EP0027854A1 - Electrohydraulic control - Google Patents

Abstract

In the case of an electrohydraulic control system which has interconnected magnetic control plates (1) and at least one connection plate (2), optionally with a pressure relief valve for the pump (P) and tank or return connection (R), it is proposed that all plates (1, 2) are clamped together directly using clamping screws (3), the through holes (9) for the clamping screws (3) and the through channels (10, 11) for a pressure connection (P) that can be connected to the pump connection and the tank connection or return (R ) are arranged symmetrically to a plane of symmetry (8) in the plates (1 and 2). Due to this symmetrical arrangement of the through channels (10, 11) and the through holes (9) for the clamping screws (3), the individual plates (1, 2) can be arranged in any two positions in the block of the electro-hydraulic control, so that the necessary connections the optimal connection positions can be selected and the direction of the connections can also be adapted to different installation conditions.

Description

The invention relates to an electro-hydraulic control system which has interconnected magnetic control plates and at least one connection plate, optionally with a pressure relief valve for the pump and tank connection.

In a known such control, the magnetic control plates are mounted on a connection plate on which the consumer connections A and B are provided, while the common pump and tank connection is optionally provided on one of the two end plates provided screwed to the magnetic control plates. The connection plate is intended for a certain number of magnetic control plates and, if the control system needs to be expanded, a larger connection plate must be provided if such a connection plate has not been previously planned with corresponding, closed connections. All connections are fixed and can hardly be varied.

The object of the present invention is to improve a control of the type mentioned at the outset in such a way that an expansion or change is possible with little effort and that in particular the direction of the connections can be adapted to different installation conditions.

To achieve this object, the invention provides that all the plate are clamped directly to one another via clamping screws and that the through holes for the clamping screws and the through channels for the the pump connection connectable pressure connection and the tank connection or return are arranged symmetrically to a central plane in the plates.

Due to the symmetrical design to the central level, the individual panels can be turned through 180 ° depending on the requirements of the connections. If more plates are to be used, correspondingly more plates can be joined together in a simple manner by using longer clamping screws.

Since the pressure connection and return line are flush through all plates, no special measures need to be taken to connect further plates. Only the consumers have to be connected to the corresponding connections of the added plates and the necessary electrical control lines for the magnetic control.

The through-channel for the pressure connection can be located particularly advantageously in the central plane, as a result of which a secure and simple seal between the individual plates is possible. Furthermore, two through channels for the tank connection or return can then be provided symmetrically to the central plane. The required connection channels can be special be short and streamlined.

Furthermore, particularly advantageously, the plates in the area of the through-channels and the through-holes for the tensioning screws can have special sealing surfaces or contact surfaces, and the plates are otherwise formed apart from these sealing and contact surfaces, in order to thus provide flow-through possibilities for cooling air between the individual plates. As a result, the entire control system can also be used for heat emission for cooling the pressure medium.

In the case of a control system with at least one plate with a control spool that can be displaced against the action of at least one spring, at least one pilot-operated control spool can be displaceably guided in a bore in each plate for particularly simple machining, this bore being guided through the entire housing perpendicular to the central plane and is closed on both sides by screw plugs, these screw plugs also serving as end stops for the control slide; As a result, few individual parts and only a small amount of processing work for the plate are required.

A particularly low-noise and energy-saving operation can be made possible by the fact that a pressure relief valve pilot-controlled via a first auxiliary valve is provided in the connection plate and that a reversing valve pilot-controlled via an electromagnet and a second auxiliary valve is further provided, the pressure-limiting valve and the reversing valve having a common control slide . In addition to a space-saving design, many individual parts are also saved here and the manufacturing costs are kept low. The pressure relief valve limits the maximum pressure to the set value and the reversing valve connects the pump connection directly to the return line when no consumers are switched on. In addition to reducing energy consumption, this also means that the pressure medium is heated much less due to the lower throttling required.

One end of the control slide is advantageously connected to the pump connection and the other end can be connected via the two auxiliary valves to the passage channel connected to the tank connection or return. The individual connecting channels can thus be made particularly short and streamlined. The two auxiliary valves are spring-loaded check valves, preferably ball valves, which are particularly inexpensive to manufacture. The preload of the compression spring of the first auxiliary valve can be adjusted from the outside to adjust the maximum pressure.

One or both of the auxiliary valves is expediently arranged in an easily replaceable banjo bolt, in one end of which a valve seat is provided. To avoid hard knocks when closing the auxiliary valves, the valve body, preferably a ball, is guided so as to be displaceable in the axial direction. When hitting the valve seat, the pressure medium dampens the touchdown movement. At the same time, this significantly reduces wear and noise emissions.

To protect the springs, the stroke of the valve body is limited by a stop, the radial guidance of the valve body still being provided when this stop is reached. The radial guide can advantageously be formed by a cylindrical wall having radial slots. The radial slots can be used for screw fastening of the valve seat, but also for the flow of the pressure medium. The sealing surface of the valve seat can be produced particularly inexpensively by simple stamping with the exception of surface hardening or hardening without any other processing.

The valve seat can simply be held in a shoulder at the end of the bore by flanging the hollow screw end.

In order to allow machining inaccuracies and misalignments without influencing the functionality, an actuating pin for the valve body can advantageously be guided axially displaceably in the valve seat. This practically prevents tilting and jamming of the valve body and valve actuation. The length of the actuating pin is expediently dimensioned such that when the actuating pin is pressed down flush with the valve seat, the valve body is located shortly before it stops. This opens the valve fully, but the actuating force cannot overstress the valve spring.

In a particularly simple manner, the hollow screw can have a cutting edge which cooperates in a sealing manner with a sealing surface of the plate, at least the cutting edge being made harder than the sealing surface, and so on to avoid special sealing rings or other sealing measures.

To easily achieve the pilot control of the control spool with a neutral central position and two end positions, both end faces of the same can be advantageously connected via a throttle via a through-channel in the control spool with the through-channel connected to the pump connection. Via the control slide, the channels connected to the pump connection and the tank connection or return can be connected and disconnected, and a preliminary throttle is advantageously provided to initiate the connection, which can be formed by at least one transverse bore in the slide in order to smooth the switching process with initiate as little noise as possible.

To reduce the risk of accidents in the event of a pressure failure, a magnetic control plate with a control slide that is displaceably guided by hydraulic pressure can have its front face connected to a connection A or B via an unlockable check valve, one of the check valves being connected by the hydraulic pressure and the other by means of a from the control piston to the Valve body of the check valve acting plunger is openable.

To achieve short connection paths, the two end faces of the control slide, which can be moved by hydraulic pressure, can be connected to the pressure connection via a throttle in each case with a magnetic control plate, and the two end faces can each be connected to the return via a controllable check valve. The check valves themselves can be opened via a solenoid against the action of a spring in order to achieve the desired reversal. In order to also overcome a certain stiffness of the control slide in the event of contamination that may occur and to achieve an exact central position, the control slide can advantageously be held between two prestressed compression springs, the effect of these compression springs being limited in each case to the stroke range on the compression spring side up to the central position.

Particularly structurally simple, an end-side receiving opening for a stop receiving one end of the compression spring can be arranged symmetrically to limit the action of the compression springs in the control slide bushing is provided, the projecting edge in the central position of the control slide, possibly with a little play on the end face of the control slide and on the edge of the bore of the plate, with the end of the stop sleeve opposite the projecting edge supporting the compression spring abutting approximately at the bottom of the receiving opening and at a displacement of the control slide in the direction of the compression spring, the stop sleeve can be lifted off the edge of the bore by the control slide and comes into contact with the locking screw during the ^% iaximal stroke.

To reduce the risk of contamination from contamination, the two throttles provided in the control slide can advantageously be connected to an external recess in the control slide via at least one transverse bore, and a sieve can also be provided on two shoulders of the recess on the entire circumference of the recess. This strainer can be used to prevent contamination of the chokes. The pressure medium flowing through the through-channel takes with it the dirt accumulating on the sieve, so that self-cleaning occurs due to the special design. The control valve also rotates slowly, so that a safe switching function is guaranteed.

At least five ring channels are provided symmetrically to the center plane in the bore receiving the control slide valve, the outer two ring channels with the through channels connected to the tank connection or return and the middle ring channel with the pressure channel and the two intermediate ring channels via hydraulically unlockable check valves with consumer connections A or B connected, furthermore the control slide has two grooves assigned to the ring channels. The ring channels can be cast directly into the plate, so that only the through hole for the control slide has to be machined for machining. A processing of the edges of the ring channels is not necessary, since the chosen construction leaves a certain positional inaccuracy due to tolerances without influence on the functionality, whereby the achievable casting accuracies are completely sufficient.

Correspondingly, the two unlockable check valves are arranged symmetrically in a stepped bore and are separated from one another by a control piston which may unlock one of the two check valves, one end face of the control piston with one of the intermediate valves Ring channels is connected.

In particular in order to reduce the required machining accuracy and as little surface processing effort as possible, the check valve is formed by a tappet carrier having the valve seat and a spring-loaded valve body, preferably a ball, and the valve body is displaceably guided by axial guide surfaces through a likewise axially displaceable tappet. Due to the axial guidance of the valve body, the valve body is positioned precisely and dampened by the pressure medium layer on its valve seat, wear and noise emission are particularly low. Due to the actuation of the tappet, misalignments during processing remain unaffected by easy movement.

Surface hardening and very precise surface processing are not necessary if the tappet carrier is inserted tightly in the stepped bore and a hard-formed sealing surface of the tappet carrier interacts with a softer sealing edge of the offset bore. Special seals are then not required.

With little manufacturing effort, the stepped bore can be closed by screw plugs, the screw plug serving as an abutment for the spring of the associated check valve and at the same time as a stroke limiter for its valve body, in order to avoid spring overstressing. Likewise, the tappet carrier can also serve as a stop for the control piston.

In order to ensure that when a consumer is switched on, the required pressure is also present, the connections of all consumers of the control plates are each connected via at least one diode to the magnet connection of the magnet of the connection plate, whereby the pressure reduction to a low pressure when a switching function is initiated is safely canceled and the required pressure is immediately produced by the switching valve of the connecting plate and the practically unpressurized return of the pressure medium to the return line is prevented.

• Fig. 1 eine Seitenansicht einer elektrohydraulischen Steuerung mit einer Anschlußplatte.und fünf Magnetsteuerplatten, die zu einer Baueinheit zusammengeschraubt sind,
• Fig. 2 einen Schnitt durch die Anschlußplatte gemäß der Linie II-II in Fig. 1 in Neutralstellung,
• Fig. 3 einen Schnitt durch eine Magnetsteuerplatte gemäß der Linie III-III in Fig. 1, ebenfalls in Neutralstellung,
• Fig. 4 eine Seitenansicht einer Magnetsteuerplatte entsprechend der Linie IV-IV in Fig. 1 und
• Fig. 5a und b einen Schnitt durch eine Anschlußplatte und eine Magnetsteuerplatte in "Hebestellung" für das Ausfahren eines Arbeitszylinders; teilweise schematisch.

Further designs according to the invention can be found in the subclaims and their advantages are explained in more detail in the description below. In the accompanying drawings:

• 1 is a side view of an electrohydraulic control with a connecting plate and five magnetic control plates which are screwed together to form a structural unit,
• 2 shows a section through the connection plate along the line II-II in FIG. 1 in the neutral position,
• 3 shows a section through a magnetic control plate along the line III-III in FIG. 1, also in the neutral position,
• Fig. 4 is a side view of a magnetic control plate along the line IV-IV in Fig. 1 and
• 5a and b show a section through a connecting plate and a magnetic control plate in the "lifting position" for the extension of a working cylinder; partly schematic.

The same reference numerals are used for all corresponding parts in the following description. In the electrohydraulic control system shown in FIG. 1, five are practically identical Magnetic control plates 1 clamped together with a connecting plate 2 via three clamping screws 3. As can be seen in connection with FIGS. 2 and 3, two electromagnets 4, 4 'are placed on each of the magnetic control plates and an electromagnet 5 is placed on the connecting plate 2, which can be switched via corresponding lines and switches.

The connection plate 2 is connected with its pressure connection P to a hydraulic unit, a pump 6, while a tank connection or return line R is connected to a tank 7, as is indicated schematically in FIGS. 5a and b.

The clamping screws 3 are passed through through holes 9 arranged symmetrically to a central plane 8, of which the lower through hole 9 lies in the plane of symmetry and the upper two through holes 9 are arranged at a distance therefrom. Three through-channels 10 and 11 are arranged parallel to these through-holes, of which the through-channel 11 is arranged symmetrically at a distance from it in the plane of symmetry 8 and the other two through-channels 10. The through-channel 11 is connected to the pressure connection P, while the through-channels 10 are connected to one another and to the return line R and also to an annular channel 12 and another Ring channel 13 are connected. Finally, there is also a connection to the return R to a second auxiliary valve 14 which can be actuated by the electromagnet 5. The second auxiliary valve 14 arranged between the electromagnet 5 and an annular channel 15 has a hollow screw 16, into which a valve seat 17 is screwed in at the top and on which opposite side, a spring support 18 is crimped. The spring support 18 has through openings 19 and it is mushroom-shaped, the part guiding the compression spring 20 also serving as a stop for the valve body 21 designed as a ball.

The valve seat 17 has a stepped bore in which the valve body 21, which is designed as a ball, is guided axially displaceably and, with a smaller diameter, a plunger-like actuating pin 22 is also provided, which can be displaced by the electromagnet 5 against the valve body 21. The length of the actuating pin 22 is dimensioned such that when the actuating rod of the solenoid valve 5 is placed on the valve seat, the valve body 21 does not yet abut the spring support 18, by which the stroke of the valve body 21 is limited. To insert one Tool and for the flow of the pressure medium 17 radial slots 23 are provided on the valve seat and the pressure medium can flow through transverse bores 24 through the valve seat 17 and the banjo bolt 16.

The second auxiliary valve 14 is arranged in a stepped bore 25, which is also penetrating the annular channel 15 down through the connecting plate 2. A first auxiliary valve 26 is screwed in from below and also has a hollow screw 27. Here, too, a valve seat 28 is crimped at one end of the hollow screw 27, while on the other opposite side a set screw 29 is used to adjust the spring preload of the spring 30 and is countered and sealed by a cap nut.

The first auxiliary valve 26 also has an axially displaceably guided ball as the valve body 31, the radial guide 32 of the valve body 31 being formed by a cylindrical wall interrupted by radial slots 33.

The interior of the hollow screw 27 is connected by a connecting channel 34 to the ring channel 12, which in turn is sealed against the ring channel 15 by a seal 35.

In a bore 36 running through the entire connecting plate 2 and perpendicular to the plane of symmetry 8, a control slide 37 is guided, through which the ring channels 12 and 13 can be separated or connected. The bore 36 for the control slide 37 is closed by two locking screws 38, 39, these locking screws 38, 39 also serve as a stroke limit stop for the control slide 37. The control slide 37 and the locking screw 38 have cutouts for a compression spring 40. Furthermore, a throttle 41 is provided in the control slide 37, a commercially available carburetor nozzle, through which the end faces of the control slide 37 are connected to one another.

Opposite the compression spring 40, the control slide 37 has two transverse bores 42, 43 which are arranged in such a way that the channels 12 and 13 are connected when the control slide 37 is in a central position and against the locking screw when it is displaced 39 are separated from each other. A small pre-throttle 44 is also provided parallel to the transverse bore 42, through which a softer switching can be achieved. The screw plug 39 also serves as a pressure connection P.

• Bei der in Fig. 2 dargestellten Neutralstellung des Steuerschiebers 37 kann Drucköl vom Druckanschluß P zum Rücklauf R fließen, da über den Elektromagneten 5 das zweite Hilfsventil 14 geöffnet und damit der Ringkanal 15 drucklos ist. Das Druckmedium kann daher ohne wesentliche Drosselung zum Rücklauf R fließen.

The functioning of the connection plate 2 is now as follows:

• In the neutral position of the control slide 37 shown in FIG. 2, pressure oil can flow from the pressure connection P to the return R, since the second auxiliary valve 14 is opened via the electromagnet 5 and the annular channel 15 is therefore depressurized. The pressure medium can therefore flow to the return R without substantial throttling.

If, as shown in FIG. 5 a, the second auxiliary valve 14 is closed, the pressure in the annular channel 15 increases and the control slide 37 moves to the left, so that the pressure medium to the through-channel 11 via the pressure connection P and the transverse bores 42, 43 can flow. If only a little pressure medium is removed, the control slide 37 is shifted somewhat to the right by a further pressure increase, but pressure is produced by the throttle 41 equalization so that the pressure continues to rise until finally the first auxiliary valve 26 opens and pressure medium can flow out via the connecting channel 34 to the return. The control slide 37 thus moves further to the right, so that pressure medium can flow out to the return R and a pressure equilibrium occurs. The level of this working pressure can be adjusted by the bias of the spring 30 accessible from the outside. The first auxiliary valve 26 thus regulates the working pressure, while the second auxiliary valve 14 can be used to reduce the pressure via the control of the electromagnet 5 if no pressure medium is required, so as to save energy and to avoid unnecessary heating of the pressure medium by throttling.

In order to be able to dissipate the resulting heat as well as possible, the abutting sealing and contact surfaces 45 and 46 (FIG. 4) are limited to the areas of the through holes 9 and through channels 10 and 11, so that air for cooling between the individual plates Can flow through 1 and 2.

Due to the symmetrical arrangement of the through channels 10 and 11 and the through holes 9 with respect to the plane of symmetry 8, the magnetic control plates 1 and the connection plate 2 can be used rotated by 180 ° depending on the connection requirements.

The magnetic control plate shown in FIG. 3 is similarly provided with corresponding through holes 9 and through channels 10 and 11 in the construction of the connecting plate 2, so that the corresponding channels of the plates 1 and 2 are directly connected to one another. 8th

At right angles to the plane of symmetry, a control slide 48 is slidably guided in the magnetic control plate 1 in a bore 47. The bore 47 is closed on the end face by means of locking screws 49, 49 'serving as stops for the control slide 48. In the bore 47, seven ring channels 50, 50 ', 51, 51', 52, 52 'and 53 are provided, which are arranged symmetrically to the plane of symmetry 8. The middle ring channel 53 is connected to the through channel 11, the ring channels 51, 51 'with the through channels 10, which are also connected to the ring channels 50, 50' via controllable check valves 54, 54 ', while the two ring channels 52, 52 'each via a check valve 55 or 55' with a consumer connection A or B stay in contact.

The control slide 48 itself has three symmetrical annular grooves 56, 56 'and 57, the central annular groove 57 having a shoulder on both sides for a sieve 58. Pressure medium flowing into transverse bores 59 is cleaned through the sieve 58. The transverse bores 59 are each connected to the end faces of the control slide 48 via a throttle 60 or 60 '. Throttles 60, 60 'are also commercially available carburetor nozzles.

On the face side, receiving openings 61, 61 'for stop bushes 62, 62' are provided symmetrically in the control slide 48, the projecting edges 63, 63 'of which can rest against the edge of the bore 47 on the face side. The length of the stop sleeves 62,62 'corresponds approximately to the depth of the receiving openings 61,61' and it is held by means of prestressed compression springs 64,64 'of the control slide 48 in its central position, whereby it still has a slight play in its central position, so that through the pressure medium flowing through the passage 11 also rotates the control slide 48 and can thus keep the sieve 58 clean.

The check valves 54, 54 'which can be actuated via the electromagnets 4, 4' are of identical design to the second auxiliary valve 14 of the connecting plate 2, so that a more detailed description is unnecessary here. Correspondingly designed edges of the check valves 54, 54 'are screwed tightly into the magnetic control plate 1 without any further sealing measures.

The check valves 55, 55 'are also arranged in a stepped bore 65, which are closed by screw plugs 66, 66'. In the area of the plane of symmetry 8, a control piston 67 is axially displaceable in the bore 65, through which the check valves 55, 55 'can be actuated via plungers 68, 68'.

The check valves 55, 55 'are of identical design, they have a tappet carrier 69 which, in a stepped bore 70, has the tappet 68, on the other hand a valve seat 71 and a valve body in the form of a ball 72, which counteracts via a spring 73 the valve seat 71 is pressed.

The ball 72 is guided axially displaceably through the wall of the bore 70 and the pressure medium can flow out laterally via radial slots 74. The slots 74 also serve as an approach for a screw-in tool of the tappet carrier 69. The pressure medium can flow through the tappet carrier 69 through four connecting channels 75.

The valve seat 71 is produced by simple stamping with a ball without any further processing, with the exception of a final surface hardening. The axial guidance of the ball 72 results in a dampened placement on the valve seat 71 due to the necessary displacement of the last remaining pressure medium before it is placed on the valve seat 71, so that low-wear operation with low noise is possible.

In the neutral position shown in Fig. 3, the check valves 55, 55 'are closed, so that no pressure medium can reach or flow back to the consumer via the connections A and B. The controllable check valves 54 are also closed, so that the control slide 48 is held in its neutral central position by the prestressed compression springs 64.

If, as shown in FIG. 5b, the electromagnet 4 is energized, then the non-return valve 54 'can now open pressure medium from the ring channel 50' to the through channel 10, either without pressure or has only a low back pressure. As a result, the control slide 48 is displaced to the right by the pressure medium flowing via the through-channel 11 via the transverse bores 59 and the nozzle 60 to the annular channel 50, as is shown in FIG. 5b. The ring channels 52 and 53 and also the ring channels 52 'and 51' are thus connected to one another, the ball 72 of the check valve 55 being lifted off via the increasing pressure in the ring channel 52, and pressure medium can flow to the consumer port A. Due to the pressure of this pressure medium, the control piston 67 is shifted to the right and the plunger 68 'also opens the ball 72' of the check valve 55 ', so that pressure medium via the consumer connection B via the ring channels 52', 51 'to the right through channel 10 can flow off. If the electromagnet 4 is switched off, the pressure in the ring channel 50 ′ rises again and the control slide 48 will return to its central position, as a result of which the check valves 55 also close again and thus lock the consumer connections A and B again.

By closing one or both of the consumer connections A, B arranged below and arranging corresponding screw plugs 66 and 66 'with an axial one Possibility of connection, these connections can be varied depending on the requirements and the magnetic control plates 1 themselves can also be rotated through 180 ° without anything changing in the function of the control.

In order to reliably prevent the working cylinder 76 indicated in FIG. 5b from creeping if any leakage currents should occur, bevels 77 are provided on the control slide 48, by means of which the full desired switching function is ensured even if the control slide 48 gets stuck slightly.

By simply closing one of the consumer connections A or B, the magnetic control plate 1 can also be used for consumers which are only loaded on one side.

The electro-hydraulic control according to the invention is mainly used in the mobile sector in agricultural machinery, construction machinery, transport vehicles, in particular forklift trucks, but the control can also be used in a variety of ways in the stationary sector.

Claims (50)

1. Electro-hydraulic control, the interconnected magnetic control plates (1) and at least one connection plate (2) optionally with a pressure relief valve for the pump (P) and tank (R) or return connection, characterized in that all plates (1, 2) are clamped directly to one another via clamping screws (3) and that the through holes (9) for the clamping screws (3) and the through channels (10, 11) for a pressure connection P which can be connected to the pump connection and the tank connection or return line R are symmetrical to one Plane of symmetry (8) are arranged in the plates (1, 2). 2. Control according to claim 1, characterized in that the through-channel (11) for the pressure connection P lies in the plane of symmetry (8) and that symmetrically to the plane of symmetry (8) two through-channels (10) are provided for the tank connection or return R. 3. Control according to claim 1 or 2, characterized in that the plates (1,2) in the region of the through channels (10,11) and the through holes (9) for the clamping screws (3) special sealing surfaces (45) and contact surfaces (46 ) have and that the Plates (1, 2) are separated from these sealing surfaces (45) and contact surfaces (46). 4. Control according to claim 3, characterized in that three through channels (10, 11) and two through holes (9) in the region of a sealing surface (45) and at a distance therefrom a through hole (9) enclosed by a contact surface (46) are provided. 5. Control according to claim 3 or 4, characterized in that the through-channels (10, 11) lie between the through-holes (9). 6. Control according to one of claims 1 to 5 with at least one plate and a spool displaceable against the action of at least one spring, characterized in that in each plate (1,2) at least one pilot-operated spool (37,48) in a bore ( 36, 47) is displaceably guided and that this bore (36, 47) runs perpendicular to the plane of symmetry (8) through the entire plate (1 or 2) and that the bore (36, 47) is closed on both sides by locking screws (38, 39, 49.49 ') is closed and that these locking screws also serve as end stops for the control slide (37,48). 7. Control according to claim 6, characterized in that a pilot valve via a first auxiliary valve (26) is provided in the connecting plate (2), and that a pilot valve via a solenoid (5) and a second auxiliary valve (14) is also provided is, wherein the pressure relief valve and the reversing valve have a common control slide (37). 8. Control according to claim 7, characterized in that one end face of the control slide (37) is connected to the pressure port P and the other end face via the two auxiliary valves (14, 26) can be connected to the through channel (10) connected to the return R . 9. Control according to claim 7 or 8, characterized in that the two auxiliary valves (14, 26) are spring-loaded check valves, preferably ball valves. 10. Control according to claim 8 or 9, characterized in that the bias of the compression spring (30) of the first auxiliary valve (26) is accessible from the outside to adjust the maximum pressure. 11. Control according to one of claims 7 to 10, characterized in that the auxiliary valve (14,26) is arranged in an easily replaceable hollow screw (27) or (16), in one bore end of which a valve seat (17) or ( 28) is provided. 12. Control according to claim 9, characterized in that the ball (valve body 21,31) is guided displaceably in the axial direction. 13. Control according to claim 12, characterized in that the stroke of the valve body (21,31) is limited by a stop (18 or 29) and that the radial guidance is still present when this stop is reached. 14. Control according to claim 12 or 13, characterized in that the radial guide is formed by a radial slots (23) or (33) having the cylinder wall. 15. Control according to one of claims 11 to 14, characterized in that the sealing surface of the valve seat (17.28) is formed by stamping. 16. Control according to claim 11, characterized in that the valve seat (28) at the end of the bore in a paragraph is held by flanging the banjo bolt (27). 17. Control according to claim 11, characterized in that the hollow screw (27) on the valve seat (28) opposite end a key surface and then a thread for screwing in the plate (2) and a distance from the thread in the region of the free end Has a groove for a seal (35) and in between a connecting channel (34) between the interior of the banjo bolt (27) and an annular channel (12) connected to the return R is provided. 18. Control according to one of claims 10 to 17, characterized in that in the hollow screw (27) a spring (30) supporting adjusting screw (29) is received, one end of which carries a stop for the valve body (31) forming spring guide and a cap nut is screwed onto the end protruding from the hollow screw (27). 19. Control according to claim 11, characterized in that a mushroom-shaped spring support (18) is held in one end of the hollow screw (16), the through openings (19) and which also serves as a stop for the valve body (21). 20. Control according to claim 19, characterized in that the mushroom-shaped spring support (18) in a shoulder of the hollow screw (27) is received and held by a flange. 21. Control according to claim 11, characterized in that an actuating pin (22) for the valve body (21) is guided axially displaceably in the valve seat (17). 22. Control according to claim 21, characterized in that the length of the actuating pin (22) is dimensioned such that when the actuating pin (22) is pressed down flush with the valve seat (17), the valve body (21) is located shortly before its stop. 23. Control according to one of claims 11 to 22, characterized in that the hollow screw (16,27) has a cutting edge which cooperates sealingly with a sealing surface of the plate (1,2), at least the cutting edge being harder than the sealing surface . 24. Control according to claim 6, characterized in that in the control slide (37) at least one throttle (41) having through channel is provided through which the two end faces of the Control spool (37) are interconnected. 25. Control according to claim 24, characterized in that via the passage channel in the control slide (48) both end faces of the control slide (48) with the passage channel (11) connected to the pressure connection P are each connected via a throttle (G0, 60 ') . 26. Control according to one of claims 1 to 24, characterized in that via the control slide (37) the channels (10, 11) connected to the pressure connection P and the return R can be connected and disconnected and that a preliminary throttle (to initiate the connection) 44) is provided. 27. Control according to claim 26, characterized in that at least one transverse bore in the control slide (37) serves as the pre-throttle (44). 28. Control according to claim 6, characterized in that one of the locking screws (39) also serves as a pressure port P. 29. Control system, in particular according to one of claims 1 to 28 with a control slide displaceably guided by hydraulic pressure, characterized in that control is carried out by the control slide (48) bare ring channels (52, 52 ', 53) are each connected to a consumer port A or B via an unlockable check valve (55, 55') and one of the check valves (55 or 55 ') can be opened by means of a control piston ( 67) displaceable tappet (68,68 ') acting on the valve body (72) of the check valve (55,55'). 30. Control according to one of claims 1 to 29, in particular according to claim 6, characterized in that the two end faces of the slide valve (48) displaceable by hydraulic pressure are each connected to the pressure port P via a throttle (60, 60 ') and that the two end faces can each be connected to the return R via a controllable check valve (54, 54 '). 31. Control according to claim 29 or 30, characterized in that the check valves (54, 54 ') can each be opened via an electromagnet (4,4') against the action of a spring. 32. Control according to claim 29 or 30, characterized in that the control slide (48) between two biased compression springs (64,64 ') is held and that the effect of these compression springs (64,64') is each limited to the compression spring side stroke range to the central position. 33. Control according to claim 32, characterized in that symmetrically to limit the action of the compression springs (64,64 ') of the control slide (48) each have an end receiving opening (61) for an end of the compression spring (64,64') receiving stop sleeve (62, 62 ') is provided, the projecting edge (63, 63') in the central position of the control spool (48), possibly with some play on the end face of the control spool (48) and on the edge of the bore (47) of the plate (1) abuts and that the projecting edge (63,63 ') opposite the pressure springs (64,64') supporting ends of the stop sleeves (62,62 ') abut the bottom of the receiving openings (61,61') and that when the control spool is displaced (48) in the direction of one of the compression springs (64, 64 '), the stop sleeve (62) or (62') can be lifted off the edge of the bore (47) by the control slide (48) and at the maximum stroke on the screw plug (49) or (49 ') comes to the plant. 34. Control according to claim 33, characterized in that the stop sleeve (62,62 ') is guided with radial play in the receiving opening (61,61') of the control slide (48). 35. Control according to claim 29 or 30, characterized in that the two throttles (60, 60 ') are provided in an axial through bore in the control slide (48). 36. Control according to claim 29, 30 or 35, characterized in that commercially available carburetor nozzles are provided as a screw insert as a throttle (60, 60 '). 37. Control according to claim 35, characterized in that the two throttles (60, 60 ') provided in the control slide (48) are connected via at least one transverse bore (59) to an annular groove (57) in the control slide (48), and that a on two shoulders of the annular groove (57), a sieve (58) is provided on the entire circumference. 38. Control according to one of claims 29 to 37, characterized in that in the control slide (48) receiving bore (47) symmetrical to the plane of symmetry (8) at least five ring channels (50.50 ', 51.51', 52.52 ', 53) are provided that the two ring channels (51,51') with the through channels (10) connected to the return R, the middle ring channel (53) with the pressure port P and the two intermediate ring channels (52, 52 ') are connected to consumer ports A and B via hydraulically unlockable check valves (55, 55'), and that the control slide (48) also has two ring grooves (56, 56 ') . 39. Control according to Claim 38, characterized in that the two unlockable check valves (55, 55 ') are arranged symmetrically in a stepped bore (65) and by a control piston (67) which unlocks one of the two check valves (55 or 55'), if necessary are separated, one end face of the control piston (67) being connected to one of the ring channels (52, 52 ') located between them. 40. Control according to claim 38 or 39, characterized in that the check valve (55, 55 ') is formed by a valve seat (71) having a tappet carrier (69) and a spring-loaded valve body, preferably a ball (72) and that the valve body is guided by axial guide surfaces and is guided by a likewise axially displaceable tappet (68, 68 '). 41. Control according to claim 40, characterized in that the tappet carrier (69, 69 ') is inserted tightly in the stepped bore (65) and for this purpose a harder sealing surface of the tappet carrier (69) with a softer sealing edge of the stepped bore (65) cooperates. 42. Control according to claim 41, characterized in that the sealing surface is formed by a circular conical connecting surface and that from this connecting surface connecting channels (75) to the valve seat (71) are guided. 43. Control according to claim 40, characterized in that the guide surfaces for the valve body (ball 72) are formed by a cylindrical bore interrupted by radial slots (74). 44. Control according to claim 39, characterized in that the stepped bore (65) is closed by locking screws (66,66 '), and that in each case the screw plugs (66, 66 ') serve as abutments for the springs (73) of the check valves (55, 55') and at the same time serve to limit the stroke of the ball (72). 45. Control according to claim 40, characterized in that the tappet carrier (69) also serve as stops for the control piston (67). 46. Control according to claim 7, 29 and 30, characterized in that the second auxiliary valve (14) of the connecting plate (2) and the two magnetically controlled check valves (54, 54 ') of the magnetic control plates (1) are of identical design. 47. Control according to claim 40, characterized in that the valve seat (71f for the balls (72) is made by stamping with a ball and a subsequent surface hardening or hardening without further grinding or lapping. 48. Control according to claim 38, characterized in that the edges of the annular grooves (56, 56 ') of the control slide (48) have bevels (77). 49. Control according to one of claims 1 to 48, characterized in that the connections of all Lifting magnets (4,4 ') of the magnetic control plates (1) are each connected to the magnetic connection of the electromagnet (5) of the connecting plate (2) via at least one diode. 50. Control according to one of claims 1 to 49, characterized in that the pressure connection P and the tank connection or return R on the connection plate (2) and all consumer connections A, B are each provided on the associated magnetic control plates (1).

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