Valve arrangement

Abstract

Valve arrangement comprising at least one multi-way valve (2) comprising a main valve (4) and a pilot valve (5) for actuating the main valve (4), wherein the main valve (4) comprises a main valve element (8) which can be selectively positioned in a first switching position or in a second switching position and which can control the fluid connection between several main valve channels (16), among which is a main feed channel (16a) supplied with working compressed air from a working compressed air source (PA) during operation of the valve arrangement (1), wherein the main valve element (8) is constantly acted upon in the direction of the first switching position by an air spring (LF) formed by air spring compressed air and can be actuated with pilot compressed air to switch to the second switching position.the pilot channel (38) which is controllable by means of the pilot valve (5) and which, during operation of the valve arrangement (1), is connected to a pilot compressed air source (PV) independently of the main feed channel (16a), wherein the main feed channel (16a) and the pilot channel (38) are formed separately from each other within the multi-way valve (2) without any mutually influencing fluid connection, and wherein the multi-way valve (2) has an outer surface (42) on which the main feed channel (16a) and the pilot channel (38) open independently of each other with spaced-apart channel openings (44, 43), wherein the channel opening (44) of the main feed channel (16a) is provided for connection to the working compressed air source (PA) and the channel opening (43) of the pilot channel (38) is provided for connection to the pilot compressed air source (PV), characterized in thatthat the compressed air for the air spring (LF) used to form the air spring is branched off from the main feed channel (16a) of the main valve (4) without a connection to the pilot channel (38) within the main valve (4), wherein the separately formed channel openings (44, 43) of the main feed channel (16a) and the pilot channel (38) are formed on a surface section of the outer surface (42) of the multi-way valve (2) designed as a mounting surface (45), wherein the valve arrangement (1) has a valve carrier (3) separate from the multi-way valve (2), which is provided with a mounting surface (46) to which the multi-way valve (2) can be attached with its mounting surface (45) and which is penetrated by valve carrier channels (48) that connect to the main valve channels (16) opening at the mounting surface (45) and to the pilot channel also opening at the mounting surface (45). (38) of the multi-way valve (2) mounted on the mounting surface (46) communicate.

Description

The invention relates to a valve arrangement having at least one multiway valve which has a main valve and a pilot valve serving for actuating the main valve, wherein the main valve has a main valve member which can be positioned selectively in a first switching position or in a second switching position and which can control the fluid connection between a plurality of main valve channels, among which there is a main feed channel which is supplied with working compressed air from a working compressed air source during operation of the valve arrangement, wherein the main valve member is constantly acted upon in the direction of the first switching position by an air spring formed by compressed air spring and can be acted upon with pilot compressed air for switching to the second switching position, which pilot compressed air can be provided by a pilot channel which can be controlled by means of the pilot valve and is connected to a pilot compressed air source during operation of the valve arrangement independently of the main feed channel, wherein the main feed channel and the pilot channel are formed separately from one another within the multiway valve without any influencing mutual fluid connection, and wherein the multiway valve has an outer surface at which the main feed channel and the pilot channel open out independently of one another with mutually spaced channel openings, wherein the channel opening of the main feed channel is provided for connection to the working compressed air source and the channel opening of the pilot channel is provided for connection to the pilot compressed air source.A valve arrangement of this type known from the data sheet "Magnetolettei VSVA-B-M52-AZD-A2-1T1L", pages 1 / 2 and 2 / 2, 05.08.2016 of Festo AG & Co. KG is concerned with a pilot-controlled monostable multiway valve, the main valve of which has a main valve member which is constantly prestressed into a first switching position by an air spring. By actuating a pilot valve, the main valve member can be supplied with pilot compressed air and switched into a second switching position counter to the spring force of the air spring. The compressed air used for generating the air spring, which can be designated as air spring compressed air, is branched off from a pilot control duct of the pilot control valve. The main valve is able, depending on its position assumed, to connect a main feed channel supplied with a working compressed air selectively to one of two further main valve channels, in order to actuate, for example, a connected pneumatic drive.During operation of the valve arrangement, the working compressed air and the pilot compressed air are supplied to the multiway valve separately from one another, which offers the possibility of selecting different pressure levels and, if required, of switching off the pilot valve in terms of pressure without impairing the compressed air supply to the main valve.A valve device known from DE 10 2010 049 935 A1 likewise represents a monostable multiway valve in which the main valve member of a main valve is prestressed into a first switching position by an air spring. The air spring compressed air required for generating the air spring is branched off directly from the main feed channel of the main valve, as is the pilot compressed air used for operating the pilot valve.A valve arrangement known from DE 10 2013 016 652 A1 contains a plurality of electro-pneumatically pilot-controlled multiway valves which are installed jointly on a valve carrier. In addition to the pilot operated multiway valves, the known valve arrangement is equipped with a safety valve which is capable of switching off the pilot compressed air to be supplied to the pilot valves of the multiway valves as required. Each multiway valve contains two pilot valves which, on the basis of the pilot compressed air which can be shut off by the safety valve, are capable of acting on and moving a main valve member for selective positioning in one of two switching positions in one or the other direction.DE 201 06 018 U1 relates to a multiway valve for carrying out two two-way control functions, two three-way control functions or a two-way control function combined with a three-way control function, wherein in each case both control functions are simultaneously brought about by a single valve slide which is arranged in a slide receptacle of the valve housing and cooperates with control surfaces which are arranged in the slide receptacle in a manner fixed to the housing in accordance with the desired control functions.DE 100 10 690 A1 shows a valve which has a control device serving for controlling fluid flows, which control device can be caused to switch over movements in two mutually opposite switching directions. In order to make possible a delay-free switching over even after relatively long standstill times, a drive device is provided which has spring means which are tensioned when the control device reaches an end switching position. The energy stored in this case is available for increasing the force during the subsequent changeover movement.The invention is based on the object of taking measures which, when a multiway valve deactivated on the pilot side is put into operation again, can prevent undesired movements of a connected pneumatic drive.To achieve this object, in a valve arrangement of the type mentioned at the beginning, it is provided that the compressed air spring serving for forming the air spring is branched off from the main feed channel of the main valve without a connection to the pilot channel within the main valve, wherein the channel openings of the main feed channel and of the pilot channel, which openings are formed separately from one another, are formed on a surface section of the outer surface of the multiway valve, which surface section is formed as a mounting surface, wherein the valve arrangement has a valve carrier which is separate with respect to the multiway valve and is provided with a placement surface to which the multiway valve is attachable or attached by its mounting surface and which is traversed by valve carrier channels which communicate with the main valve channels which open on the mounting surface and the pilot channel of the multiway valve which is mounted on the placement surface and which likewise opens on the mounting surface.The valve arrangement according to the invention contains at least one monostable multiway valve, the main valve member of which is prestressed into a first switching position by an air spring. The compressed air required for forming the air spring, which is referred to as air spring compressed air, is branched off from the main feed channel of the main valve, which, during operation of the valve arrangement, is connected to an external compressed air source, which, for better differentiation, is referred to as working compressed air source. The pilot valve of the multiway valve is capable of supplying the main valve member of the main valve with a pilot compressed air in the opposite direction with respect to the spring force of the air spring in order to switch over the main valve member into a second switching position overcoming the spring force of the air spring and to retain it there for as long as desired. The pilot compressed air is supplied to the pilot passage controllable by the pilot valve not through branching from the main feed passage of the main valve but separately from a pilot compressed air source. As a result, there is no mutually influencing connection between the air spring and the pilot control duct. If the pilot compressed air fails during operation of the multiway valve or if it is intentionally switched off, this does not influence the air spring function. It is even the case that the main valve member which is currently held in the second switching position on the basis of a corresponding operating position of the pilot valve is switched back into the first switching position by the air spring if the pilot compressed air source is intentionally or on the basis of a fault disconnected from the pilot duct while the main valve member is in the second switching position. Thus, after intentional or disturbance-based switching off of the pilot compressed air, the main valve member always assumes the first switching position, which results in reproducible conditions when switching on again. A pneumatic drive connected to the multiway valve can consequently not execute any uncontrolled movements when the pilot compressed air is switched on again. A significant safety aspect of the valve arrangement is thus that the operating state of the pilot control valve does not affect the existence and effectiveness of the air spring.Advantageous further developments of the invention are evident from the dependent claims.The air spring compressed air required for forming the air spring is branched off from the main feed channel inside the main valve. This enables a very short channel guidance and allows a cost-effective integration of the required branch channel into the valve housing of the main valve.The valve member expediently has two first and second drive surfaces oriented opposite one another. The first drive surface delimits an air spring chamber which is permanently connected to the main feed channel and is separated from the pilot channel. The second drive surface delimits a drive chamber connected to the pilot channel. By controlled fluid application of pilot compressed air to the drive chamber, the main valve member can be switched between the first and second switching positions and held in the desired switching position as required.The valve member is preferably accommodated in an axially displaceable manner in a working chamber of the main valve, which working chamber has two mutually opposite end portions, one of which forms the air spring chamber and the other of which forms the drive chamber.The air spring chamber is preferably connected to the main feed channel via a branch channel which has no connection to the pilot channel. The branch channel runs, for example, in a valve housing of the main valve or passes through the main valve member.The pilot valve is in particular designed such that it divides the pilot channel into a pilot drive section connected to the drive chamber and a pilot feed section connected to the pilot compressed air source during operation of the valve arrangement. The pilot valve can interrupt or release the fluid connection between the pilot feed section and the pilot drive section depending on the operating state. When the connection is released, the pilot compressed air is applied to the main valve member, which consequently experiences a driving force which counteracts the air spring force and switches over the main valve member from the first switching position into the second switching position and holds it there.The pilot valve is preferably provided with a 3 / 2 valve function, and connects the pilot driving portion to a pilot exhaust passage communicating with the atmosphere in the state separated from the pilot supply portion. This allows the driving chamber to be vented to remove the driving force applied to the main valve member, thereby causing the main valve member to be switched to the first switching position by the air spring force.It is expedient to make the first drive surface of the main valve member delimiting the air spring chamber smaller than the second drive surface delimiting the drive chamber. As a result, even at the same pressure level of the air spring pressure corresponding to the working pressure and of the pilot pressure, a reliable switching over of the main valve member from the first switching position into the second switching position and consequently a reliable monostable operating mode can be ensured without additional pressure reducing measures.The fluid pressures provided by the working compressed air source and by the pilot compressed air source can be of different sizes. For example, the pilot pressure is lower than the working pressure. Preferably, however, the fluid pressures are of equal magnitude.Within the multiway valve, the main feed channel and the pilot channel are formed separately from one another without any influencing mutual fluid connection.The main feed channel and the pilot control channel open out with mutually spaced channel openings independently of one another on an outer surface of the multiway valve. The channel orifice of the main feed channel is provided for connection to the external working compressed air source and the channel orifice of the pilot channel is provided for connection to the external pilot compressed air source.The surface section of the outer surface of the multiway valve, which surface section has the channel openings of the main feed channel and of the pilot channel, is designed as a mounting surface with which the multiway valve can be mounted in front on a mounting surface of a valve carrier of the valve arrangement. The valve carrier can have a plurality of placement surfaces, which can each be equipped with a multiway valve designed according to the invention. The valve carrier is traversed by valve carrier channels which communicate with the main valve channels of the main valve which open out on the mounting surface and also with the pilot channel which likewise opens out on the mounting surface. Thus, all fluid communication with respect to a multiway valve can take place through the valve carrier.The main valve passages of the main valve suitably comprise, in addition to the main feed passage, at least one main working passage provided for connection to a load and at least one main venting passage connected to the atmosphere. If these two channels are present twice, the main valve can perform a 5 / 2 valve function, otherwise a 3 / 2 valve function. Depending on the switching position of the main valve member, each main working channel can be connected in one switching position to the main feed channel and in the other switching position to a main venting channel.In an advantageous embodiment, the valve arrangement has a cut-off valve connected between the pilot channel and the pilot compressed air source, which valve offers the possibility of disconnecting the pilot channel from the pilot compressed air source and of switching the pilot valve inoperative. Even if the pilot valve is operated in the pilot passage isolated from the pilot compressed air source, for example, by manual or electric operation, it cannot switch the switching position of the main valve member in the absence of the required pilot compressed air. Preferably, the pilot channel is vented to the atmosphere in the interruption position of the interrupter valve separating the pilot channel from the pilot compressed air source.The main valve of the multiway valve is preferably a slide valve, the main valve member of which is designed as a piston slide.The pilot valve is preferably of an electrically operable type. It suitably comprises an electromagnetic or piezoelectric actuator. The pilot valve has in particular a 3 / 2 valve function with a monostable characteristic.The invention is explained in more detail below with reference to the attached drawings. The single FIG. (FIG. 1 ) illustrates in a partially schematic representation and partially in section a preferred embodiment of the valve arrangement according to the invention, wherein the main valve member is illustrated when the first switching position caused by the air spring is assumed.The valve arrangement denoted in its entirety by reference numeral 1 contains at least one multiway valve 2 and is formed in a simple case exclusively by such a multiway valve 2. In contrast to this, the valve arrangement 1 can also contain a plurality of multiway valves 2.The valve arrangement 1 also comprises a valve carrier 3, which is indicated merely by dash-dot lines in FIG. 1 and which is expediently equipped or can be fitted detachably with at least one multiway valve 2. The valve arrangement 1 illustrated by way of example is equipped with such a valve carrier 3, which, however, represents only an optional equipment variant.The multiway valve 2 is of an electro-pneumatically pilot-controlled design. It has a main valve 4 and a pilot valve 5 which is expediently combined with the main valve 4 to form a structural unit. The pilot valve 5 can expediently be actuated electrically and is used for pneumatic actuation of the main valve 4.The main valve 4 comprises a valve housing, referred to as main valve housing 6, in which a longitudinal cavity, referred to as working chamber 7, is formed for better differentiation. In the working chamber 7 there is a valve member of the main valve 4, referred to as main valve member 8 for better differentiation, which valve member is preferably designed as a piston slide, since the main valve 4 is in particular a slide valve.The working chamber 7 has a longitudinal axis 7a with which a longitudinal axis 8a of the valve member 8 coincides. The valve member 8 can be switched over between two switching positions in the working chamber 7 by performing a linear switching movement 11 indicated by a double arrow, which is oriented in the axial direction of the two longitudinal axes 7 a, 8 a, relative to the main valve housing 6. FIG. 1 illustrates a first switching position of the two switching positions, in which the main valve member 8 assumes a position, for example, which is close to the pilot valve 5. The first switching position is defined, for example, in that the main valve member 8 rests with a first axial end face 12 against a first stop face 13 fixed to the housing.In the other, second switching position, not illustrated, the main valve member 8 has moved away from the first stop surface 13 and in particular rests with a second axial end surface 14 opposite the first axial end surface 12 against a second stop surface 15 which is in turn fixed to the housing.At axially spaced-apart points, a plurality of valve channels passing through the main valve housing 6 open into the working chamber 7, which for better differentiation are designated as main valve channels 16. Between the length sections 17 of the working chamber 7 forming one end section of a main valve channel 16 there are annular sealing surfaces 18 which are stationary with respect to the main valve housing 6 and are oriented radially inward and through which the main valve member 8 extends coaxially. The main valve member 8 has a plurality of length sections of larger diameter which are arranged axially spaced apart from one another and which are designated as closure sections 22, wherein a length section of the main valve member 8 designated as overflow section 23 extends in each case between the closure sections 22 arranged axially spaced apart from one another, the outer diameter of said length section being smaller than that of the closure sections 22.The annular sealing surfaces 18 are expediently formed by annular sealing elements which are fixed in the working space 7 on the peripheral circumferential wall 35 and which consist in particular of a material having rubber-elastic properties.The diameter of the closure sections 22 is matched to the diameter of the annular sealing surfaces 18 in such a way that an annular, radial sealing contact is provided when a closure section 22 extends through the opening surrounded by a radial sealing surface 18. In this case, the length sections 17 of the working chamber 7 adjoining the relevant sealing surface 18 on opposite sides are separated from one another in a fluid-tight manner. If an overflow section 23 assumes an axial position in which it passes through the opening surrounded by a radial sealing surface 18, an annular overflow gap is produced between the two length sections 17 of the working chamber 7 which connect axially on both sides to the said radial sealing surface 18, which permits fluid to pass between the relevant two main valve channels 16.Thus, depending on the switching position of the main valve member 8, a different connection pattern is obtained between the main valve channels 16 opening into the working chamber 7.One of the main valve passages 16, which will be referred to below as main feed passage 16a, is connected, in the operating state of the valve arrangement 1, to an external compressed air source, which will be referred to below as working compressed air source PA. The working compressed air source PA makes available compressed air, referred to as working compressed air, which is under an overpressure, referred to as working pressure.The two main valve channels 16 opening into the working space 7 on opposite sides of the main feed channel 16 apreferably represent a first main working channel 16 band a second main working channel 16 c. These two main working channels 16 b, 16 care provided for connection to a pneumatic consumer, which according to the exemplary embodiment is in particular a pneumatic drive 24, to which they are connected in the operating state of the valve arrangement 1 according to the schematic illustration of FIG. 1.The pneumatic drive 24 has an output part 26 which is movable relative to a drive housing 25 and has a piston 26 aarranged in the interior of the drive housing 25 and which divides two housing spaces from one another, to which in each case one of the two main working ducts 16 b, 16 cis connected.The main valve channels 16 expediently also contain two main venting channels, which are designated as first and second main venting channels 16 d, 16 e, and which each open into the working chamber 7 on the side of one of the main working channels 16 b, 16 cthat is opposite the main feed channel 16 a. Each main vent passage 16d, 16e is connected to the atmosphere R.Thus, the main valve 4 in the embodiment has a 5 / 2 valve function. In the first position of the main valve member 8, the first main working passage 16b is connected only to the main feed passage 16a, while at the same time the second main working passage 16c is connected only to the second main bleeding passage 16e. In the second switching position, the first main working channel 16 bis only connected to the first main venting channel 16 d, while the second main working channel 16 cis only connected to the main feed channel 16 a. In both cases, an operating situation arises on the part of the connected pneumatic drive 24, in which its piston 26 ais acted upon by working compressed air on one side and is relieved of pressure or vented on the other side, so that the output part 26 moves in one direction or the other with respect to the drive housing 25.In an embodiment not shown, the main valve 4 is provided with a 3 / 2 valve function, and the second main working passage 16 cand the second main bleeding passage 16 eare not provided.Two first and second drive surfaces 27, 28 oriented opposite to one another with respect to the axial direction of the longitudinal axis 8 aare formed on the main valve member 8. Each of these driving surfaces 27, 28 is supplied with a fluid force to apply a driving force to the main valve member 8 capable of affecting the switching position of the main valve member 8. The two drive surfaces 27, 28 are expediently formed by the two axial end faces 12, 14 of the main valve member 8The first drive surface 27 a, which is on the right in FIG. 1, is oriented such that its fluid application acts on the main valve member 8 in the direction of the depicted first switching position. On the other hand, the main valve member 8 is urged in the direction of the second switching position by a fluid force acting on the second driving surface 28.The first drive surface 27 delimits an air spring chamber 32 which is formed in the interior of the main valve housing 6, and is preferably formed by one of the two axial end sections of the working chamber 7. The second drive surface 28 delimits a further chamber which is fluidically separated from the air spring chamber 32 and which is referred to as drive chamber 33. This drive chamber 33 is preferably formed by the end section of the drive chamber 7 axially opposite the air spring chamber 32.The two drive surfaces 27, 28 are expediently each formed on a piston-like end section 36 of the main valve member 8, which carries an annular seal 34, which rests with sealing in a slidingly displaceable manner on the peripheral circumferential wall 35 of the working chamber 7 in order to separate the air spring chamber 32 and the drive chamber 33 from the length section of the working chamber 7 lying therebetween in a fluid-tight manner. This longitudinal section of the main valve member 8 comprising the closure sections 22 and the overflow sections 23 can be connected to the two piston-like end sections 36 in a manner that transmits only compressive forces or can also be firmly connected.From a fluidic point of view, the air spring chamber 32 is exclusively connected to the main feed channel 16 aof the main valve 4. Thereby, working compressed air is branched off from the main feed channel 16 aand fed into the air spring chamber 32, where it forms an air spring LF. The compressed air in the air spring chamber 32 is therefore referred to as air spring compressed air. Preferably, the air spring compressed air is branched off from the end section of the main feed channel 16 aforming a length section 17 of the working chamber 7.The air spring compressed air in the air spring chamber 32, i.e., the air spring LF, exerts a constant driving force on the main valve member 8 acting in the direction of the first shift position. This driving force is also referred to below as air spring force.The air spring chamber 32 preferably receives the air spring compressed air via a branch duct 37 formed in the main valve 4 and there in particular in the main valve housing 6, which branch duct leads firstly into the air spring chamber 32 and secondly into the longitudinal section 17 of the working chamber 7 assigned to the main feed duct 16 a. Thus, the air spring compressed air for forming the air spring LF is directly branched from the main feed passage 16 aof the main valve 4.In order to produce a changeover movement 11, the drive chamber 33 can be acted upon with compressed air under the control of the pilot valve 5, which for better differentiation is referred to as pilot compressed air. The pilot compressed air originates from an external pilot compressed air source PV, to which a pilot duct 38 of the multiway valve 2 is connected.The multiway valve 2 is in particular designed such that the pilot compressed air can be fed into the multiway valve 2 separately from the working compressed air. Thus, the multiway valve 2 receives the pilot compressed air from the outside and not from the inside through a branch from the main feed duct 16a.The multiway valve 2 has an outer surface 42 to which the pilot channel 38 opens out with a channel orifice 43. Independently thereof, the main feed channel 16 aof the main valve 4 likewise opens out to the outer surface 42 of the multiway valve 2 via a dedicated channel opening 44, which is spaced apart from the channel opening 43 of the pilot channel 38. The channel opening 43 of the pilot channel 38 is designed for connection to the pilot compressed air source PV. Independently thereof, the channel opening 44 of the main feed channel 16a is designed for connection to the working compressed air source PA.In the exemplary embodiment, the working compressed air source PA and the pilot compressed air source PV are illustrated as compressed air sources which are separate from one another. However, it is understood that both compressed air sources can also be formed externally of the valve arrangement 1 by a common compressed air source which branches off for connection to, on the one hand, the main feed channel 16 aand, on the other hand, the pilot channel 38.The two channel openings 43, 44 are formed jointly on a surface section of the outer surface 42 used as a mounting surface 45. With this mounting surface 45 in front, the multiway valve 2 can be mounted or mounted on a mounting surface 46 of the optional valve carrier 3 already discussed above. As a result, the two channel openings 43, 44 are located in a position opposite the placement surface 46, which also applies to the channel openings 47 of the further main valve channels 16 formed on the mounting surface 45.The valve carrier 3 is traversed by valve carrier channels 48 which each open on the one hand on the placement surface 46 in such a way that they are aligned in the correct assignment with the channel openings 43, 44, 47 of the multiway valve 2 present on the mounting surface 45. Thus, the main valve passages 16 and the pilot passage 38 in the valve carrier 3 continue in corresponding valve carrier passages 48. Expediently, the working compressed air source PA and the pilot compressed air source PV are each connected to a respective dedicated one of the valve carrier channels 48, which correspondingly also applies to the pneumatic drive 24. A sealing device 50 is expediently placed between the mounting surface 45 and the placement surface 46.If the valve arrangement 1 does not contain a valve carrier 3, the named connection measures take place directly at the channel openings 43, 44, 47 of the multiway valve 2.The pilot control channel 38 extends, for example, between the channel orifice 43 located on the outer surface 42 of the multiway valve 2 and the drive chamber 33. As is indicated by the switching symbol 5 aof the pilot control valve 5, the pilot control valve 5 is switched into the course of the pilot control channel 38 and divides the pilot control channel 38 into a pilot feed section 38 a, which leads to the channel orifice 43 and is consequently connected to the pilot compressed air source PV, and a pilot drive section 38 b, which opens into the drive chamber 33.The pilot passage 38 is connected or connectable to the pilot compressed air source PV independently of the main feed passage 16 aof the main valve 4. The air spring compressed air is branched off from the main feed passage 16a without a connection to the pilot passage 38. The latter takes place within the main valve 4 and there in particular from the longitudinal section 17 of the working chamber 7 belonging to the main feed channel 16 a.The branch passage 37 does not have any connection to the pilot passage 38 in the multiway valve 2.Pilot valve 5 preferably has a 3 / 2 valve function and, in addition to pilot channel 38, communicates with a pilot venting channel 49 leading to atmosphere R.The pilot valve 5 can be selectively switched to one of two operating positions. In the first operating position shown in the drawing, it has interrupted the pilot channel 38, wherein the pilot feed section 38 ais closed and at the same time the pilot drive section 38 bis connected to the pilot venting channel 49. In this first operating position of the pilot control valve 5, the drive chamber 33 is thus vented. Accordingly, the main valve member 8 assumes the illustrated first switching position due to the air spring force of the air spring LF which is constantly acting on it.By appropriate actuation, pilot valve 5 can be switched to a second switching position in which it releases the air passage through pilot channel 38, in that it fluidically connects pilot feed section 38 ato pilot drive section 38 b, for example. The pilot vent channel 49 is separated from the pilot channel 38.In the second operating position, pilot compressed air flows through the pilot channel 38 into the drive chamber 33 and acts there on the second drive surface 28 formed on the main valve member 8, the drive force exerted on the main valve member 8, which is referred to below as pilot drive force for better differentiation, being greater than the air spring force and having the result that the main valve member 8 is switched from the first switching position into the second switching position. In this second switching position, the main valve member 8 remains as long as it is acted upon by the pilot driving force.The main valve 4 has a monostable characteristic. If the pilot drive force is removed, which is effected by switching the pilot valve 5 into the first operating position, the main valve member 8 is pushed back into the first switching position again by the air spring force still present.In the exemplary embodiment, the working pressure and the pilot pressure are of equal magnitude. This simplifies the pressure supply measures. In order that the main valve member 8 can nevertheless be readily switched into the second switching position if required and can be fixed there, the second drive surface 28 of the main valve member 8, which can be acted upon by the pilot compressed air, is selected to be larger than the first drive surface 27 acted upon by the air spring LF. In this way, a pilot drive force which is larger with respect to the air spring force can be produced very easily. Of course, the two drive surfaces 27, 28 can also be selected to be of equal size if a pilot pressure is provided which is greater than the working pressure.A safety aspect is associated with the design of the multiway valve 2 in that, in the event of the pilot compressed air fed into the pilot duct 38 being omitted, the main valve member 8 is switched over into the first switching position by the air spring LF which is independently effective therefrom, provided it is not already located there. Such a omission of the pilot compressed air can occur due to a disturbance in the compressed air supply or can be deliberately brought about when a cut-off valve 53 is switched on between the pilot channel 38 and the pilot compressed air supply, which applies to the exemplary embodiment. The cut-off valve 53 makes it possible to cut off the pilot passage 38 without pressure in order to prevent the main valve 4 from being actuated even in the event of the pilot valve 5 being actuated. This can be the case during maintenance work or changeover work.The interrupt valve 53 can expediently assume two switching positions, namely a through position and an interrupt position. In the passage position, the fluid connection between the pilot compressed air source PV and the pilot channel 38 is released, and in the interruption position is disconnected. Preferably, in the cut-off position, the pilot channel 38 is vented by the cut-off valve 53, so that no residual pressure remains in the pilot channel 38, which could still cause an undesired switching function of the main valve 4 in the event of an actuation of the pilot valve 5.If the pilot compressed air source PV is again connected to the pilot channel 38, the standard operation of the multiway valve 2 can be continued, wherein it is ensured that the main valve 4 is in the first switching position and not in another position which could result in uncontrolled movement of the output part 26 of a connected pneumatic drive 24.The pilot valve 5 is expediently of an electrically actuatable type and contains an electrically activatable actuating unit 54 in order to be able to preset the operating position of the pilot valve 5 as required. The actuating unit 54 can expediently be connected in a manner not illustrated in more detail to an electronic control device which can deliver the electrical actuating signals. The pilot control valve 5 is expediently additionally equipped with a manual auxiliary actuating device 55, which enables a purely manual switching over of the pilot control valve 5 independently of the electrically activatable actuating unit 54. The operation unit 54 is, for example, an electromagnet unit or a piezoelectric unit.The electrical connection of the pilot control valve 5 to an electronic control device can expediently be effected, in the case of a valve arrangement 1 equipped with a valve carrier 3, via the valve carrier 3, which then has a signal transmission device 56, which is only schematically indicated and can be coupled electromechanically to the pilot control valve 5.

Claims

Valve arrangement, having at least one multiway valve (2) which has a main valve (4) and a pilot valve (5) serving for actuating the main valve (4), wherein the main valve (4) has a main valve member (8) which can be positioned selectively in a first switching position or in a second switching position and can control the fluid connection between a plurality of main valve ducts (16), under which there is a main feed duct (16a) which is fed with working compressed air from a working compressed air source (PA) during operation of the valve arrangement (1), wherein the main valve member (8) is constantly acted upon in the direction of the first switching position by an air spring (LF) formed by compressed air spring, and can be acted upon with pilot compressed air for switching into the second switching position, which can be provided by a pilot channel (38) which can be controlled by means of the pilot valve (5) and is connected to a pilot compressed air source (PV) independently of the main feed channel (16a) during operation of the valve arrangement (1), wherein the main feed channel (16a) and the pilot channel (38) are formed separately from one another within the multiway valve (2) without any influencing mutual fluid connection, and wherein the multiway valve (2) has an outer surface (42) at which the main feed channel (16a) and the pilot channel (38) open out independently of one another with mutually spaced channel openings (44, 43), wherein the channel orifice (44) of the main feed channel (16a) is provided for connection to the working compressed air source (PA) and the channel orifice (43) of the pilot channel (38) is provided for connection to the pilot compressed air source (PV), characterized in that the compressed air spring air serving to form the air spring (LF) is branched off from the main feed channel (16a) of the main valve (4) without a connection to the pilot channel (38) within the main valve (4), wherein the channel orifices (44, 43), formed separately from one another, of the main feed channel (16a) and of the pilot channel (38) are formed on a surface section, formed as a mounting surface (45), of the outer surface (42) of the multiway valve (2), wherein the valve arrangement (1) has a valve carrier (3) which is separate with respect to the multiway valve (2), which is provided with a mounting surface (46), to which the multiway valve (2) is or can be attached by its mounting surface (45) and through which valve carrier channels (48) pass, which communicate with the main valve channels (16), which open out on the mounting surface (45), and the pilot channel (38), which likewise opens out on the mounting surface (45), of the multiway valve (2) mounted on the mounting surface (46).Valve arrangement according to Claim 1, characterized in that the main valve member (8) has two first and second drive surfaces (27, 28) oriented opposite one another, wherein the first drive surface (27) delimits an air spring chamber (32) which has no connection to the pilot duct (38) and is constantly connected to the main feed duct (16a), and wherein the second drive surface (28) delimits a drive chamber (33) which is connected to the pilot duct (38).Valve arrangement according to Claim 2, characterized in that the main valve member (8) is accommodated in an axially displaceable manner in a working chamber (7) of the main valve (4), the two mutually opposite end portions of which form the air spring chamber (32) and the drive chamber (33).Valve arrangement according to Claim 2 or 3, characterized in that the air spring chamber (32) is connected to the main feed duct (16a) via a branch duct (37) which has no connection to the pilot duct (38).Valve arrangement according to one of Claims 2 to 4, characterized in that the pilot duct (38) is divided by the pilot valve (5) into a pilot feed section (38a) which is or can be connected to the pilot compressed air source (PV) and a pilot drive section (38b) which is or can be connected to the drive chamber (33).Valve arrangement according to claim 5, characterised in that the pilot valve (5) has a 3 / 2 valve function and is capable of connecting the pilot drive section (38b) either to the pilot feed section (38a) or to a pilot venting duct (49) connected to the atmosphere (R).Valve arrangement according to one of Claims 2 to 6, characterized in that the first drive surface (27) delimiting the air spring chamber (32) is smaller than the second drive surface (28).Valve arrangement according to one of Claims 1 to 7, characterized in that the fluid pressures of the working compressed air provided by the working compressed air source (PA) and of the pilot compressed air provided by the pilot compressed air source (PV) are of the same magnitude.Valve arrangement according to one of Claims 1 to 8, characterized in that, in addition to the main feed channel (16a), the main valve (4) contains, as further main valve channels (16), at least one main working channel (16b, 16c) provided for connection to a consumer and at least one main venting channel (16d, 16e) connected to the atmosphere (R), wherein each main working channel (16b, 16c) is connected to the main feed channel (16a) in one switching position of the main valve member (8) and to a main venting channel (16d, 16e) in the other switching position.Valve arrangement according to one of Claims 1 to 9, characterized in that it has a shut-off valve (53) which is connected between the pilot duct (38) and the pilot compressed air source (PV) and by means of which the pilot duct (38) can be disconnected from the pilot compressed air source (PV).Valve arrangement according to Claim 10, characterized in that the pilot control duct (38) can be vented to the atmosphere (R) through the interrupter valve (53)Valve arrangement according to one of Claims 1 to 11, characterized in that the main valve (4) is a slide valve, the main valve member (8) of which is designed as a piston slide.

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