Gas-powered drive system and operating method

Abstract

A gas-powered drive system has a drive which includes a first chamber and a second chamber which are separated from one another by a piston. One of the chambers is connected to a gas source to drive the work element and the other chamber is connected via an exhaust air throttle to a gas sink by means of a reversing valve to movement of the piston. A control valve is assigned to the driving chamber through which the driving chamber can be filled with gas from the gas source. The opening cross-section of the control valve is set as a function of a control pressure.

Claims

1. A gas-powered drive system,comprising a drive comprising a first chamber and a second chamber, which are separated from one another by a movable work element of the drive, the first chamber being configured to be connected to a gas source to form a chamber configured to drive the work element, and the second chamber being configured to be connected via an exhaust air throttle to a gas sink by means of a reversing valve, to form a chamber configured to counteract movement of the work element, wherein a control valve is provided to the driving chamber, the control valve being configured so that through the control valve the first chamber can be filled with gas from the gas source, the control valve also being configured so that an opening cross-section of the control valve can be set as a function of a control pressure prevailing upstream from the exhaust air throttle in a flow direction or as a function of a control pressure which is a pressure drop across the exhaust air throttle, the control valve also being configured so that the opening cross-section of the control valve can be increased when the pressure drop across the exhaust air throttle is to below a first limit pressure and can be decreased to close the control valve when the pressure drop across the exhaust air throttle further drops below a second limit pressure.

2. The system according to claim 1, wherein the first limit pressure is greater and the second limit pressure is lower than the pressure that prevails upstream from the exhaust air throttle or the pressure drop across the exhaust air throttle, whereby a supercritical gas flow in the exhaust air throttle can occur.

3. The system according to claim 1, further comprising an electronic or electric controller configured to measure the control pressure and to activate an electrical drive configured to adjust a valve actuator in the control valve as a function of a measured value of the control pressure.

4. The system according to claim 1, further comprising a gas line configured to be a control line which fluidically connects the control valve to the second chamber, the control line being configured so that the control pressure acts, through the control line, on the valve actuator of the control valve, the valve actuator being prestressed by an actuating force and thereby being configured to be displaced as the control pressure falls.

5. The system according to claim 4, wherein the control valve has a characteristic curve that describes a dependence on the opening cross-section of the control valve and the valve actuator displacement, the characteristic curve having a reversing slope at a valve actuator displacement between two extreme possible displacements of the valve actuator.

6. The system according to claim 5, wherein the control valve comprises two control edges configured to cooperate with the valve actuator or wherein a second valve actuator is provided and a respective one of the two control edges is disposed on each of the valve actuators the control edges being configured to increase the opening cross-section of the control valve upon a direction of displacement of the valve actuator which is defined by falling control pressure by cooperation with a first of the two control edges, and to decrease the opening cross-section in the same displacement direction by cooperation with a second of the two control edges until the opening cross-section of the control valve is entirely closed.

7. The system according to claim 4, further comprising respective reversing valves provided in a region of the control line between the control valve and the drive and between the exhaust air throttle and the drive, the reversing valves being configured so that, in a first switched stage, the first chamber can be connected to the control valve and, at the same time, the second chamber can be connected to the exhaust air throttle and, in a second switched stage, the second chamber can be connected to the control valve and, at the same time, the first chamber can be connected to the exhaust air throttle.

8. The system according to claim 1, further comprising a pressure reducer connected in parallel and a check valve that is situated in series, with the exhaust air throttle the pressure reducer and check valve being configured so that the second chamber can be filled with gas while the exhaust air throttle is blocked.

9. The system according to claim 1, wherein characterized in that a respective assembly comprising an exhaust air throttle and a control valve, including a control line connected to the other chamber, is assigned to each of the two chambers, the assemblies being configured so that it is possible for each of the two chambers to be filled with gas by the assigned control valve during a process phase during which the particular chamber acts as a driving chamber, and for each of the two chambers to be emptied by the assigned exhaust air throttle during a process phase during which the particular chamber acts as a counteracting chamber.

10. The system according to claim 9, further comprising a respective pressure reducer, connected in parallel with each of the assemblies, the pressure reducers being configured so that the system can be transferred from a state in which both chambers of each of the assemblies are pressure-relieved into an operating state by filling one of the two chambers with gas by way of the pressure reducer while pressurizing and opening the control valve assigned to the other chamber.

11. The system according to claim 1, wherein the movable work element comprises a piston.

12. A method for operating a gas-powered drive system, the gas-powered drive system comprising a drive comprising a first chamber and a second chamber, which are separated from one another by a movable work element of the drive, the first chamber being connected to a gas source to form a chamber configured to drive the work element and the second chamber being connected via an exhaust air throttle to a gas sink by means of a reversing valve to form a chamber configured to counteract movement of the work element, the method comprising assigning a control valve to the driving chamber through which the driving chamber is filled with gas from the gas source and setting an opening cross-section of the control valve as a function of a control pressure prevailing upstream from the exhaust air throttle in a flow direction or a control pressure which is a pressure drop across the exhaust air throttle so that the opening cross-section is increased by way of the control valve when the control pressure drops below a first limit pressure and the opening cross-section is decreased so that the control valve is closed when the control pressure further drops below a second limit pressure.

13. The method according to claim 12, wherein the movable work element of the gas-powered drive system comprises a piston.

Description

(1) The invention will be described in more detail hereafter based on the figures.

(2) FIG. 1 shows a first embodiment of the invention comprising a cylinder-piston assembly A as a work element, the piston 3 of which separates two chambers 1 and 2. It is assumed here that the work element A carries out a working stroke when the piston rod of the piston 3 is being extended.

(3) Using a reversing valve 7, a pressure source 4 can be selectively connected to a line L1 and, at the same time, a pressure sink 6 can be connected to a line L2, or vice versa. In this embodiment the pressure regulation according to the invention is carried out only during the working stroke, in particular so that the chamber 1 that is driving during the working stroke is only filled with gas via the control valve 8 to such an extent that a supercritical flow is present at the exhaust air throttle 5.

(4) For this purpose, it is provided that the control valve 8, by way of which the chamber 1 is filled, is situated in the line L1 leading to the chamber 1 that is driving during the working stroke. A check valve R1 is disposed in parallel with the control valve, which prevents inflow into the chamber bypassing the control valve 8, but allows gas to flow out of the chamber 1 during the return stroke, in particular when the control valve 5 is then closed (as is shown here).

(5) During the working stroke, gas is displaced from the chamber 2, which during the working stroke counteracts the movement of the piston 3, via the exhaust air throttle 5 and a check valve R2, which is disposed in series therewith and opens, in the direction of the pressure sink 6, to the pressure sink 6.

(6) As an essential aspect according to the invention, the invention provides that a gas line 9, serving as a control line 9, connects the control valve 8 to a line section that is situated in the line L2 between the counteracting chamber 2 and the exhaust air throttle 5.

(7) According to the invention, the control pressure acting in this line section, in particular essentially the pressure dropping across the exhaust air throttle 5, acts via the control line 9 on the valve actuator in the control valve 8 and can influence the position of the valve actuator, and thus the opening cross-section of the control valve 8, in such a way that, as the control pressure falls, the opening cross-section is increased when the control pressure drops below a first limit pressure, so that more gas flows into the driving chamber, and, when a further drop below a second limit pressure occurs, which is lower than the first limit pressure, the opening cross-section is decreased, and preferably closed entirely, in particular when a third limit pressure is reached, which is preferably lower than the second limit pressure.

(8) In this way, the control pressure is maintained in the regulating range around the first limit pressure until a drop below the second limit pressure occurs. This can preferably be selected such that a supercritical flow is achieved in the exhaust air throttle, and the first limit pressure is thus greater than the minimum pressure that is required for the supercritical flow. The second limit pressure is preferably lower than this minimum pressure.

(9) At the end of the stroke, the piston 3 is no longer able to displace gas from the chamber 2, so that the control valve 8 decreases the opening thereof, as a result of the control pressure dropping below the second limit pressure, until the valve closes, preferably when reaching or dropping below the third limit pressure.

(10) A return stroke can be initiated by switching over of the reversing valve 7. In this illustrated case, connecting the pressure source 4 to the line L2 prompts the check valve R2 to close, and the check valve R3 to open, which is situated in series with respect to a pressure regulating valve 12 by way of which the chamber 2 is filled for the return stroke. The gas that is displaced from the chamber 1 can escape without impairment to the pressure sink 6, for example to the outside, via the open check valve R1. At the same time, the pressure build-up in the chamber 2 ensures that force is applied to the valve actuator in the control valve 8 via the control line 9, so that the same opens again, in particular when the third limit pressure is reached or exceeded, and initiates a subsequent working stroke. The pressure conditions required for cyclical working strokes are thereby maintained. The system can be started from an idle position by pressurizing the chamber 2.

(11) FIG. 2 shows an embodiment in which a pressure-regulated movement of the piston 3 takes place both during the working stroke and during the return stroke, based on the control pressure in the control line 9.

(12) The control valve 8 is also provided in the line L1 here, which in this embodiment is permanently connected to the pressure source 4. The pressure sink 6 is permanently connected at the line L2 to the exhaust air throttle 5.

(13) The essential difference compared to FIG. 1 is that the chamber 1 is now selectively connected to the control valve, and the chamber 2 is selectively connected to the exhaust air throttle, or vice versa, via the reversing valve. The above-described pressure regulation by way of the control valve 8 thus always takes place with respect to the currently driving chamber of the two chambers 1, 2, and the exhaust air throttle is always present for the gas that flows out of the presently counteracting chamber.

(14) The pressure regulating valve 12 can be provided to achieve minimum filling of the formerly driving chamber, pressurization of the control line 9, and opening of the control valve 8 in an initial depressurized state of the two chambers, in the switched position shown here, with the control valve closed (at the end of the working stroke). The system is thus transferred to the regular operating state thereof again and can carry out a movement by switching over the reversing valve.

(15) FIG. 3 shows another possible embodiment in which a respective assembly AN1 or AN2, comprising a control valve 8 and an exhaust air throttle 5, is assigned to each of the two chambers 1 and 2. The control line 9 of a control valve 8, which is assigned to a particular chamber, has a fluid connection to the respective other chamber.

(16) The respective required flow direction is defined by the check valves R1, R2 in each of the assemblies AN1, AN2. In this way, R1 allows flow through the control valve 8 to the chamber and, at the same time, R2 blocks flow through the exhaust air throttle when the pressure source 4 is connected to the assembly AN1 or AN2, and R2 allows flow out of the chamber through the exhaust air throttle 5 and, at the same time, R1 blocks a flow through the control valve 8 when the pressure sink 6 is connected to the assembly AN1 or AN2.

(17) By way of the reversing valve 7, connection of the pressure source 4 and the pressure sink 6 to one assembly AN1 or AN2 can be alternatingly carried out.

(18) Using the same above-described effect, a pressure regulation van be carried out, during the working stroke and during the return stroke, or during reversing working strokes, which meets the desired pressure criterion during exhaust air throttling, and preferably supercritical flow.

(19) Here, the invention can provide that a pressure regulating valve 11 comprising a check valve is situated in parallel with the assembly AN2, by way of which initial commissioning of the system can be carried out when both chambers are depressurized, as has been described above.

(20) Furthermore, a pressure regulating valve can also be disposed in parallel with the assembly AN1, which is not shown.

(21) FIGS. 4a and 4b show a possible embodiment of a control valve 8 comprising a valve actuator 8a, which comprises two actuating bodies 8b and 8c that are connected by a reduced diameter region. Such a design of the valve actuator 8a can be provided in all possible embodiments of the valve 8. The valve actuator 8a is pressurized here on the left side by the control pressure from the control line 9, and is loaded here on the right by a force here a spring 13, which is disposed in a pressure-relieved space. As the control pressure in the line 9 falls, the valve actuator 8a is thus displaced to the left, based on this illustration. Action between the valve actuator 8a (the actuating body 8b thereof) and the control edge SK1 increases the opening cross-section, and action between the valve actuator 8a (the actuating body 8c thereof) and the control edge SK2 decreased the opening cross-section. The opening cross-section between the connections 4 (to the pressure source) and 1 (to the chamber/to the regulated volume) can thus be set as a function of the control pressure.

(22) The aforementioned limit pressures can be defined by means of the spring 13, the force of which can be settable. On the right side, the control valve 8 is gas pressure-relieved at the connection 23. In all possible embodiments of a control valve, the second and third limit pressures may be dependent on the first and may be determined by the spring as well as the design of the control valve, in terms of the geometry of the control edges.

(23) The illustration of FIG. 4a shows a position having a maximum opening cross-section, which may be found at a control pressure between the first and second limit pressures, or preferably at the second limit pressure. Preferably, as the control pressure rises and the first limit pressure is exceeded, the control valve can close, or initially decrease and then close the opening cross-section as the control pressure rises, in particular if no residual opening is provided, for example by a mechanical stop, or no parallel flow path is provided, and, according to the invention, can increase the opening cross-section up to the illustrated maximum open position when a drop below the first limit pressure occurs, as the control pressure falls. If the control pressure falls further, the opening cross-section is decreased until it closes at the control edge SK2.

(24) FIG. 4b shows an embodiment of the same control valve from FIG. 4a in a position in which the first limit pressure can be present in the control line 9. In this case, the control valve is closed at the control edge SK1 and, proceeding from this position, would increase the opening cross-section from the closed position as the control pressure falls. Proceeding from this position, the control valve 8 would remain closed as the control pressure rises.

(25) FIG. 5 shows an embodiment in which, in contrast to FIGS. 4a and 4b, two springs 13a, 13b are disposed coaxially inside one another. The spring 13b acts on the valve actuator 8a, and the spring 13a acts indirectly via the bearing element 14 which can be displaced into the stop 15. In this way, a first displacement range of the valve actuator 8a is defined, in which both springs cooperate, and a second displacement range, when the bearing element 14 is situated in the stop, in which only the spring 13b acts. The limit pressures and the slopes of the opening characteristics of the two control edges as a function of the control pressure can thus be decoupled from one another. The space in which the springs 13a and 13b are disposed is pressure-relieved via the connection 23.

(26) FIG. 6 shows an embodiment in which the embodiment in FIGS. 4a and 4b was expanded by an integrated minimum pressure application for starting from a depressurized state. In this way, the pressure reducers 11 and 12 shown in the previous FIGS. 2 and 3 and provided for this purpose can be dispensed with.

(27) The piston 20 shown on the right is used to reduce the outlet pressure of the control valve 8 for the minimum pressure application. A spring 21 acts on the piston 20, which, through the borehole 22, is subjected to the pressure regulated by the control valve, thus, in particular, the pressure in the driving chamber 1. The connections 1 and 22 are thus preferably directly connected. The spring 21 is preloaded so that the piston 20 moves to the left only when the outlet pressure of the control valve 8 is sufficient, which is to say when the pressure in the driving chamber 1 has a minimum pressure predetermined by the spring 21. The space in which the springs 13b and 21 are disposed is pressure-relieved via the connection 23.

(28) The position of the piston defines the preloading of the springs 13b and 13c. These define the position of the valve actuator 8a both as a function of the control pressure in the line 9 and as a function of the preload thereof, and consequently define the position of the piston 20.

(29) When the piston 20 is situated in the left extreme position, the spring rates and preloads of the springs 13b and 13c correspond to the nominally required value for the known function of the valve, in particular as was described above. As a result of partial relaxation of the two springs 13b and 13c, displacement of the piston 20 to the right results in displacement of the valve actuator 8a to the right.

(30) With the system in an entirely depressurized state, pressure is present neither in the control line 9 nor downstream from the control valve, which is to say in the borehole 22. The piston 20 is in the right extreme position thereof, loaded by the springs 21 and 13b. Due to the displacement of the valve actuator 8a to the right, the control valve is consequently opened via the control edge SK2 and the actuating body 8c. When pressure is applied to the feed line of the control valve, the valve position described above applies increasing pressure to the regulated volume, which acts via the borehole 22 back on the piston 20. When this pressure reaches the target value, the piston 20 is moved to the left, the valve actuator 8a is displaced to the left as a result of the increase in the tension of the springs 13b and 13c, and the control valve is closed via the control edge SK2 and the actuating body 8c.

(31) From this point in time onward, the piston 20 remains in the left extreme position thereof during normal operation of the system, and the function of the valve corresponds to the variant in FIGS. 4a and 4b. To improve the operating behavior, a spring system 21 made with disk springs can, in particular, be used for loading the piston 20.

(32) FIG. 7 shows a modification of the embodiments of FIG. 5 and FIG. 6. Unless the functions described there and in FIG. 4 are replaced by functions described hereafter, these also apply to the embodiment of FIG. 7.

(33) In a modification of FIG. 6, the piston 20, in this embodiment, no longer acts via a resilient spring 13b, but acts rigidly here, via the piston rod 20a, on the valve actuator. The cooperation of the piston 20 and the spring 21 is reversed in terms of the direction here. Again, the space in which the spring 21 is disposed is pressure-relieved via the connection 23. Here, the piston 20 is accordingly subjected to the pressure of the connection 1, from the direction of the valve interior, for example via the line 22, which connects the space to the left of the piston 20 to the connection 1, preferably inside the valve.

(34) As in FIG. 5, the limit pressures and the slopes of the opening characteristics of the two control edges can be decoupled from one another as a function of the control pressure. However, here, this does not take place by the springs 13b and 21 disposed inside one another, but as differs therefrom by the implementation of opening cross-sections that differ as a function of the position, in the action between a control edge, here the control edge SK1, and the valve actuator 8a, in particular in the case of an actuating body, here the actuating body 8b of the valve actuator 8a. According to the invention, this manner of influencing the characteristics via opening cross-sections that differ as a function of the position can be carried out independently of the further specific illustrated designs of the valve 8.

(35) So as to implement these position-dependent opening cross-sections, an actuating body, for example here the actuating body 8b, can, for example, include axially extending control grooves 8d in the surface thereof, which extend only regionally in the axial direction, which is to say, not completely across the surface. In this example, the control grooves 8d end before of the right axial end of the actuating body 8b.

(36) As differs from FIGS. 5 and 6, application of control pressure here preferably takes place via the connection 9, onto the axial end face of the right actuating body 8b on which the piston rod 20a also acts. The action occurs against the spring 13c on the other side of the valve actuator 8a, which is disposed in a space that is pressure-relieved via the connection 23. The movement of the valve actuator 8a is reversed in the embodiment of FIG. 7, compared to FIGS. 5 and 6.