ES2732624T3 - Hydraulic system for the supply of a pressure medium to a hydraulic cylinder with three separate active surfaces on which a pressure medium and a procedure for the operation of the hydraulic system can be applied - Google Patents

Abstract

Hydraulic system with a hydraulic cylinder (2), which has at least three separate active surfaces (48, 50, 52) on which a pressure medium can be applied; where a pressure means can be applied to a first active surface (48) and a second active surface (50) for a displacement of a piston / rod element (12) of the hydraulic cylinder (2), in its direction of displacement (8); wherein an accumulator switching valve (42) is provided, by means of which a pressure means of a charged accumulator (38) can be applied to the second surface (50) in the direction of travel (8); and where a loading valve (46) is provided, by means of which a first working space (14) of the hydraulic cylinder (2), delimited by the first active surface (48), can be connected so that it can be driven fluid, with a second working space (16) of the hydraulic cylinder (2), delimited by the second active surface (50); and where a hydraulic machine (30) is provided, whereby a pressure means can be applied respectively to the first active surface (48) or to a third active surface (52) of the hydraulic cylinder (2) in a closed hydraulic circuit ; wherein a pressure means can be applied to the third active surface (52) for the movement of the piston / rod element (12) against the direction of travel (8); and wherein the accumulator switching valve (42) is connected in a flow path of the accumulator (36) between the accumulator (38) and the second working space (16); and wherein the discharge valve (46) is connected in an intermediate branch (44) of the flow path of the accumulator (36), between the switching valve of the accumulator (42) and the second working space (16); and wherein the intermediate branch (44) is connected to a first flow path (24), so that flow can be conducted, between the first work space (14) and the hydraulic machine (30); and wherein the flow path of the accumulator (36) extends from the second working space (16) to the accumulator (38) made as a high pressure accumulator; and where from the flow path of the accumulator (36) a branch (39) is conducted to a second flow path (40), which extends from the hydraulic machine (30) to a third work space (18) delimited by the third active surface (52); and where a non-return valve (41) is arranged in the branch (39), which blocks in the direction towards the second flow path (40).

Description

DESCRIPTION

Hydraulic system for the supply of a pressure medium to a hydraulic cylinder with three separate active surfaces on which a pressure medium and a procedure for the operation of the hydraulic system can be applied

Area of the invention

The present invention refers to a hydraulic system according to claim 1.

Furthermore, the invention refers to a procedure for the operation of the hydraulic system according to the invention, in accordance with the claim on the method 12.

Background of the present invention

In known hydraulic systems, particularly in those for the supply of a pressure medium to a hydraulic cylinder with three separate active surfaces on which a pressure medium can be applied, which are used for example as adjustment devices for wind installations , hydraulic presses or plastic injection machines, generally in the integration of additional functions, such as emergency operation as well as for compensation of leaks and volume differences, a low pressure accumulator is required, from which a machine Hydraulics can recover a pressure medium, or a medium of excess pressure can be taken from the cylinder and / or from the system, which is subject to a high space requirement, high manufacturing costs and / or costs of functioning. In addition, costly corrosion protection must be implemented in the known solutions in the hydraulic cylinder used, particularly in the case of synchronization cylinders with an internal construction, which results in high production costs.

Document D 102012 012 142 A1 describes a hydraulic adjustment device, which has an adjustment function for a working mode and a special operating mode. To a double acting adjustment cylinder, provided for this, a working pressure medium can be applied and to fulfill the adjustment function in the special operating mode it can be connected with a pressure medium accumulator, the which has a compressed gas separated from the working pressure medium.

EP 2420681 A2 describes a linear hydraulic drive with a hydraulic cylinder designed with three pressure chambers, whose active surfaces are adjusted with each other so that in a fast march and in a force impact, a hydraulic cylinder drive by machine that supplies a medium of pressure, works in approximately the same speed range / moment of rotation.

Disclosure of the present invention

On the contrary, the present invention aims to create a hydraulic system for the supply of a pressure means of a hydraulic cylinder with three separate active surfaces on which a pressure medium can be applied, which is more economical to manufacture and / or to operate

Said object is solved by a hydraulic system with the characteristics of claim 1.

Furthermore, an object of the present invention is to operate in a simple manner the hydraulic system according to the invention.

Said object is solved by a method for operating the hydraulic system according to the invention, with the characteristics of the related claim on the process.

Advantageous improvements of the invention are described in the related claims. A hydraulic system according to the present invention contains a hydraulic cylinder, which has at least three separate active surfaces on which a pressure means can be applied. There, a pressure means for a displacement of a piston / rod element of the hydraulic cylinder, in its direction of travel, can be applied to a first active surface and a second active surface. An accumulator switching valve is provided in the hydraulic system, by means of which a pressure means of a charged accumulator can be applied to the second active surface in the direction of travel, particularly during emergency operation for rapid displacement and / or maximum of the piston element / rod.

An advantage of the hydraulic system according to the present invention is that the invention according to the invention that a pressure means is applied to the second active surface from the charged accumulator for the displacement of the piston / rod element, allows a design Simple special construction of the hydraulic cylinder and therefore a saving of manufacturing costs.

The hydraulic system according to the invention can be advantageously used, for example, in wind installations for the adjustment of the hydraulic passage, particularly of a rotor or of the blades of a rotor. Particularly during an emergency operation in which the rotor must be turned from the wind, then, for the displacement of the piston / rod element in the direction of the preferential position, a pressure means is additionally applied to the first active surface, to the second active surface, which allows a quick adjustment.

According to the invention, a charging valve is provided, whereby, especially during a charging mode in which the accumulator is charged with a pressure means, a first working space of the hydraulic cylinder, delimited by the first active surface , can be connected so that fluid can be conducted, with a second working space of the hydraulic cylinder, delimited by the second active surface. In this way the accumulator can be charged with a pressure medium, particularly after the execution of the emergency operation. During the charging mode, the piston / rod element advantageously travels completely against the direction of travel, to drive back a pressure means from the second working space to the hydraulic circuit, when the accumulator switching valve It is closed and the load valve open.

Another advantage of the hydraulic system according to the invention is that a low pressure accumulator from which a pressure medium can be recovered by the hydraulic machine, can be considerably smaller in size compared to those of similar hydraulic systems. The accumulator, from which a pressure medium is applied to the second active surface, is advantageously realized as a high pressure accumulator. Advantageously, then, the hydraulic system can be used in addition to the aforementioned wind installations, also in hydraulic presses or plastic injection machines, and in general in hydraulic systems with a high pressure accumulator and a low pressure accumulator .

Advantageously, during normal operation, a negative pressure can be generated in the first working space, particularly a vacuum, especially because of a displacement of the piston / rod element in its direction of travel and because the second space of The work is closed in normal operation due to the energized state and thereby closed the accumulator switching valve. In normal operation, when the second workspace is closed, the piston / rod element can move in or against the direction of travel. Thus, in the second workspace there is also no humidity during normal operation, with which is no longer necessary then there a corrosion treatment whose implementation is highly expensive and laborious, which is why the costs of the hydraulic system according to the invention can be further reduced.

According to the invention, a hydraulic machine is provided, by which a pressure means can be applied respectively to the first active surface or to a third active surface of the hydraulic cylinder in a closed hydraulic circuit; where a pressure means can be applied to the third active surface for the displacement of the piston / rod element, against the direction of travel. In this way, the first workspace and the third workspace can be activated respectively directly. In particular, during normal operation only a pressure means for the displacement of the piston / rod element in the direction of travel is applied to the first active surface, and a pressure means for displacement is applied to the third active surface of the piston / rod element against the direction of travel.

The hydraulic machine can be driven with a variable speed and / or particularly with a reversible direction of rotation and / or be rotatable. As already stated above, it is advantageous that during a normal operation of the hydraulic cylinder a pressure medium cannot flow into the second working space. Therefore, during normal operation a synchronized behavior of the hydraulic cylinder is achieved, since advantageously the first active surface has the same dimensions as the third active surface. The second active surface may differ in the size of the other two active surfaces, particularly being larger than the first active surface or the third active surface. In the emergency operation, a differential behavior of the hydraulic cylinder is presented.

Advantageously, the hydraulic cylinder, made particularly cylindrically hollow, has a guide pivot in its housing, particularly with a cylindrical shape, on which the piston / rod element is mounted axially movable. In this case, the first workspace is delimited by the guide pivot and the piston / rod element, and the second workspace is delimited by the guide pivot and the piston / rod element and the housing. Additionally, the third workspace is delimited by the element piston / rod and housing. The special conformation of the hydraulic cylinder, according to the invention, allows an execution thereof that saves space, and thus a reduction of the required space.

Particularly, the piston / rod element has a fundamentally annular radial collar, in an open end section, or in a position between a closed end section of the piston / rod element and the open end section. Advantageously, the respective work spaces delimited by the piston / rod element, in particular the second work space and the third work space are delimited by the radial collar, or by their annular surfaces.

Particularly, the piston / rod element projects with its closed end outward of a final section of the housing, oriented essentially in the direction of travel, from which a cylinder head is formed.

The guide pivot can be arranged in a final section of the housing, which moves away from the direction of travel, from which a cylinder base is formed. In particular, the guide pivot is fixedly connected to the housing or is made as a single piece with the housing.

The first active surface may be disposed in the final section of the piston / rod element, particularly cylindrically shaped hollow, in an inner edge; where the first active surface is oriented essentially towards the base of the cylinder and moves away from the direction of travel.

The second active surface may be arranged at an outer edge of the piston / rod element, particularly shaped as an annular radial collar; where the second active surface is oriented essentially towards the base of the cylinder and moves away from the direction of travel.

The third active surface may be arranged on an outer edge of the piston / rod element, particularly shaped as an annular radial collar; where the third active surface is oriented essentially towards the cylinder head and the direction of travel.

According to the invention, the accumulator switching valve is connected in a flow path of the accumulator, between the accumulator and the second working space; and the charging valve is connected in an intermediate branch of the flow path of the accumulator, between the switching valve of the accumulator and the second working space. Additionally, the intermediate branching is connected to a first flow path, so that flow can be conducted, between the first work space and a source of a pressure medium. This ensures a simpler change in operating mode, for example, between normal operation and emergency operation, or between emergency operation and charging mode. Advantageously, the accumulator switching valve is open not energized and closed with power supply. In this way, during a power outage, emergency operation can be executed and for example a rotor of a wind installation can be automatically turned from the wind.

Advantageously, the second workspace is subdivided into a first chamber and a second chamber, by means of a separation wall made fluid tight, or by means of a plate or a steel plate. Thus, in the loading mode, a total withdrawal of the piston / rod element is not necessary, since the negative pressure generated in the first chamber during normal operation, or the vacuum generated is effectively separated of a pressure medium present in the second chamber through the separation wall. Thus, the charging mode can end in virtually any position without negatively influencing subsequent normal operation. Another advantage of the separation wall is that, because the pressure medium is kept away from the low pressure / vacuum in the first chamber, a release of gases of moisture and / or air or dissolved gas in the medium can be avoided of pressure and with it a cavitation. Advantageously, the separation wall is made in the form of a ring and is arranged on the guide pivot in an axially movable manner. There, particularly during emergency operation, the separation wall can be displaced by an application of a pressure means from the accumulator in the direction of travel, especially together with the piston / rod element.

In particular, during loading mode, the separation wall can be moved against the direction of travel by means of an application of a third active surface pressure means by means of the piston / rod element, directly or by means of pressure that is present in the first chamber. It is also advantageous that the separation wall is maintained in its respective position by a replacement device and / or through a frictional force between the separation wall and the housing. Thus, during normal operation, a travel path of the piston / rod element in the direction of travel is marked by a travel stop on the cylinder head side, in the housing, and against the direction of travel is marked by a folding stop on the base side of the cylinder, in the housing, or by a position of the separation wall.

The replacement device can be made as a spring element, where polyurethane is used as a material.

Advantageously, the separation wall can be moved against the direction of travel by means of a replacement device, in particular independently of the piston / rod element. In this way, the accumulator can be charged with a pressure medium, regardless of the piston / rod element, in particular after executing the emergency operation.

The replacement device can be made as a spring element, where a gas charge of the first chamber, especially with nitrogen, acts as a spring element.

The second active surface may be arranged on an annular outer edge of the separation wall; where the second active surface is oriented essentially towards the base of the cylinder and moves away from the direction of travel.

Advantageously, a discharge valve is provided on the separation wall, particularly shaped as a non-return valve, which allows the passage in the direction of the accumulator and through which a pressure means circulates from the first chamber to the Second chamber With this, an amount of leakage from the hydraulic cylinder, which has been aspirated due to the low pressure / vacuum in the first chamber, particularly during charging mode, can be transported back to the hydraulic circuit. In this case, the replacement device is made as a spring element composed particularly of polyurethane.

Advantageously, a pressure monitoring device is provided, by means of which a pressure in the accumulator is monitored. The pressure monitoring device is particularly provided in the high pressure accumulator and / or in the low pressure accumulator. This ensures high safety against leaks from the hydraulic cylinder. Therefore, in addition to progressive leaks, the hydraulic system is able to automatically reset itself to an original state, and thereby delay a service call. In particular, with the above-described execution of the charging mode, an amount of leakage can be transported back to the hydraulic circuit.

A method according to the invention for operating the hydraulic system according to the present invention comprises the following steps:

close and / or keep the accumulator switching valve closed, and close and / or keep the charging valve closed for normal operation execution;

open and / or keep the accumulator switching valve open and open and / or keep the load valve open for the execution of an emergency operation for the particularly rapid and / or maximum movement of the piston / rod element;

close and / or keep the accumulator switching valve closed and open and / or keep a load valve open for the execution of a restart of the hydraulic system after the execution of the emergency operation, with the charge of the accumulator, particularly for the displacement of the piston / rod element against the direction of travel.

An advantage of the process according to the invention is that with it the hydraulic system according to the invention operates in a simple and efficient manner and therefore costs are saved.

Advantageously, after the emergency operation, the charging mode is executed. In this way, after the emergency operation the accumulator, particularly the high pressure accumulator, can be recharged with a pressure medium. Then normal operation can be executed again. Brief description of the drawings

Several exemplary embodiments / an exemplary embodiment of the present invention are explained in detail below by schematic drawings. They show:

Figure 1, a hydraulic system according to the invention, according to a first exemplary embodiment, with a hydraulic cylinder represented in a longitudinal section, in a closed hydraulic circuit.

Figure 2, a hydraulic system according to the invention, according to a second exemplary embodiment, with a hydraulic cylinder represented in a longitudinal section, in a closed hydraulic circuit, during normal operation.

Figure 3, a hydraulic system according to the invention, according to Figure 2, during normal operation; Y

Figure 4, a hydraulic system according to the invention, according to Figure 2, during a charging mode. Detailed description of the forms of execution represented

The exemplary embodiment of the hydraulic system 1 according to the invention, shown in Figure 1, contains a hydraulic cylinder 2, which has a special construction design according to the invention and can be identified in its type of differential construction as a cylinder of synchronization

In a housing 4 of the hydraulic cylinder 2, in a final section of the housing 4 which essentially departs from a direction of travel 8, a cylindrical shaped guide pivot 6 is arranged, from which a cylinder base 10 is formed. The guide pivot 6 is made here as a single piece with the housing 4, alternatively thereto, it can be fixedly connected with the housing 4.

A piston / rod element 12 in the form of a hollow cylinder is mounted axially movable on the guide pivot. A first work space 14 is delimited by the guide pivot 6 and the piston / rod element 12. A second work space 16 is delimited by the guide pivot 6 and the piston / rod element 12 and the housing 4. A third Working space 18 is delimited by the piston / rod element 12 and the housing 4. The piston / rod element 12 projects, in the position shown, with a final section 20 closed outside an end section of the housing 4, oriented essentially in the direction of travel 8, from which a cylinder head 22 is formed.

From the first workspace 12 a first flow path 24 extends to a source of a pressure medium 26. The source of a pressure medium 26 is made as a pump unit, which has a drive 28 of a controllable electric motor, here with variable speed and with reversible direction of rotation, and a hydraulic machine 30 that is shaped here as a hydraulic pump. Parallel to the hydraulic machine 30, a low pressure accumulator 32 is connected with fluid passage, from which the hydraulic machine 30 can aspirate a pressure medium respectively by means of a feedback valve 34 formed as a non-return valve.

From the second workspace 16 extends a flow path of the accumulator 36 to an accumulator 38, realized as a high pressure accumulator. From a flow path of the accumulator 36 a branch 39 is conducted to a second flow path 40, which extends from the hydraulic machine 30 to a third work space 18. On the branch 39 a non-return valve 41 is arranged, the which blocks in the direction towards the second flow path 40.

In the flow path of the accumulator 36, between the second working space 16 and the accumulator 38 there is arranged a switching valve of the accumulator 40, here a directional control valve 2/2 which is closed not energized. Between the second working space 16 and the switching valve of the accumulator 42, by means of a loading valve 46, an intermediate branch 44 of the flow path of the accumulator 36 can be connected with the first flow path flow 24. The loading valve 46 is in this case performed as a closed non-energized 2/2 directional control valve.

A first active surface 48 is arranged in a closed end section 20 on an inner edge of the piston / rod element 12. The first active surface 48 is oriented essentially towards the base of the cylinder 10 and outside the direction of travel 8.

The second active surface 50 is disposed on an outer edge of the piston / rod element 12, here realized as an annular radial collar; wherein the second active surface 50 is oriented essentially towards the base of the cylinder 10 and outside the direction of travel 8. The radial collar is arranged in a final section 51 of the piston / rod element 12.

The third active surface 52 is disposed on the outer edge of the piston / rod element 12, here realized as an annular radial collar; wherein the third active surface 52 is oriented essentially towards the cylinder head 22 and towards the direction of travel 8.

The functionality and the different modes of operation of the hydraulic system according to the invention are described below.

In normal operation, for a displacement of the piston / rod element 12 in its direction of travel 8, a pressure means is applied to the first active surface 48 through the first path of flow 24 by means of the hydraulic machine 30. The pressure means present in the third working space 18 is transported back to the hydraulic machine 30 through the flow path of the accumulator 36, the branch 39 and the second flow path 40. In this case, the switching valve of the accumulator 42 is energized and thereby closed and the charging valve 46 is not energized and thereby closed. A displacement of the piston / rod element 12 against the direction of travel 8 is performed analogously to the same connection of the valves 42, 46.

Since in normal operation, the switching valve of the accumulator 42 is energized and thereby closed, due to the displacement of the piston / rod element 12 in the direction of travel 8, a low pressure or a vacuum is generated in the First workspace 16.

In an emergency operation, the accumulator switching valve 42 is not energized and thereby open, whereby a pressure means is applied to the second active surface 50 from the accumulator 38 and the piston / rod element 12 is moves in its direction of travel 8. When the switching valve of the accumulator 42 is connected not energized during normal operation, in addition to the first active surface 48, a pressure means is applied to the second active surface 50 - the first surface activates 48, as described above, with a pressure means from the source of a pressure means 26, or from the hydraulic machine 30. In the event of a power failure, which results in a failure of the drive 28, for example of the electric motor, the switching valve of the accumulator 42 is therefore disconnected practically automatically and only a means of accumulator pressure is applied dor 38 to the second active surface 50. In this way, in emergency operation, the hydraulic cylinder 2 can still be adjusted without drive 28.

After the execution of the emergency operation, the charging mode must take place, in order to recharge the accumulator 38 with a pressure means, and to transport a pressure medium from the second work space 16 back to the hydraulic circuit . In this case, the switching valve of the accumulator 42 is energized and thereby closed and the charging valve 46 is energized and thereby open. Thus, in the movement of the piston / rod element 12 against its direction of travel 8, a pressure means is transported from the hydraulic machine 30 through the second flow path 40 to the third work space 18. In in this case, a pressure means is transported from the first work space 14 and a pressure means from the second work space 16 back to the hydraulic circuit; wherein a pressure medium is transported from the second work space 16 to the intermediate branch 44 along the flow path of the accumulator 36 via the charging valve 46 to the second flow path 24 and to the low pressure side of the machine hydraulic 30. The pressure medium from the first working space 14 is transported through the first flow path 24 to the low pressure side of the hydraulic machine 30. From the high pressure side of the hydraulic machine 30 a pressure means through the branch 39 and the non-return valve 41 traversed with fluid in the direction of the flow, to the accumulator 38, thus recharging the accumulator 38. Then a normal operation can again be carried out.

Figure 2 shows a second example of execution of the hydraulic system according to the invention, in normal operation.

The hydraulic elements represented in the hydraulic circuit in addition to Figure 1 are standard elements that do not require further description here.

Unlike the first exemplary embodiment shown in Figure 1, the hydraulic cylinder 2 of the second exemplary embodiment has a separation wall 54 in the second workspace 16, whereby it is subdivided into a first chamber 56 arranged adjacently to the open end section 51, and a second chamber 58 disposed adjacent to the base of the cylinder 10.

The low pressure / vacuum that arises in normal operation due to the displacement of the piston / rod element 12 in the direction of travel 8 when not energized, and thus closed, the switching valve of the accumulator 42, is then generated in the first camera 56.

A travel path of the piston / rod element 12 in the direction of travel 8 is marked in normal operation by a travel stop on the cylinder head side, in the housing 4, and against the direction of travel 8 It is marked by a position of the separation wall 54.

The separation wall 54 is in an intermediate position between the travel stop on the cylinder head side in the housing 4, and a withdrawal stop on the base side of the cylinder in the housing 4, and effectively separates a means of pressure present in the second chamber 58 of the active pressure / vacuum in the first chamber 56.

In the separation wall 54 a discharge valve 60 is provided, shaped as a non-return valve, which allows the passage in the direction towards the accumulator 38 and through which a pressure means can flow from the first chamber 56 to the second chamber 58.

Figure 3 shows the second embodiment of the hydraulic system according to the invention, described in Figure 2, in emergency operation.

In the emergency operation described in reference to Figure 1, here, a pressure means is applied from the accumulator 38 to the second active surface 50, formed on an annular outer edge of the separation wall 54, in order to move with greater force the piston / rod element 12 in the direction of travel 8. Here, the separation wall 54 moves axially on the guide pivot 6, until it is housed in the piston / rod element 12 or in its collar annular radial, as shown in Fig. 3. Then the separation wall 54 travels together with the piston / rod element 12 in the direction of travel 8 until the piston / rod element 12 is located in the side travel stop of the cylinder head in the housing 4.

Figure 4 shows the second embodiment of the hydraulic system according to the invention, described in Figure 2, in the loading mode.

Unlike the first example of execution of the hydraulic system 1 according to the invention, represented in Figure 1 and described above, in the case of the second example of execution of the hydraulic system 1 according to the invention, it is no longer in the loading mode a total withdrawal of the piston / rod element 12 is necessary. In the second exemplary embodiment, in the loading mode, the separation wall 54 travels from the piston / rod element 12 against the direction of travel 8 and thereby In each position of the separation wall 54, an effective separation of a pressure medium in the second chamber 58 is guaranteed from the low pressure / vacuum generated in the first chamber 56 during normal operation. In this way, a travel path of the piston / rod element 12 and thereby an extension of the travel of the piston / rod element 12 against the direction of travel 8 can be selected relatively freely during the loading mode. An amount of leakage of the hydraulic cylinder 2, possibly generated, that has been aspirated because of the low pressure / vacuum in the first chamber 56, can be transported back to the hydraulic circuit through the discharge valve 60, particularly during the charging mode A hydraulic system with a special hydraulic cylinder has been revealed, particularly with a synchronization cylinder with a differential construction design, which has three separate active surfaces on which a pressure medium can be applied | In normal operation operable with a synchronization characteristic, in emergency operation, the cylinder develops a differential characteristic. This is advantageous in a use of the hydraulic system according to the invention, for example in wind installations for adjusting the hydraulic passage of a rotor or its rotor blades.

List of reference symbols

1 Hydraulic system

2 Hydraulic cylinder

4 Hydraulic cylinder housing

6 Guiding Pivot

8 Direction of travel

10 Cylinder base

12 Piston / rod element

14 First workspace

16 Second workspace

18 Third workspace

20 Closed end section of the pivot / rod element

Cylinder head

First flow path

Source of a pressure medium

Drive

Hydraulic machine

Low pressure accumulator

Feedback Valve

Accumulator flow path

Accumulator

Branch

Second flow path

Non-return valve

Accumulator switching valve Intermediate branch

Loading valve

First active surface

Second active surface

Open end section of the pivot / rod element Third active surface

Separation wall

First camera

Second chamber

Discharge valve

Claims (12)

1. Hydraulic system with a hydraulic cylinder (2), which has at least three separate active surfaces (48, 50, 52) on which a pressure medium can be applied; where a pressure means can be applied to a first active surface (48) and a second active surface (50) for a displacement of a piston / rod element (12) of the hydraulic cylinder (2), in its direction of displacement (8); wherein an accumulator switching valve (42) is provided, by means of which a pressure means of a charged accumulator (38) can be applied to the second surface (50) in the direction of travel (8); and where a loading valve (46) is provided, by means of which a first working space (14) of the hydraulic cylinder (2), delimited by the first active surface (48), can be connected so that it can be driven fluid, with a second working space (16) of the hydraulic cylinder (2), delimited by the second active surface (50); and where a hydraulic machine (30) is provided, whereby a pressure means can be applied respectively to the first active surface (48) or to a third active surface (52) of the hydraulic cylinder (2) in a closed hydraulic circuit ; wherein a pressure means can be applied to the third active surface (52) for the displacement of the piston / rod element (12) against the direction of travel (8); and wherein the accumulator switching valve (42) is connected in a flow path of the accumulator (36) between the accumulator (38) and the second working space (16); and wherein the discharge valve (46) is connected in an intermediate branch (44) of the flow path of the accumulator (36), between the switching valve of the accumulator (42) and the second working space (16); and wherein the intermediate branch (44) is connected to a first flow path (24), so that flow can be conducted, between the first work space (14) and the hydraulic machine (30); and wherein the flow path of the accumulator (36) extends from the second working space (16) to the accumulator (38) made as a high pressure accumulator; and where from the flow path of the accumulator (36) a branch (39) is conducted to a second flow path (40), which extends from the hydraulic machine (30) to a third work space (18) delimited by the third active surface (52); and where a non-return valve (41) is arranged in the branch (39), which blocks in the direction towards the second flow path (40). 2. Hydraulic system according to claim 1, wherein during normal operation a low pressure can be generated in the second workspace (16). 3. Hydraulic system according to claim 1 or 2, wherein during normal operation of the hydraulic cylinder (2) a pressure medium cannot flow to the second working space (16). 4. Hydraulic system according to one of the preceding claims 1 to 3, wherein the hydraulic cylinder (2) has in its housing (4) a guide pivot (6), on which the piston / rod element (12) is mounted axially displaceable; wherein the first work space (14) is delimited by the guide pivot (6) and by the piston / rod element (12); and wherein the second work space (16) is delimited by the guide pivot (6) and by the piston / rod element (12) and the housing (4); and where a third work space (18) is delimited by the piston / rod element (12) and the housing (4). 5. Hydraulic system according to one of the preceding claims 1 to 4, wherein the accumulator switching valve (42) is open not energized. 6. Hydraulic system according to one of the preceding claims 1 to 5 wherein the second work space (16) is subdivided into two chambers (56, 58), by means of a separation wall (54) made fluid tight. 7. Hydraulic system according to claim 6, wherein the separation wall (54) is made in the form of a ring and is arranged on the guide pivot (6) in an axially movable manner; and wherein the separation wall (54) can be moved from the accumulator (38) in the direction of travel (8) by an application of a pressure means, or by an application of a pressure means to the third active surface (52) can be displaced by the piston / rod element (12) directly or indirectly against the direction of travel. 8. Hydraulic system according to claim 6 or 7, wherein the separation wall (54) can be moved against the direction of travel (8) by a replacement device. 9. Hydraulic system according to one of claims 6 to 8, wherein a discharge valve (60) is provided in the separation wall (54) which allows the passage in the direction towards the accumulator (38). 10. Hydraulic system according to claim 8 or 9, wherein the replacement device is arranged in the first chamber (56) and is made as a gas charge or as a spring element essentially composed of polyurethane. 11. Hydraulic system according to one of claims 1 to 10, wherein in an emergency operation, a charged pressure accumulator means (38) can be applied to the second active surface (50) in the direction of travel ( 8). 12. Method for operating the hydraulic system according to one of claims 1 to 11, characterized by the following steps: close and / or keep the accumulator switching valve (42) closed and close and / or keep the charging valve (46) closed for the execution of normal operation for the displacement of the piston / rod element (12) in or against of the direction of travel (8); open and / or keep the accumulator switching valve (42) open and open and / or keep the charging valve (46) open for the execution of an emergency operation for the displacement of the piston / rod element (12) in the direction of travel (8); I close and / or keep the accumulator switching valve (42) closed and open and / or keep a load valve open (46) for the execution of a restart of the hydraulic system after the execution of the emergency operation, with the charge of the accumulator (38).