Abstract:
A drive having an emergency closing function comprises a movable coupling device, which has an emergency spring clamped between an input-side and an output-side spring system. The emergency spring is a compression spring moved along with the coupling device. A distance of the spring systems is defined by a locking device in normal operation of the drive, wherein the emergency spring can relax for an emergency function or emergency movement of the drive after the locking device is released or unlocked. The locking device is operated or triggered hydraulically or pneumatically and/or magnetically.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2011/000686, filed on Feb. 15, 2011, which claims the benefit of priority to Serial No. DE 10 2010 011 516.9, filed on Mar. 15, 2010 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure relates to a drive with emergency closing function. 
     For drives with an emergency closing function, various approaches are known. 
     Document DE 101 52 414 A1 and document DE 197 23 624 A1 present hydraulic drives for valve bodies of valves with fixed mechanical coupling between an actuating cylinder and the valve body. The valve body is biased in the closing direction of the respective valve by a respective emergency spring by which the valve is closed in the event of a fault. 
     A disadvantage of such hydraulic drives is that the emergency spring is relaxed or stressed during every adjustment movement of the valve body by the drive. 
     Document DE 103 08 017 B4 presents a hydraulic drive having a mechanical coupling and having an emergency spring, wherein in a normal operating mode, the emergency spring in the stressed state is moved jointly with the coupling. In an emergency operating mode, a knee lever device which holds the emergency spring stressed is released such that the emergency spring relaxes and thus spreads or lengthens the mechanical coupling. The valve is thereby closed. 
     A disadvantage of the latter drives is the outlay in terms of apparatus for the mechanical release function, which must be moved jointly with the emergency spring. 
     By contrast, it is the object of the disclosure to provide a drive which is simple in terms of apparatus and which has an emergency closing function. 
     Said object is achieved by a drive with emergency closing function. 
     SUMMARY 
     The drive according to the disclosure with emergency closing function has a coupling device which is movable—preferably in translatory fashion—and which has an emergency spring braced between a driving-side spring abutment and a driven-side spring abutment. The emergency spring is preferably a compression spring which is moved jointly with the coupling device. A spacing of the spring abutments is fixed in a normal operating mode of the drive by a locking device, wherein, after a release or unlocking of the locking device, the emergency spring is configured to relax for an emergency function or emergency movement of the drive. Here, according to the disclosure, the locking device is actuated or released hydraulically or pneumatically and/or magnetically. The outlay in terms of apparatus for the jointly moved parts of the locking device is thus reduced in relation to the prior art. 
     Further advantageous embodiments of the disclosure are described below. 
     In a preferred refinement, an adjustment drive is provided which enables generation of a translatory driving-side movement which is transmitted via the coupling device into a translatory driven-side movement of a valve body of a valve. After the release or unlocking of the locking device, it is alternatively possible for a translatory driven-side movement of the valve body in a closing direction of the valve to be generated by the emergency spring. 
     A preferred refinement has a positionally fixed cylinder and a driven-side piston accommodated therein, which cylinder and piston together delimit a driven-side annular chamber. Here, the driven-side piston is connected via a driven-side piston rod to the driven-side spring abutment. This permits the use of fixed feed lines to the positionally fixed cylinder and pump movements. 
     A damper which, during the emergency function or emergency movement, acts in the closing direction at the end of the driven-side movement protects against impacts of the driven-side piston and if appropriate of the valve after the release or unlocking of the locking device. 
     In a preferred exemplary embodiment, the damper is a fluidic end position damper. Here, said damper preferably has a damping chamber which is formed on the driven-side annular chamber and which is of reduced diameter in relation to the driven-side annular chamber, whereas the driven-side piston rod has a damping peg with an enlarged diameter in relation to the driven-side piston rod. When the damping peg protrudes into the damping chamber, the final part of the movement is damped. 
     In one refinement of the drive according to the disclosure, the cylinder has a driving-side piston which is connected via a corresponding driving-side piston rod to the driving-side spring abutment. Here, the driving-side piston rod extends through a corresponding driving-side annular chamber. 
     To permit a reversal of the closing direction, the adjustment drive and the driving-side piston are coupled via a connecting rod which extends through the driven-side spring abutment, the driven-side piston rod and the driven-side piston. 
     In one variant of the valve, the latter is a butterfly valve, wherein the valve body is a closing plate. The coupling device is then connected via a pivot drive to a shaft of the closing plate by which the closing plate and thus the valve are adjusted. 
     If the adjustment drive is arranged on a first side of the shaft or of the butterfly valve and the emergency spring is arranged on a second side, which is situated opposite the first side, of the shaft or of the butterfly valve, a space-saving refinement of the drive for the butterfly valve is created. 
     In a preferred refinement of the drive according to the disclosure, the two annular chambers are hydraulically coupled or connected via a coupling line. Here, the two pistons are arranged between the two annular chambers. In this way, the two pistons are held in contact with one another or pressed against one another, and thus the two spring abutments are held with a predetermined spacing to one another, by a common pressure of a pressure medium of the two associated annular chambers. 
     It is preferable for the coupling line or the driven-side annular chamber to be connectable or permanently connected via a low-pressure line to a low-pressure accumulator. During a movement of the pistons away from one another, in particular after the unlocking of the locking device, excess pressure medium flows out toward said low-pressure accumulator. This takes place, for example in the case of the hydraulic locking device, as a result of the undershooting of a predetermined pressure in the two annular chambers. 
     If an orifice is arranged in the low-pressure line and/or in the coupling line directly upstream of the driven-side 3/2 directional seat valve, it is furthermore possible for a speed of the movement in the closing direction of the driven-side piston after an unlocking of the locking device to be adjusted. 
     For the aeration of the chamber formed between the two pistons during the movement thereof away from one another, an aeration duct formed as a bore is preferable, which aeration duct extends through one of the two pistons and the associated piston rod, for example at the driving side. 
     A pressing force, generated by the common pressure of the two pressure chambers, between the two pistons is preferably greater than the sum of a force of the emergency spring and a force required to move the valve body. It is thus possible, in the normal operating mode, for the translatory movement of the adjusting drive to be reliably transmitted to the valve body without the two pistons moving away from one another. 
     In a preferred refinement of the drive according to the disclosure, there is arranged in the coupling line a driven-side 3/2 directional seat valve to which the low-pressure line is connected. The hydraulic securing device is released by said valve. It is thereupon possible, during a movement of the driven-side piston in the closing direction, for the excess pressure medium from the driven-side annular chamber to flow via the coupling line into the low-pressure accumulator. It is preferable if, in a spring-biased normal position of a valve body of the 3/2 directional seat valve, the driven-side annular chamber is connected to the low-pressure accumulator. 
     In a preferred refinement, the damping chamber is connected via a bypass line to a portion of the coupling line which connects the driven-side 3/2 directional seat valve and the driven-side annular chamber. Here, a check valve is arranged in a portion of the coupling line which is parallel to the bypass line, which check valve opens from the driven-side 3/2 directional seat valve toward the driven-side annular chamber. Damping, which is simple in terms of apparatus, for the final part of the emergency movement is thus realized, wherein the pressure medium of the driven-side annular chamber flows via the damping chamber and via the bypass line to the coupling line. Said pressure medium flow path is also utilized for a movement in the closing direction in the normal operating mode. 
     In a preferred variant of the drive, the adjustment drive is hydraulic or pneumatic and has a cylinder, in particular a synchronous cylinder, whose piston rod is moved by a piston of a machine which is operated as a pump. The driving-side spring abutment is fastened to the piston rod. 
     Here, if a pressure medium connection from the machine which can be operated as a pump to the cylinder can be shut off—in particular by means of a 4/2 directional valve—and if the machine is connected via a high-pressure line to the coupling line and via a suction line to the low-pressure accumulator, it is then possible to realize a pump function for increasing the pressing force between the driving-side piston and the driven-side piston. 
     To prevent cavitation, the suction line is connected via two branch lines, in which in each case one check valve is arranged, to the two working connections of the machine. 
     The low-pressure line and the coupling line are connected via a suction line in which there is arranged a check valve which opens from the low-pressure line toward the coupling line. It is thus possible, during a movement of the driving-side piston in the closing direction, for pressure medium to be sucked out of the low-pressure accumulator into the driving-side annular chamber. 
     In a preferred refinement of the drive according to the disclosure, there is arranged in the coupling line a driving-side 3/2 directional seat valve which is configured to connect the driving-side annular chamber via a high-pressure line to a high-pressure accumulator. In said refinement, the driving-side annular chamber is charged directly, and the driven-side annular chamber is charged indirectly via the coupling line, with high pressure. The two pistons are pressed together by said high pressure. 
     If the low-pressure line and the high-pressure line are connected by means of a suction line in which there is arranged a check valve which opens from the low-pressure line toward the high-pressure line, pressure medium can be sucked from the low-pressure accumulator to the high-pressure line. 
     Here, if at least one orifice is arranged in the high-pressure line between the high-pressure accumulator and a connection of the suction line, with a check valve which opens toward the high-pressure accumulator being arranged in a bypass line parallel to said at least one orifice, a pump function by the adjusting drive is possible. Here, pressure medium is pumped from the driving-side annular chamber via the check valve into the high-pressure accumulator, and subsequently pressure medium is sucked from the low-pressure accumulator into the driving-side annular chamber, wherein a return flow of pressure medium from the high-pressure accumulator via the at least one orifice is substantially prevented. 
     To prevent a return movement of the driven-side piston in the direction of the driving-side piston and thus in the opening direction of the valve body during the pump function, a portion of the coupling line arranged between the check valve and the driven-side 3/2 directional seat valve can be designed to be connectable alternately to the low-pressure line or to the high-pressure line via a 3/2 directional seat valve. Here, in a line which connects the portion of the coupling line to the 3/2 directional seat valve, there is arranged an orifice and a check valve which opens toward the 3/2 directional seat valve. 
     A preferred refinement of the drive according to the disclosure has a support or fastening element which is in the form of a hydraulic block and on or in which the one or more pressure accumulators, the valves and the ducts and the cylinders are arranged. 
     In a preferred variant or in a preferred refinement of the drive according to the disclosure, a magnetic locking device is provided as an alternative or in addition to the hydraulic locking device. Said magnetic locking device has an electromagnet which has a coil and an armature, the coil and armature being connected to in each case one of the two spring abutments. Said locking device is electrically actuated, wherein a deactivation or failure of an electrical current initiates an unlocking of the locking device and thus an emergency function or emergency movement. 
     The coil and the armature are arranged in each case annularly and are fastened in each case via a spacer part to the associated spring abutment, wherein the emergency spring is arranged in a protected manner in the interior of the two spacer parts. 
     If the magnetic locking device has a permanent magnet which provides for example 80% of the magnet force, the energy demand of the electromagnet during normal functioning is reduced. 
     The adjustment drive is preferably connected to the driving-side spring abutment. The adjustment drive is electric, for example in the form of an electric motor with spindle drive, hydraulic, for example with a hydraulic cylinder, or pneumatic, for example with a pneumatic cylinder. 
     A damping element is preferably arranged between the two pistons. Vibrations introduced by the valve body are thus prevented from being transmitted via the two pistons to the adjustment drive, in particular spindle drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary embodiments of the disclosure will be described in detail below on the basis of the figures, in which: 
         FIG. 1  shows, in a schematic illustration, a first exemplary embodiment of a drive according to the disclosure having an adjustment drive, having a hydraulic arrangement and having a coupling device with hydraulic locking device; 
         FIG. 2  shows the adjustment drive and the coupling device of the first exemplary embodiment as per  FIG. 1 ; 
         FIG. 3  shows the hydraulic arrangement of the first exemplary embodiment as per  FIG. 1 ; 
         FIG. 4  shows the coupling device and the hydraulic arrangement of the first exemplary embodiment of the drive according to the disclosure in the emergency function; 
         FIG. 5  shows, in a schematic illustration, a coupling device with a hydraulic and magnetic locking device and a hydraulic arrangement of a second exemplary embodiment of the drive according to the disclosure; 
         FIG. 6  shows, in a schematic illustration, a coupling device with a magnetic locking device and a hydraulic arrangement of a third exemplary embodiment of the drive according to the disclosure; 
         FIG. 7  shows, in a schematic illustration, a coupling device with a magnetic locking device and a hydraulic arrangement of a fourth exemplary embodiment of the drive according to the disclosure; and 
         FIGS. 8 a  to 8 d    show, in a schematic illustration, a fifth exemplary embodiment of a drive according to the disclosure with an adjustment drive, a hydraulic arrangement and a coupling device with hydraulic locking device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic illustration of a complete drive according to the disclosure as per a first exemplary embodiment. The drive has an adjustment drive  44  which is in the form of an electric cylinder and by which, in a normal operating mode of the drive, via a coupling device  46 , a valve body  2  of a seat valve (in  FIG. 1 ) is moved to the right in a closing direction or (in  FIG. 1 ) to the left in an opening direction. 
       FIG. 1  shows the seat valve  1 ,  2  in an open position from which its valve body  2  can be pressed in the closing direction against the valve seat  1  of the seat valve. 
     Furthermore, the drive has a hydraulic arrangement  48  by which in particular a switch from a normal operating mode into an emergency operating mode of the drive according to the disclosure is performed. In the normal operating mode, the valve body  2  is moved by the adjustment drive  44 , and in the emergency operating mode, the valve body  2  is moved instead by an emergency spring  6  integrated in the coupling device  46 . 
       FIG. 2  shows the adjustment drive  44  and the coupling device  46  of the first exemplary embodiment as per  FIG. 1 . The adjustment drive  44  has en electric motor  50  which, via a spindle drive  52 , moves a driving-side spring abutment  12  in translatory fashion. 
     The coupling device  46  has a positionally fixed cylinder  14  which, during an adjustment of the valve body  2 , is not jointly moved either in the normal operating mode or in the emergency operating mode. In said cylinder there are accommodated two pistons  8 ,  9  which bear against one another and which have in each case one piston rod  4 ,  10 . At the driving side, the piston rod  10  connects the piston  9  to the spring abutment  12 , whereas at the driven side, the piston rod connects the piston  8  to a spring abutment  3 . The emergency spring  6  is braced between the two spring abutments  3 ,  12 . 
     The pressure in the annular chambers  13 ,  15  presses the pistons  8 ,  9  against one another with a force greater than the sum of a spring preload force of the emergency spring  6  and the greatest operating force exerted on the valve body  2  by the volume flow. It is thereby ensured that the two pistons  8 ,  9  bear against one another at all times and the force of the adjustment drive  44  acts on the valve body  2 . The force of the adjustment drive  44  acts on the driving-side spring abutment  12  and thus moves the spring  6 , the two piston rods  4 ,  10 , the two pistons  8 ,  9  and finally the valve body  2 . In this way, the spacing between the valve body  2  and valve seat  1  in the normal operating mode is set, and the volume flow thus regulated. Here, the volumes of the two annular chambers  13 ,  15  vary. 
     In the drive according to the disclosure, in the normal operating mode, an emergency spring  6  is held braced between spring abutments  3 ,  12  by the pressure in the annular chambers  13 ,  15 . In the emergency operating mode, the driven-side annular chamber  15  is opened. The emergency spring  6  then moves the valve body  2  toward the valve seat  1  and thus closes the seat valve  1 ,  2 . In particular, in the emergency operating mode, the relaxing emergency spring  6 , the driven-side spring abutment  3  and the valve body  2  move, wherein the spring abutment  3  drives the driven-side piston  8  via the driven-side piston rod  4 . The movement of said parts in the closing direction continues until the valve body  2  sets down on the valve seat  1  and thus shuts off the volume flow. 
       FIG. 3  shows the hydraulic arrangement  48  of the first exemplary embodiment as per  FIG. 1 . Said hydraulic arrangement has a coupling line for connecting the two annular chambers  13 ,  15  (cf.  FIG. 2 ), said coupling line being composed of a driving-side portion  54   a , a driven-side portion  54   b  and a central portion  54   c . In the driven-side portion  54   b  there is arranged a check valve  25  which opens in the direction of the driven-side annular chamber  15 , wherein parallel to said check valve there is provided a bypass line  56  which connects a damping chamber  5  of the driven-side annular chamber  15  (cf.  FIG. 2 ) to the driven-side portion  54   b.    
     Between the driving-side portion  54   a  and the central portion  54   c  of the coupling line there is provided a driving-side 3/2 directional seat valve  20 , whereas a corresponding driven-side 3/2 directional seat valve  22  is provided between the driven-side portion  54   b  and the central portion  54   c . The driving-side 3/2 directional seat valve  20  connects the two portions  54   a ,  54   c  of the coupling line when in a spring-biased normal position a, whereas said valve connects the driving-side portion  54   a  to a high-pressure accumulator  16  via a high-pressure line  58   a ,  58   b  when in an energized switching position b. The driven-side 3/2 directional seat valve  22  connects the two portions of the coupling line  54   b ,  54   c  when in a switching position b, whereas said valve connects the driven-side portion  54   b  of the coupling line to a tank or low-pressure accumulator  24  via a low-pressure line  60  when in a spring-biased normal position a. 
     Two orifices  18   a ,  18   b  are arranged in a portion  58   b  of the high-pressure line, wherein parallel to the orifices  18   a ,  18   b  there is arranged a bypass line  62  with a check valve  17  which opens toward the high-pressure accumulator. 
     An orifice  23  is provided in the low-pressure line  60 . 
     The central portion  54   c  of the coupling line is connected via a relief line  40  to the low-pressure line  60 , wherein in the relief line  40  there is provided a pressure-limiting valve  21 . Between the portion  58   b  of the high-pressure line and the low-pressure line  60  there is provided a relief line  42  in which a pressure-limiting valve  19  is arranged. 
     Between the low-pressure line  60  and the portion  58   a  of the high-pressure line there is provided a suction line  38  in which there is arranged a check valve  64  which opens from the low-pressure line  60  toward the high-pressure line  58   a.    
     The driven-side portion  54   b  of the coupling line is connected via a line  36   a  to a 3/2 directional seat valve  32  which connects the line  36   a  via a line  36   b  to the bypass line  62  when in a spring-biased normal position b, while connecting the line  36   a  via a line  36   c  to the low-pressure line  60  when in a switching position a. 
     An increase in the hydraulic preload will be explained below with reference to  FIG. 3 : if the pressure in the annular chambers  13 ,  15  falls, as a result of leakage or temperature influence, to such an extent that a risk is posed to the above-described pressing-together of the pistons  8 ,  9 , the pressure in the annular chambers  13 ,  15  must be increased. For this purpose, the 3/2 directional seat valve  20  is switched into its switching position b. As a result, the annular chamber  13  is charged with the pressure of the high-pressure accumulator  16  and raised to the pressure level of the latter. If the 3/2 directional seat valve  20  is switched back into the normal position a and the two annular chambers  13 ,  15  are connected, then an average pressure of the pressures thereof is generated in the two annular chambers  13 ,  15 . If said average pressure is insufficient, the 3/2 directional seat valve  20  is switched back and forth until the average pressure is high enough. 
     A pressurization of the high-pressure accumulator  16  will be explained below: if the hydraulic pressure in the high-pressure accumulator  16  falls, as a result of leakage or temperature influence, to a value which no longer permits the above-described increase in the hydraulic preload, the pressure in the high-pressure accumulator  16  must be increased. For this purpose, the 3/2 directional seat valve  20  is switched into the switching position b, and thus the high-pressure accumulator  16  is connected to the driving-side annular chamber  13 . The piston  9  is then moved by the force of the adjustment drive  44  such that the annular chamber is decreased in size. As a result, the piston  9  pumps pressure medium from the annular chamber  13  into the high-pressure accumulator  16 , and thus increases the pressure of the latter. 
     During said movement, air simultaneously flows through the bore or the aeration duct  11  into the space formed between the pistons  8 ,  9 . The pressure falls in the annular chamber  15  because, since the piston  9  is no longer exerting a force on the piston  8 , the pressure in the annular chamber  15  is then a function of the spring preload force of the emergency spring  6  and the operating force exerted on the valve body  2  by the volume flow. The spring force is always greater than the operating force. 
     The piston  9  is subsequently moved quickly back into its initial position (to the right in  FIG. 2 ) by the force of the adjustment drive, and the annular chamber is thus increased in size again. During said process, a large amount of pressure medium flows from the low-pressure accumulator  24  via the suction line  38  into the annular chamber  13 . Pressure medium simultaneously also flows into said annular chamber  13  from the high-pressure accumulator  16 . The latter amount is however small, because the flow thereof is hindered by the two orifices  18   a ,  18   b , such that the pressure level in the high-pressure accumulator  16  scarcely falls. Directly thereafter, the pressure of the high-pressure accumulator  16  propagates in the annular chamber  13 . The pumping process can then be repeated. When the pressure level is high enough, a return to the normal operating mode is effected by switching of the 3/2 directional seat valve  20  into the switching position a. 
     If the pumping movement is to take place during the normal operating mode, the piston  9  is moved away from the piston  8 . As a result, the pressure in the driven-side annular chamber  15  falls to a value determined by the force of the emergency spring  6  and the force of the volume flow. The starting pressure in the annular chambers  13 ,  15  is at least as high as the pressure resulting from the highest volume flow force, plus that resulting from the highest spring force, plus a safety margin. This ensures that the two pistons  8 ,  9  remain pressed against one another even under the action of the highest volume flow force. The lowered pressure in the driven-side annular chamber  15  is associated with an increase in size of the pressure medium volume in the annular chamber  15 , and results in the piston  8  being displaced in the opening direction. The pressure medium in the annular chamber  15  acts as a spring. 
     To prevent said movement in the opening direction, the lines  36   a  to  36   c , the valves  32 ,  33  and the orifice  34  are provided. 
     The 3/2 directional seat valve  32 , when in its switching position b, has no influence on the functions presented in the description because the high-pressure accumulator  16  is separated by the check valve  33 . The pressure is always higher in the high-pressure accumulator  16  than in the rest of the hydraulic system, and the check valve  33  thus remains closed. The low-pressure accumulator  24  is separated by the closing function b of the 3/2 directional seat valve  32 . 
     In order that the above-described displacement of the piston  8  does not take place during the pumping function, the pressure in the annular chamber  15  is decreased to such an extent that its force action F hyd . on the piston  8  cancels out the other forces.
 
 F   spring   +F   volume flow   =F   hyd .
 
     Only then is the pumping process commenced. The position of the piston  8  then does not change. 
     For this purpose, the piston  9  is held in its position by the electric motor  50  and the 3/2 directional seat valve  32  is switched into its switching position a. Since pressure medium flows from the annular chamber  15  via orifice  34 , check valve  33  and 3/2 directional seat valve  32  to the low-pressure accumulator  24 , the pressure in the annular chamber  15  falls. This is continued until the predetermined pressure prevails in the annular chamber  15 . The magnitude of said predetermined pressure is predefined by the known spring force F spring  and the force resulting from the action of the volume flow F volume flow . The force F volume flow  is proportional to the torque at the electric motor  50 , and can be determined therefrom. 
     The 3/2 directional seat valve  32  is then switched back into its switching position b, and the pumping process can begin without the piston  8  moving. 
     During a part stroke test, the emergency functionality of the drive is checked during operation and substantially without impairment to said operation. Here, it is determined whether the emergency spring  6  can move the piston  8  in the closing direction. So as not to impair the operation, said movement should be only small. 
     For this purpose, the above-described pressure reduction by the 3/2 directional seat valve  32  beyond the predetermined pressure is continued, the spring force/volume flow force thus prevails, and the piston  8  is moved slowly, owing to the orifice  34 , in the closing direction. The process is ended by the valve  32  being placed back into its switching position b. The starting position of the piston  8  and the outlet pressure in the annular chambers  13 ,  15  is attained by switching of the 3/2 directional seat valve  20  back and forth. Here, the pressure in the high-pressure accumulator  16  is distributed to the annular chambers  13 ,  15 . 
       FIG. 4  shows the coupling device  46  and the hydraulic arrangement  48  of the first exemplary embodiment of the drive according to the disclosure in the emergency function. Said emergency function is triggered by switching of the driven-side 3/2 directional seat valve  22  into its spring-biased switching position a. The driven-side annular chamber  15  is thus connected to the low-pressure accumulator  24 . Here, the driving-side annular chamber  13  remains shut off. The driven-side piston  8  is driven by the emergency spring  6  and forces pressure medium from the annular chamber  15  via the orifice  23  into the low-pressure accumulator  24 , and moves the valve body  2  in the closing direction. The speed of the piston  8  is limited by the orifice  23 . During said emergency movement, the emergency spring  6  is supported via the driving-side spring abutment  12 , the driving-side piston rod  10  and the driving-side piston  9  on the pressure in the driving-side annular chamber  13  which is shut off. 
     When the damping peg  7  protrudes into the annular chamber  5  provided for it, the outflow of the pressure medium from the annular chamber  15  is throttled. As a result, a pressure is generated in the annular chamber  15  which slows the movement of the piston  8 . This state or moment is shown in  FIG. 4 . 
     A restoration of operational readiness will be explained below: proceeding from a closed position of the seat valve  1 ,  2 , the driving-side 3/2 directional seat valve  20  is switched into the switching position b, and the piston  9  is thereupon pressed against the piston  8  by a fast movement of the adjustment drive  44 . As a result of the fast movement, pressure medium flows from the low-pressure accumulator  24  and from the high-pressure accumulator  16  into the annular chamber  13 . Here, the larger amount comes from the low-pressure accumulator  24 , because the amount flowing in from the high-pressure accumulator  16  is throttled by the two orifices  18   a ,  18   b . Directly thereafter, the pressure of the high-pressure accumulator  16  propagates in the driving-side annular chamber  13 . 
     The driven-side 3/2 directional seat valve  22  is switched into the switching position b, whereas the driving-side 3/2 directional seat valve  20  is switched back and forth between its switching positions until the pressure of the high-pressure accumulator  16  has propagated in both annular chambers  13 ,  15 . The driving-side 3/2 directional seat valve  20  thereafter remains in the switching position a, and operational readiness for the normal function and the emergency function is restored. 
     Since the pressure medium volume is closed and expands to a greater extent than the surrounding metal in the event of a temperature increase, pressure is generated. The magnitude of the pressure is limited by the pressure-limiting valve  21  which, when its set pressure is reached, connects the annular chambers  13 ,  15  to the low-pressure accumulator  24 . 
       FIG. 5  shows a coupling device  146  with a hydraulic and magnetic locking device and a hydraulic arrangement  148  of a second exemplary embodiment of the drive according to the disclosure. In relation to the coupling device  46 , the coupling device  146  is supplemented by two spacer parts  26 ,  28  which are connected by an electromagnet. The electromagnet has a coil  27 . The spacer part  28  is fastened to the spring abutment  12  and the spacer part  26  is fastened to the spring abutment  3 . When the emergency spring  6  is braced by the force of the adjustment drive  44  and the two spacer parts  26 ,  28  are in contact, the coil  27  of the electromagnet is energized. The resulting magnetic force is greater than the spring preload force of the emergency spring  6  and presses the spacer parts  26 ,  28  against one another. The emergency spring  6  remains braced by the magnet force. Both locking devices—magnetic and hydraulic—act in parallel and redundantly. 
     The hydraulic arrangement  148  has a coupling line  154   a ,  54   b  to the driven-side 3/2 directional seat valve  22 , to which the low-pressure accumulator  24  is connected via the low-pressure line  60 . The low-pressure line  60  is connected via a suction line  138  to the driving-side portion  154   a  of the coupling line. In the suction line there is arranged a check valve  164  which opens toward the coupling line  154   a.    
     The emergency function is triggered by the non-energization of the electromagnet  27  and of the 3/2 directional seat valve  22 , as a result of which the former loses its force action and the latter is switched into the switching position a. The subsequent closing movement of the piston is limited in terms of its speed by the orifice  23  and is slowed by the end position damping  5  and  7 . The driving-side piston  9  maintains its position during the emergency movement. In the driving-side annular chamber  13 , pressure builds up in accordance with the spring force of the emergency spring  6 . 
       FIG. 6  shows the coupling device  146  as per  FIG. 5 , with only a magnetic locking device, and a hydraulic arrangement of a third exemplary embodiment of the drive according to the disclosure. Both annular chambers  13 ,  15  are charged with pressure from the low-pressure accumulator  24 . 
     After the triggering of the emergency function by the switching of the coil  27  into the deenergized state, both pistons  8 ,  9  seek to move away from each other. The end position is reached when the piston  9  makes contact with the housing of the positionally fixed cylinder  14 , and the valve body  2  makes contact with the valve seat  1 . 
       FIG. 7  shows a coupling device  346 , with only a magnetic locking device, and a hydraulic arrangement of a fourth simple exemplary embodiment of the drive according to the disclosure. In said exemplary embodiment, the driving-side piston with the driving-side piston rod and the coupling line are dispensed with. 
     By contrast to the second exemplary embodiment as per  FIG. 5 , the hydraulic arrangement  138  shown therein may also be replaced by the hydraulic arrangement  38  of the first exemplary embodiment shown in  FIG. 3 . 
       FIGS. 8 a  to 8 d    show a fifth exemplary embodiment of a drive according to the disclosure, the adjustment drive  444  of which is a hydraulic or pneumatic direct drive (instead of an electromechanical spindle drive  52 ). The coupling device  46  and a hydraulic arrangement  448  with a hydraulic locking device are also shown. 
     The adjustment drive  444  is composed of an electric motor  450 , a coupling  66 , a machine  68  which can be operated as a pump and as a motor, three check valves  70 ,  71 ,  72 , a 4/2 directional valve  74 , and a hydraulic/pneumatic cylinder  76 . 
       FIG. 8 b    shows the pump function, and  FIGS. 8 c  and 8 d    show the opening and closing movement of said drive. 
     Cavitation on the respective low-pressure side of the machine  68  is prevented by the check valves  70 ,  71 , which connect the low-pressure accumulator  24  to the in each case lower-pressure side. The leakage of the machine  68  is conducted via a leakage line  82  to the low-pressure accumulator  24 . 
     It is a prerequisite for the function that, during operation, the pressure in the annular chambers  13 ,  15  of the cylinder  14  is always greater than the pressure in the annular chambers  78 ,  80  of the cylinder  76 , because in this way the check valve  72  hydraulically separates the adjustment drive  444  from the annular chambers  13 ,  15  of the cylinder  14 . The separation is eliminated only during the pumping process. 
     The drive according to the fifth exemplary embodiment reduces the outlay in terms of construction because, aside from various lines, the items  16 ,  17 ,  18   a ,  18   b ,  19 ,  20  and  64  of the first exemplary embodiment (cf.  FIG. 3 ) are dispensed with. Furthermore, said drive increases reliability in relation to the adjustment drive  44  in the form of a spindle drive shown in  FIGS. 1 and 2 , because the twist prevention facility and nut lubrication required therein and the rolling bearing arrangement of the spindle can be dispensed with. Furthermore, through suitable selection of the size of the cylinder surfaces of the cylinder  76 , the electric motor  450  and the machine  68  coupled thereto can be ideally adapted to the movement to be performed. It is thus possible to use an electric motor  450  which is reduced in size in relation to the exemplary embodiments described above. A further simplification arises in that the pump function is inherent in the machine  68 . The machine  68  which is operated as a pump can, in interaction with the 4/2 directional valve  74  and the check valve  72 , increase the pressure in the annular chambers  13 ,  15  ( FIG. 8 b   ). The pump function of the piston  9 , the high-pressure accumulator  16  and the driving-side 3/2 directional seat valve  20 , which connects said high-pressure accumulator to the annular chamber  13 , are thus dispensed with. 
     During the pumping process, the two pistons  8 ,  9  remain in contact and do not move. The cylinder  76  is blocked by the 4/2 directional valve  74  which is switched into switching position b. A pressure reduction in the annular chambers  13 ,  15  by the 3/2 directional seat valve  32 , the lines  36   a  to  c , the check valve  33  and the orifice  34  is thus not necessary, such that this procedure can be omitted and the corresponding items can be dispensed with (cf.  FIGS. 3 and 4 ). 
     The drive according to  FIGS. 8 a  to 8 d    additionally requires a travel measurement device  84  configured to regulate the position of the valve body  2  with respect to the positionally fixed cylinder  14  via the electric motor  450 . The position of the nut of the spindle drive  52  as per the above-described exemplary embodiments is an exact function of the angle of rotation of the electric motor  50 . The spindle drive  52  thus does not require a travel measurement device. Said exact proportionality does not apply for the hydraulic direct drive as per the fifth exemplary embodiment owing to the volumetric efficiency of the machine  68  which is operated as a pump. 
     The device for speed limitation (orifice  23 ) illustrated in  FIGS. 1 to 8  and the hydraulic end position damping  5 ,  7  may alternatively also be electric, magnetorheological or pneumatic, or take place electrically, magnetorheologically or pneumatically. 
     A further exemplary embodiment (not shown) of the drive according to the disclosure relates to a butterfly valve. Here, according to the prior art, a drive with emergency function serves, via a rotatable shaft, to pivot in an opening or closing sense a closing plate which is fastened to said shaft. An adjusting drive and an emergency spring act on a thrust rod with a peg. Said peg is received in a slot of a lever to which the shaft is fastened. A longitudinal movement of the thrust rod thus leads, via the peg and the slot, to a pivoting movement of the lever and to a rotational movement of the shaft, as a result of which the closing plate of the butterfly valve which is fastened to said shaft opens or closes. Here, the emergency spring is constantly stressed or relaxed. 
     The drive according to the disclosure for a butterfly valve is based on the same principle as that described with reference to  FIGS. 1 to 4 and 8 . However, by contrast to the exemplary embodiments shown, in said drive (not shown) according to the disclosure for a butterfly valve, the force of the adjustment drive is introduced into the driving-side piston not at one side via the driving-side spring abutment but rather to the opposite side of said driving-side piston via a relatively long rod through the pivot drive. Here, the long rod extends through the thrust rod of the pivot drive, the driven-side piston rod, the driven-side piston, the driven-side spring abutment and a part of the emergency spring. 
     Disclosed is a drive with emergency closing function, having a movable coupling device which has an emergency spring braced between a driving-side spring abutment and a driven-side spring abutment. The emergency spring is preferably a compression spring which is moved jointly with the coupling device. A spacing of the spring abutments in a normal operating mode of the drive is fixed by a locking device, wherein, after a release or unlocking of the locking device, the emergency spring is configured to relax for an emergency function or emergency movement of the drive. Here, according to the disclosure, the locking device is hydraulically or pneumatically and/or magnetically actuated, or can be hydraulically or pneumatically and/or magnetically triggered. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Valve seat 
           2  Valve body 
           3  Driven-side spring abutment 
           4  Driven-side piston rod 
           5  Damping chamber 
           6  Emergency spring 
           7  Damping peg 
           8  Driven-side piston 
           9  Driving-side piston 
           10  Driving-side piston rod 
           11  Aeration duct 
           12  Driving-side spring abutment 
           13  Driving-side annular chamber 
           14  Cylinder 
           15  Driven-side annular chamber 
           16  High-pressure accumulator 
           17  Check valve 
           18   a ,  18   b  Orifice 
           19 ,  21  Pressure-limiting valve 
           20  Driving-side 3/2 directional seat valve 
           22  Driven-side 3/2 directional seat valve 
           23  Orifice 
           24  Low-pressure accumulator/tank 
           25  Check valve 
           26 ,  28  Spacer part 
           27  Coil 
           32  3/2 directional seat valve 
           33  Check valve 
           34  Orifice 
           36   a ,  36   b ,  36   c  Line 
           38 ;  138  Suction line 
           40  Relief line 
           42  Relief line 
           44 ;  444  Adjustment drive 
           46 ;  146 ;  346  Coupling device 
           48 ;  148 ;  448  Hydraulic arrangement 
           50 ;  450  Electric motor 
           52  Spindle drive 
           54   a ;  154   a  Driving-side portion 
           54   b  Driven-side portion 
           54   c  Central portion 
           56  Bypass line 
           58   a ,  58   b ;  458  High-pressure line 
           60  Low-pressure line 
           62  Bypass line 
           64 ;  164  Check valve 
           66  Coupling 
           68  Machine 
           70 ,  71 ,  72  Check valve 
           74  4/2 directional valve 
           76  Cylinder 
           78 ,  80  Annular chamber 
           82  Leakage line 
           84  Travel measurement device