Valve arrangement and drive system equipped with it

Abstract

A valve arrangement (2) and a drive system (1) equipped therewith are proposed, wherein at least one valve unit (27) is used for the fluidic control of a fluid-operated drive (3). Each valve unit (27) contains, in fluidic parallel connection, a throttle device (77) responsible for end-position damping, a check valve (78) assigned to a bypass channel (81), and a main valve (37) designed as a throttle valve (37a) and usable for speed regulation. The main valve (37) has a main valve member (38) that can be switched between a throttling open position and a closed position by means of an electrically actuated switching device (56). The open position can be varied for speed regulation by means of an adjusting device (57). The valve unit (27) can be mounted directly on a fluid-operated drive (3).

Description

The invention relates to a valve arrangement having at least one valve unit having a valve housing for the fluidic activation of a fluid-actuated drive, which valve unit contains an output element that can be driven to perform a stroke movement, wherein the valve unit has the following:a control connection opening for the selective supply or discharge of a pressure fluid,a working connection opening provided for connection to a fluid-actuated drive to be controlled,a throttle device provided for damping the end position of the output member of the fluid-operated drive, which throttle device has a throttle channel connecting the two connection openings and a throttle point arranged in the throttle channel,a main valve which has a main channel connecting the two connection openings parallel to the throttle channel and a main valve member assigned to the main channel, wherein the main valve member can be positioned alternately in one of two switching positions, which are an open position releasing a main flow cross section of the main channel as the first switching position and a closed position closing the main channel as the second switching position, by means of an electrically actuatable switching device of the valve unit while performing a switching movement, anda check valve connected between the two connection openings and permitting a fluid flow in the direction of the working connection opening and preventing it in the opposite direction.The invention further relates to a drive system having a fluid-actuated drive having a drive housing and a driven member drivable for a stroke movement relative to the drive housing, and having a valve arrangement having at least one valve unit for fluidically controlling the fluid-actuated drive.From DE 35 06 180 A1 a drive system is known in which a regulating valve is connected to a fluid-actuated drive formed by a working cylinder, under the cooperation of which a driven member of the fluid-actuated drive can be driven to a stroke movement by controlled fluidic pressurization and which permits end position damping of the driven member when approaching an end stroke position. Two flow channels are formed in the regulating valve, which flow channels are firstly a throttle channel belonging to a throttle device and secondly a further channel, which can be designated as a main channel and is a constituent part of a shut-off valve device, which can be designated as a main valve. The shut-off valve device has a main valve member which normally assumes an open position releasing a main flow cross section of the main channel, from which a maximum stroke speed of the output member of the fluid-actuated drive results. By means of a position sensor referred to as a signal transmitter, a switching over of the main valve member into a closed position can be brought about as a function of a predetermined stroke position of the output member, so that a further pressurization of the output member is only possible through the throttle device, which leads to a deceleration and accordingly an end position damping of the output member. A non-return valve inserted into the course of the throttle channel permits a fluid flow only in the direction of the drive and prevents disruptive return flows.DE 198 37 960 A1 describes a valve unit in which an unlockable check valve is connected between an inlet channel and an outlet channel, wherein a further check valve and a throttle device connected in parallel in this respect are provided in a series connection with the unlockable check valve. The pilot-operated check valve permits venting of the outlet duct by supplying a control pressure, wherein a manual venting device is additionally provided which, if required, also permits manual venting of the outlet duct. The valve unit can be mounted directly on a pneumatically operated working cylinder.From DE 1 927 506 U a single-acting working cylinder for pneumatic pressure media is known, which is equipped with a multiway valve and a speed regulating valve. Both valves are mounted in a mutually coaxial alignment lying behind one another on an end face of the working cylinder, so that they form a unit with the working cylinder.WO 2016 / 023569 A1 discloses an actuator control for controlling a fluidically operable actuator, which has a feed valve in a feed line for the inflow of a working fluid and a discharge valve in a discharge line for an outflow of the working fluid. Both valves can be controlled by a control device, wherein the control is effected taking into account a flow signal provided by a flow sensor coupled to the control device.The object of the invention is to provide a valve arrangement and a drive system equipped therewith in a configuration which, with a cost-effective construction and also in conjunction with a fluid-actuated drive of simple design, enables effective speed control of the movable output member of the fluid-actuated drive.To achieve this object, a valve arrangement of the type mentioned at the beginning is provided according to the invention,the check valve of the valve unit is assigned to a bypass channel connecting the two connection openings and present in addition to the throttle channel and the main channel,and that the main valve of the valve unit is designed as a throttle valve provided for setting a stroke speed of the output member of the fluid-operated drive, by means of which a throttled fluid flow can be produced in the main channel in the first switching position of the main valve member forming an open position, and which has an adjusting device by means of which different open positions can be preset as the first switching position for the main valve member, which differ from one another in the cross-sectional dimensions of the main flow cross section and thus in the producible throttling intensity.The object is furthermore achieved with a drive system of the type mentioned at the beginning, the valve arrangement of which is designed in the aforementioned sense.The valve arrangement, which can be used or is designed in particular as a component of a drive system in conjunction with a fluid-actuated drive, offers the advantageous possibility of effectively, precisely and variably actuating the movable output member of a fluid-actuated drive having no internal speed control structures with respect to a desired speed profile. The valve arrangement contains at least one valve unit with a working connection opening provided for fluidic connection to a drive chamber of the fluid-actuated drive and a control connection opening usable for the selective supply or discharge of a pressure fluid for the purpose of ventilating or venting the connected drive chamber. A control valve device suitable for presetting the direction of movement of the stroke movement of the driven member can be connected in particular to the control connection opening, which can cause ventilation or venting by supplying or discharging a pressure fluid formed in particular by compressed air. When the control port is vented, a fluid flow from the working port to the control port can form in the valve unit, the flow rate of which flow depends on the instantaneous switching position of the main valve member of the main valve, which can be positioned alternately selectively in an open position, which allows a fluid passage through the main channel, as the first switching position or in a closed position, which closes the main channel for preventing a fluid passage, as the second switching position. If, during a stroke movement of the output member of the fluid-operated drive, the pressure fluid displaced from a drive chamber of the drive, which decreases in volume, is introduced into the valve unit via the working connection opening, the second switching position of the main valve member, which is designed as a closed position, is responsible for a damping phase of the stroke movement of the output member, which damping phase brings about end position damping, since the pressure fluid displaced from the drive chamber can flow out to the vented control connection opening at a greatly reduced flow rate only through the throttle device, which is connected in parallel with the main valve, because of the likewise blocking nonreturn valve. The first switching position of the main valve member, designed as an open position, is responsible for a normal phase of the stroke movement of the driven member, which phase is upstream of the damping phase and in which the stroke speed of the driven member is higher than in the subsequent damping phase, since a considerably larger flow cross section is available to the displaced pressure medium for the transfer to the control connection opening as a result of the opened main flow cross section of the main channel. A special feature of the main valve is its configuration as a throttle valve, which in the open position or first switching position of the valve member can open up a main flow cross section of the main channel, which although in favor of a higher stroke speed of the output member is larger in absolute value than the flow cross section of the throttle device responsible for the end position damping, nevertheless effects a throttling of the fluid flow in order to provide a predetermined stroke speed of the output member for the normal phase of the stroke movement of the output member for speed regulation. An adjusting device of the main valve or throttle valve offers the advantageous possibility of presetting a plurality of alternative open positions for the first switching position of the main valve member, which differ from one another in the cross-sectional dimensions of the respectively released main flow cross section and bring about different throttling intensities, so that there is the possibility for a variable speed regulation in the normal phase of the stroke movement. By means of an electrically actuatable changeover device, the valve member can in principle be changed over at any time between the open position currently predetermined by the setting device and the closed position in order to change from a normal phase to a damping phase of the stroke movement for the end position damping. The throttle valve is thus a two-position valve which has the special feature that different open positions can be preset by means of the setting device for the first switching position of the main valve member, so that a comfortable speed regulation for the normal phase of the stroke movement is possible. The setting device consequently permits a setting of the stroke speed outside the damping phase, which setting is individually adapted to the intended use of the associated drive. The electrical controllability of the changeover device offers the simple possibility of implementing a position-dependent initiation of the damping phase with respect to the output member by detecting a corresponding stroke position, which can be designated as damping position, of the output member of the fluid-actuated drive during its stroke movement. In this case, the entire effective surface of the output member delimiting the associated drive chamber can be used for the damping process, resulting in an extremely effective end position damping. If a reversal of the movement of the driven member is to be brought about, this can be brought about by ventilating the control connection opening, the instantaneous switching position of the main valve member being unimportant since the check valve, which opens in this case, allows unhindered fluid transfer through the bypass channel parallel to the main channel and to the throttle channel to the working connection opening and the drive chamber of the fluid-actuated drive connected thereto.The output member can thus execute an unthrottled stroke movement on the part of the valve unit connected to the ventilated drive chamber.The valve unit thus permits, on the one hand, an at least substantially unthrottled fluid flow from the control connection opening to the working connection opening through the then open bypass duct and the throttle duct when a higher fluid pressure is present at the control connection opening than in the working connection opening, and, on the other hand, a throttled fluid flow from the working connection opening to the control connection opening when the fluid pressure present at the working connection opening is higher than at the control connection opening, wherein two-phase throttling is possible here, in particular--in each case when the bypass duct is closed by the check valve--in a first throttling phase in the open position of the main valve member through the main duct and the throttle duct acting parallel thereto and in a second throttling phase in the closed position of the main valve member through the throttle duct of the throttle device which is then acting exclusively.In the case of a double-acting fluid-actuated drive, both drive chambers of the drive can be connected to their own valve unit, so that a normal phase regulated with respect to the stroke speed and a damping phase of a stroke movement greatly slowed down in this respect can take place in both movement directions.The drive system according to the invention contains a fluid-actuated drive with a drive housing and an output member which is movable in particular linearly in this respect, wherein the output member can be driven to a stroke movement relative to the drive housing by a controlled pressurization by means of a suitable pressure fluid. Any fluid pressure medium can be used as the pressure fluid, compressed air being preferred, so that the fluid-actuated drive is a pneumatic drive. The fluid-operated drive is combined with the valve arrangement designed according to the invention, which offers the advantage of dividing the stroke movement of the output member in at least one and expediently in both movement directions into a normal phase with a regulated and in particular constant higher stroke speed and into a damping phase with a decreasing stroke speed. The fluid-operated drive itself expediently does not have any internal structures designed for speed control; it requires in particular neither a throttle device nor a separate buffer element on the output member provided for fluidic end position damping. Accordingly, the drive system can be realized very inexpensively using an inexpensive fluid-operated drive.Advantageous further developments of the invention are evident from the dependent claims.The valve arrangement can have only one valve unit or two valve units depending on the direction of movement of the output member of a fluid-operated drive. A kit with two valve units is provided in particular when the associated fluid-actuated drive is a double-acting drive, the output member of which divides two drive chambers from one another in a drive housing, which drive chambers can be supplied with fluid in a controlled manner in each case.The working connection opening is expediently located on a connecting piece of the valve housing of the at least one valve unit of the valve arrangement, wherein this connecting piece offers the possibility of fastening the valve unit directly to a drive housing of a fluid-actuated drive to be controlled. A drive system equipped with at least one such valve unit contains a drive assembly with a fluid-actuated drive and at least one valve unit fastened directly to the drive housing by means of its connecting piece. A piston of the output member of the fluid-actuated drive delimits in the drive housing at least one drive chamber which, in order to enable controlled fluid application, communicates with a fluid channel which passes through the drive housing and is referred to as a drive channel and which opens out on an outer surface of the drive housing. To form the drive assembly, the drive unit can be connected with its connecting piece to a channel end section of this drive channel. It is expediently screwed with the connecting piece having an external thread into the channel end section having an internal thread.The main valve of the at least one valve unit expediently has a first valve chamber communicating with the control connection opening and a second valve chamber separated in this respect by a separating wall of the valve housing, wherein the main channel passes through the separating wall and opens into both valve chambers. The switchable main valve member of the main valve expediently extends in the first valve chamber.The main channel passing through the partition wall has a first channel opening facing the first valve chamber and a second channel opening facing the second valve chamber.The main valve is preferably designed as an axially sealing seat valve, wherein the first channel orifice is surrounded by a valve seat, which is opposite a closure section of the main valve member. In the closed position of the main valve member, the closure portion sealingly abuts the valve seat, so that the main channel is closed. In the different open positions of the main valve member which can be predetermined by the setting device, the closure section is lifted to different extents from the valve seat and, in the process, defines, together with the valve seat, a main flow cross section with different cross-sectional dimensions which are responsible for different throttling intensities as a function of the setting.It is advantageous if the closure section has a shape tapering in the direction of the second valve chamber, wherein it is preferably shaped conically. Depending on the respectively set open position, the closure section dips into the main channel to different extents through the first channel mouth in the first switching position and in this case delimits, together with the wall of the main channel, an annular gap of different width defining the main flow cross section.In order that the valve member and accordingly also the associated changeover device is not exposed to any appreciable fluidic pressure force which is effective in the opening direction in the closed position, suitable pressure compensation measures are expediently integrated into the valve unit. These pressure compensation measures include an end wall which sealingly closes the first valve chamber on the side opposite the separating wall and which carries out the switching movement and which is preferably arranged on the valve member. The closing wall separates the first valve chamber from a compensation chamber which, like the first valve chamber, varies in volume and communicates with the second valve chamber via a compensation channel, so that the same fluid pressure prevails therein as in the second valve chamber. In this way, the force acting on the valve member in the closing direction is amplified.The main valve is configured in particular such that the switching motion of the main valve member is a linear motion following the axial direction of a valve main axis of the valve unit. Alternatively, it would be possible in principle, for example, to implement the changeover movement as a curved movement or as a linear movement inclined with respect to the valve main axis.For optimum adaptation of the stroke speed to a respective application in the normal phase of the stroke movement, it is advantageous if the setting device enables continuously variable setting of different open positions for the first switching position. Alternatively, however, the adjustment device can also be designed without any problems for a stepped adjustment of the different open positions.A compact design of the valve unit and good accessibility for adjustment measures is facilitated if the adjustment device is arranged in an axial extension of the main valve member. Preferably, the working connection opening, the main valve member and the adjusting device are aligned coaxially with respect to one another, in particular with the main valve member axially between the working connection opening and the adjusting device.For a cost-effective construction, it is advantageous if the adjusting device can be actuated manually for changing the open positions. In this case, it has an actuating member which can be manipulated manually in order to change the open position. In particular, the actuating member can be suitably designed for manual torque introduction.The adjusting device expediently contains a first stop element arranged on the main valve member and a second stop element arranged in a fixed manner with respect to the valve housing. The first stop element takes along the switching movement of the main valve member and the second stop element is placed in the movement path of the first stop element. When switching from the second switching position, designed as a closed position, into the first switching position, the first stop element can run onto the second stop element, whereby an open position is specified. In order to preset different open positions of the first switching position, it is expediently possible to change a relative position of the first stop element assumed with respect to the main valve member. The change of this relative position takes place in a direction of movement of the switchover movement. Additionally or alternatively, for presetting a plurality of different open positions, it may be possible to change a relative position of the second stop element with respect to the valve housing.Preferably, the first and / or second stop element, which can be adjusted to change a relative position, is designed as a threaded element provided with a thread, the change in position of which can be brought about by a rotational movement and a screwing process resulting therefrom with axial adjustment. For example, a position-variable first stop element can be screwed in the manner of a nut with an internal thread onto an external thread arranged in a fixed manner with respect to the valve member. To secure the position of the set relative position, a counter element, which is in particular designed as a counter nut, is expediently screwed onto the aforementioned external thread.Preferably, the main valve member is prestressed by means of a spring device into the first switching position representing an open position. Accordingly, the valve member has an open position as a basic position. The switching device is capable of exerting a switching force on the main valve member which is opposed to the spring force of the spring device and which can overcome this spring force in order to switch the main valve member into the second switching position representing a closed position and retain it there for at least a period of time.The electrically actuatable changeover device is functionally expediently based on an electromagnetic operating principle, wherein it has a coil arrangement which can be electrically energized for its activation, that is to say for generating a changeover force. Alternatively, for example, an electromotive functional principle for the changeover device is possible, for example using an electrically actuatable spindle drive.The valve arrangement can have a separate position sensor for each existing valve unit, which is provided for attachment to the fluid-actuated drive to be controlled and which is capable of producing an electrical changeover signal in its assembled position of use at a specific stroke position, which can be referred to as damping position, of a movable output member of the drive, by means of which changeover signal the main valve member is changed over from the instantaneous open position to the closed position. A drive system of preferred construction contains at least one position sensor which is arranged on the drive housing of the stroke-actuated drive to be controlled, in particular in an adjustable manner, by assuming a position of use. The mounting position of the position sensor on the drive housing defines the starting point for the damping phase of the lifting movement. The adjustment possibility, which is preferably present, allows a change as required in the mounting position of the respective position sensor in the stroke direction of the output member and in this way enables an adjustment of the length of the damping section for the end position damping, taking into account the kinetic energy to be braked.It is considered favorable if the valve arrangement has an electronic control unit for each position sensor and thus also for each valve unit, by means of which electronic control unit the electrical changeover signal for the electrically actuatable changeover device of the relevant valve unit can be generated as a function of the actuation of the associated position sensor. The electronic control unit is in particular capable of inducing the electrical changeover signal immediately after a sensor signal generated by the position sensor and attributable to the detection of the damping position of the output member is received and supplying it to the electrically actuatable changeover device. In a drive system, each electronic control unit is preferably mounted directly on the drive housing of the fluid-actuated drive, wherein it is particularly advantageous if it is combined with the assigned position sensor to form a structural unit. For example, each position sensor may directly comprise an integrated electronic control unit. The at least one electronic control unit can, however, also be designed such that it can be mounted or installed on the fluid-actuated drive independently of a position sensor.An electronic control unit arranged directly on the drive housing, which can be embodied in particular as a discrete circuit with low complexity, avoids extensive cabling with a superordinate external electronic control device and promotes a plug-and-play functionality of the fluid-actuated drive to be controlled.It is also advantageous in such a configuration in particular that for the electrical wiring preferably only three cable cores are required per stroke end position of the output member, namely two cores for the positive actuation voltage and the ground connection and a third core for the transmission of the switchover signal to the switchover device. Preferably, any further analog and / or digital signal transmission and signal processing is dispensed with, so that a speed control that is competitive even with purely mechanical end position attenuations can be provided.In order to ensure that the damping phase or the end position damping is reliably maintained from the detection of the damping position of the output member until the stroke end position is reached, it is advantageous if each electronic control unit is assigned an electrical timing element which is preferably integrated into the electronic control unit and by means of which an electrical changeover signal which can be generated by means of the position sensor is still maintained for a predetermined or predeterminable period of time after its generation. The predetermined or predeterminable time period is in particular dimensioned such that the damping phase continues with certainty until the output member has reached the end-of-stroke position. In this way, a cost-effective position sensor, designed for example as a reed switch or Hall sensor, can be used for detecting the damping position, which outputs a sensor signal briefly only when the damping position of the output element is reached. Alternatively, it is possible to provide a position sensor in the form of a travel measuring device which is capable of continuously outputting a sensor signal, so that an electrical timer would be unnecessary.Since a position sensor usually responds with both directions of movement of the output member and consequently generates an electrical changeover signal again when it is moved out of a stroke end position when it passes the damping position in front, measures can be taken which link the output of the electrical changeover signal to a specific direction of movement of the output member. For example, a higher-order external electronic control device can be present as a component of the valve arrangement and / or of the drive system, which is responsible for the actuation of a control valve device that controls the fluid action on the drive and thus the direction of movement of the output member, and which furthermore ensures that an electrical changeover signal for the changeover device is only output if the output member moves in the direction of the associated adjacent end-of-stroke position upon detection of the damping position. For example, the aforementioned electronic control device is linked to the at least one aforementioned electronic control unit for optimum signal processing.In principle, however, it is unproblematic if the main valve member is temporarily switched over into the closed position when the driven member is moved out of the end stroke position and when it passes the position sensor responsible for detecting the damping position, since the fluid flow within the valve unit during the ventilation process is oriented in the opening direction of the check valve and consequently, even when the main channel is closed, a sufficient fluid supply for generating the lifting movement of the driven member is ensured through the bypass channel.The invention is explained in more detail below with reference to the attached drawings. In these show: FIG. 1 shows components of a preferred embodiment of the drive system according to the invention, which is realized using a preferred embodiment of the valve arrangement according to the invention, in a perspective illustration, FIG. 2 shows the arrangement from FIG. 1 in a plan view according to arrow II from FIG. 1, FIG. 3 shows a longitudinal section of the arrangement from FIGS. 1 and 2 along the stepped section line III-III from FIG. 2, wherein further advantageous components of the drive system and of the associated valve arrangement are evident, FIG. 4 shows an enlarged individual illustration of a valve unit of advantageous construction illustrated in FIG. 3 in a section IV, which is framed by a dot-dash line in a longitudinal section, wherein a main valve member of a main valve of the valve unit is shown in a first switching position representing an open position, and FIG. 5 is a longitudinal section corresponding to FIG. 4 of the valve unit in a second switching position of the main valve member representing a closed position.Referring now to the drawings, there is seen a preferred construction drive system, generally designated by the reference numeral 1, which incorporates a preferred embodiment of a valve assembly 2.For simplification, the drive system 1 has a fluid-actuated drive 3, which is also referred to below only as a drive 3 and which can certainly be a rotary drive, but which is preferably designed as a linear drive in accordance with the illustrated exemplary embodiment.The drive 3 can be operated with a pressurized fluid, which can also be referred to as fluidic pressure medium and which is preferably compressed air, so that it is possible to speak of a pneumatic drive. However, the drive 3 can also be operated with other gaseous or also hydraulic pressure fluids.The drive 3 has a housing designated as a drive housing 4 and an output member 5 which can be moved back and forth relative to the drive housing 4 while performing a lifting movement 6 indicated by a double arrow.The output member 5 has a piston 8 arranged in a housing interior 7 of the drive housing 4, which piston divides the housing interior 7 into two drive chambers 11, 12 with sealing, which for better differentiation are also referred to as first drive chamber 11 and second drive chamber 12. The piston 8 is motion-coupled to a force-application section 13 of the output member 5 located outside the drive housing 4, which is, for example, an end section of a piston rod 14 of the output member 5, which is firmly connected to the piston 8 in the housing interior 7. During the stroke movement 6, the piston 8 slides along an inner circumferential surface of the housing interior 7, against which it rests in a slidable manner, for example, by means of a two-part piston seal 8 aand by means of a piston guide ring, which is not illustrated. Depending on the lifting direction 6 a, 6 b, the piston rod 14 moves out of the drive housing 4 or into the drive housing 4. A machine element, not illustrated in any more detail, can be fixed, for example, to the force-tapping section 13 which has an external thread by way of example, and which is intended to be moved during the operation of a machine device.The drive housing 4 has a first end wall 15 and a second end wall 16, which are spaced apart from one another in an axial direction of a longitudinal axis 17 of the drive 3 that can be designated as the longitudinal direction 17 aand between which a housing tube 18 extends, which together with the two end walls 15, 16 delimits the housing interior 7. The two end walls 15, 16 are expediently designed as housing covers which are separate with respect to the housing tube 18 and are attached to the housing tube 18 by means of tie rods or other fastening means. The piston rod 14 passes through the second end wall 16, which can also be referred to as a bearing cover, wherein it is surrounded by a guiding and sealing device 19, which is only schematically indicated and fixed to the second end wall 16.The two end walls 15, 16 are each penetrated by a fluid channel which, for better differentiation, is designated as first drive channel 21 in the case of the first end wall 15 and as second drive channel 22 in the case of the second end wall 16. Each drive channel 21, 22 opens out with an outer channel opening 23 on an outer outer surface of the associated end wall 15, 16 oriented transversely to the longitudinal axis 17 and communicates on the other hand via an inner channel opening 24 with the housing interior 7, wherein the inner channel opening 24 of the first drive channel 21 opens out into the first drive chamber 11 and the inner channel opening 24 of the second drive channel 22 opens out into the second drive chamber 12.By means of an electrically actuatable control valve device 25, which is preferably formed as a component of the drive system 1, a controlled fluid application of the already mentioned pressure fluid to the two drive chambers 11, 12 can be carried out in order to cause the stroke movement 6 in one or the other stroke direction 6 a, 6 bby a resulting application of a pressure difference to the piston 8. The control valve device 25 allows alternating ventilation and venting of the two drive chambers 11, 12 in opposite directions through the drive channels 21, 22 in order to produce a stroke movement 6, in which the output member 5 moves between a first stroke end position 5 aillustrated in solid lines in FIG. 3 and a second stroke end position 5 b, which is opposite thereto and is indicated only by dashed lines in FIG. 3. In the first stroke end position 5 a, the piston 8 abuts the first end wall 15, wherein the output member 5 is retracted as far as possible into the drive housing 4. In the second stroke end position 5 b, indicated by dashed lines, the piston 8 bears against the second end wall 16, wherein the output member 5 is extended as far as possible from the drive housing 4.The control valve device 25 is designed, by way of example, as a 5 / 2-way valve with two possible switching positions, which is connected to a pressure source P which provides the pressure fluid required for driving the output member 5 and also communicates with the atmosphere R. Depending on the switching position of the control valve device 25, pressure fluid originating from the pressure source P is supplied to one of the drive chambers 11 or 12 for the purpose of venting it, and at the same time the pressure fluid located in the other drive chamber 12, 11 is discharged to the atmosphere for venting. The control valve device 25 can alternatively also be designed as a three-position valve, which simultaneously vents or vents both drive chambers 11, 12 in an additional intermediate position.In order to preset the switching positions of the control valve device 25 and accordingly the lifting direction 6 a, 6 bof the output member 5, the control valve device 25 is expediently connected to a superordinate external electronic control device 26, from which it receives its electrical actuation signals.In order to be able to optimally coordinate the operation of the drive 3 with respect to other processes, the drive 3 is expediently equipped with an end position detection device, which is not illustrated in more detail and is capable of detecting the two end stroke positions 5 a, 5 bof the output member 5 in a contactless manner and of reporting them to the electronic control device 26. The end position detection device can be realized by means of individual position sensors or by means of a position measuring system.The speed of the lifting movement 6, which speed is referred to as the lifting speed, largely depends on the flow rate--also referred to as the flow rate or flow rate--with which the pressurized fluid is fed into or discharged from the drive chambers 11, 12. For optimum speed control, the valve arrangement 2 and accordingly also the drive system 1 are equipped with a functionally electrically controllable valve unit 27 for each stroke direction, by way of example. Of these two valve units 27, a first valve unit 27a is connected to the first drive passage 21 and a second valve unit 27 is connected to the second drive passage 22. In this case, the second valve unit 27 bserves for speed control in the first stroke direction 6 aand the first valve unit 27 a serves for speed control in the second stroke direction 6 b, which is opposite the first stroke direction 6 a. The output member 5 moves in the first stroke direction 6 a, starting from the first stroke end position 5 a, into the second stroke end position 5 band in the second stroke direction 6 b, starting from the second stroke end position 5 b, back into the first stroke end position 5 a.If speed control is desired only in one of the two lifting directions 6 a, 6 bof the output member 5, one of the two valve units 27 can be dispensed with. The same applies if, in contrast to the illustrated exemplary embodiment, the drive 3 is not a double-acting drive 3, but rather a single-acting drive 3, in which the drive force on the output member 5 is produced only in one direction of movement by a fluid force and in the opposite direction for example by a restoring spring.A preferred construction of the valve units 27 is described below, wherein the relevant explanations relate by way of example to both the first valve unit 27 aand the second valve unit 27 b, since the same are of identical construction. References to one valve unit 27 are accordingly to be understood as references to both valve units 27 a, 27 b, provided that no deviating details are given in the individual case.The valve unit 27 has a valve housing 28 at which a control connection opening 31 and a working connection opening 32 open out on the outside. The control connection opening 31 serves for the selective supply and discharge of the pressurized fluid required during operation of the drive 3 and, in the ready-to-use state of the drive system 1 according to FIG. 3, is connected via a control line 33 suitable for the fluid guidance and therefore designated as a fluidic control line 33 to one of two working outputs 34 a, 34 bof the control valve device 25. By way of example, the control connection opening 31 has an internal thread for screwing in a connecting device which enables the detachable connection of a fluidic control line 33.The working connection opening 32 is connected to the associated working channel 21 or 22 in the ready-to-use state of the drive system 1. Each valve unit 27 is preferably a structural unit which can be handled uniformly before it is attached to the drive 3 and in which all associated components are integrated and which, in its preferred position of use, as can be seen from FIGS. 1 to 3, is fastened directly to the drive housing 4 of the drive 3. For this purpose, the valve housing 28 has, by way of example, a connecting piece 35 with which it is inserted through the outer channel opening 23 into an adjoining outer channel end section of the associated first or second drive channel 21, 22. By way of example, the connecting piece 35 has an external thread, with which it is screwed into an internal thread of the aforementioned outer channel end section. A seal which is expediently present for preventing leakage is not illustrated any further. Thus, the drive 3 together with the at least one valve unit 27 attached to it forms a drive assembly that can be handled uniformly.The associated working connection opening 32 opens out on the connection piece 35, in particular on the end face, in such a way that, when the valve unit 27 is mounted in the use position, it communicates with the associated working channel 21, 22 and is fluidically connected to the associated drive chamber 11, 12 via this working channel 21, 22.The valve unit 27 has an imaginary valve main axis 36, which is preferably a longitudinal axis of the valve unit 27 and with respect to which the working connection opening 32 and the preferably present connection piece 35 are aligned in particular coaxially. The control connection opening 31 is expediently oriented orthogonally to the valve main axis 36.A two-position switching valve, referred to as main valve 37, is integrated into the valve unit 27 for better differentiation. It has a valve member referred to as a main valve member 38 which, within the scope of a changeover movement 41 indicated by a double arrow, can be positioned selectively in a first switching position 38 adisplayed in FIG. 4 or in a second switching position 38 bdisplayed in FIG. 5. The switchover movement 41 is, for example, a linear movement in the axial direction of the valve main axis 36.The first switching position 38 ais an open position in which the main valve member 38 releases a flow cross section, referred to as main flow cross section 49, of a main channel 42 of the main valve 37 for a fluid passage for better differentiation. The second switching position 38 bis a closed position in which the main valve member 38 closes the main passage 42 so that fluid passage through the main passage 42 is prevented. Since the main valve 37 is designed such that the pressurized fluid flowing through the main passage 42 in the open position experiences a throttling and thus a reduction in its flow rate, the main valve 37 can alternatively be referred to as a throttle valve 37 a, wherein a switchable throttle valve 37 ais involved on account of the switching possibility relating to the main valve member 38. Regardless of the functionality as throttle valve 37 a, the designation as main valve 37 is generally retained below.The main valve 37 has a first valve chamber 43 formed in the valve housing 28 and is separated from a second valve chamber 44 also formed in the valve housing 28 by a partition wall 45 of the valve housing 28. The first valve chamber 43 is in constant open fluid communication with the control port 31, while the second valve chamber 44 is in constant open fluid communication with the working port 32. The two valve chambers 43, 44 and the partition wall 45 arranged therebetween are arranged consecutively in the axial direction of the valve main axis 36, for example. A control passage 46 is formed in the valve housing 28 for fluid communication between the first valve chamber 43 and the control port 31, and a working passage 47 is formed for communication between the second valve chamber 44 and the working port 32.The partition wall 45 is preferably traversed coaxially by the main channel 42, which opens into the first valve chamber 43 via a first channel opening 42 aand into the second valve chamber 44 via a second channel opening 42 b.The main valve member 38 has a longitudinal shape and extends coaxially with the valve main axis 36 in the first valve chamber 43, and at its end region facing the partition wall 45 it has a closure section 48 aligned coaxially with respect to the main channel 42. In an end region axially opposite the closure section 48, the main valve member 38 has a closure wall 51 formed, for example, in the manner of an annular collar, by means of which the first valve chamber 43 is axially separated from a housing chamber adjoining the latter and designated as compensation chamber 53. The first valve chamber 43 and the compensation chamber 53 are formed by axially successive length sections of a housing interior 54 of the valve housing 28, on the cylindrical inner circumferential surface 52 of which the main valve member 38 rests with the end wall 51 in a slidingly displaceable and sealed manner. For sealing, the end wall 51 carries, by way of example, a sealing ring 55 which abuts the inner circumferential surface 52.The end wall 51 carries along the switching movement 41 directly, so that during the switching movement 41 the aspect ratio between the first valve chamber 43 and the compensation chamber 53 changes continuously in opposite directions.Using an electrically actuatable changeover device 56 assigned to the main valve member 38, the main valve member 38 can be positioned alternately in the first switching position 38 aand in the second switching position 38 b, thereby performing the changeover movement 41.The first switching position 38a shown in FIG. 4 is mechanically preset by an adjusting device 57 belonging to the main valve 37. By way of example, the setting device 57 has a first stop element 58 arranged on the main valve member 38 and contributing to the changeover movement 41 and a second stop element 59 arranged in the movement path of the first stop element 58 in a fixed manner with respect to the valve housing 28. The second stop element 59 is located on the side of the first stop element 58 axially opposite the closure section 48. A spring device 62 acting between the main valve member 38 and the valve housing 28 continuously biases the main valve member 38 into the first switching position 38 a, wherein it presses the first stop element 58 onto the second stop element 59 in order to preset the first switching position 38 a.The spring device 62 is expediently located in the first valve chamber 43, wherein it is exemplarily designed as a helical compression spring, which coaxially encloses a shank portion 50 of the main valve member 38 connecting the closure portion 48 to the end wall 51 and which is supported at one end on the partition wall 45 and at the other end on the end wall 51.The adjusting device 57 is expediently arranged in axial extension of the main valve member 38. It contains, by way of example, a shaft body 63 which is preferably formed integrally with the main valve member 38 and passes through a boundary wall 64 of the valve housing 28 which delimits the compensation chamber 53 on the side opposite the end wall 51 in a sealed and slidingly displaceable manner, and which carries the first stop element 58 on an outer shaft body section 63 aarranged outside the valve housing 28.By way of example, the outer shaft body portion 63a has an external thread 65 with which it is screwed into the first stop element 58, which has a central threaded hole with an internal thread 61 complementary to the external thread 65.The second stop element 59 is formed by way of example by a connecting web 66 cof a U-shaped retaining bracket 66 connecting two bracket legs 66 a, 66 b, which connecting web is attached with the free ends of the bracket legs 66 a, 66 bto the outside of the boundary wall 64 of the valve housing 28. The first stop element 58 is surrounded by the retaining bracket 66, wherein it bears against the mutually facing inner surfaces of the two bracket legs 66 a, 66 bin a manner which brings about a rotation prevention with respect to the retaining bracket 66, but nevertheless permits a relative movement of the first stop element 58 in the axial direction of the valve main axis 36. By way of example, the first stop element 58 is designed as a perforated rectangular plate which, for the purpose of preventing rotation, bears with two mutually opposite rectangular sides in each case against an inner surface of one of the two bracket limbs 66 a, 66 b.The first channel opening 42 aof the main channel 42 is framed by an annular valve seat 67 which is stationary with respect to the valve housing 28 and is exemplarily formed on the partition wall 45 and to which the closure portion 48 axially lies. During the switchover movement 51, the distance between the closure section 48 and the valve seat 67 changes, wherein this distance has a maximum in the first switching position 38 aand is equal to zero in the second switching position 38 b. This means that in the first switching position 38 a, a flow cross section is open through the annular gap defined between the closure section 48 and the valve seat 67, which flow cross section forms the main flow cross section 49 already discussed above and which permits fluid transfer between the two valve chambers 43, 44. In the second switching position 38 bin accordance with FIG. 5, on the other hand, the main channel 42 is tightly closed by the closure section resting against the valve seat 67.It can thus be seen that the second switching position 38 bof the main valve member 38 is a closed position closing the main channel 42 and the first switching position 38 ais an open position releasing a main flow cross section 49 of the main channel 42 for a fluid passage.A special feature of the adjusting device 55 is that they can alternatively specify different open positions than the first switching position 38 afor the main valve member 38. These different open positions differ from one another in the cross-sectional dimensions of the main flow cross section 49 which is released for a fluid passage and thus in the throttling intensity which can be produced with respect to a fluid flowing through.A change of the open position can be carried out very easily manually, for example, by changing the relative position between the first stop element 58 and the main valve member 38 in the axial direction of the main valve axis 36. In the illustrated exemplary embodiment, this is possible by rotating the shaft body 63 by introducing a torque into an actuating member 68 which is connected to the shaft body 63 in a rotationally fixed manner. The actuating member 68 is attached in a rotationally fixed manner, for example, to an end section of the outer shaft section 63 athat passes through the second stop element 59 in a freely rotatable manner and is shaped in the form of a disk, for example, so that it can be easily gripped and rotated with fingers of a hand.Due to the threaded engagement of the shaft body 63 with the first stop element 58 designed as a threaded element and the support of the first stop element 58 secured against rotation with respect to the valve housing 28 via the retaining bracket 66, a rotational actuation 71 of the actuating member 68, indicated by a double arrow, results in a screwing process between the shaft body 63 and the first stop element 58, from which a relative position, changing in the axial direction of the valve main axis 36, between the first stop element 58 and the shaft body 63 and thus between the first stop element 58 and the main valve member 38 results.Depending on the selected setting of the setting device 57, different open positions and correspondingly different cross-sectional dimensions of the released main flow cross section 49 of the main channel 42 result for the first switching position 38 acaused by the spring device 62.It is particularly advantageous that, due to the threaded engagement between the shaft body 63 and the first stop element 58, continuously variable setting of different open positions and accordingly also of different throttling intensities or flow rates is possible.Preferably, axially adjacent to the first stop element 58, a counter element 72 acting as a counter nut is screwed onto the external thread 65 of the shaft body 63 and can be braced with the first stop element 58 in order to secure its adjusted relative position.With regard to the configuration of the closure section 48, it is advantageous if the latter, according to the illustrated exemplary embodiment, has a shape tapering in the direction of the second valve chamber 44, wherein, by way of example, a conical shape is selected. The smallest diameter of the closure section 48 is smaller and the largest diameter of the closure section 48 is larger than the diameter of the main channel 42 in the region of the valve seat 67. during the changeover movement 41 the depth of insertion of the closure section 48 relative to the main channel 42 changes, wherein the closure section 48 in the closed position rests with its tapering outer circumferential surface against the valve seat 67.The valve seat 67 is formed by way of example by an annular edge in the region of the first channel mouth 42 a, but can also be tapered, for example, corresponding to the lateral surface of the closure section 48 and can be shaped conically, for example.By means of the switching device 56 already mentioned further above, a switching force FU acting counter to the spring force FF of the spring device 62 can be exerted on the main valve member 38 which is greater than the spring force FF of the spring device 62, so that the main valve member 38 is switched from the first switching position 38 acorresponding to an open position into the second switching position 38 brepresenting a closed position.To generate the switching force FU, it is sufficient, for example, to supply an electrical switching signal to the switching device 56. For this purpose, at least one electrical control line 73 is connected to the changeover device 56. A ground connection can be effected, for example, via the valve housing 28. The switching force FU bleibt as long as the electrical switching signal is present at the switching device 56. When the electric changeover signal is omitted, the changeover force FU is no longer present and the main valve member 38 is immediately returned to the set first switching position 38 aby the spring force FF of the spring device 62.In order to keep the switching force FU and accordingly also the energy requirement as low as possible, it is advantageous if the second valve chamber 44 is connected to the compensation chamber 53 via a compensation channel 74 designed as a fluid channel at least in the closed position of the main valve member 38, but preferably continuously. By way of example, a continuous fluid connection results from a formation of the compensation channel 74 in a wall section of the valve housing 28.Due to the compensation channel 74, the same fluid pressure prevails in the compensation chamber 53 as in the second valve chamber 44, resulting in a fluid force acting upon the main valve member 38 in a closing manner by acting on the end wall 51, which assists the switching force FU.Preferably, the mode of operation of the changeover device 56 is based on an electromagnetic functional principle. By way of example, it contains a coil arrangement 75 which surrounds the housing interior 54 and therefore also at least one longitudinal section of the main valve member 38 with a radial spacing and is connected to the electrical control line 73. Furthermore, it contains a permanent magnet 76, which is in particular designed as a ring magnet and is arranged, for example, on the end wall 51 coaxially to the valve main axis 36. The electrical changeover signal causes the coil arrangement 75 to be energized, wherein the interaction of the current flow with the magnetic field of the permanent magnet 76 generates a Lorentz force, which is effective as the changeover force FU.Alternatively, an electromagnetic actuation principle could also be realized using the reluctance principle by generating a reluctance force as the switching force FU.In addition to the main valve 37, the valve unit 27 includes a throttle device 77 functionally connected in parallel with the main valve 37 and a check valve 78 functionally connected in parallel with the main valve 37 and the throttle device 77.The functional parallel connection of the check valve 78 results from the fact that the two valve chambers 43, 44 are fluidically connected to one another independently of the main channel 42 by means of a bypass channel 81 which is additional in this respect and to which the check valve 78 is assigned. The check valve 78 is designed such that it allows a fluid flow through the bypass channel 81 from the first valve chamber 43 into the second valve chamber 44, but prevents a fluid flow with a reverse flow direction. The bypass duct 81 can therefore only be flowed through if a greater fluid pressure prevails in the first valve chamber 43 than in the second valve chamber 44. In the event of an overpressure in favor of the second valve chamber 44, the check valve 78 and therefore the bypass duct 81 remain closed.By way of example, the bypass channel 81 is designed as a fluid channel passing through the partition wall 45 parallel to the main channel 42. For example, it is composed of a plurality of individual channels distributed around the main channel 42 in order to provide a relatively large flow cross section, but can also be realized as a single channel. The check valve 78 contains, by way of example, as a check valve member 78 a, a check lip which is placed in the second valve chamber 44 in front of the partition wall 45 and has a check lip, which is pivotable for opening and closing according to the double arrow 82, as a check valve member 78 a, which in a closed position bears against the partition wall 45 and covers and closes the associated duct orifice of the bypass duct 81 and which in an open position is lifted from this duct orifice, so that the bypass duct 81 is open.It is understood that the bypass channel 81 can also be formed outside the partition wall 45 and can furthermore also open into the control channel 46 for connection to the first valve chamber 43.The throttle device 77 contains a fluid channel which connects the two valve chambers 43, 44 and therefore also the control connection opening 31 and the working connection opening 32 to one another parallel to the main channel 42 and to the bypass channel 81 and is designated as throttle channel 83 for the purpose of better differentiation. The throttle device 77 also has a throttle point 84 assigned to the throttle channel 83 and providing a greatly reduced flow cross section compared to the throttle channel 83. The throttle point 84 results, for example, from a throttle screw 85 screwed into the valve housing 28 and projecting into the throttle channel 83 with narrowing of the channel cross section. By rotating the throttle screw 85, the cross section of the throttle point 84 and thus the throttling intensity of the throttle device 77 can be adapted as desired.The drive system 1 is expediently designed such that the switching of the main valve member 38 from the first switching position 38 arepresenting an open position into the second switching position 38 brepresenting a closed position can be initiated or is initiated as a function of the stroke position of the moving output member 5 of the drive 3. For this purpose, the valve arrangement 2 and accordingly also the drive system 1 contains, for each installed valve unit 27, a position sensor 86 which responds to a predetermined stroke position of the output member 5 assumed relative to the drive housing 4.Both position sensors 86 are mounted on the drive housing 4 outside the housing interior 7 in such a way that they are activated in a contactless manner by an activation element 87 of the output member 5 moving past them during the lifting movement 6 and output an electrical sensor signal.They are preferably magnetic field-sensitive position sensors 86, for example reed switches or Hall sensors, wherein a permanent magnet that carries along the stroke movement 6 is arranged as the activation member 87 on the output member 5, by means of which permanent magnet a respective position sensor 86 can be activated in a contactless manner. The activation member 87 is expediently attached to the piston 8 and is in particular configured as a ring magnet.The stroke position of the output member 5 which can be detected by a respective position sensor 86 is referred to as damping position since it initiates end position damping. This is in each case a position shortly before one of the two end stroke positions 5 a, 5 bis reached. The first position sensor 86 ais provided in order, during a stroke movement in the second stroke direction 6 b, to determine a first damping position 5 cof the output member 5 upstream of the first stroke end position 5 a, indicated by dashed lines in FIG. 3, while the second position sensor 86 bis provided in order, during a stroke movement 6 taking place in the first stroke direction 6 a, to detect a second damping position 5 d, upstream of the second stroke end position 5 b, indicated by dashed lines in FIG. 3.In each stroke direction 6 a, 6 b, the stroke movement 6 can be divided into a normal phase and a damping phase. The normal phase begins with one of the two stroke end positions 5 a, 5 band, when the damping position 5 dor 5 cadjacent to the respective other stroke end position 5 bor 5 ais reached, changes into a damping phase that is slowed down in comparison to the normal phase. During the normal phase, the output member 5 can move at a predetermined stroke speed, which can be designated as normal speed and is determined by the main flow cross section 49 of the open position of the main valve member 38 of that valve unit 27 whose working connection opening 32 communicates with the currently volume-reducing drive chamber 43, 44. As can be seen, by means of the selected open position of the main valve 37 designed as a throttle valve 37 a, the stroke speed can be adjusted during the normal phase, so that the main valve 37 or throttle valve 37 acan also be referred to as a speed regulating valve.The same valve unit 27 specifies the stroke speed in the damping phase following the normal phase, which is now, however, no longer determined by its main valve 37 but by the throttle device 77. Since the flow cross section of the throttle point 84 is considerably smaller than the main flow cross section 49 of the main valve 37, the output member 5 experiences a strong braking during the damping phase, which brings about end position damping of the output member 5.When the output member 5 reaches the relevant damping position 5 c, 5 dduring the stroke movement 6, the position sensor 86 which is then activated generates an electrical sensor signal which can be passed on either directly or after electronic processing as an electrical changeover signal to the valve unit 27 functionally assigned to it, with the result that the main valve member 38 changes over from the first switching position 38 ato the second switching position 38 b, as a result of which the damping phase and therefore end position damping is initiated.Each position sensor 86 present can be positioned expediently variably and in particular continuously in different positions along the stroke path of the output member 5. In this way, the damping position to be detected and the stroke distance of the damping phase can be set in an application-specific manner.By way of example, the valve arrangement 2 contains for each position sensor 86 a separate electronic control unit 88 which is capable of generating the mentioned electrical changeover signal on the basis of the position signal generated by the associated position sensor 86. Each electronic control unit 88 expediently has only small dimensions and can be mounted or mounted directly on the drive housing 4 of the drive 3, as depicted. A design is advantageous in which each position sensor 86 is combined with the electronic control unit 88 assigned to it to form a unit that can be handled in a single way. The electrical control line 73 connects the electronic control unit 88 to the associated changeover device 56.Each electronic control unit 88 or the position sensor 86 assigned to it preferably has, in addition to the electrical control line 73, only two further connections, on the one hand a connection marked with "+" in FIG. 3 for the positive actuation voltage and a ground connection marked with "-". As a result, the electrical connection work for putting the drive system 1 into operation is extremely simple.By means of at least one further electrical control line 91, indicated by dashed lines in FIG. 3, each electronic control unit 88 can be networked to the superordinate electronic control device 26.For reasons which will be explained later, it is advantageous if each electronic control unit 88 is equipped with an electrical timer 92 indicated by dashed lines in FIG. 3. The electrical timer 92 ensures that the electrical changeover signal is retained for a certain period of time after activation by a position sensor 86, even if the relevant position sensor 86 is deactivated again because the activation member 87 has moved away from it during the damping phase. The aforementioned time interval is in particular set or adjustable in such a way that the electrical changeover signal is reliably present based on empirical values until the output member 5 has reached the adjoining end stroke position 5 a, 5 bafter passing a damping position 5 d, 5 d, so that a further lasting end position damping can be dispensed with.An explanation will now be given of a preferred mode of operation of the described drive system 1.The starting point for an operating cycle is assumed to be the first stroke end position 5 aof the output member 5. In the case of both valve units 27, 27 a, 27 b, the main valve member 38 of the main valve 37 is in the first switching position 38 aand therefore in an open position. The output member 5 is held in the first stroke end position 5 a, since in the illustrated first switching position of the control valve device 25, the first drive chamber 11 is vented and the second drive chamber 12 is vented.To start the operating cycle, the control valve device 25 is switched over into its second switching position by control signals of the higher-order electronic control device 26, so that pressurized fluid originating from the pressure source P is fed into the control connection opening 31 of the first valve unit 27 aand at the same time the control connection opening 31 of the second valve unit 27 bis vented. Within the first valve unit 27 a, the fluid pressure at the control port 31 and thus also in the first valve chamber 43 is higher than in the second valve chamber 44 and the working port 32 communicating with the first drive chamber 11, and as a result, the check valve 78 opens and the pressure fluid can flow into the first drive chamber 11 through the bypass passage 81 at a maximum flow rate defined by the cross section of the bypass passage 81. In parallel, in the first valve unit 27 a, a fluid flow from the control connection opening 31 to the first drive chamber 11 is also possible through the opened main valve 37 and through the throttle device 77, which is constantly slightly open.Since the second drive chamber 12 is situated at the atmosphere R via the main valve 37 of the second valve unit 27 b, which valve assumes an open position, and via the control valve device 25, a higher fluid pressure prevails in the first drive chamber 11 than in the second drive chamber 12, so that the output member 5 performs a stroke movement 6 in the first stroke direction 6 a. This is the normal phase described above, in which the stroke speed is determined mainly by the cross-sectional dimensions of the main flow cross section 49 of the main valve 37 of the second valve unit 27 b, which main valve is in the open position. The main valve 37 permits only a restricted fluid flow of the pressurized fluid displaced by the piston 8 from the second drive chamber 12. In parallel, a fluid flow with a low flow rate can also take place through the throttle device 77 of the second valve unit 27 b, which, however, can be neglected. In FIG. 4, at 93, the flow paths of the pressurized fluid flowing out through the second valve unit 27b are illustrated by means of arrow plots.The open position of the main valve member 38 set by means of the setting device 57 of the second valve unit 27 bis a speed-determining value for the normal phase and the cross-sectional dimension of the released main flow cross section 49 thus predetermined.Shortly after leaving the first end stroke position 5 a, the output member 5 passes the first damping position 5 c, which results in an operationally irrelevant temporary switching of the main valve member 38 of the first valve unit 27 ato the closed position. However, this has no relevant effect on the ventilation of the first drive chamber 11 and therefore on the extension behavior of the output member 5, since the full cross section of the bypass duct 81 is still available for the ventilation of the first drive chamber 11.When the stroke movement 6 continues in the first stroke direction 6 a, the output member 5 reaches the second damping position 5 dwhich is detected by the second position sensor 86 b, whereupon the associated electronic control unit 88 switches the main valve member 38 of the second valve unit 27 bto the closed position which can be seen from FIG. 5. This process marks the start of the damping phase that brings about end position damping. During the damping phase, the pressurized fluid displaced from the second drive chamber 12 can flow in the second valve unit 27 bthrough only the throttle point 84, wherein the associated flow path 94 is illustrated in FIG. 5 by an arrow representation. Fluid passage through the main passage 42 is prevented by the main valve member 38 positioned at the closed position, fluid passage through the bypass passage 81 is prevented by the check valve 78 urged at the closed position. By adjusting the throttle screw 85, the flow cross section of the throttle 84 and thus the extent of the deceleration of the output member 5 can be adjusted.The damping phase in the first stroke direction 6 aends upon reaching the second stroke end position 5 bof the output member 5. the previously correspondingly set electrical timing element 92 of the electronic control unit 88 assigned to the second position sensor 86 bsecures that an electrical changeover signal is applied to the changeover device 56 of the second valve unit 27 band consequently the closed position of the main valve element 38 is maintained until the output member 5 has reached the second stroke end position 5 bwith certainty.Expediently, the reaching of the second stroke end position 5 bis detected by the end position detection device mentioned further above, not illustrated, whereupon the electronic control device 26 switches the control valve device 25 back into the first switching position illustrated in FIG. 3 immediately or at a later point in time on the basis of its programming.According to a modified embodiment, it can be provided that the electronic control device 26 uses the end position signal supplied to it by the end position detection device upon reaching the second stroke end position 5 bto supply an end of damping signal to the electronic control unit 88 via the further electrical control line 91, by means of which damping end signal the electrical timing element 92 is deactivated. In this way, empirical values for deactivating the electrical timer 92 can be dispensed with.The switching back of the control valve device 25 into the first switching position brings about a lifting movement 6 of the output member 5 in the second lifting direction 6 b, in which the output member 5 enters the drive housing 4 again by way of example and moves back from the second end-of-stroke position 5 bto the first end-of-stroke position 5 a. In this process, the operating mode of the two valve units 27 a, 27 bis interchanged compared with the preceding first stroke direction 6 a. This means that, in the case of the second valve unit 27 b, during a normal phase which initially begins, the pressurized fluid flows into the second drive chamber 12 through the open nonreturn valve 78 in accordance with the flow path 95 indicated by a dashed arrow illustration in FIG. 4 and displaces the output member 5 in the second stroke direction 6 b, wherein the piston 8 displaces the pressurized fluid contained in the first drive chamber 11 through the open main valve 37 of the first valve unit 27 ain accordance with the flow path 93 to the atmosphere R. The pressure medium fed in can also flow in the second valve unit 27 b, parallel to the bypass duct 81, through the open main valve 37 and through the throttle point 84, which is not illustrated in any more detail, however. The stroke speed during the normal phase of the second stroke direction 6 bis predefined by the open position selected for the main valve member 38 of the first valve unit 27 a.Analogous to the switching of the first valve unit 27 awhen passing the first damping position 5 cduring the extension in the first stroke direction 6 a, the retraction in the second stroke direction 6 bgenerates a temporary switching of the main valve 37 of the second valve unit 27 bto the closed position when the output member 5 passes the second damping position 5 d. For the reasons described above, however, this is also irrelevant here.The electrical control units 88 are preferably able to process electrical lifting direction signals relating to the current lifting direction of the output member 5 obtained from the external electronic control device 26 via the further electrical control lines 91 in such a way that a switching of the main valves 37 into the closed position is prevented if the output member 5 reaches the damping position 5 cor 5 dconnected directly to these lifting end positions 5 a, 5 bafter leaving one of the two lifting end positions 5 a, 5 b. In this case, the sensor signals relating to the reaching of a damping position are virtually masked out.When the output member 5 reaches the first damping position 5 cwhen moving further in the second stroke direction 6 b, the first position sensor 86 acauses the main valve 37 of the first valve unit 27 ato switch over into the closed position according to FIG. 5, so that a damping phase causing end position damping is initiated in turn. This damping phase is also ensured, analogously to the above description, by the electrical timer 92 assigned to the first position sensor 86 auntil the first stroke end position 5 ais reached.In the arrangement described, it is advantageous that the stroke position-dependent activation of the throttle device 77 responsible for the end position damping takes place just as outside the drive 3 as the speed regulation by the main valve 37 designed as a throttle valve 37 a. Accordingly, the drive 3 as such does not contain any specific speed control structures. In this context, it is advantageous that the entire effective cylinder surface is always available for the braking process during the end position damping. It is furthermore advantageous that each valve unit 27 can be fastened to the drive 3 in a manner comparable to a cartridge, which can be effected, for example, by screwing it into the associated drive channel 21, 22.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 35 06 180 A1

[0003] DE 198 37 960 A1

[0004] DE 1 927 506 U

[0005] WO 2016 / 023569 A1

[0006]

Claims

Valve arrangement, having at least one valve unit (27) which has a valve housing (28) for the fluidic activation of a fluid-actuated drive (3) and which contains an output member (5) which can be driven to produce a stroke movement (6), the valve unit (27) having the following: - a control connection opening (31) for the selective supply or discharge of a pressure fluid, - a working connection opening (32) which is provided for connection to a fluid-actuated drive (3) which is to be activated, - a throttle device (77) which is provided for end position damping of the output member (5) of the fluid-actuated drive (3) and has a throttle channel (83) which connects the two connection openings (31, 32) and a throttle point (84) which is arranged in the throttle channel (83), - a main valve (37) which has a throttle point (84) which connects the two connection openings (31, 31, 32), 32) parallel to the throttle channel (83) and having a main valve member (38) assigned to the main channel (42), wherein the main valve member (38) can be positioned alternately in one of two switching positions by means of an electrically actuatable changeover device (56) of the valve unit (27) while performing a changeover movement (41), which are an open position as the first switching position (38a) that releases a main flow cross section (49) of the main channel (42) and a closed position as the second switching position (38b) that closes the main channel (42), and - a check valve (78), which is connected between the two connection openings (31, 32) and permits a fluid flow in the direction of the working connection opening (32) and prevents it in the opposite direction, characterized in that, the check valve (78) of the valve unit (27) is assigned to a bypass channel (81) connecting the two connection openings (31, 32) and present in addition to the throttle channel (83) and the main channel (42), and the main valve (37) of the valve unit (27) is designed as a throttle valve (37a) provided for setting a stroke speed of the output element (5) of the fluid-operated drive (3), by means of which a throttled fluid flow can be generated in the main channel (42) in the first switching position (38a) of the main valve element (38) forming an open position, and which has an adjusting device (57), by means of which different open positions can be predefined as the first switching position (38a) for the main valve element (38), which differ from one another in the cross-sectional dimensions of the main flow cross section (49) and thus in the force intensity which can be produced.Valve arrangement according to Claim 1, characterized in that the working connection opening (32) opens out at a connecting piece (35) of the valve housing (28), via which connection piece the valve unit (27) can be fastened directly to a drive housing (4) of a fluid-actuated drive (3) to be controlled.Valve arrangement according to Claim 1 or 2, characterized in that the main valve (37) has a first valve chamber (43) communicating with the control connection opening (31) and a second valve chamber (44) which is separated in this respect by a dividing wall (45) of the valve housing (28), which dividing wall is traversed by the main duct (42), and communicates with the working connection opening (32), the main valve member (38) of the main valve (37) extending in the first valve chamber (43).Valve arrangement according to Claim 3, characterized in that a first duct orifice (42a) of the main duct (42) facing the first valve chamber (43) is framed by a valve seat (67), opposite which is a closure section (48) of the main valve member (38) of the main valve (37), which closure section, in the closed position of the main valve member (38), sealingly bears against the valve seat (67) and which, in the open positions of the main valve member (38) which can be variably predetermined by the setting device (57), is lifted to different extents from the valve seat (67) and in the process defines, together with the valve seat (67), different cross-sectional dimensions of the main flow cross section (49).Valve arrangement according to Claim 4, characterized in that the closure section (48) has a shape which narrows in the direction of the second valve chamber (44) and is expediently conical, it dipping to different extents into the main duct (42) through the first duct orifice (42a) in the plurality of adjustable different open positions.Valve arrangement according to one of Claims 3 to 5, characterized in that the main valve member (38) has a closing wall (51) which tightly closes the first valve chamber (43) on the side opposite the dividing wall (45) and which carries with it the switching movement (41), by means of which closing wall a compensation chamber (53) is expediently divided off from the first valve chamber (43) and communicates with the second valve chamber (44) via a compensation duct (74).Valve arrangement according to one of Claims 1 to 6, characterized in that the changeover movement (41) of the main valve member (38) is a linear movement which can be carried out in the axial direction of a valve main axis (36) of the valve unit (27).Valve arrangement according to one of Claims 1 to 7, characterized in that the setting device (57) is designed for continuously setting different open positions of the main valve member (38).Valve arrangement according to one of Claims 1 to 8, characterized in that the adjusting device (57) is arranged in an axial extension of the main valve member (38).Valve arrangement according to one of Claims 1 to 9, characterized in that the adjusting device (57) is of a manually actuatable design and has an actuating member (68) which can be manipulated manually for its actuation.Valve arrangement according to one of Claims 1 to 10, characterized in that the setting device (57) has a first stop element (58) which is arranged on the main valve member (38) and which contributes to the changeover movement (41) of the main valve member (38), and a second stop element (59) which is arranged in a fixed manner with respect to the valve housing (28) in the movement path of the first stop element (58), wherein the first stop element (58) bears against the second stop element (59) in each open position of the main valve member (38) and is lifted off from the second stop element (59) in the closed position, and wherein a relative position of the first stop element (58) which is assumed with respect to the main valve member (38) and / or a relative position of the second stop element (59) which is assumed with respect to the valve housing (28) can be variably set in order to preset a plurality of alternative open positions of the main valve member (38).Valve arrangement according to claim 11, characterised in that the first and / or second stop element (58, 59), which can be variably adjusted to change its relative position, is a threaded element provided with a thread, to which a counter element (72) is expediently assigned for securing the position.Valve arrangement according to one of Claims 1 to 12, characterized in that the main valve member (38) is prestressed by means of a spring device (62) into the first switching position (38a) representing an open position and can be switched over by the switching device (56) counter to a spring force (FF) of the spring device (62) into the second switching position (38b) representing a closed position.Valve arrangement according to one of Claims 1 to 13, characterized in that the electrically actuatable changeover device (56) is functionally based on an electromagnetic operating principle and has a coil arrangement (75), which can be energized for activation thereof.Valve arrangement according to one of Claims 1 to 14, characterized in that it is equipped with two valve units (27) for the fluidic activation of a double-acting fluid-actuated drive (3).Valve arrangement according to one of Claims 1 to 15, characterized in that it has, for each valve unit (27) present, a position sensor (86) which is provided for attachment to the fluid-actuated drive (3) to be actuated and which is designed to produce, in a use position attached to the fluid-actuated drive (3), at a specific stroke position of a movable output member (5) of the fluid-actuated drive (3), an electrical changeover signal for the electrically actuatable changeover device (56), said electrical changeover signal producing a changeover of the main valve member (38) from the first switching position (38a), which represents an open position, into the second switching position (38b), which represents a closed position.Valve arrangement according to Claim 16, characterized in that each position sensor (86) is assigned an electronic control unit (88), by means of which the electrical changeover signal for the electrically actuatable changeover device (56) of the assigned valve unit (27) can be generated as a function of the actuation of the position sensor (86), wherein, in the case of the presence of a plurality of valve units (27), a dedicated electronic control unit (88) is expediently assigned to the position sensor (86) of each valve unit (27).Valve arrangement according to Claim 17, characterized in that each existing electronic control unit (88) is assigned an electrical time element (92), by means of which an electrical changeover signal which can be generated by means of a position sensor (86) can be maintained during a predetermined or predeterminable period of time.Drive system, having a fluid-actuated drive (3) which has a drive housing (4) and an output member (5) which can be driven relative to the drive housing (4) in relation to a stroke movement (6), and having a valve arrangement (2) which has at least one valve unit (27) for the fluidic activation of the fluid-actuated drive (3), characterized in that the valve arrangement (2) is designed according to one of Claims 1 to 18.Drive system according to Claim 19, characterized in that a piston (8) of the driven member (5) in the drive housing (4) delimits at least one drive chamber (11, 12) which can be acted upon with a pressurized fluid under controlled conditions in order to produce the stroke movement (6) of the driven member (5) and which communicates with a drive duct (21, 22) formed in the drive housing (4), to which a valve unit (27) of the valve arrangement (2) is connected by its working connection opening (32).Drive system according to claim 20, characterised in that the valve arrangement (2) is formed according to the characterising features of claim 2, wherein the at least one valve unit (27) is mounted directly on the drive housing (4) by means of the connecting piece (35) having the working connection opening (32) on a channel end section of the associated drive channel (21, 22) which opens out on the outside of the drive housing (49) and is expediently screwed into this channel end section.Drive system according to one of Claims 19 to 21, characterized in that the valve arrangement (2) is designed according to the characterizing features of one of Claims 16 to 18, wherein each position sensor (86) is arranged, in particular in an adjustable manner, on the drive housing (3) of the fluid-actuated drive (3) to be actuated, assuming a position of use.Drive system according to one of Claims 19 to 22, characterized in that the valve arrangement (2) is designed according to the characterizing features of Claim 17 or 18, wherein expediently each electronic control unit (88) is mounted directly on the drive housing (4) of the fluid-actuated drive (3).

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