FLUID PRESSURE DEVICE FOR A DOUBLE-ACTING PNEUMATIC CYLINDER AND METHOD FOR OPERATING SUCH A PNEUMATIC CYLINDER

Description

[0001] The invention relates to a fluid return device for a double-acting pneumatic cylinder. The invention further relates to a device for operating a double-acting pneumatic cylinder and a method for operating a double-acting pneumatic cylinder.

[0002] In double-acting pneumatic cylinders, the cylinder's interior is divided by a piston into a first cylinder chamber (away from the piston rod) and a second cylinder chamber (away from the piston rod). A piston rod is attached to the piston and extends outwards through the second cylinder chamber. The cylinder—or more precisely, the piston rod—is extended by introducing compressed air into the first cylinder chamber. This increases the volume of the first cylinder chamber while simultaneously decreasing the volume of the second cylinder chamber as the piston moves to one side of the second cylinder chamber.

[0003] It has already been proposed to connect quick-release valves to the cylinder chambers of pneumatic cylinders so that the fluid can escape more quickly from the respective cylinder chamber when its volume is reduced, for example in DE 26 48 358 A1 and DE 38 04 081 A1. In this case, the air is discharged from the affected cylinder chamber to the outside environment.

[0004] Energy-saving circuits can improve the efficiency of pneumatic cylinders. Such energy-saving circuits are described, for example, in the book "Energy Analysis and Improvement of the Drive Technology of Pneumatic Handling Systems," author Jan Hepke, 1st edition 2017, ISBN 978-3-8440-5254-1.

[0005] DE 20 2015 003 307 U1 discloses a pneumatic control system with compressed air recirculation for a pneumatic cylinder. To extend the pneumatic cylinder, a directional control unit switches a compressed air line from a cylinder chamber on the piston rod side to a cylinder chamber on the opposite side. Simultaneously, the cylinder chamber on the piston rod side, which is still pressurized, is connected to a vent line leading to a vent control unit. A bypass line with a check valve branches off from the vent line. Due to the still high pressure in the cylinder chamber on the piston rod side, compressed air flows into the vent line. The high pressure there, via a control line connected to a compressed air supply control unit, causes the compressed air supply to be temporarily interrupted. Therefore, the pressure in the cylinder chamber on the opposite side remains low.Due to the pressure difference between the two cylinder chambers, compressed air flows from the vent line through the bypass line towards the cylinder chamber furthest from the piston rod. When the pressures in both cylinder chambers become approximately equal, the vent control opens via control lines, the pressure in the vent line and in the cylinder chamber furthest from the piston rod drops, the compressed air supply control unit opens, and the cylinder chamber furthest from the piston rod is supplied with fresh compressed air. The pneumatic cylinder then extends.

[0006] WO 2008 / 060168 A1 shows a hydraulic actuator with a piston, a cylinder chamber on the opposite side of the piston rod, and a cylinder chamber on the opposite side of the piston rod. A first hydraulic line is connected to the cylinder chamber on the opposite side of the piston rod via a hydraulic valve, and a second hydraulic line is connected to the cylinder chamber on the opposite side of the piston rod. To retract the piston, fluid is supplied via the first hydraulic line. It flows through a check valve inside the hydraulic valve and into the cylinder chamber on the opposite side of the piston rod. To extend the piston, fluid is supplied to the cylinder chamber on the opposite side of the piston rod via the second hydraulic line. Fluid in the cylinder chamber on the opposite side of the piston rod is forced out and flows to the hydraulic valve.Since the return path to the first hydraulic line is blocked by the check valve, the fluid from the cylinder chamber on the piston rod side moves a movable slider against the force of a spring, thereby opening a passage to the cylinder chamber on the opposite side. Consequently, fluid flows from the cylinder chamber on the piston rod side into the cylinder chamber on the opposite side.

[0007] WO 2012 / 129042 A1 shows a hydraulic circuit with a check valve that allows fluid return from a cylinder chamber on the piston rod side to a cylinder chamber on the opposite side, but prevents reverse flow. The fluid return is controlled by an electro-hydraulic proportional control valve.

[0008] WO 2012 / 045320 A1 describes a piston-cylinder unit with a housing in which a working cylinder is arranged. A piston on a piston rod divides the working cylinder into a feed cylinder chamber on the side opposite the rod and a piston ring side on the side opposite the rod. A changeover valve establishes a fluid connection between a first fluid connection, the piston ring side, and the feed cylinder chamber during extension, and a fluid connection between a second fluid connection and the piston ring side during retraction.

[0009] From DE 1 816 402 A1, a hydraulic system with a working cylinder is known. A changeover valve is connected between the pressure medium lines to the cylinder chambers; its open port is connected to a pressure relief valve connected to a return line and to one of the cylinder chambers, while the other cylinder chamber is connected directly to one of the pressure medium lines.

[0010] However, existing solutions have the disadvantage of requiring many components or additional control functions. This makes retrofitting existing installations particularly difficult and costly.

[0011] Furthermore, the use of known energy-saving circuits partially reduces the insertion or extension force of the double-acting pneumatic cylinder. Depending on the operating principle, the piston's movement speed may also be reduced in at least one of these directions.

[0012] The object of the present invention is to provide a device and a method by which fluid consumption during the operation of a double-acting cylinder is reduced.

[0013] The problem is solved by a fluid return device for a double-acting pneumatic cylinder with the features of claim 1.

[0014] The fluid return device for the double-acting pneumatic cylinder, which can be connected to or is connected to a first fluid supply for supplying fluid to a first cylinder chamber of the pneumatic cylinder located away from the piston rod and to a second fluid supply for supplying fluid to a second cylinder chamber of the pneumatic cylinder located on the piston rod side, comprises: a first fluid passage to establish a fluid connection between the first fluid connection and the first cylinder chamber; a quick-release valve with an inlet for connection to the second fluid connection, an outlet for connection to the piston rod-side, second cylinder chamber of the pneumatic cylinder, and a vent connected to the first fluid passage by a second fluid passage; and a check valve in the second fluid passage that prevents fluid from flowing from the first fluid passage to the quick-release valve.

[0015] The first fluid passage can be designed, for example, as a line, a pipe, a hose or a channel provided in a base body.

[0016] When the fluid return device is connected to the double-acting (pneumatic) cylinder, the first cylinder chamber can be supplied with fluid via the first fluid passage to extend the cylinder (more precisely: a piston rod of the double-acting cylinder). Fluid flows from the first fluid connection through the first fluid passage into the first cylinder chamber. The first fluid connection is thus used as a first fluid supply.

[0017] As the cylinder extends, the volume of the second cylinder chamber decreases, and fluid flows from this chamber to the outlet of the quick-release valve and into the valve itself. The quick-release valve prevents the fluid from flowing from its outlet to its inlet and out of the inlet. Instead, it allows the fluid from the second cylinder chamber to continue flowing through the quick-release valve's vent into the second fluid passage.

[0018] The quick-release valve acts similarly to a check valve with respect to a fluid connection between its inlet (and the associated second fluid connection) and its outlet (and the associated second cylinder chamber).

[0019] As mentioned above, a check valve is provided in the second fluid passage. If the fluid pressure in the second fluid passage on one side of the quick-release valve's vent (upstream side) is higher than the fluid pressure in the first fluid passage, fluid flows from the quick-release valve's vent through the second fluid passage and the check valve within it into the first fluid passage and finally reaches the first cylinder chamber. This ensures that, when the cylinder extends, at least some of the fluid displaced from the second cylinder chamber by a piston of the double-acting cylinder is returned to the first fluid passage and ultimately to the first cylinder chamber. In other words, the quick-release valve and the second fluid passage serve to return fluid from the second cylinder chamber to the first cylinder chamber.

[0020] The double-acting cylinder is a double-acting cylinder with a single-ended piston rod. The cylinder's interior is divided by the piston into a first cylinder chamber (away from the piston rod) and a second cylinder chamber (on the side of the piston rod). The piston rod extends through the second cylinder chamber. Therefore, the effective cross-sectional area of ​​the second piston chamber on one side of the second cylinder chamber is smaller than the effective cross-sectional area of ​​the first piston chamber on the other side of the first cylinder chamber. This allows the fluid pressure in the second cylinder chamber to exceed the fluid pressure in the first cylinder chamber if fluid, such as compressed air, is supplied to the first cylinder chamber from the outside (via the first fluid connection and the first fluid passage).This pressure difference makes it possible and energetically advantageous to return fluid from the second cylinder chamber to the first cylinder chamber in the manner described.

[0021] Because of the fluid recirculation, significantly less fluid needs to be supplied via the first fluid connection to extend the double-acting cylinder. For example, the fluid recirculation device saves 24% compressed air during a complete cylinder cycle (extension and retraction). This considerably improves the efficiency of the connected cylinder, making its operation more cost-effective, energy-efficient, and environmentally friendly. Ultimately, this also reduces CO₂ emissions.

[0022] If the fluid return device is connected to the double-acting cylinder, the second cylinder chamber can be supplied with fluid via the quick-release valve. Fluid flows from the second fluid connection into the inlet of the quick-release valve and then through the outlet of the quick-release valve into the second cylinder chamber. The second fluid connection thus serves as a secondary fluid supply during retraction. The piston moves, increasing the volume of the second cylinder chamber and decreasing the volume of the first cylinder chamber. Fluid in the first cylinder chamber can escape through the first fluid passage and then via the first fluid connection. Alternatively or additionally, the fluid can escape from the first cylinder chamber via another route when the cylinder (or its piston rod) is retracted.

[0023] During the initial setup, the cylinder can be operated as if it were connected conventionally without a fluid return device.

[0024] A key advantage of the quick-release valve is its ability to reliably close its inlet for fluid return, thus ensuring the backflow of fluid from its outlet to its vent. Conversely, it opens its inlet and closes its vent when fluid is supplied at increased pressure from the second fluid connection. This allows a reliable supply of fluid to the second cylinder chamber for cylinder retraction. Simultaneously, no fluid supplied from the second fluid connection can enter the second fluid passage unintentionally, as the vent is closed during retraction.

[0025] One advantage of the fluid return device is its simple design. It is cost-effective and space-saving. Furthermore, its integration is simple, inexpensive, and quick. It can be used with any double-acting pneumatic cylinder with a single-ended piston rod.

[0026] The fluid return device according to the invention is further characterized in that the extension force when extending the cylinder remains at least substantially the same when using the fluid return device. Preferably, the extension force of the double-acting cylinder is reduced by less than 10% when using the fluid return device, more preferably by less than 5%, and most preferably by less than 2%. This particularly implies that the extension force of the double-acting cylinder is equal to or even greater when using the fluid return device than without it.

[0027] Alternatively or additionally, the fluid return device according to the invention is characterized in that the retraction force when retracting the cylinder remains at least substantially the same when using the fluid return device. Preferably, the retraction force of the double-acting cylinder is reduced by less than 10%, more preferably by less than 5%, and most preferably by less than 2% when using the fluid return device.

[0028] As a comparison in this sense, the same cylinder is operated under the same conditions without the fluid return device, with the first cylinder chamber being connected directly to the first fluid connection in a conventional manner and the second cylinder chamber being directly connected to the second fluid connection.

[0029] The fluid return device can therefore be used without hesitation in existing installations, without any significant reduction in performance. To do this, the fluid return device is simply connected as described between the first fluid connection and the first cylinder chamber, and between the second fluid connection and the second cylinder chamber.

[0030] Preferably, the fluid is air. In particular, the first fluid connection can serve as a primary compressed air supply. Alternatively or additionally, the second fluid connection can serve as a secondary compressed air supply. Air is readily available and inexpensive. It can be supplied easily, cost-effectively, quickly, and in large quantities using known methods.

[0031] In a further advantageous embodiment, the check valve assembly includes a non-return valve. A non-return valve assembly is particularly preferred. This contributes to a simple, compact, and cost-effective design.

[0032] In a further development of the invention, the inlet, outlet, and / or vent of the quick-release valve are each designed as a fluid connection, particularly preferably as a compressed air connection, and most preferably as a compressed air coupling. This enables a simple and secure, and optionally detachable, connection of the quick-release valve.

[0033] The fluid return device preferably includes fluid connections for connection to the first cylinder chamber, the second cylinder chamber, the first fluid connection, and / or the second fluid connection, most preferably compressed air connections, and most preferably compressed air couplings. This ensures easy handling and installation of the fluid return device. In particular, it allows for quick and easy retrofitting.

[0034] In a further development of the invention, the flow cross-section of the second fluid passage is approximately the same size as the flow cross-section of the first fluid passage. In a particularly preferred embodiment of the invention, the flow cross-section of the second fluid passage is at most 30% larger or smaller than the flow cross-section of the first fluid passage, most preferably by at most 20%, and most preferably by at most 10%. This significantly increases the energy benefit of recirculating fluid from the second cylinder chamber into the first fluid passage and into the first cylinder chamber. However, if the flow cross-section of the second fluid passage becomes larger, its volume also increases, and the pressure within it decreases. This impairs the energy gain from the recirculation.If the cross-sectional area of ​​the second fluid passage decreases, this tends to lead to a higher pressure within it, but the volume of fluid returned to the first cylinder chamber decreases or may even be insufficient. Therefore, it is advantageous if the cross-sectional area of ​​the second and first fluid passages is approximately the same.

[0035] Alternatively or additionally, the flow cross-section of the second fluid passage is a maximum of 30% larger or smaller than a flow cross-section of the first fluid connection, a flow cross-section of the second fluid connection, a flow cross-section of a fluid connection between the outlet of the quick-release valve and the second cylinder chamber and / or as a flow cross-section of a fluid connection between the first fluid passage and the first cylinder chamber (if present), Most preferably by a maximum of 20%, extraordinarily preferably by a maximum of 10%. This dimensioning of the second fluid passage ensures a particularly high energy efficiency of the recirculation.

[0036] The fluid return device includes an auxiliary outlet device. The auxiliary outlet device is designed to counteract any residual overpressure in the second cylinder chamber when the cylinder is extended. It can, for example, be configured to release fluid into the environment or into a collection container.

[0037] Preferably, the auxiliary outlet device is configured so that fluid can flow out of the fluid return device from the second cylinder chamber at least when the check valve is closed and the cylinder is being extended at the same time.

[0038] As mentioned, the check valve prevents fluid from flowing from the first fluid passage through the second fluid passage to the quick-release valve. Therefore, no fluid can escape from the first fluid passage through the auxiliary outlet device. For example, the check valve, designed as a non-return valve, can close when the cylinder extends if the fluid pressure in the first fluid passage is the same. At the same time, however, the quick-release valve prevents fluid flowing into the outlet from escaping through the inlet when the cylinder extends. Consequently, it is possible that a residual overpressure relative to a reference pressure, such as ambient pressure, remains in the second cylinder chamber. This residual overpressure can slow down or even prevent the cylinder from fully extending.As mentioned above, the auxiliary exhaust device is designed to counteract the residual overpressure in the second cylinder chamber when the cylinder is extended (that is, to reduce or completely prevent such residual overpressure).

[0039] According to the invention, the auxiliary outlet device is connected to the vent of the quick-release valve in parallel with the check valve. It is connected to the second fluid passage between the vent and the check valve.

[0040] This enables simple and cost-effective integration.

[0041] The auxiliary outlet device may, for example, include an outlet opening, a throttle and / or a controllable valve.

[0042] In a simple case, the auxiliary outlet device is, for example, an outlet opening whose flow cross-section is significantly smaller than the flow cross-section of the second fluid passage. Particularly preferably, the flow cross-section of the outlet opening is at most 10% of the flow cross-section of the second fluid passage, more preferably at most 3%, and extraordinarily preferably at most 1%.

[0043] If the pressure difference between the fluid pressure in the first fluid passage and the fluid pressure at the quick-release valve's vent is large, for example, midway through cylinder extension, the fluid displaced from the second cylinder chamber is allowed to pass through the check valve and, due to its larger flow diameter, flows primarily through the second fluid passage into the first. Because of the smaller flow diameter of the outlet port, only a small fraction of the fluid displaced from the second cylinder chamber is released through the outlet port. When the piston approaches its maximum extension position, and the pressure difference disappears, and the check valve closes, a limited volume of fluid will still escape from the second cylinder chamber and be discharged through the outlet port until the residual pressure dissipates.This allows the residual overpressure to drop in a controlled manner to ambient pressure, and the cylinder can be extended fully, at least essentially without hindrance.

[0044] Preferably, the auxiliary outlet device limits the outlet volume flow rate at which fluid can flow out of the auxiliary outlet device. This can be achieved, for example, by limiting the area of ​​the outlet opening. This reduces the fluid losses at the outlet.

[0045] Alternatively or additionally, the auxiliary outlet device includes an outlet mechanism configured to close a fluid outlet to the environment if the fluid pressure in the first fluid passage is greater than the fluid pressure at the vent of the quick-release valve by at least a specified amount, and to open it otherwise. The specified amount can be an absolute pressure difference and / or a pressure ratio. In particular, the specified amount can correspond to a pressure difference of zero. This ensures that no fluid is lost at all when the cylinder extends, as long as fluid is being recirculated. However, such a solution is more complex than the small outlet opening described above.

[0046] Preferably, the auxiliary outlet device is integrally formed with the quick-release valve, particularly with its vent, the second fluid passage, and / or the check valve. This saves installation space, simplifies production, and reduces costs. However, the auxiliary outlet device can also be formed by one or more separate components.

[0047] In a preferred embodiment of the invention, the fluid return device is designed as a separate unit for connection to the double-acting cylinder. This makes the fluid return device particularly easy to manufacture.

[0048] Furthermore, it can be easily, cost-effectively, quickly and without problems retrofitted into existing systems, without having to replace the cylinder or a control valve for the cylinder itself.

[0049] Another aspect of the invention relates to a combination of the fluid return device with the double-acting cylinder.

[0050] In particular, the invention also relates to a double-acting pneumatic cylinder comprising a fluid return device according to one of the described embodiments, wherein the first fluid passage is in fluid communication with the first cylinder chamber of the pneumatic cylinder facing away from the piston rod, and wherein the outlet of the quick-release valve is in fluid communication with a second cylinder chamber of the pneumatic cylinder on the piston rod side.

[0051] The first effective cross-sectional area of ​​the piston on the side opposite the piston rod (on the side of the first cylinder chamber) is larger than the second effective cross-sectional area of ​​the piston on the side opposite the piston rod (on the side of the second cylinder chamber).

[0052] In other words, the second effective cross-sectional area is smaller than the first effective cross-sectional area. Preferably, the size of the second effective cross-sectional area is 40% to 95% of the first effective cross-sectional area, more preferably 70% to 90%, and most preferably 80% to 90%. This ensures, on the one hand, a sufficiently high fluid pressure in the second cylinder chamber for fluid return during retraction, and on the other hand, that the retraction force is still sufficiently high compared to the extension force.

[0053] Preferably, the double-acting cylinder is a double-acting pneumatic cylinder with exactly one single-ended piston rod. However, it is also possible for the piston to have multiple piston rods (i.e., at least two). For example, two piston rods can be attached to the piston, both extending side by side through the first cylinder chamber to the outside. Multiple double-acting cylinders can also be provided.

[0054] In a further development of the invention, the fluid return device and the cylinder are arranged together in a housing and / or formed together in a base body. This makes the system consisting of the fluid return device and the double-acting cylinder particularly compact and cost-effective. Furthermore, the elimination of intermediate connections, especially detachable ones, avoids potential sources of malfunction. In particular, the fluid return device can be integrated into the double-acting cylinder.

[0055] In another preferred embodiment of the invention, the fluid return device is designed as a separate unit. The double-acting cylinder and the fluid return device can have a coupling device for a detachable connection between the double-acting cylinder and the actual fluid return device. This allows the two elements to be quickly and easily separated or connected, serviced, and, if necessary, quickly replaced.

[0056] The fluid return device and / or the cylinder are preferably designed for a fluid pressure or operating pressure of at least 0.15 MPa, particularly preferably in the range between 0.3 and 1.6 MPa, for example 0.6 MPa.

[0057] According to a further aspect, a device according to the invention for operating the double-acting pneumatic cylinder comprises a fluid return device according to one of the previously described embodiments, as well as a control valve with a fluid inlet and at least one fluid outlet, which can assume at least two states. In a first state, the control valve connects the fluid inlet to the first fluid passage of the fluid return device, and in a second state, the control valve connects the fluid inlet to the inlet of the quick-release valve of the fluid device and the first fluid passage of the fluid return device to the at least one fluid outlet.

[0058] The fluid inlet is designed for connection to a fluid pressure source. The at least one fluid outlet is provided for the discharge of fluid from the device.

[0059] In the first state, the inlet of the quick-release valve is not connected to the fluid inlet. Therefore, no fluid is supplied to the quick-release valve and the second cylinder chamber from the fluid inlet in this first state. In the second state, the first fluid passage is not connected to the fluid inlet.

[0060] In a further development of the device, the fluid inlet of the control valve is connected to a fluid pressure source. This allows the fluid inlet of the control valve to be supplied with fluid under increased pressure. Preferably, the fluid pressure source provides compressed air. The fluid pressure provided by the fluid pressure source is preferably at least 0.15 MPa, and particularly preferably in the range between 0.3 and 1.6 MPa, for example at 0.6 MPa.

[0061] Alternatively or additionally, a silencer is connected to at least one fluid outlet of the control valve. This dampens the noise of fluid (e.g., compressed air) flowing from the at least one fluid outlet.

[0062] In particular, the device may include the silencer.

[0063] The control valve is preferably a 4 / 3-way valve. It is particularly preferred that the 4 / 3-way valve is closed in an intermediate position between the first state and the second state.

[0064] In another particularly preferred embodiment of the invention, the control valve is a 5 / 2-way valve. This solution is even more cost-effective. In particular, in this case, the control valve can have a second fluid outlet in addition to the at least one fluid outlet.

[0065] In a further development of the invention, the control valve, in the first state, also connects the inlet of the quick-release valve to a fluid outlet of the control valve. This can be, for example, at least one fluid outlet or an additional fluid outlet. This prevents an increased fluid pressure from remaining at the inlet of the quick-release valve when the control valve is switched to the first state. Any potential fluid flow from the inlet of the quick-release valve to its outlet is thus reliably prevented during the first state.

[0066] The control valve and the fluid return device can be designed as a single unit. For example, both can be housed in a common casing and / or formed in a common base body. In particular, the control valve can be integrated into the fluid return device. The fluid return device comprising the control valve can be designed as a separate unit for connection to the double-acting cylinder.

[0067] In another embodiment, the control valve, the fluid return device, and the double-acting cylinder are provided as a single unit. In particular, the control valve and the fluid return device can both be integrated into the double-acting cylinder.

[0068] The above-mentioned problem is further solved by a method for operating a double-acting pneumatic cylinder with the features of claim 10.

[0069] Preferably, a fluid return device according to one of the previously described embodiments is used for the method.

[0070] The designs and advantages described for the fluid return device, the combination of the fluid return device with the double-acting (pneumatic) cylinder, the device for operating the double-acting (pneumatic) cylinder and for the method also apply accordingly to the other items.

[0071] The invention is explained below with reference to exemplary embodiments and the figures.

[0072] They show schematically: Fig. 1 shows an embodiment of a fluid return device according to the invention; Fig. 2 shows a device for operating a double-acting cylinder, which includes the fluid return device. Fig. 1 and includes a control valve; Fig. 3 a combination of a fluid return device according to the invention with a double-acting cylinder, wherein the fluid return device is integrated into the cylinder.

[0073] The in Fig. 1 A schematically illustrated embodiment of a fluid return device 1 according to the invention comprises a housing 2, a quick-release valve 3, a first fluid passage 7, a second fluid passage 8 with a check valve 9, an auxiliary outlet 10, and four fluid connections 11, 12, 13, 14. In this embodiment, the four fluid connections 11, 12, 13, 14 are designed as compressed air connections. The second fluid passage 8 establishes a fluid connection from a vent 6 of the quick-release valve 3 to the first fluid passage 7. The check valve 9 in the second fluid passage 8 prevents fluid from flowing from the first fluid passage 7 through the second fluid passage 8 towards the vent 6.The check valve 9 thus specifies a flow direction for fluid in the second fluid passage 8, with the vent 6 opening into an upstream end of the second fluid passage 8 and a downstream end of the second fluid passage 8 opening into the first fluid passage 7.

[0074] In the Fig. 1 In the illustrated embodiment, the fluid return device 1 is designed as a separate unit with the housing 2. The unit is configured as shown in Fig. 2 shown to be connected to a double-acting cylinder 20. Compressed air is used as the fluid in this case.

[0075] A first cylinder-side fluid connection 12 serves to connect a first cylinder chamber 21 of the double-acting cylinder 20 (in Fig. 1 not shown Fig. 2 ) to the fluid return device 1. A second cylinder-side fluid connection 14 serves to connect a second cylinder chamber 22 of the same cylinder 20 to the fluid return device 1.

[0076] A first fluid connection 11, located away from the cylinder, serves to connect to a first fluid supply, through which fluid can be provided for feeding into the first cylinder chamber 21. A second fluid connection 13, also located away from the cylinder, serves to connect to a second fluid supply, through which fluid can be provided for feeding into the second cylinder chamber 22.

[0077] The first fluid passage 7 establishes a direct fluid connection between the first fluid port 11 facing away from the cylinder and the first fluid port 12 on the side of the cylinder.

[0078] The quick vent valve 3 has an inlet 4, an outlet 5 and a vent 6.

[0079] The inlet 4 is in direct fluid communication with the second fluid connection 13 facing away from the cylinder. More generally, it is provided that the second fluid connection can be connected to the inlet 4 and is connected accordingly when the fluid return device 1 is used as intended.

[0080] The outlet 5 is in direct fluid communication with the second cylinder-side fluid connection 14. More generally, it is provided that the second fluid connection can be connected to the piston rod-side, second cylinder chamber 22 and is connected accordingly when the fluid return device 1 is used as intended.

[0081] As mentioned above, the second fluid passage 8 connects to the vent 6.

[0082] The quick-release valve 3 provides a check valve function with respect to the fluid connection from inlet 4 to outlet 5. Fluid can flow (at least essentially) unimpeded from inlet 4 to outlet 5 and out of outlet 5. Conversely, the quick-release valve 3 prevents fluid from flowing out of outlet 5 through inlet 4. If fluid flows into the quick-release valve 3 through outlet 5, it flows out of the quick-release valve 3 through vent 6.

[0083] Preferably, one or all of the fluid connections 11, 12, 13, 14 are designed as pneumatic couplings to enable easy and safe connection of the fluid return connection 1. Accordingly, the fluid return connection 1 can also be easily removed.

[0084] The operation and use of the fluid return device 1 will now be described with reference to Fig. 2 explained in more detail.

[0085] The same reference symbols are used for identical elements in the different figures, and the corresponding explanations apply equally to the different figures.

[0086] In Fig. 2 are the double-acting cylinder 20 and a control valve 30 connected to the fluid return device 1. Fig. 1 connected.

[0087] At the in Fig. 2 The cylinder 20 shown is a double-acting pneumatic cylinder with a single-ended piston rod 24. Compressed air is used as the fluid to move the piston. The interior of the cylinder 20 is divided into a first cylinder chamber 21 and a second cylinder chamber 22 by a piston 23. The piston 23 is movably mounted within the interior of the cylinder 20 along a longitudinal direction. A piston rod 24 is attached to the piston 23. This single piston rod 24 of the cylinder 20 extends from the piston 23 along the longitudinal direction of the cylinder 20 through the second cylinder chamber 22 and protrudes from the interior of the cylinder 20. The piston rod 24 thus transmits the movements of the piston 23 to the outside. Consequently, external objects can be moved through the cylinder 20 by means of the piston rod 24.

[0088] In Fig. 2 The first cylinder chamber 21, located away from the piston rod, is connected as intended to the first cylinder-side fluid port 12 of the fluid return device 1, and the second cylinder chamber 22, located on the piston rod side, is connected as intended to the second cylinder-side fluid port 14 of the fluid return device 1. Thus, the first cylinder chamber 21 is in direct fluid communication with the first fluid passage 7, and the second cylinder chamber 22 is in direct fluid communication with the outlet 5 of the quick-release valve 3.

[0089] In this configuration, the control valve 30 is a 5 / 2-way control valve for compressed air. A second fluid port 32 (compressed air port) of the control valve 30 is connected via a first fluid connection 51 to the first fluid port 11 of the fluid return device 1, which is furthest from the cylinder. A fourth fluid port 34 of the control valve 30 is connected via a second fluid connection 52 to the second fluid port 13 of the fluid return device 1, which is furthest from the cylinder.

[0090] As will become apparent, the first fluid connection 51 serves in particular as the first fluid connection for supplying fluid (more precisely, compressed air) to the first cylinder chamber 21 of the cylinder 20, which is located away from the piston rod. The second fluid connection 52 serves in particular as the second fluid connection for supplying fluid (more precisely, compressed air) to the second cylinder chamber 22 of the cylinder 20, which is located on the piston rod side.

[0091] A first compressed air connection of the control valve 30 serves as a fluid inlet 31 and is in fluid communication with a fluid supply source 40, which in this embodiment is designed as a compressed air source. A third fluid connection of the control valve 30 serves as a first fluid outlet 33a of the control valve 30. A first silencer 41a is connected to the first fluid outlet 33a, through which compressed air can be released into the atmosphere.

[0092] A fifth fluid port of the control valve 30 serves as a second fluid outlet 33b of the control valve 30. A second silencer 41b is connected to the second fluid outlet 33b, through which compressed air can be released into the atmosphere.

[0093] The control valve 30 can assume two states.

[0094] In a Fig. 2 In the first state shown, for extending the cylinder 20, the control valve 30 connects the fluid inlet 31 with the second compressed air connection 32 and therefore (via the first fluid connection 51 and the first compressed air connection 11 facing away from the cylinder) with the first fluid passage 7.

[0095] In a second state, not shown, for retracting the cylinder 20, the control valve 30 connects the fluid inlet 31 to the fourth compressed air connection 34 and thus (via the second fluid connection 52 and the second compressed air connection 13 facing away from the cylinder) to the inlet 4 of the quick-release valve 3. At the same time, in its second state, it connects its second fluid connection 32 (and thus, via the first fluid connection 51 and the first fluid connection 11 facing away from the cylinder, the first fluid passage 7) to its first fluid outlet 33a.

[0096] When the double-acting cylinder 20 is extended, residual overpressure could occur in the second cylinder chamber 22 if the check valve 9 closes before the cylinder 20 is fully extended. This residual overpressure could hinder or at least slow down the complete extension of the piston rod 24. Therefore, the auxiliary outlet device 10 is connected to the second fluid passage 8 between the vent 6 and the check valve 9. The auxiliary outlet device 10 is thus connected to the vent 6 in parallel with the check valve 9. In this embodiment, the auxiliary outlet device 10 consists of a small outlet opening. The outlet opening can be a small bore in the vent 6 itself or in the second fluid passage 8 between the vent 6 and the check valve 9. Fluid (compressed air) can escape into the environment through this outlet opening.The flow cross-section of the outlet opening is significantly smaller than the flow cross-section of the second fluid passage 8. Therefore, only a negligible fraction of the air displaced during extension from the second cylinder chamber 22 flows outwards through the outlet opening as long as the check valve 9 is open. However, the outlet opening is sufficient to dissipate the residual overpressure quickly and in a controlled manner after the check valve 9 closes. Consequently, the auxiliary outlet device 10 counteracts the residual overpressure. This prevents or reduces any obstruction of the cylinder 20's extension by such residual overpressure.

[0097] In Fig. 3 schematically shows another embodiment according to the invention, in which the fluid return device 1 is made of Fig. 1 and 2The first cylinder chamber 21, the second cylinder chamber 22, the piston 23, and the fluid return device 1 are together formed in a base body 202 of the cylinder 200. Accordingly, the fluid return device 1 is not designed as a separate unit.

[0098] This makes the overall design more compact, easier to handle, and more cost-effective. Here, the first fluid passage 7 is directly connected to the first cylinder chamber 21. Furthermore, the outlet 4 of the quick-release valve 3 is directly connected to the second cylinder chamber 22 via a third fluid passage 25. Otherwise, the design and operation of the fluid return device 1 correspond to the one described above. Fig. 1 and Fig. 2 and of cylinder 20 from Fig. 2 .

[0099] With the proposed fluid recirculation 1, the compressed air consumption for the double-acting cylinders 20, 200 is significantly reduced. At the same time, the extension and retraction forces of the cylinders 20, 200 remain fully intact. Furthermore, the time required for retraction is practically unchanged, and the extension time is only slightly increased. Bezugszeichenliste:

[0100] 1 Fluid return device 2 Housing 3 Quick vent valve 4 Inlet 5 Outlet 6 Vent 7 First fluid passage 8 Second fluid passage 9 Check valve 10 Auxiliary outlet device 11, 12, 13, 14 Fluid connection 20, 200 Cylinder 21 First cylinder chamber 22 Second cylinder chamber 23 Piston 24 Piston rod 25 Third fluid passage 30 Control valve 31 Fluid inlet 32, 34 Fluid connection 33a, 33b Fluid outlet 40 Fluid pressure source 41a, 41b Silencer 51, 52 Fluid connection 202 Base body

Claims

1. Fluid return apparatus (1) for a double-acting pneumatic cylinder (20, 200), which connectable or connected to a first fluid connection (51) for supplying fluid to a first cylinder chamber (21) of the pneumatic cylinder (20, 200) facing away from the piston rod and to a second fluid connection (52) for supplying fluid to a piston-rod-side, second cylinder chamber (22) of the pneumatic cylinder (20, 200), wherein the fluid return apparatus (1) comprises: a first fluid passage (7) for producing a fluid communication between the first fluid connection (51) and the first cylinder chamber (21); an auxiliary outlet device (10); and a non-return fitting (9); characterized by a rapid venting valve (3) with an inlet (4) for communication with the second fluid connection (52), an outlet (5) for communication with the piston-rod-side second cylinder chamber (22) of the pneumatic cylinder (20, 200), and a vent (6), which is connected by a second fluid passage (8) to the first fluid passage (7); wherein the non-return fitting (9) is arranged in the second fluid passage (8) and prevents fluid from flowing from the first fluid passage (7) to the rapid venting valve (3), wherein the auxiliary outlet device (10) is connected to the vent (6) of the rapid venting valve (3) in parallel to the non-return fitting (9).

2. Fluid return apparatus (1) according to Claim 1, characterized in that the non-return apparatus (9) is configured as a check valve.

3. Fluid return apparatus (1) according to any one of the preceding claims, characterized in that the auxiliary outlet device (10) is formed integrally with the rapid venting valve (3), especially with its vent (6), with the second fluid passage (8) and / or with the non-return fitting (9).

4. Fluid return apparatus (1) according to one of the preceding claims, characterized in that the auxiliary outlet device (10) limits an outlet volume flow at which fluid can flow out from the auxiliary outlet device (10).

5. Fluid return apparatus (1) according to one of the preceding claims, characterized in that the fluid return apparatus (1) is configured as a separate unit for connection to the double-acting pneumatic cylinder (20).

6. Double-acting pneumatic cylinder (200), comprising a fluid return apparatus (1) according to one of Claims 1 to 4, wherein the first fluid passage (7) is in fluid communication with a first cylinder chamber (21) of the pneumatic cylinder (200) facing away from the piston rod and wherein the outlet (5) of the rapid venting valve (3) is in fluid communication with a piston-rod-side, second cylinder chamber (22) of the pneumatic cylinder (200).

7. Double-acting pneumatic cylinder (200) according to Claim 6, characterized in that the fluid return apparatus (1) is integrated in the pneumatic cylinder (200).

8. Apparatus for operating a double-acting pneumatic cylinder (20, 200), comprising: a fluid return apparatus (1) according to one of the preceding Claims 1 to 5 or a double-acting pneumatic cylinder (200) according to one of Claims 6 or 7; and a control valve (30) with a fluid inlet (31) and at least one fluid outlet (33a) which can adopt at least two states; wherein the control valve (30) - in a first state connects the fluid inlet (31) to the first fluid passage (7) of the fluid return apparatus (1) and - in a second state connects the fluid inlet (31) to the inlet (4) of the rapid venting valve (3) of the fluid return apparatus (1) and connects the first fluid passage (7) of the fluid return apparatus (1) to the at least one fluid outlet (33a).

9. Apparatus according to Claim 8, characterized in that the apparatus comprises a silencer (41a) which is connected to the at least one fluid outlet (33a) of the control valve (30).

10. Method for operating a double-acting pneumatic cylinder (20, 200) having a first cylinder chamber (21) facing away from the piston rod and a piston-rod-side, second cylinder chamber (22), wherein a first fluid passage (7) provides a fluid connection between a fluid connection (51) for supplying fluid to the first cylinder chamber (21) and the first cylinder chamber (21); characterized in that at least a part of the compressed air in the second cylinder chamber (22) is returned into the first cylinder chamber (21) via a vent (6) of a rapid venting valve (3) when a volume of the second cylinder chamber (22) is reduced, wherein an inlet (4) of the rapid venting valve (2) is connected to a second fluid connection (52) for supplying fluid to the second cylinder chamber (22), an outlet (5) of the rapid venting valve (3) is connected to the piston-rod-side second cylinder chamber (22), the vent (6) of the rapid venting valve (3) is connected by a second fluid passage (8) to the first fluid passage (7), wherein an auxiliary outlet device (10) is connected to the vent (6) of the rapid venting valve (3) in parallel to a non-return fitting (9), which prevents fluid from flowing from the first fluid passage (7) to the rapid venting valve (3), wherein the auxiliary outlet device (10) is connected to the vent (6) of the rapid venting valve (3) in parallel to the non-return fitting (9).