DE1776078C - Servomotor with a pressure-medium operated actuator - Google Patents

Description

27. Servomotor according to claims 22 and components any number of settings with the highest Ge-23. characterized in that the actuator allows accuracy, without causing excessive (17) ^zusützl: ch in a side forces aufnehmen- demands on the manufacturing accuracy of the support bearing Find out is *. tent parts are provided.

35 Based on a servomotor with one of

an actuator acted upon by a pressure medium

This object is achieved in that the actuator of a known per se stepwise (digital) and

The invention relates to a servomotor with a continuously (analog) function that is known per se

actuator acted upon by a pressure medium. 40 control device, the effect of which is in series

Such servomotors are required in order to be switched, at the same time from its starting position

pneumatic or hydraulic working pressure can be moved in.

to cover a corresponding mechanical distance - this can preferably be done in stages, this distance through a longitudinal end adjusting device a piston or known per se also represented by a rotary movement 45 drive and the continuously operating control device can. be known per se diaphragm actuator.

According to their mode of operation, such actuating mo-

gates in Continuous, i.e. analog and in steps or several coupled with each other, in one

step-wise working servomotors divided. Similar to a single cylinder between two end positions

working steel motors usually have a 50 shiftable length according to a geometrical

Pressure medium acted upon diaphragm, the series of stepped pistons against the see, selecting the diaphragm

The force of a spring experiences a deflection, at least one of which is driven against a stiff spring

which is proportional to the pressure acting. having the cylinder acting membrane, the

For the adjusting ranges of the diaphragm drive, which work in steps or in stages, at least the

motors also include digital servomotors, 55 step of the smallest stage of the piston drive

whose manipulated variable corresponds to the controlling, parallel-.

IeI pending assessable code a limited by such a combination of a digital

Number of discrete values with the same distance from - servomotor with at least one analog servomotor

accepts each other. tor is a new and extremely advantageous hybrid type

Frictions in the drive mechanism of a pressure-operated servomotor created by a pressure-operated servomotor, a servomotor to be set and other devices and the possibility of using pneumatically defined counterforce: result in a disadvantageous outward and hydraulic systems considerably expanded. This acting uncertainty analog is especially true for the application of pressure mitt same operating positioning motor, so that such control motors actuated servomotors machines as actuators in Werkzeugmadurch control means to sequence plants or STEL 65 are preferably extended to position at the i ^T clungsmachern in the setting of the. As a result, the mutual assignment of workpieces and the work position of the servomotor is recorded as a control variable and is used to position stops and the like.
the pressure of the pressure meter fed to the servomotor. The setting steps of the servomotor can now

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executed with great accuracy as small as desired, errors occurring in the process are embodied,

the, with adjusting speeds that match those of a summing point of the pressure chamber of the

of digital servomotors approximately correspond. Diaphragm actuator acting pressure line

For this purpose, the pressure chambers are fed to the so that ζ. Β. Zero offsets

common cylinder arranged stepped pistons each- 5 balanced and constant or only long-

because with the same working pressure, the pressure space of the sam changing, of the work process, for example of the

Membrane drive compensated for errors resulting from different work tool wear

pressure applied. Of course, the · can be.

Diaphragm drive via a suitable valve arrangement According to a preferred embodiment of the Er

even with a detection stepped in its pressure level are for switching on the correction mechanism.

Pressure medium are acted upon, so that the devices pressure-medium-actuated membranes are provided.

log working part of the servomotor similar to a dihen, those in their rest position on projections

working part works. Through this measure of the cylinder overlying springs are assigned,

there is the advantage that the number of digital their spring force in each case also on the cylinder

Steps, especially for small steps, can be adjusted without large pressure screws arranged.

Effort can be increased. Of course, instead of membrane

According to a further feature of the invention, pistons, bellows and the like can also be used for devices

but also the step-by-step, i.e. digital, triggering of the energy storage mechanism for the correction inputs

Equipment from several continuous, i.e. analogous, work directions are used,

tend diaphragm drives exist, each of which in ao The correction facilities are preferred

their spring force differently stepped, stiff Fe- concentric to the axis of symmetry of the cylinder between

to which are assigned. In this way, the membrane drive and the actuator of the can see

crete lengths of extremely small values on economical servomotor, modified front ropes of the cylinder

be set in a liche way. orderly. For this purpose, the one facing away from the actuator

The hybrid servomotor is particularly advantageous, as the end face of the cylinder containing the stepped pistons

if, according to a further feature of the invention, the one receiving the correction devices

Each stepped piston of the digital piston drive has a flange and a central extension that

Pressure-actuated and analog working, system via the stiff spring with the membrane of the analog

conditional error eliminating correction device acting drive is connected. With a larger one

is assigned, each to the actuator, preferred 30 number of digital stages can have several such

but act wisely on the common cylinder. Flanges are arranged one behind the other.

According to a further feature of the invention, the assignment to the respective graduated piston is thereby achieved forced that the pressure areas of the individual are coupled with each other and in the common Correction devices each with the working cylinder arranged piston to the coupling pressure are applied, which is also the one to be used, arranged on both sides of the piston and corrective stepped piston is supplied. The perpendicular to the axis of symmetry of the cylinder in the Correction devices are preferably projections pointing in the same direction, which are from Pressure medium can be switched on, the effect of which is adjusted by ends of ends which are external on both sides of the piston Energy storage devices located on cross members or piston rods arranged in the middle of the cylinder Support the abutments. 4 ° are worn.

In this way, length errors of the digital The advantage of the arrangement is to be seen in working members of the servomotor corrected, and that the coupling surface of the in the same direction it is true that each of them is easy to edit individually according to the guiding principle or sentences effective stepped piston of the servomotor. the accuracy of the individual stepped pistons Of course, a correction of the actuating path embodied in the actuator 45 can be increased significantly. The servomotor can also be operated in an analogue manner. The accuracy is increased again if after the part of the servomotor. Correction with another feature of the invention provides help However, special correction drives have the jump in the axis of symmetry of the piston Advantage that the Zylingers lying stop surfaces due to manufacturing tolerances aufweiverursathten geometric length error of every 50 sen, dc .en size only a fraction of the Stepped piston detected separately and the respective associated coupling surface is. Be that way ripe correction variable can only be determined once. Since, even with normal maneuvering forces, there are high surface pressures each correction drive can be adjusted to this size, which is the influence of dust and dirt. the actuator of the servomotor is considerably reduced if the accuracy of the setting is relied on always set directly in 55 with pressure medium. In addition, small areas can be created Make the corrected, load-independent length setting more precise than large areas, convicted. Finally, another advantage of the Korrcktu in the common cylinder is to ensure proper guidance of the stepped piston ^ facilities to see that the number of digi- the projections on the inner wall of the cylinder talen steps is no longer as tightly limited as before, 60 sliding guide surfaces. That way will as manufacturing errors in the individual stages can be eliminated as far as possible, the piston jamming in the cylinder are. avoided.

As a result of its analog working parts, this is for the case that those of a tool are odd Actuator de ·, hybrid servomotor can be influenced by the workpiece acting on the servomotor the errors that are particularly large from the processing power and those from the analog process originate on a machine tool. For this purpose, the high adjustment accuracy achieved is maintained only the pressure medium, whose respective pressure is to be th, is according to a further feature Here the Wcrk / eunmuschinc own or in the case of the invention one triggered by a print medium

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face clamp provided through which penetrates the th. When the stops 6 on the actuator after the transfer to its setting position 7 are in contact, the stops 10 and II is detectable. exactly to the extent by which the study concerned

For this purpose, the actuator is supposed to move within its position piston, removed, namely by tion partially comprehensive pressure piece of a 5 the dimensions α, 2 α, 4 α, 8 α. The manipulated variables of the lever acted upon, the stepped pistons 2 to 5, which are differentiated by a pressure medium, are therefore after a struck piston against the action of a spring ordered in the rising geometric series is held in its inoperative position. To side-way that the adjustment of each subsequent step forces the actuator is also in piston twice as large as that of the previous one Support bearing led. io den. For each stepped piston in cylinder 1 there is a

In order to ensure the service life of the servomotor, the best compressed air supply line is arranged, via which the

influencing hard impacts during the adjustment process of the individual pressure chambers 12 to 15, in which the stepped piston

To exclude the connecting member furthermore according to the invention 2 to 5 divide the interior of the cylinder by

according to the actuator on a damping device. Connection lines 12a to 15 ″ under pneumatic

For this purpose, the actuator has a damping piston 15 that can be pressurized

The uppermost actuating piston 5 is firmly connected to an actuator bens via a channel 17, which is guided to the outside through a cylinder cover 18 which is easily adjustable through a cylinder cover 18. The pressure connection, whereby this throttle can also be regulated as a function of space 16 above the uppermost stepped piston 5, of the differential pressure of the damping fluid, which is provided in the cylinder chambers under pressure through a supply line 16 α. its effect on the stepped piston for example

The restoring force for the piston drive is half as great as the effect of the known manner via a pressure medium that acts on the control actuator fed to the end lines 12 α to 15 α in a returning sense, and presses on the remaining stepped pistons,
• »was with a pressure, the force of which is half as large as that of part II of the hybrid servomotor, as is that of the actuator from its protrusion. with cylinder 1 of the digital part through a

All details about the invention can be found in the extension 20 and with a diaphragm plate 21

the following description in connection with a spacer 22 is firmly connected. These parts

of the drawing, on which an embodiment of a 30 is located in a membrane housing 24, the orls-

Servomotor according to the invention, some execution is firmly arranged. Finally, there is a membrane 23

Rungsbeispielc provided in such a servomotor, which closes a pressure chamber 26, the

ordered actuating piston and a second execution through a supply line 26 a set under control pressure

shape of a servomotor can be seen to a greater or lesser extent,

are shown automatically. In detail, 35 is also shown for each stepped piston in the digital

F i g. 1 shows a section through a Druckmittelbetä- part I a correction element 25 available. This cor-

saturated servomotor according to the invention, rectifying members each consist of spring housings 26,

Fig. 2 to 4 different embodiments of the one with respect to Fig. 1 lower end face

Stellko! Bcn for a servomotor according to FIG. 1, side of the cylinder 1 forming flange 32 firmly with

F i g. 5 another embodiment of the digital 40 connected to the cylinder 1 and symmetrically to the

Part of the servomotor according to FIG. 1 and sen are arranged. Located in each spring housing

F i g. 6 a device for generating a digitally a soft spring 27 which is a pressure piece 28

valley stepped pressure for digital control of the against a housing-fixed stop 29 presses. the

analog working part of the servomotor according to the force of each spring 27 can by one also in the

F i g. 1. 45 flange 32 guided screw 30 can be adjusted.

I.ine in the following as a hybrid servomotor with a nut 31 to secure the setting drew, operated by a pneumatic pressure. Opposite each pressure piece 28 is a cut-out Facility consists, as in F i g. 1 shows, provided from release device. They each consist of a digitally operating part I and a Mcmbrangehäusc 33 which is arranged in an analog manner and is fixed to the housing Embedding part II. The digital part I consists of a diaphragm 34 with a diaphragm plate 35 a cylinder 1 which is closed on all sides and in which it is firmly connected. If air pressure is applied by a second piston 2 to 5 line 38, referred to as a stepped piston, is passed into the diaphragm housing are inserted so that they slide easily. The stepped pistons are lifted up to the stop 36 of the diaphragm plate 35 Provided on the underside with stops 6, which at the same time, the pressure piece 28 from the stop 29 7 attacks of hook-shaped Koppelgltedern 8 55 lifted and the force of the spring 27, which until then sit up. The coupling links 8 are each recorded by the stop 29, really Top of the previous stepped piston and on now onto cylinder 1 of the digital part I and beder attached lower cylinder wall. Furthermore, each has a corresponding deflection of the stiffer the stepped piston on its lower side a wide spring 19 and thus a length adjustment of the zyres hook-shaped coupling member 9. The coupling 60 linderst.

members and 9 are on the facing The operation of the above

Inside also with a stop 10 and device is the following:

11 provided. The attacks 6.7. 10 and U are the over one not shown here because not / ur He

ground and lapped end faces of Stahlslif-findung belonging control and regulating device is

th, which in the end faces of the stepped piston and the 65 by means of the connecting line 16a of the pressure H

Coupling links are used, namely at the constantly supplied with compressed air, so that. if the An

Place at which the imaginary symmetry line of the closing lines 12a to ISa do not carry any compressed air

Graduated piston containing cylinder this end face all parts of the digital part 1 in I ig. ) darge

posed to take position. This means that the actual supply line 12 a to ISo is also

Liche actuator 17 in its starting position. If lines 38 are connected to a correction element 25, so

corresponding to a code pending in parallel that when controlling one of the stepped pistons 2 to

Compressed air through some of the connecting lines, e.g. B. 5, the assigned correction element is also

through the connection lines 12 a and 15 a, in which 5 is controlled. Each correction link is at the assembly

Pressure chambers 12 and 15, the step days of the hybrid servomotor move according to the

pistons 2 and 5 with respect to FIG. I up until the failure of the associated stepped piston with

The stops 10 have been adjusted to the stops 11 to abut with the aid of the screw 30 and correct

long. All other stepped pistons therefore always remain directly opposite when it is activated

gen under the influence of the length error prevailing in the pressure chamber 16 in the already described

seeing pressure, the force of which about half as much.

is as great as that of the pressure in the supply lines 12a instead of the stepped piston 2 shown in FIG

to 15 a in the position shown. Actuators up to 5 can also have stepped pistons of other configurable

17 is adjusted by the amount used. In the case of the

a f 8 a. 15 provided example, the coupling links consist of to

At the same time α through the feed line 26 and both sides of the respective piston, here of the stages of the pressure chamber 26 of the analog part Il of the piston 3, eccentrically arranged crossbars 42, does not control illustrated and regulating device having at their end faces in the same direction on the Compressed air at a predetermined pressure supplies the imaginary axis of symmetry of the cylinder 1. As a result, the membrane 23 experiences opposing projections 41 which, due to the action of the stiff spring 19, have a deflection which is proportional to the pressure inside the cylinder and which extends over the central surfaces 40. The stops 6, 7, 10 and 11 cylinder 1 carried by the projections and extension 20 on the piston containing the actuator 17, so that this one white also experiences the ground and lapped frontal deflection here. The actuator 17 is therefore as seen from steel pins.

the digital part I and the analog part II of the hy- In Fi g. 3, the crossbars 42 are rod-shaped

briden servomotor at the same time from its in Fig. 1 and have the projections 41 three by about

dargesieiiieii Aüsgangsiagc has been moved. Guide surfaces 40 offset from one another by 120 °

The analog part II can also be controlled digitally. This ensures better guidance of the piston

be approved. A device for generating a di- 30 against tipping and better protection against

digital pressure for digital control of the rotation of the piston against the upstream or downstream

Analog Part II is shown in FIG. 6 shown schematically. reached piston.

One supply air line 8t a, 81 b, 81 c and 81 d each. Finally, Fig. 4 shows another embodiment

over which the device of an actuating piston, not shown here, in which the projections

The source provided is supplied with compressed air, 35 41 corresponds to the diameter of the piston 3

via a three-way switch 82 a, 82 b, 82 c and discs, the two opposite one another

82 d with one cylinder 83 a, 83 ft, 83 c and 83 d each have recesses 44 and 45. The disks

connected. Their diameters are different, are each of two also opposite

7. B. graded according to a geometric series. Depending on the bolt-shaped crossbars 42 and 42 a worn, the

Actuation of the three-way switch is the 4 ° mentioned in pairs with respect to the piston by 90 ° in relation to one another.

Cylinder with the pressure source or with the other offset by means of screws 50 are attached.

Outside air connected. In the cylinders slide in them- These pistons, before they enter cylinder 1,

ren diameters corresponding stepped pistons are set, in the form of a chain with the rest

84 ". 84 b, 84 c and 84 d, which are assembled via piston rod pistons.

Support gen 85 on a common cross member 95. 4S Another embodiment of the digital part I.

The traverse acts on the servomotor via a coupling rod 86, as shown in FIG. 5. Here are one on dai

a diaphragm plate 87 of a diaphragm 88, which acts in actuator 17, the influence of restoring

a housing 96 is clamped into which a force - that of a tool or a

Compressed air supply line 92 having throttle 90, a workpiece can be exerted on the servomotor - aul

Lead 93 and a control line 94 open. With 50 the actuator preventing clamping device M

the diaphragm is connected to a closing cone 91, which and the service life of the servomotor is unfavorable

interacts with the control line 94. preventing influencing impacts during the actuation process «

The parts just described form a Kaska- damping device 50 provided,

denrejjler, with which, depending on the position of the three-way all with the embodiment according to FIG. 1 same

Switches 82 in pressure chamber 89 of housing 96 are five-fold and have the same reference numerals

ten different air pressures can be generated, and will not be explained in more detail. Also in this

the control piston according to the execution via the control line 94 to the analogous part II embodiment

of the servomotor shown in Fig. 1 is used individually in the form of Fig. 2,

are feasible, so that these fifteen different The already mentioned damping device 50 is

Take settings, so also work digitally 60 housed in a cylinder 48, which is connected to the Zy

can. linder 1 is axially connected. The actuator 17 consists

Finally, with the setting of the actuator, here is made up of a guide part 49 and a Kniben

17 a correction has also been made to rod 51, which autaeisl a damping piston 52

Due to manufacturing tolerances and similar errors in both parts are with a piston 53 of the last Stu

to compensate for the setting of the actuator. To 65 piston by means of a screw cap 54 firmly connected

For this purpose, the activated Stufenkol- The cylinder spaces 55 and 56 on both sides de

ben 2 and 5 associated correction members 25 with damping piston 52 are with a damping fluid '

Using the supply lines 38 has been switched on. Filled with fluid and sealed by sealing rings 57 and 58

seals and communicates with one another via channels 59 and 60. The channel 59 can be adjusted by the Throttle screw 61 more or less throttled according to the desired damping will. Instead of the simple throttle screw, one can also use one under the effect of the differential pressure the damping fluid standing throttle can be used with which the flow rate through the throttle can be regulated.

The clamping device 46 is penetrated on the lateral surface by the actuator 17 at 74 on the end face housed bell-shaped hood 62 of the servomotor and has a lever 63 which is rotatably mounted about a bolt 64. A Nu-ε 65 of the lever 63 is by a spring 66 against a Pressure piece 67 pressed, which is perpendicular to the main axis

the cylinder 1 and 48 is movably arranged in the end face of the hood 62 and thereby clamps the Actuator 17 fixed. A cylinder 68, in which a piston 69 moves, is arranged coaxially with the spring 66, which is supported against the lever 63 by means of a pressure piece 70. The cylinder 68 i <= t through a cover 71 completed. If compressed air is passed into a connection 72, it presses over the Piston 69 and over the pressure piece 70 and over the

ίο Lever 63 the spring 66 together. This gives the Lift! the pressure piece 67 freely and the actuator 17 can move freely. On the other hand, there is no pressure in the Cylinder 68 is present, so the actuator 17 is locked again. The face of the bell-shaped hood 62 at the same time forms a support bearing for the actuator 17 that absorbs cable forces.

Hicrau 2 sheets of drawings

Claims (26)

Patent claims: 1. Servomotor with an actuator acted upon by a pressure medium, characterized in that the actuator (17) is controlled by a step-by-step (digital) known per se and by a continuously (analog) operating control device (I and II) that is known per se, which are connected in their effect in series ^gle: chzeitig from its starting position is movable 2. Servomotor according to claim 1, characterized in that the per se known step-wise actuating device (I) a piston drive (2 to S) and the per se known continuously operating actuating device (II) a diaphragm drive (19, 23) in ' 3. Servomotor according to claims 1 and 2, characterized in that one of the piston drive (2 to 5) generated longitudinal movement *> of the actuator (17) one of the diaphragm drive (19, 23) generated longitudinal movement is superimposed. 4. Servomotor according to claims 1 to 3, characterized in that the adjustment range of the »5 Membraiuintriebs (19, 23) at least the adjusting step the smallest digital level (2) of the KoI benantricbs covered. 5. servomotor according to speeches 1 to 4, thereby characterized in that the pressure spaces (12 to 15) are arranged in the common cylinder (1) Stepped piston (2 to 5) each with the same working pressure, the pressure chamber (26) of the Diaphragm drive (19, 23) can be acted upon with different working pressures. 6. Servomotor according to claim 5, characterized in that the pressure chamber (26) of the Diaphragm drive (19, 23) supplied pressure medium is graduated in its pressure level. 7. Servomotor according to claim 1, characterized in that the stepwise (digital) working device (I) consists of several continuously (analog) working diaphragm drives, each of which is assigned stiff springs with different levels of spring force. - 8. Servomotor according to claims 1 to 6, characterized in that each stepped piston (2 to S) of the piston drive a pressure medium-operated and analog correcting device (25) is assigned, each acting on the common cylinder (1). 9. Servomotor according to claim 8, characterized in that the pressure chambers (38) of the correction devices (25) each with the pressure roughness (12 to 15) of the stepped piston (2 to 5) the working pressure supplied to the piston drive can be acted upon. 10. Servomotor according to claim 8, characterized in that the correction devices (25) are switchable via pressure medium, adjustable in their effect energy storage device (27), which Support on abutments (29) arranged on the cylinder (1). 11. Servomotor according to claims, characterized in that that for switching on the correction devices (25) pressure medium-actuated Membranes (34) are provided, which in their rest position on abutments (29) of the cylinder (1) overlying springs (27) are assigned, the spring force of which is also applied to the cylinder (1) arranged pressure screws (30) adjustable 12 servomotor according to claims, characterized in that that the correction devices (25) are concentric about the axis of symmetry of the cylinder (1) between the diaphragm drive (19, 23) and the end face facing away from the actuator (17) (32) of the cylinder (1) are arranged. 13. Servomotor according to one or more of the preceding claims, characterized in that that the end face of the cylinder (1) facing away from the actuator (17) has a flange (32) for Receipt of the correction devices (25) and a central extension (20) which extends over the stiff spring (19) is connected to the membrane (23) of the continuously acting drive (II). 14. Servomotor according to claim 13, characterized in that that the membrane housing (24) of the continuously acting drive (II) carrier for the Membraniiihaiise (33) of the respective energy storage (27) is in the operative position transferring membrane (34) 15. Servomotor with several unci coupled to one another in a common cylinder arranged piston, each occupying one of two end positions, according to claims I to 6, characterized in that the coupling is arranged on both sides of the piston (2 to 5) Projections (41) at right angles to the axis of symmetry of the cylinder (1) in the same direction point and off-center from the ends of on both sides of the piston (2 to 5) Traverses (42) are carried. 16. Servomotor according to Claim 5, characterized in that that the projections (41) in the axis of symmetry of the piston (2 to 5) leading Cylinder (1) have horizontal stop surfaces (6, 7, 10, 11), the size of which is only one Fraction of the coupling area. 17. Servomotor according to claims 15 and 16, characterized in that the stop surfaces (6, 7, 10, 11) the end faces of hardened, in the end faces of the projections (41) and the Pistons (2 to 5) are embedded steel pins. 18. Servomotor according to claims 15 to 17, characterized in that the projections (41) have sliding guide surfaces (40) on the inner wall of the cylinder (1). 19. Servomotor according to claims 15 to 18, characterized in that each projection (41) has three guide surfaces offset from one another by 120 ° (40). 20. Servomotor according to claims 15 to 19, characterized in that the projections (41) are the diameter of the piston (2 to 5) corresponding discs, each having two opposing recesses (44), and each of two also opposite, however are carried in pairs with respect to the piston (2 to 5) by 90 ° offset from each other cross members (42, 42 a) . 21. Servomotor according to claims 1 to 3, characterized in that the restoring force for the piston drive (I) is half as large as that moving the actuator (17) from its starting position Power. 22. Servomotor controlled according to one or more of the diums as a manipulated variable. Through appropriate preceding Claims, characterized by the formation of the servomotor can be pre-drawn in this way, that one of a print medium ejection paths of the order of 0.1 mm exactly releasable clamping device (46) is provided. through which the actuator (17) after the transfer 5 With digital servomotors, larger feed tion can be determined in its setting position. ways - ζ. B. greater than 0.1 to 1 mm - quickly reacts 23. Servomotor according to claim 22, characterized and characterized by such a return to the position cork that an internal rectification of the actuator (17) is not required, since the positioning of the load within its bearing (62) is partly comprehensively dependent. The setting error is here only the pressure piece (67) acted upon by a lever (63) due to the accuracy of the individual points, which is determined by a piston that acts on the pressure medium, i.e. the number of points,
struck piston (69) against the action To achieve the desired accuracy, a spring (66) is in its inoperative position, therefore, is held up for the production of such servomotors. dige manufacturing methods necessary. Another IA. Servomotor according to one of the preceding 15 disadvantage is in the limited possibility of adjustment to claims, characterized in that see. For example, in the case of a digital actuator (17), a damping device (50) servomotor with four actuating pistons, whose paths have a ratio of I: 2: 4: 8 in steps, when activated 25. Servomotor according to claim 24 characterized by the code 1-2-4-8 sixteen discrete positions, indicates that the actuator (17) an ao Are 'further positions required, the grows Has dampening piston (52) and the two-number of actuating pistons very quickly and dnmil with gieiden Side of the damping piston (52) arranged rather manufacturing accuracy of the setting error. Uttering Cylinder chambers (55, 56), which with the isi only a limited number of actuating pistons si-damping liquid-jit are filled, via a one more likely to lead in a cylinder, such as Channel (60) having throttle (61) with one another is shown in German Auslegeschrift 1 223 258. who are connected. The invention has for its object to be a 26. Servomotor according to claim 25, thereby creating a new pressure-medium-actuated servomotor, indicates that the throttle (61) depending on the advantageous properties of the above speed of the differential pressure of the damping fluid-described types of servomotors combined and is controllable. 30 through special training and arrangement of his