JPH0828745A - Valve driving actuator - Google Patents

Abstract

PURPOSE:To surely maintain stability for controlling a valve opening position and maintain linearity accuracy and improve energy efficiency by providing a ball screw reduction gear between the operating shaft of a power cylinder and the output shaft of an actuator. CONSTITUTION:Pressure difference between both the upper and lower chambers 25 and 26 of a cylinder 22 in a control valve actuator 10 is adjusted so that a current opening reaches a command opening by a positioner for receiving a valve opening command from a host system and an opening feedback from an actuator output shaft. Then, downward thrust exerted on an operating shaft 24 connected to a piston 23 enables an output shaft 27 to be driven through the linear movement of a first ball screw 31, the integral rotating movement of a first nut 33, a connecting member 35 and a second nut 34 and the linear movement of a second ball screw 32 in a ball screw reduction gear 30. When this opening feedback coincides with the opening command, the actuator 10 is kept balanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic actuator or the like for driving a flow rate (pressure) regulating valve for process control.

[0002]

2. Description of the Related Art Generally, a pneumatic actuator such as a flow rate (pressure) control valve used under high temperature and high pressure conditions in a thermal power plant for business uses a wide range of fluid pressure in the valve body. ) Stability of valve opening position control, (2)
Securing of linearity accuracy and (3) improvement of energy efficiency are desired.

The stability of the valve opening position control is as follows: (a) the thrust thrust of the actuator is sufficient against the pressure fluctuation on the load side, and (b) the output thrust is constant over the entire stroke of the actuator. , (C) It is ensured by making the stroke of the power cylinder relatively large with respect to the required unit stroke of the actuator output shaft.

Further, ensuring the linearity accuracy means that the ratio of the displacement position of the power cylinder operating shaft to the displacement amount of the actuator output shaft is constant over the entire stroke, and the resolution for the valve opening command signal is constant over the entire opening position. It means that there is. When this linearity accuracy is ensured, it becomes possible for the host system to easily correct the gain of the valve opening command signal in response to changes in the valve flow rate characteristics due to fluid pressure fluctuations in the valve body.

However, conventionally, as a valve driving actuator, there is one as described in Japanese Patent Application Laid-Open No. 4-312274 or Japanese Utility Model Laid-Open No. 63-37879.

Japanese Patent Application Laid-Open No. 4-312274 discloses a valve drive actuator that linearly drives an output shaft by thrust of a power cylinder. The valve is opened by air pressure and is closed by a compression spring. Is provided with a mechanism for increasing the driving force.

Japanese Utility Model Laid-Open No. 63-37879 discloses a valve drive actuator which directly drives a valve stem by displacement of a diaphragm which receives fluid pressure. It is provided with a stroke increasing mechanism for increasing the movement.

[0008]

[Patent Document 1] Japanese Unexamined Patent Publication No.
The prior art described in Japanese Patent No. 312274 has the following problems. Since it is a spring balance type that uses a compression spring,
The actuator applies the spring pressure at each opening position to the thrust on the load side, and as a result, the actual effective output thrust output to the load side changes significantly depending on each opening position, and a constant output cannot be obtained. Opening position control lacks stability. Further, depending on the opening position, most of the driving force of the actuator is spent for compressing the spring, and the energy efficiency is very poor.

Since the lever is rotationally moved, the action point and the force point of the lever are circular motions, and the thrust and displacement transmission amount are not constant at each opening position. Therefore, the resolution for the valve opening command signal depends on the opening position. There is a drawback that they are different, and it is difficult to secure the linearity accuracy in controlling the valve opening position.

Further, since the conventional technique disclosed in Japanese Utility Model Laid-Open No. 63-37879 increases the stroke of the valve element, the thrust is naturally reduced, and it is required for a unit stroke of the actuator output shaft. The stroke of the power cylinder becomes smaller and the stability of the valve opening position control is poor.

SUMMARY OF THE INVENTION It is an object of the present invention to ensure stability of valve opening position control, ensure linearity accuracy, and improve energy efficiency in a valve drive actuator.

[0012]

According to a first aspect of the present invention, there is provided a valve driving actuator for linearly driving an output shaft by thrust of a power cylinder, the valve driving actuator being provided between an operating shaft of the power cylinder and an output shaft of the actuator. A ball screw speed reducer is provided, and the ball screw speed reducer is (a) connected to the operating shaft of the power cylinder and guided to the housing side of the actuator so that only linear movement is possible, and ( b) A second ball screw that is connected to the output shaft of the actuator and is guided to the actuator housing side so that only linear movement is possible, and (c) It is screwed into the first ball screw, and only rotational movement is possible on the actuator housing side. Nut that is supported on the actuator, and (d) a second nut that is screwed into the second ball screw and is supported only on the housing side of the actuator so that it can only rotate. And (e) a connector that connects the first nut and the second nut, and (f) the lead of the second ball screw is set smaller than the lead of the first ball screw. is there.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, a manual reciprocating device including a worm gear and a worm wheel is further provided, and the manual reciprocating device is provided with a manual reciprocating device via a clutch. The connector is adapted to be connectable.

According to a third aspect of the present invention, in addition to the second aspect of the present invention, the clutch is automatically engaged by a spring return type miniature cylinder when the power source of the power cylinder is lost, and the manual operation is performed. The output shaft of the actuator can be locked by the reverse rotation stop function of the worm gear that constitutes the reciprocating device.

[0015]

According to the present invention described in claim 1,
Has the effect of The stroke of the power cylinder is decelerated by the speed reducer to become the output stroke of the actuator, and the thrust thrust of the actuator against the pressure fluctuation on the load side becomes sufficiently large.

Since the reduction gear ratio of the reduction gear transmission is constant at all opening positions, the output thrust of the actuator is constant at all strokes.

Since the stroke of the power cylinder is reduced by the reduction gear to be the output stroke of the actuator, the stroke of the power cylinder can be made relatively large with respect to the required unit stroke of the actuator output shaft. Due to the above items, the stability of the valve opening position control can be ensured.

The ratio of the amount of displacement of the power cylinder operating shaft to the amount of displacement of the actuator output shaft through the speed reducer on this operating shaft is constant in all strokes, that is, the resolution for the valve opening signal is at all opening positions. Since the crossover is constant, linearity accuracy can be secured.

Let Tc be the thrust of the power cylinder,
When the output thrust of the actuator is Ta, Ta
= Tc × 1 / i × η (i: reduction ratio, η: transmission efficiency), and η is a simple combination of a ball screw and a nut, and therefore high efficiency of 0.90 or more and good energy efficiency.

A first ball screw on the cylinder actuating shaft side of the ball screw speed reducer and a second ball screw on the actuator output shaft side are connected via a connector for connecting two nuts forming a pair with each ball screw. Since they are connected, the reduction ratio can be arbitrarily selected according to the lead ratio of both ball screws.
A large reduction ratio can be obtained in a small space, and backlash (backlash), which cannot be avoided by the reduction gear, can be reduced to an extreme value that does not become an unstable factor in the valve opening position control due to the general characteristics of the ball screw.

According to the second aspect of the present invention, there are the following effects. Since the manual reciprocating device can be connected to the connector via the clutch, when the power source of the power cylinder is lost, the manual reciprocating device and the connector are connected by the clutch so that the upper and lower chambers of the power cylinder are equalized. The valve opening position can be manually adjusted by driving the connector (and thus the second nut) by a manual reciprocating operation using a manual handle or the like.

According to the present invention described in claim 3, the following effects are obtained. When the power source of the power cylinder is lost, the spring return type miniature cylinder automatically connects the manual reciprocating device and the connector by the clutch. As a result, the actuator output shaft includes the second ball screw, the second nut,
It is immediately locked by the reverse rotation stop function by the worm gear of the manual reciprocating device via the connector. Therefore, the valve opening position at the time of an emergency abnormality in the plant operation called loss of power source can be held on the spot. After that, the valve opening position can be manually adjusted by the manual reciprocating device by equalizing the pressures in the upper and lower chambers of the power cylinder, as described above.

[0023]

1 is a longitudinal sectional view showing an embodiment of a valve driving actuator according to the present invention, and FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a schematic diagram showing an example of a control valve, and FIG. 4 is a schematic diagram showing a positioner.

The actuator 10 of FIG. 1 drives, for example, the control valve 11. As shown in FIG. 3, the control valve 11 includes a valve box 15 having an inlet channel 12, an outlet channel 13, and a valve chamber 14, and a valve seat 16 formed in the valve chamber 14 of the valve box 15.
And a valve stem 18 movably supported by the valve box 15 and provided with a valve body 17.

The actuator 10 is provided with the control valve 1
1. A housing 21 mounted on the valve box 15 of 1,
Pneumatic power cylinder 22 is provided on the top of this housing 21.
It has. The cylinder 22 has a piston 23 and an operating shaft 24, and a positioner 50, which will be described later, has a piston 23.
Control air pressure C applied to each of the upper chamber 25 and the lower chamber 26
1, the actuating shaft 24 is moved up and down by the thrust caused by C2. S is the supply air pressure.

The actuator 10 has an output shaft 27 to which the valve rod 18 of the control valve 11 is connected, and the power cylinder 2
A ball screw speed reducer 30 is disposed between the second actuating shaft 24 and the output shaft 27, and the thrust of the cylinder 22 drives the output shaft 27 to move up and down linearly.

As shown in FIGS. 1 and 2, the ball screw speed reducer 30 includes a first ball screw 31, a second ball screw 32, and
The first nut 33, the second nut 34, the rotating body-like connector 35
Is configured.

The first ball screw 31 is the power cylinder 2
It is connected to the second actuating shaft 24, and is guided to the housing 21 side of the actuator 10 so that only linear movement is possible. In the present embodiment, the linear motion guide of the first ball screw 31 includes cam followers 37 provided at both ends of an arm 36 fixed to a connecting portion between the first ball screw 31 and the operating shaft 24 and extending in a diametrical direction. It is made to fit into a guide groove 38 formed by notching in the vertical direction of the housing 21. That is, the guide groove 38 is provided in the stroke range of the cylinder 22 so as to be parallel to the first ball screw 31.

The second ball screw 32 is used for the actuator 1
It is connected to the output shaft 27 of 0 and is guided to the housing 21 side of the actuator 10 so that only linear movement is possible. In this embodiment, the linear motion guide of the second ball screw 32 is made by engaging the key 39 provided on the outer peripheral portion of the second ball screw 32 with the key groove 40 formed in the housing 21 by notching. . In other words, the key groove 40 is
It is provided so as to be parallel to the second ball screw 32 over the stroke range.

The first ball screw 31 and the second ball screw 32 are coaxially arranged. In this embodiment, in order to make the height of the actuator 10 compact, the second ball screw 32 has an opening at its upper end surface. A hollow portion 41 is provided so that the lower end portion of the first ball screw 31 can enter the hollow portion 41. Due to the decelerating action of the ball screw speed reducer 30, the movement amount of the second ball screw 32 is determined by the first ball screw 31.
Is smaller than the moving amount of the first ball screw 31, and the lower end portion of the first ball screw 31 penetrates into the hollow portion 41 of the second ball screw 32 by the difference in the moving amount.

The first nut 33 is screwed into the first ball screw 31 and is supported on the housing 21 side of the actuator 10 so as to be rotatable only. The rotation guide of the first nut 33 will be described later. First ball screw 31 and first nut 3
The screw backlash of 3 is generally significantly smaller than the meshing backlash of gears and the like.

The second nut 34 is screwed into the second ball screw 32 and is supported on the housing 21 side of the actuator 10 so as to be rotatable only. The rotation guide of the second nut 34 will be described later. Second ball screw 32 and second nut 3
The backlash of the screw 4 is generally significantly smaller than that of the meshing backlash of the gear or the like.

The rotor-shaped connector 35 connects the first nut 33 and the second nut 34. That is, the first nut 33 is fixed to the connector 35 by the set screw 42, and the second nut 3
4 is fixed to the connector 35 by a set screw 43. At this time, the upper and lower end surfaces of the connector 35 are rotatably supported by the housing 21 of the actuator 10 through the upper and lower thrust bearings 44 and 45, and as a result, the first
As described above, the nut 33 and the second nut 34 are rotationally guided. The push screw 46 screwed into the housing 21 presses the upper thrust bearing 44,
As a result, the connector 35 can only rotate with respect to the housing 21 without any play in the axial direction.

In the ball screw speed reducer 30, the second
The lead L2 (for example, 20 mm) of the ball screw 32 is set smaller than the lead L1 (for example, 64 mm) of the first ball screw 31. As a result, when the operating shaft 24 of the power cylinder 22 moves by, for example, L1, the first ball screw 31
Also moves by L1 and the first nut 33 makes one rotation. This one rotation of the first nut 33 passes through the connector 35 to the second rotation.
The nut 34 is also rotated once. One rotation of the second nut 34 moves the second ball screw 32 by L2, and thus the output shaft 27 of the actuator 10 by L2. Therefore, the ball screw speed reducer 30 converts the movement amount L1 of the operating shaft 24 of the power cylinder 22 into the movement amount L2 of the output shaft 27 of the actuator 10, and the reduction ratio i thereof is the lead of both ball screws 31, 32. Ratio of L2 / L1.

The position control of the actuator 10 (position control of the piston 23 of the power cylinder 22) is shown in FIG.
Positioner 50. That is, the positioner 50 is made on the principle that two opposing forces are balanced. The position of the actuator 10 is determined by the magnitude of these forces, and the position is maintained. The positioner 50 balances when the moment of the upward force exerted by the loading bellows 51 becomes equal to the moment of the downward force exerted by the positioning spring 52. The force of the loading bellows 51 is determined by the control signal pressure P sent from the control system. The force of the positioning spring 52 is determined by the position of the piston 23 (same as the position of the valve rod 18 and the output shaft 27) and the shape of the positioning cam 53. The positioner drive arm 54 is connected to the positioner drive rod 55, and the piston 2
The position corresponding to each position of 3 is taken. Drive arm 54
Are connected to the positioning cam 53 by a gear 56. The cam 53 is a spring beam 57 and a cam follower 5.
The assembly of 8 is moved to give a strong and weak tension to the positioning spring 52. Therefore, the tension of the spring 52 depends on the position of the piston 23. The cam 53 determines the relationship between the piston position and the spring tension, and is selected so that the relationship between the control signal pressure P and the piston position has a desired characteristic. When the forces of the loading bellows 51 and the positioning spring 52 are in balance, the balance beam 59 keeps the pilot valve stem 61 in the balance position, and creates a pressure difference necessary to balance the load side with the respective ports of the piston 23. Keep the position of. When the pilot valve stem 61 is in the neutral position, since the ball portion of the stem is located at the center of the pilot port, equal pressure is generated in each port and equal pressure is applied to both sides of the piston 23. The control system changes the control signal pressure P, and the actuator 1
When instructed to operate 0, the force acting on the balance beam 59 by the loading bellows 51 increases or decreases. This causes the balance beam 59 and the pilot valve stem 61 to move up and down, increasing the control pressure on one side of the piston 23 and decreasing the pressure on the other side. When the piston 23 moves due to this pressure difference, the tension of the positioning spring 52 becomes equal to the moment due to the bellows 51, the pilot valve stem 61 returns to the balance position again, and the piston 23 stops at the new position instructed.

The actuator 10 also has a manual reciprocating device 70. The manual reciprocating device 70 includes a worm gear 71 supported by the housing 21 and a connector 35.
It is composed of a worm wheel 72 supported around a radial bearing 79. The worm wheel 72 of the manual reciprocating device 70 is connectable to the connector 35 via the clutch 73. Clutch 7
3 can be moved up and down by being guided by a key 74 provided on the outer peripheral portion of the connector 35, and the claw 73A of the clutch 73 and the claw 72A of the worm wheel 72 can be engaged and disengaged.

The clutch 73 is vertically moved by a spring return type miniature cylinder 75. In the miniature cylinder 75, a cam follower 76 provided on the tip end portion of the piston rod is engaged with a circumferential cam groove 77 provided on the outer peripheral portion of the clutch 73. Therefore, during normal operation of the actuator 10, the miniature cylinder 7
The contraction operation of 5 causes the clutch 73 to move to the worm wheel 7
It is pulled up and held in a non-meshing position with 2. Then, when the power source of the power cylinder 22 is lost, the spring 75A of the miniature cylinder 75 immediately pushes the clutch 73 down to the meshing position with the worm wheel 72, and the output shaft 27 of the actuator 10 is locked by the reverse rotation stop function of the worm gear 71. As described above, in a state where the clutch 73 and the worm wheel 72 are engaged with each other, and the upper chamber 25 and the lower chamber 26 of the power cylinder 22 are pressure-equalized by the pressure equalizing valve 78, the worm gear 7 of the manual reciprocating device 70 is provided.
When 1 is rotated by a manual handle or the like, the connector 35 can be rotated and the output shaft 27 of the actuator 10 can be moved, and the valve opening position of the control valve 11 can be manually adjusted.

The actuator 10 operates as follows. The positioner 50 receives the valve opening command from the host system,
The cylinder 22 receives the opening feedback from the actuator output shaft 27 so that the current opening becomes the command opening.
The pressure difference between the upper and lower chambers 25 and 26 is adjusted.

Although FIG. 1 shows the upper limit position of the piston 23 (100% at the valve opening), the pressure at the upper part of the piston is increased based on the closing direction operation command (for example, opening command 50%) from the host system. At the same time, the pressure in the lower part is lowered, and as a result, downward thrust is generated on the operating shaft 24.

The downward thrust of the operating shaft 24 is caused by (a) linear movement of the first ball screw 31 in the ball screw speed reducer 30, (b) integral movement of the first nut 33, the connector 35, and the second nut 34. The output shaft 27 of the actuator 10 is moved through the rotational movement (c) and the linear movement of the second ball screw 32. At this time, the reduction ratio i of the ball screw speed reducer 30 is the ratio L2 / L1 of the leads of both ball screws 31, 32 as described above, and when the output thrust of the actuator 10 is Ta and the thrust of the power cylinder 22 is Tc, Ta = Tc × 1 / i × η (transmission efficiency) is obtained.
Here, since the transmission efficiency η is a combination of the first ball screw 31 and the first nut 33 and the second ball screw 32 and the second nut 34, the transmission efficiency η is 0.90 or higher.

When the opening feedback from the output shaft 27 coincides with the opening command, the actuator 10 is in a balanced state, and the thrust on the load side and the ball screw speed reducer 30.
Positioner 5 to balance the thrust on the drive side via
Zero adjusts the pressure difference between the upper and lower chambers 25 and 26 of the cylinder 22.

When the opening command from the host system becomes 0% and the valve fully close command is issued, the output shaft 27 is further lowered, and when the lowering operation is restricted at the seat position on the valve 11 side, the positioner 50 inside the positioner 50 is closed. Upper chamber 25 of cylinder 22 due to signal deviation
While increasing the pressure of to almost the same pressure as the supply pressure,
When the pressure in the lower chamber 26 is released to the atmosphere, the maximum thrust is generated on the output shaft 27. This maximum thrust ensures the deadline of the control valve 11.

When the supply pressure of the drive source of the power cylinder 22 is lost, the pressure equalizing valve 43 is opened and the cylinder 22
By equalizing the pressures in the upper chamber 25 and the lower chamber 26 and operating the manual reciprocating device 70 with a manual handle or the like, the output shaft 27 of the actuator 10 can be moved to a desired position.

The operation of this embodiment will be described below. The stroke of the power cylinder 22 is decelerated by the speed reducer 30 to become the output stroke of the actuator 10, and the thrust thrust of the actuator 10 against the pressure fluctuation on the load side becomes sufficiently large.

Since the reduction gear ratio of the reduction gear transmission 30 is constant at all opening positions, the output thrust of the actuator 10 is constant at all strokes.

The stroke of the power cylinder 22 is the speed reducer 3.
Since the output stroke of the actuator 10 is reduced by 0, the stroke of the power cylinder 22 can be made relatively large with respect to the required unit stroke of the output shaft of the actuator 10. Due to the above items, the stability of the valve opening position control can be ensured.

The ratio of the amount of displacement of the operating shaft 24 of the power cylinder 22 to the amount of displacement of the output shaft 27 of the actuator 10 via the speed reducer 30 on the operating shaft 24 is constant over the entire stroke, that is, the valve opening degree. Since the resolution for the signal is constant over all opening positions, linearity accuracy can be secured.

When the thrust of the power cylinder 22 is Tc and the output thrust of the actuator 10 is Ta, Ta = Tc × 1 / i × η (i: reduction ratio, η: transmission efficiency), and η is a simple Since it is a combination of the ball screws 31 and 32 and the nuts 33 and 34, the efficiency is 0.90 or higher and the energy efficiency is good.

The two ball nuts 31 of the ball screw speed reducer 30 on the side of the cylinder operating shaft 24 and the second ball screw 32 on the side of the actuator output shaft 27 are paired with the respective ball screws 31, 32. Since they are connected via a connector 35 that connects 33 and 34, the reduction ratio can be arbitrarily selected by the lead ratio (L2 / L1) of both ball screws 31 and 32, and a large reduction ratio can be obtained in a small space. At the same time, the backlash (backlash) unavoidable in the speed reducer 30 can be reduced to an extreme value that does not become an unstable factor of the valve opening position control due to the general characteristics of the ball screw.

Since the manual reciprocating device 70 can be connected to the connector 35 via the clutch 73, the manual reciprocating device 70 and the connector 35 are connected by the clutch 73 when the power source of the power cylinder 22 is lost. Power cylinder 2
(2) With the pressure in the upper and lower chambers 25, 26 equalized, the connector 35 (and thus the second nut) can be driven by a manual reciprocating operation using a manual handle or the like to manually adjust the valve opening position.

When the power source of the power cylinder 22 is lost, the spring-return type miniature cylinder 75 automatically causes the manual reciprocating device 70 and the coupler 35 to move to the clutch 7.
Connected by 3. As a result, the actuator output shaft 27 is immediately locked by the reverse rotation stop function of the worm gear 71 of the manual reciprocating device 70 via the second ball screw, the second nut, and the connector 35. Therefore, the valve opening position at the time of an emergency abnormality in the plant operation called loss of power source can be held on the spot. After that, the valve opening position can be manually adjusted by the manual reciprocating device 70 by equalizing the pressures in the power cylinder upper and lower chambers 25 and 26, as described above.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and changes in design within the scope not departing from the gist of the present invention can be made. Even if it exists, it is included in the present invention. For example, the connector of the present invention may be formed by integrally molding the first nut and the second nut.

[0053]

As described above, according to the present invention, in the valve driving actuator, the stability of the valve opening position control can be secured, the linearity accuracy can be secured, and the energy efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a valve driving actuator according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a schematic view showing an example of a control valve.

FIG. 4 is a schematic diagram showing a positioner.

[Explanation of symbols]

 10 Actuator 11 Control Valve 21 Housing 22 Power Cylinder 24 Operating Shaft 27 Output Shaft 30 Ball Screw Reduction Gear 31 First Ball Screw 32 Second Ball Screw 33 First Nut 34 Second Nut 35 Connector 70 Manual Reciprocating Device 71 Worm Gear 72 Worm wheel 73 Clutch 75 Miniature cylinder 75A Spring

Claims (3)

[Claims] 1. A valve drive actuator for linearly driving an output shaft by thrust of a power cylinder, wherein a ball screw speed reducer is arranged between an operating shaft of the power cylinder and an output shaft of the actuator. The speed reducer is (a) connected to the operating shaft of the power cylinder, and is guided to the housing side of the actuator so that only linear movement is possible.
The ball screw and (b) the second that is connected to the output shaft of the actuator and is guided to the actuator housing side so that only linear movement is possible.
A ball screw, (c) a first nut that is screwed to the first ball screw and is supported only on the actuator housing side for rotational movement, and (d) a second ball screw is screwed to the actuator housing side. A second nut that is rotatably supported by the first ball screw, and (e) a connector that connects the first nut and the second nut to each other. A valve drive actuator characterized by being set smaller than the reed. 2. The valve driving actuator according to claim 1, further comprising a manual reciprocating device including a worm gear and a worm wheel, the manual reciprocating device being connectable to the connector through a clutch. 3. When the power source of the power cylinder is lost, the clutch is automatically meshed with a spring return type miniature cylinder, and the output shaft of the actuator is controlled by the reverse rotation stop function of the worm gear constituting the manual reciprocating device. The valve driving actuator according to claim 2, wherein the actuator is lockable.