DE2513918A1 - PRESSURE COMPENSATED HYDRAULIC DRIVE DEVICE WITH A MULTIPLE WORK FUNCTIONS - Google Patents

Description

Our reference: G 1365

Pressure-compensated hydraulic drive device
with a plurality of work functions

The invention relates to a pressure-compensated hydraulic drive device with a plurality of work functions and with feed from a source for hydraulic fluid.

The invention can be used in a wide range of applications, but is particularly suitable for use in a hydraulic circuit with pressure-compensated
Flow regulators or flow adjusters and is described below in particular in this context.

MiJ; the need for more complex hydraulic drive systems Hydraulic drive systems have come to the fore that perform a variety of work functions either one after the other or at the same time. To meet this requirement, there is an interest in hydraulic drive or control systems to provide a variety of work functions with good efficiency and perform well.

One of the essential components in hydraulic circuits of the more recent design is a pressure-compensated control slide.

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Such pressure-compensated control spools not only determine the effectiveness of a hydraulic motor and its working direction, but at a given position of the control spool keep the motor at a constant, set speed regardless of changes in the motor load or the pressure of the feed liquid.

An example of the need for such complex hydraulic systems with pressure-compensated control valves can be found for example in the case of an excavator mounted on a crawler chassis. It is common when using such an excavator Desired and required in many cases, a main boom, a clamp arm and a bucket at the same time to operate. Since each of these operations takes place via a separate control area, the operator must the flow in each control area independent of the other control areas and independent of changes in control the load and pressure. In addition, the operator must perform work functions of the machine can combine without the position control for other work functions are lost or impaired.

In the patent application file number P 24 40 099.5-13 a hydraulic drive system is already proposed which two or more pressure-compensated control spools each of which can control its own separate work function at the same time. This suggestion was very successful as this was done while minimizing the performance of the adjustable feed pump depending on the Fluid requirement of any of the hydraulically operated work functions is achieved. In practical use of drives with this circuit, the work functions do not necessarily require the same operating pressure. Therefore it is possible that some of the work functions

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achieve system relief pressure before other work functions. The pressure compensator, the one with the system relief pressure is fed, is normally in its position for full flow and gives all incoming Hydraulic fluid to the assigned control slide on. If, however, the work function is blocked is, as will be explained in more detail below, it does not require any further supply of hydraulic fluid. The pressure therefore rises and a relief valve opens, which diverts the flow into an accumulator, bypassing the actuators of the work function. If such a work function working under system relief pressure or the control area assigned to it arranged upstream of another work function or its control area with a lower operating pressure is, this can prevent the flow to the downstream work function.

"Blocking" in the present context is to be understood as a situation in which a hydraulic actuator, for example a piston in a hydraulic cylinder that cannot perform its work function and so an increase in pressure brings about in the feed line for the actuator. Such a case can then, for example occur when the piston of the hydraulic cylinder has reached the end of its stroke or when the counter load for the actuator, e.g. the piston is too big and can no longer be overcome.

A machine in which one or more work functions fail in such a blocked position works of course not with optimal efficiency. A sudden, temporary failure of one or more work functions can also cause jolts or jerks during operation the machine.

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The invention provides a pressure-compensated hydraulic drive device with a plurality of work functions and with feed from a source for hydraulic fluid created, in which at least two control areas are provided, each. A work function control and are interconnected, in which one of the control areas is necessary for its work function full amount of hydraulic fluid processed and the remaining hydraulic fluid to the another control area forwards, and in the case of a device for forwarding the hydraulic fluid from the one to the other control area is also provided for the case that one control area is in its working position is blocked.

The pressure-compensated hydraulic drive or control device according to the present invention has two control areas or system controls that are mutually are connected and each perform or control their own work function. One of the system controls processes the required amount of hydraulic oil in order to allow the assigned work function under full Covering the fitness requirements required for this to be able to perform. The remaining hydraulic fluid is diverted to the other system controller or forwarded. A device is provided that allows hydraulic fluid to pass over from one control panel to another control panel if the first control panel is blocked.

In detail, the one system control or the one control area can be connected to a control slide have standing pressure compensator. A first signal line upstream of the control slide brings the Compensator slide in such a position in which the

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Hydraulic fluid can flow on to the other control area, verai the control slide has a sufficient amount of fluid to carry out its work function. A second signal line downstream of the control slide adjusts the compensator slide so that the control slide receives the required amount of hydraulic fluid according to its full needs. According to a first embodiment of the invention, a pressure relief device for discharging hydraulic fluid from the pressure compensator is provided in the second signal line; In a second embodiment of the invention, a pressure relief device for supplying hydraulic fluid to the pressure compensator is provided in the second signal line. In both embodiments, the hydraulic fluid can flow on to the other control area or to the other system control when the control slide is blocked in its working position.

Further details, features and advantages of the invention emerge from the following description of exemplary embodiments with reference to the drawing, in particular in FIG Connection with the additional claims · It shows Fig. 1 schematically simplifies the circuit of a pressure * compensated hydraulic circuit with a plurality of work functions,

FIG. 2 shows an illustration of an embodiment of a device according to the invention, corresponding to the illustration in FIG. 1, FIG.

3 shows a representation corresponding to FIGS. 1 and 2

another embodiment of a device according to the invention,

Fig. 4 is a section through a in the invention Device used pressure relief valve,

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Fig. 5 is a section through an actuator used in the fiction according to en device and

Fig. 6 is a section through a in the invention Device used, designed as a slide member * Pressure relief device.

A pressure compensated hydraulic system with a plurality of work functions has a source of hydraulic fluid, for example a suitable pump 10. Two system controls 12 and 12 * are connected to one another and each can carry out its own, separate work function. The system controller or control section 12 is processing the required amount of that supplied by the pump 10 Hydraulic fluid in order to be able to carry out its work function and conducts the rest of the hydraulic fluid to control area 12 · continue. An institution with a pressure relief valve 16 in a second Signal line 38 enables the hydraulic fluid to be passed on from the control area 12 to the control area 12% if the control area 12 or its control spool is in a blocking position.

1 shows a pressure-compensated hydraulic system with several work functions of the type proposed in the above-mentioned Fateirfcan message file number P 24 40 099.5-13. This system controls a plurality of work functions simultaneously. A pump 10, preferably a pump with adjustable pump power, for example, * a pump of the type Dynapowsr Model No _t 45 (made by The New York Air Brake Company) is in the upper half of Fig * 'illustrated the power DER pump 10 is connected via a lever 20 adjustable _f . öes against the force of a pressure spring -22 pressure. actuate the iv excitation of a piston 24 in a cylinder 26? istc The Purapt 1G is equipped with a suction line 2t vetsefee & c <£ it si * sikse: Spei · =

ft

rather T leads, and with a pressure line 29 leading to the Tax areas 12 and 12 * leads to the present Description are also referred to as system controls, point phone areas or work areas.

In the illustrated embodiment, the. working area 12 and 12 'separate, independent work functions exercise, for example, the work area 12 can move a bucket while the work area 12 'lifts a boom. With the present Embodiment is the control area 12 with a Control slide 30 of conventional design and provided with a pressure compensator 31, which is also conventional Control slide or pressure compensator slide is formed. The control area 12 'has the same components, which are also provided with corresponding reference numbers, but with an additional indicative line.

The compensator slide 31 is over with the slide 31 ' line 32 connected in series. Each of the corapensator sliders 31 and 31 'is connected to the associated control slide 30 and 30 * via lines 33 and 33', respectively. Besides the compensator slide 31 and 31 'are in operation acted upon by pressure or return springs 34 and 34 *, which seek to urge the compensator slide in a position in which a flow from the line 29 and the line 32 from via the lines 33 and 33 · to the Control slides 30 and 30 'is possible. A first signal line 36 »which is arranged upstream of the control slide 30 or is connected, can be a pressurization of the control slide, not shown in the Compensator slide 31 in the direction of a switching position in which a deflection or forwarding of Liquid to the compensator slide 31 'via the line takes place when the control slide 30 is in the middle position shown in FIG. A check valve 40

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against a load drop, which is arranged in the line 33, prevents a backflow of liquid from the actuator, when the control slide 30 is in its feed position, in the hydraulic fluid Actuator is to be supplied, but the pump does not work. A second signal line 38 between the Control slide 30 and the pressure compensator 31 allowed a pressurization of the compensator slide 31 by liquid from the area downstream of the control slide in the same direction as the compensator spring 34. The signal lines 36 and 38 sense the pressure drop across an adjustable opening 42 in the control slide 30 and adjusting flow from the compensator slide 31 to the Control slide 30 so that a constant pressure drop across the adjustable opening 42 is achieved.

The line 32 connects the compensator slide 31 and 31 ' in a series connection, i.e. it connects the two control areas 12 and 12 '. One downstream of the compensator slide 31 'connected flow line 44 leads to a device which detects the overall requirements of the system and adjusts the output of the pump 10 accordingly. This device has a throttle opening 46 and a control slide designated as a whole with 48 on. The control slide 48 has a slide body 50 acted upon by a spring 52, and also further Openings 54 and 56 for the application of the measurement signals, an outlet opening 58 to the memory T, one Control opening 60 and a pressure opening 62. The opening 56 for the measurement or control signals allows an application of the slide body 50 by pressure fluid in the opposite direction to the force of the pressure spring 52 accordingly the pressure arriving via a line 64 from the upstream side of the throttle opening 46. The slide body is corresponding 50 acted upon in the direction of action of the spring 52 by measuring pressures from the line 66, which one of the

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Downstream of the throttle opening 46 corresponding pressure leads.

The pressure port 62 receives fluid from the pump 10 via lines 29 and 68. The control port 60 is connected via a line 70 to the cylinder 26, while the outlet port 58 via a line 72 with the Memory T is connected. The lines 74 and 74 'extend from the spools 34 and 34' into the Memory T.

The shut-off device or valve 75, which is commonly referred to as a pressure compensator control slide, limits the maximum pressure generated by the pump 10. One Pressure opening 76 of the control slide 75 receives liquid from the pump 10 via the lines 29 and 78 Pressure in the opening 76 acts against a spring 80 and can move the slider body 82 so that over the control slide 48 and the line 70 liquid flows into the cylinder 26 of the pump 10.

This hydraulic system is illustrated in more detail using a description of a typical mode of operation. if the hydraulic system is in its neutral rest position or idle division in which the pump works, however the work functions are not in operation, a work function can be actuated, for example when, for example, the operator wants to raise the main boom of an excavator. The operator can do this for example, actuate the control slide 30 by hand in such a way as to carry out the desired Work function is required. This displacement of the control slide 30 allows passage the hydraulic fluid under pressure from the pump 10 through the pressure line 29 into the pressure compensator The slide member not shown in detail in the pressure com-

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pensator 31 is normally from the spring. 34 applied so that a full flow through the line to the control slide 30 can take place. Depending on the setting of the adjustable opening 42, what by definition the position of the slide member of the control slide takes place, the signal lines 36 and 38 set the compensator slide 31 in such a way that only those necessary to carry out a work function, for example movement of a piston in an actuating cylinder via a desired one Distance, required amount of hydraulic fluid can enter the control slide 30. Those from the actuator such as the illustrated hydraulic cylinder Hydraulic fluid flowing back is diverted into the reservoir T via the line 74. The rest of the from the flow offered to the pump 10 is passed on or via the line into the downstream control region 12 ' diverted. The operator can operate another work function in which the control area or the System control 12 'in the one explained for the control area 12 Way is used.

If more pressure fluid is offered by the pump 10 than is necessary, it flows via the line 44 to the opening 46 and causes a pressure drop. The pressure is then detected upstream of the opening 46 through the line 64 and fed to the measurement signal opening 56 in order to urge the slide body 50 against the spring 52. At the same time, the pressure downstream of the opening 46 is detected via the line 66 and passed to the measuring signal opening 54, where it counteracts the application of the higher pressure in the opening to the extent of the pressure drop or the counterpressure. The slide body 50 is then set in such a way that pressure fluid flows into the cylinder opening 26 from the pump 10 via the lines 29, 68 and 70. This flow moves the piston 24 against the

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Force of the spring 22 and thereby sets the pump 10 so that it only supplies the amount of liquid required for the operation of both work functions.

A difficulty can arise when the system 12 is operating and performing a work function, such as raising the main boom of an excavator, while the control system 12 'is performing another work function. A piston, which is supported so that it can move back and forth in a hydraulic cylinder and is used to raise the boom, can reach its end of stroke. In this case, the hydraulic cylinder can no longer receive hydraulic fluid from the control slide 30. The control area 12 is then blocked.

In this blocking position, the pressure drop across the adjustable opening 42 is almost zero, and thus the pressure in the signal line 36 approximately equal to the pressure in the signal line 38. The compensator spring 34 urges the Slide body in pressure compensator 31 in a switching position, in which this the entire flow for the work function, which is controlled by the control area 12, to Control slide 30 forwards. However, the actuator can no longer take up liquid, so that pressure builds up in the line 29 and reaches the pressure opening 76 of the slide 75 via the line 78. The increased Pressure urges the spool body 82 against the spring 80 and allows flow from the pump 10 over the Lines 29, 78 and 70 into cylinder 26. This liquid entering cylinder 26 causes movement of the piston 24 and the lever 20 against the force of the spring 22, whereby the pump is set to zero power will. Therefore, if the control area 12 is blocked, no liquid will flow to the control area 12 '.

In the inventive design of such a

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Hydraulic circuit, however, a flow from the control area 12 to the control area 12 'is enabled when the former Control area 12 is blocked. For this purpose, FIG. 2 shows a first embodiment of the present invention shown. With the exception of the second signal line, this embodiment corresponds to the hydraulic system according to FIG Fig. 1 so that only the control areas are illustrated. Corresponding components have the same reference symbols. The second signal line 138 has a control slide line 84, one end to the control slide and the other end to one end of a main line connected. A compensator line 90 is at one end to the pressure compensator 31 and at its other end End to main line 86 and a relief line connected. A relief valve 16 is with the other end of the relief line 92 and one end of a Drain line 93 to memory T connected. A throttle can be provided in the main line 86. A secondary line 88 is shown because this is in a schematic or circuit diagram-like illustration of a pressure relief valve it is required. However, the line 88 occurs in the pressure relief element designed as a slide element according to FIG. 6 in effect.

As illustrated in FIG. 4, the pressure relief valve 16 include a housing 94 with a seat 96 which is in flow communication with the relief line 92 stands. A movable closing body 98 such as a ball rests on the seat 96. A feather urges the closing body 98 against the sealing seat 96 against the fluid pressure in the relief line 92. The Ball 98 lifts off the sealing seat 96 and provides a connection between the relief line 92 and the drain line 93 when the fluid pressure in the relief line 92 increases so that the closing force of the spring 100 is overcome.

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The mode of operation of a device according to the invention is illustrated in more detail below with the aid of a typical mode of operation of the hydraulic system shown. When the control area 12 is in the blocking position explained above, the fluid pressure in the signal line 138 rises and causes the closing body 98 to lift off the seat 96 against the force of the closing spring 100, so that pressure fluid can pass from the compensator line 90 through the relief line 92, the relief valve 16 and the drain line 93 to the reservoir T. This lowering of the pressure on the spring-loaded side of the pressure compensator 31 enables the higher pressure of the first signal line 36 to move the control element of the compensator into a position in which the flow is passed on via line 32 to control area 12 ^1. Although the work function assigned to control area 12 is stopped, the work assigned to control system 12 'can function can still be operated.

The throttle 18 can be used to reduce the flow of the control slide line 84 into the memory T overflowing amount of liquid are used. In this way - must the pump 10 convey less liquid than otherwise required and therefore works with better efficiency and with lower cost. The restrictor 18 can be of any desired size, such as about 1.5 mm (0.06 inces), being approximately 3.8 liters (1 gallon) per minute with a pressure drop across the restrictor 18 of about 7 bars (100 psi) pass through it.

A second embodiment of the present invention, as shown in Fig. 3, corresponds essentially to the first embodiment, with the exception of details the configuration of the second signal line 238.

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The second embodiment is a pressure relief valve 16 is provided in the second signal line 238 to fluid in the second signal line 238 to the pressure compressor 31 feed. The hydraulic fluid can then from the control area 12 to the control area 12 * flow when the control area 12 is blocked.

The second signal line 238 has a control slide line 104 which is connected to the control slide 30 at one end and at its other end to a discharge line and connected to one end of a jerk line 108 is. A compensator line 110 is at one end connected to the pressure compensator 31 and at the other end to the control slide line 104. A pressure relief valve 16 is connected at one end to the other end of the relief line 106 and to one end of a working line 112. An actuator 116 is on the other end of the working line 112 is connected. The check line 108 has a check valve 118 on which a flow from the working line 112 to the control spool line 104 is permitted. A secondary line 114 is shown as this is a schematic or circuit diagram of a pressure relief valve is required. However, the line 114 occurs in connection with that designed as a slide member Pressure relief device according to FIG. 6 in effect.

In Fig. 5 details of the actuator 116 are shown, which has a cylinder 120 in the Pressure fluid flows in from the working line 112. This pressure fluid controls a reciprocating movement of an actuating piston 122 in the cylinder 120. As the actuating piston 122 is connected to the slide or control body in the compensator 31, the piston 122 urges the slide body against the compensator spring 34.

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For a better understanding of the second invention Embodiment according to Pig. 3 it is assumed that the Control area 12 is blocked. The pressure in the control spool line 104 is transmitted via the relief line to the pressure relief valve 16, whereby the Closing body 98 is lifted against the force of spring 100. This allows liquid to flow through lines 104 and 106, Flow via the sealing seat 96 into the line 112 and consequently to the actuating member 116. The actuation piston 122 meets the control body of the pressure compensator, not shown in detail, and moves it against the Force of the spring 34, whereby the pressure compensator 31 is set so that liquid via the line 32 is forwarded to the control area 12 '. Although the control area 12 is blocked, this can a downstream work function can still be performed.

For a more detailed illustration of the importance of the non-return valve 118 it is assumed that the actuating piston in the actuating member 116 is in the direction of the spring moved. When the work function associated with control area 12 is resumed, it must the control body in the compensator slide 31 move in the direction of the actuating member 116. However can no liquid flows through the working line 112, since the pressure relief valve 16 is in its closed position is. The check valve 118 therefore enables a flow to the control slide line 104 and thus an emptying of the actuator, so that the pressure compensator 31 is again in the direction of application of the Spring 34 can move.

The pressure relief valve 16 according to FIG. 4 is only one example of many commercially available devices which

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can be used in connection with the present invention. For example, a slide member can also be used instead, as illustrated in FIG. 6. The slide member 124 has a cylinder 126 on. A slide body or control body 128 with two control webs 129 are slidably mounted in the cylinder 126. A slide spring 130 in one end of the cylinder acts on the control piston 128 so that a fluid line 132 connected to the slide cylinder 126 in this way is that they always with an annular space 131 between the Control webs 129 is in connection. A line 134 is connected to the end of the cylinder 126 which is the spring 130 has. One pressure line 136 is with the other End of the cylinder 126 connected so that pressure fluid from the line 136 the slide or control body urges against the force of the spring 130, so that a flow from the line 1 32 via the space 131 to the line 1 34 is possible will. When used as a pressure relief valve, for example as a pressure relief valve 16 according to FIG. 2, the line 132 serves as a relief line, the line 136 as Secondary line and line 134 as a drain to the storage tank.

Although, according to the above description, a pump with variable pumping capacity is used, in the invention In connection with this, a pump with constant displacement can easily be used. Furthermore is de above description is limited to only two work functions for the sake of clarity. Of course, an unlimited number of work functions or control areas can be connected in series will. A limit on the number of work functions or control ranges result essentially only from practical restrictions on the pump 10, the usually covers the entire power requirement for all work functions. In addition, .'in some

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In some cases, a control range can be formed by a conventional control slide without pressure compensation.

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Claims (14)

Claims 1.JPressure-compensated hydraulic circuit with a plurality of Work functions and with supply from a source of hydraulic fluid, characterized in that at least two control areas are provided that each control a work function and are interconnected, that one of the control areas is responsible for its work function required full amount of hydraulic fluid processed and the remaining hydraulic fluid to the other control area, and that a device for forwarding the hydraulic fluid from one to the other control area is also provided for the case that the one control area in its working position is blocked. 2. Hydraulic circuit according to claim. 1, characterized in that the a control area, a pressure compensator and a control slide having. 3. Hydraulic circuit according to claim 2, characterized in that the device for forwarding the hydraulic fluid a device for setting the pressure compensator t. 4. Hydraulic circuit according to claim 3, characterized in that the device for setting the pressure compensator has a pressure relief device. 5. Hydraulic circuit according to one of claims 2 to 4, characterized in that the control area has a first, upstream control line connected to the control spool to move a control spool in the pressure compensator Having forwarding the remainder of the hydraulic fluid. 5 0 9 β Λ i / Γι: J -5 / -. 6. Hydraulic circuit according to one of claims 2 to 5 _t, characterized in that the control area downstream of the control slide has a second signal line for moving the control slide in the pressure compensator for forwarding the remainder of the hydraulic fluid. 7. Hydraulic circuit according to claim 6, characterized in that the second signal line is a pressure relief device for setting the pressure compensator. 8. Hydraulic circuit according to claim 6 or 7, characterized in that the pressure compensator further comprises a pressure spring for the slide body and that the first signal line for acting on the slide body against the force of the pressure spring and the second signal line for acting on the slide body is connected in the same direction as the force of the pressure spring. 9. Pressure compensated hydraulic circuit with a plurality of work functions and with feed from one source for Hydraulic fluid, in particular according to one of Claims 1 to 8, characterized in that at least two control areas are provided that each control a work function and are interconnected by one of which is connected to a control slide Has pressure compensator, and a first signal line connected upstream of the control slide for movement a compensator slide in the pressure compensator for forwarding the hydraulic fluid to the other control area and a second signal line connected downstream of the control slide for moving the compensator slide to Has delivery of the required full amount of hydraulic fluid to the control slide, and that in the second signal line a pressure relief device for draining hydraulic fluid from the pressure com- 509841/0354 pensator is provided to relay the hydraulic fluid to enable the other control area in the event that the control slide is in its working position is blocked. 10. Hydraulic circuit according to claim 9, characterized in that that the second signal line has a control slide line, which has one end on the control slide and with the other end is connected to the end of a main line, and has a compensator line that is connected to a End with the pressure compensator and the other end with the other end of the main line and one end of a relief line is connected, the pressure relief device is connected to the other end of the relief line so that the fluid pressure in the relief line the pressure relief device to a liquid discharge from the control slide line, through the main line, the relief line and the pressure relief device in a memory actuated. 11. Hydraulic circuit according to claim 10, characterized in that a throttle is provided in the main line. 12. Hydraulic circuit according to claim 11, characterized in that the pressure relief device is a pressure relief valve has, with a housing with a sealing seat connected to the relief line, a movable one Closing element for the sealing seat and a pressure spring for pressing the closing element against the sealing seat in the opposite direction to the fluid pressure in the relief line, wherein the closing element lifts off the sealing seat when the Pressure in the relief line as a result of a blockage of the control slide beyond a predetermined value increases. 5098-41 / 0354 13. Hydraulic circuit according to claim 11, characterized in that that the pressure relief device is a slide member has, with a cylinder, a slide with two control webs, a slide spring in one end of the slide cylinder and one end to the control valve line and the other end to the valve member connected secondary line, the relief line being connected to the slide cylinder in such a way that it is in communication with an annular space between the two control webs, and the secondary line is connected to another end of the slide cylinder, in the liquid from the secondary line the slide urges against the force of the slide spring to allow liquid to pass from the relief line into the drain line when the control slide is blocked. 14. Hydraulic circuit according to one of claims 1 to 13, characterized characterized in that the other control area has a second pressure compensator and a second control slide having. Empty soap