Valve Actuators

Abstract

Disclosed herein is an actuator for a valve, comprising: a main shaft extending along an axial centerline of the main shaft and having an opening for receiving a valve stem; a first planetary gear system including a plurality of planetary gears, a first sun gear, and a first ring gear configured to rotate the main shaft about the axial centerline; and a motor for rotating the first planetary gear system, wherein the axial centerline of the main shaft coincides with the central axis of the sun gear of the planetary gear system.

Description

[Technical Field]

[0001] The present invention relates to actuators for valves, and more particularly to actuators having a central opening for receiving the valve stem of a gate valve, globe valve, or similar stem-operated object. [Background technology]

[0002] Valves are used to control the flow of fluids through pipes. They are usually operated manually, often by a handle, handwheel, or tap. Examples include the taps that turn the water on and off in showers and kitchen sinks.

[0003] However, there is a growing demand for actuators that allow valves to be operated from a remote location. This is useful, for example, when a ship's captain wants to adjust the ballast water on board but doesn't want to send a crew member into the engine room to open and close the valve. Hydraulic, pneumatic, and electric actuators are used for this purpose. For economic and environmental reasons, electric actuators are taking market share from hydraulic and pneumatic actuators.

[0004] An actuator typically consists of a motor and a gear system. To attach an actuator to a valve, the valve's handwheel is removed and the actuator's output shaft is attached to the valve shaft, which is called the valve spindle (butterfly valves and ball valves) or valve stem (globe valves and gate valves). The actuator is controlled by a microcontroller that receives commands via a signal cable and moves the motor to an open, closed, or intermediate position based on the received command. After operation, the controller reports completion or an error to the main system.

[0005] Valves come in many types and sizes. Some valves, such as butterfly valves and ball valves, are opened and closed by turning a valve spindle attached to the valve's moving part by a quarter turn. Other valves, such as globe valves and gate valves, have a stem that moves the valve's moving part up and down.

[0006] Both globe valves and gate valves typically have a stem, part of which is a threaded rod. The main difference between globe valves and gate valves relates to the design of the actuators for these valves: The stem of a globe valve typically rotates and moves up and down with the handwheel because the stem is threaded up and down via a nut that is part of the globe valve housing. The stem of a gate valve does not normally rotate. The handwheel is attached to a nut and thrust bearing, allowing the stem to be screwed up or down.

[0007] Because the spindle cannot move up and down, it is relatively easy to construct an electric actuator capable of operating butterfly and ball valves. An example of an actuator made for this purpose is the Eltorque QT250 actuator. This type is not suitable for globe or gate valves because the stem cannot move up and down. Disclosure of the latest technology

[0008] AUMA Riester GmbH & Co. KG manufactures an actuator capable of operating gate valves. Instead of the handwheel of a manual actuator, this actuator features a gear wheel driven by a worm wheel attached to the main shaft of an electric actuator. The motor and gearing of this type of actuator are positioned perpendicular to the stem.

[0009] In AUMA actuators, the stem nut is integrated into the actuator and is rotated by a gear system. To operate the gate valve, the stem nut is threaded, which translates the threaded valve stem when it rotates. This design does not result in a particularly compact valve actuator.

[0010] US2013140476A1 discloses a rotary valve adapter assembly that includes an adapter plate configured to be attached to a rotary valve body.

[0011] No. 20200052A1 discloses an induction valve drive mechanism that minimizes the overall volume of the induction valve drive mechanism and maintains a large output torque.

[0012] US2011275477A1 discloses a planetary gear reducer including a gear bracket having a central hole and first, second, and third positioning portions arranged parallel to the central hole.

[0013] US2007191177A1 discloses an automatic reduction ratio switching device that includes an input carrier, an output carrier, and an intermediate carrier.

[0014] US11118658B1 discloses a planetary gear system and method for a flow control actuator to provide a selectable torque and speed range.

[0015] CN114233916A discloses a marine intelligent small electric actuation mechanism comprising a motor, an output shaft, and a planetary gear unit. Summary of the Invention [Problem to be solved by the invention]

[0016] It is an object of the present invention to provide an actuator for a stemmed valve. The main problem that the present invention seeks to solve is how to manufacture a compact actuator for a globe valve, gate valve, or other stemmed valve. The advantage that the present invention has over the prior art is its compactness. [Means for solving the problem]

[0017] According to a first aspect of the present invention, there is provided an actuator for a valve, comprising: a main shaft extending along an axial centerline of the main shaft and having an opening for receiving a valve stem; a first planetary gear system including a plurality of planetary gears, a first sun gear, and a first ring gear configured to rotate the main shaft about its axial centerline; and a motor for rotating the first planetary gear system, wherein the axial centerline of the main shaft coincides with the axis of the sun gear of the planetary gear system.

[0018] The term valve actuator, as used herein, refers to a device that can be attached to a valve and that can open or close the valve when it receives a signal to open or close the valve.

[0019] References to the first planetary gear system being configured to rotate the main shaft about its axial centerline refer to the gear system being arranged to be coupled to the main shaft such that rotation or actuation of the planetary gear system rotates the main shaft. The coupling between the main shaft and the first planetary gear system does not necessarily have to be a direct coupling; there may be one or more additional gear systems or other mechanisms arranged to couple the first planetary gear system to the main shaft.

[0020] In some embodiments, the first sun gear and / or first ring gear are disposed within the actuator to surround the main shaft and its opening, and the valve stem can translate up and down along the axis of rotation of the first sun gear and / or first ring gear during use, with the shaft extending through a central opening in the first sun gear and / or ring gear. A bearing may be provided between the first sun gear and the main shaft to allow the first sun gear to rotate about the main shaft. The first ring gear may be manufactured as part of the actuator housing or as a separate component that is fixedly mounted within the housing.

[0021] In embodiments, the actuator comprises a hollow valve nut coupled to the main shaft, having a centerline coincident with the axial centerline of the main shaft, and including a throughbore through which the valve stem extends in use, the inner surface of the throughbore being shaped to interact with the valve stem to translate the valve stem along the axial centerline of the shaft upon rotation of the main shaft. The valve nut may be coupled to the main shaft for rotation therewith.

[0022] In embodiments, the valve nut is configured to be removably coupled to the main shaft. In this manner, the actuator can be easily adapted to function with various types / sizes of valves. In embodiments, the valve nut and main shaft are formed as one integral part. The valve nut and shaft may be machined from the same piece of material or molded as one piece, for example. The removably coupled may be by one or more screws that can be removed, for example, to replace the valve nut.

[0023] In an embodiment, the motor for rotating the first planetary gear system is an electric motor.

[0024] In one embodiment, the actuator includes a rotor frame rotatable about the axial centerline of the main shaft and coupled to the main shaft via a first planetary gear system. In another embodiment, the rotor frame is hollow and surrounds the main shaft, such that the main shaft extends through the center of the rotor frame. This reduces the actuator's footprint and provides a compact design.

[0025] In an embodiment, the actuator comprises a locking mechanism including a locking element movable between a locked position, in which the locking element presses against the main shaft or a locking ring fixed to the main shaft to prevent rotation of the main shaft, and an unlocked position, in which the main shaft can rotate relative to the locking element. In the unlocked position, the locking element does not press against the main shaft or locking ring, and movement of the main shaft is not impeded. A novel feature of this embodiment is that the locking mechanism locks relative to the main shaft and not the actuator housing. This again results in a particularly compact configuration of the overall mechanism.

[0026] In an embodiment, the locking mechanism comprises at least one unlocking pin coupled to the rotor frame for transitioning the locking element from a locked position to an unlocked position when the rotor frame rotates in either direction about the axial centerline of the main shaft. The use of an unlocking pin coupled to the rotor in this manner means that (intentional) rotation of the shaft by the rotor frame is not impeded, but rotation of the shaft by other means is prevented. Unwanted actuation of the valve is therefore prevented.

[0027] In some embodiments, the actuator includes a second planetary gear system including a second plurality of planetary gears, a second sun gear, and a second ring gear. The second planetary gear system couples the first planetary gear system to the main shaft and rotates the main shaft about its axial centerline. The second planetary gear system may have the same structure as the first planetary gear system and may be arranged to surround the shaft. The second planetary gear system is typically located above the first planetary gear system (away from the valve nut). In some embodiments, one or more planetary gear systems similar to the second planetary gear system may be added above the second planetary gear system as desired. Since each planetary gear system has a gear ratio and the system as a whole requires a specific total gear ratio, the number of planetary gear systems depends on specific design requirements, with the ratios of the individual systems multiplied to arrive at the total gear ratio. Therefore, adding one or more additional planetary gear systems increases the flexibility of the actuator in terms of achievable gear ratios.

[0028] In one embodiment, the actuator includes a first split ring gear system including a lower annular sun gear, a plurality of lower annular planetary gears, a plurality of upper annular planetary gears, an annular gear carrier, and an upper annular sun gear, where the upper annular sun gear is arranged to rotate with the main shaft. In one embodiment, the first ring gear system is configured to reverse the direction of rotation of the main shaft. This can be achieved by having a greater number of teeth on the upper annular sun gear than on the lower annular sun gear. Thus, in one embodiment, the number of teeth on the upper annular sun gear is greater than the number of teeth on the lower annular sun gear. The advantage of including this split ring gear system is that it potentially allows for a higher gear ratio than a planetary gear system, reducing the need for multiple planetary gear systems. Furthermore, if the ring gear system is also configured to reverse the direction of rotation, the emergency operating wheel rotates in the same direction as the valve stem or nut, making manual operation of the valve intuitive.

[0029] In one embodiment, the hollow valve nut includes an internal thread that allows the threaded valve stem to freely translate upward along the centerline of the main shaft as the main shaft rotates. This configuration is suitable for gate valves and other valves where it is undesirable for the stem to rotate as the main shaft translates axially. The internal thread refers to the thread located on the surface of the valve nut through-hole, which is the inward-facing surface toward the central axis.

[0030] In embodiments, the through hole in the valve nut has a non-circular cross-section, allowing a valve stem of a similar cross-section to freely translate upward along the centerline of the main shaft as the main shaft rotates. This configuration is suitable for globe valves and other valves that allow the stem to rotate as the main shaft translates axially. Furthermore, the cross-sectional shape of the valve nut hole may have a non-circular shape, such as a square, triangle, oval, rectangle, pentagon, hexagon, or other polygon.

[0031] In embodiments, the rotor frame is a frame for the rotor of an electric motor and is configured to rotate about the axial centerline of the main shaft. The motor including the rotor frame is configured to rotate the main shaft about its axial centerline. The rotor may include magnets, a squirrel cage, or other shapes that allow for interaction between the magnets and the stator. The stator may surround the rotor frame. In embodiments, the motor is configured to rotate the main shaft by transmitting torque through the bottom emergence shaft and the rotor frame to rotate the main shaft. In this configuration, the motor may be an "off-the-shelf" electric, hydraulic, or pneumatic motor, since it is mounted outside the actuator housing.

[0032] In an embodiment, the actuator includes an encoder comprising an encoder gear arrangement attached to the main shaft and configured to count the number of revolutions of the main shaft. The encoder gear arrangement may rotate the encoder shaft, possibly via a set of encoder gears, so that the encoder shaft rotates once for every integral number of revolutions of the main shaft (typically 2 or more, preferably 15 to 40 revolutions, most preferably 30 revolutions). Counting the number of revolutions of the main shaft allows for monitoring of the valve position. The relative number of revolutions may be specifically adjusted as desired.

[0033] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings: [Brief explanation of the drawings]

[0034] [Figure 1] 1 shows a cross-sectional view of the entire actuator and an isometric view from above and below. [Figure 2] 1 shows the first assembly step of attaching the bottom of the actuator and the first planetary gear system. [Figure 3] 10 shows a second assembly step for installing the second planetary gear system. [Figure 4] 10 shows the third assembly step of installing the split ring gear. [Figure 5] 4 shows the fourth assembly step of installing the automatic locking mechanism. [Figure 6] 10 shows a fifth assembly step of attaching the rotor and stator of the electric motor for moving the actuator. [Figure 7] The sixth assembly step is shown, where the emergency handle and encoder gear unit are attached. In the illustration, most of the parts are hidden, so the plate on which these parts are normally attached is hidden. [Figure 8] Same as Figure 7, but without hidden parts. [Figure 9] The main shaft is shown. [Figure 10]1 shows a first sun gear for a first planetary gear system. [Figure 11] 1 shows a carrier for planetary gears in a multi-stage planetary gear system. [Figure 12] FIG. 1 shows a cross section through an upper planetary gear of a multi-stage planetary gear system. [Figure 13] 2 shows a cross-sectional view through the automatic locking mechanism shown in FIG. 1. [Figure 14] The rotor in the motor is shown. [Figure 15] Shows the emergency mechanism separated into two parts. DETAILED DESCRIPTION OF THE INVENTION

[0035] Figures 1-8 include cross-sectional views and at least one isometric view of the same assembly step, with the remaining figures showing important or partially hidden components in Figures 1-8.

[0036] The lower part of Figure 1 shows a valve nut (40) suitable for operating a gate valve. Because the valve nut (40) moves the gate valve stem up and down, it must be machined to fit the stem's threads. The valve nut can be secured to the main shaft (2) with a bolt (47), making it easy to replace. If the actuator operates a globe valve, the threads (40A) of the valve nut (40) are replaced with a hole having a noncircular cross-section. The hole may have the same dimensions as the opening (51) extending axially through the main shaft (2). The cross-section of the hole may be any noncircular shape, such as a square, triangle, oval, rectangle, pentagon, or hexagon. Shapes with three or more corners are preferred to help prevent slippage. A particularly advantageous shape for the cross-section of the valve nut opening is a hexagon. If the actuator is intended only for operating a globe valve, the cross-section of the central opening of the valve nut (40) and the cross-section of the valve stem should preferably have the same shape and be properly matched. If the actuator is intended to operate only gate valves, the opening (51) in the main shaft (2) can be the same size and shape as the central opening in the valve nut (40), or it can be replaced with a round opening (51), which is much easier to machine. Figure 1 shows the hexagonal opening (51) in the main shaft (2), which is large enough to accept a threaded stem when operating a gate valve and the same size as the valve nut hole when operating a globe valve, allowing the actuator to operate both globe and gate valves with only minor adjustments. A seal (39) at the bottom of the main shaft prevents water and debris from entering the actuator. The valve nut (40) and main shaft (2) rotate within the actuator base (1). The actuator base (1) has a threaded hole (1A) to attach the actuator to the valve. Bearings (43, 44) ensure smooth rotation of the main shaft. Any suitable coupling means can be used to couple the valve nut to the stem. It is also possible to configure the valve nut (40) and the main shaft (2) as a single component.The advantage of this is that there are fewer parts in the actuator and the bottom seal 39 can be the same diameter as the top seal 41. The disadvantage is that the actuator only fits one type of valve, as both the stem diameter and stem thread size must match the valve type.

[0037] Figure 2 shows the first assembly step. The first ring gear (5) is placed on the actuator bottom (1). The first ring gear (5) and actuator bottom (1) can be manufactured as one piece, but are shown here as two pieces for ease of manufacturing. Inside the ring gear (5) is the first planetary gear (4) with bearings (4A) and shafts (4B). The shafts are pressed into holes (2B) in the main shaft (2) during a press pass. These holes (2B) are only visible in Figure 9. The same goes for the bearing passages (2A). In the center is the first sun gear (3, 6). The first sun gear consists of two parts (3, 6) joined by a press pass. These may also be manufactured as one piece. Radial needle bearings (46) and axial needle bearings (44) ensure that the first sun gear (3, 6) rotates smoothly around the main shaft (2). The modulo of the first planetary gear system is 1.5 in the diagram presented. The modulo is not fixed and can be changed to a value appropriate to the design parameters according to the specific design.

[0038] Figure 3 shows the second assembly step. A second ring gear (9) with gear teeth (9A) is mounted on top of the first ring gear (5). The second ring gear is smaller to provide space for the large needle bearing (45). When all outer components are bolted through the holes in the outermost component (49), the large axial needle bearing (45) transmits thrust between all components that together form the housing (1, 5, 9, 16, 17, 22, 23) and the first sun gear (3, 6). This thrust force is then transmitted back to the valve nut (40) through the needle bearing and main shaft (2). Without the large bearing (45), thrust bearings are required throughout the actuator; including the large bearing (45) simplifies the valve design, but is optional. Inside the second ring gear (9) is the second planetary gear (8) with its needle bearing (8A) and shaft (8B). The shaft is pressed into holes in the first sun gear (6). These holes (6B) are shown in FIG. 10, which shows the top half of the first sun gear (6). Also note the passage (6A) for the large axial needle bearing (45). The second sun gear (7) is joined to the lower sun gear (10) of the split ring gear. The modulo of the second planetary gear system is 1.0 in the diagram shown. The modulo is not fixed and can be changed to a value appropriate to the design parameters according to the specific design. If desired, one or more planetary gear systems similar to the second planetary gear system can be added above the second planetary gear system.

[0039] Figure 4 shows the third assembly step, where a split ring gear system is added. The reason for including a split ring gear system is to achieve a higher gear ratio than a regular planetary gear system at this stage. This is because the sun gears in each step must have a larger diameter than the main shaft. For example, in the illustrated diagram, the first planetary sun gear (3) has 64 teeth, and the first planetary ring gear (5) has 104 teeth. This results in a gear ratio of only 2.625. Therefore, a three-stage planetary gear system has a gear ratio of only approximately 18. In a split ring gear system, the gear ratio can be significantly larger. However, the torque transmission capacity of a split ring gear is lower than that of a planetary gear system. Therefore, including a split ring gear system coupled to the main shaft (2) via one or more planetary gear systems is an optional addition, although it does have certain advantages.

[0040] The split ring gear system of Figure 4 is constructed with modulo 0.5 gears. The modulo is not fixed and can be changed to a value appropriate to the design parameters according to the specific design. In the illustrated diagram, the lower annular sun gear (10) is the output and has 160 teeth, although various numbers of teeth are possible for different applications. In one example, the lower annular planetary gear (11) has 36 teeth. In this example, the upper annular planetary gear (14) has 32 teeth, but it is clear that a different number of teeth can be selected for one or both gears depending on the desired operation. The lower annular planetary gear (11) and the upper annular planetary gear (14) are mounted on the same shaft (14A). There is a press pass between the bores of the planetary gears (11, 14) and the shaft (14A), so the planetary gears (11, 14) and the shaft (14A) rotate as one part. The shaft (14A) is mounted within a bore in a needle bearing (12A) of the annular gear carrier (12). The ring gear carrier (12) is shown in FIG. 11. The ring gear upper sun gear (13) has 164 teeth in this example, but various tooth counts are possible for different applications. The ring gear upper sun gear (13) is attached to the main shaft (2) at the press pass, so it moves with the main shaft (2). The ring gear upper ring (20A) is part of the lower automatic lock (20) mechanism. The ring gear upper ring (20A) has 228 teeth in this example, but various tooth counts are possible for different applications. The ring gear upper ring (20A) is the input to the ring gear. The gear ratio for the ring gear using the presented configuration is approximately 9.3, but various gear ratios are possible for different applications. Because the upper sun gear has more teeth than the lower sun gear, the rotation direction for the ring gear is opposite. This is desirable because rotating the emergency handle (29) rotates the main shaft (2) in the same direction. This also results in a slightly higher overall gear ratio. Calculating the gear ratio is not straightforward as the upper annular sun gear moves with the main shaft (2) and the gear ratio is affected by the rotational speed of the main shaft (2). Figure 12 shows a cross section through the annular upper sun gear (13).

[0041] Figure 5 shows the fourth assembly step. In this step, the auto-lock mechanism is installed. The purpose of the auto-lock mechanism is to ensure that torque can only be transmitted from the motor to the valve. The auto-lock mechanism prevents torque from being transmitted from the valve to the motor, thereby ensuring that the valve does not move unintentionally. A novel feature of this actuator is that the auto-lock locks to the main shaft (2) rather than the housing (1, 5, 9, 16, 17, 22, 23). The reason for this design is that the auto-lock mechanism can be located inside the motor, resulting in an efficient, compact, and space-saving design. In one example, the auto-lock mechanism consists of a bottom auto-lock (20), one or more rollers (20B), one or more unlocking pins (19A), and a locking ring (21). The locking ring (21) has a press pass against the main shaft (2), so they rotate together. The roller (20B) is pressed into the locked position by a spring (20C), shown in the cross-sectional view of Figure 13. When the spring (20C) moves the roller (20B) toward the unlocking pin (19A), the roller (20B) presses against both the self-locking bottom (20) and the locking ring (21), creating a locking action with a machined surface (20D). As the rotor frame (19) rotates, one of the unlocking pins (19A) pushes one roller out of its locked position, allowing the rotor frame (19) to rotate in either direction. The two unlocking pins fit into two holes in the rotor frame (19) with a press pass. The inclusion of two unlocking pins and two rollers means that the locking mechanism can function with the rotor frame (19) rotating in either direction.

[0042] Figure 6 shows the fifth assembly step. In this step, the rotor, including the rotor frame (19), magnets (18), optional emergency gear wheel (27), and unlocking pin (19A), is placed on the automatic locking mechanism. Most of the rotor is hidden in Figure 6; the rotor is also shown in Figure 14. The rotor rotates around the main shaft (2) and is supported by ball bearings (43) and axial thrust needle bearings (44), which roll on the lock ring (21). The stator, including iron laminations (17), coil supports (16, 22), and coils (17A), is positioned outside the rotor. The annular gear carrier support (15) provides additional support to the annular gear carrier (12) via the large-radius bearing (43). The annular gear carrier support (15) also provides support for the stator, ensuring it is centered on the main shaft (2). The axial centerline of the stator and the axis of rotation of the rotating frame (19) coincide with the axial centerline of the main shaft. This also makes the overall device extremely compact. The electric motor may be a three-phase axial-flux PM motor with 12 poles and distributed windings. However, the actuator may use any electric motor with appropriate dimensions. The motor preferably includes a central through-hole and can be mounted around the main shaft. Therefore, all "off-the-shelf" motors are excluded.

[0043] It is possible to add a second "emergency shaft" and place an "off-the-shelf" or separate motor on this shaft to drive the actuator, but this solution would be significantly bulkier than the proposed design. The motor mounted in this manner could be an electric, hydraulic, or pneumatic motor. In this case, the magnets (18), coils (17A), steel laminations (17), etc., may not be required. Such an embodiment would include a rotating frame (19), but the rotating frame (19) would rotate via the emergency shaft rather than forming part of the rotor of the motor itself. Even if the rotating frame (19) forms part of the motor, an emergency shaft may be included for use in emergencies when the primary motor fails for some reason.

[0044] Figure 7 shows the location of the emergency shaft and optional encoder gear unit. This diagram is not an assembly step, as many components are not shown in their final assembled position. The positions of parts hidden by the encoder plate (24) are shown. In Figure 7, an encoder gear wheel (35) is attached to the main shaft (2). This encoder gear wheel interacts with the encoder gear unit (36) to rotate the encoder shaft (37) within the absolute encoder (38). The encoder gear unit (36) is positioned so that the encoder shaft rotates once for approximately 30 rotations of the main shaft. This allows the absolute encoder (38) to track the number of rotations of the main shaft (2) and, therefore, the valve position. The total valve stroke is assumed to be less than 30 rotations so that the absolute encoder (38) fits within one rotation, but these parameters are adjustable. For example, if the actuator is attached to a valve with a stroke length greater than 30 rotations, the encoder gear unit can be reconfigured.

[0045] Figure 7 shows the shafts and handles for emergency operation of the valve. The lower emergency shaft (25) has a gear wheel (26) that interacts with a gear wheel (27) above the motor. Thus, the lower emergency shaft (25) rotates when the motor rotates the valve. Rotation of the upper emergency shaft (28) and handle (29) during normal operation is undesirable because it would rapidly wear the emergency shaft seal (42). Therefore, there is a clutch between the upper emergency shaft (28) and the lower emergency shaft (25).

[0046] The clutch functions as follows: When the emergency operation is not in use, the lock wings (34) remain on the lock (31). Thus, the lock wings (34) lift and hold the emergency shaft (28). When the emergency handle (29) rotates, the lock wings rotate to a position where they are disengaged from the top of the lock (31). The spring (33) then pushes down the upper emergency shaft (28). As the upper emergency shaft (28) rotates further, the edge (28A) of the upper emergency shaft (28) descends into the slot (25A) of the lower emergency shaft (25). Therefore, rotation of the emergency handle (29) rotates the rotating frame (19) and moves the valve. The guide pin (28B) ensures that the upper emergency shaft (28) descends straight. The nut (30) attaches the lock wings (34) and emergency handle (29) to the upper emergency shaft (28). A bolt (31A) secures the lock (31) to the top cover (23). Figure 15 shows the emergency shaft in more detail. In Figure 15, the emergency handle (29) and nut (30) have been removed to reveal the lock wings.

[0047] Figure 8 shows the sixth assembly step, where most of the components shown exploded in Figure 7 are attached to the encoder plate (24), which is inserted by sliding its edges into the stator. Bearings between the encoder plate (24) and the main shaft (2) are not essential, but they help center the stator iron laminations (17) around the rotor. The encoder plate (24) serves as a support for the encoder (38), encoder shaft (37), encoder gearing (36), and lower emergency shaft (25).

[0048] Figure 1 shows the seventh and final assembly step that completes the actuator. Here, the top cover (23), top seal (41), emergency shaft seal (42), top emergency shaft (28), top emergency shaft spring (33), emergency handle (29), nut (30), locking wing (34), lock (31), and bearing (34) are installed on top of the actuator. Wires from the encoder and motor can be routed through holes (23A) in the top cover (23). Other solutions for routing wires are also possible. If the actuator is intended for submersible use, the connections must be IP68 rated.

[0049] After the actuator is attached to the valve, the hole in the central shaft can be filled with grease and the hole can be capped, ensuring that the valve nut (40) stays lubricated for a very long period of time.

Claims

1. a main shaft (2) having an opening (51) extending along an axial centerline of the main shaft (2) for receiving a valve stem; a first planetary gear system (3, 4, 5, 6) configured to rotate the main shaft (2) about an axial centerline, the first planetary gear system (3, 4, 5, 6) including a plurality of planetary gears (4), a first sun gear (3, 6), and a first ring gear (5); a motor for rotating the first planetary gear system; wherein the axial centerline of the main shaft (2) coincides with the center axis of the sun gear of the planetary gear system.

2. a hollow valve nut (40) coupled to the main shaft (2), having an axial centerline coincident with the axial centerline of the main shaft, and including a through hole through which the valve stem extends in use; 2. The valve actuator of claim 1, wherein an inner surface of the through hole is configured to interact with the valve stem to translate the valve stem along the axial centerline of the main shaft (2) as the main shaft rotates.

3. The valve actuator of claim 2, wherein the valve nut (40) is configured to be removably coupled to the main shaft (2).

4. 3. The valve actuator of claim 2, wherein the valve nut (40) and the main shaft (2) are formed as one integral part.

5. 5. The valve actuator according to claim 1, wherein the motor for rotating the first planetary gear system is an electric motor.

6. a rotor frame (19) rotatable about the axial centerline of the main shaft (2) and coupled to the main shaft (2) via the first planetary gear system (3, 4, 5, 6); The valve actuator according to any one of claims 1 to 5, comprising:

7. 7. The valve actuator of claim 6, wherein the rotor frame (19) is hollow and surrounds the main shaft (2).

8. A locking element (20) that is movable between a locked position in which the locking element (20) is pressed against the main shaft (2) or a locking ring (21) fixed to the main shaft (2) to prevent rotation of the main shaft (2), and an unlocked position in which the main shaft (2) can rotate relative to the locking element (20). The valve actuator according to any one of claims 1 to 7, comprising a locking mechanism including:

9. 9. The valve actuator according to claim 8 when dependent on either claim 6 or claim 7, wherein the locking mechanism comprises at least one unlocking pin (19A) coupled to the rotor frame (19) for transitioning the locking element (20) from the locked position to the unlocked position when the rotor frame (19) rotates in either direction about an axial centerline of the main shaft (2).

10. 10. The actuator for a valve according to any one of claims 1 to 9, further comprising a second planetary gear system (7, 8, 9) including a second plurality of planetary gears (8), a second sun gear (7), and a second ring gear (9), said planetary gear system (7, 8, 9) being arranged to couple said first planetary gear system (3, 4, 5, 6) to said main shaft to rotate said main shaft (2) about its axial centerline.

11. 11. The valve actuator according to claim 1, further comprising a first split ring gear system (10, 11, 12, 13, 14) including a lower annular sun gear (10), a plurality of lower annular planetary gears (11), a plurality of upper annular planetary gears (14), a ring gear carrier (12), and an upper annular sun gear (13), wherein the upper annular sun gear (13) is arranged to rotate together with the main shaft (2).

12. 12. The valve actuator of claim 11, wherein the annular gear system (10, 11, 12, 13, 14) is configured such that the upper annular sun gear (13) has a greater number of teeth than the lower annular sun gear (10), thereby reversing the direction of rotation of the main shaft (2).

13. 5. The valve actuator according to claim 2, wherein the hollow valve nut (40) is configured with an internal thread that allows the threaded valve stem to translate freely upward along the axial centerline of the main shaft (2) as the main shaft (2) rotates.

14. 5. The valve actuator of claim 2, wherein the through hole of the hollow valve nut (40) has a non-circular cross section, allowing a valve stem having a similar cross section to freely translate upward along the centerline of the main shaft (2) as the main shaft (2) rotates.

15. The valve actuator according to claim 6 or 7 when dependent on claim 5, wherein the rotor frame (19) is a frame of a rotor of the electric motor and is configured to rotate about the axial centerline of the main shaft (2).

16. 8. The actuator for a valve according to claim 6 or 7, wherein the motor is configured to rotate the main shaft (2) by transmitting torque through a bottom emergency shaft (25) and the rotor frame (19) to rotate the main shaft (2).

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