Electric actuator and actuator with an electric actuator

Abstract

Electric actuator (1) for an actuator with safety actuating function for positioning an actuator, such as a valve element, of a process plant, comprising an electric motor (5) for providing a torque for actuating the actuator, wherein the electric motor (5) has a motor shaft (21) for delivering the torque, an output shaft (3) for transmitting the torque from the electric motor to the actuator, and a coupling (11) for providing and / or interrupting a torque-transmitting connection between the motor shaft (21) and the output shaft (3), characterized by the fact that the output shaft (3), the motor shaft (21) and the clutch (11) are arranged coaxially to each other, and that the electric actuator (1) further comprises: a planetary gear set (7) arranged coaxially to the output shaft (3) for transmitting the torque from the electric motor (5) to the output shaft (3), wherein the motor shaft (21) provides the torque from the electric motor (5) to the gear set, and that the motor shaft (21) extends in its axial direction (A) from the gearbox to the electric motor (5) through the clutch (11) and through a centrifugal brake (13) and / or through a ring gear (75).

Description

[0001] The invention relates to an electric actuator for an actuator with a safety actuating function for positioning an actuator, such as a valve element, in a process plant, such as a chemical plant, for example a petrochemical plant, a power plant, a food processing plant, a heating plant, for example a heating plant for a building, a part of a building, such as an apartment, or a room of a building, or the like. The invention also relates to an actuator with a safety actuating function comprising an actuator, such as a valve element, in a process plant and an electric actuator according to the invention.

[0002] An actuator with an electric drive is known, for example, from DE 195 19 638 A1. The known actuator comprises a valve actuator with a safety actuating function for operating a valve. The known actuator includes a drive motor whose rotation is reversible, and whose drive force can be transmitted via a gearbox to a plunger for valve actuation. The actuator further comprises an electromagnetic brake or clutch and a spring accumulator acting on the plunger, which, in normal operation of the actuator, is coupled to the drive motor by the action of the electromagnetic brake or clutch.In the event of a power failure, the valve in the known actuator is moved to a defined, usually closed, position for safety reasons by disengaging the electrical coupling between the electric motor and the plunger. This allows the spring to act on the plunger, moving the valve to its defined (closed) position. In the known actuator and other actuators of this type with a safety function, the driving electric motor must be designed to provide a sufficient minimum torque to move the actuator to its target position, despite the continuous action of the spring, which forces the control valve towards the closed position. The known actuator has proven itself in practical applications and enjoys great popularity.However, there is a desire to provide the functionality of the known actuator in a smaller installation space, while keeping the acquisition and maintenance costs of the actuator as low as possible.

[0003] DE 37 08 470 C1 discloses an actuator for a valve comprising an electric actuator motor connected to a valve spool via a spindle drive and a first gearbox arranged coaxially thereto. A spring drive is arranged between the spindle drive and the actuator motor, the capacity of which is designed for a full spindle stroke. A controllable clutch is provided parallel to the spring drive, which locks the spring drive in one operating position and releases it in the other operating position, so that the valve closes automatically in the event of a power failure.

[0004] DE 195 19 638 A1 discloses a valve actuator with a safety actuating function for operating a valve, consisting of a drive motor whose direction of rotation is reversible and whose driving force acts via a gearbox on a plunger for valve actuation, an electromagnetic brake, and a spring accumulator which, in normal operation, is coupled to the drive motor by the action of the electromagnetic brake. The spring accumulator is designed as a rotary spring accumulator, the output shaft of which is connected to an eccentric body that acts on the plunger, wherein the lever arm of the eccentric body continuously changes its length in the closing range of the valve and has its shortest length when the valve is closed.

[0005] EP 0 851 163 A2 discloses an electric actuator for a valve with an axially displaceable actuating spindle connected to a threaded spindle drive. The threaded spindle drive is driven by an electric actuator motor via two coaxially mounted gear units. The two gear units are identical planetary gear sets coupled in series and are directly driven by the coaxially arranged actuator motor. A magnetic rotary encoder is mounted on the actuator motor shaft as an incremental position signal generator. The position signals from this encoder are fed to a microprocessor, which controls the actuator motor accordingly.

[0006] EP 2 784 361 A1 discloses an electrically actuated actuator for a rotary spool valve, comprising an operating shaft for actuating the valve and an electric motor with a drive shaft for rotating the operating shaft from a first to a second rotary position. The actuator further includes a spring element for pre-tensioning the operating shaft back to the first rotary position and a clamping arrangement with an electrically actuated solenoid and a push rod, which tensions a tensioning belt around a drive element to fix the operating shaft in the second rotary position.

[0007] The invention is based on the objective of providing an actuator with a safety positioning function or an electric actuator for an actuator with a safety positioning function that overcomes the disadvantages of the prior art and in which, in particular, the required installation space is reduced; preferably while maintaining or reducing the acquisition and operating costs.

[0008] This problem is solved by the subject matter of independent claim 1.

[0009] Accordingly, an electric actuator is provided for a control device with a safety actuating function for positioning an actuator, such as a valve element, in a process plant, a chemical plant, in particular a petrochemical plant, a power plant, a food processing plant, a heating plant, or the like. The electric actuator comprises an electric motor for providing torque to actuate the actuator, wherein the electric motor has a motor shaft for delivering the torque, a drive shaft for transmitting the torque from the electric motor to the actuator, and a coupling for providing and / or interrupting a torque-transmitting connection between the motor shaft and the drive shaft.

[0010] Preferably, the coupling is implemented as a normally-disengaging coupling. This can be particularly advantageous if the safety function is to be activated in the event of a power failure, a failure of an electrical signal, or the like. Alternatively or additionally, the coupling can be an electromagnetic coupling. An electromagnetic coupling can, for example, be implemented with two soft magnetic cages and a coil, wherein preferably the coil and one of the cages are fixed in position (fixed to the housing), and in particular rotationally fixed relative to a stationary part of the electric motor, while the second cage is rotatable and connected to the torque-transmitting connection between the motor shaft and the drive shaft. When the coil of the electromagnetic coupling is energized, the two soft magnetic cages can exert a mutual holding torque on each other.Preferably, the electric actuator according to the invention comprises exactly one electric motor. For example, a 50 Hz synchronous motor can be used as the electric motor, which is particularly well suited for use with the power supply of the standardized European 50 Hz power grid, whereby no additional transformers are required to adapt the mains current to the motor. Alternatively, a DC motor can be used as the electric motor.

[0011] According to the invention, the drive shaft, the motor shaft, and the coupling are arranged coaxially to one another. Surprisingly, it has been found that when the coupling is arranged coaxially to the motor shaft and drive shaft, the required installation space of an electric actuator according to the invention, as well as the number of individual components, can be significantly reduced compared to a conventional electric actuator. An advantage of the actuator according to the invention is that it allows the components of an actuator to be arranged on fewer axes than usual, by eliminating the separate axis of the coupling required in the prior art. Preferably, the mains-powered part of the electric motor and / or, if applicable, the coupling can be arranged in a fixed position, particularly relative to a housing of the electric actuator or actuator.This avoids the need for increased investment in the costs of wiring the (mains) powered parts of the electric motor and, if applicable, the electromagnetic coupling.

[0012] According to a preferred embodiment of the invention, the electric actuator further comprises a gearbox, preferably arranged coaxially to the drive shaft, in particular a planetary gearbox, for transmitting the torque from the electric motor to the drive shaft, wherein the motor shaft provides the torque to be transmitted, in particular the drive torque, from the electric motor to the gearbox. Other gearboxes are also conceivable. Preferably, the gearbox comprises several gearbox components that are movable relative to one another, such as a torque input gearbox component, a torque output gearbox component, and / or a torque transmission gearbox component or torque transfer component. The motor shaft can be connected to a torque input gearbox component in a rotationally fixed manner, in particular by material, positive, or frictional locking.The output shaft can be connected to a torque output transmission component in a rotationally fixed manner, in particular by material, form, or force locking. It should be understood that a reduction or multi-ratio transmission provides an output torque to the input shaft that differs from the input torque directly applied to the shaft coming from the motor. In this respect, a distinction can be made between an input torque on the input side of a transmission and an output torque on the side of the transmission furthest from the motor. However, it should be understood that when the term "torque" is used in general, it can encompass both input torque and output torque, and, where applicable, in the presence of multiple transmission stages, input torques and output torques.

[0013] It is clear to a person skilled in the art that the entire power supplied to the actuator is present at the output of the electric motor in the form of the drive speed and drive torque present there, and that this power cannot be exceeded regardless of any over- or under-reductions in one or more gear stages and defines the torque of the electric motor which the electric motor provides to actuate the actuator.

[0014] The gearbox of the electric actuator preferably consists of exactly one gear stage. Preferably, the gearbox of the electric actuator is designed as a reduction gearbox, in particular with exactly one reduction gear stage. Preferably, the reduction gearbox has a reduction ratio of at least 2, 3, 5, 7, or 9. A gearbox designed as a reduction gearbox is particularly well suited for converting a low input torque at a high input speed into a higher output torque at a lower output speed. The gearbox is particularly preferably not self-locking. A non-self-locking gearbox is particularly well suited for combination with a spring accumulator provided on the output side of the gearbox for moving the actuator into the safe position.

[0015] According to a preferred embodiment of an electric actuator according to the invention, the preferably reducing gear is designed as a planetary gear. A planetary gear comprises (as gear components) a central, coaxial sun gear, an outer, internally toothed, coaxial ring gear, and at least one planet gear, preferably several planet gears, in particular an odd number of planet gears, for example three or five planet gears, which are arranged between the sun gear and the ring gear and mesh with the ring gear and the sun gear. A planetary gear further comprises (as a further gear component) a planet carrier which is connected to the at least one planet gear or the several planet gears, wherein the planet gear(s) are rotatably mounted on the planet carrier about their planet gear axis, preferably on a shaft or axle body of the planet carrier.In particular, the output shaft can be implemented, at least in part, as a planetary gear unit of the gearbox. Alternatively, a planetary gear unit of the planetary gearbox can be directly connected to the output shaft in a torque-transmitting manner, preferably non-rotatably, by frictional and / or positive locking. Additionally or alternatively, the motor shaft can be non-rotatably connected to the sun gear of the planetary gearbox. Such a configuration of the gearbox as a planetary gearbox with a driven sun gear and driven planet gears with a preferably stationary ring gear is particularly well suited for a relatively high reduction ratio.

[0016] In a preferred embodiment of the invention, which can be combined with the one described above, a transmission component, preferably a ring gear, of the transmission, which may optionally be designed as a planetary gear set, is rotationally fixed relative to a rotatable part of the coupling. Preferably, in this preferred embodiment of an electric actuator, the coupling comprises a coupling part that is stationary relative to the electric motor and / or the actuator housing. The coupling can be functionally subdivided into a rotatable part that can perform a rotational movement together with at least one part of the torque-transmitting connection between the motor shaft and the drive shaft, and a stationary coupling part that is preferably stationary and / or fixed to the housing.In combination with the transmission described above, particularly the planetary gear system, such a coupling offers the advantage that a transmission component of the transmission, in particular the ring gear of the planetary gear system, can optionally be stationary to provide a power-transmitting connection between the motor shaft and the output shaft, or optionally, when the coupling is open, the transmission component, in particular the ring gear, can be free-running, so that other transmission components, for example the planet gears between the sun gear and the ring gear, run freely, so that practically no torque transmission takes place between the motor shaft and the output shaft.

[0017] In a preferred embodiment of an actuator according to the invention, the electric motor is designed with a preferably constant rated speed of at least 200 revolutions per minute, at least 500 revolutions per minute, at least 1000 revolutions per minute, at least 3000 revolutions per minute, or at least 6000 revolutions per minute. In a preferred embodiment of an actuator according to the invention, the direction of rotation of the electric motor is reversible. Preferably, the electric motor is a synchronous motor designed for operation in a 50 Hz power grid. According to an alternative preferred embodiment, the electric motor can be a DC motor.

[0018] In a preferred embodiment of an electric actuator according to the invention, a centrifugal brake, preferably arranged coaxially to the drive shaft, is non-rotatably connected to the gearbox and / or the clutch. In particular, the centrifugal brake can be non-rotatably connected to a gearbox component, especially the ring gear, of the gearbox. When using the electric actuator according to the invention as part of an actuator with a safety positioning function, it has proven advantageous to provide a centrifugal brake that preferably does not generate a braking force during the actuator operation, i.e., during the actuation of the actuator by the electric motor.Furthermore, it has proven advantageous that a centrifugal brake is designed to provide a braking force, preferably a braking force dependent on the acceleration of the output shaft, when the safety positioning function is performed by the actuator. This braking force preferably activates above a certain acceleration threshold to prevent damage to the actuator due to excessive acceleration. Preferably, the electric actuator comprises a brake pot that interacts with the centrifugal brake and is stationary on a housing and / or stationary relative to the stationary part of the coupling or the electric motor.

[0019] In a preferred embodiment of an electric actuator according to the invention, the motor shaft extends axially from the gearbox, in particular the gearbox input component or torque input gearbox component, especially the sun gear of a planetary gearbox, to the electric motor, preferably into and / or through the stationary part of the electric motor. The motor shaft preferably extends completely through the clutch, its stationary and / or rotating part, and / or optionally through the centrifugal brake, its rotating part, and / or its brake housing. In this arrangement, the motor shaft penetrates the clutch and optionally the centrifugal brake in the axial direction. This preferred arrangement allows for a particularly compact design of the actuator.

[0020] In a preferred embodiment of an electric actuator according to the invention, the motor shaft is axially segmented and radially surrounded, preferably completely, by a sleeve or hollow shaft. The hollow shaft is, in particular, rotatably mounted relative to the motor shaft and / or supported on the motor shaft. The hollow shaft can preferably be mounted on the motor shaft as a plain bearing. Preferably, the hollow shaft is non-rotatably connected to a transmission component, preferably a torque transmission component, in particular the ring gear, the rotatable part of the centrifugal brake, and / or the rotatable part of the clutch.The use of a hollow shaft surrounding the motor shaft for torque transmission between a transmission component, in particular the ring gear, of the transmission, which is particularly equipped as a planetary gear, and the clutch, and optionally the centrifugal brake, improves the bearing stability of the rotating parts, i.e., the bearing of the motor shaft during positioning operation and, when the safety positioning function is triggered, the rotational movement of the hollow shaft with the clutch and optionally the centrifugal brake mounted on it.

[0021] In a preferred embodiment of an electric actuator according to the invention, which can be combined with the previous one, the motor shaft extends at least partially through a stator and / or a rotor of the electric motor, wherein the motor shaft is preferably rotatably mounted on both sides of the electric motor in the axial direction. Preferably, a rolling bearing, in particular a ball bearing, is provided on each side of the electric motor for rotatable axial mounting of the motor shaft. The use of a particularly long special shaft as the motor shaft for transmitting the torque from the electric motor to the actuator allows further components, in particular the coupling, to be arranged in a space-saving manner between the electric motor and the actuator or a gearbox upstream of the actuator, for example a reduction gearbox such as a planetary gearbox.In a preferred embodiment of an electric actuator, at least 25%, at least 33%, at least 40%, or at least 50% of the motor shaft extends axially outside the motor. In a preferred embodiment of an electric actuator according to the invention, which can be combined with the previous one, the axial extension of the motor shaft is at least 25%, at least 33%, at least 40%, or at least 50% greater than the axial extension of the electric motor. When using such extra-long special shafts, it has surprisingly proven advantageous with regard to the stability of the shaft and its rotational movement to provide bearings, which preferably include a stationary part connected to a housing of the electric motor.Due to the very high speeds achievable, for example by the preferably used synchronous motors, direct current motors or DC motors, from several hundred to over a thousand revolutions per minute, rolling bearings, such as ball bearings, are particularly suitable for bearing applications.

[0022] The invention further relates to an actuator with a safety actuating function, comprising an actuator, such as a valve element, for adjusting the process fluid flow of a process plant, such as a chemical plant, for example a petrochemical plant, a food processing plant, a power plant, a heating system, for example a floor heating system or central heating system, or the like, as well as an electric actuator designed as described above. The actuator may, in particular, have an eccentric actuated by the output shaft for linearly actuating the valve element. Alternatively, the actuator may, in particular, have a spindle drive, such as a threaded spindle, actuated by the output shaft for linearly actuating the valve element.

[0023] In a preferred embodiment of an actuator according to the invention, a spring accumulator, in particular a rotary spring accumulator, is included for moving the actuator into a safety position, particularly when the clutch and / or the electric motor is de-energized, wherein the spring accumulator is preferably arranged coaxially to the output shaft and / or the motor shaft. Preferably, the spring accumulator can be arranged on both sides relative to the transmission described above.

[0024] A preferred embodiment of an actuator according to the invention comprises an actuator housing consisting of two housing halves. In particular, the electric actuator according to the invention can preferably be completely housed in a first housing half. Preferably, all electrical connections of the actuator can be provided in the first housing half. Preferably, an output eccentric and, optionally, a spring accumulator, particularly coaxial with the motor shaft, are housed in a second housing half. In such an embodiment, the actuator comprises a motor shaft that defines the drive axis, as well as a bearing shaft or output shaft for defining the axis of rotation of the output eccentric, wherein the axis of rotation of the output eccentric is coaxial with the drive axis. Such an embodiment allows for the realization of a particularly compact actuator.

[0025] According to an alternative embodiment of an actuator according to the invention, the actuator and the output eccentric can be arranged with the axis of rotation of the eccentric and the drive axis in parallel and, in particular, can be housed within the same housing shell, preferably with separate chambers provided for receiving the actuator according to the invention on the one hand and the output eccentric on the other. In the second alternative embodiment of an actuator, the bearing axis that defines the axis of rotation of the eccentric can be supported on both sides of the eccentric on the actuator housing, so that a particularly stable eccentric bearing can be achieved, which in particular prevents the transmission of imbalances of the eccentric to the output shaft of the actuator.In this alternative embodiment of an actuator according to the invention, at least one torque-transmitting component, such as a spur gear, can be provided between the output shaft of the actuator and the output eccentric. Preferably, such a spur gear is designed as a two-stage reduction spur gear.

[0026] In a preferred embodiment of an actuator according to the invention, a further transmission, in particular a planetary transmission and / or reduction transmission, preferably a multi-stage planetary transmission, especially with driven sun gear(s) and / or driven planetary gear segments, can be provided upstream of the output eccentric. If the actuator housing is implemented according to the second alternative, the further transmission is preferably housed in the eccentric chamber of the housing. Preferably, the further transmission is a planetary transmission, in particular a multi-stage, preferably a two-stage planetary transmission.In particular, several gearboxes can be used for reduction in an actuator, i.e., additional gearboxes besides the gearbox of the actuator, whereby, for example, a high overall reduction ratio of at least 100, at least 500, at least 1000, at least 2000 or even at least 5000, preferably 500 to 3000, in particular 1000 to 2000 can be achieved.

[0027] Further advantages, features and properties of the invention will become clear through the following description of preferred embodiments of the invention with reference to the accompanying drawings, which show: Fig. 1 a sectional view of an electric actuator according to the invention; Fig. 1a an exploded view of the actuator according to Fig. 1; Fig. 2 a first embodiment of an actuator according to the invention with an actuator according to the invention Fig. 1; and Fig. 3 a cross-sectional view of a second, alternative actuator according to the invention with an actuator according to the invention Fig. 1.

[0028] The in Fig. 1 and Fig. Figure 1a shows a preferred embodiment of an actuator 1 according to the invention comprising as its main components an electric motor 5 with a motor shaft 21, an output shaft 3, and an electromagnetic clutch 11, which, when energized, provides a torque-transmitting connection from the motor shaft 21 to the output shaft 3. The motor shaft 21 and the output shaft 3 are arranged coaxially with each other. Their respective or common axis of rotation defines the motor axis A.

[0029] Ball bearings 23, 25 are attached to both sides of the housing of the electric motor 5 in the direction of the motor axis A for the rotatable mounting of the motor shaft 21 relative to the stationary part of the electric motor 5. The motor shaft 21 extends completely through the stationary part of the electric motor 5 in the axial direction A, up to the gearbox. Fig. In the preferred embodiment of an actuator 1 according to the invention, shown in Figure 1, the transmission is implemented as a planetary gear set 7, which comprises as transmission components a sun gear 71, three planet gears 76, a ring gear 75, and a planet gear carrier 73. The sun gear 71 of the planetary gear set 7 is rotationally fixed to the motor shaft 21 and serves as the transmission input component. The drive torque applied by the motor 5 to the motor shaft 21 is introduced into the planetary gear set 7 via the sun gear 71, in order to be transmitted via the planetary gear set 7 to the output shaft 3 and from there further in the direction of the Fig. 1. Actuator not shown.

[0030] When the electromagnetic clutch 11 of the actuator 1 is energized, the ring gear 75 of the planetary gear 7 is stationary. The ring gear 75 of the planetary gear 7 is connected to a rotatable part 12 of the electromagnetic clutch 11 via a hollow shaft 27. When the electromagnetic clutch 11 is energized, an electromagnet 10 exerts holding forces between the stationary part 15 and the movable part 12 of the electromagnetic clutch 11. The stationary part 15 and the movable part 12 of the electromagnetic clutch 11 are implemented as soft magnetic claws. The stationary part, also referred to as the stationary part 15, is connected to the stationary part of the electric motor 5 and the housing 35 of the actuator in a rotationally fixed manner. The actuator housing 35 is designed to be anchored in a rotationally fixed manner in an actuator housing (135, 135') as explained below, for example by flange mounting.The actuator housing 35 can also be referred to as the mounting section or actuator flange. The electromagnet 10 belongs to the stationary part 15 of the electromagnetic coupling 11. Both the electromagnet 10 of the coupling 11 and the electric motor 5 can be supplied with power by stationary power lines that do not need to be subjected to rotational movement.

[0031] The hollow shaft 27 completely surrounds the motor shaft 21 in the radial direction. A sliding fit can be provided between the hollow shaft 27 and the motor shaft 21. A centrifugal brake 13 is provided on the hollow shaft 27 in the axial direction A between the ring gear 75 and the rotatable part 12 of the electromagnetic clutch 11. The centrifugal brake 13 is rotationally fixed to the hollow shaft 27. Radially relative to the axial direction of the motor shaft A, surrounding the centrifugal brake 13, a brake pot 17 is provided in the actuator housing 35, with which the centrifugal brake 13 can enter into frictional contact to generate a braking force. The centrifugal brake 13 comprises two brake arms arranged rotationally symmetrically to each other, in the radially outer section of which recesses, for example bores, are provided for receiving weights, for example dowel pins, made of metal, in particular lead.The pot 17 is preferably pressed into the actuator housing 35 and can, in particular, be held rotationally fixed relative to the mounting section 35. For a rotationally fixed connection of the hollow shaft 27 with the components arranged radially on its outer surface, i.e., the rotatable coupling part 12, the centrifugal brake 13 and / or the ring gear 75, a splined connection, a non-circular connection, a press fit, a toothed shaft connection or the like may be provided, for example.

[0032] If the ring gear 75 of the planetary gear 7 of the in Fig. 1 and Fig. Since the actuator 1 shown in Figure 1a is fixed in position relative to the housing and the electric motor 5 by the current-energized coupling 11, the planet gears 76 can roll in the ring gear 75, driven by the movement of the sun gear 71. The ring gear 75 and the planet gears 76 act as torque transmission components. The rolling motion of the planet gears 76 also moves the planet gear carrier 73, which rotatably supports the planet gears 76. The in Fig. The planet gear carrier 73 shown in Figure 1a is made in two parts and, when assembled, forms a cage structure for receiving the planet gears 76. The two halves of the planet gear carrier 76 can be firmly connected by a snap-fit ​​or detent connection. The planet gear carrier 73 has pins for supporting the planet gears 76. The output shaft 3 is formed integrally with the planet gear carrier 73 and has a gear profile on its outer surface. The output shaft 3 can transmit the output torque of the planetary gear set 7 via its external gear profile. The planet gear carrier 73 constitutes a transmission output component or torque output transmission component.

[0033] When the clutch 11 of the actuator 1 is opened, which in the illustrated preferred embodiment can be achieved by de-energizing the electromagnetic clutch 11, the rotatable part 12 of the clutch 11 can move independently of the stationary part 15 of the electromagnetic clutch 11. The electromagnetic clutch 11 then exerts no holding or braking force on the rotatable clutch part 12. Consequently, the holding force that keeps the ring gear 75 stationary also disappears. When the ring gear 75 is not held stationary by the clutch 11, it is free to rotate. When the ring gear 75 is free to rotate, the planet gears 76 do not roll within the ring gear 75. By disengaging the clutch 11, the rotary motion of the output shaft 3 can be transmitted directly to the ring gear 75 via the planet carriers 73 and the planet gears 76. The ring gear 75 rotates with the output shaft 3 when the clutch 11 is disengaged.

[0034] If the ring gear 75 is not stationary, no or only very slight torques are transmitted from the sun gear 71 via the planet gears 76 to the planet gear carrier 73. If the ring gear 75 is free-running, the planet gears 76 can rotate freely within the ring gear 75, so that a movement of the sun gear 71 causes no or at most an extremely slight rotational movement of the planet gear carrier 73.

[0035] If a torque acts on the output shaft 3 on the side of the transmission furthest from the motor, for example by an actuator return spring, this torque can act on the output shaft 3 unimpeded by a drive torque from the electric motor 5 when the clutch 11 is disengaged. It should be understood that instead of the electromagnetic clutch 11 shown, an alternative type of clutch may be provided to establish and / or disconnect a torque-transmitting connection between the motor shaft 21 and the output shaft 3, for example a friction clutch, a dog clutch, or the like.

[0036] The electric motor 5 of the actuator 1 can preferably be dimensioned such that even in the de-energized state, a small torque acts from the electric motor 5 on the motor shaft 21. Such a minimum torque can be provided, for example, by the permanent magnets of an electric motor designed as a synchronous motor, DC motor, or other type of motor. If the clutch were also closed in the de-energized state, the minimum torque of the motor, due to the high gear ratio and speed of the transmission, could be sufficient to cause the actuator 1 to self-lock against actuation of the output shaft 3 by the spring accumulator. Such a safety-critical self-locking is avoided by disengaging the clutch to interrupt the torque-transmitting connection.

[0037] When a torque from the side opposite the drive is applied to the output shaft 3 with the clutch 11 open, this accelerates the output shaft 3 in the direction of rotation of the torque opposite the drive. The rotatable ring gear 75, which is fixedly connected to the centrifugal brake 13, is also rotated by the output shaft 3. The centrifugal brake 13 is designed to provide an acceleration-dependent braking effect. The higher the acceleration of the centrifugal brake 13, the further the centrifugally acted brake arms of the centrifugal brake 13 move radially outwards until, at a design-determined acceleration limit, they reach a sliding contact or frictional contact with the brake drum 17 in order to exert the braking effect of the centrifugal brake 13. In this way, the centrifugal brake 13 prevents dangerous sudden movements resulting from high accelerations.

[0038] The in the Fig. 2 and Fig. The three different actuators 101 and 102 shown according to the invention each comprise an actuator 1 as described above. For ease of reading and to avoid repetition, the same or similar reference numerals are used below for the same or identical components.

[0039] The actuator 101 according to Fig. 2 comprises as its main components an actuator 1 with an electric motor 5, a motor shaft 21, an output shaft 3 and a clutch 11 for providing and / or interrupting a torque-transmitting connection between the motor shaft 21 and the drive shaft 3.

[0040] As a further main component, the actuator 101 includes according to Fig. 2 an actuator that is in Fig. 2 is shown only schematically as control valve 113. The control valve 113 of the actuator 101 is designed to perform a translational movement. The control valve 113 of the actuator 101 is actuated by a plunger 111 of the actuator 101, which is subjected to the torque of the electric motor via an eccentric 103. The eccentric 103 is rotatably mounted about an eccentric bearing axis 121. The eccentric 103 is specifically designed to perform a maximum rotational movement amplitude of less than 180°, preferably less than 135°, and particularly less than 90°. The rotational movement of the eccentric 103 is translated into a translational actuator movement via the plunger 111.

[0041] A rotary spring accumulator 105 is rigidly connected to the eccentric 103. The spring accumulator 105 is designed to move the eccentric 103 such that the control valve 113 is moved into a predetermined safety position. This safety position can be, for example, a fully open or a fully closed valve position. The spring accumulator 105 comprises a torsion spring that is supported on one side by the eccentric housing 139 and rigidly connected to the eccentric 103 on the other. The spring accumulator 105 can be designed to maintain a predetermined safety spring force excess in the predetermined safety position, so that sufficient closing force is ensured, particularly in a safety closed position.

[0042] The eccentric 103 is completely enclosed within the eccentric housing 139. The eccentric bearing axis 121 is fully surrounded by the eccentric housing 139 in its axial direction and around its entire circumference. The spring accumulator 105 is completely surrounded by the eccentric housing 139 along its axial spring height and in the circumferential direction.

[0043] The actuator 1 is surrounded by the drive housing 135. The drive axis A, which is defined by the motor shaft 21, is, in the preferred embodiment, according to Fig. The eccentric bearing axis 121 and the eccentric axis E defined by the eccentric bearing axis 121 are arranged coaxially. The axis of rotation E of the eccentric 103 is arranged coaxially with the motor axis A. The drive housing 135 and the eccentric housing 139 are oriented coaxially to each other and are fastened together at their end faces, for example by screws. The output shaft 3 of the actuator 1 is integrally connected to the planet gear web 73 of the planetary gear 7 as a gear-like extension and can project out of the drive housing 135 in the axial direction A.

[0044] The output shaft 3 of the actuator 1 can be directly or indirectly connected to the eccentric 103 for torque transmission. In the preferred embodiment of the actuator 101 according to Fig. 2. The torque transmission from the output shaft 3 to the eccentric 103 is effected indirectly via a further gearbox 107, which is implemented as a two-stage planetary gearbox. In the further gearbox 107, ring gears are provided that are fixed to the eccentric housing (139) and in which planet gears roll. The output shaft 3 acts as the sun gear of the first gear stage of the further gearbox 107. The eccentric bearing axis 121 extends from the eccentric housing 139 into the output shaft 3 to support the eccentric 103 and the further gearbox 107. The central planet carrier and the sun gear, which connects the two planetary gear stages of the further gearbox 107 and is formed integrally with it, are also rotatably mounted on the eccentric bearing axis 121.

[0045] The eccentric 103 has pins for rotatably mounting the second planetary gears of the further gearbox 107. The further gearbox 107 provides a further reduction in torque. The drive torque of the electric motor 5 is converted by the planetary gear 7 of the actuator 1 into the output torque present at the output shaft 3.

[0046] The output torque of the actuator acts as a drive torque on the further gearbox 107 and is converted by the further gearbox 107 into an output torque applied to the eccentric 103, with which the eccentric 103 actuates the plunger 111 and thus the valve element 113. As described above, torque is transmitted from the electric motor 5 of the actuator 1 to the eccentric 103 of the actuator 101 only when the clutch 11 is closed. If the clutch 11 is opened, for example, in the preferred embodiment described here by de-energizing the electromagnetic clutch 11 so that the electromagnetic holding force between the stationary clutch part 15 and the rotatable clutch part 12 is eliminated, the ring gear 75 of the planetary gear 7 of the actuator 1, which is non-rotatably connected to the rotatable clutch part 12, is also no longer held in a fixed position and is therefore essentially free to rotate.The torque from the electric motor 5 is then practically no longer transmitted from the sun gear 71 to the planet gear carrier 73.

[0047] With the clutch 11 de-energized and open, the spring accumulator 105 continues to exert a torque on the eccentric 103. This spring accumulator torque, as described above, moves the control valve 113 into the predetermined safety position. The resulting rotational movement of the eccentric 103 about its axis of rotation E causes the pins of the eccentric 103, which support the ring gears of the secondary transmission 107, to move. This movement of the eccentric 103 then moves the secondary transmission 107, which is transmitted to the output shaft 3.The output shaft 3, as described above, is designed as a gear-like extension of the planet gear web 73 of the planetary gear set 7, whose rotational movement is almost completely converted into a ring gear (75) movement when the clutch 11 is open. At sufficiently high acceleration above a certain acceleration threshold, a braking effect of the centrifugal brake 13 is triggered. The braking torque of the centrifugal brake 13 is transmitted via the planetary gear set 7 through the planetary gear stages of the further gear set 107 back to the eccentric 103, thus braking its rotational movement and consequently the linear movement of the valve element 113. This prevents the valve element 113 from abruptly moving into the predetermined safety position (usually a closed position), thereby avoiding damage to the valve element 113.

[0048] Fig. Figure 3 shows another, alternative preferred embodiment of the actuator 102 according to the invention. The actuator 102 differs from the actuator 101 described above essentially in that the drive axis A of the actuator 1 is arranged parallel to the eccentric axis of rotation E. To bridge the radial distance between the drive axis A and the eccentric axis of rotation E, a spur gear 109 is rotatably mounted on the housing 137 of the actuator 102, transmitting torque between the output shaft 3. A second, further gear unit 107' of the eccentric 103 comprises, in addition to the stepped spur gear 109 for bridging the distance between the drive axis A and the eccentric axis of rotation E, a second stepped spur gear 119, which is rotatably mounted coaxially to the eccentric axis of rotation E about the eccentric bearing axis 121', which is fixed to the housing.The second gearbox 107' comprises, similar to the further gearbox 107 of the actuator 101 described above, a two-stage reduction planetary gearbox, the input stage of which is the stepped second spur gear 119.

[0049] The housing of the actuator 102 is essentially divided into two housing halves 135' and 137. Compared to the axial extension of the eccentric bearing axis 121' and the motor shaft 21, the axial extension of the first housing half 137 is significantly smaller than that of the second housing half 135'. The first housing half 137 can also be referred to as the housing cover. The second housing half 135' is referred to below as the housing shell. The housing shell 135' comprises two parallel chambers, one of which houses the actuator 1 with the electric motor 5, the clutch 11, the optional centrifugal brake 13, and the optional gearbox 7. The second chamber of the housing shell 135' houses the eccentric 103, the spring accumulator 105, the planetary gear stages of the additional gearbox 107, and the optional second spur gear 119.The eccentric bearing axis 121 extends in its axial direction E through the eccentric 103 and through the planetary gear stages of the further gearbox 107'. The bearing axis 121' is held at its two opposite ends in the housing halves 135', 137.

[0050] The function of the eccentric 103, also taking into account the spring accumulator 105 of the plunger 111 and the clutch 11 as well as the centrifugal brake 13, corresponds to the actuator 102 according to Fig. 3 essentially the function described above with regard to the actuator 101 according to Fig. 2. The two-stage planetary gear of the further gear 107, 107' also functions in essentially the same way in both versions.

[0051] In both actuators 101 and 102, the coupling 11 and the electric motor 5 are connected to each other in a rotationally fixed manner via a mounting section 35. This mounting section 35 can also serve to mount the actuator 1 in a rotationally fixed manner within a housing half 135 or 135'. For this purpose, the mounting section 35 can, for example, be designed as a flange for attachment to the housing half 135 or 135' of the actuator 101 or 102.

[0052] The features disclosed in the foregoing description, figures and claims can be important for the realization of the invention in its various embodiments, both individually and in any combination. Reference symbol list 1 actuator 3 Output shaft 5 electric motor 7 planetary gears 10 Electromagnet 11 electromagnetic clutch 12 rotating coupling part 13 Centrifugal brake 15 stationary coupling part 17 Brake pot 21 Motor shaft 23, 25 ball bearings 27 Hollow shaft 35 actuator housings 71 Sun wheel 73 Planetary gear bridge 75 Ring gear 76 planetary gear 101, 102 Actuator 103 eccentrics 105 spring storage units 107, 107' further gearbox 109, 119 Spur gear 111 pestles 113 Control valve 121, 121' Eccentric bearing axle 135, 135' Drive housing 137 Case cover 139 eccentric housings A motor rotary axis E eccentric rotary axis

Claims

[1] Electric actuator (1) for an actuator with safety actuating function for positioning an actuator, such as a valve element, of a process plant, comprising an electric motor (5) for providing a torque for actuating the actuator, wherein the electric motor (5) has a motor shaft (21) for delivering the torque, an output shaft (3) for transmitting the torque from the electric motor to the actuator, and a coupling (11) for providing and / or interrupting a torque-transmitting connection between the motor shaft (21) and the output shaft (3), characterized by , that the output shaft (3), the motor shaft (21) and the clutch (11) are arranged coaxially to each other, and that the electric actuator (1) further comprises: a planetary gear set (7) arranged coaxially to the output shaft (3) for transmitting the torque from the electric motor (5) to the output shaft (3), wherein the motor shaft (21) provides the torque from the electric motor (5) to the gear set, and that the motor shaft (21) extends in its axial direction (A) from the gearbox to the electric motor (5) through the clutch (11) and through a centrifugal brake (13) and / or through a ring gear (75). [2] Electric actuator (1) according to claim 1 characterized by that the transmission has exactly one gear stage, which is designed as a reduction gear stage. [3] Electric actuator (1) according to claim 1 or 2 characterized by, that the planetary gear (7) is designed to reduce the gear ratio, wherein the output shaft (3) is realized at least partially as a planet carrier (73) of the gear or a planet carrier (73) is directly connected to the output shaft (3) in a torque-transmitting manner and / or wherein the motor shaft (21) is connected to the sun gear (71) of the gear in a rotationally fixed manner. [4] Electric actuator (1) according to one of claims 1, 2 or 3, characterized by , that a gear component of the planetary gear (7) is rotationally fixed relative to a rotatable part (12) of the clutch (11). [5] Electric actuator (1) according to any one of the preceding claims, characterized by , that the electric motor (5) is designed with a rated speed of at least 200 rpm, at least 500 rpm, at least 1000 rpm, at least 3000 rpm or at least 6000 rpm and / or that the direction of rotation of the electric motor (5) is reversible. [6] Electric actuator (1) according to any one of the preceding claims, characterized by , that a centrifugal brake (13) arranged coaxially to the output shaft (3) is connected to the transmission and / or the clutch (11) in a rotationally fixed manner, wherein the centrifugal brake (13) is connected to a transmission component of the transmission in a rotationally fixed manner. [7] Electric actuator (1) according to any one of the preceding claims, characterized by , that the motor shaft (21) is axially section-wise surrounded in the radial direction by a hollow shaft (27) which is rotatably mounted relative to the motor shaft (21) and / or on the motor shaft (21) with a sliding bearing, wherein the hollow shaft (27) is non-rotatably connected to a transmission component, , a centrifugal brake (13) and / or the rotatable part (12) of the clutch (11). [8] Electric actuator (1) according to any one of the preceding claims, characterized by, that the motor shaft (21) extends through a stator and / or a rotor of the electric motor (5), wherein the motor shaft (21) is rotatably mounted on both sides of the electric motor (5) in the axial direction with a rolling bearing on each side. [9] Actuator (101, 102) with safety actuating function, comprising an actuator, such as a valve element (113), for adjusting a process fluid flow of a process engineering plant, and an electric actuator (1) according to one of the preceding claims, comprising an eccentric (103) or spindle drive actuated by the output shaft (3) for linearly actuating the actuator. [10] Actuator (101, 102) according to claim 9, characterized by, that the actuator (101, 102) comprises a spring accumulator (105), namely a rotary spring accumulator, for moving the actuator into a safety position when the clutch (11) and / or the electric motor (5) is de-energized, wherein the spring accumulator (105) is arranged coaxially to the output shaft (3) and / or is arranged on the output side relative to the gearbox.

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