DE3011088A1 - HYDRAULIC DRIVE CONTROL - Google Patents

Description

BLUMBACH · WESER · BERGEN ^ KRAMER ZWIRNER - HOFFMANN

PATENT LAWYERS IN MUNICH AND WIESBADEN 3 0 I I 0 P P

-7-

Patentconsult Radeckestrasse 43 8000 Munich 60 Telephone (089) 883603/883604 Telex 05-212313 Telogramme Patentconsull Patentconsult Sonnenberger Straße 43 6200 Wiesbaden Telephone (06121) 562943/561998 Telex 04-186237 Telegrams Palontconsull

Sperry Corporation
Troy, me. 48048, USA

Hydraulic drive circuit

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

A large number of hydraulic motors, in particular in the form of hydraulic cylinders, are used in excavators and cranes, and it is customary for each hydraulic motor to be assigned a control pressure-operated directional control valve which is moved by a manually operated control device via the hydraulic control or pilot circuit. The directional control valve is used to supply hydraulic fluid to the hydraulic motor in order to control the direction and speed of the moving slide of the hydraulic motor. The directional control valve of each hydraulic motor also determines the return flow of the hydraulic fluid ₀ It is also known to use so-called load compensating valves or fixed throttles for limiting further operating loads.

Munich: R. Kramer Dipl.-Ing. . W. Weser Dipl.-Phys. Dr. rer. nat. · E. Hoffmann Dlpl.-Ing. Wiesbaden: P.G. Blumbach Dlpl.-Ing. · P. Bergen Prof. Dr. jur. Dlpl.-Ing., Pat.-Ass., Pat.-Anw. until 1979 G. Zwirner Dipl.-Ing. Dlpl.-W.-Ing.

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The invention is based on the object of providing a hydraulic drive circuit for the precise control of the position and speed of the movable member of the hydraulic motor, namely the drive circuit should be of simple construction, easy to manufacture and operate; Furthermore, it should be possible to achieve favorable operating conditions. This includes the following: When the load pressure changes in different parts of the system, the hydraulic drive circuit should remain fault-free, even if several hydraulic motors are supplied from the same pressure medium source; in the case of pushing loads on the hydraulic motors or hydraulic motors, no hydraulic fluid should be taken from the pressure medium source ¹ ; the directional control valves should be arranged near their hydraulic motor in order to prevent the loss of control of the load in the event of a malfunction in the hydraulic lines to the H3'-dromotor, with a device to prevent uncontrolled lowering of the load in the event of a pressure medium failure due to breakage of lines is provided.

The problem posed is achieved on the basis of the characterizing measures of claim 1.

It is of particular advantage that the valves that control the hydraulic flow control from the hydraulic motor, in the case of energy-generating loads, function to control the speed, and that the valves that control the hydraulic flow into the hydraulic motor, in the case of energy-absorbing

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Loads control the speed. The time interval between the coming into effect of the valves, which the Control hydraulic flow in and out of the hydraulic motor, can be adjusted by dimensioning the valves so that the can take into account the special nature of the particular load.

Exemplary embodiments are described with reference to the drawings. It shows:

1 shows a hydraulic circuit according to the invention;

Fig. 2 shows a metering supply valve used in the circuit;

3 shows a discharge metering valve;

4 shows an outlet valve and a discharge measurement valve ;

FIGS. 5 to 7 are diagrams showing the timing of various parts of FIG hydraulic circuit;

8 to 11 show the hydraulic circuit in different operating states;

12 shows a view from above of a valve block according to the invention;

Fig. 13 is a side view of the valve block;

14 shows a view of the narrow side of the valve block;
15 shows a detail according to section 15-15 in FIG. 14;

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16 is a section along line 16-16
in Fig. 12;

17 is a section along line 17-17 in FIG
Fig. 14;

18 is a section along line 18-18 in
Fig. 12j

19 shows a further exemplary embodiment of a hydraulic circuit according to the invention;

Fig. 19a shows a control circuit to be attached to line A-A of Fig. 19;

Fig. 19b; another control circuit, also to the Attach line A-A of Figure 19;

FIG. 20 shows a supply metering valve in the hydraulic circuit according to FIG. 19;

Fig. 21 ■ an outlet valve and discharge measurement valve for the hydraulic circuit according to Fig. 19 »

FIG. 22 shows a discharge measuring valve for the circuit according to FIG. 19; FIG.

23 shows a further embodiment of a hydraulic Circuit according to the invention and

FIG. 23a shows a control circuit to be attached to the line B-B of FIG.

The hydraulic drive circuit shown in FIG

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According to the invention, a hydraulic motor, which is shown here as a hydraulic cylinder 20 with piston and piston rod 21, leads is, hydraulic fluid to the pressure medium delivery pump 22 with different adjustable Hydraulic flow and is promoted with a load sensing control. A manually operated control device 23 supplies control pressure to a valve system 24 for controlling the direction of movement of the hydraulic motor. The hydraulic fluid the pressure medium delivery pump 22 reaches a feed metering valve 27 via a line 25 and channels 26, which serves to direct the hydraulic flow to one or the other end of the hydraulic cylinder 20 and to steer. The feed metering valve 27 is controlled via the control device 23 and control lines 28, 29 as well as -channels 30, 31 acted upon at opposite ends with control pressure. Depending on the direction of movement of the valve, hydraulic fluid passes through supply and discharge channels 32, 33 or lines to one or the other End of the hydraulic cylinder 20.

In the hydraulic circuit there is also a discharge measurement valve 34 at each end of the hydraulic cylinder, 35 is provided, namely in the channels 32, 33 to control the outflowing hydraulic flow, that is, just the End that is not acted upon by the conveyor pump system is, and which outflowing hydraulic flow reaches a return channel 36.

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In the hydraulic circuit are also spring-loaded Cone valves 37, 38 in lines 32, 33 and spring-loaded Anti-cavitation valves 39 »40 are provided, which serve to open the lines 32, 33 to the return channel 36. Further spring-loaded cone valves 41, 42 are assigned to the respective discharge measurement valves 34, 35. One Throttle line 47 with a throttle 49 extends from channel 36 to the respective discharge measurement valves 34, 35 and via check valves 77 to the control lines 29, 30.

In the hydraulic circuit there is also a back-up valve 44 for generating a filling pressure and thus keeping it low the risk of cavitation that could occur when the load's momentum or its weight denotes the risk of cavitation The piston in the hydraulic cylinder is depressed. A pressure relief valve 45 for a filling pump leads excess Pressure medium (if not required at the inlet of the pump 22) and passes this to the back pressure valve 44 to the for the To increase the hydraulic fluid required for the motor.

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The supply metering valve 27 (FIG. 2) has a bore

50 and a slide piston 31 guided therein, which is held in the neutral central position by springs 52 as long as no control pressure is applied. The spool

51 blocks the pressure channel 26 in the middle position

hydraulic flow entering the channels 32, 33. When control pressure is applied in the channel 30 or 31, the slide piston 51 is shifted in the pressure direction until equilibrium exists between the control pressure, the spring force and the flow forces. The direction of movement determines which of the channels 32 or 33 is supplied with pressure medium from the channel 26.

The two discharge metering valves 34, 35 (FIG. 3) are identical formed, which is why only the valve 34 needs to be described. The discharge metering valve 34 has a Bore 60 and a cone valve 61 guided therein. In the cone valve 61, a channel 62 is provided, which in a Space 63 leads inside the cone valve, from which one or more channels 64 lead to the tank channel 36. A valve pin 65 normally closes the connection between the space 63 and the channel 64 under the action of a spring 66. The pressure prevailing in space 63 adapts to the pressure in line 32, and the pressure resulting therefrom The cone valve 61 is held in its seat by an imbalance of forces. The discharge measurement valve 34 also has a piston 67 on, which is urged to the right in Fig. 3 as a result of a spring 68 and a hole for the valve passing through

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has pin 65. The control line 28 of the hand control 23 extends through a channel 69 into a chamber 70, so that if necessary control pressure is applied to the piston 67. In such a case, the piston 67 is turned to the left in Fig. 3 moved and takes the valve pin 65 with, 'so that the space 63 via the channel 64 with the tank channel 36 in connection comes. The resulting imbalance of forces results in a movement of the cone valve 61 to the left, whereby the line 32 can discharge into the channel 36.

It can thus be seen that the same control pressure that is used to determine the opening direction of the feed metering valve is also used to determine and control the opening of the relevant discharge measurement valve, " so that the hydraulic fluid in the hydraulic cylinder can return to the tank line.

Each discharge metering valve 34, 35 is assigned a spring-loaded piston slide 71 (FIG. 4), which in effect occurs when the load pressure in channel 32 exceeds a predetermined value and a flow path from the load over the Acting as a control throttle channel 62, the space 63, the valve chamber 71, a channel 73 to the tank channel 36 opens. This throttled hydraulic flow reduces the pressure and the closing force on the left end of the cone valve 61, which then moves to the left in the drawing and creates a direct connection between channels 32 and 36. To avoid overshooting when the pressure rise is very high, a throttle 72 and an associated one

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Chamber 72a provided so that the gradually increasing pressure in the spring chamber of the cone valve 71 this again returns to the equilibrium position. This negative feedback is also effective with respect to the cone valve 61 and largely prevents overdrive, although the responsiveness the valves 61 and 71 is made high.

The mode of operation of the hydraulic circuit under varying operating conditions is illustrated in FIGS. 8 to 11 explained.

Fig. 8 shows the case of power consumption by the one to be driven When the manual control 23 moves in a predetermined direction to operate the hydraulic cylinder 20 is, the control pressure acting via line 28 and channel 30 shifts the piston slide of the supply valve 27 to the right, whereby the pressure medium flows through the channel 33, the cone valve 38 opens and to port B. of the hydraulic cylinder 20 arrives. The same control pressure is applied to the discharge metering valve 34 and enables it the hydraulic fluid to flow through the connection A of the hydraulic cylinder 20 into the tank channel 36.

If the manual control 23 is adjusted to operate the hydraulic cylinder 20 due to lowering a bar (Fig. 1 and 9), control pressure is generated in line 28. However, the discharge metering valve 34 opens before the supply metering valve 27. The load acting on the hydraulic cylinder pushes this

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Pressure medium through the opening A on the discharge measurement valve 34 past into the return flow channel 36. The cone valve 40 is opened and some pressure medium to the other The end of the cylinder 20, that is to say to the opening B, is conveyed, as a result of which cavitation is avoided. So it will be that Pressure medium brought to the other end of the hydraulic cylinder without opening the feed metering valve 27 and the hydraulic fluid delivered by the pump is used. The same operating position is also when the machine continues to run a load is reached whose momentum is to be slowed down,

In order to achieve the "swimming" operating position (FIG. 10), the manual control 23 is bypassed and control pressure is applied given to both control lines 28, 29. This can be achieved, for example, by solenoid valves 75, which are shown in FIG their energized state bypass the manual control 23 and the pressure medium originating from the control pump 76 directly in the lines 28, 29 leads, whereby both discharge metering valves 34, 35 are opened and both ends of the hydraulic cylinder 20 are in communication with the reflux line 36. In this operating condition, the valve pins 65 of both discharge metering valves are fully retracted, so that the Pressure medium can flow back and forth through the throttling channels 62, 64, as it corresponds to the floating state.

If the pressure at the outlet end A of the cylinder 20 becomes too high (Figs. 4 and 11), the slide valve 71 comes into operation,

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30/140

whereby the cone valve 61 is opened and releases the increased pressure in the channel 36 and at the same time the cone valve 40 opens, which opens the way to the other end B of the hydraulic cylinder. The hydraulic circuit is thus acting as a pilot operated pressure relief valve for the pressurized outlet of the hydraulic cylinder.

By changing the spring forces and the pressure surfaces on the Feed metering valve 27 and discharge metering valves 34, 35 can suitably set the mutual response times will. For example, if the time dependency is set so that the discharge metering valve is the supply metering valve the supply air valve controls the hydraulic flow and the speed in the event that when the piston of the hydraulic cylinder is driven. In such an arrangement with an overtaking load results the pressure created by the load to cause the discharge metering valve to control hydraulic flow and speed. In such a situation, the anti-cavitation check valves 39, 40 allow pressure medium to be directed to the supply side of the hydraulic cylinder flows, so that no hydraulic fluid is required from the pump to the hydraulic cylinder to fill. (When the load is driving, the piston "overtakes" the speed measured to it by the metering valves.) In Fig. 5 the arrangement is shown in which the discharge metering valve comes into operation before the supply metering valve.

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With this knowledge of the independent control of the discharge and supply metering valves, varying metering arrangements can be made to suit the nature of the load situation as found on the particular engine. If primarily energy-absorbing loads come into question, the springs and pressure surfaces of the discharge metering valve can be controlled so that the discharge metering valve opens quickly before the supply metering valve opens (Fig. 6). In the case of mainly excessive loads (Centrifugal masses), the discharge sizing valve can be made to open gradually, but a lot earlier than the supply metering valve, so that the discharge metering valve the main control remains (Fig.7).

As can be seen from FIGS. 1 and 8 to 11, there is a check valve 77 in a branch line 78 of the respective control line 28, 29 next to the discharge measurement valve 34 and 35, respectively intended. The check valves 77 allow the relatively warm and pressurized hydraulic fluid in the Channel 36, in a throttled flow through the control lines 28, 29 back to the manual control and to the hydraulic tank to flow when no control pressure is applied to lines 28, 29. When applying the control pressure to one of the Lines 28 or 29 closes the respective check valve 77 and separates the control pressure from the tank pressure in the channel 36 from.

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In the hydraulic circuit of FIGS. 1 and 8 to 11, the maximum load pressure is provided in one of one To scan series of valve systems 24 that control a plurality of motors (hydraulic cylinders), and these higher To supply pressure to the pump 22 with a variable delivery rate according to the scanned load. Each valve system 24 has a line 79, which leads to an alternately closing valve 80, which the load pressure of an adjacent Motor (hydraulic cylinder) via a line 81 receives. The alternately closing valve 82 also blocks the channel the low pressure and in this way senses which pressure is the highest and a further one alternately closing valve 82 is to be supplied via a channel 83. A conduit 84 extends from channel 32 to the alternately closing valve 82. This senses which of the applied pressures is the greater and sets in such a way that the higher pressure of the adjusting device of the pump 22 is fed. Each valve system in sequence contains such alternately closing valves 80, 82, the load pressure with the load pressure of a Compare the adjacent valve system and compare the higher pressure to the subsequent valve system in the sequence transmit, so that finally the highest load pressure on the pump 22 becomes effective.

The provision of the load sensing system and the two load dump check valves 37, 38 ensure a pressure medium

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vent with the supply metering valve in the middle position so that no restrictors are needed in the load sensing lines which would result in a loss of performance during operation and allow some flow from the load during the build up of pressure in the sensing lines. Furthermore, sets no cylinder drift when other motors (hydraulic cylinder) in activity are. The load dump check valves 37, 38 eliminate the need for close tolerances between the spool 51 and the bore 50.

In practice, the various individual parts of the valve circuit 24 is preferably made as part of a valve block that is mounted directly on the engine 20, so that the need for long lines between the valve circuit and the motor (hydraulic cylinder) avoided will. As can be seen from FIGS. 12 to 18, the Valve block three housing sections 85, 86 and 87. The middle housing section 86 has a mounting surface 88 (Fig. 16, 17), which contains the ends of the channels 32, 33, which are in communication with the engine (hydraulic cylinder). The various components of the valve circuit 24 are housed in the housing sections and are shown in the drawing have been provided with the same reference numerals. The hydraulic circuit according to Fig. 1 is actually folded, to make the valve block more compact. In order to also facilitate the opening of the valves 39, 40, these are theirs respective pre-dimensioning valves 34 and 35 opposite.

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Although the hydraulic circuit works in conjunction with a pump for variable delivery quantities and with control by load sensing, the circuit can also be used in conjunction can be used with a fixed displacement pump which has a variable discharge valve according to a load sampling having. In such an arrangement, the pressure in line 82 is applied to the variable outlet valve associated with the fixed pump created.

Another embodiment of the hydraulic circuit according to the invention is shown in FIG. 19 and 19a. So far the components correspond to the first exemplary embodiment, the same reference numerals are used. The main

The greatest difference is the use of two Feed metering valves 27a and 27b instead of a combined feed metering valve 27. Accordingly, there are two pressure lines P and supply channels 26a, 26b and a number of others Control lines are provided which form two groups C1 and C2. The feed metering valve 27a is thereby via channels 30, 30a controlled with control pressure C1 or C2, while control pressure C2 or C1 can be applied to the supply metering valve 27b via channels 31, 31a. Depending on which supply metering valve 27a or 27b is actuated, the pressure medium is supplied to the hydraulic cylinder 20 in such a way that that the piston 21a or the piston rod 21b is driven to the right or left.

Each supply metering valve 27a, 27b (Fig.20) has one Bore 50 and a slide piston 51 guided therein,

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by a respective spring 52 in its neutral Middle position is held. The slide piston 51 normally blocks the hydraulic flow in the supply channel 26a, 26b to channels 32, 33. When control pressure in control channel 30a or 31a is applied, the spool 51 of the respective Feed metering valve 27a or 27b shifted accordingly until there is an equilibrium of forces between the control pressure, the spring force and the flow forces is established. In this way it is determined which of the channels 32, 33 is supplied with pressure medium from the supply channels 26a or 26b will.

22 shows an enlarged illustration of the discharge measurement valve 34 from FIG. 19. As far as there is a correspondence with regard to the function, the same reference numerals as in the embodiment according to FIG. 3 are used. The spring 66 of the valve pin 65 is arranged in the space 63 of the cone valve 61. The piston 67 is to name the spring 68 is hollow. When control pressure is supplied to the chamber 70 via the channel 28, 69, the moves Piston 67 in the drawing to the left and takes the valve pin 65 with so that the space 63 via the channel 64 with the Return channel 36 comes into connection and that is from it The resulting imbalance of forces causes the cone valve 61 to lift off.

As in the first exemplary embodiment, the same control pressure acts on the respective supply metering valve and the associated discharge metering valve, so that the

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the same hydraulic flow is supplied to the cylinder 20 as it leaves the cylinder and into the return line entry.

As in the first exemplary embodiment, each has a discharge measuring valve a spring-loaded control slide piston 71 is assigned, as shown in FIG. Compared to the first embodiment functionally equivalent parts are given the same reference numerals. The main difference lies in the arrangement of the throttling channel 62, which is now housed as a throttle channel 62a in the slide piston 71 and not in the cone valve 61. The connecting channel 73 between the cone valve 41 and the discharge channel 36 is also on the Back of the piston 67 of the discharge metering valve 34 out. When the valve 41 is open, there is a throttle current via the channels 62a, 73, so that a pressure drop becomes noticeable in space 63, which leads to the opening of the cone valve 61 leads. The combination of the valves. 61, 71 represents a pilot-operated outlet valve. With a high pressure increase in the line 32 there is a risk of the slide piston 71 overshooting and thus overdriving the outlet valve. To counteract this, the throttle 72 and the associated space 72a are again provided.

When the load to be moved absorbs energy, the hand control is used 23 adjusted accordingly, so that, for example, the channels C2 in FIGS. 19 and 19a receive control pressure and the valves 27a and 35 open. The one under pressure

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Hydraulic fluid opens the valve 37 and passes through the channel 32 to the connection A of the hydraulic cylinder 20. The Hydraulic fluid displaced on the other side of the piston 21a reaches the return channel via the connection B and the channel 33 36.

When the hand control 23 to continue running or lowering a Load is actuated, channels C1 receive control pressure, however not to the extent that they open of their own accord. Since the pressure in the channel 32 increases due to the falling load is, first of all opens the discharge metering valve 34 and hydraulic fluid flows into the return channel 36. Since this is at a higher pressure due to back pressure, the cone valve opens 40, so that hydraulic fluid can reach the other port B of the hydraulic cylinder 20 via the channel 33, whereby cavitation is avoided even if the supply metering valve 27b should remain closed.

For the floating mode of operation, the manual control 23 is bridged and control pressure is applied to both control pressure lines 28, 29 created. This can be done in the manner already described using solenoid valve controls. This opens both discharge measurement valves 34, 35 open with respect to the valve pin 65, so that the hydraulic fluid depending on the direction of movement of the piston 21a can circulate between the ports A and B via the return channel 36.

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-25-. ■ .- ■ '■ "" ■

The hydraulic circuit can also be designed to be remotely controllable, as shown in FIGS. 19 / 19b. This system can be operated in the normal way, as described with reference to Fig. 19 / 19a, or in a regenerative

tive operating mode. In this case, hydraulic fluid of the piston rod end 21b can be fed via port B, channel 33, the lifted load drop check valve 38a, the supply metering valve 27b and the pump pressure lines P to the connection A of the hydraulic cylinder flow, with the returned hydraulic fluid in the pump pressure lines with the mixes hydraulic fluid fresh from the pump. In this modified circuit there are three remotely controllable Directional control valves 75a, 75b, 75c for two positions each, for example solenoid valves, are provided to allow the supply of the Control pressure to the supply metering valves 27a, 27b and the discharge metering valves 34, 35 to control. Additionally a fourth, remotely controllable two-position valve 75d is provided around the modified load drop check valve 38a to connect to the tank.

The remote hydraulic control device is connected via the lines C1, C2 to the remotely controllable valve 75a, the line C1 to the second, remotely controllable valve 75b and the Line C2 leads to the third, remotely controllable valve 75c. The second and third valve 75b, 75c are in turn in the switching position shown via the lines C1, C2 with the channels 28, 30, 30a and 29, 31, 31a of the hydraulic

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Circuit of Fig. 19 connected. The modified check valve 38a has a throttle 76 and a channel 78 which leads to the on-off switching valve 75d. The throttle 76 restricts the hydraulic flow flowing to the tank. In the normal operation, the on-off switching valve is 75d de-energized and closed, and the valves 75a, 75b, 75c are also de-energized, so that the channels C1, C2 in the described Way are switched through.

When regenerative operation is desired, valves 75a, 75b, 75c, 75d ~ are energized. As a result, the load drop check valve 38a is connected to the tank, the control pressure to both discharge measurement valves 34, 35 is shut off, and at the same time both supply measurement valves 27a, 27b are opened by the control pressure supplied at the same time. With the check valve 38a open and the supply metering valves 27a, 27b as well as the discharge metering valves 34, 35 closed, the hydraulic flow is guided in such a way that one can speak of the regenerative mode of operation. This is used when a faster movement of the driven member 21 is desired.

If the pressure when returning from port A becomes too high, the control spool piston 71 acts as a preparation to open the cone valve 61, whereby a compensation of the increased pressure takes place and an additional hydraulic flow to the hydraulic cylinder 20 via the opened cone valve 40 takes place.

As in the first exemplary embodiment, the spring forces and the pressure surfaces of the valves can be dimensioned appropriately 27a, 27b, 34, 35, the respective response time can be set appropriately. If, for example, the discharge metering valve chronologically before the supply measurement valve, this respective supply measurement valve controls the hydraulic flow and the speed in the case that the motor (hydraulic cylinder) is driven. When in this arrangement however, the load overtakes the drive, the hydraulic pressure generated by the load will cause the discharge metering valve controls hydraulic flow and speed. In this situation, the anti-cavitation check valves make it possible 39, 40 that hydraulic fluid flows in without the pumped fluid to fill the Hydraulic cylinder is required.

As in the first embodiment, the circuit can be adapted to the special type of load situation. Also the Possibility of discharging the relatively warm hydraulic fluid from the return channel 36 via a throttle flow the lines 28, 29 are given and need not be explained further.

The sampling of the maximum load pressure in a series of Valve circuits 24 for controlling a plurality of motors (hydraulic cylinders) take place in the manner already described Way. In Figs. 19 and 19b the load sensing channels are marked with Designated LS1 and LS2.

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Fig. 23 / 23a show a modification of the hydraulic circuit according to the invention for a one-sided acting Hydraulic cylinder. The piston and piston rod of the hydraulic cylinder are mechanical or by gravity returned. In this modified embodiment, only the elements of the right half of the double-acting are grounded System of Fig. 19 is used.

When the controller 23 (Fig. 23a) is adjusted according to the case of an energy-absorbing load, the piston To drive the hydraulic cylinder, the lines C1 and the channels 28 and 31a receive control pressure. The supply metering valve 27b is shifted to the right, and the pressure medium passes through the channel 33 and the open cone valve 38 into inlet B of the cylinder.

When the control 23 is set to lower the load, the control pressure is fed into line C2 and channel 29, and the discharge metering valve 35 opens. The load resting on the piston rod and piston of the cylinder presses the hydraulic fluid through port B, the discharge metering valve 35 into the return channel 36.

When large actuating cylinders are required, for example in large forklifts and all-terrain devices double-acting cylinder, and when the ratio of the acted upon Area is large, a suitably dimensioned, single-acting system of large volume can be used,

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to control the head end of the cylinder, and a suitable one sized, single acting, small volume system used to control the piston rod end of the cylinder will.

When absolute load locking is required in the interests of safety and no piping between
the head end and the piston rod end of the cylinder are allowed to prevent the load from continuing in either direction, two single-acting systems are placed at each end of the cylinder.

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Claims (19)

BLUMBACH · WESER · BERGEN · KRAMER PATENT LAWYERS IN MUNICH AND WIESBADEN Patentconsult Radeckestrafle 43 8000 Munich 60 Telephone (089) 883603/883604 Telex 05-212313 Telegrams Patentconsull Patenlconsull Sonnenberger Straße 43 6200 Wiesbaden Telephone (06121) 562743/561998 Telex 04-186237 Telegrams Palentconsull 'Sperry Corporation
Troy, me. 48048, USA Patent claims: Hydraulic drive circuit for a) a hydraulic motor, in particular hydraulic cylinder, b) with alternately effective supply and discharge lines as well as control lines, if applicable, c) in connection with a pressure medium delivery pump, in particular with a variable delivery rate according to a load scan, and with d) Valves for steering and controlling the pressure medium from and to the connections of the hydraulic motor, characterized in that in the supply and / or discharge line (32, 33) at least dl) a feed metering valve (27, 27a, 27b) and d2) a discharge metering valve (34, 35) are provided, their readiness states and / or position with regard to flow cross-sections via a control pressure (C1, C2) supplying control device (23) are adjustable. Munich: R. Kramer Dlpl.-Ir.g. · W. Weser Dipl.-Phys. Dr. rer. nat. · E. Hoffmann Dlpl.-Ing. Wiesbaden: P. G. Blumbach Dipl.-Ing. P. Bergen Professor Dr. jur. Dipl.-Ing., Pat.-Ass., Pat.-Anw. until 1979 G. Zwirner Dipl.-Ing. DIpI.-W.-Ing. 0 3 0 0 A1 / 0 8 61 ^{0 RIG! NAL INSPECTED} 2. Hydraulic drive circuit according to claim 1, characterized in that in the supply and / or discharge line (32, 33) a check valve (37, 38) in the manner is arranged that the pressure medium from the supply metering valve (27, 27a, 27b) flow in the direction of the hydraulic motor can, but is blocked in the event of a load drop. 3. Hydraulic drive circuit according to claim 1 or 2, characterized in that an anti-cavitation valve (39, 40) is provided in the supply and / or discharge line (32, 33) which opens the connection between a return channel (36) and the respective supply line (32, 33), when the pressure in the return channel (36) by a certain amount higher than the pressure in the supply line (32, 33). 4. Hydraulic drive circuit according to one of claims 1-3 » characterized in that each discharge metering valve (34, 35) is assigned a modulating control valve (41, 42), which controls the opening width of the discharge metering valve modulated when the pressure in the discharge line (32 or 33) exceeds a predetermined value. 5. Hydraulic drive circuit according to one of claims 1-4, characterized in that the dimensioning and arrangement of the feed metering valve (27, 27a, 27b) and the discharge metering valve (34, 35) is made so that the discharge measurement valve (34, 35) responds in front of the feed metering valve in the opening direction. 6. Hydraulic drive circuit according to claim 5, characterized in that the discharge metering valve (34, 35) is fully open before the supply metering valve (27, 27a, 27b) opens, in adaptation to the first Line driving loads. 7. Hydraulic drive circuit according to claim 5, characterized in that each discharge metering valve (34, 35) begins to open before the supply metering valve (27, 27a, 27b) opens and moves towards a gradual opening, adapting to primarily ongoing loads. 8. Hydraulic drive circuit according to one of claims 1-7 » characterized in that the supply metering valve (27, 27a, 27d) and the discharge metering valve (34, 35) for fastening are formed in close proximity to the hydraulic motor. 9 · Hydraulic drive circuit according to claim 8, characterized in that the feed metering valve (27, 27a, 27b) and the discharge metering valve (34, 35) in a housing (85, 86, 87) for attachment to the hydraulic motor (20) is trained. 10. Hydraulic drive circuit according to one of claims 1-9, characterized in that for connecting a plurality of drive circuits (24) with a pressure medium delivery pump (22) comparison devices (80, 82) for comparing the load pressures neighboring drive circuits and determining the highest i 030041/0661 Load pressure are provided. 11. Hydraulic drive circuit according to one of claims 1-10, characterized in that a single supply metering valve (27) is provided for blocking two channels (32, 33) or for releasing one of these channels, which Part of the supply and discharge line are-and in which One discharge measurement valve (34, 35) is located in each case. (Figures 1 to 11). 12. Hydraulic drive circuit according to one of claims 1-10, characterized in that two feed metering valves (27a, 27b) and two discharge metering valves (34, 35) are provided are, in each case a feed metering valve (27a) and a discharge metering valve (34) in the course of a channel (32) and the other supply metering valve (27b) is arranged with the other discharge metering valve (35) in the other channel (33) are (Figs. 19 to 22). 13. Hydraulic drive circuit according to claim 12, characterized in that each feed metering valve (27a, 27b) can be actuated selectively with control pressure (C1 or C2). 14. Hydraulic drive circuit according to claims 2 and 12 or 13 » characterized in that the one with the piston rod connection (B) related load drop check valve (38a) can be opened remotely (75d), namely 030 0 41/06 61 at the same time as the supply metering valve located in the same channel (27b), for the purpose of a regenerative mode of operation. 15. Hydraulic drive circuit according to claim 14, characterized in that for remote control of the load drop check valve (38a) this has a throttle channel (76, 78) to the tank, in which a remotely controllable on-off switching valve (75d) is arranged. 16. Hydraulic drive circuit * according to claim 14 or 15, characterized in that for the simultaneous opening of the feed metering valve (27b) and the load drop check valve (57a) three remotely controllable valves (75a, 75b, 75c), each with two switching positions, are provided, which control lines (C1 or C2) switch in such a way that in their first position the control pressure to one or the other discharge metering valve (34 or 35) and the feed metering valve. len (27b or 27a) is performed and in a second layer the control pressure is applied simultaneously to both supply metering valves (27a, 27b) and from both discharge metering valves (34, 35) is blocked. 17. Hydraulic drive circuit according to claim 16, characterized in that the first remotely controllable valve (75a) in its first switching position either the control pressure to the second (75b) or to the third valve (75c) and in its second position the control pressure to both downstream valves (75b, 75c) switched through, so that 030041/0661 when the on / off switching valve (75d) is in the on position, the pressure medium from the piston rod connection (B) via the supply metering valves (27b, 27a) to the cylinder head connection (A) can flow. 18. Hydraulic drive circuit according to one of the claims 1 to 17, characterized in that a three-part housing (85, 86, 87) is provided for receiving the valves, which in the are arranged essentially in two planes (Fig. 16, 18). 19. Hydraulic drive circuit according to claim 3 and 18, characterized in that in each case an anti-cavitation valve (39, 40) and a discharge metering valve (34, 35) face each other with regard to a return channel (36) (Figures 16, 18). 030041/0661