Control valve with safety function

Abstract

Control valve with - a control pressure chamber (24) which can be acted upon by a control pressure of a control medium, for displacing a control element (16) - and a working pressure area (26) for a working pressure medium, - wherein a first and a second seal (28a, 28b) are arranged between the control pressure chamber (24) and the working pressure area (26), - and wherein an intermediate region (32) is arranged between the first and the second seal (28a, 28b), - which is connected to a discharge area (29) by at least one line (34, 36) for discharging a leakage medium which is located in the intermediate area (32) in the event of a leak, - wherein the discharge region (29) is designed to supply the control element (16) with the leakage medium.

Description

[0001] The invention relates to a control valve and a motor unit with a motor and a control valve.

[0002] Control valves are used to perform a control function. They can be controlled by a control medium. For example, control valves can switch between two states or control within a control range.

[0003] Control valves are known, which are controlled by a pressurized fluid, for example, pneumatically or hydraulically, and are used to control consumers such as motors. Multi-way valves with a varying number of possible flow paths and connections are also known. Control valves are controlled by the position of a control element, such as a valve cone or cylinder.

[0004] DE 10 2006 026 792 A1 describes a pneumatic diaphragm pump. A piston rod is connected to two diaphragms. The piston rod is accommodated in the bearing bushing for longitudinal displacement. A control valve has a movable control piston pressurized with compressed air. A control channel is formed on the piston rod so that compressed air is directed via at least two different paths depending on the position of the piston rod relative to the bearing bushing. A first side of the control piston is continuously pressurized with an operating pressure during normal operation of the diaphragm pump.

[0005] DE 89 05 720 U1 discloses a valve for direct attachment to a rotating, pneumatically bidirectional device. The valve has a first compressed air inlet for actuation in one direction and a second compressed air inlet for actuation in the other direction, as well as an outlet for the air consumed during each actuation. The hoses of a direct control unit can be connected to the two compressed air inlets. When the first compressed air inlet is pressurized, the valve connects the second compressed air inlet to the outlet, and when the second compressed air inlet is pressurized, the valve connects the first compressed air inlet to the outlet.

[0006] DE 28 53 506 A1 describes a hydraulically actuated directional control valve with three switching positions. One center position is spring-centered. The control piston has recesses on both sides in which centering springs and a section of support bodies are located to support the centering springs. These support bodies rest on the housing part.

[0007] The task can be considered to propose a control valve and a motor unit for which there is a reduced risk of malfunction.

[0008] The object is achieved by a control valve according to claim 1 and a motor unit with a motor and a control valve according to claim 11. Dependent claims relate to advantageous embodiments of the invention.

[0009] The control valve according to the invention comprises a control pressure chamber, which can be subjected to a control pressure for displacing a control element. Furthermore, a working pressure area for a working pressure medium is provided. A first and a second seal are arranged between the control pressure chamber and the working pressure area. An intermediate area is arranged between the two seals, which is connected to a discharge area by at least one line for discharging a leakage medium located in the intermediate area in the event of a leak.

[0010] The control pressure chamber is designed to accommodate the control medium, which pressurizes the control element in such a way that a controlled displacement of the control element occurs. The control pressure chamber can be a cavity of any shape. In particular, the control pressure chamber can comprise at least one control connection through which the control medium can be introduced into the control pressure chamber. The control pressure chamber is arranged such that its pressurization acts on the control element and can thus cause displacement.

[0011] The working pressure area is designed to accommodate a working pressure medium. For this purpose, the working pressure area comprises a working pressure supply connection. A working pressure area that is part of the control element and can thus be moved with the control element is particularly preferred.

[0012] The control medium and the working pressure medium can be any liquid, for example oil, or any gas. These are preferably gases. The control medium and the working pressure medium can be the same medium; preferably, they are compressed air. The respective pressure can be freely selected. The pressures can be the same or different. The pressure of the working pressure medium is preferably between atmospheric pressure and 10 bar, more preferably 5 to 8 bar. The pressure of the working pressure medium is particularly preferably 6 bar. The control pressure is preferably variable and is less than 6 bar, particularly preferably between 1.2 bar and 2 bar.

[0013] The working pressure area and the control chamber are sealed from each other by the seals arranged between them. The seals form a barrier for the working pressure medium and the control medium, thus preventing pressure exchange between the control pressure chamber and the working pressure area. The seals are preferably attached to the control element. The seals are also preferably made of a flexible material, such as flexible plastic or rubber.

[0014] Between the first and second seals is the intermediate region, which is designed to accommodate the leakage medium. The spaced-apart first and second seals form and delimit the intermediate region. The leakage medium can be the control medium, which can escape from the control pressure chamber in the event of a failure and overcome one of the two seals.

[0015] The leakage medium can also be the working pressure medium, which in the event of a failure can leave the working pressure zone and pass through one of the two seals. The intermediate zone prevents the leakage medium from overcoming the second seal and thus passing from the working pressure zone into the control pressure chamber.

[0016] A simple and preferred design of the line connecting the intermediate region with the discharge region can be realized by a material recess, for example by a bore, which runs through the control element.

[0017] The discharge area can be a cavity of any shape, which is designed to receive or pass through the leakage medium discharged through the line.

[0018] The control valve according to the invention prevents the leaking medium from overcoming both seals in the event of a leak, as it is diverted before overcoming the second seal. This prevents the working pressure medium from passing from the working pressure area into the control pressure chamber, or from inadvertently flowing from the control pressure chamber into the working pressure area. This prevents hazardous malfunctions in the event of a leak and increases safety. In particular, it prevents the working pressure medium from overflowing into the control chamber and thus unintentionally controlling the control element.

[0019] According to the invention, the diverting region is designed to pressurize the control element with the leakage medium in the closing direction. Preferably, the diverting region is attached directly to the control element, so that pressurizing the diverting region exerts an effect on the control element in the direction of the closing position. Preferably, the diverting region and the control pressure chamber are arranged on opposite sides of the control element, so that their effects oppose each other.

[0020] In a further development of the control valve, the control element can be moved between an open position and a closed position. In the open position, the working pressure area is connected to a working port so that the working pressure medium is guided through the valve to the working port. In the closed position, the working pressure area is separated from the working port so that in the closed position the control element is positioned such that the flow of the working pressure medium to the working port is interrupted. In the closed position, the working pressure medium is therefore not guided through the valve. The working port is designed, for example, to be connected to a consumer, such as an actuator, and to supply this with the working pressure medium. The working port can thus represent a connection point between the control valve and the consumer.The control valve preferably has a working pressure supply connection for a working pressure supply, via which the working pressure medium can be provided. Particularly preferably, the working pressure supply is a compressed air supply. According to this refinement, the control valve then directs the medium of the working pressure supply to the working connection in the open position and interrupts the line of the working pressure medium in the closed position, preventing it from passing from the working pressure supply to the working connection.

[0021] In a preferred embodiment, a return element is designed to urge the control element toward the closed position. The return element can be any component designed to preload the control element toward the closed position. Preferably, the return element is a spring element, more preferably a coil spring, and most preferably a compression spring. Furthermore, the return element is preferably mounted between the control element and a counterbearing.

[0022] In a preferred embodiment of the control valve, the control pressure chamber and the reset element are arranged so that their effects oppose each other. Particularly preferably, the control pressure chamber and the reset element are mounted on opposite sides of the control element, so that their effects on the control element oppose each other. Further preferably, the reset element provides an effect on the control element toward the closed position, and the control pressure chamber provides an effect toward the open position.

[0023] According to an alternative development, a vent connection point is provided between the discharge area and an outside area. The outside area can preferably be the environment outside the control valve. According to the advantageous development, the vent connection point is designed to prevent a pressure buildup in the discharge area by diverting the leakage medium, passing through the discharge area, into the outside area.

[0024] In a preferred embodiment of the control valve, the reset element is arranged in the discharge area. This advantageously results in a compact design.

[0025] In an advantageous development, the control element is arranged displaceably in a surrounding enclosure. The surrounding enclosure can be designed as desired. Preferably, the surrounding enclosure substantially surrounds the control element. According to the advantageous development, the control element is displaceable in the surrounding enclosure between the open position and the closed position. Preferably, the enclosure surrounds the control element such that the latter can only be displaced along one axis. Particularly preferably, there is a close fit between the control element and the surrounding enclosure, so that only a small gap remains between them. Further preferably, the working pressure region can surround the control element and is delimited by the surrounding enclosure. It is further preferred that the working connection and / or the working pressure supply connection can be formed by material recesses in the surrounding enclosure.

[0026] According to an advantageous embodiment, the first and second seals are slidably mounted between the control element and the surrounding enclosure. Preferably, the first and second seals are mounted on the control element in such a way that displacement of the control element also causes displacement of both seals. Particularly preferably, the control element has a groove for each seal, which accommodates the respective seal. Preferably, the seals are mounted in such a way that the control element is slidably displaceable in the surrounding enclosure, and the fluid flow between the control element and the surrounding enclosure is limited at the location of the seal.

[0027] In a further advantageous embodiment of the control valve, the control element is a piston located in a cylinder liner. The piston is preferably cylindrical with circular surfaces as end faces. Correspondingly, the cylinder liner preferably has a circular cross-section. A rotationally symmetrical design of the piston and the corresponding cylinder liner is particularly preferred. According to this advantageous embodiment, the working pressure region at least partially surrounds the piston. Particularly preferably, the working pressure region surrounds the piston as a circular ring which has the cylinder axis as its center. The working pressure region is preferably formed by a material recess in the piston and is delimited by the cylinder liner.

[0028] In an advantageous development, a portion of the line runs essentially parallel to the longitudinal axis of the piston. Preferably, the line runs within the piston. According to this advantageous development, the line connects the intermediate region with the discharge region, with the intermediate region and discharge region preferably being arranged on opposite end surfaces of the piston. Particularly preferably, the line runs along the center axis of the cylindrical piston. The line is preferably a bore extending through the piston.

[0029] An embodiment of the control valve according to the invention is explained in more detail below with reference to the drawings. The figures show: Fig. 1 a sectional view of an embodiment of a control valve in a closed position, Fig. 2 a sectional view of the control valve according to Fig. 1 in an opening position, Fig. 3 a sectional view of the control valve according to Fig. 1 and Fig. 2 in a closed position in case of failure, Fig. 4 a pneumatic circuit diagram of a motor unit with a control valve.

[0030] Fig. 1 shows an embodiment of a control valve 10. The control valve 10 comprises a housing 12 with a bore 14 in which a piston 16 is slidably mounted.

[0031] A control pressure chamber 24 is located adjacent to a first end face 18 of the piston 16. The control valve 10 can be controlled via a control connection 30, a connection for a control medium. A spring 22 is mounted on the opposite side of the piston 16. The spring 22 is a compression spring 22 that is mounted between the piston 16 and a boundary formed by the housing 12.

[0032] The piston 16 is cylindrical, and the housing 12 is a cylinder liner. Both are rotationally symmetrical about a cylinder axis X. The piston 16 is movable within the housing along the cylinder axis X.

[0033] A working pressure region 26 is arranged around the piston 16. The working pressure region 26 is formed by a notch in the piston 16, which is annular and rotationally symmetrical to the cylinder axis X. Except for the notch of the working pressure region 26, the outer surface of the piston 16 directly borders the inner surface of the housing 12. The working pressure region 26 is delimited by the inner surface of the housing 12 and by the piston 16.

[0034] Four grooves are formed in the outer surface of the piston 16 in the areas directly adjacent to the inner surface of the housing 12. Sealing rings 28a-28d are located in these grooves. The sealing rings 28a-28d are thus mounted between the outer surface of the piston 16 and the inner surface of the housing 12. Two sealing rings 28a, 28b are located between the working pressure area 26 and the control pressure chamber 24. The sealing rings 28a, 28b are spaced apart from one another to define an intermediate area 32. The other two sealing rings 28c, 28d are arranged on the opposite side of the working pressure area 26.

[0035] Within the intermediate region 32, the piston 16 has a radial bore 34 which has openings on the upper side of the jacket surface so that it traverses the piston 16 in its longest radial extent perpendicular to the cylinder axis X. There may also be additional radial bores 34, for example a total of three. Additional radial bores 34 result in a higher overall volume flow of the leakage medium being able to be diverted, thereby increasing the reliability of the control valve 10. In the center, the radial bore 34 is connected to a longitudinal bore 36 which runs along the cylinder axis X. The radial bore 34 and the longitudinal bore 36 run perpendicular to one another. The longitudinal bore 36 opens into a diversion region 29 which also represents a receiving cavity for the compression spring 22. In the illustrated embodiment, the diversion region 29 is connected to the environment of the control valve 10 via a vent valve 42.

[0036] Fig. 4 shows a pneumatic circuit diagram of a motor unit with the control valve 10. A compressed air supply 46 is connected to the working pressure area 26 via a supply connection 38. A pneumatic motor 48 is connected to a working connection 40 in order to control it with a working pressure medium from the compressed air supply 46. The pneumatic motor 48 can, for example, be controlled to raise and lower a hoist 52 using a chain sprocket 50. For such a control, the control valve 10 connects the supply connection 38 to the working connection 40 or separates the two from each other, so that, in the case of a connection, the compressed air from the compressed air supply 46 can flow via the control valve 10 to the pneumatic motor 48. The control valve 10 is controlled via a control pressure of the control medium, which is admitted into the control pressure chamber 24 via the control connection 30 in accordance with the desired control.

[0037] Fig. 1 shows the control valve 10 in a closed state. In the closed state, the piston 16 is in a closed position, in the outermost position toward the control pressure chamber 24. No control pressure acts on the end face 18 to overcome the restoring force of the compression spring 22. The compression spring 22 is at its maximum possible extension in the control valve 10. Although the working pressure area 26 is connected to the supply port 38, in the closed position the working pressure area 26 and the working port 40 are spatially separated from one another. Consequently, the supply port 38 and the working port 40 are not connected to one another, no working pressure medium can flow through the control valve 10, and the control valve 10 is closed.In order to ensure that no working pressure medium can reach the working connection 40 from the working pressure area 26 in the closed state, the sealing ring 28c forms a barrier between the working pressure area 26 and the working connection 40. The sealing ring 28d forms a barrier between the working connection 40 and the rear part of the bore 14, which is created as soon as the piston 16 is moved in the direction of the control pressure chamber 24 by the restoring force of the compression spring 22.

[0038] Fig. 2 shows the control valve 10 in an open state. In the open state, the control pressure in the control pressure chamber 24 acts on the piston 16, causing it to move against the spring force of the compression spring 22. In contrast to the closed position, the compression spring 22 is in a compressed state. Compared to the closed position, the piston 16 is moved in the direction of the compression spring 22 in the open position. The working pressure area 26 is moved with the piston 16. The supply port 38 remains connected to the working pressure area 26. Additionally, in the open state, the working pressure area 26 is connected to the working port 40. Consequently, the supply port 38 is connected to the working port 40, and the working pressure medium can flow from the compressed air supply 46 to the working port 40.

[0039] The control valve 10 can therefore be controlled between two states via a control port 30 using a control pressure. In the closed state, no working pressure medium flows, and in the open state, the volume flow of the working pressure medium is at its maximum. The control pressure can be adjusted so that any state between the open state and the closed state can be achieved. These states form a control range with states in which the volume flow of the working pressure medium is present but lower than in the open state.

[0040] An adjustable volume flow of the working pressure medium is available at the working connection, which, for example, drives the pneumatic motor 48 ( Fig. 4). For such applications, safe operation is relevant and malfunctions must be prevented to avoid hazards. To ensure proper control, it is therefore important that the working pressure medium and the control medium cannot leave the working pressure area 26 or the control pressure chamber 24 via the gap between the piston 16 and the inner surface of the cylinder liner 12. If, for example, when the control valve 10 is closed, the working pressure medium flows from the working pressure area 26 into the control pressure chamber 24, the piston 16 is subjected to the pressure of this leakage medium. This can lead to a displacement of the piston 16 and thus to an opening of the control valve 10. The sealing rings are used to prevent the working pressure medium and the control medium from leaving the intended area.However, there is a risk that the sealing rings do not form a sufficient barrier and that pressure may leak, for example, from the working pressure area 26 into the control pressure chamber 24.

[0041] Fig. Figure 3 shows a fault scenario for the control valve 10. In the event of a failure, for example, of the sealing ring 28b, the transition between the outer surface of the piston 16 is a leak point despite the sealing ring 28b, and compressed air flows from the working pressure area 26 into the intermediate area 32. In the illustrated leak scenario, the compressed air, the leakage medium, does not flow further via the second sealing ring 28a into the control pressure chamber 24, but is first guided through the radial bore 34 into the longitudinal bore 36 and further into the discharge area 29. The leakage medium is guided out of the control valve 10 into the environment via the vent valve 42. The path of the leakage medium, which leaves the working area 26 at a leakage point, reaches the intermediate area 32 and reaches the environment via the radial and longitudinal bores 34, 36 and the discharge area 29, is in Fig. 3 marked by an arrow.

[0042] Since in the event of a leak, compressed air from the working pressure area 26 is prevented from entering the control pressure chamber 24, an unwanted pressurization of the piston 16 in the direction of the opening position is prevented.

[0043] An alternative embodiment of the control valve 10 (not shown) does not include a vent valve 42. The leakage medium is not discharged into the environment, but instead pressurizes the piston 16. This pressurization counteracts the pressurization by the control pressure and thus has an effect on the piston 16 toward its closed position. This further reduces the risk of the control valve opening accidentally.

Claims

[1] Control valve with - a control pressure chamber (24) which can be acted upon by a control pressure of a control medium, for displacing a control element (16) - and a working pressure area (26) for a working pressure medium, - wherein a first and a second seal (28a, 28b) are arranged between the control pressure chamber (24) and the working pressure area (26), - and wherein an intermediate region (32) is arranged between the first and the second seal (28a, 28b), - which is connected to a discharge area (29) by at least one line (34, 36) for discharging a leakage medium which is located in the intermediate area (32) in the event of a leak, - wherein the discharge region (29) is designed to supply the control element (16) with the leakage medium. [2] Control valve according to claim 1, wherein - the control element (16) is displaceable between an opening position and a closing position, - and wherein in the opening position the working pressure area (26) is connected to a working connection (40) and in the closing position the working pressure area (26) is separated from the working connection (40). [3] Control valve according to claim 2, wherein - a return element (22) is designed to urge the control element (16) towards the closed position. [4] Control valve according to claim 3, wherein - the control pressure chamber (24) and the return element (22) are arranged so that their effects are opposite to each other. [5] Control valve according to claim 3 or 4, wherein - the return element (22) is arranged in the discharge area (29). [6] Control valve according to one of the preceding claims, wherein - a venting connection point (42) is provided between the discharge area (29) and an outside area. [7] Control valve according to one of the preceding claims, wherein - the control element (16) is arranged displaceably in a surrounding enclosure (12). [8] Control valve according to claim 7, wherein - the first and second seals (28a, 28b) are slidably mounted between the control element (16) and the surrounding enclosure (12). [9] Control valve according to one of the preceding claims, wherein - the control element (16) is a piston in a cylinder liner. [10] Control valve according to claim 9, wherein - a part of the line (36) runs parallel to the longitudinal axis of the piston. [11] Motor unit comprising a motor (48) and a control valve (10) according to any one of claims 2-10, wherein - the motor (48) is connected to the working connection (40).

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