Pneumatic drive, air-release valve therefor, and method for air release
Patent Information
- Application Number
- EP2023818410
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-24
- Filing Date
- 2023-12-05
- Publication Date
- 2025-12-31
Smart Images
Figure EP2023084324_29082024_PF_FP_ABST
Abstract
Description
[0001] Pneumatic actuator, vent valve therefor and method for venting
[0002] The invention relates to a pneumatic drive comprising a displacement unit with at least one volume-variable drive chamber, wherein the at least one drive chamber is connected via a line to at least one switching valve that can be switched between at least two switching positions, and wherein the line comprises a throttle unit assigned to the drive chamber, which is connected via a first line section of the line to the switching valve and via a second line section of the line to the drive chamber.
[0003] Such a pneumatic drive is known, for example, from the publication DE 102011 013 187 B4.
[0004] In such a drive, it is preferably provided that the movable active surface of such a drive chamber exerts a force in the direction of movement on a device or mass to be moved.
[0005] The effective surface is preferably subjected to a restoring force at least temporarily.
[0006] The displacement unit in the invention can be, for example, a bellows, a vane drive, or a cylinder-piston unit, and preferably a double-acting cylinder-piston unit with two drive chambers separated by a piston with two opposing piston surfaces. Here, the piston surfaces form the active surfaces. Each active surface is reset by the other.
[0007] Furthermore, the invention relates to a method for relieving the pressure in a drive chamber of a pneumatic drive, in particular a pneumatic drive as mentioned above and / or further specified in the description of the invention, wherein the pressure in the drive chamber is relieved by a throttle valve of a throttle unit.
[0008] In a preferably double-acting cylinder-piston unit as a displacement unit, the piston preferably has a connection to a piston rod in order to exert an effect outwards, i.e. outside the cylinder-piston unit.
[0009] Each effective surface of a displacement unit, in particular each of the opposing piston surfaces of a double-acting cylinder-piston unit, can be formed from a single surface, but also from several partial surfaces, whereby in the latter case the effective surface is to be understood as the effectively acting effective surface, in particular which is the sum of all equally oriented partial surfaces or which corresponds to the sum of the projections of all partial surfaces of a drive chamber in the plane orthogonal to the direction of movement.
[0010] Preferably, in this embodiment of a pneumatic drive, the drive chamber, preferably each of a plurality of drive chambers, can be pressurized by means of the changeover valve through the line, depending on the switching position of the changeover valve, e.g. from a gas pressure source and / or relieved of pressure, e.g. in the direction of a pressure sink, in particular the atmospheric environment, wherein the respective throttle unit can be flowed through in both opposite directions by the gas used for operation, e.g. air.A throttle unit preferably has a throttle valve and a check valve which are connected in parallel, preferably so that when the throttle unit is pressurized from the first line section leading to the changeover valve, the gas flow flowing through the throttle unit is largely or entirely guided through the open check valve past the throttle valve, in particular only a smaller partial gas flow is guided through the throttle valve, and when the throttle unit is pressurized from the second line section leading to the drive chamber, the gas flow flowing through the throttle unit is guided completely through the throttle valve.
[0011] The operation of such a pneumatic actuator with a throttle unit is generally known as exhaust-throttled drive, e.g. from the publication Doll et al.: Dimensioning of pneumatic cylinders for motion tasks, International Journal of Fluid Power, 2015.
[0012] This is achieved by pressurizing the drive chamber used for propulsion with gas, thereby initiating a movement, e.g., moving the piston of a (possibly double-acting) cylinder-piston unit. For resetting, the then passive drive chamber—especially if there are multiple drive chambers, a previously used and currently passive drive chamber—must be relieved of pressure to allow for resetting. Such resetting can be achieved, for example, by filling another of several drive chambers, e.g., two drive chambers.
[0013] In throttled pneumatic actuators, especially those designed as double-acting cylinder-piston units, the currently driving drive chamber is preferably always pressurized to full pressure. Therefore, after the switching valve controlling the pneumatic actuator switches, the compressed gas or compressed air from the drive chamber, which now counteracts the restoring movement and is passive during this period, must escape through the throttle unit, particularly so that a partial restoring force is only generated by this pressure reduction.
[0014] The time required for the air to slowly escape through the throttle unit is no longer available for the actual movement task. The pneumatic drive is therefore not operating optimally. As a result, the compressed gas consumption of such throttled pneumatic drives is excessive due to their oversizing, which has a very negative impact on operating costs and the ecological footprint.
[0015] The flow cross-section of throttle units cannot simply be increased because this would result in the permissible speed being exceeded in the direction of the end stop of the effective area, especially of a piston, which would lead to damage to the drive in the long term.
[0016] The object of the invention is to further develop a pneumatic drive of the type mentioned above and a method for depressurizing pneumatic drives in such a way that the time required to depressurize the passive drive chamber is reduced. A further object is preferably to achieve this purely mechanically, in particular without electronic control, in particular using operating parameters that are already available.
[0017] Furthermore, it is preferably provided that the use and effect of a throttle unit is not omitted in the invention, but rather the venting is only supported over a predetermined period of time, in particular in order to be able to continue to use the gas cushion provided by the effect of a throttle unit in the passive drive chamber to regulate the speed at the end of the movement of the active surface, in particular of a piston. The passive drive chamber is the one that is or will be relieved of pressure at the time in question, whereas the pressurised drive chamber is referred to as active. In displacement units with two counteracting drive chambers, e.g. in double-acting cylinder-piston units, one drive chamber can always be active and another passive at the same time.
[0018] The invention also relates to a vent valve comprising a valve body with a valve actuator designed as a movable, e.g. displaceable valve body, with which a first valve connection can be switched to a second valve connection in a first switching state of the valve actuator and can be shut off in a second switching state.
[0019] The object is achieved with a pneumatic drive of the type mentioned at the outset, in which the line of the at least one drive chamber, preferably the lines of each drive chamber, has a branch in the second line section leading to a switchable vent valve, wherein the vent valve comprises a valve actuator movable between at least two switching states and the branch is open in a first switching state in the direction of a pressure sink, in particular through a valve connection of the vent valve, and is closed in a second switching state, wherein the valve actuator can be acted upon by a first force in a first direction, in particular is acted upon during operation, with which the valve actuator can be moved in the direction to assume the first switching state and this first force is dependent on the pressure in the first line section,wherein the valve actuator can be acted upon by a second force in a second direction, in particular during operation, with which the valve actuator can be moved in the direction for assuming the second switching state, and this second force is formed by the sum of a first partial force, in particular which is at least substantially constant or dependent on the position of the valve actuator, and a second partial force which is dependent on the pressure in the first line section.
[0020] Preferably, the second direction is opposite to the first direction.
[0021] In particular, the currently passive drive chamber can be relieved of pressure not only by the throttle unit but also by the vent valve, in particular at the same time as being relieved by the throttle valve of the throttle unit, and in particular can be relieved more quickly by the vent valve than by the throttle valve of the throttle unit.
[0022] Further preferably, said first force is dependent on the pressure in the first line section and on time, in particular this force is, starting from a maximum force which is dependent on the maximum pressure in the first line section, preferably linearly dependent, decreasing with a time delay after a pressure decrease in the first line section and / or with a smaller gradient than the gradient of the pressure in the first line section, in particular also increasing with a time delay after a pressure increase in the first line section and / or increasing with a smaller gradient than the gradient of the pressure in the first line section.
[0023] Due to the partial forces described above, the second force as a whole is dependent on the pressure in the first line section with an offset given by the first partial force, in particular wherein the second force directly follows a change in the pressure in the first line section or at least follows it with a time delay that is smaller than the time delay for the first force. In particular, after a pressure decrease in the first line section, the gradient of the first force has a smaller magnitude than the gradient of the second force. The invention can preferably provide that, for a given static pressure in the first line section, the first force and the second partial force of the second force are of the same magnitude and opposite in direction.Due to the first partial force acting simultaneously and in the same direction as the second partial force, the second force as the sum of these two partial forces is greater than the first force in the case of a static pressure in the first line section.
[0024] In general, it can be provided that in the case of a static pressure, the second force is greater than the first force, in particular regardless of how the respective forces are composed of several partial forces.
[0025] The invention can also provide that the said first force and / or the said second force are each composed of at least two partial forces, wherein at least one of the at least two partial forces is dependent on the pressure in the first line section, in particular also dependent on time. The at least one further partial force is preferably at least substantially constant or dependent on the position of the valve actuator.
[0026] Such a further partial force, in particular a partial force independent of pressure, accordingly forms an offset for the otherwise overall pressure-dependent first and / or second force, in particular wherein the offset also acts when no force-generating pressure is present. The respective, in particular pressure-independent partial force (of the first and / or second force) can be generated, for example, by a force-generating element provided in the vent valve, e.g. a spring element. Preferably, the partial force independent of pressure, in particular the aforementioned offset for the second force, is greater than for the first force, provided that such an offset exists for the first force.Preferably, in the invention, the valve actuator is formed by a valve body which is movably mounted in the vent valve and which has a first pressurizable active surface which adjoins a first valve chamber connected to the first line section, in particular by means of which the first force can be generated, and which has at least one second pressurizable active surface which adjoins at least one second valve chamber connected to the first line section, in particular by means of which the second partial force of the second force can be generated, wherein the second active surface is acted upon by means of a force generating element, e.g. spring element, in particular a compression spring, with the first partial force.
[0027] Such a valve body can be designed, for example, as a linearly displaceable valve piston whose effective surfaces are formed by piston surfaces.
[0028] In general, the pressurizable active surfaces in the invention, regardless of the element on which they are realized, are those surfaces which, when pressurized, generate a resulting pressure force which has a component acting in the direction of movement.
[0029] Preferably, the force-generating element, e.g., a spring element, is adjustable so that the partial force generated thereby can be varied. The force-generating element / spring element can preferably be a mechanical spring element, e.g., a helical spring, disc spring, etc., but can also be designed as a pneumatic or magnetic spring element.
[0030] Preferably, a vent valve according to the invention is used in which the valve actuator has a first pressurizable active surface which adjoins a first valve chamber connected to the second or a third valve connection and has at least one second pressurizable active surface which adjoins at least one second valve chamber connected to the second or third valve connection, wherein the second active surface is subjected to a force by means of a force generating element, in particular a spring element, in particular a compression spring, wherein the first valve chamber, in particular in the body of the vent valve, is connected to the second or third valve connection with a greater flow resistance than the second valve chamber.
[0031] Here, the movable valve body can preferably be a linearly movable valve piston, the effective surfaces of which are determined by the piston surfaces.
[0032] Here, the first valve connection is preferably connected to the branch of the pneumatic actuator. The second valve connection is preferably connected to a pressure sink, e.g., the atmospheric environment or the first line section. The third valve connection is preferably connected to the first line connection. The first and second valve connections can be connected or separated from one another depending on the position of the valve actuator. If the second and third valve connections are connected to the first line section, the second and third valve connections can also be identical, i.e., formed by the same connection element of the vent valve body.
[0033] The valve body or the valve actuator is preferably linearly movable in the respective valve chamber, but can also be movable with other forms of movement, e.g. pivoting, rotational, etc.
[0034] Accordingly, the first force is generated or at least can be generated by the pressure acting on the first active surface in the first valve chamber, which is filled or emptied via this line section depending on the gas pressure in the first line section, in particular through the third valve connection. Accordingly, the second partial force of the second force is generated or at least can be generated by the pressure acting on the at least one second active surface in the second valve chamber, which is filled or emptied via this line section depending on the gas pressure in the first line section, in particular through the third valve connection.
[0035] Here too, each of the effective surfaces, in particular the opposing effective surfaces of the valve actuator, can be formed from a single surface, but also from several partial surfaces, wherein in the latter case the effective surface is to be understood as the respectively effectively acting effective surface from the sum of all equally oriented partial surfaces or as the sum of the projections of all partial surfaces of a valve chamber in the plane orthogonal to the direction of movement.
[0036] Preferably, the first effective area and the second effective area are exactly the same size, in particular in order to ensure that the first force and the second partial force of the second force cancel each other out when there is static pressure in the first line section and thus the same pressure in the first and second valve chambers.
[0037] In particular in the case of static pressure conditions in the first line section (same pressure in both valve chambers), preferably also when the pressure in the first valve chamber or when the differential pressure between the two valve chambers has fallen to a pressure less than a predetermined minimum pressure, in particular which is dependent on the first partial force or results from this in conjunction with the effective area of the valve actuator, in particular furthermore when the pressure in the second valve chamber corresponds to the pressure in the first line section, the invention thus has the effect that the valve actuator is moved by the second force, in particular which is then essentially only given by the first partial force, into the closed position in which the branch is closed, in particular so that the (further) pressure relief of the (passive) drive chamber then only takes place via the throttle unit.This ensures that after the pressure in the first valve chamber or the said differential pressure drops below the said minimum pressure, the effect of the vent valve is eliminated, only the throttle unit acts and can be used in such a way that the piston of a cylinder-piston unit, in particular the piston of a cylinder-piston unit, is braked by the gas cushion in the direction of the end position of the effective surface of the displacement unit.
[0038] It is preferably provided that the first valve chamber is connected to the first line section and / or the third valve connection by means of a greater flow resistance, in particular generated by a throttle or a throttle valve, compared to the second valve chamber.
[0039] This results in pressure changes in the first line section being transmitted more quickly to the second valve chamber, and the pressure change in the first valve chamber thus lags behind the pressure change in the second valve chamber.
[0040] Alternatively, this can be expressed in such a way that after a pressure change in the first line section, the pressure equalization with the first valve chamber takes longer than with the second valve chamber, and / or immediately after the pressure change in the first line section, the amount of the temporal pressure gradient in the first valve chamber is smaller than in the second valve chamber.
[0041] The change in the first force is thus also delayed in time and / or slower compared to the change in pressure in the first line section and thus also delayed in time and / or slower compared to the change in the second force. In the event of pressure relief in the first line section, in particular substantially down to atmospheric pressure, at least substantially only its first partial force remains as the second force, because the second partial force is effectively eliminated immediately following the pressure drop because the second valve chamber is depressurized comparatively quickly, whereas the first force is greater than the second force over a predetermined period of time because the pressurized gas escapes from the first valve chamber more slowly in comparison due to the higher flow resistance.
[0042] The aforementioned time period ends when the first force becomes smaller than the first partial force of the second force. From this point on, the second force is greater than the first force and blocks the branch.
[0043] The invention can thus achieve that a drive chamber of the displacement unit, in particular of a cylinder-piston unit, is relieved more quickly by the vent valve over the predetermined period of time than would be the case if the gas flowed solely through the throttle unit.
[0044] Since it is intended that the second force becomes greater than the first force before the drive chamber is completely relieved to the atmospheric pressure level, the residual emptying of the drive chamber from the time the branch is closed always only takes place through the throttle unit.
[0045] This can be ensured by a suitable design of the volume of the first valve chamber and / or by selecting a suitable flow resistance between the first valve chamber and the third valve connection or the first line section, and / or by the preferably adjustable partial force of the second force, which is provided by a force-generating element. This allows the effective surface in the displacement unit, e.g., a piston in a cylinder-piston unit, to be moved more smoothly toward the end position.
[0046] The object is further achieved by a method of the type mentioned at the outset, which implements the effects described above, in which the pressure relief also takes place through an additional vent valve, in particular through the vent valve described according to the invention, and the drive chamber is pressure-relieved over a predetermined period of time through the vent valve with a larger gas volume flow than through the throttle unit, wherein the time period results from a pressure drop of different speeds in two valve chambers of the vent valve, via which pressure-dependent opposing forces act on a movable valve actuator and which are switched to a common pressure sink with different flow resistances. The movable valve actuator can - as already mentioned - be a movable valve body, e.g. a linearly movable valve piston.
[0047] In the aforementioned application using the vent valve, this common pressure sink can be formed by the first line section, in particular the one connected to the third valve port. In this case, the valve chambers are the aforementioned first and second valve chambers.
[0048] In the method, this means in particular that during the specified time period, the gas volume flow through the vent valve is greater than the gas volume flow through the throttle unit. The effect of the vent valve, which is limited to the time period, thus ceases at the end of the time period, but in particular with a time interval before the end of each cycle of pressure relief of the passive drive chamber. Preferably, a pressure relief cycle is thus ended with the sole effect of the exhaust air throttle unit. When carrying out the method or when using the pneumatic drive according to the invention, it is preferably provided that during the predetermined time period one of the two forces, in particular the aforementioned first force, which loads the valve actuator towards an open position, exceeds the other force, in particular the aforementioned second force.
[0049] The open position is the position in which the drive chamber is depressurized through the vent valve, in particular the aforementioned branch is open, preferably via the second valve connection directly to the atmospheric environment or to another pressure sink, e.g. the first line section, if this is switched to the atmospheric environment via the changeover valve.
[0050] The time period begins when one of the two opposing forces, in particular the first force which loads the valve actuator towards an open switching state, becomes greater than the other, in particular when a pressure drop occurs in the first line section, and ends when this force becomes smaller than the other again, in particular when the pressure in the first valve chamber or when the differential pressure between the two valve chambers becomes smaller than a minimum pressure, e.g. as previously described.
[0051] In this case, both forces preferably change as a function of the pressure in the common pressure sink, e.g. from the onset of a pressure drop in the first line section, but with different temporal behavior. In the event of a pressure drop, the decrease in the (first) force which loads the valve actuator towards an open switching state temporarily lags behind the decrease in the opposite (second) force, i.e. the (first) force decreases more slowly, in particular over the duration of the said time period, in particular wherein at the end of the time period an equilibrium of forces is reached between the two forces, after which the force, in particular the aforementioned second force, which loads the valve actuator towards the closed switching state becomes or is greater.
[0052] This is because the first force continues to decrease beyond the point of force equilibrium, whereas the second force does not fall below the magnitude of the first partial force. This also means that the aforementioned minimum pressure in the first valve chamber, or the aforementioned differential pressure, is a pressure at which a first force is generated that corresponds to the first partial force (the second force).
[0053] In all embodiments, it is preferably provided in a further development that the first valve chamber and the second valve chamber are connected by means of a flow resistance, in particular a throttle.
[0054] Preferably, the first valve chamber and the second valve chamber are connected to one another through the valve actuator via a connecting channel, in particular wherein the connecting channel forms an increased flow resistance in the connection between the first valve chamber and the first line section and / or third valve connection compared to the connection between the second valve chamber and the first line section and / or third valve connection, preferably wherein the connecting channel locally has a cross-sectionally tapered zone.
[0055] Preferably, the flow resistance is adjustable.
[0056] Furthermore, it is preferably provided that the predetermined time period is changed by adjusting the volume of the valve chamber through which the force is exerted that loads the valve actuator toward the open position, and / or by changing the flow resistance with which the valve chamber is connected to the common pressure sink through which the force is exerted that loads the valve actuator toward the open position. In the aforementioned application on the pneumatic drive, in particular when using the aforementioned vent valve, this is preferably the first valve chamber.
[0057] For this purpose, this (first) valve chamber, in particular of the venting valve and pneumatic drive according to the invention, preferably has an adjustable volume, in particular in that this valve chamber comprises two housing parts which delimit the valve chamber volume and which are displaceable relative to one another, in particular linearly, preferably one housing part can be inserted into the other.
[0058] In this case, the first housing part preferably has a connection at an axial end region to a sleeve which coaxially surrounds the outside of the second housing part, in particular wherein a threaded connection is formed between the inner wall of the sleeve and the outer wall of the second housing part.
[0059] The invention can generally provide that the branch is directly connected to the atmospheric environment in the first switching state (in particular via its second valve connection) or is at least connectable, or that the branch is directly connected to a pressure vessel or is at least connectable, in particular wherein the pressure in the pressure vessel is always lower than the supply pressure of the pressure source of the pneumatic drive, preferably wherein recuperated air in the pressure vessel is reused for further purposes as compressed air at a lower pressure level, or that the branch is indirectly connected to the atmospheric environment via the first line section through the changeover valve (in particular via its second valve connection) or is at least connectable, in particular wherein a preferably conventional quick exhaust valve is arranged in the first line section.The invention is explained in more detail with reference to the figures. The description is based on the common features of Figures 1 to 4, with individual deviations being described. Figure 5 shows a structural example of a vent valve that can be used in Figures 1, 2, and 4. The wiring in Figure 3 can be implemented in a similar manner, but requires a separation of the previously described connections 2 and 3, which is not implemented in Figure 5.
[0060] The invention is described using the example of a double-acting cylinder-piston unit as a displacement unit, but can of course also be used with other types of displacement units that have at least one pressurizable drive chamber via which pressure can be exerted on an active surface.
[0061] Figures 1 to 3 show a pneumatic actuator 1 with a double-acting cylinder-piston unit 2, which has two drive chambers 2a, 2b separated by a piston 2c with two opposing piston surfaces, which here form two opposing effective surfaces of the displacement unit. The piston acts outward via the piston rod 2d.
[0062] The two drive chambers 2a, 2b are each connected via a separate line to a switching valve 3 that can be switched between at least two switching positions for both drive chambers 2a, 2b. Alternatively, it can also be provided that each line of a respective drive chamber 2a, 2b has its own switching valve.
[0063] Each line associated with a respective drive chamber 2a, 2b comprises a throttle unit 4 associated with the respective drive chamber 2a, 2b, which is connected to the switching valve 3 via a first line section 5a of the line and to the drive chamber 2a, 2b via a second line section 5b of the line. The respective line thus comprises the two line sections 5a, 5b and the throttle unit 4.
[0064] Due to the switchability, one of the two drive chambers, e.g. chamber 2a, can be alternately connected to a pressure source 9, while at the same time the other drive chamber, e.g. chamber 2b, is connected to a pressure sink 8.
[0065] If the line section 5a is switched from the switching valve 3 to the pressure source 9, as shown in Figures 1 to 3, gas flows through the line section 5a, through the open check valve and the throttle valve of the throttle unit 4 and through the line section 5b into the drive chamber 2a, while at the same time gas flows from the drive chamber 2b through the line section 5b, through the throttle valve of the other throttle unit 4, whose check valve is closed, and through the first line section 5a to the pressure sink 8.
[0066] In Figures 1 to 3, the reference numerals are indicated only on the elements of one of the lines, here to the drive chamber 2a. The structure is identical in the other line to the drive chamber 2b.
[0067] Figure 4 shows a single-acting cylinder actuator whose pneumatically active side has the same features described above. However, the retracting movement is achieved by an external load FA. This can be, for example, a weight force, spring force, or constant pressure force. It can act either on the rod 2d or internally on the piston, for example, in the case of an integrated spring or a constant pressure application to the rod side.
[0068] If the line section 5a is switched from the switching valve 3 to the pressure source 9, as shown in Figure 4, gas flows through the line section 5a, through the open check valve and the throttle valve of the throttle unit 4 and through the line section 5b into the drive chamber 2a.
[0069] To reduce the extension speed, additional fittings not shown may optionally be present in line 5a or 5b according to the prior art. These are generally throttle check valves whose check valves are closed when air flows into chamber 2a; they therefore act as so-called supply air throttles. Such fittings will not be considered further, as they have no influence on the aspect of the invention.
[0070] The structure and functionality of the systems in Figures 1 to 4 are known in the prior art.
[0071] The inventive aspect is achieved by the vent valves 6 in the boxes outlined in dashed lines. The structure is identical for both lines in each of Figures 1 to 3, but differs in Figures 1, 2, and 3. The different valve designs shown in Figures 1 to 3 can all also be implemented on single-acting actuators. The circuitry shown in Figure 4 corresponds to the design in Figure 3.
[0072] This ensures that the respective line in Figures 1 to 3 from both drive chambers 2a, 2b or in Figure 4 only from one drive chamber 2a in the second line section 5b has a branch 7 leading to the switchable vent valve 6, wherein the vent valve 6, which is shown in a structural example in Figure 5, has a valve actuator 6a that is movable between at least two switching states, wherein the branch 7 can be opened directly or indirectly in the direction of a pressure sink 8 in a first switching state and is closed in a second switching state. The closed state is shown in Figures 1 to 4.
[0073] The valve actuator 6a can be or is acted upon by a first force F1 in a first direction, here to the right, with which the valve actuator 6a can be moved in the direction for assuming the first switching state. This first force F1 is dependent on the pressure in the first line section 5a, because the force F1 is exerted on the piston surface of the valve actuator 6a via the pressure prevailing in a first valve chamber 6b, which is connected to the first line section 5a, preferably by means of the throttle cross-section 6e, as indicated by the dashed lines within the vent valve 6. The variable-volume valve chamber 6b is shown in a structural example of the vent valve in Figure 5. Alternatively or cumulatively, an adjustability of the throttle cross-section and / or the pressure-independent partial force of the second force, in particular the spring preload, can also be provided.
[0074] The valve actuator 6a can further be subjected to a second force F2 in a second direction, here to the left, with which the valve actuator 6a can be moved in the direction for assuming the second switching state. This second force F2 is formed by the sum of a first partial force, in particular which is at least substantially constant, and a second partial force which is dependent on the pressure in the first line section 5a. The first partial force is generated here by a compression spring element 6c which acts directly on the valve actuator 6a. The second partial force of the second force F2 is exerted on the piston surface of the valve actuator 6a via the pressure prevailing in a second valve chamber 6d which is connected to the first line section 5a, which is indicated within the vent valve 6 by the dashed lines in Figures 1 to 4.The second valve chamber 6d is also shown in the constructive example of the vent valve in Figure 5.
[0075] Since the first valve chamber 6b and the second valve chamber 6d are both connected to the first line section, here via a flow resistance or a throttle 6e, the same pressure prevails in both valve chambers 6b, 6d under static conditions.
[0076] Since the effective areas / piston areas of the valve actuator 6a in the two valve chambers 6b, 6d are the same size, although they could be different, in this example the first force F1 and the second partial force of the second force F2 are equal and cancel each other out due to their opposite directions. Accordingly, in this case the second force F2 is greater than the first force F1 by the amount of the first partial force generated by the spring element 6c.
[0077] Such a static or at least quasi-static case occurs, for example, when the first line section 5a from the switching valve 3 is connected to the pressure source or to the pressure sink and pressure equalization has occurred in all volume elements of the overall arrangement. In these cases, the vent valve is always pushed into the closed position by the force F2.
[0078] Starting from the situation shown in Figures 1 to 4, in which the drive chamber 2a is pressurized, the effect of the arrangement and the operating method according to the invention can be described as follows:
[0079] In this situation, the pressure in the first and second valve chambers 6b, 6d is equal, and the vent valve 6 is closed. If the switching valve 3 is now switched so that the first line section 5a is connected to the pressure sink 8, the pressure in the first power section 5a drops. The drive chamber 2a begins to vent through the throttle unit 4.
[0080] Since both valve chambers 6b and 6d are connected to the first line section 5a, but the valve chamber 6b is connected to the first line section 5a via the resistance line element 6e, e.g. a throttle valve or a zone with a reduced cross-section, with a higher flow resistance than the valve chamber 6d and here the valve chamber 6b also has a storage volume, the pressure in the valve chamber 6b drops more slowly than in the valve chamber 6d, where the pressure drops almost immediately.
[0081] The pressure is thus reduced immediately following the switching of the switching valve 3 in the second valve chamber 6d in such a way that in fact only the constant partial force of the second force F2 acts through the spring element, at least if a residual force due to the pressure at the pressure sink 8 is neglected.
[0082] In the first valve chamber 6b, however, the pressure remains at a higher level for a longer period due to the slower and longer flow out of the first valve chamber 6b, so that immediately after the pressure drop generated in the first line section 5a, the pressure in the first valve chamber 6b is greater than in the second and as a result the force F1 becomes greater than the constant partial force of the force F2, whereby the vent valve is opened.
[0083] The drive chamber 2a is then depressurized more quickly via the vent valve than by the exhaust air throttle unit 4, which acts parallel to the vent valve. If, after a period of time that depends on the flow resistance and the volume in the first valve chamber 6b, the pressure in the first valve chamber 6b or the differential pressure between the two valve chambers falls below a minimum pressure at which the force F1 is equal to the first partial force of the second force F2, a force equilibrium is reached at this minimum pressure, after which the second force F2 becomes greater than the first force F1. Once the pressure falls below the minimum, the valve actuator 6a is then moved into the position in which the branch 7 is closed.
[0084] The drive chamber 2a can then no longer vent through the vent valve 6 and the remaining venting takes place through the exhaust air throttle unit 4 at a reduced speed, so that the piston 2c moves slowly to the end stop.
[0085] The invention thus ensures that accelerated venting of the drive chamber occurs only over a predetermined period of time, after which residual venting still follows through the throttle unit 4. The period of time can be adjusted by appropriately selecting the volume of the first valve chamber 6b and / or the flow resistance of the resistance element 6e and / or the first partial force of the force F2.
[0086] For this purpose, the invention preferably provides that the volume of the first valve chamber 6b is adjustable, e.g. with the construction according to Figure 5.
[0087] Here, the valve chamber 6b is formed between two housing parts 6f and 6g, whereby the inner housing part 6f can be pushed coaxially into the outer housing part 6g. The inner housing part 6f is connected at the axial end to a sleeve 6h surrounding the outer housing part 6g, which can serve as a handle for adjustment and, for example, has a threaded connection to the outer housing part. The differences between Figures 1 to 3 arise from the fact that in Figure 1, the pressure sink 8, to which the branch 7 is connected by the vent valve 6, is connected to the second valve connection of the vent valve 6 via the first line section 5a when the changeover valve 3 has connected the pressure sink 8 to the first power section 5a.
[0088] In Figure 2, the first line section 5a additionally has a quick-vent valve 10. This has its own pressure sink 8, which is connected to the valve according to the invention as soon as the switching valve vents the associated first line section 5a.
[0089] In Figure 3, however, the vent valve 6 connects branch 7 at the first valve connection directly to the atmosphere. The second connection of the vent valve 6 can therefore be open to the atmosphere.
[0090] Figure 5 additionally shows that the first valve chamber 6b can be connected to the second valve chamber 6d via a channel in the valve actuator, which, for example, provides an increased flow resistance for the venting of the first valve chamber 6b by means of a cross-sectionally tapered zone or a resistance element.
Claims
Patent claims 1. Pneumatic drive (1) comprising a. a displacement unit with at least one volume-variable drive chamber (2a, 2b), b. wherein the at least one drive chamber (2a, 2b) is connected via a line to at least one changeover valve (3) that can be switched between at least two switching positions, c. wherein the line comprises a throttle unit (4) assigned to the drive chamber (2a, 2b), which is connected to the changeover valve (3) via a first line section (5a) of the line and is connected to the drive chamber (2a, 2b) via a second line section (5b), characterized in that d. the line of the at least one drive chamber (2a, 2b), preferably the lines of each drive chamber (2a, 2b), has a branch (7) leading to a switchable vent valve (6) in the second line section (5b), e.wherein the vent valve (6) comprises a valve actuator (6a) movable between at least two switching states and the branch (7) is open or at least openable in the direction of a pressure sink (8) in a first switching state and is closed in a second switching state, f. wherein the valve actuator (6a) can be acted upon, in particular is acted upon, by a first force (F1) in a first direction, with which the valve actuator (6a) in the direction for assuming the first. switching state and this first force (F1) is dependent on the pressure in the first line section (5a), g. wherein the valve actuator (6a) can be acted upon, in particular is acted upon, by a second force (F2) in a second direction, with which the valve actuator (6a) is movable in the direction for assuming the second switching state and this second force (F2) is formed by the sum of a first partial force, in particular which is at least substantially constant or dependent on the position of the valve actuator, and a second partial force which is dependent on the pressure in the first line section (5a).
2. Pneumatic drive according to claim 1, characterized in that the valve actuator (6a) is formed by a valve body which is movably mounted in the vent valve (6), which has a first pressurizable active surface which adjoins a first valve chamber (6b) connected to the first line section (5a) and which has at least one second pressurizable active surface which adjoins at least one second valve chamber (6d) connected to the first line section (5a), wherein the second active surface is acted upon by means of a force generating element (6c), in particular a spring element (6c), in particular a compression spring, with the first partial force.
3. Pneumatic drive according to claim 2, characterized in that the first valve chamber (6b) is connected to the first line section (5a) by means of a greater flow resistance than the second valve chamber (6d), in particular generated by a resistance element (6e), preferably a throttle.
4. Pneumatic drive according to claim 3, characterized in that the first valve chamber (6b) and the second valve chamber (6d) are connected by means of a flow resistance (6e), in particular a throttle, preferably the first valve chamber (6b) and the second valve chamber (6d) are connected to one another through the valve actuator (6a) via a connecting channel, in particular wherein an increased flow resistance in the connection is formed between the first valve chamber (b) and the first line section (5a) in comparison to the connection between the second valve chamber (6d) and the first line section (5a), preferably wherein the connecting channel locally has a cross-sectionally tapered zone.
5. Pneumatic drive according to one of the preceding claims 2 to 4, characterized in that the first valve chamber (6b) has an adjustable volume, in particular in that the valve chamber (6b) comprises two housing parts (6f, 6g) which delimit the valve chamber volume and which are displaceable relative to one another, in particular linearly, preferably one housing part (6f) can be inserted into the other (6g).
6. Pneumatic drive according to one of the preceding claims, characterized in that the branch (7) in the first switching state is a. directly connected to the atmospheric environment or at least connectable by means of the vent valve (6), or b. directly connected to a pressure vessel or at least connectable by means of the vent valve, in particular wherein the pressure in the pressure vessel is always lower than the supply pressure of the pressure source of the pneumatic drive, preferably wherein recuperated air in the pressure vessel is reused for further purposes as compressed air at a lower pressure level, or c. indirectly connected to the atmospheric environment via the first line section (5a) through the changeover valve (4) or at least connectable by means of the changeover valve, in particular wherein a quick vent valve (10) which opens when the flow direction is reversed is arranged in the first line section (5a).
7. A vent valve comprising a valve body with a valve actuator (6a) designed as a movable valve body, with which a first valve connection can be switched to a second valve connection in a first switching state of the valve actuator (6a) and can be shut off in a second switching state, characterized in that the Valve actuator (6a) has a first pressurizable active surface which adjoins a first valve chamber (6b) connected to the second or a third valve connection and has at least one second pressurizable active surface which adjoins at least one second valve chamber (6d) connected to the second or a third valve connection, wherein the second active surface is subjected to a force by means of a spring element (6c), in particular a compression spring, wherein the first valve chamber (6b), in particular in the body of the vent valve, is connected to the second or third valve connection with a greater flow resistance than the second valve chamber (6d).
8. Vent valve according to claim 7, characterized in that the first valve chamber (6b) and the second valve chamber (6d) are connected to one another through the valve actuator via a connecting channel, in particular wherein the connecting channel forms the greater flow resistance in the connection between the first valve chamber (6b) and the second or third valve connection in comparison to the connection between the second valve chamber (6d) and the second or third valve connection, preferably wherein the connecting channel locally has a cross-sectionally tapered zone.
9. Vent valve according to claim 7 or 8, characterized in that the first valve chamber (6b) has an adjustable volume, in particular in that the valve chamber (6b) comprises two housing parts (6f, 6g) which delimit the valve chamber volume and which are displaceable relative to one another, in particular linearly, preferably wherein a first housing part (6f) can be inserted into a second housing part (6g).
10. Vent valve according to claim 9, characterized in that the first housing part (6f) has a connection at an axial end region to a sleeve (6h) coaxially surrounding the outside of the second housing part (6g), in particular wherein a threaded connection is formed between the inner wall of the sleeve (6h) and the outer wall of the second housing part (6g). REPLACEMENT SHEET (RULE 26) 11 .Method for depressurizing a drive chamber (2a, 2b) of a pneumatic drive (1), in particular a pneumatic drive (1) according to one of the preceding claims 1 to 6, wherein the depressurization of the drive chamber (2a, 2b) takes place by means of a throttle valve of a throttle unit (4), characterized in that the depressurization also takes place by means of an additional venting valve (6), in particular by means of a venting valve (6) according to one of the preceding claims 7 to 10, and the drive chamber (2a, 2b) is depressurized over a predetermined period of time by means of the venting valve (6) with a greater gas volume flow than by means of the throttle unit (4), wherein the period of time results from a pressure drop of different speeds in two valve chambers (6b, 6d), via which opposing forces act on a movable valve actuator (6a) in a pressure-dependent manner and which are connected to a common pressure sink (8) with different flow resistances.
12. Method according to claim 11, characterized in that in the predetermined time period one of the two forces (F1) which loads the valve actuator (6a) in the direction of an open position exceeds the other force (F2).
13. Method according to claim 11 or 12, characterized in that the predetermined time period is changed by a. adjusting the volume of that valve chamber (6b) via which the force (F1) is exerted, with which the valve actuator (6a) is loaded in the direction of the open position, and / or b. changing the flow resistance with which that valve chamber (6b) is connected to the common pressure sink (8), via which the force (F1) is exerted, with which the valve actuator (6a) is loaded in the direction of the open position, and / or c. adjusting the first partial force of the second force (F2) with which the valve actuator (6a) is loaded in the direction of the closed position, in particular by adjusting the preload path of a Compression spring, in particular with which an at least substantially constant or stroke-dependent force is generated.