Background

[0001] The invention relates to converting pressure and/or flow in a pressure medium-operated system, and especially to a method and arrangement for converting pressure and for arranging a charging cycle.

[0002] Pressure converters may be necessary in pressure medium- operated systems in situations, for instance, where there is a need to optimize motion rates and/or forces in working phases. The pressure, surface area and flow ratios of a pressure medium-operated system and its components are typically used in pressure converters. Publication FI20090383 discloses a method for converting the pressures in a pressure medium-operated system by using valve structures and other corresponding components known per se. In said method, the pressure of one or more actuators is converted with one or more pressure converters to differ from the system pressure. In the solution, one or more pressure converter cylinders are switched on or off as a set limit value controlling the valves is exceeded or undershot during the movement of one or more actuators requiring a conversion of the motion rate or force. However, the solution requires a connection to both the inlet and return channel of the actuator, and the counter-pressure in the return channel may affect the charging of the pressure converter, which limits the possible applications of the solution.

Brief description of the invention

[0003] Thus, the object is to develop a new method and arrangement for converting pressure and for arranging a charging cycle. The object of the invention is achieved by a method and pressure converted that are characterised by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

[0004] The invention is based on adapting the position of a piston and/or piston rod and/or a part coupled to them and moving with them to switch on at least the conversion and/or charging cycle of the pressure converter.

[0005] The method and system of the invention provide the advantage that the pressure converter can be connected to one channel, i.e. pressure line, because the charging cycle does not require external control. Brief description of the figures

[0006] The invention will now be described in more detail in connection with preferred embodiments and with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a pressure converter;

Figure 2 is a schematic view of a method for converting pressure and for arranging a charging cycle in a pressure medium system;

Figure 3 is a schematic view of a pressure medium system comprising a pressure converter;

Figure 4 is a schematic view of another pressure medium system comprising a pressure converter;

Figure 5 is a schematic view of yet another pressure medium system comprising a pressure converter; and

Figure 6 is a schematic view of one more pressure medium system comprising a pressure converter.

Detailed description of the invention

[0007] Publication FI20090383 discloses a pressure conversion solution and various applications, in which the conversion of pressure and/or flow could be advantageous.

[0008] Figure 1 is a schematic view of a pressure converter. The pressure converter 7 comprises at least one converter cylinder 1 and at least one converter valve 3 as well as means for switching on a conversion and charging cycle of the pressure converter 7. The converter cylinder 1 may comprise any double-acting pressure medium cylinder known per se, such as a hydraulic or pressurized-air cylinder, or a pressure medium cylinder known per se with at least two chambers. The conversion cycle may comprise a pressure increase cycle or volume-flow increase cycle, for instance.

[0009] The pressure converter 7 may be adaptable to convert pressure to the extent of the ratio of the surface areas of at least one converter cylinder to an external pressure medium-operated actuator 2, such as a hydraulic cylinder, hydraulic motor, or some other one- or double-acting pressure medium-operated actuator. The means for switching on the conversion and charging cycle of the pressure converter may comprise at least one moving part in the converter cylinder 1 , which is adaptable to move in relation to the cylinder barrel of the converter cylinder 1 . The moving part may preferably comprise a converter cylinder piston 8 and/or piston rod 9 and/or at least a separate switching part 12 connected to the piston 8 or piston rod, the embodiments of which are described in greater detail in connection with the other figures. The conversion and charging cycles of the pressure converter may then be adapted to be connected to the position of the moving part 8, 9 in such a manner that the position of the moving part 8, 9 determines the conversion and charging cycle of the pressure converter 7. This way, the piston 8 and/or piston rod 9 of the converter cylinder 1 controls directly or indirectly by its own movement the pressure conversion operation, on one hand, and the charging operation of the pressure converter, on the other hand. The charging of the pressure converter 7 refers to the return of the piston 8 or piston rod 9 of the converter cylinder 1 to a position that permits the start of a new conversion cycle. The pressure medium may comprise pressurized liquid, such as hydraulic liquid known per se, or pressurized gas, such as pressurized air, for example.

[0010] Figure 2 is a schematic view of a method for converting pressure and for arranging a charging cycle in a pressure medium system. In the method, the pressure supplied to at least one external actuator is converted 21 to the extent of the ratio of the surface areas of at least one converter cylinder. Further, in the method, the control of the conversion and charging cycles of the pressure converter is switched 22 with means for controlling the conversion and charging cycles of the pressure converter, the means comprising at least one moving part in at least the converter cylinder, the moving part being adaptable to move in relation to the cylinder barrel of the converter cylinder and the position of the moving part being adaptable to determine the control of the conversion and charging cycles of the pressure converter.

[0011] In an embodiment, the method initiates a conversion cycle of the pressure converter, in which the pressure and/or volume flow supplied to at least one actuator is converted to the extent of the ration of the surface areas of at least one converter cylinder in response to at least one part of the converter cylinder reaching a position in relation to the cylinder barrel of the converter cylinder, which position switches on the initiation of the conversion cycle. The conversion cycle and various embodiments to implement and/or start/switch it are shown elsewhere in this specification and the related figures.

[0012] In an embodiment of the method, a charging cycle of the pressure converter, in which the piston of the converter cylinder is returned to the position from which the next conversion cycle can be started at the begin- ning of the work movement of the actuator, is stopped in response to the fact that at least one moving part of the converter cylinder reaches a position in relation to the cylinder barrel of the converter cylinder, which position switches on the stopping of the charging cycle. The return of the piston 8 and/or piston rod 9 and/or separate switching part 12 connected to them to the position, in which the pressure converter 7 can start a new conversion cycle, may directly or indirectly switch on the stopping of the charging cycle. This position of the piston 8 and/or piston rod 9 and/or separate switching part 12 connected to them may be called the initial position of the converter cylinder 1 and piston 8 and/or piston rod 9 and/or separate switching part 12 connected to them. In the embodiments of Figures 3 to 6, the piston 8 of the converter cylinder 1 is then on the left in the figure and the pressure converter 7 is charged and ready to start a new conversion cycle.

[0013] The method may further comprise steps and features that are described elsewhere in this specification, in connection with Figures 1 and 3 to 6 and the related description, for instance.

[0014] Figure 3 is a schematic view of a pressure medium system comprising a pressure converter 7. In the embodiment according to Figure 3, when the actuator 2 works in direction +, i.e. toward the right in Figure 3, a directional control valve 6 is arranged in the first position thereof in such a manner that the pressure medium flows from channel P to channel A and through a first check valve 4 to the actuator 2, to the side of the larger surface area, i.e. piston, and to the side of the smaller surface area of the converter cylinder 1 , i.e. to the side of the piston rod of the converter cylinder 1 . In this description, the expression 'piston side' refers to the side of the larger surface area of the piston, unless otherwise stated. In normal one-rod pressure medium cylinders with piston rods, this typically means the side opposite to the piston-rod side. However, in some embodiments, the work surface areas of different sides of the piston have been made to differ from each other in some other manner known per se.

[0015] As load increases in the actuator 2, the pressure in channel A increases. The converter valve 3 is adapted to stop the entry of the pressure medium to the side of the larger surface area of the converter cylinder 1 , i.e. in the embodiment of Figure 3, for example, to the piston 8 side of the converter cylinder 1 , when the pressure in channel A is lower than the set value of the converter valve 3. Correspondingly, the converter valve 3 is adapted to allow the pressure medium to flow to the side of the larger surface area of the converter cylinder 1 , i.e. to the piston 8 side, when the pressure in channel A increases under the influence of the load to the actuator 2 to be equal to the set value of the converter valve 3 or higher. Because the same pressure prevails on both work surfaces of the converter cylinder 1 , the pressure moves the piston 8 and piston rod 9 in direction +, i.e. to the direction of the smaller surface area, under the influence of the surface area difference between the work surfaces of the converter cylinder 1 .

[0016] In the embodiment of Figure 3, in the wall of the converter cylinder 1 , at least one pressure converter channel opening (not shown) connecting to a second check valve 5 is formed in such a manner that after the piston closes said pressure conversion channel/s, the oil exiting from the side of the smaller surface area only exits to the actuator 2, which initiates the conversion cycle, in the embodiment of Figure 3, the pressure increase cycle. The conversion cycle continues after the piston 8 passes the opening of the pressure conversion channel as long as the pressure caused by the load in channel A remains as high as or higher than the set value of the converter valve 3. During the conversion cycle, the pressure supplied to the actuator 2 increases to the extent of the ratio of the surface area of the converter cylinder 1 . This can, thus, be called the conversion cycle of the pressure converter 7. The position of the piston 8 in relation to the cylinder barrel 1 1 of the converter cylinder, and more precisely to the opening of the pressure conversion channel arranged in the wall of the converter cylinder, initiates the conversion cycle of the pressure converter 7. In other words, the position of the moving part, in this embodiment the piston 8, of the converter cylinder switches on the control of the conversion cycle, in this case the initiation of the conversion cycle.

[0017] If during the movement of the converter cylinder 1 in direction +, the pressure caused by the load of the actuator 2 to channel A decreases below the set value of the first converter valve 3, the pressure medium will flow again through the first check valve 4 along channel A to the actuator 2, in the embodiment of Figure 3 to the piston side of the actuator 2, and the piston 8 of the converter cylinder 1 stops. The actuator 2 then returns to its normal operating state in terms of pressure and speed, which it had before the beginning of the conversion cycle.

[0018] Correspondingly, when the actuator 2 of the embodiment of Figure 3 operates in direction -, i.e. to the left in Figure 3, the directional control valve 6 can be arranged to a second position of the directional control valve 6 in such a manner that the pressure medium flows from channel P to channel B. The pressure medium exiting the actuator 2 then flows to the side of the smaller surface area of the converter cylinder 1 , i.e. to the piston rod 9 side of the converter cylinder, and moves the piston 8 and piston rod 9 in direction -, i.e. toward the larger surface area of the piston 8. The pressure medium exiting from the side of the larger surface area of the converter cylinder 1 , i.e. from the piston 8 side, is able to flow through the first converter valve 3 and second check valve 5 to channel A and on through the valve 6 to tank line T.

[0019] When the piston 8 has moved to the position, where it covers the converter cylinder 1 , more precisely the opening of at least one pressure conversion channel arranged in the wall of the converter cylinder barrel 1 1 , the pressure medium can no longer flow from the side of the larger surface area of the converter cylinder 1 , i.e. the piston 8 side, through said pressure conversion channel opening to the second check valve 5, but only through the first converter valve 3, more precisely the check valve of the first converter valve 3, to channel A and on to tank line T. When the piston 8 has further moved in direction - and reached a position, where it has passed the at least one opening of the pressure converter channel arranged in the wall of the cylinder barrel 1 1 of the converter cylinder 1 , the pressure medium can flow from the side of the smaller surface area of the converter cylinder 1 only through the second check valve 5 to channel A and on to tank line T. This ends the charging cycle of the pressure converter 7. In other words, the position of the moving part, in this embodiment the piston 8, of the converter cylinder switches on the charging control, in this case the ending of the conversion cycle.

[0020] In the embodiment of Figure 3, when the movement of the actuator 2 generates suction over the pressure converter 7, the ratio of the surface areas of the converter cylinder 1 causes a higher so-called suction force on the side of the larger chamber in the converter cylinder, which enables the charging of the pressure converter. Said charging caused by the suction effect can be prevented, if necessary, by using conventional pressure medium components in the actuator 2, with which the creeping of the actuator 2 can be prevented in spite of possible small leaks from the directional control valve 6 arranged in a closed position. Pressure medium components of this type may comprise locking or load discharge valves known per se, for instance. [0021] Figure 4 is a schematic view of a second pressure medium system comprising a pressure converter 7. In the embodiment according to Figure 4, when the actuator 2 works in direction +, i.e. toward the right in Figure 4, a directional control valve 6 can be arranged in the first position thereof in such a manner that the pressure medium is allowed to flow from channel P to channel A and through a second converter valve 10 to the actuator 2, i.e. in the embodiment of Figure 4, to the side of the larger surface area of the piston of the actuator 2, and to the side of the smaller surface area, i.e. the piston rod 9, of the converter cylinder 1 .

[0022] The second converter valve 10 may comprise a check valve that is controlled mechanically by a limit switch, for example, electrically by a position transducer, for example, or by some other manner known per se, a directional control valve, or some other valve that is adaptable to implement the function described herein. On the other hand, the second converter valve 10 may also comprise a mechanically opened check valve cartridge or some other corresponding valve component that is arrangeable internally to the structure of the converter cylinder 1 and adaptable to implement the function described herein. The piston 8, for instance, may then be adapted to change the state of the second converter valve 10 when returning to its initial position. The second converter valve 10 may then be positioned in the rear piece of the cylinder, for instance, in which case the piston pushes the valve open, when it returns to its innermost position. The state change of the second converter valve 10 is preferably mechanical, electrical, or a kick-down-type change, such as an on/off- type change, implemented in some other manner known per se.

[0023] As the load increases in the actuator 2, the pressure in channel A increases. The first converter valve 3 is adapted to stop the entry of the pressure medium to the side of the larger surface area of the converter cylinder 1 , i.e. to the piston 8 side of the converter cylinder 1 , when the pressure in channel A is lower than the set value of the first converter valve 3. Correspondingly, the first converter valve 3 is adapted to allow the pressure medium to flow to the side of the larger surface area of the converter cylinder 1 , i.e. to the piston 8 side, when the pressure in channel A increases under the influence of the load of the actuator 2 to be equal to the set value of the first converter valve 3 or higher. Because the same pressure then prevails on both work surfaces of the converter cylinder 1 , the pressure moves the piston 8 and piston rod 9 to direction +, i.e. to the direction of the smaller surface area, un- der the influence of the surface area difference between the work surfaces of the converter cylinder 1 .

[0024] In the embodiment of Figure 4, a switching part 12 is further connected to the piston 8 and/or piston rod 9 and adapted to change the state of the second converter valve 10. The switching part 12 may be a part forming a uniform structure with the piston 8 and/or piston rod 9, or a structural part connected to the piston 8 and/or piston rod 9 in some other manner and arranged to move together with them, or some other structural part that is able to cause the change of state in the second converter valve 10 on the basis of the position of the piston 8, piston rod 9, or some other moving part of the converter cylinder 1 , 1 ' in relation to the cylinder barrel 1 1 of the converter cylinder 1 , 1 '. Correspondingly, the switching part 12 may form part of the remaining structure of the pressure converter 7 in such a manner that the second converter valve 10 may be used under the influence of the position of the moving part of the converter cylinder 1 , such as the piston 8 and/or piston rod 9. The switching part 12 may then comprise a sensor, such as position transducer, that detects the piston 8, piston rod 9, or some other part moving in relation to the cylinder barrel 1 1 of the converter cylinder 1 , 1 '. After the piston 8 and/or piston rod 9 of the converter cylinder 1 has moved to the extent defined by the switching part and/or the position of the switching part, the switching part changes the state of the second converter valve 10, in the embodiment of Figure 4 to the check valve function, in which case the second converter valve 10 allows the pressure medium to flow only from channel A to the actuator 2 and to the side of the smaller surface area of the converter cylinder 1 . The pressure supplied to the actuator 2 then increases to the extent of the ratio of the surface areas of the converter cylinder 1 . This can be called the conversion cycle of the pressure converter 7. Thus, the position of the piston 8 and piston rod 9 in relation to the converter cylinder barrel then initiates, in this embodiment through the switching part, the conversion cycle of the pressure converter 7. In other words, the position of the inner part, i.e. in this embodiment the piston 8 or piston rod 9, of the converter cylinder switches, in this embodiment through the switching part, on the control of the conversion cycle, in this case the initiation of the pressure increase cycle.

[0025] If during the movement of the converter cylinder 1 in direction +, the pressure in channel A decreases below the set value of the first converter valve 3, the converter cylinder 1 will stop and the pressure medium will flow again through the second converter valve 10 to the actuator 2, in the embodiment of Figure 4 to the piston side of the actuator 2.

[0026] Correspondingly, when the actuator 2 of the embodiment of Figure 4 operates in direction -, i.e. to the left in Figure 4, the directional control valve 6 can be arranged in a second position of the directional control valve 6 in such a manner that the pressure medium flows from channel P to channel B. The pressure medium exiting the actuator 2 then flows to the side of the smaller surface area of the converter cylinder 1 , i.e. to the piston rod 9 side of the converter cylinder, and moves the piston 8 and piston rod 9 in direction -, i.e. toward the piston 8. The pressure medium exiting from the side of the larger surface area of the converter cylinder 1 , i.e. from the piston 8 side, is able to flow through the first converter valve 3 to channel A and on through the valve 6 to tank line T.

[0027] When the piston 8 and/or piston rod 9 or a separate switching part connected to them has moved to a position, in which it again changes the state of the second converter valve 10, in this embodiment the switching part 12 changes the state of the second converter valve by pressing the second converter valve 10 and allowing flow from the actuator 2 to channel A and on to tank line T. This ends the charging cycle of the pressure converter 7. In other words, the position of the moving part, in this embodiment the piston 8 or the piston rod 9, of the converter cylinder switches on the charging control, in this case the ending of the charging cycle.

[0028] It should be noted that in Figure 4, the piston 8 of the converter cylinder 1 is not shown in its initial position, but it has already moved slightly toward direction +. In the other Figures, 3, 5, and 6, the piston 8 is instead shown substantially in its initial position.

[0029] Figures 5 and 6 show some other pressure medium systems that comprise a pressure converter 7. The embodiment of Figure 5 may otherwise correspond to that of Figure 3 and the embodiment of Figure 6 may otherwise correspond to that of Figure 4, but the conversion ratio in the embodiments of Figures 5 and 6 has been increased in such a manner that the pressure converter 7 comprises a second converter cylinder 1 '. The second converter cylinder V may comprise a double-acting pressure medium cylinder known per se and/or a two-chamber pressure medium cylinder. As shown in Figures 5 and 6, the second converter cylinder 1 ' can then be connected in series with the first converter cylinder 1 in such a manner that the channel that is in the embodiments of Figures 3 and 4 connected to the piston rod side of the converter cylinder 1 is in the embodiments of Figures 5 and 6 connected to the piston rod side of the second converter cylinder V and the piston side of the second converter cylinder is connected to the piston rod side of the first converter cylinder 1 . In different embodiments, the pressure converter 7 may comprise one, two or more second converter cylinders 1 '. In different embodiments, the converter cylinders may be connected to each other in series or in parallel. By connecting converter cylinders in parallel, it is possible to increase the volume of the pressure converter, and by connecting converter cylinders in series, it is possible to alter the pressure conversion ratio of the pressure converter.

[0030] In an embodiment, the first converter valve 3 may comprise a sequence valve or some other pressure-opening valve known per se with adjustable opening pressure. In another embodiment, the first converter valve may comprise one or more separate check valves with a pressure release valve known per se connected in parallel thereto in a manner known per se. One or more check valves of the first converter valve 3 may be integrated to the valve that opens by the pressure of the first converter valve 3, or one or more check valves of the first converter valve 3 may be arranged in parallel to a separate, pressure-opening valve of the first converter valve 3. By furnishing the first converter valve 3 with more than one check valve, it is possible to easily form the first converter valve 3 that is dimensioned to optimally take into consideration the differences in the maximum volume flow through the first converter valve 3 toward the converter cylinder 1 and away from the converter cylinder 1 . In an embodiment, the check valve of the first converter valve 3 may comprise at least one valve component that is arrangeable internally to the structure of the converter cylinder 1 and adaptable to implement the function described herein. The at least one check valve of the first converter valve 3 and/or the pressure-opening valve of the first converter valve 3 may then be positioned in the rear piece of the cylinder, for example.

[0031] In some embodiments, more than one first converter valve 3 and/or second converter valve 10 may be connected in parallel. The capacity of the pressure converter can then be easily scaled and the pressure converter can easily be implemented even for high flows. [0032] Depending on the embodiment, some or all of the pressure converter 7 components may be arranged into an integrated entity or correspondingly formed by connecting separated components to each other.

[0033] As stated above, in the first position of the directional control valve 6, the pressure medium can, thus, flow from channel P to channel A, and from channel B to channel T, i.e. the tank connection. Thus, in the embodiments of Figures 3 to 6, it is then possible to operate in direction + with the actuator 2. In the second position of the directional control valve, the pressure medium is allowed to flow from channel P to channel B, and from channel A to channel T, which means that in the embodiments of Figures 3 to 6, it is possible to operate in direction - with the actuator 2. The directional control valve 6 may further comprise a third position, in which flow between all channels, for instance, is closed, and/or other additional positions. In different embodiments, it has also been possible to implement the operation of the directional control valve 6 in some other manner and/or component known per se, as long as the directional control valve 6 or corresponding pressure medium component is able to implement the described functionality.

[0034] In an embodiment, the converter cylinder 1 and/or second converter cylinder V may also comprise some other pressure medium cylinder than that described above, if the pressure medium cylinder is able to implement the described functionality.

[0035] In an embodiment, the pressure converter 7 can be positioned in channel B in addition to or instead of channel A. The pressure converter 7 arranged in channel B can then naturally convert the pressure when operating in direction - and charge the pressure converter 7 when operating in direction +.

[0036] In an embodiment, the at least one converter cylinder 1 of the pressure converter 7 arranged in channel A and/or B can be arranged in the direction opposite to the direction of the embodiments of Figures 3 to 6, in which case the side of the larger surface area of at least one converter cylinder 1 , 1 ' is connected to the actuator 2. In such a case, the pressure converter 1 does not increase the pressure supplied to the at least one actuator 2, but increases the volume flow supplied to the at least one actuator 2. This may be useful in applications, in which high force is not needed, but a high motion speed of the actuator 2 is beneficial. [0037] Even though, for the sake of simplicity, Figures 3 to 6 show embodiments, in which the actuator 2 is a pressure medium cylinder, in an embodiment the actuator 2 may be some other pressure medium-operated actuator, such as a pressure medium-operated motor, turning device or some other pressure medium-operated actuator known per se. It is apparent to a person skilled in the art that it is then not necessarily possible to refer to operation in direction + or -, but the operating principle of the pressure converter 7 corresponds to that described above.

[0038] In the present solution, only the position of the parts moving in relation to the converter cylinder barrel of the pressure converter determines the control of the conversion and charging cycle, i.e. the initiation or ending of the conversion and/or charging cycle. In such a case, in the present solutions, the switching of the charging operation is thus forced, i.e. arranged to depend on the physical position of the piston and/or piston rod in at least one converter cylinder, whereby it is possible ensure that the pressure converter 7 is always charged, i.e. the piston of the converter cylinder 1 , 1 ' has been returned to the position, in which the conversion cycle may begin as a new work movement of the actuator 2 starts in the work direction, in which the conversion cycle of the pressure converter 7 can be utilized. In this description, this position is referred to as the initial position. The converter cylinder may also be one of said other converter cylinders. Switching the charging operation on also requires very little energy/pressure, so there is no need to generate pressure separately for the charging. The pressure converter 7 can also in all embodiments be arranged in each case between one pressure medium line/channel, so it comprises exactly one input channel and one output channel. In the case of a double-acting actuator, it is possible to arrange in each case at least one pressure converter 7 into either one of the pressure medium lines/channels in one or both directions. Thus, the now described pressure converter is also suitable for single-acting actuators, such as actuators like the tip cart of a tractor that reverse through gravity, spring force or some other corresponding force. On the other hand, it is possible to work with double-acting actuators in direction - without this affecting the charging of the pressure converter.

[0039] When using the present pressure converter and/or method or some other described pressure conversion solution, the actuator 2 may be dimensioned to be smaller than without using the present solution. Thanks to the smaller actuator, such as pressure medium cylinder, it is then possible to pro- vide a higher working rate for an external actuator in work phases that do not require high force, than when using a larger actuator that is able to produce the same force with a corresponding work pressure without a pressure converter. The use of the external actuator can then also be optimized with the present solution so that high force is only produced when the load of the actuator is high, and normal work pressure can be used with a smaller load, and the rate of the actuator can be correspondingly optimized. This may be beneficial in connection with a wood chopping device or during branch-cutting or in connection with some other corresponding device with varying load, in which case a low-load phase, such as transfer phase, can be performed quickly, and during an actual work phase, such as wood splitting or branch cutting, it is possible to use a pressure converter to produce higher force. On the other hand, in embodiments in which a slow by forceful movement is advantageous, such as in presses or high-power cutters used by the fire department or in metal cutting, a corresponding force may be achieved with a smaller actuator but higher work pressure. In such a case, a low-pressure system provides the high pressure for the actuator requiring it and the entire pressure medium system need not be made into a high-pressure system. It is also possible to optimize with the pressure converter the need for high-pressure system components for actuators requiring high force, which is preferable, because high-pressure system components are typically more expensive and complex than components intended for lower pressures. In embodiments, where the converter cylinder is arranged in the opposite direction, it is correspondingly possible to increase the working rate of the actuator in comparison with a corresponding solution used with corresponding volume flow but no pressure converter.

[0040] It is obvious to a person skilled in the art that as technology advances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the above-mentioned examples but may vary within the scope of the claims.