Fluid return apparatus for a double-acting cylinder and method for operating such a cylinder

Abstract

In order to reduce fluid consumption, a fluid return apparatus is provided for a double-acting cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the cylinder and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the cylinder. The fluid return apparatus comprises a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet providing communication with the second fluid connection; an outlet providing communication with the piston-rod-side second cylinder chamber; a vent of the rapid venting valve, connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, which prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device.

Claims

1. A fluid return apparatus for a double-acting pneumatic cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the double-acting pneumatic cylinder to extend a piston rod of a piston in the cylinder, the first cylinder chamber facing away from the piston rod, and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the double-acting pneumatic cylinder to retract the piston, wherein the fluid return apparatus comprises: a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet, an outlet and a vent, wherein the inlet of the rapid venting valve provides communication with the second fluid connection; wherein the outlet of the rapid venting valve provides communication with the second cylinder chamber at the piston rod-side of the double-acting pneumatic cylinder, and wherein the vent of the rapid venting valve is connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, wherein the non-return fitting prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device, wherein the second fluid passage directly returns the fluid from the second cylinder chamber to the first cylinder chamber, when expanding the first fluid chamber to extend the piston rod, and when the fluid pressure in the second cylinder chamber is greater than the fluid pressure in the expanding the first cylinder chamber.

2. The fluid return apparatus according to claim 1, wherein the non-return fitting comprises a check valve.

3. The fluid return apparatus according to claim 1, wherein the auxiliary outlet device and the non-return fitting are connected to the vent of the rapid venting valve in parallel with one another.

4. The fluid return apparatus according to claim 1, wherein the auxiliary outlet device is adapted to limit an outlet volume flow of fluid flowing out from the auxiliary outlet device.

5. The fluid return apparatus according to claim 1, wherein the fluid return apparatus is a unit separate from the double-acting pneumatic cylinder.

6. A double-acting pneumatic cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the double-acting pneumatic cylinder, the first cylinder chamber facing away from a piston rod of a piston in the cylinder, to extend the piston rod, and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the double-acting pneumatic cylinder, wherein the double acting pneumatic cylinder has a fluid return apparatus comprising: a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet, an outlet and a vent, wherein the inlet of the rapid venting valve provides communication with the second fluid connection; wherein the outlet of the rapid venting valve provides communication with the second cylinder chamber at the piston rod-side of the double-acting pneumatic cylinder, and wherein the vent of the rapid venting valve is connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, wherein the non-return fitting prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device, wherein the first fluid passage is in fluid communication with the first cylinder chamber of the double-acting pneumatic cylinder facing away from the piston rod, and wherein the outlet of the rapid venting valve is in fluid communication with the second cylinder chamber at the piston rod-side of the double-acting pneumatic cylinder, wherein the second fluid passage directly returns the fluid from the second cylinder chamber to the first cylinder chamber, when expanding the first fluid chamber to extend the piston rod, and when the fluid pressure in the second cylinder chamber is greater than the fluid pressure in the expanding the first cylinder chamber.

7. The double-acting pneumatic cylinder according to claim 6, wherein the fluid return apparatus is integrated in the double-acting pneumatic cylinder.

8. A method of operating the double-acting pneumatic cylinder according to claim 6, including a step of returning at least a part of the fluid in the second cylinder chamber to the first cylinder chamber via the vent of the rapid venting valve when a volume of the second cylinder chamber is reduced.

9. An apparatus for operating a double-acting pneumatic cylinder having a first fluid connection for supplying fluid to a first cylinder chamber of the double-acting pneumatic cylinder, the first cylinder chamber facing away from a piston rod of a piston in the cylinder, to extend the piston rod, and a second fluid connection for supplying fluid to a second cylinder chamber at a piston rod-side of the double-acting pneumatic cylinder, wherein the double acting pneumatic cylinder has a fluid return apparatus comprising: a first fluid passage providing fluid communication between the first fluid connection and the first cylinder chamber; a rapid venting valve comprising an inlet, an outlet and a vent, wherein the inlet of the rapid venting valve provides communication with the second fluid connection, wherein the outlet of the rapid venting valve provides communication with the second cylinder chamber at the piston rod-side of the double-acting pneumatic cylinder, and wherein the vent of the rapid venting valve is connected by a second fluid passage to the first fluid passage; and a non-return fitting in the second fluid passage, wherein the non-return fitting prevents fluid from flowing from the first fluid passage to the rapid venting valve and an auxiliary outlet device, wherein the first fluid passage is in fluid communication with the first cylinder chamber of the double-acting pneumatic cylinder facing away from the piston rod, and wherein the outlet of the rapid venting valve is in fluid communication with the second cylinder chamber at the piston rod-side of the double-acting pneumatic cylinder, wherein the apparatus for operating the double-acting pneumatic cylinder comprises: a control valve with a fluid inlet and at least one fluid outlet, wherein the control valve is switchable between at least a first state and a second state, wherein in the first state the control valve connects the fluid inlet to the first fluid passage of the fluid return apparatus, and in the second state the control valve connects the fluid inlet to the inlet of the rapid venting valve of the fluid return apparatus and connects the first fluid passage of the fluid return apparatus to the at least one fluid outlet, wherein the second fluid passage directly returns the fluid from the second cylinder chamber to the first cylinder chamber, when expanding the first fluid chamber to extend the piston rod, and when the fluid pressure in the second cylinder chamber is greater than the fluid pressure in the expanding the first cylinder chamber.

10. The apparatus according to claim 9, further comprising a silencer connected to the at least one fluid outlet of the control valve.

Description

(1) In the figures schematically:

(2) FIG. 1 shows an embodiment of a fluid return apparatus according to the invention;

(3) FIG. 2 shows an apparatus for operating a double-acting cylinder which comprises the fluid return apparatus from FIG. 1 and a control valve;

(4) FIG. 3 shows a combination of a fluid return apparatus with a double-acting cylinder according to the invention, wherein the fluid return apparatus is integrated in the cylinder.

(5) The embodiment of a fluid return apparatus 1 according to the invention shown schematically in FIG. 1 comprises a housing 2, a rapid venting valve 3, a first fluid passage 7, a second fluid passage 8 with a non-return fitting which is configured as a check valve 9, an auxiliary outlet device 10 and four fluid connections 11, 12, 13, 14. The four fluid connections 11, 12, 13, 14 are configured as compressed air connections in the embodiment. The second fluid passage 8 produces a fluid communication from a vent 6 of the rapid venting valve 3 to the first fluid passage 7. The check valve 9 in the second fluid passage 8 prevents fluid from being able to flow from the first fluid passage 7 through the second fluid passage 8 in the direction of the vent 6. The check valve 9 therefore predefines a flow direction for fluid in the second fluid passage 8, wherein the vent 6 opens into an upstream end of the second fluid passage 8 and a downstream end of the second fluid passage 8 opens into the first fluid passage 7.

(6) In the embodiment shown in FIG. 1 the fluid return apparatus 1 is configured as a separate unit with the housing 2. The unit is adapted to be connected to a double-acting cylinder 20, as shown in FIG. 2. In this case, compressed air is used as fluid.

(7) A first cylinder-side fluid connection 12 is used for connection of a first cylinder chamber 21 of the double-acting cylinder 20 (not shown in FIG. 1, see FIG. 2) to the fluid return apparatus 1. A second cylinder-side fluid connection 14 is used for connection of a second cylinder chamber 22 of the same cylinder 20 to the fluid return apparatus 1.

(8) A first fluid connection 11 facing away from the cylinder is used for connection to a first fluid connection via which fluid can be provided for feeding into the first cylinder chamber 21. A second fluid connection 13 facing away from the cylinder is used for connection to a second fluid connection via which fluid can be provided for feeding into the second cylinder chamber 22.

(9) The first fluid passage 7 produces a direct fluid communication between the first fluid connection 11 facing away from the cylinder and the first cylinder-side fluid connection 12.

(10) The rapid venting valve 3 has an inlet 4, an outlet 5 and the vent 6.

(11) 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 communication can be connected to the inlet 4 and when the fluid return apparatus 1 is used as provided, it is connected accordingly.

(12) 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 communication can be connected to the piston-rod-side second cylinder chamber 22 and when the fluid return apparatus 1 is used as provided, it is connected accordingly.

(13) As mentioned above, the vent 6 is adjoined to the second fluid passage 8.

(14) The rapid venting valve 3 affords a rebound function in relation to a fluid communication from the inlet 4 to the outlet 5. Fluid can (at least substantially unhindered) flow out from the inlet 4 to the outlet 5 and flow out from the outlet 5.

(15) On the other hand, the rapid venting valve 3 prevents fluid from being able to flow out from the outlet 5 through the inlet 4. When fluid flows in through the outlet 5 into the rapid venting valve 3, it flows out through the vent 6 from the rapid venting valve 3.

(16) Preferably individual ones or all the fluid connections 11, 12, 13, 14 are executed as compressed air couplings in order to enable a simple and secure connection of the fluid return apparatus 1. Accordingly, the fluid return apparatus 1 can be easily removed again.

(17) The mode of operation and use of the fluid return apparatus 1 will now be explained in more detail with reference to FIG. 2.

(18) The same reference numbers are used for the same elements in the different figures and the corresponding explanations apply likewise for the different figures.

(19) In FIG. 2 the double-acting cylinder 20 and a control valve 30 are connected to the fluid return apparatus 1 from FIG. 1.

(20) The cylinder 20 shown in FIG. 2 comprises a double-acting pneumatic cylinder with a one-sided piston rod 24. Compressed air is used as fluid for movement of the piston. An interior space of the cylinder 20 is divided by a piston 23 into a first cylinder chamber 21 and a second cylinder chamber 22. The piston 23 is accommodated in the interior space of the cylinder 20 so that it can be moved along a longitudinal direction of the cylinder 20. A piston rod 24 is attached to the piston 23. The precisely one 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 projects from the interior space of the cylinder 20. The piston rod 24 thus transmits the movements of the piston 23 outwards.

(21) Consequently external objects can be moved by means of the piston rod 24 through the cylinder 20.

(22) In FIG. 2 the first cylinder chamber 21 facing away from the piston rod as provided is connected to the first cylinder-side fluid connection 12 of the fluid return apparatus 1 and the piston-rod-side second cylinder chamber 22 is connected as provided to the second cylinder-side fluid connection 14 of the fluid return apparatus 1. Consequently 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 rapid venting valve 3.

(23) In this embodiment the control valve 30 is a 5/2 way control valve for compressed air. A second fluid connection 32 (compressed air connection) of the control valve 30 is connected via a first fluid communication 51 to the first fluid connection 11 of the fluid return apparatus 1 facing away from the cylinder. A fourth fluid connection 34 of the control valve 30 is connected via a second fluid communication 52 to the second fluid connection 13 of the fluid return apparatus 1 facing away from the cylinder.

(24) As will become apparent, the first fluid communication 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 facing away from the piston rod. The second fluid communication 52 serves in particular as the second fluid connection for supplying fluid (more precisely compressed air) to the piston-rod-side second cylinder chamber 22 of the cylinder 20.

(25) 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 the present embodiment is configured 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 exhaused into the atmosphere.

(26) A fifth fluid connection 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 exhausted into the atmosphere.

(27) The control valve 30 can adopt two states.

(28) In a first state shown in FIG. 2, for extension of the cylinder 20 the control valve 30 connects the fluid inlet 31 to the second compressed air connection 32 and accordingly (via the first fluid communication 51 and the first compressed air connection 11 facing away from the cylinder) to the first fluid passage 7.

(29) In a second state not shown, for retraction of the cylinder 20 the control valve 30 connects the fluid inlet 31 to the fourth compressed air connection 34 and accordingly (via the second fluid communication 52 and the second compressed air connection 13 facing away from the cylinder) to the inlet 4 of the rapid venting valve 3. At the same time, in its second state the control valve connects its second fluid connection 32 (and therefore via the first fluid communication 51 and the first fluid connection 11 facing away from the cylinder the first fluid passage 7) to its first fluid outlet 33a.

(30) During extension of the double-acting cylinder 20 a residual excess pressure could occur in the second cylinder chamber 22 when the check valve 9 closes before the cylinder 20 is completely extended. This residual excess pressure could hinder or at least slow down a complete extension of the piston rod 24. Between the vent 6 and the check valve 9 the auxiliary outlet device 10 is therefore connected to the second fluid passage 8. The auxiliary outlet device 10 is consequently connected parallel to the check valve 9 to the vent 6. In the present exemplary 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. Through this outlet opening fluid (compressed air) can flow out into the surroundings. A flow cross-section of the outlet opening is substantially smaller than the flow cross-section of the second fluid passage 8. Therefore only a negligibly small proportion of the air displaced from the second cylinder chamber 22 during extension flows outwards through the outlet opening as long as the check valve 9 is open. However, the outlet opening is sufficient to reduce the residual excess pressure rapidly and in a controlled manner after closing the check valve 9. Consequently the auxiliary outlet device 10 counteracts the residual excess pressure. It thereby prevents or reduces a hindering of the extension of the cylinder 20 by such a residual excess pressure.

(31) FIG. 3 shows schematically a further embodiment according to the invention in which the fluid return apparatus 1 from FIGS. 1 and 2 is directly integrated in a cylinder 200. The first cylinder chamber 21, the second cylinder chamber 22, the piston 23 and the fluid return apparatus 1 are here formed jointly in a base body 202 of the cylinder 200. Accordingly, the fluid return apparatus 1 is here not configured as a separate unit.

(32) As a result, the entire structure is more compact, easier to handle and more cost-effective. Here the first fluid passage 7 is connected directly to the first cylinder chamber 21. Furthermore, the outlet 4 of the rapid venting valve 3 is connected directly to the second cylinder chamber 22 via a third fluid passage 25. Otherwise, the structure and operating mode correspond to the fluid return apparatus 1 from FIG. 1 and FIG. 2 and the cylinder 20 from FIG. 2.

(33) With the proposed fluid return apparatus 1 the compressed air consumption for the double-acting cylinder 20, 200 is reduced appreciably. At the same time, the retraction and extension force of the cylinder 20, 200 is fully maintained. At the same time, the time required for retraction is almost unchanged and the time required for extension is only slightly increased.

REFERENCE LIST

(34) 1 Fluid return apparatus

(35) 2 Housing

(36) 3 Rapid venting valve

(37) 4 Inlet

(38) 5 Outlet

(39) 6 Vent

(40) 7 First fluid passage

(41) 8 Second fluid passage

(42) 9 check valve

(43) 10 Auxiliary outlet device

(44) 11, 12, 13, 14 Fluid connection

(45) 20, 200 Cylinder

(46) 21 First cylinder chamber

(47) 22 Second cylinder chamber

(48) 23 Piston

(49) 24 Piston rod

(50) 25 Third fluid passage

(51) 30 Control valve

(52) 31 Fluid inlet

(53) 32, 34 Fluid connection

(54) 33a, 33b Fluid outlet

(55) 40 Fluid pressure source

(56) 41a, 41b Silencer

(57) 51, 52 Fluid communication

(58) 202 Base body