Pneumatic device with a movably mounted piston

Abstract

A pneumatic device having a pneumatic cylinder and a piston movably mounted in the pneumatic cylinder to divide an interior of the pneumatic cylinder into two chambers. The chambers are connected to a line network having a valve assembly. The line network, in a plurality of operating states of the valve assembly serving for venting the respective chamber, connects the respective chamber to at least a respective selected one of a plurality of outflow openings, of the pneumatic device, and in a further operating state of the valve assembly, disconnects the respective chamber from the outflow opening. A control installation of the pneumatic device adjusts the operating state of the valve assembly. The line network is designed so that, in at least three of the operating states for venting the respective chamber, the connection between the respective chamber and the outflow opening is established by mutually dissimilar flow resistances.

Claims

1. A pneumatic device having a pneumatic cylinder and a piston which is movably mounted in the pneumatic cylinder and by way of which an interior of the pneumatic cylinder is subdivided into two chambers, wherein the chambers are connected to a line network of the pneumatic device that comprises a valve assembly, wherein the line network, in a plurality of operating states of the valve assembly serving for venting a respective chamber, is specified to connect the respective chamber to an outflow opening, or at least a respective selected one of a plurality of outflow openings, of the pneumatic device, and in at least one further operating state of the valve assembly, to disconnect said respective chamber from the outflow opening or all outflow openings, wherein a control installation of the pneumatic device is specified to adjust the operating state of the valve assembly, wherein the line network is designed in such a manner that, in at least three of the operating states serving for venting the respective chamber, the connection between the respective chamber and the outflow opening, or the respective selected outflow opening, is established by way of mutually dissimilar flow resistances, wherein said pneumatic device comprises at least one sensor which is specified to detect sensor data pertaining to a position of the piston relative to the pneumatic cylinder, and/or a spatial orientation of the piston and/or of the pneumatic cylinder, and/or pertaining to a pressure in at least one of the chambers, wherein the control installation is specified to adjust the operating state of the valve assembly as a function of the sensor data, and wherein the control installation, when meeting a recuperation condition dependent on the sensor data, is specified to actuate the valve assembly in such a manner that the chamber of which the volume is currently being reduced by the movement of the piston is connected to a pressure source so as to direct compressed air back into the pressure source.

2. The pneumatic device according to claim 1, wherein at least one of the chambers, at least in the operating states serving for venting the respective chamber, is connected to an exhaust line, wherein the line network comprises at least two line branches which extend in each case from the exhaust line of the line network to one, or a respective, outflow line, wherein the, or the respective, outflow line is connected to the outflow opening or in each case at least one of the outflow openings, wherein a shut-off valve of the valve assembly is in each case disposed in the line branches so as to release or block the respective line branch as a function of the operating state of the valve assembly, wherein, in the at least three operating states serving for venting the respective chamber, mutually dissimilar line branches and/or mutually dissimilar combinations of line branches are released, and/or wherein a directional control valve of the valve assembly is specified to selectively connect the exhaust line or the outflow line to the different line branches, wherein, in the at least three operating states serving for venting the respective chamber, mutually dissimilar line branches and/or mutually dissimilar combinations of line branches are connected to the exhaust line and the, or the respective, outflow line.

3. The pneumatic device according to claim 2, wherein at least two of the line branches have mutually dissimilar flow resistances.

4. The pneumatic device according to claim 2, wherein an aperture and/or a throttle are/is in each case disposed in at least one of the line branches or in all line branches.

5. The pneumatic device according to claim 4, wherein the throttle and/or aperture disposed in a first one of the line branches has a flow cross section which differs from the flow cross section of the apertures and/or throttles disposed in a second one of the line branches, and/or in that at least one of the apertures and/or throttles has an adjustable flow cross section.

6. The pneumatic device according to claim 4, wherein the pneumatic device comprises a pneumatic module which forms at least the pneumatic cylinder, the piston and a part of the line network that comprises the exhaust line and the valve assembly, wherein the pneumatic module has a respective exhaust port for a plurality or all of the line branches, by way of which a respective portion of the respective line branch, configured separately from the pneumatic module, is connected to the pneumatic module, wherein the portion configured separately from the pneumatic module comprises the throttle and/or aperture of the respective line branch.

7. The pneumatic device according to claim 2, wherein, in all operating states serving for venting a first one of the chambers, the first one of the chambers is connected to the exhaust line, wherein, in all operating states serving for venting a second one of the chambers, one of the line branches on a side of the shut-off valve disposed in the one of the line branches, which side is directed away from the exhaust line, or on a side of the directional control valve that selectively connects the exhaust line to the different line branches, which side is directed away from the exhaust line, is connected to the second chamber.

8. The pneumatic device according to claim 1, wherein a first sub-assembly of the valve assembly, in a first group of the operating states of the valve assembly, is specified to connect an exhaust line of the line network to a first one of the chambers, and in a second group of the operating states of the valve assembly, to connect the or an exhaust line of the line network to a second one of the chambers, wherein a second sub-assembly of the valve assembly, in at least some of the operating states serving for venting one of the chambers, connects the exhaust line to the outflow opening or at least a respective one of the outflow openings.

9. The pneumatic device according to claim 1, wherein an exhaust line of the line network that is connected to the respective chamber at least in the operating states serving for venting the respective chamber, irrespective of the operating state of the valve assembly, is permanently connected to the outflow opening or at least one of the outflow openings by way of at least one bypass line.

10. The pneumatic device according to claim 1, wherein the chambers are in each case connected to the line network by way of exactly one chamber port, wherein the valve assembly, in at least one operating state serving for pressurizing the respective chamber, is specified in such a manner that a first sub-assembly of the valve assembly disconnects the respective chamber port from the outflow opening or all outflow openings and connects the respective chamber port to a compressed air connection and/or a compressed air source of the pneumatic device.

11. The pneumatic device according to claim 10, wherein the first sub-assembly of the valve assembly, in a second group of the operating states of the valve assembly, is specified to connect a pressurization line of the pneumatic device that is connected to the compressed air connection and/or the compressed air source to a first one of the chambers, and in a first group of the operating states of the valve assembly, to connect said pressurization line to a second one of the chambers.

12. The pneumatic device according to claim 1, wherein the valve assembly is specified in such a manner that in a non-energized valve installation a selected one of the chambers is connected to a pressure source and/or a compressed air connection of the pneumatic device, and the other one of the chambers is connected to the outflow opening or at least one of the outflow openings.

13. The pneumatic device according to claim 1, wherein the respective chamber in a plurality or all of the operating states serving for venting the respective chamber is connected to the outflow opening, or to at least one of the outflow openings, by way of a proportional valve, wherein the opening degree of the proportional valve is dissimilar in these operating states.

14. The pneumatic device according to claim 12, wherein the connection between the other one of the chambers and the outflow opening is established in an operating state for venting the other one of the chambers that has a highest flow resistance for the venting.

15. A pneumatic device having a pneumatic cylinder and a piston which is movably mounted in the pneumatic cylinder and by way of which an interior of the pneumatic cylinder is subdivided into two chambers, wherein the chambers are connected to a line network of the pneumatic device that comprises a valve assembly, wherein the line network, in a plurality of operating states of the valve assembly serving for venting a respective chamber, is specified to connect the respective chamber to an outflow opening, or at least a respective selected one of a plurality of outflow openings, of the pneumatic device, and in at least one further operating state of the valve assembly, to disconnect said respective chamber from the outflow opening or all outflow openings, wherein a control installation of the pneumatic device is specified to adjust the operating state of the valve assembly, wherein the line network is designed in such a manner that, in at least three of the operating states serving for venting the respective chamber, the connection between the respective chamber and the outflow opening, or the respective selected outflow opening, is established by way of mutually dissimilar flow resistances, wherein an exhaust line of the line network that is connected to the respective chamber at least in the operating states serving for venting the respective chamber, irrespective of the operating state of the valve assembly, is permanently connected to the outflow opening or at least one of the outflow openings by way of at least one bypass line.

16. A pneumatic device having a pneumatic cylinder and a piston which is movably mounted in the pneumatic cylinder and by way of which an interior of the pneumatic cylinder is subdivided into two chambers, wherein the chambers are connected to a line network of the pneumatic device that comprises a valve assembly, wherein the line network, in a plurality of operating states of the valve assembly serving for venting a respective chamber, is specified to connect the respective chamber to an outflow opening, or at least a respective selected one of a plurality of outflow openings, of the pneumatic device, and in at least one further operating state of the valve assembly, to disconnect said respective chamber from the outflow opening or all outflow openings, wherein a control installation of the pneumatic device is specified to adjust the operating state of the valve assembly, wherein the line network is designed in such a manner that, in at least three of the operating states serving for venting the respective chamber, the connection between the respective chamber and the outflow opening, or the respective selected outflow opening, is established by way of mutually dissimilar flow resistances, wherein the valve assembly is specified in such a manner that in a non-energized valve installation a selected one of the chambers is connected to a pressure source and/or a compressed air connection of the pneumatic device, and the other one of the chambers is connected to the outflow opening or at least one of the outflow openings, wherein the connection between the other one of the chambers and the outflow opening is established in an operating state for venting the other one of the chambers that has a highest flow resistance for the venting.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIGS. 1 and 2 show exemplary embodiments of a pneumatic device according to the invention;

(2) FIG. 3 shows a pneumatic module which can be used instead of the pneumatic module utilized in FIG. 1; and

(3) FIGS. 4 and 5 show further exemplary embodiments of a pneumatic device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows a pneumatic device 1 having a pneumatic cylinder 5 and a piston 6 which is movably mounted in the pneumatic cylinder 5 and by way of which an interior of the pneumatic cylinder 5 is subdivided into two chambers 7, 8. In the example, the chambers 7, 8 are connected to a line network 10 by way of a single chamber port 37, 38, said line network 10 enabling, on the one hand, pressurization of the chambers 7, 8 by way of a compressed air connection 31, or a pressure source 39 of the pneumatic device 1, respectively, and venting of the respective chamber 7, 8 by way of the outflow openings 11 to 13, on the other hand.

(5) The line network 10 comprises a valve assembly 9. The latter in a respective operating mode of the valve assembly 9 that serves for pressurizing the respective chambers 7, 8 serves for connecting the respective chamber 7, 8 to the pressure source 39 and to disconnect said respective chamber 7, 8 from the outflow openings 11 to 13, on the one hand. On the other hand, the valve assembly 9, in a plurality of operating states of the valve assembly 9 which are in each case utilized for venting the respective chamber 7, 8, serves for connecting the respective chamber to in each case at least one of the outflow openings 11 to 13. In order for the operating states to be changed, the control installation 14 controls the respective actuator 51 of the shut-off valves 20, 21, or directional control valves 47, 48 of the valve assembly 9, respectively.

(6) The line network 10 herein is designed in such a manner that in different operating states, in the example in different switching states of the shut-off valves 20, 21, dissimilar flow resistances for the outflow of air to one or a plurality of the outflow openings 11 to 13 are derived for a respective chamber to be vented, the latter in the example being connected to the exhaust line 15 by way of the respective directional control valve 47, 48. As a result, the quantity of air, or gas, respectively, exiting the respective chamber 7, 8 per unit of time differs in the different operating states at a given pressure in the respective chamber 7, 8 to be vented, and in the region of the outflow openings 11 to 13.

(7) It is made possible as a result that dissimilarly intense accelerations are derived for the piston, for example when the chamber not to be vented is pressurized, depending on which operating state and thus which flow resistance is selected by the control unit 14. Accordingly, during venting, for example, deceleration of the piston at different intensities can also take place after the end of the pressurization of the other chamber by selecting a suitable flow resistance, so as to avoid a hard impact and thus a jolting stop of the piston 6, for example.

(8) In the exemplary embodiment shown, the different flow resistances are implemented in that the exhaust line 15 is connected to the outflow openings 11, 12 by way of two line branches 16, 17, which have a respective shut-off valve 20, 21, and is additionally permanently connected to the outflow opening 13 by way of a bypass line 23.

(9) In the switching position of the shut-off valves 20, 21 shown, which is also assumed in a non-energized state of the pneumatic device 1, or of the valve assembly 9, respectively, the chamber 8 is exclusively connected to the exhaust line 15. Since the shut-off valves 20, 21 are switched for blocking, the air, or the gas, respectively, can flow out of the chamber 8 exclusively by way of the bypass line 23 and the outflow opening 13. The bypass line 23 herein has a high flow resistance, which can be implemented by utilizing a suitable aperture 26 with a small flow cross section, for example. As a result, the gas contained in the chamber 8 can flow out only relatively slowly.

(10) Since pressurization of the chamber 7 in the non-energized state takes place by way of the directional control valve 48 in the example shown, the piston 6 in the example in the non-energized state is displaced up to a detent on the left in the image, thus up to the minimum extent of the chamber 8, wherein not unduly high speeds are achieved herein by virtue of the high flow resistance of the bypass line 23, which is typically advantageous during uncontrolled displacement in the non-energized state. In the energized state of the pneumatic device 1, the non-energized state also corresponds to a utilizable operating state for venting the chamber 8. Venting in the chamber 7 with a substantially identical flow resistance is also possible by switching both directional control valves 47, 48.

(11) During the operation of the pneumatic device 1, it is often desirable to achieve higher accelerations of the piston 6 than can be achieved by venting the respective chamber 7, 8 to be vented exclusively by way of the bypass line 23. Higher accelerations can be achieved in that the flow resistance for the gas flowing out of the respective chamber 7, 8 to be vented is reduced, which in the example shown can be made possible in that the control installation 14 actuates the respective actuator 51 of the shut-off valve 20 and/or of the shut-off valve 21 so as to release the line branch 16 and/or the line branch 17.

(12) In the simplest case, the line branches 16, 17 can have approximately identical flow resistances when each of the shut-off valves 20, 21 is opened, for example when identical apertures 24, 25 or throttles are utilized for limiting the flow in both line branches 16, 17. If this is the case, three operating states with dissimilar flow resistances can be provided for venting the respective chamber 7, 8. The minimum flow resistance is achieved when both line branches 16, 17 are released by opening both shut-off valves 20, 21. A medium flow resistance is achieved when only one of the line branches 16, 17 is released in that only one of the shut-off valves 20, 21 is released by actuating the respective actuator 51. The maximum flow resistance is achieved by closing both shut-off valves 20, 21.

(13) The movement of the piston 6 in the example is controlled by the control installation 14 which defines a switching state of the directional control valves 47, 48, or of the shut-off valves 20, 21, depending on the operating state. The different operating states herein lead to accelerations of the piston 6 in dissimilar directions, or at dissimilar intensities, or may also lead to a position of the piston 6 being held, respectively.

(14) The movement of the piston 6 can be controlled according to a fixed pattern, or trigger signals for a change of position, or specific target positions, can be provided by an external installation, for example. In order to implement a desired behavior in the movement herein it is expedient to detect the relative position of the piston 6 in relation to the pneumatic cylinder 5 by a sensor 41. This takes place in the example in that the piston 6 has a magnetic coding 45 which is detectable by a magnetic field sensor 41, for example a Hall sensor.

(15) Additionally or alternatively to the position of the piston 6, the control installation can also take into account a speed and/or acceleration of the piston 6 which is determined from the sensor data. In a simple example, in a movement of the piston 6 toward a detent, an acceleration of the piston 6 can be reduced, or the latter intensely decelerated, for example when reaching a specific position ahead of the detent, in particular as a function of the current speed of the piston 6, in that the flow resistance for gas flowing out of the chamber 7 or 8 to be reduced, respectively, is increased by closing one or both shut-off valves 20, 21.

(16) However, it is also possible to carry out more complex control procedures in which a target motion pattern is defined for a specific position of the piston 6, for example, and the actual movement of the piston 6 detected by the sensor 41 is controlled in a closed loop in such a manner by adapting the operating states that a deviation from the target movement is minimized.

(17) In principle, it is possible to identify forces acting on the piston 6 by means of an acceleration of the piston 6 detected by the sensor 41, and to take into account said forces when controlling the pneumatic device 1. In order to more rapidly identify corresponding forces and to minimize delays in terms of closed-loop control as a result, for example, it can however be advantageous to detect the pressure in the respective chamber 7, 8 by sensors 42, 43, and/or the spatial orientation of the pneumatic cylinder 5 and thus also of the piston 6 by the sensor 44, so as to determine the influence of gravity on the movement of the piston 6 and to take into account said influence of gravity when controlling. As a result, overshooting of a position control, for example, and other inaccuracies can be minimized, as a result of which piston movements which are particularly free of jolts and vibrations can be achieved.

(18) In order to be able to control the movement of the piston 6 as precisely as possible, it can be advantageous if more than three mutually dissimilar flow resistances can be provided for venting the respective chamber 7, 8. In the design embodiment shown in FIG. 1, this can be implemented in a particularly simple manner in that the line branches 16, 17 are designed in such a manner that the latter have mutually dissimilar flow resistances when the respective shut-off valve 20, 21 is opened. This can be achieved, for example, in that throttles or apertures 24, 25 which have mutually dissimilar flow cross sections are utilized in the line branches 16, 17. Additionally or alternatively, it is also possible to provide an aperture 24, 25 or throttle in at least one of the line branches 16, 17, the flow cross section of said aperture 24, 25 or throttle being adjustable.

(19) While different operating states of the valve assembly 9 are adjustable according to requirements by the control installation 14 in the pneumatic device 1, in which different operating states dissimilar flow resistances for venting a respective chamber 7, 8 are derived, it can be expedient to utilize dissimilar maximum or minimum flow resistances in dissimilar applications, or to also adapt the flow resistances for intermediate stages. In the exemplary embodiment shown in FIG. 1 this is possible in a particularly simple manner in that the portions 32, 33 of the line branches 16, 17, or the portion 34 of the bypass line 23, respectively, in which the respective aperture 24-26 that dominates the flow resistance is disposed, are designed as separate modules that are attached to a respective exhaust port 28, 29 of a pneumatic module 27 comprising the pneumatic cylinder 5 with the piston 6 and that part of the line network 10 that comprises the valve assembly 9. As a result, the apertures 24 to 26, or the portions 32-34 which comprise them of the line branches 16, 17, respectively, are easily replaceable, or different apertures 24-26 and/or throttles and/or modules which comprise corresponding line portions 32-34, respectively, can be utilized for adapting the pneumatic module 27 to dissimilar requirements.

(20) The valve assembly 9 in the exemplary embodiment shown comprises two sub-assemblies 35, 36. The first sub-assembly 35, in the state shown in FIG. 1, herein serves for connecting the chamber 8 to the exhaust line 15 and thus at least to the outflow opening 13, anddepending on the switching state of the second sub-assembly 36optionally additionally to the outflow openings 11 and 12 of the outflow lines 18, 19, while the chamber 7 is connected to the pressure source 39. In contrast, by switching both directional control valves 47, 48 of the first sub-assembly 35, the chamber 8 can be connected to the pressure source 39, and the chamber 7 to the exhaust line 15 and thus to the outflow openings 11 to 13, as explained. Optionally, an operating state can be utilized in which, proceeding from the switching position shown in FIG. 1, both chambers 7, 8 are connected to the exhaust line 15 by switching exclusively the directional control valve 48, this enabling a rapid pressure equalization between the chambers 7, 8, as a result of which the piston 6 is almost freely movable.

(21) The discussion up to this point assumes that gas from the chambers 7, 8 is discharged exclusively by way of the exhaust line 15. However, it is also possible that, when the control installation meets a recuperation condition depending on the sensor data of the sensors 41-44, that one of the chambers 7, 8 of which the volume is being reduced by the momentary movement of the piston is connected to the pressure source 39 by actuating the directional control valves 47, 48 of the first sub-assembly 35. This is particularly expedient when the pressure in the chamber being reduced, which pressure can be directly detected by the sensor 41 or 43, for example, is above the pressure of the pressure source, because gas can in this case be fed back into the pressure source, as a result of which the efficiency of the pneumatic device 1 can be further increased.

(22) FIG. 2 shows a pneumatic device 2 which is constructed largely like the pneumatic device 1 shown in FIG. 2, but is modified in terms of some aspects which are explained in more detail hereunder.

(23) A first difference lies in that the first sub-assembly 35 for selectively connecting the respective chamber 7, 8 to the pressurization line 40 or the exhaust line 15 is formed by a common directional control valve 49, instead of the two directional control valves 47 utilized in FIG. 1. A 4/3-way valve with a blocked central position is utilized in the example herein. Alternatively, it would be possible, for example, to provide an additional valve position so as to connect the chambers 7, 8 directly by way of the directional control valve 49, and/or to provide further ports, for example separate ports for the line branches 16, 17 and/or the bypass line 23, on the valve.

(24) As a further difference in comparison to the exemplary embodiment shown in FIG. 1, the line branches 16, 17 and the bypass line 23 in the pneumatic device 2 are converged in a common outflow line 18 after the respective aperture 24, 25, 26, this requiring only one outflow opening 11 for the entire pneumatic device 2. This can be particularly advantageous when the outflow opening 11 is provided with a silencer 50, as in the exemplary embodiment shown, because the necessary installation space of the pneumatic device 2 can be reduced in this case by utilizing a common silencer for both line branches 16, 17 and the bypass line 23.

(25) The utilization of a common outflow line 18 in the exemplary embodiment shown in FIG. 2 is possible in a particularly simple manner, because the apertures 24 to 26 therein are not designed as separate components outside a pneumatic module 27, or as part of separate modules, respectively, as was the case in FIG. 1. If such a modular construction is to be utilized, a common outflow line 18 could nevertheless be utilized, for example in that the portions 32-34 of the line branches 16, 17, or of the bypass line 23, respectively, after leading through the respective aperture 24-26, in a modification of the exemplary embodiment shown in FIG. 1, would be led back into the pneumatic module 27 and in the latter converge in a common outflow line.

(26) FIG. 3 shows a pneumatic module 52 which, instead of the pneumatic module 27, would be able to be utilized in the exemplary embodiment utilized in FIG. 1. The pneumatic module 52 differs from the pneumatic module 27 utilized in FIG. 1 essentially in that a 3/3-way valve is utilized as the second sub-assembly 36 of the valve assembly 9, by way of which both line branches 16, 17 can be selectively disconnected from the exhaust line 15, or one of the line branches 16, 17 is in each case selectively connected to the exhaust line 15. In this way, by suitably actuating the directional control valve 22 by the control installation 14, exclusively the bypass line 23, or the bypass line 23 conjointly with either the first line branch 16 or the second line branch 17, can be utilized for venting the respective chamber 7, 8.

(27) If the line branches 16, 17, or apertures 24, 25 or throttles disposed therein, respectively, have mutually dissimilar flow resistances, three different flow resistances for discharging gas from the respective chamber 7, 8 connected to the exhaust line 15 can thus be adjusted by the three switching positions of the directional control valve 22.

(28) The design embodiment shown in FIG. 3 could for example be modified in that, in one of the switching states of the directional control valve 22, both line branches 16, 17 are connected to the exhaust line 15, for example. This switching state can replace one of the switching states in which only one of the line branches 16, 17 is connected to the exhaust line 15, or this may be an additional switching state in order to increase the number of potentially providable flow resistances.

(29) The pneumatic device 3 illustrated in FIG. 4 corresponds largely to the pneumatic device 2 illustrated in FIG. 2, wherein, deviating therefrom, the design embodiment already explained in the context of FIG. 1 has been chosen for the first sub-assembly 35. However, instead of utilizing two line branches 16, 17 having a respective shut-off valve 20, 21, only a single line branch is utilized in FIG. 4, the flow resistance of the latter being adjustable by a proportional valve 46. The control installation 14 herein is specified to adjust at least three different positions of the proportional valve 46, so as to adjust at least three dissimilar flow resistances for gas to be discharged from a respective chamber 7, 8.

(30) The pneumatic device 4 shown in FIG. 5 differs from the pneumatic device 2 shown in FIG. 2 in that the first sub-assembly 35 of the valve assembly 9 is implemented by two directional control valves 47, 48 instead of a single directional control valve 49, as has already been explained in the context of FIG. 1, on the one hand. Moreover, the chamber 8 is connected to the outflow opening 11 in another way, as will be explained in more detail hereunder.

(31) As has already been explained in the context of FIG. 1 or FIG. 2, respectively, the chamber 7, in all operating states of the valve assembly 9 serving for venting the chamber 7, is connected to the exhaust line 15, wherein the exhaust line by way of the bypass line 23 is permanently connected to the outflow opening 11, on the one hand, and on the other hand is connected to the latter so as to be able to be switched by way of the line branches 16, 17.

(32) However, in those states that serve for venting the chamber 8, thus in the switching state of the directional control valve 47 shown in FIG. 5, the chamber 8 is connected to the directional control valve 21 on the side of the latter facing away from the exhaust line 15. Thus, if the directional control valve 21 is in the closed state, as is illustrated in FIG. 5, venting of the chamber 8 takes place exclusively by way of the aperture 24, or the rear portion of the line branch 17, respectively.

(33) However, by adjusting the directional control valve 21, the chamber 8 is additionally connected to the exhaust line 15 and thus, at least by way of the bypass line 23, and when additionally activating the shut-off valve 20, by way of the line branch 16, connected to the outflow opening 11.

(34) In this way, three different flow resistances for venting the respective chamber 7, 8 can also be provided in the design embodiment shown in FIG. 5, at identical flow resistances of the line branches 15, 17, or of the apertures 24, 25, respectively, or even four different flow resistances can be provided at dissimilar flow resistances of the line branches 16, 17, or of the apertures 24, 25, respectively.

(35) While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.