Actuator

Abstract

An actuator includes a motor assembly, a drive coupling assembly, and an actuator shaft. The motor assembly includes a motor housing having a cover and a base; an electric motor including an outer stator and an inner rotor; and a hollow output shaft coaxially connected with the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft. The drive coupling assembly includes a drive coupling housing containing a drive coupling, where the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling. An actuator shaft extends through the hollow output shaft and the inner rotor and engages the drive coupling such that rotation of the drive coupling through the hollow output shaft causes axial movement of the actuator shaft.

Description

[0001] This application is a divisional application of a Chinese national stage patent application with the application number 201980085021.9, which entered the Chinese national stage on June 21, 2021, for the PCT application with the international application number PCT / GB2019 / 053563 and the international filing date of December 16, 2019, and the invention title of "Actuator". Technical Field

[0002] The present invention relates to actuators such as valve actuators, and in particular to valve actuators operated by an electric motor. The present invention also relates to a system including a valve and an actuator, and an electric motor for such an actuator or system. Background Art

[0003] Electric valve actuators are control devices widely used in many industries including the process control industry for managing fluid and gas flow. Such actuators use an electric motor to convert electrical energy into mechanical motion to operate a fluid control valve.

[0004] When an electric valve actuator is used to operate a heavy industrial valve, a large torque may need to be applied to the valve. Since an electric motor capable of directly providing sufficient torque for such an operation may be very large, an electric motor with a lower torque can be used together with a gear transmission system (usually a worm gear), which is configured to increase the torque while reducing the output speed. Using such gears to transmit power from the electric motor to the valve increases mechanical complexity due to more moving parts. Therefore, a gear electric valve actuator may have reduced efficiency due to frictional losses, reduced accuracy and increased noise due to gear backlash, wear / lubrication / maintenance problems. The transmission system also occupies space in the actuator housing, resulting in a larger overall size.

[0005] Therefore, there is a need for a valve actuator including an electric motor that can be compactly assembled within a valve actuator housing and can provide sufficient torque to operate a heavy industrial valve without a large gear transmission system.

[0006] EP 3026373 A1 (TGK CO), EP 0364308 A2 (SNEDDON) and GB862324A (ATOMIC ENERGY AUTHORITY UK) disclose motor-operated valve actuators. Summary of the Invention

[0007] One aspect of the present invention provides an actuator, which includes a motor assembly, a drive coupling assembly, and an actuator shaft. The motor assembly includes a motor housing having a cover and a base; an electric motor, within the motor housing, including an outer stator and an inner rotor; and a hollow output shaft coaxially connected to the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft. The drive coupling assembly includes a drive coupling housing containing a drive coupling, wherein the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling; and wherein the drive coupling assembly is connected to the base of the motor housing. The actuator shaft engages the drive coupling such that rotation of the drive coupling through the hollow output shaft causes the actuator shaft to move.

[0008] The drive coupling assembly can be outside the motor housing. For example, the electric motor can be on one side of the motor housing base (inside the motor housing), while the drive coupling assembly can be on the other side of the motor housing base (outside the motor housing).

[0009] The connection between the drive coupling assembly and the motor housing can be releasable. For example, the drive coupling assembly and the motor housing can be connected to each other by at least one removable fixing element (such as a bolt).

[0010] The hollow output shaft can directly engage the drive coupling or can engage the drive coupling through a gear arrangement. The gear arrangement can include a gearbox, and the drive coupling assembly can be connected to the base of the motor housing through the gearbox. The gearbox can contain a planetary gear arrangement that includes a sun gear and planetary gears mounted on a rotating gear carrier, wherein the sun gear is hollow and coaxial with the hollow output shaft and the actuator shaft, and the rotation of the hollow output shaft can be transmitted to the actuator shaft through the rotation of the rotating gear carrier. The planetary gear arrangement can be a multi-stage planetary gear arrangement.

[0011] The drive coupling can include an anti-backdrive coupling.

[0012] The actuator shaft can extend through the hollow output shaft and the inner rotor. In this case, rotation of the drive coupling causes the actuator shaft to move axially.

[0013] Rotation of the inner rotor can be transferred to the drive coupling by the engagement of at least one axially extending lug and at least one corresponding notch formed in corresponding portions of the hollow output shaft and the drive coupling. Such engagement allows the motor assembly to be easily removed from the drive coupling assembly and the actuator shaft (e.g., for maintenance), because once the connection between the drive coupling assembly and the motor housing is released, the lug and notch can be disengaged simply by axially moving the motor assembly away from the drive coupling assembly. Additionally, this can be done without affecting the position of the actuator shaft, since the actuator shaft and the motor assembly are only indirectly connected through the drive coupling assembly.

[0014] The hollow output shaft can be mounted within the inner rotor and extend through the inner rotor.

[0015] The cover and base of the motor housing can define an inner tube and the inner rotor can be mounted on bearings on the tube.

[0016] The cover and base of the motor housing can be fixed in a spaced arrangement by positioning members extending between the peripheral regions of the cover and the base of the motor housing. In this case, bearings can be provided in the cover and base of the motor housing to mount the inner rotor for rotation. Additionally, the upper portion of the hollow output shaft can have an outer flange, and the hollow output shaft can be mounted within the inner rotor through the flange, with the upper surface of the flange engaging the bearing at the upper portion of the inner rotor.

[0017] The cover of the motor housing can extend around the stator and rotor from the base of the motor housing.

[0018] The cover of the motor housing can have an opening area, and the motor housing further includes a removable cover that can be fixed to the outer surface of the cover of the motor housing to close the opening area.

[0019] The actuator can include an actuator housing within which actuator components are fixed and which defines the motor housing, and the outer stator and inner rotor are directly mounted on the motor housing. Optionally, the actuator housing can define a drive coupling housing, and for example, the actuator housing can surround the motor assembly.

[0020] The actuator can include a valve housing within which valve components are fixed, and the valve housing defines the drive coupling housing.

[0021] The drive coupling can be an internally threaded drive nut, ball screw nut, or roller screw nut that engages with a thread on the exterior of the actuator shaft. The drive coupling can include an anti-backdrive coupling.

[0022] The outer stator, inner rotor, hollow output shaft, drive coupling, and actuator shaft can be coaxially arranged. For example, the inner rotor, hollow output shaft, and drive coupling can have a common axis of rotation.

[0023] The outer stator may include a stator body having a series of inwardly projecting teeth, with windings disposed around each tooth. In this case, the sides of the stator teeth may be substantially straight along the entire length of the teeth. An electric motor having this feature may also be used in other applications.

[0024] The outer stator may be fixed in place by engaging with the cover and the base of the motor housing.

[0025] The drive coupling housing may be fixed relative to the lower surface of the lower part. The actuator may also include a bearing assembly located between the drive coupling and the drive coupling housing to allow the drive coupling to rotate relative to the drive coupling housing.

[0026] Another aspect of the present invention provides a system that includes an actuator according to the first aspect and a valve connected to the actuator.

[0027] The actuator shaft may be directly connected to the valve.

[0028] Another aspect of the present invention provides a system that includes an actuator according to the first aspect, wherein the actuator shaft is a threaded valve stem that includes a valve at its lower end.

[0029] Another aspect of the present invention provides an electric motor for use in the actuator or system as defined above, which includes an outer stator and an inner rotor, wherein the outer stator includes a stator body having a series of inwardly projecting teeth, with windings disposed around each tooth; and wherein the sides of the stator teeth are substantially straight along the entire length of the teeth.

[0030] Further variations are disclosed in the following description. Description of the Drawings

[0031] Figure 1 A partial cross-sectional view of an electric valve actuator is shown.

[0032] Figure 2 An exploded view of the actuator system is shown.

[0033] Figure 3 Shows Figure 2 A cross-sectional view of the assembled actuator system shown in

[0034] Figure 4 A cross-sectional view of a second actuator system is shown.

[0035] Figure 5 A cross-sectional perspective view of the second actuator system is shown at an angle.

[0036] Figure 6 The exterior of the second actuator system is shown.

[0037] Figure 7A cross-sectional view of a second actuation system in a partially disassembled configuration is shown.

[0038] Figure 8 The exterior of a second actuation system in a partially disassembled configuration is shown.

[0039] Figure 9 Another valve actuation system including a planetary gear device is shown.

[0040] Figure 10 A cross-sectional view of an electric motor designed for use with an actuation system is shown. Detailed Description

[0041] Figure 1 A partial cross-sectional view of an electric valve actuator 1 is shown, which includes an electric motor 2 (e.g., a brushless DC electric motor or an AC induction motor) for the electric operation of a valve (not shown); a transmission system 3 that connects the motor 2 to the valve (e.g., via a worm gear drive); a junction box 4 for power and data signal connections; an actuator control unit 5 for processing command signals and actuator signals to control actuator operation; a position control unit 6 connected to the transmission system; and a display 7 and local controls 8 for locally viewing and configuring the operation of the actuator 1. A handwheel 8 for manually operating the valve in an emergency situation (e.g., when the electric motor 2 fails or there is no available main power) may also be provided.

[0042] Figure 2 A exploded view of an actuation system 10 is shown, which can be used to replace the electric motor 2 and the transmission system 3 as described above with respect to Figure 1 The actuation system 10 can be used to provide a compact electric valve actuator that is capable of providing sufficient torque to operate heavy-duty industrial valves without a large transmission system / gear. Figure 2 Is a simplified illustration of the actuation system 10, with components such as electronics, PCBs, and wires omitted for clarity.

[0043] The actuation system 10 includes an electric motor, such as a brushless DC motor or a switched reluctance motor, including an outer stator 11 and an inner rotor 12; a motor housing 20; a hollow output shaft 30; a drive coupling 13 that is contained within a drive coupling housing 15; and an actuator shaft 14. As Figure 3 shown, all of these components are arranged on a common central axis, which is also the axis of rotation of the inner rotor 12, the hollow output shaft 30, and the drive coupling 13.

[0044] The inner rotor 12 is hollow and has a central, axially extending bore. As Figure 3As shown, the inner rotor 12 is substantially contained within the outer stator 11 such that the inner surface of the stator 11 surrounds the outer surface of the inner rotor 12.

[0045] Both the outer stator 11 and the inner rotor 12 are mounted within a generally circular motor housing 20 through which the system 10 can be located within an actuator housing. The motor housing 20 includes a base 23, a cover 22, and a shroud 21, each having a central aperture. A drive coupling housing 15 is located on the lower surface of the base 23 (i.e., the outer surface of the base 23 / the surface of the base 23 outside of the motor enclosed space of the motor housing 20). The cover 22 is fixedly spaced from the base 23 by positioning members 25 between the peripheral regions of the cover 22 and the base 23 such that the stator 11 and the rotor 12 are held in place within the motor housing 20. The cover 22 has an opening area 26 and the shroud 21 is removably fixed to the upper surface of the cover 22 (i.e., the outer surface of the cover 22 / the surface of the cover 22 outside of the motor enclosed space of the motor housing 20) so as to close the opening area 26.

[0046] The positioning members 25 can include threaded rods and nuts, the threaded rods extending through clearance counterbores in the cover 22 and the base 23 of the motor housing.

[0047] The shroud 21 and / or the cover 22 of the motor housing 20 can provide a means for attaching components (such as electronic components and cables) to the motor housing 20.

[0048] Bearings 27, 28 are provided in the cover 22 and the base 23 of the motor housing 20 to enable the inner rotor 12 to rotate within the motor housing 20.

[0049] Optionally, the electric motors 11, 12 can be mounted directly to the actuator housing rather than within the motor housing 20 described above, in which case bearings will be provided in the actuator housing to enable the inner rotor 12 to rotate within the actuator housing. Additionally, the stator 11 will be fixed to the actuator housing by means such as heat shrink, adhesion, or mechanical keying to prevent the stator 11 from rotating within the actuator housing.

[0050] The hollow output shaft 30 includes a hollow cylinder having an outer flange 31 that projects radially from the outer surface in its upper end region. The hollow output shaft 30 is mounted within the inner rotor 12 by a fixing means (such as bolts) between the flange 31 and the inner rotor 12 such that the hollow output shaft 30 rotates with the inner rotor 12. The upper surface of the flange 31 engages a bearing 27 in the upper part of the housing (such as the upper part 22 or the upper part of the actuator housing). The lower end of the rotor 12 engages a bearing 28 in the lower part of the housing (such as the base 23 or the lower part of the actuator housing). The lower end of the shaft 30 passes through the central aperture of the lower part of the housing (such as the base 23 or the lower part of the actuator housing).

[0051] The drive coupling housing 15 is fixed to the lower part of the motor housing 20 (i.e., the base 23) or the actuator housing around the central hole. The drive coupling 13 is mounted for rotation in a bearing 16 in the drive coupling housing 15. The hollow output shaft 30 has axially extending lugs 32a, 32b at one end (i.e., its lower end). The lugs 32a, 32b engage in corresponding notches 33a, 33b provided at one end of the drive coupling 13 such that the drive coupling 13 can rotate with the hollow output shaft 30 in the bearing 16. Optionally, axially extending lugs may be provided at one end of the drive coupling 13 and corresponding notches may be provided at one end of the hollow output shaft 30. Thus, the rotation of the inner rotor 12 is transmitted to the drive coupling 13 through the engagement of the lugs and notches formed in the corresponding parts of the hollow output shaft 30 and the drive coupling 13.

[0052] The drive coupling 13 includes a drive nut having an internally threaded hole. The valve actuator shaft 14 extends through the hollow output shaft 30 and the drive coupling 13 and has an external thread that engages the internal thread of the drive coupling 13. This engagement converts the rotation of the drive coupling 13 relative to the actuator shaft 14 into linear movement of the shaft 14. Thus, actuation of the rotor 12 causes the actuator shaft 14 to move axially. If a valve is provided at one end (i.e., the lower end) of the actuator shaft 14 (e.g., where the actuator shaft is directly connected to the valve or where the actuator shaft is a threaded valve stem that includes a valve at its lower end), the axial movement of the actuator shaft 14 in turn operates the valve, causing the electric motors 11, 12 to act directly on the valve. The thread pitch on the drive coupling and the shaft 14 determines the degree of axial movement of the shaft per revolution of the rotor 12.

[0053] As an alternative to the above drive nut, the drive coupling 13 can be a recirculating ball screw nut or a roller screw nut. Moreover, the actuation system 10 can include an anti-backdrive coupling.

[0054] As with Figure 1 the actuator, a handwheel (not shown) can be provided for manually operating the valve in an emergency (e.g., when the electric motor fails or when there is no main power available).

[0055] Figures 4 - 8 An alternative second actuation system 100 is shown, which can also be used in place of the system described above with respect to Figures 2 - 3 the system. Figures 4 - 8 is a simplified illustration of the second actuation system 100, with components such as electronics, PCBs, and wires omitted for clarity.

[0056] The second actuation system 100 includes an electric motor, which includes an outer stator 111 and an inner rotor 112; a motor housing 120; a hollow output shaft 130; a drive coupling 113, which is contained within a drive coupling housing 115; and an actuator shaft 114, all of which are generally constructed in the same manner as the Figures 2 - 3 system shown therein.

[0057] In the second system, a cover 122 extends from the base 123 of the motor housing around the stator 111 and rotor 112, defining an inner tube 122a such that the stator 111 and rotor 112 are fixed in place within the motor housing 120. The inner rotor 112 is mounted on bearings 127, 128 on the inner tube 122a to enable the inner rotor 112 to rotate within the motor housing 120. The inner rotor 112 is also mounted on a seal 124 on the inner tube 122a and a seal 129 in a central hole in the lower part of the housing (e.g., the base 123 or the lower part of the actuator housing) such that components of the electric motor 111, 112 (e.g., the stator windings of the electric motor, motor drive electronics, and IGBT modules) are sealed, e.g., to prevent a potentially explosive environment. Additionally, the cover 122 may have an opening area, and the motor housing 120 may further include a cover that is removably fixed to the upper surface of the cover 122 (i.e., the outer surface of the cover 122 / the surface of the cover 122 outside the motor enclosure space of the motor housing 120) to close the opening area 26. At least one seal may be provided between the cover and the opening area.

[0058] The cover 122 and / or the cover of the motor housing 120 may provide a means for attaching components (e.g., electronic components and cables) to the motor housing 120.

[0059] Similar to Figures 2 - 3 the system shown therein, the hollow output shaft 130 has axially extending lugs 132a, 132b at one end (i.e., its lower end / the end extending through the central hole in the lower part of the housing (e.g., the base 123 or the lower part of the actuator housing)), which engage corresponding notches 133a, 133b provided at one end of the drive coupling (see Figure 8 ).

[0060] In the above system, the drive coupling assembly is connected to the base of the motor housing. Since the electric motor is located on one side of the base of the motor housing (i.e., inside the motor housing), and the drive coupling assembly is located on the other side of the base of the motor housing (i.e., outside the motor housing), the drive coupling assembly is also outside the motor housing. When the drive coupling assembly and the motor housing are connected to each other by at least one removable fixing element, the connection between the drive coupling assembly and the motor housing is releasable. For example, in the compact actuation systems 10 and 100, the removable fixing elements include bolts 41, 141 that extend through clearance holes provided in flanges 42, 142 of the drive coupling housings 15, 115 and engage threaded holes in the bases 23, 123 of the motor housing.

[0061] The engagement between the lugs and the corresponding notches formed in the respective portions of the drive coupling (i.e., drive coupling 13 or drive coupling 113) and the hollow output shaft (i.e., shaft 30 or shaft 130) allows the motor assembly to be easily removed from the drive coupling assembly and the actuator shaft (e.g., for maintenance), as Figure 7 and Figure 8 shown, because once the connection between the drive coupling assembly and the motor housing is released, the lugs and notches can be disengaged simply by axially moving the motor assembly away from the drive coupling assembly. Additionally, this can be done without affecting the position of the actuator shaft (i.e., shaft 14 or shaft 114) because the actuator shaft is indirectly connected to the motor assembly through the drive coupling assembly (i.e., the engagement between the lugs and notches). If a valve is provided at one end of the actuator shaft (i.e., the lower end of the actuator shaft), this means that the motor assembly can be safely removed for repair or replacement without having to stop using the valve.

[0062] The drive coupling housing (i.e., drive coupling housing 15 or drive coupling housing 115) can be connected to the valve housing in which the valve components are fixed. Alternatively, the valve housing can define the drive coupling housing (i.e., drive coupling housing 15 or drive coupling housing 115).

[0063] In the case where the electric motor used with the compact actuation systems 10 and 100 is a brushless DC motor, drive electronics and an IGBT (Insulated Gate Bipolar Transistor) module can be used to switch current to the motor windings using pulse width modulation (PWM) control. The IGBT module can be arranged radially around the motor end windings and electrically connected to the motor end winding terminations.

[0064] (or similar materials known in the art) can be used to substantially or completely encapsulate the components of an electric motor used with the compact actuation systems 10 and 100 (e.g., the stator windings of the electric motor, the motor drive electronics, and the IGBT modules at the ends of the motor end windings). For example, this can be achieved by using the motor housing 120 as a mold and pouring molten (or similar materials) into the opening of the motor housing 120 (e.g., the opening provided between the inner rotor 112 and the base of the motor housing 123) and allowing (or similar materials) to cure. Encapsulating the components of the electric motor in (or similar materials) can make the compact actuation system (i.e., the compact actuation system 10 or 100) explosion-proof because (or similar materials) can be used as a barrier between a potentially explosive environment and the encapsulated components (e.g., the motor windings and drive electronics) that may become a source of spark ignition.

[0065] In Figures 2 - 8 the illustrated embodiment, the hollow output shafts 30, 130 are directly joined to the drive couplings 13, 113. In this case, the maximum torque that can be applied to the actuator shaft will depend on the size of the motor. For high-torque applications, the motor size required for direct drive may be too large to be practical. In this case, a gear device can be inserted between the motor and the drive coupling. Figure 9 An embodiment of the device is shown that includes a gearbox 350 that houses a planetary gear device that includes a sun gear 352 and a series of planetary gears 354. The sun gear 352 is hollow and is concentrically mounted in the drive coupling housing 315 together with the hollow output shaft 330 and the drive coupling 313 (and thus with the actuator shaft, not shown). The sun gear 352 is mounted on a sun gear carrier 356 that is mounted in bearings in the upper part of the gearbox 350 and has a notch 333 to receive a lug 332 on the end of the hollow output shaft 330. The planetary gears 354 are mounted on a planetary gear carrier 358 that rotates with the planetary gears 354 and transfers rotation to the drive coupling 313 via a drive lug 360. The motor and the gearbox can be separate units such that the motor can be removed from the gearbox. Similarly, the gearbox can be removed from the drive coupling, leaving the valve in place, as described above.

[0066] Although Figure 9 a single-stage planetary gear system is shown, a multi-stage planetary gear system can also be used. For example, the planetary gear carrier can be connected to the hollow sun gear of a subsequent planetary gear stage. Two or more subsequent stages can be used.

[0067] As an alternative to the planetary gearbox disclosed above, the gearbox can be a spur gear type or bevel gear type with a hollow output shaft to allow the actuator shaft to rise through the output gear of the gearbox. In the case of using such a spur or bevel gear gearbox, the actuator shaft may not rise through the hollow output shaft of the motor since the motor rotation axis may no longer be concentric with the gearbox output axis.

[0068] The above-described linear motor device, or a linear motor incorporated into a gearbox, can be used in conjunction with an anti-backdrive coupling to operate a quarter-turn valve, such as a ball valve or butterfly valve. This type of quarter-turn valve does not have a rising valve stem or actuator shaft. The anti-backdrive coupling may remain attached to the valve to hold the position of the valve while the motor is removed in a similar manner as described above for maintenance or replacement.

[0069] Figure 10 A cross-sectional view of electric motors 211, 212 that can be used with the compact actuator systems 10 and 100 described above is shown. The stator 211 consists of an outer stator body 213 having a series of inwardly projecting stator teeth 214. The sides of the stator teeth 214 are substantially straight along the entire length of each tooth. It has previously been proposed to provide a laterally extending portion or tip at the end of each tooth (i.e., the sides extend laterally towards adjacent teeth at the end). This is done to reduce the high flux density levels in the stator that cause excessive heat generation during use. In practice, the outer stator 211 does not have stator tooth tips. In applications such as the valve actuator described above, the motor can have a low rotational output speed such that iron losses and heat generation are not a problem. Additionally, the motor will operate, for example, at a 25% duty cycle rather than continuous rated operation, and the outer stator 211 can be relatively large in size relative to the motor output power, thus having a large thermal mass that helps to dissipate any heat generated.

[0070] The absence of stator tooth tips on the outer stator 211 can significantly simplify the coil assembly process since pre-wound concentrated "coil groups" can be assembled onto the stator 211 by simply sliding them onto the stator teeth rather than having to wind the coils in place onto the stator 211. The process of maintaining such a stator 211 is also simplified since the "coil groups" can be easily removed from the stator teeth by simply sliding the "coil groups" off the stator teeth. Additionally, it simplifies the design of the outer stator 211, making it easier to manufacture. Motors having these features, such as brushless DC motors or switched reluctance motors, can also be used in other applications in addition to the valve actuator disclosed above. The present invention extends to such uses.

[0071] Further changes can be made within the scope of the present invention.

[0072] Various examples can be defined in accordance with one or more of the following clauses:

[0073] Clause 1. An actuator comprising a motor assembly, a drive coupling assembly, and an actuator shaft; the motor assembly includes a motor housing having a cover and a base; an electric motor within the motor housing, including an outer stator and an inner rotor; and a hollow output shaft coaxially connected to the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft; the drive coupling assembly is connected to the base of the motor housing, the drive coupling assembly includes a drive coupling housing containing a drive coupling, wherein the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling; the actuator shaft engages the drive coupling such that rotation of the drive coupling through the hollow output shaft causes movement of the actuator shaft.

[0074] Clause 2. The actuator according to clause 1, wherein the drive coupling assembly is external to the motor housing.

[0075] Clause 3. The actuator according to clause 1 or 2, wherein the connection between the drive coupling assembly and the motor housing is releasable such that the motor housing can be removed from and reattached to the drive coupling assembly.

[0076] Clause 4. The actuator according to clause 1, 2, or 3, wherein the hollow output shaft directly engages the drive coupling.

[0077] Clause 5. The actuator according to clause 1, 2, or 3, wherein the hollow output shaft engages the drive coupling through a gear arrangement.

[0078] Clause 6. The actuator according to clause 5, wherein the gear arrangement includes a gearbox, and the drive coupling assembly is connected to the base of the motor housing through the gearbox.

[0079] Clause 7. The actuator according to clause 6, wherein the gearbox contains a planetary gear arrangement, the planetary gear arrangement includes a sun gear and planetary gears mounted on a rotating gear carrier, wherein the sun gear is hollow and coaxial with the hollow output shaft and the actuator shaft, and rotation of the hollow output shaft is transmitted to the actuator shaft through rotation of the rotating gear carrier.

[0080] Clause 8. The actuator according to clause 7, wherein the planetary gear arrangement is a multi-stage planetary gear arrangement.

[0081] Clause 9. The actuator according to clause 6 or 7, wherein the drive coupling includes an anti-backdrive coupling.

[0082] Clause 10. An actuator as described in any of the preceding clauses, wherein the actuator shaft extends through the hollow output shaft and the inner rotor.

[0083] Clause 11. An actuator as described in Clause 10, wherein rotation of the drive coupling causes axial movement of the actuator shaft.

[0084] Clause 12. An actuator as described in any of the preceding clauses, wherein rotation of the inner rotor is transmitted to the drive coupling by engagement of at least one axially extending lug and at least one corresponding notch formed in corresponding portions of the hollow output shaft and the drive coupling.

[0085] Clause 13. An actuator as described in any of the preceding clauses, wherein the cover of the motor housing extends from the base of the motor housing around the stator and the rotor.

[0086] Clause 14. An actuator as described in Clause 13, wherein the cover of the motor housing defines an inner tube and the inner rotor is mounted on a bearing on the tube.

[0087] Clause 15. An actuator as described in any of Clauses 1 - 12, wherein the cover and the base of the motor housing are fixed in a spaced arrangement by a positioning member extending between the outer peripheral regions of the cover and the base of the motor housing.

[0088] Clause 16. An actuator as described in Clause 15, wherein bearings are provided in the cover and the base of the motor housing for mounting the inner rotor for rotation.

[0089] Clause 17. An actuator as described in Clause 16, wherein the hollow output shaft has an outer flange in its upper region, the hollow output shaft is mounted within the inner rotor through the flange, and the upper surface of the flange engages a bearing in the upper portion of the housing.

[0090] Clause 18. An actuator as described in any of Clauses 15 - 17, wherein the hollow output shaft is mounted within the inner rotor and extends through the inner rotor.

[0091] Clause 19. An actuator as described in any of the preceding clauses, wherein the cover of the motor housing has an opening area, and the motor housing further includes a removable cover that can be fixed to the outer surface of the cover of the motor housing to close the opening area.

[0092] Clause 20. A system comprising:

[0093] An actuator as described in any of the preceding clauses, and

[0094] A valve connected to the actuator.

[0095] Clause 21. The system as described in Clause 20, wherein the actuator shaft is directly connected to the valve.

[0096] Clause 22. The actuator as described in any one of Clauses 1 - 19, wherein the outer stator includes a stator body having a series of inwardly projecting teeth, and windings are disposed around each tooth.

[0097] Clause 23. The actuator as described in Clause 18, wherein the sides of the stator teeth are substantially straight along the entire length of the teeth.

[0098] Clause 24. An electric motor for an actuator as described in Clause 1 or a system as described in Clause 20, having an outer stator and an inner rotor, wherein the outer stator includes a stator body having a series of inwardly projecting teeth, and windings are disposed around each tooth; and wherein the sides of the stator teeth are substantially straight along the entire length of the teeth.

Claims

1. An actuator, comprising: a motor assembly, comprising: a motor housing, comprising: a cover, and a base; an electric motor disposed within the motor housing, comprising: an outer stator, and an inner rotor; and a hollow output shaft mounted within and extending through the inner rotor and coaxially connected to the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft, wherein the hollow output shaft extends between the cover and the base; a drive coupling assembly connected to the base of the motor housing, the drive coupling assembly comprising a drive coupling housing containing a drive coupling, wherein the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling; and an actuator shaft extending through the hollow output shaft and engaging the drive coupling such that rotation of the drive coupling through the hollow output shaft causes axial movement of the actuator shaft; wherein the electric motor is located on one side within the motor housing of the base, and the drive coupling assembly is located on the other side outside the motor housing of the base; and wherein the connection between the drive coupling assembly and the base is releasable such that the motor housing can be removed from and reattached to the drive coupling assembly.

2. The actuator according to claim 1, wherein, the hollow output shaft directly engages the drive coupling.

3. The actuator according to claim 1, wherein, the hollow output shaft engages the drive coupling through a gear arrangement.

4. The actuator according to claim 3, wherein, the gear arrangement includes a gearbox, and the drive coupling assembly is connected to the base of the motor housing through the gearbox.

5. The actuator according to claim 4, wherein, the gearbox contains a planetary gear arrangement, the planetary gear arrangement includes a sun gear and planetary gears mounted on a rotating gear carrier, wherein the sun gear is hollow and coaxial with the hollow output shaft and the actuator shaft, and rotation of the hollow output shaft is transmitted to the actuator shaft through rotation of the rotating gear carrier.

6. The actuator according to claim 4, wherein, the drive coupling includes an anti-backdrive coupling.

7. The actuator according to claim 1, wherein, rotation of the inner rotor is transmitted to the drive coupling through engagement of at least one axially extending lug and at least one corresponding notch formed in corresponding portions of the hollow output shaft and the drive coupling.

8. The actuator according to claim 1, wherein, the hollow output shaft has an outer flange in its upper region, the hollow output shaft is mounted within the inner rotor through the flange, and an upper surface of the flange engages a bearing in an upper portion of the housing.

9. The actuator according to claim 1, wherein, the outer stator includes a stator body having a series of inwardly projecting teeth, with windings disposed around each tooth.

10. The actuator according to claim 9, wherein, The side surface of the stator tooth is substantially straight along the entire length of the tooth.

11. An actuator, comprising: A motor assembly, comprising: A motor housing, comprising: A cover, and A base; An electric motor, which is within the motor housing, comprising: An outer stator, and An inner rotor; and A hollow output shaft, which is coaxially connected to the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft; wherein the cover defines an inner tube; A drive coupling assembly, which is connected to the base of the motor housing, the drive coupling assembly comprising a drive coupling housing containing a drive coupling, wherein the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling; and An actuator shaft, the actuator shaft extending through the hollow output shaft and into the inner tube, and engaging the drive coupling such that rotation of the drive coupling through the hollow output shaft causes axial movement of the actuator shaft; wherein, the electric motor is located on one side within the motor housing of the base, and the drive coupling assembly is located on the other side outside the motor housing of the base; and wherein, the connection between the drive coupling assembly and the base is releasable such that the motor housing can be removed from and reattached to the drive coupling assembly.

12. The actuator according to claim 11, wherein, The hollow output shaft directly engages the drive coupling.

13. The actuator according to claim 11, wherein, The hollow output shaft engages the drive coupling through a gear device.

14. The actuator according to claim 13, wherein, The gear device includes a gearbox, and the drive coupling assembly is connected to the base of the motor housing through the gearbox.

15. The actuator according to claim 14, wherein, The gearbox contains a planetary gear device, the planetary gear device including a sun gear and planetary gears mounted on a rotating gear carrier, wherein the sun gear is hollow and coaxial with the hollow output shaft and the actuator shaft, and rotation of the hollow output shaft is transmitted to the actuator shaft through rotation of the rotating gear carrier.

16. The actuator according to claim 15, wherein, The planetary gear device is a multi-stage planetary gear device.

17. The actuator according to claim 14, wherein, The drive coupling includes an anti-backdrive coupling.

18. The actuator according to claim 11, wherein, The actuator shaft extends through the hollow output shaft and the inner rotor.

19. The actuator according to claim 11, wherein, The cover of the motor housing extends from the base of the motor housing around the stator and the rotor.

20. The actuator according to claim 11, wherein, The inner rotor is mounted on a bearing on the tube.

21. The actuator according to claim 11, wherein, The outer stator includes a stator body having a series of inwardly projecting teeth, with windings disposed around each tooth.

22. The actuator according to claim 21, wherein, The side surface of the stator tooth is substantially straight along the entire length of the tooth.

23. An actuator, comprising: A motor assembly, comprising: A motor housing, comprising: A cover, and A base; An electric motor, which is within the motor housing, comprising: An outer stator, and An inner rotor; and A hollow output shaft, which is coaxially connected to the inner rotor such that rotation of the inner rotor causes corresponding rotation of the hollow output shaft; A drive coupling assembly, which is connected to the base of the motor housing, the drive coupling assembly comprising a drive coupling housing containing a drive coupling, wherein the drive coupling engages the hollow output shaft such that rotation of the hollow output shaft causes corresponding rotation of the drive coupling; and An actuator shaft, the actuator shaft engaging the drive coupling such that rotation of the drive coupling through the hollow output shaft causes movement of the actuator shaft; wherein, the electric motor is located on one side within the motor housing of the base, and the drive coupling assembly is located on the other side outside the motor housing of the base; and wherein, the connection between the drive coupling assembly and the base is releasable such that the motor housing can be removed from and reattached to the drive coupling assembly; wherein, the actuator shaft extends through the hollow output shaft and the inner rotor, wherein rotation of the drive coupling causes axial movement of the actuator shaft; wherein, the cover and the base of the motor housing are fixed in a spaced arrangement by a positioning member extending between the cover and the peripheral region of the base of the motor housing; wherein, bearings are provided in the cover and the base of the motor housing for mounting the inner rotor for rotation; and wherein, the hollow output shaft has an outer flange in its upper region, the hollow output shaft is mounted within the inner rotor through the flange, and the upper surface of the flange engages a bearing in the upper part of the housing.

24. A system, comprising: An actuator according to any one of claims 1 to 23, and A valve connected to the actuator.

25. The system according to claim 24, wherein, The actuator shaft is directly connected to the valve.

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