EP0053323B1 - Hydrostatic transmission system with a variable pump and several actuators - Google Patents

Description

The invention relates to a hydrostatic drive system with an adjustable pump, to the delivery line of which a plurality of consumers each having an inlet connection and an outlet connection are connected, each of which can be individually controlled by means of a directional control valve which throttles in intermediate positions, the adjusting element of the pump being displaceable in a pump actuating cylinder Pump actuating piston is connected and the pressure medium inflow and outflow to and from the pump actuating cylinder is controlled by means of a pump adjustment directional control valve which has a control slide valve, one side of which is acted upon by the pressure in the pump's conveying clothing in front of the directional control valve and the second side of which is by a spring and the pressure in a control pressure line is applied, the control pressure line with the delivery line between each of the directional control valve and the associated consumer via control pressure branch lines, in which opening towards the control pressure branch line Check valves are arranged, is connected.

In a known drive system, the task and function of the system are merely to adjust the adjustable pump in such a way that it does not deliver against an unnecessarily high pressure, but rather that only the pressure that is actually required by a consumer is generated in the delivery line. The pressure drop that arises on the arbitrarily controlled control directional valve due to the throttle effect in this pressure gradient must correspond to the force of the spring against which the control slide of the pump adjustment directional control valve is supported. This known system can only be used if only a single consumer is activated at any given time. If two of the control directional control valves were actuated at the same time in a throttling position and the two consumers controlled by these directional control valves were loaded equally, the shuttle valve provided in this system is in an indifferent position, so that this pressure medium between the controlled consumers leads in an uncontrollable manner - and can flow here. However, if two control directional control valves are fully open and the loads controlled by them are loaded differently, the pressure medium can flow freely through the two opened control valves from the more heavily loaded consumer to the less heavily loaded consumer, so that the more heavily loaded consumer uncontrollably under the load acting on it backs away and the less burdened consumer accelerates accordingly in an uncontrolled manner. This system is therefore not usable if it is necessary to be able to control several consumers with different loads at the same time (DE-A-21 59 766).

Furthermore, a control valve with pressure relief for a system with a constant pump is known, a part of the current delivered by the constant pump that is not consumed by the consumer being discharged. For the purpose of controlling each of the two consumers, a longitudinal slide is provided with a longitudinal bore and radial bores and annular grooves, a throttle element which is displaceable against a spring being arranged in the longitudinal bore. The space in front of the end face of this respective throttle element is neither connected to the pressure line nor to the drain line in the neutral position of the slide. In one of the two possible displacement directions controlled slide one of the radial bores in connection with the longitudinal bore is connected to the discharge channel, so that the space in front of the end face of the throttle element in the longitudinal bore of the slide is acted upon by the inlet pressure. The pressure on the other side of this throttle element, which is arranged in the longitudinal bore of the slide and is supported against a spring, is determined via a non-return valve by the pressure which is applied to the consumer with the higher pressure. With this device, it is not possible to take into account a negative load on the consumer. The spaces behind the throttle element in each longitudinal bore of a slide are continuously connected to the outlet via a throttle opening, so that a leakage current flows continuously through the throttle opening, the size of which, as a result of the constant width of the throttle opening, depends on the level of pressure at the respective highest pressure leading consumer (FR-A-21 83 825).

Furthermore, a hydraulic system is known with a number of differently acting, single-acting consumers, which are connected in parallel to one another and are controlled jointly via a single directional valve. The flow of pressure medium flows to each consumer via a metering orifice and a throttling point connected downstream thereof, the throttling point having a slide which on its front face is affected by the pressure behind the metering orifice and on the back by the pressure with which the consumer with the highest pressure acts is burdened. With this system, lifting or lowering is only possible for all consumers together. If a lowering of all loaded consumers is controlled by throttles on the common directional valve, the individual consumers will fall back one after the other in the order of the load. That means the consumer with the highest load will sink back first. The non-adjustable orifices only exert their effect if all of these orifices are inevitably flowed through by the pump. These orifices only allow the consumers to be driven together to the end position. The control pressure lines are not relieved of pressure, so that the pump always delivers against the pressure of the consumer most recently pressurized (DE-A-22 60 457).

In particular, the invention relates to a hydrostatic drive system for a construction machine, in particular for an excavator, in which the consumer has one or more cylinders for lifting the boom, at least one cylinder for actuating the bucket, at least one further cylinder for kinking the arm, at least another consumer can be a hydraulic motor for the chassis and / or at least one further consumer can be a hydraulic motor for pivoting the excavator superstructure. In the currently known excavators, the pump emits a delivery line to which control directional valves are connected, the branch lines emerging from these control directional valves leading to the individual consumers. The individual control directional control valves are usually combined to form a block control device, the individual sections of which form the control directional control valves to the individual branch lines. If at all, the pump is only regulated depending on the delivery pressure in the delivery line. The delivery flow flowing to the individual consumers is arbitrarily controlled only by opening the control directional control valve, which is assigned to intermediate positions and which is in intermediate positions, to a greater or lesser extent. Any repercussions that result from changes in the working pressure in a consumer must be compensated for by the operator through arbitrary control interventions.

The present invention is based on a drive system of the type mentioned the task of designing the system such that changes in pressure caused by changes in the load on a consumer do not affect the other consumers connected in parallel to the same pump , but that pressure medium flows to each consumer with the pressure determined by the load of the respective consumer with the arbitrarily selected current, changes in the load being taken into account to any extent up to the negative load when the pump is set to the most favorable value with regard to energy consumption will.

• ä) zwischen jedem Wegeventil und dem jeweils zugeordneten Verbraucher ist in der jeweiligen Förderzweigleitung je eine einstellbare Drosselstelle angeordnet, deren Einstellorgan in Öffnungsrichtung von dem in der Förderzweigleitung hinter dem Wegeventil wirkenden Druck beaufschlagt ist, wobei das Einstellorgan auf der entgegengesetzten Seite von einer Feder und einem in einem Steuerdruckraum wirkenden Steuerdruck beaufschlagt ist, wobei die Einstellorgane aller jeweils einem Verbraucher zugeordneten Drosselstellen von dem gleichen, in einem mit einer Druckentlastung versehenen Steuerdruckraum anstehenden Steuerdruck beaufschlagt sind,
• b) die Steuerdruckräume der Einstellorgane aller Drosselstellen sind mit der an das Pumpeneinstellwegeventil angeschlossenen Steuerdruckleitung verbunden,
• c) jedem als Zulaufanschluß betreibbaren Anschluß jedes Verbrauchers ist ein Wegeventil mit nachgeschalteter Drosselstelle zugeordnet.

This object is achieved according to the invention by combining the following features:

• Ä) Between each directional valve and the respective associated consumer, an adjustable throttle point is arranged in the respective delivery branch line, the setting member of which is acted upon in the opening direction by the pressure acting in the delivery branch line behind the directional valve, the setting member on the opposite side by a spring and a control pressure acting in a control pressure chamber is acted upon, the setting members of all throttle points respectively assigned to a consumer being acted upon by the same control pressure present in a control pressure chamber provided with pressure relief,
• b) the control pressure chambers of the setting members of all throttling points are connected to the control pressure line connected to the pump setting directional valve,
• c) a directional valve with a downstream throttle point is assigned to each connection of each consumer that can be operated as an inlet connection.

In the drive system according to the invention, several consumers, namely any of the existing consumers, can be controlled simultaneously in any direction of movement for any movement speed, each consumer moving at the controlled speed regardless of the load, each change in load regardless of its sign on the pump setting element is taken into account.

In addition, the invention opens up the possibility of various, very advantageous further developments.

According to an expedient further development, a delivery branch line starting from an adjustable throttle point and a return line are connected to each of the two connections of each consumer or at least some of the consumers, with a combined pressure-limiting and lowering brake valve in the return line, one control pressure chamber of which connects to the other connection of the same consumer leading feed branch line is connected is arranged. This makes it possible to control each consumer or the consumers connected in this way in both directions of movement with the device according to the invention.

In a drive system in which an outlet to a container is provided for pressure relief for the control pressure line, according to an expedient further development it is provided that a flow control valve is arranged in the outlet line provided as an outlet. The. Pressure relief has the advantage in itself that a higher control pressure is not present and the pump is thus swung out to a greater flow than required. A particularly favorable adaptation characteristic can be achieved by the arrangement of the flow control valve.

According to another expedient embodiment, it is provided that a check valve which opens towards this line is arranged behind the throttle point in a connection between this feed branch line and the line leading to the associated throttle point, in order to relieve the pressure on the delivery branch line. This has the advantage that only the line which actually carries the higher pressure is relieved.

This embodiment is particularly expedient if a drive system with a check valve arranged in the throttle element is used as the check valve arranged in the connection between the delivery line and the line leading to the throttle point.

A further advantageous refinement results if a two return line originates from each consumer and all two return lines are connected to a collective return line which is connected to the housing of the pump sucking out of the housing, a preloaded pressure accumulator being connected to the collective return line so that the pump housing always runs maintain a certain pressure, which is given by the preload, which facilitates priming of the pump or avoids cavitation during priming.

According to another expedient refinement, it is provided that two consumers connected in parallel to one another are connected to one throttle point and are controlled jointly by the one throttle point. This arrangement reduces the number of throttling points required.

Furthermore, there is an expedient embodiment if all of the throttle points assigned to a consumer or a group of consumers are combined in a control unit which is in each case arranged directly on the assigned consumer or the assigned consumer group. By combining them in a control unit, these organs, which all require the same degree of maintenance, can be arranged together in a protected manner, in such a way that the individual lines from the individual throttle point to the consumer are as short as possible.

According to a further embodiment, it is provided that the valve group formed from the check valves and the pressure limiting and lowering brake valves is arranged together with the throttle points in an overall control unit.

In a drive system with at least two pumps, in which at least one of these two pumps is assigned to several consumers, there is an expedient further development if both the delivery lines and the control pressure lines of both pumps are connected to an interconnection device, which occurs when there is a pressure difference between the delivery line and associated control pressure line, which is smaller than the pressure difference intended on the directional control valve, connects the two delivery lines to one another and connects the two control pressure lines to one another, so that both pumps deliver to the consumer who is controlled to take up such a current that the flow of a pump can no longer generate the pressure difference provided on the directional control valve.

According to a further expedient refinement, a limit load control device which triggers a pressure signal when the speed of the pump drive shaft drops is provided, the pressure signal acting on a pump adjustment directional control valve, with the result that when the torque absorbed by the pump or pumps increases, the drive speed the primary energy source driving the pump or pumps is pressed, the pump or pumps are set to a smaller stroke volume per revolution and thus consume less power and thus relieve the primary energy source.

According to a further expedient embodiment, it is provided that a pressure relief valve is connected to both the delivery line and the control pressure line, a throttle point being arranged between the control pressure line and the pressure relief valve in the connecting line, and the pressure relief valve connected to the control pressure line being at a lower pressure is set as the pressure relief valve connected to the delivery line.

According to a further expedient refinement, it is provided that one of the consumers is assigned an additional control unit in which a four-port / three-position directional control valve is arranged, to which on the one hand the delivery line and the return line and on the other hand two lines leading to one connection of the consumer are connected, each Side of the valve has two pressure chambers, one of which is connected to an arbitrarily operable control pressure transmitter and the other to one of the two lines leading to the consumer, the respectively actuated control pressure transmitter on each side and the pressurized of the two lines leading to the consumer is connected to the other side of the valve and a branch line is connected to each of the two lines leading to the consumer, both of which lead to the collective control pressure line, in each of these two branch lines one to d he collective control pressure line opening check valve is arranged.

It can be advantageous that all control units of the overall system are combined to form an assembly, in particular in the form of a valve block.

The invention makes it possible to utilize the device with a control pressure line in the case of a plurality of consumers which can be arbitrarily connected in parallel with one another, pressure regulation being effected by a valve, the valve slide of this valve on the one hand by an arbitrarily actuable control pressure transmitter and on the other Side is under pressure from the consumer, so that when the control pressure transmitter is actuated, an equilibrium state is established on the valve slide between the control pressure transmitter pressure and the pressure in the pressure-carrying line leading to the consumer. If the pressure in this line leading to the consumer, which is pressurized, drops, the valve is opened further, so that a larger current flows to the consumer and the pressure at the consumer is increased due to the expected consumer detection. This valve can also be used to arbitrarily preselect a certain pressure that occurs at the consumer by means of an arbitrarily given setting for a control pressure transmitter, it being assumed that with increasing flow rate, the force reaction at the consumer increases due to increasing speed of movement. In this new device, the pressure control is effected by a valve with the advantage that this device can be connected to the line system according to the invention with the delivery line emanating from the pump, a return line and a control pressure line leading to the control pressure acting on the servo control valve of the pump . In this case too, this control unit can be connected or attached directly to the consumer and additionally contain suction check valves or pipe rupture safety valves and pressure relief valves, the control pressure line being connected via a check valve in this case as well. The purpose of these devices is a regulation to constant, arbitrarily selectable pressure and thus constant force or constant moment at the consumer. These facilities also make it possible to reduce energy losses.

• Figur 1 zeigt einen Gesamtübersichtschaltplan und die weiteren Figuren zeigen die Schaltschemen zu den einzelnen in der Gesamtübersicht gemäß Figur 1 nur umrißartig dargestellten Baugruppen.
• Figur 2 zeigt das Schaltschema zu dem Doppelpumpen-Aggregat 24.
• Figur 3 zeigt das Schaltschema zu der Grenzlaststeuereinrichtung 230.
• Figur 4 zeigt das Schaltschema zu der Zusammenschalteinheit 179.
• Figur 5 zeigt das Schaltschema zu der Teilsteuereinheit 27 und zu der Steuereinheit 74.
• Figur 6 zeigt das Schaltschema zu der Steuereinheit 74 oder 75 mit zugeordnetem Verbraucher.
• Figur 7, Figur 8 und Figur 9 zeigen jeweils eine Gesamtsteuereinheit 85 bzw. 110 bzw. 111 mit zugeordnetem Verbraucher.
• Figur 10 zeigt das Schaltschema zu einer auf konstanten Druck regelnden Regeleinheit.
• Figur 11 zeigt eine andere Ausgestaltungsform zu einer Teilsteuereinheit.
• Figur 12 zeigt das Schaltschema zu einer Zusammenschalteinheit in einer weiterentwickelten Ausgestaltungsform.

In the drawing, an excavator control is shown in the circuit diagram as an exemplary embodiment of the subject matter of the invention and two modifications to each detail of the exemplary embodiment are shown.

• FIG. 1 shows an overall overview circuit diagram and the other figures show the circuit diagrams for the individual assemblies shown only in outline in the overall overview according to FIG. 1.
• FIG. 2 shows the circuit diagram for the double pump unit 24.
• FIG. 3 shows the circuit diagram for the limit load control device 230.
• FIG. 4 shows the circuit diagram for the interconnection unit 179.
• FIG. 5 shows the circuit diagram for the partial control unit 27 and for the control unit 74.
• FIG. 6 shows the circuit diagram for the control unit 74 or 75 with an associated consumer.
• FIG. 7, FIG. 8 and FIG. 9 each show an overall control unit 85 or 110 or 111 with an associated consumer.
• Figure 10 shows the circuit diagram for a control unit regulating to constant pressure.
• FIG. 11 shows another embodiment of a partial control unit.
• FIG. 12 shows the circuit diagram for an interconnection unit in a further developed embodiment.

The pumps 3 and 4 are driven by the internal combustion engine 1 by means of the shaft 2. The actuator 5 of the pump 3 is connected to a pump actuator piston 6. Which is displaceable in a pump actuating cylinder 7 and divides it into two pressure chambers 8 and 9. The pump 3 feeds into a delivery line 12, from which lines 13 and 14 are fed via delivery branch lines to the pressure chamber 9, in which a spring 11 is arranged. The pressure chamber 8 is acted upon by a hydraulically controlled pump adjustment valve, which controls the application of the pressure chamber 8.

The pump 4 feeds into a delivery line 15. The setting member 16 of the pump 4 is connected to a pump actuating piston 17 which is displaceable in a pump actuating cylinder 18 and divides it into two pressure chambers 19 and 20, a spring 21 being arranged in the pressure chamber 20. This pressure chamber 20 is connected to the delivery line 15 via a branch line 321 and a further branch line 22. The application of pressure to the pressure chamber 19 is controlled via a hydraulically controlled pump adjustment valve 23. Both pumps 3 and 4 are arranged in a common housing 24.

Two further pumps 25 and 26 are driven by shaft 2. The pumps 25 and 26 are constant pumps.

A delivery branch line 28 branches off from the delivery line 12, which leads to a sub-control unit 27 in which the delivery branch line 28 is divided into two sub-lines 29 and 30. Each of these two sub-lines 29 and 30 leads to a directional control valve 31 and 32, respectively, the directional control valve 31 being hydraulically controlled and being pressurized via a pressure transmitter control line 33 by an arbitrarily actuatable control pressure transmitter 92 arranged in the driver's cab of the excavator. In the same way, the hydraulically controlled directional valve 32 is acted upon by control pressure via a pressure transmitter control line 34, the pressure transmitter control line 34 leading to an arbitrarily actuatable further control pressure transmitter 93 which is also arranged in the driver's station. The directional control valves 31 and 32 each act as a measuring throttle point, through which a throttled current is conducted from the partial line 29 to the line 35 or from the partial line 30 to the line 36. In the other position, the directional valve 31 connects the line 35 to the return line 37 and in the same way in the other switching position, the directional valve 32 connects the lines 36 and 38 to one another, the two return lines 37 and 38 leading together to the return branch line 39.

The line 35 leads to an adjustable throttle point 40 with a throttle valve body 41, the rear side of which by a spring 42 and is acted upon by the control pressure present in a control pressure line 53. A line 43 extends from the adjustable throttle point 40 and branches into two lines 44 and 45, each of which leads to a pressure chamber 46 and 47 of the two working cylinders 48 and 49, which are connected in parallel on the excavator for lifting, in this Case the assigned consumers are.

In an analogous manner, the line 36 leads to the adjustable throttle point 50, which has a throttle valve body 51, the rear side of which is acted upon by a spring 52 and by the pressure present in a control line 53. A line 53 extends from the adjustable throttle point 50 and is divided into two lines 54 and 55, of which the line 54 leads to the pressure chamber 56 of the working cylinder 48 and the line 55 leads to the pressure chamber 57 of the working cylinder 49.

A check valve 58 opening towards the working cylinder 48 is arranged in the line 54. Between this and the working cylinder 48, a line 59 is connected to the line 54, which leads to a combined pressure-limiting and lowering brake valve 60, the discharge of which leads via line 61 and line 62 to the return partial line 39. Furthermore, between the check valve 48 and the working cylinder 48, a line 63 is connected to the line 54, in which a check valve 64 is arranged and, on the other hand, is connected to the line 62.

In an analogous manner, a check valve 68 is arranged in the line 44 and a line 65 is connected between this and the working cylinder 48, in which a check valve 66 is arranged, which on the other hand is also connected to the line 52. Furthermore, a line 69 is connected to the line 44 between the check valve 68 and the working cylinder 48, which leads to a combined pressure-limiting and lowering brake valve 70, the drain line 71 of which is connected to the line 62. The control pressure chamber of the combined pressure limiting and lowering brake valve 70 is connected via line 72 to line 54 before the check valve 58. In the same way, the control pressure chamber of the combined pressure limiting and lowering brake valve 60 is connected via line 73 to line 44 before the check valve 68. If line 54 carries pressure, the control pressure chamber of the combined pressure limiting and lowering brake valve 70 is loaded by this pressure and thus the combined pressure limiting and lowering brake valve is relieved of delivery pressure, so that it opens at more or less low pressure in line 44. Conversely, the same applies to the combined pressure limiting and lowering brake valve 60 if the line 44 is pressurized before the pressure blow valve 68.

These valves 58, 64, 60, 70, 68, 66 are combined in a control unit 74 which is attached directly to the working cylinder 48.

An analogous valve arrangement is provided in the control device 75, which is attached to the working cylinder 49.

Within the partial control unit 27, a line 76 is connected to the line 53, which leads to a check valve 77. Likewise, a line 78 is connected to line 43, which leads to a check valve 79. The two check valves 77 and 79, on the other hand, are connected to the partial control pressure line 80, to which the pressure spaces behind the throttle valve bodies 41 and 51 are also connected.

A relief check valve 94 opening towards the line 35 is arranged in the throttle valve body 41. In the same way, a relief check valve 95 opening towards the line 36 is arranged in the throttle valve body 51. The control pressure line 80 leads to a control pressure line 81 to which a control pressure line 83 is connected. A branch line 82 is connected to the delivery line 12. The branch line 82 and the control pressure line 83 lead to an overall control unit 85, from which a return line 84 emerges, which is connected to the return line 39. The overall control unit 85 is attached to the working cylinder 86, which serves to actuate the bucket of the excavator. The overall structure of the circuit of the overall control unit 85 is analogous to the sum of the partial control unit 27 and the control unit 74. Two directional control valves 87 and 287 are provided, of which the directional control valve 287 is acted upon by a control line 88 from an arbitrarily actuatable control pressure transmitter 90, which in is arranged in the vicinity of the control pressure transmitters 92 and 93, which act on the pressure transmitter control lines 33 and 34. Accordingly, the directional control valve 87 is controlled by means of a control pressure line 89, which in turn is also connected to an arbitrarily actuable control pressure transmitter 91, which is arranged spatially in the vicinity of the control pressure transmitter 90, 92 and 93.

The two directional control valves 287 and 87 are constructed in such a way that they exert an adjustable throttle effect in intermediate positions and each act as a measuring throttle point at which a predetermined pressure drop is maintained, that is to say that when the throttle point is expanded, an increased current is supplied . Each of these two directional valves 87 and 287 is followed by an adjustable throttle point 96 or 97, behind which a branch line leading to the control pressure partial line 83, each with a check valve 100 or 101, branches off at a connection point 98 or 99.

The return line 39 leads to a main return line 102 which leads directly into the housing 24 of the pumps 3 and 4 and to which a prestressed storage tank 103 is connected.

From the delivery line 15, the pump 4 starts, branch lines 104, 105, 106 branch off, of which the branch line 104 leads to a working cylinder 107, which serves to buckle the arm of the excavator, and the branch line 105 leads to a hydraulic motor 108 for the travel drive and the branch line 106 to a hydraulic motor 109 for the swing drive motor of the excavator. The overall control units 110 and 111 are constructed in the same way as the overall control unit 85, that is to say they each contain two directional control valves 112 or 113 or 114 or 115 and in each case an adjustable throttle point 116 or 117 or 118 or 119, the Control pressure chamber of the directional valve 112 is acted upon by an arbitrarily actuatable control pressure transmitter 120 and, accordingly, the control pressure chamber of the directional valve 113 is acted upon by a control pressure transmitter 121 and the control pressure chamber of the directional valve 114 is acted upon by a control pressure transmitter 122 and, accordingly, the control pressure chamber of the directional valve 115 is actuated by a control pressure transmitter 123 is acted upon. The return partial lines 124 and 125 starting from the overall control units 110 and 111 lead to a return branch line 126 which is connected to the main return line 102 as well as the return line 127. The lines 106 and 127 are connected to a four-port / three-position directional valve 128, which is hydraulically operated by the two Control pressure transmitter 129 and 130 is controlled and either either connects the connection 131 of the hydraulic motor 109 to the delivery line 106 and the other connection 132 of the hydraulic motor 109 to the return line 127 or vice versa connects the delivery line 106 to the connection 132 and the return line 127 to the connection 131 . Here too, an additional control unit 133 is provided, which is attached directly to the hydraulic motor 109 and in which two check valves 134 and 135 and two pressure relief valves 136 and 137 and connections 138 and 139 are provided for a control pressure line 140, between the control pressure line 40 and the connections 139 and 138 check valves 141 and 142 are arranged.

The control pressure line 150 is connected to the control pressure line 81 assigned to the pump 3. The control pressure line 150 leads to a branch line 152, in which a throttle point 153 is arranged and which leads to a pressure chamber of the hydraulically controlled pump adjustment directional valve 10. The opposite pressure chamber of the same is connected via branch line 154 to line 14, which is supplied with the delivery pressure in delivery line 12 of pump 3.

A current regulator 155 is also connected to the line 150, the output of which leads into the interior of the housing 24 of the pumps 3 and 4.

A pressure limiting valve 157 is connected to the line 152 between the throttle point 153 and the control pressure chamber of the pump adjustment directional valve 10.

A line 158 extends from the line 13, which leads to a connection 159 of the pump adjusting valve 10, so that pressure medium conveyed through this line 158 and the connection 159 by the pump 3 via the delivery line 12, the lines 13, 158 and the connection 159 can be guided through the pump adjustment valve 10 into the pressure chamber 8.

The lines 158 and 150 are connected by a connecting line 160, in which a throttle point 161 is arranged.

Control pressure lines 162, 163 and 164 extend from the control units 110 and 111 and from the control device 133, which are connected to a control pressure line 165 to which the line 166 is connected, to which in turn the line 167 with the throttle point 168 is connected and on which the current regulator 169 is connected. The line 170 emanating from the throttle point 168 leads to a pressure chamber of the hydraulically controlled pump adjustment directional valve 23 of the pump 4, the opposite pressure chamber of which is connected to the line 22 via the connection 171. A pressure relief valve 172 is connected to line 170.

The connection 173 of the pump adjustment directional valve 23 is connected to the line 321 via the line 174. A connection line 175, in which a throttle point 176 is arranged, is arranged between the lines 174 and 166.

An interconnection control line 177 is connected to the control pressure line 81 and an interconnection control line 178 is connected to the control pressure line 165, these two control lines leading to the interconnection unit 179. In this a four-port / two-position directional valve 182 is arranged, which is hydraulically controlled and has two control pressure chambers on each side, each control pressure chamber on the one hand being assigned an equally large control pressure chamber on the other side, but it is not necessary that the two each control pressure chambers lying on one side have the same diameter. Starting from the delivery line 12, a branch line 180 leads to the interconnection unit 179, and likewise a branch line 181 leads from the delivery line 15 to the interconnection unit 179. The two lines 180 and 181 are connected to the four-position / two-way valve 182 in such a way that in the drawing shown Position of the same, the lines 180 and 181 are connected to one another and these lines are blocked in the other switching position of the same. The control pressure lines 177 and 178 are connected to the two other connections of the four-port / two-position directional control valve 182 in such a way that in the switch position shown the lines 177 and 178 are connected to one another and are closed in the other switch position.

In the interconnection unit 179, two pressure relief valves 184 and 185 are also arranged, of which the pressure relief valve 184 serves to secure the delivery line 12 and is connected to this via line 180, while the pressure relief valve 185 serves to secure the delivery line 15 and via line 181 this is connected.

In this case, the line 180 acted upon by the delivery pressure of the pump 3 is connected to a control pressure chamber and the line 177 acted upon by the control pressure assigned to the pump 3 is connected to the control pressure chamber of the same size arranged on the side opposite this control pressure chamber. Furthermore, the line 181 acted upon by the delivery pressure of the pump 4 is connected to a control pressure chamber which is on the same side as the pressure chamber acted upon by the line 180, and the line 178 acted upon by the control pressure assigned to the pump 4 is connected to one on the opposite side Connected side pressure control chamber, which is the same size as the control pressure chamber acted on by line 181, the two pressure chambers, which are connected to the lines 177 and 178 pressurized by control pressure, are arranged on the side of the directional control valve 182, on which the compression spring 186 is arranged is.

The constant pump 25 draws in via the line 187 from the housing 24 of the pumps 3 and 4 and delivers into a line 188 which leads to an adjustable throttle point 189, the setting member 190 of which is operatively connected to the setting member of the internal combustion engine 1. Before the throttle point 189, a pressure limiting valve 193 is connected to the line 188 via a line 191, in which a filter 192 is arranged, the outlet of which is connected to a line 194, which in turn is connected to the line 195 behind the throttle point 189 forms the continuation of line 188 and leads to further consumers, which are no longer shown in the drawing.

A controlled pressure relief valve 196 is also connected to line 194, the control pressure of which is determined via line 197 by the pressure upstream of throttle point 189. The line 189 emanating from the pressure relief valve 196 leads to a throttle point 199 and the line 200 emanating therefrom leads to the tank 156 via a pressure relief valve 201. The pressure relief valve 196 and the throttle point 199 are connected in series and, in parallel, a further pressure relief valve 202 is connected, which maintains the pressure upstream of the pressure relief valve 196 constant. The important thing is that the pressure drop at the throttle point 189 controls the pressure relief valve 169, which in turn controls the flow to the throttle point 199.

A limit pressure control line 203 branches off from the line 198 between the pressure limiting valve 196 and the throttle point 199 and a second limit pressure line 204 branches off from the line 200. The line 203 branches into two lines 205 and 206, each of which opens into a control pressure chamber of the pump adjustment directional valve 10 or 23, on the same side on which the delivery pressure of the associated pump 3 or 4 acts. Two lines 207 and 208 branch off from line 204, each of which leads to the other side of the pump adjustment directional valve 10 and 23, respectively, which is acted upon by a spring.

The mode of operation is as follows: If the internal combustion engine 1 drives the pumps 3, 4, 25 and 26 and all control pressure transmitters 93, 92, 91, 90, 120, 121, 122, 123, 130, 129 are not actuated, the pumps are in the zero stroke position and do not promote. No consumer is charged. If the control pressure transmitter 92 is now actuated, the directional control valve 31 is actuated and opens, so that it establishes a connection between the delivery line 12 and the line 44 to the working cylinder 48, the adjustable throttle point 40 opening. At the same time, the check valve 79 opens, so that the partial control pressure line 80 and thus the control pressure line 81 is pressurized.

Since the directional valve 31 acts as a measuring throttle point, the pressure in line 35 and thus the pressure in line 43 and thus also the pressure in line 78 and in the partial control pressure line 80 and in the control pressure line 81 is lower than the pressure in the delivery branch line 28 and the delivery line 12. The pressure in the delivery line 12 acts via the delivery branch lines 13, 14 and 154 on one side of the pump adjustment directional valve 10 and the pressure in the control pressure line 81 acts via lines 150, 151, 152 on the other side of this servo control valve, on which the spring also acts. The spring is designed so that the pump adjustment valve 10 responds to a very specific pressure difference between the pressures in the branch lines 154 and 152, for example to a pressure difference of 20 bar. The result of this is that the actuator 5 of the pump 3 is adjusted by means of the pump adjusting valve 10 via the pump adjusting piston 6 in such a way that it promotes a flow of flow which generates the predetermined pressure drop at the directional valve 31 acting as a measuring throttle point. That is: if the setting of the directional control valve 31 is changed by changing the setting of the control pressure transmitter 92, the pump 3 is also set to a different flow rate and specifically to a flow rate such that, in turn, the predetermined pressure drop arises at this directional control valve 31 acting as a measuring throttle point.

• Werden gleichzeitig zwei, zwei verschiedenen Verbrauchern zugeordnete Steuerdruckgeber betätigt, beispielsweise der Steuerdruckgeber 92 und der Steuerdruckgeber 90, so werden zwei Wegeventile - in dem genannten Fall das Wegeventil 31 und der Arbeitszylinder 86 - gleichzeitig geöffnet und somit gleichzeitig zwei Verbraucher, nämlich hier einerseits die beiden Arbeitszylinder 48 und 49 und andererseits der Arbeitszylinder 86, mit der gleichen Pumpe 3 verbunden. Dabei wirkt in den beiden Arbeitszylindern 48 und 49 der gleiche Druck. Jedoch ist es unwahrscheinlich, daß zufällig auch in dem Arbeitszylinder 86 der gleiche Druck wirkt. Vielmehr wird einer der Verbraucher höher belastet sein und somit einen höheren Druck benötigen. Angenommen, der Druck in dem Arbeitszylinder 86 ist höher als der Druck in den Arbeitszylindern 48 und 49, dann steht an der Anschlußstelle 98 ein höherer Druck an als in der Leitung 43 mit der Folge, daß das Rückschlagventil 79 geschlossen sein wird und die Steuerdruckleitung 80, 83 durch Öffnen des Rückschlagventiles 101 von dem an der Anschlußstelle 98 anstehenden Druck beaufschlagt wird. Da von diesen Steuerleitungen auch die Rückseiten der Drosselventilkörper 41 und 241 beaufschlagt sind, vor dem jeweiligen Drosselventilkörper in der Leitung 35 bzw. 240 jedoch unterschiedliche Drücke herrschen, wird an den Drosselstellen 40 und 96 eine unterschiedliche Drosselwirkung erzeugt, d. h. bei dem Arbeitszylinder 48, 49, der den kleineren Druck erzeugt, wird durch die einstellbare Drosselstelle 40 ein so großes Druckgefälle erzeugt, daß vor dieser einstellbaren Drosselstelle 40 in der Leitung 35 und damit in der Förderzweigleitung 28 und damit in der Förderleitung 12 und damit in der Zweigleitung 82 ein so hoher Druck erzeugt wird, wie ihn der Arbeitszylinder 86 benötigt, wobei an der einstellbaren Drosselstelle 96 infolge des Druckes in der Leitung 240 unter der Wirkung des Steuerdruckes in der Steuerdruckleitung 83 eine entsprechend geringere Drosselwirkung erzeugt wird, da bei diesem der Verbraucherdruck, der auf den Drosselventilkörper 241 wirkt, groß genug ist, um die einstellbare Drosselstelle 96 ganz zu öffnen, so daß an dieser kein Druckgefälle auftritt.

The adjustable throttling points 40, 50, 96 or 97 and 116 or 117 have the following effect:

• If two or two different consumers are assigned control pressure transmitters at the same time If, for example, the control pressure transmitter 92 and the control pressure transmitter 90 are activated, two directional control valves - in this case the directional control valve 31 and the working cylinder 86 - are opened at the same time and thus two consumers simultaneously, namely here the two working cylinders 48 and 49 and the working cylinder 86 , connected to the same pump 3. The same pressure acts in the two working cylinders 48 and 49. However, it is unlikely that the same pressure also happens to work in the working cylinder 86. Rather, one of the consumers will be more heavily loaded and will therefore need more pressure. Assuming that the pressure in the working cylinder 86 is higher than the pressure in the working cylinders 48 and 49, then there is a higher pressure at the connection point 98 than in the line 43, with the result that the check valve 79 will be closed and the control pressure line 80 , 83 is acted upon by the pressure at the connection point 98 by opening the check valve 101. Since these control lines also act on the rear sides of the throttle valve bodies 41 and 241, but different pressures prevail in front of the respective throttle valve body in the lines 35 and 240, a different throttling effect is generated at the throttle points 40 and 96, that is to say in the working cylinders 48, 49 , which generates the lower pressure, is generated by the adjustable throttle point 40 such a large pressure drop that before this adjustable throttle point 40 in the line 35 and thus in the delivery branch line 28 and thus in the delivery line 12 and thus in the branch line 82 is so high Pressure is generated, as required by the working cylinder 86, whereby a correspondingly lower throttling effect is generated at the adjustable throttle point 96 as a result of the pressure in the line 240 under the effect of the control pressure in the control pressure line 83, since in this case the consumer pressure acting on the throttle valve body 241 looks big enough to be the once The throttle point 96 can be opened fully, so that there is no pressure drop across it.

The current supplied by the pump 3 is thus divided between the two consumers - in the present case on the one hand the working cylinders 48, 49 and on the other hand the working cylinder 86 - in proportion to the opening width of the adjustable throttle points.

The check valves 58 and 68 act as pipe break protection. This means that if a leak occurs in the delivery line 12 or the delivery branch line 28 or the branch line 82 or another line connected to this and the pressure escapes, the consumer is connected by actuating the associated control pressure transmitter and thus opening the associated directional valve is not able to sink back under load. For example, when lifting under load and thus the working cylinders 48 and 49 are under pressure and the delivery line 12 breaks, the check valve 58 closes. The liquid present in the working cylinders 48 and 49 is thus enclosed and clamped in, so that no unwanted movement can occur , since the combined pressure limiting and lowering brake valves 60 and 70 are closed, since there is no pressure in the lines 53 and 43, and thus the combined pressure limiting and lowering brake valves 60 and 70 are not open.

However, if the directional control valve 31 is opened by actuating the control pressure transmitter 92, pressure is present in the line 43, so that pressure medium flows through the lines 43, 44 into the working cylinders 48 and 49. The pressure present in line 43 is also present in the control pressure chamber of the combined pressure-limiting and lowering brake valve 60 via line 73, so that it is open. This means that the pressure medium flow flowing out of the pressure chambers 56 and 57 of the working cylinders 48 and 49 can be unhindered through the line 54 into the line 59, the combined pressure-limiting and lowering brake valve 60, the lines 61 and 62 and into the return branch line 39 and thus into the Drain the main return line 102. The speed of movement of the pistons in the working cylinders 48 and 49 should be determined by the extent to which the directional control valve 31 is open. If, as a result of external forces, the pistons in the working cylinders 48 and 49 want to lead this current, they draw in liquid with the result that the pressure in the line 44 and thus in the line 43 drops. Thus, the pressure in the control pressure chamber of the combined pressure limiting and lowering brake valve 60 is also reduced via line 73, so that it closes to the extent that the pressure is reduced, that is to say that in the combined pressure limiting and lowering brake valve 60, a throttling effect is generated, which throttles the current flowing out of the pressure spaces 56 and 57, so that the throttling effect of the movement speed of the pistons in the working cylinders 48 and 49 is braked. The combined pressure limiting and lowering brake valves 60 and 70 are also controlled by the pressure in the lines 59 and thus 54 or 69 and thus 44. The combined pressure limiting and lowering brake valves 60 and 70 thus also act as a safeguard against impermissibly high pressure in the working cylinders 48 and 49. That is, if too high a pressure occurs as a result of overloading or intermittent loading, it opens depending on the direction of loading due to the too high Pressure either the combined pressure limiting and lowering brake valve 60 or the combined pressure limiting and lowering brake valve 70, so that these combined pressure limiting and lowering brake valves 60 and 70 also act as overload relief pressure relief valves, even if none of the control pressure transmitters 92 and 93 is actuated.

Especially in such a case of drainage of pressure medium through one of the combined pressure-limiting and lowering brake valves 60 and 70, but also in any other case of suction into one of the pressure chambers 46, 47 or 56, 57, respectively, the associated check valve 64 or 66 opens so that the respectively opened check valve 64 or 66 and the line 62 and the return branch line 39, the main return line 102 can be reloaded from the storage tank 103.

If the control pressure transmitter 92 has been actuated and thus the directional control valve 31 has been opened, and as a result line 43 has been pressurized via the delivery line 12 and the lines 28, 29, 35, and the actuation of the control pressure transmitter 92 is now ended and the directional control valve 31 is thus in brought the relief position, the adjustable throttle point 40 completes completely. This would have the consequence that the last effective pressure remains in line 43 and thus holds the combined pressure limiting and lowering brake valve 60 in the open position via line 73. However, when both control pressure transmitters 92 and 93 are closed, both combined pressure limiting and lowering brake valves 60 and 70 should also be closed. Therefore, in the throttle valve body 41, a relief check valve 94 opening towards the pump 3 is provided, which in the said operating state has the consequence that the line 43 is relieved via the relief check valve 94 when the adjustable throttle point 40 is closed.

The valves on the other side of the control unit 74 or the corresponding valves in the control unit 85 or 100 or 111 act in an analogous manner.

If, by acting on the control pressure transmitter 92 in the pressure transmitter control pressure line 33, such a pressure is generated that the directional control valve 31 opens very wide, this would result in such a strong current in the lines 29, 35 and thus also 28 and the delivery line 12 to maintain the required pressure drop on the directional valve 31 required that the pump 3 alone cannot promote this current. In this state, the interconnection unit 179 takes effect. As already mentioned, to control the pump 3 by the pump adjustment valve 10, the spring acting on it is designed such that a specific pressure drop occurs at the directional valve 31 acting as a measuring throttle point, for example a pressure drop of 20 bar. The compression spring 186 on the four-port / two-position valve 182 is designed such that this valve responds at a lower pressure drop, for example a pressure drop of 15 bar, between the delivery line 12 and the control pressure line 81. The four-port two-position valve 182 is designed such that when the movement of its slide body begins, the interconnection control lines 177 and 178 are first connected to one another, with the result that the pump 4 is pivoted out so far that the same pressure is present in the delivery line 15 as in FIG Delivery line 12, wherein when no consumer is connected to the pump 4, this pressure is generated upstream of the throttle point 176. When the slide body is moved further in the four-port / two-position valve 182, the branch lines 180 and 181 are then also connected to one another by the valve 182, so that the flow of the pump 4 is additionally conveyed through the four-port / two-position valve 182 into the delivery line 12 of the pump 3, the pump 4 now swings out so far that it generates exactly the flow rate that is required to generate the required pressure drop together with the flow rate of the pump 3 at the directional control valve 31 acting as a measuring throttle point.

Although the consumers are directly protected by the combined pressure limiting and lowering brake valves 60, 70 and the corresponding pressure limiting valves on the other consumers, it is necessary to additionally protect the pump 3 and the entire system by means of a pressure limiting valve, which prevents an inadmissibly high pressure Part of the system is damaged. For practical reasons, this pressure relief valve is also installed in the interconnection unit 179, namely the pressure relief valve 184 is connected to the delivery line 12 via the branch line 180 and, in a corresponding manner, the pressure relief valve 185 is connected to the delivery line 15 via the branch line 181 to protect the pump 4. Opening one of these pressure relief valves has the disadvantage that this pressure medium is used to discharge at the highest possible pressure, which means that a lot of energy is destroyed in this pressure relief valve. This is inevitable for the reduction of short pressure surges. However, it is advantageous if it can be avoided that this pressure relief valve remains open for a longer time. For this purpose, the pump 3 is assigned the pressure relief valve 157, which is set to such a low pressure that it opens when there is a pressure in the control pressure line 81 which corresponds to the pressure drop at the through the directional control valve 31 or 32 or 86 or 87 given throttling point is below the response pressure of the pressure relief valve 184, so that the pressure relief valve 157 opens before opening the pressure relief valve 184 and thereby limits the maximum possible pressure in the branch line 152, with the result that with a slight increase in the pressure in the line 154 Pump adjustment valve 10 increases the pressure in the pressure chamber 8 of the pump actuating cylinder 7 and thereby adjusts the pump 3 to a smaller stroke and thus a smaller flow rate, whereby it can be expected that after this control process caused by the increase in the control pressure increases, the pressure in the delivery line 12 as a result of the reduced Delivery flow is reduced and thus the response of the pressure relief valve 184 can be avoided.

In an analogous manner, a corresponding pressure relief valve 172 is assigned to the pump 4, which responds to the pressure in the line 166 and opens before the pressure relief valve 185 opens.

With this pressure relief valve, however, only protection against pressure peaks is achieved during the control process of the pump. There is no protection against overloading the internal combustion engine 1. This is achieved by the limit load control 230. The pump 25 delivers through the line 188 to the adjustable throttle point 189, the setting member 190 of which is operatively connected to the setting member of the internal combustion engine 1. The line 195 behind the throttle point leads to the control pressure transmitters 90, 91, 92, 93, 120, 121, 122, 123, 129 and 130. The externally controlled pressure relief valve 196 is connected to this line 195 and detects the pressure via line 197 is influenced in line 188 before the adjustable throttle point 189. The pressure relief valve 196 is set to the pressure drop which is to prevail at the throttle point at the respectively provided operating speed. If this pressure drop is present, the pressure relief valve 196 is closed. If the pressure drop is smaller than intended, the pressure relief valve 196 opens and leads a flow to the downstream throttle point 199, at which a pressure drop now also arises and this pressure drop is transmitted via the limit pressure lines 203 and 204 as a pressure difference to the two sides of the pump adjustment directional valve 10 and the delivery branch line 13 activated. It is thereby achieved that when both pumps 3 and 4 deliver to at least one consumer and the limit load control 230 intervenes, both pumps 3 and 4 are withdrawn proportionally, that is to say in equal measure, so that when two driven working cylinders are superimposed, they move out the direction of movement resulting from the movement superposition is not changed. The speeds of movement of two consumers switched on are in the same relationship to each other as the openings of the directional control valves, which act as measuring throttles. If the speed of the internal combustion engine 1 is reduced as a result of overloading the internal combustion engine 1, the pressure drop at the adjustable throttle point 189 will decrease and the pressure relief valve 196 will thus open and thus a pressure drop will occur at the throttle point 199, which acts on both pump adjustment directional control valves 10 and 23 to the same extent. The setting of both pumps 3 and 4 is thus changed in the direction of a smaller stroke volume per revolution, but only to the extent that the pressure drop at the throttle point 199 and the pressure drop at the directional control valve acting as a measuring throttle of the consumer which is switched on keep the balance. If one of the pumps 3 or 4 tends to run ahead, it immediately receives a counter signal which adjusts the two pressure drops again. In this way, the pressure drops at the directional valves acting as a measuring throttle of the two consumers are kept the same, with the result that the absolute quantity changes at these directional valves acting as a measuring throttle, but not the ratio of the quantities to one another and thus the ratio of the movement speeds to one another.

The pressure relief valve 202 serves to protect the pump 25. The pressure relief valve 193 additionally protects the pump 25 in the event that the adjustable throttle point 189 is closed too far or completely. In this case, the pressure medium flows via line 188, line 191, pressure relief valve 193 into line 194.

To charge the pressure accumulator 103, the pump 26 is used, which pumps to the steering device of the excavator, which is no longer shown in the drawing. The return from the steering device still has sufficient pressure to charge the storage container 103. For this purpose, the line 239 coming from the steering device is connected to the line 102.

The pump 25 sucks from the housing 24, in which the two pumps 3 and 4 are arranged, in order to ensure that an exchange of pressure medium takes place in the housing 24. The pressure medium flowing back from the steering through line 239 flows, as far as it is excess, via the pressure relief valve 201 into the unpressurized container 156. The volume of the storage container 103 is dimensioned such that leakage losses and volume differences on the two sides of the pistons can be compensated for even when several consumers are actuated in the same direction.

FIG. 11 shows a modified embodiment of a partial control unit. The partial control unit 270 corresponds to the partial control unit 27 with the only difference that instead of the two directional control valves 31 and 32, which form the two measuring throttle points in the partial control unit 27, a single four-port / three-position directional control valve 231 is provided, which by means of the two control pressure transmitters 92 and 93 via the Pressure transmitter control line 33 or 34 can be controlled and, in the neutral position shown in the drawing, closes off the branch conveyor line 28 and connects the lines 35 and 36 to one another and, in a controlled position, connects the branch conveyor line 28 to the line 35 and at the same time connects the line 36 to the return branch line 39 and in the other modulated position, the feed branch line 28 connects to the line 36 and at the same time connects the line 35 to the return line 39.

The additional control unit 133 has a slightly different structure and a different mode of operation like the control units 85 or 110 or 111. The four-port / three-position valve 128 is not only controlled by the two control pressure transmitters 129 and 130, but it is also on the opposite side of the controlled side from the delivery pressure in the line 131 leading to the consumer 132 is acted on, so that when valve 128 is actuated via one of control pressure transmitters 129 or 130, an equilibrium state is established on valve slide of valve 128. If the pressure at the consumer drops, the valve is opened further so that a greater current flows to the consumer and the pressure at the consumer is increased due to the consumer detection.

FIG. 12 shows a modified embodiment of an interconnection unit.

The interconnection unit 279 essentially corresponds to the interconnection unit 179, the four-port, two-position directional valve 282 essentially corresponding to the valve 182. To the valve 282 are connected in the same way as to the valve 182, a branch line 180 originating from the delivery line 12 and opposite thereto an interconnection control line 177 originating from the control line 81, and a branch line 181 originating from the delivery line 15 is also connected and to the opposite one Control pressure chamber, an interconnection control line 178 starting from the control pressure line 166 is connected.

In contrast to the valve 182, the valve 282 on the side opposite the compression spring 286 has a third control pressure chamber 234 which is connected via a line 233 to the limit load control element 230 in such a way that when the limit load control element 230 acts on the pump adjustment directional control valves 10 and 23 Signal, by which the actuator 5 of the pump 3 and the actuator 16 of the pump 4 are adjusted in the direction of a smaller stroke volume, prevents the interconnection valve 282 from opening. A pressure is thus exerted by the limit load control element 230 via the control line 233 on the additional pressure space 234, which loads the valve member of the interconnection valve 282 in the direction of the closed position. The interconnection unit 279 should only connect the two delivery lines 12 and 15 of the two pumps 5 and 4 to one another if one of the two pumps is set to the greatest possible delivery flow and the pressure drop at the directional control valve 32 acting as a measuring throttle point drops below the intended value. This pressure drop at the directional control valve 31 acting as a measuring throttle point is also smaller when the limit load controller 230 intervenes, with the result that the stroke volume of the pump 4 is set to a smaller value via the actuator 5 than the pressure drop at the measuring throttle point. An interconnection unit of the embodiment shown in FIG. 4 responds to each drop in the pressure drop at the directional control valve 31 acting as a measuring throttle, with the result that the delivery lines 12 and 15 are also connected when the drop is caused only by the intervention of the limit load regulator 230 . In order to avoid this disadvantage, by applying pressure to the third pressure chamber 234, the switching pressure difference at which the interconnection unit 279 performs the interconnection function is reduced to the same extent as the pressure drop at the directional control valve 31 acting as a measuring throttle point is reduced by the signal of the limit load control device 230.

It can easily be seen that such a drive system can be expanded without difficulty by connecting further additional consumers to the delivery line, the return line and the control pressure line, each via a control unit. With this system, it is possible to apply several arbitrary consumers simultaneously from one pump, even if the loads are different.

Claims (13)

1. A hydrostratic drive system comprising an adjustable pump (3), the delivery line (12) of which is connected to a plurality of consumers (48, 49, 86, 107, 108, 109) each of which has an inlet terminal and an outlet terminal and which can each be individually operated by means of a direction control valve (31, 32, 87, 287, 112, 113, 114, 115) which throttles in intermediate positions, wherein the adjusting member (5) of the pump (3) is connected to a pump control piston (6) which is displaceable in a pump control cylinder, wherein the input and output of pressure to and from the pump control cylinder (7) are controlled by means of a pump adjusting direction control valve (10) which is provided with a valve spool, one side of which is acted on by the pressure in the delivery line (12) of the pump upstream of the direction control valve (31, 32, 86, 87,112,113,114,115), and the other side of which is acted on by a spring and by the pressure in a control pressure line (81), and wherein the control pressure line (81) is connected to the conveyor lines (43, 53, 45, 55), in each case between one of the direction control valves (31, 32, 287, 87, 112, 113, 114, 115) and the assigned consumer (48, 49, 86, 107, 108, 109), by way of control pressure branch lines (74, 78) which contain non-return valves (77, 79, 100, 101) opening towards the control pressure branch line (74, 78), characterised by the combination of the following features :

a) between each direction control valve (31, 32, 287, 87, 112, 113, 114, 115) and the assigned consumer (48, 49, 86,107,108, 109), the conveyor branch line (35, 43, 36, 53) in question in each case contains an adjustable throttling point (40, 50, 96, 97, 116, 117, 118, 119), the adjusting member of which is acted on, in the opening direction, by the pressure which prevails in the conveyor branch line (35, 36) downstream of the direction control valve (31, 32, 87, 287, 112, 113, 114, 115), the adjusting member being acted upon on the opposite side by a spring and by a control pressure which prevails in a control pressure chamber, and the adjusting members of all the throttling points (40, 50, 96, 97, 116, 117, 118, 119), which are each assigned to a consumer, being acted upon by the same control pressure which prevails in a control pressure chamber provided with a pressure relief means (115),

b) the control pressure chambers of the adjusting members of all the throttling points (40, 50,96. 97,116,117,118,119) are connected to the control pressure line (81) which is connected to the pump adjusting direction control valve (10), and

c) each terminal of each consumer (48, 49, 86, 107, 108, 109) which can be operated as an input terminal, is assigned a direction control valve (31, 32, 87, 287,112,113,114,115) followed by a throttling point (40, 50, 96, 97, 116, 117, 118, 119).

2. A drive system as claimed in Claim 1, characterised in that each of the two terminals of each consumer (48, 49, 86, 107, 108, 109) is connected to a conveyor branch line (43, 53) which starts from an adjustable throttling point (40, 50, 96, 97,116,117,118,119), and to a return line (59, 69) which contains a combined pressure limiting and braking lowering valve (60, 70), one control pressure chamber of which is connected to the conveyor branch line which leads to the other terminal of the same consumer (48, 49, 86, 107, 108, 109).

3. A drive system as claimed in Claim 1 or Claim 2, wherein for the pressure relief of the control pressure line (81) an exhaust is provided to a container, characterised in that the exhaust line (150) which serves as exhaust contains a flow regulating valve (155).

4. A drive system as claimed in one of the preceding Claims, characterised in that for the pressure relief of the conveyor branch line (43, 53) downstream of the throttling point (40, 50, 96, 97,116,117,118,119), a connection between this conveyor branch line (43, 53) and the line (35, 36) which leads to the assigned throttling point (40, 50, 96, 97, 116, 117, 118, 119) contains a non-return valve (94, 95) which opens towards this line (35, 36).

5. A drive system as claimed in Claim 4 having a non-return valve (94, 95) arranged in the throttling member (40, 50, 96, 97, 116, 117, 118, 119), characterised in that the non-return valve which is arranged in the throttling point (throttling member) (40, 50, 96, 97, 116, 117, 118, 119) is the non-return valve (94, 95) arranged in the connection between the conveyor branch line (43, 53) and the line which leads to the throttling point (40, 50, 96, 97, 116, 117, 118, 119).

6. A drive system as claimed in Claim 1, or preferably Claim 2, characterised in that a branch return line (39, 84,124; 125, 127) leads from each consumer (48, 49, 86, 107, 108, 109) ; that all the branch return lines (39, 84, 124, 125, 127) are connected to a collecting return line (102) ; that the pump (3) sucks in from its housing (24) ; and that the collecting return line (102) is connected to the housing (24) of the pump (3), and a preloaded pressure storage means (103) is connected to the collecting return line (102).

7. A drive system as claimed in one of the preceding Claims, characterised in that two consumers (48 and 49), connected in parallel, are connected to a throttling point (40 or 50).

8. A drive system as claimed in one of the preceding Claims, characterised in that all the throttling points (96, 97 and 116, 117 and 118, 119 and 40, 50) which are assigned to a consumer (86 or 107 or 108 or 109), or to a consumer group (48, 49), are combined in a control unit (27) ; and that the control unit (27) is arranged directly at the location of the assigned consumer (86, or 107, or 108, or 109), or the assigned consumer group (48, 49).

9. A drive system as claimed in Claims 2 and 8, characterised in that the valve group which consists of the non-return valves (58 and 68) and pressure limiting and braking lowering valves (60, 70), is arranged, together with the throttling points (96, 97 and 116, 117 and 118, 119) in an overall control unit (85, 110, 111).

10. A drive system as claimed in Claim 1 comprising two pumps, wherein at least one of these two pumps (3, 4) is assigned a plurality of consumers (48 or 49 or 86 or 107 or 108 or 109), characterised in that the delivery lines (12 and 15) and the control pressure lines (81 and 165) of the two pumps are connected to an interconnecting device (117) which, when a pressure difference exists between the delivery line (12, 15) and the assigned control pressure line (61, 165) which is smaller than the pressure difference intentionally provided in the direction control valve (31 or 32 or 87 or 287 or 112 or 113 or 14 or 115), interconnects the delivery lines (12 and 15) and interconnects the control pressure lines (81 and 165).

11. A drive system as claimed in one of the preceding Claims, characterised in that a load limiting control device (230) is provided which triggers a pressure signal in the event of a reduction in the speed of the drive shaft (2) of the pump (3, 4) ; and that the pressure signal acts on the pump adjusting direction control valve (10, 23).

12. A drive system as claimed in Claim 1, characterised in that the delivery line (12) is connected to a pressure limiting valve (184) and the control pressure line (81) is connected to a pressure limiting valve (157), where a throttling point (153) is located between the control pressure line (81) and the pressure limiting valve (157), and where the pressure limiting valve (157) which is connected to the control pressure line (81), is set at a lower pressure than the pressure limiting valve (184) which is connected to the delivery line (12).

13. A drive system as claimed in one of the preceding Claims, characterised in that a consumer (109) is assigned an additional control unit (133) which contains a four-terminal/three-position direction control valve (128) which is connected on one side to the conveyor line (106) and the return line (127) and, on the other side, to two lines (131 and 132), each of which leads to a respective terminal of the consumer (109), where each side of the valve (128) has two pressure chambers, one of which is connected to a control pressure generator (129, 130), operable at will, and the other of which is connected to one of the two lines (131 and 132) which lead to the consumer (109), where the operated control pressure generator (129 or 130) is connected at one side of the valve (128), and that one of the two lines (131 and 132) which lead to the consumer (109) which is acted upon by pressure, is connected at the other side of the valve (128) ; and where each of the two lines (132, 131) which lead to the consumer (109) is connected to a branch line, both of which branch lines lead to the collecting control pressure line (140), each of these two branch lines containing a non-return valve (141, 142) which opens towards the collecting control pressure line (140).

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