the control lines 23, 24 nozzles 41 and 42 are used. These nozzle arrangements serve to modulate the control pressure provided by the logic element L from the line 9 from the control pressure supply Z on the way to the control sides 47, 48 of the load-holding valves 11, 12, ie to reduce it either equally or unequally, so that the Aufsteuerseiten 47, 48 either equal but lower control pressures than that of the control pressure supply Z provided control pressure act, or unequal control pressures lower than the control pressure provided by the control pressure Z control pressure. In this way, the maximum Aufsteuerquerschnitt each load-holding valve 11, 12 can be adjusted individually to user-specific requirements, so that neither a mechanical limit 27 as in Fig. 1 is required, additional additional counterbalance valves or bias valves or throttle valves. The nozzles shown in the control lines 15, 16 and 21, 22 in Fig. 3 (as well as in Fig. 1 ) also adjust the tapped from the respective working line A or B control pressure for the other control side 47 or 48 accordingly, so that even in the direction control of the hydraulic consumer, the respective load-holding valve 11, 12 is opened only as far as it meets user-specific requirements.

The other functions of the hydraulic control H in Fig. 3 match the basis Fig. 1 described. The floating position is also adjusted by simultaneous moderate energizing both proportional magnets 4, 6 of the three-position-way proportional directional slide W with the participation of the and logic element L.

Fig. 4 shows an embodiment of the And logic element L, the example in the hydraulic controls H of Fig. 1 and 3 is usable, but also in other hydraulic controls, to provide there a safety aspect such that only in the presence of two simultaneous pressure signals with approximately the same pressure values, a pressure transmission path for another possibly higher pressure is released.

The and-logic element L in Fig. 4 is designed as Einschraubventil and screwed into a block 52 in a first control pressure chamber 53, which is closed by a screw plug 55. To the first control pressure chamber 53, the control line 1 (see Fig. 1 and 3 ) connected. In the first control pressure chamber 53, an actuating piston 54 is sealingly displaceable via a stroke X limited by a valve insert 60 (slide fitting). The one actuating piston 54 is designed as a pot piston and contains in the interior in a second control pressure chamber 57, a further actuating piston 56 (eg, a solid piston), which is axially adjustable only over a Leerhub Y due to a arranged in an actuating piston 54 coupling 66 (eg a locking ring) , The second control pressure chamber 57 is connected through the wall of the one actuating piston 54 between the bottom of the one actuating piston 54 and the further actuating piston 56 to the control line 2 (FIG. Fig. 1 and 3 ) connected.

In the lower end of the bore in the block 52 is the check valve 26, which can be unlocked, for example, by a displaceable in the valve insert 60 plunger 58. The ram 58 becomes acted upon by a spring 59 in the reverse direction of the check valve 26 and faces the underside of the further actuating piston 56. The one actuating piston 54, for example, by a return spring 62 for in Fig. 4 shown exposed position.

In the and-logic element L in Fig. 4 is incorporated as an option a 2/2-way slider function F, which is part of the basis of the Fig. 1 and 3 explained pressure relief D is. Below the valve insert 60, the control line 9 is connected to the control pressure supply Z, while the space containing the spring 59 is connected to the line 25 to the control pressure circuit 10. From the line 25 branches off the discharge line 49, which leads to an opening provided in the first control pressure chamber 53 above the valve insert 60 annular space, is connected to the via a channel 61 in the valve insert 60 of the tank R.

To form the slide function F, the lower end of the further actuating piston 54 has a slide end 64, and below the annular space to which the discharge line 49 leads, a slide bore section 65 is provided whose inner diameter corresponds approximately to the outer diameter of the slide end 64.

Function of the and-logic element:

If none of the control lines 1, 2 control pressure, take the actuating piston 54, 56, for example, in Fig. 4 drawn layers. The check valve 26 is in the blocking position. The control lines 25 and the discharge line 49 are depressurized to the tank R.

If the control line 1 is acted upon by control pressure, then the one actuating piston 54 moves downwards over its stroke X until it optionally engages on an elastic sealing ring 63 arranged in the valve insert 60. Since the control line 2 carries no control pressure, the other actuating piston 56 remains passive, so that the plunger 58 is not acted upon. Does the control line 2 control pressure, however, the control line 1 no control pressure, then moves the other actuating piston 56 via its idle stroke Y up against the coupling 66 at which it is intercepted. The one actuating piston 54 remains in the in Fig. 4 shown position so that the plunger 58 is not acted upon. The check valve 26 holds its blocking position.

However, if both control lines 1, 2 at the same time (or optionally with a slight time offset), for example by simultaneous energization of the two proportional magnets 4, 6 in the Fig. 1 and 3 are subjected to control pressure, then drives an actuating piston 54 via its stroke X down to rest on the sealing ring 63, and moves the other actuating piston 56 via its idle stroke Y until it rests against the coupling 60th

The actuating forces exerted by the two actuating pistons 54, 56 add up and displace the plunger 58 downwards, so that the check valve 26 is hydraulically unlocked and feeds the control pressure from the control line 9 into the control line 25. By the slider function F then the discharge line 49 is separated from the tank R, since the slider end 64 is retracted into the slide bore portion 65 and shut off. This way, in the Fig. 1 and 3 set the floating position.

Once the control pressure in the control line 1 or 2 or the control pressures in the control lines 1 and 2 are reduced (both proportional solenoid 4, 6 de-energized), the spring 59 pushes the plunger 58 back up to stop, so that the check valve 26 assumes its blocking position , Pilot pressure residues in the first and second control pressure chambers 53, 57 are exhausted to the tank R via the spool fittings while the spool end 64 is pulled out of the spool bore portion 65 and also connects the relief spool 49 to the tank R, so that the control pressure circuit 10 is depressurized ,

The in the and logic element L of Fig. 4 integrated slider function F is only an option. In its place, it would be conceivable, as in Fig. 4 indicated by dashed lines, from the spring 59 containing space to provide a control line 49 'to the tank R, in which a nozzle 50 and / or a discharge switching valve 51 is included or are. If only the nozzle 50 is provided, although a low leakage current will occur permanently when the check valve 26 is unlocked. This leakage current is negligible, but serves to relieve the pressure. If the relief switching valve 51 is provided, it must be actuated to allow the pressure relief to take effect. The nozzle 50 could be provided in the latter case as flanking damping measure.

According to the invention, to open the load holding valves 11, 12 at least when adjusting the floating position on the control sides 47, 48 of the load holding valves 11, 12 control pressures up to about 60 bar, as provided by the control pressure supply Z, although the control pressure signals in the control lines 1, 2 can be weaker, eg only 20 to 40 bar to exclude heating problems of the proportional solenoid 4, 6 at a longer duration of the floating position. The proportional solenoids 4, 6 are used, so to speak, only to simultaneously apply two control pressure signals in the control lines 1, 2 with a relatively moderate height to make the AND logic element L to respond and to unlock the check valve 26, thus the higher control pressure from the control pressure supply Z for controlling the load-holding valves 11, 12 is usable.

Claims (13)

1. A hydraulic controller (H) with a double-acting hydraulic load (V) and a three position proportional directional slide valve (W) between a pressure source/tank arrangement (PR) and working lines (A, B) which include actuable load holding valves, from a control pressure circuit (10), which is connected to a control pressure supply (Z), wherein a floating position of the hydraulic load (V) may be set with actuated load holding valves by simultaneous and equal energising of two proportional magnets (4, 6) of the three position proportional directional slide valve (W), characterised in that provided in the control pressure circuit (10) there is a pressure dependently responsive hydraulic AND logic element, which enables connections (19, 20, 23, 24, 25) between the control pressure supply (2) and actuation sides (47, 48) of the load holding valves (11, 12) exclusively in the set floating position.
2. A hydraulic controller as claimed in Claim 1, characterised in that equal control pressures are settable via the connections at the actuation sides (47, 48) of the two load holding valves (11, 12) for the enabling.
3. A hydraulic controller as claimed in Claim 1, characterised in that unequal control pressures are settable via the connections at the actuation sides (47, 48) for the enabling.
4. A hydraulic controller as claimed in Claim 1, characterised in that associated with the logic element (L) there is a pressure relief (D), which includes a relief line (49, 49') to the tank (R), at least for the connections to the actuation sides (47, 48).
5. A hydraulic controller as claimed in Claim 4, characterised in that the pressure relief (D) is integrated into the logic element (L), preferably with a slide valve function (F) monitoring the relief line (49).
6. A hydraulic controller as claimed in Claim 4 or 5, characterised in that the pressure relief (D) includes a nozzle (50) and/or a relief switching valve (51) in the relief line (49').
7. A hydraulic controller as claimed in at least one of the preceding claims, characterised in that integrated into each load holding valve (11, 12) there is an application specific and mechanical limit (27) of an actuation cross-section, preferably a screw adjustable or replaceably installed limiting stop (39).
8. A hydraulic controller as claimed in Claim 1, characterised in that the AND logic element (L) includes a hydraulically unlockable non-return valve (26) and two actuating pistons (54, 56) connected in series for the non-return valve (26), each of which may be acted on by one of two control pressures from one of two control lines (1, 2) and that the non-return valve (26) is unlockable only when at least approximately equal control pressures are present simultaneously in the control lines (1, 2).
9. A hydraulic controller as claimed in Claim 8, characterised in that an unlocking rod (58) of the non-return valve (26) is loaded by spring force (59) in the closing direction of the non-return valve (26) and that provided between the actuating pistons (54, 56) there is a coupling (66), which limits a relative idle stroke (Y).
10. A hydraulic controller as claimed in Claim 9, characterised in that the one actuating piston (54) is preferably a tube piston movable over a limited stroke (X) in a first control pressure chamber (53), which axially movably receives the other actuating piston (56), which is preferably constructed in the form of a solid piston, in a second control pressure chamber (57) and contains the coupling (66) and that the unlocking rod (58) is actuable by the other actuating piston (56).
11. A hydraulic controller as claimed in Claim 10, characterised in that the first control pressure chamber (53) includes a slider bore section (65), which is preferably restricted by a sealing ring (63), for one slider end (64) of the one actuating piston (54) for a 2/2-way slider function (F), integrated into the logic element (L), of the one actuating piston (54), that connected to the slider bore section (65) there are a tank (R) and a relief line (49), which is connected to the non-return valve (26), and that the relief line (49) and the tank (R) are selectively connectable and separable by means of the 2/2-way slider function (F).
12. A hydraulic controller as claimed in Claim 8, characterised in that the non-return valve (26) is actuated on in the blocking direction with control pressure from a control pressure supply (Z) and as soon as it is unlocked via both actuating pistons (54, 56) it connects the control pressure supply (Z) with at least one control line (25) to a pressure dependently actuable valve (11, 12), preferably a load holding valve actuable against spring force (35).
13. A hydraulic controller as claimed in Claim 8, characterised in that the AND logic element (L) is constructed in the form of a screw-in valve.

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