Patent Description:
An electric actuator, also referred to as a linear actuator, is widely used in fields such as furniture, medical equipment, and solar power generation. The electric actuator mainly comprises: a drive motor, a drive worm, a worm gear, a screw rod, and a nut. The operating principle of electric actuators goes like this: the drive motor activates the drive worm to rotate; the drive worm which meshes with the worm gear actuates the worm gear to rotate; then rotation of the worm gear drives the screw rod to rotate, and rotation of the screw rod drives the nut to move axially; since the nut is usually attached to an inner tube, the axial movement of the nut results in extension and retraction motion of the inner tube.

Owing to application environments of the electric actuator, a clutch device is additionally provided mainly to disengage power transmission between the drive motor and the rotary screw rod when the electric actuator encounters drive motor failure or power-off or other circumstances which require power cutoff, whereby the rotary screw rod may be manually activated to realize reverse push. For example, the Chinese Patent Application No. <CIT> discloses a solution of additionally providing a clutch device to an electric actuator.

In addition, in order to generate a resistance upon retraction of the electric actuator, a self-locking device is usually provided on the electric actuator; the self-locking device generally comprises a friction sleeve and a self-locking torsion spring sleeved outside the friction sleeve, such that when the friction sleeve rotates reversely along with the rotary screw rod, the self-locking torsion spring retracts radially to embrace the friction sleeve, whereby to generate a self-locking resistance against the rotary screw rod. Such self-locking devices provided on an electric actuator have been well known.

However, conventional electric actuators are only provided with either a clutch device or a self-locking device; even the clutch device and the self-locking device are both provided, the driving units for driving the two devices are usually provided standalone, such that in the case of need to control the clutch device and the self-locking device simultaneously, it would be very complex to manipulate the two devices independently and synchronously.

Moreover, conventional clutch devices or self-locking devices are substantially driven by a cable pulling a cable pulling lever; however, it is difficult to control the pulling strength or stroke of such a driving manner, resulting in operation clumsiness of the clutch device or self-locking device. Hand-rotatory release devices are already available in the market. For example, the Chinese Utility Patent No. <CIT> discloses a hand-rotatory release solution. However, such a hand-rotatory device is usually mounted on an end portion of the electric actuator, and if the installed stroke of the electric actuator is restricted, the mount space for the electric actuator with a hand-rotatory device would be affected. International patent application <CIT> discloses a linear actuator with a disengagement unit for interrupting the connection between a motor of the linear actuator and a spindle of the liner actuator.

To overcome the above and other drawbacks in conventional technologies, the invention provides an electric actuator according to claim <NUM> and having a hand-rotatory release device, which enables control of two devices with one hand-rotatory release device and offers smoother, more convenient operation.

The present invention adopts the following technical solution.

An electric actuator having a hand-rotatory release device comprises: a housing, a drive motor, a transmission assembly, a rotary screw rod and a driving nut, the drive motor activating, via the transmission assembly, the rotary screw rod to rotate, rotation of the rotary screw rod driving the driving nut to move axially along the rotary screw rod; and the electric actuator further comprises:.

The present invention offers the following benefits:.

The electric actuator according to the present invention is provided with both a clutch device and a self-locking device, which improves functional versatility of the electric actuator; moreover, the clutch device in combination with the self-locking device further offers an advantage that the rotary screw rod, which is substantially in a completely free rotation state after the clutch device disengages the power transmission, easily results in a very fast retraction speed of the electric actuator, while the self-locking device may provide certain resistance to prevent the rotary screw rod from retracting too fast.

Secondly, the self-locking device according to the invention is further provided with a release torsion spring, such that the self-locking device is unlockable by itself; when the release torsion spring is released, the self-locking device is in an unlocked state; now, irrespective of whether the electric actuator rotates forwardly or reversely, the self-locking device substantially produces no resistance against the rotary screw rod, which renders the electric actuator in a state of quick release, i.e., the electric actuator may retract quickly.

Additionally, the electric actuator according to the invention is further provided with a hand-rotatory release device in this embodiment. The hand-rotatory release device comprises a first driving member, a second driving member, and a release rotary knob configured to activate the first driving member and the second driving member, the first driving member and the second driving member being configured to drive the clutch device and the self-locking device, respectively, such that when it is needed to quickly release the electric actuator, an operator manipulates the hand-rotatory release device to be in a completely released state, which renders the clutch device in a disengaged state and meanwhile the self-locking device in an unlocked state; accordingly, the user may conveniently control the two devices by manipulating the hand-rotatory release device.

Finally, the hand-rotatory release device according to the present invention is released via the release rotary knob. Such rotational setting enables better control of the driving strokes of the first driving member and the second driving member, thereby mitigating the instantaneous over large driving stroke occurring to the first driving member and second driving member as much as possible, and thereby offering a smoother operation. Moreover, the hand-rotatory release device according to the present inventioninvention is disposed on the housing, rather than being disposed on an end portion of the electric actuator like a conventional hand-rotatory device, which eliminates a need of additionally increasing the axial retracted height of the electric actuator, without affecting the axial mount space.

Preferably, the hand-rotatory release device further comprises a pull lever axially movable along the rotary screw rod, a rack portion being provided on the pull lever, the release rotary knob being attached with a release gear which meshes with the rack portion.

Preferably, the electric actuator comprises an outer tube, and an inner tube extendable and retractable relative to the outer tube, a mount base being mounted on the outer tube, the release rotary knob being rotatably mounted on the mount base, the pull lever being at least partially slidably mounted on the mount base.

Preferably, a limit step is provided on the pull lever, a pull lever reset spring for resetting the pull lever is provided between the limit step and the mount base.

Preferably, the second driving member comprises a push block, the push block being provided on the pull lever or being provided integrated with the pull lever, the push block having a guiding face, the release torsion spring comprising a pin which extends radially, wherein when the pull lever moves axially, the guiding face on the push block abuts against the pin, resulting in outward expanding of the release torsion spring.

Preferably, the first driving member comprises a swing link rotatable relative to the housing, wherein axial movement of the pull lever brings the swing link to rotate, and swinging of the swing link axially pushes the clutch device.

Preferably, the transmission assembly comprises a drive worm and a drive worm gear, the drive worm being connected to the drive motor, the drive worm gear being sleeved outside the rotary screw rod, the clutch device being provided between the drive worm gear and the rotary screw rod.

Preferably, the clutch device comprises an adapter coupling, a toothed groove in transmission fit with the adapter coupling being provided on the drive worm gear, the adapter coupling being sleeved over the rotary screw rod and axially movable relative to the rotary screw rod.

Preferably, the self-locking device comprises a first friction sleeve and a second friction sleeve; the first friction sleeve and the second friction sleeve being sleeved over the rotary screw rod, respectively, an axial end face of the first friction sleeve abutting against an axial end face of the second friction sleeve, the first friction sleeve rotating synchronously with the rotary screw rod, the second friction sleeve rotating freely relative to the rotary screw rod, a self-locking torsion spring being sleeved over the first friction sleeve, and the release torsion spring being sleeved over the second friction sleeve; or, the self-locking device comprises a third friction sleeve, the third friction sleeve rotating synchronously with the rotary screw rod, the release torsion spring being sleeved over the third friction sleeve.

Preferably, in the course of the hand-rotatory release device's returning to the initial state from the completely released state, the second driving member is firstly disengaged from the release torsion spring on the self-locking device to generate a self-locking force, and after the release torsion spring returns to the initial state, the first driving member is correspondingly disengaged from the clutch device.

These characteristics and advantages of the inventioninvention will be disclosed in detail through the embodiments below with reference to the accompanying drawings.

Hereinafter, the invention will be described in further detail with reference to the accompanying drawings, among which:.

Hereinafter, the technical solutions of the present invention will be explained and illustrated through embodiments with reference to the accompanying drawings. However, the embodiments are only some embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art without exercise of inventive work based on the examples in the embodiments all fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the orientational or positional relationships indicated by the terms "inner," "outer," "upper," "lower," "left," and "right," etc. are orientational or positional relationships based on the drawings, which are intended merely for facilitating description of the present invention and simplifying relevant illustrations, not for indicating or implying that the devices or elements compulsorily possess those specific orientations and are compulsorily configured and operated with those specific orientations; therefore, such terms should not be construed as limitations to the present invention.

As illustrated in <FIG>, an electric actuator, also referred to as a linear actuator, is provided in this embodiment. The electric actuator comprises: a housing, an outer tube <NUM>, an inner tube <NUM>, a drive motor, a transmission assembly, a rotary screw rod <NUM>, and a driving nut <NUM>, wherein the drive motor activates, via the transmission assembly, the rotary screw rod <NUM> to rotate, and rotation of the rotary screw rod <NUM> brings the driving nut <NUM> to move axially along the rotary screw rod <NUM>; since the driving nut <NUM> is securely connected to the inner tube <NUM>, axial movement of the driving nut <NUM> brings the inner tube <NUM> to move axially relative to the outer tube <NUM> and the housing; a to-be-driven object is connected to an outer end of the inner tube <NUM>. The electric actuator in this embodiment further comprises:.

In this embodiment, the electric actuator is provided with both a clutch device and a self-locking device, which improves functional versatility of the electric actuator; moreover, the clutch device in combination with the self-locking device further offers an advantage that the rotary screw rod <NUM>, which is substantially in a completely free rotation state after the clutch device disengages the power transmission, easily results in a very fast retraction speed of the electric actuator, while the self-locking device may provide certain resistance to prevent the rotary screw rod <NUM> from rotating too fast, thereby preventing the driving unit <NUM> from retracting too fast.

Secondly, the self-locking device is further provided with a release torsion spring <NUM>, such that the self-locking device is unlockable by itself; when the release torsion spring is released, the self-locking device is in an unlocked state; now, irrespective of whether the electric actuator rotates forwardly or reversely, the self-locking device substantially produces no resistance against the rotary screw rod <NUM>, which renders the electric actuator in a state of quick release, i.e., the electric actuator may retract quickly.

Additionally, the electric actuator is further provided with a hand-rotatory release device in this embodiment. The hand-rotatory release device comprises a first driving member, a second driving member, and a release rotary knob <NUM> configured to activate the first driving member and the second driving member, the first driving member and the second driving member being configured to activate the clutch device and the self-locking device, respectively, such that when it is needed to quickly release the electric actuator, an operator manipulates the hand-rotatory release device to be in a completely released state, which renders the clutch device in a disengaged state and meanwhile the self-locking device in an unlocked state; accordingly, the user may conveniently control the two devices by manipulating the one hand-rotatory release device.

Finally, the hand-rotatory release device in the present invention is released via a release rotary knob <NUM>. Such rotational setting enables better control of the driving strokes of the first driving member and the second driving member, mitigating the instantaneous over large driving stroke occurring to the first driving member and second driving member as much as possible, thereby offering a smoother operation. Moreover, the hand-rotatory release device according to the present invention is disposed on the housing, rather than being disposed on an end portion of the electric actuator like a conventional hand-rotatory device, which eliminates a need of additionally increasing the axial retracted height of the electric actuator, without affecting the axial mount space.

In this embodiment, in order to improve manipulation precision of the release rotary knob <NUM> when being turned, the hand-rotatory release device further comprises a pull lever <NUM> which is axially movable along the rotary screw rod, a rack portion <NUM> being provided on the pull lever, wherein the rack portion <NUM> may be constructed integrally with or separately from the pull lever <NUM>; the release rotary knob <NUM> is attached with a release gear <NUM> in mesh with the rack portion <NUM>, such that when the release rotary knob <NUM> is rotated, the release gear <NUM> is brought to rotate, while rotation of the release gear <NUM> drives the rack portion <NUM> to move axially along the rotary screw rod <NUM>, thereby driving the pull lever <NUM> to move axially; axial movement of the pull lever <NUM> brings the first driving member and the second driving member to move, thereby achieving the purpose of driving the clutch device and the self-locking device.

In order to install the pull lever <NUM> more securely, a mount base <NUM> is mounted on the outer tube in this embodiment, the release rotary knob <NUM> is rotatably mounted on the mount base <NUM>, and the pull lever <NUM> is at least partially slidably mounted on the mount base <NUM>. As illustrated in <FIG>, the mount base <NUM> is sleeved over the outer tube <NUM> in this example, the rack portion <NUM> of the pull lever <NUM> being disposed in the mount base <NUM>, a fraction of the pull lever <NUM> extending out of the mount base <NUM>; a base cover plate <NUM> is provided over the mount base <NUM> to cover those parts including the release gear <NUM> and the rack portion <NUM>.

A limit step is provided on the pull lever in this embodiment, a pull lever resetting spring <NUM> for resetting the pull lever <NUM> being provided between the limit step and the mount base <NUM>. In this embodiment, the pull lever comprises a first pull lever and a second pull lever, the first pull lever being configured mainly to drive the first driving member and the second driving member, the corresponding rack portion <NUM> being provided on the second pull lever, wherein the first pull lever has a rectangular flat shape as a whole and the second pull lever is relative thin cable, thereby forming the limit step at a joint between the first pull lever and the second pull lever; while the pull lever reset spring <NUM> is disposed between the limit step and the mount base <NUM>, such that when the force applied upon the release rotary knob vanishes, the corresponding pull lever is reset to the initial position under the action of the pull lever reset spring <NUM>.

In this embodiment, the transmission assembly comprises a drive worm <NUM> and a drive worm gear <NUM>, wherein the drive worm <NUM> is connected to the drive motor, the drive worm gear <NUM> is sleeved outside the rotary screw rod <NUM> and coaxial with the rotary screw rod <NUM>, and the clutch device is disposed between the drive worm gear <NUM> and the rotary screw rod <NUM>. In this embodiment, the clutch device is mainly configured to disengage the power link between the drive worm gear <NUM> and the rotary screw rod <NUM>.

Hereinafter, specific constructions of the clutch device and the self-locking device are described below:
<FIG> and <FIG> illustrate a specific construction of the clutch device in this embodiment. The clutch device comprises a ball bushing <NUM>, a spline sleeve <NUM>, and an adapter coupling <NUM>, wherein the ball bushing <NUM> is sleeved over the rotary screw rod <NUM> via a squared section and rotates synchronously with the rotary screw rod <NUM>; a plurality of balls are provided on an outer periphery of one end of the ball bushing <NUM>, the spline sleeve <NUM> is sleeved outside the ball bushing <NUM>, and the spline sleeve <NUM> is constantly in mesh with the drive worm gear <NUM>, wherein the spline sleeve <NUM> and the ball set <NUM> are not directly connected, and the adapter coupling <NUM> is configured to engage or disengage the spline sleeve <NUM> with or from the ball bushing <NUM>, the adapter coupling <NUM> being axially movable relative to the rotary screw rod <NUM>.

As illustrated in <FIG>, a spline slot fitted with the spline sleeve <NUM> is provided on an inner wall of the adapter coupling <NUM> in this embodiment, i.e., the adapter coupling <NUM> constantly rotates synchronously with the spline sleeve <NUM>; a ball groove <NUM> fitted with balls of the ball bushing <NUM> is further provided on an inner wall of the adapter coupling <NUM>, such that when the adapter coupling <NUM> moves axially towards the balls on the ball bushing <NUM>, the balls are docked into the ball groove <NUM>, causing the adapter coupling <NUM> to be fitted and docked with the ball groove <NUM>, thereby implementing torque transmission between the adapter coupling <NUM> and the ball bushing <NUM>. Therefore, the adapter coupling now serves to couple the rotary screw rod <NUM> and the drive worm gear <NUM>. The state illustrated in <FIG> is the state in which the adapter coupling <NUM> is docked with the ball bushing <NUM>. When the adapter coupling <NUM> moves away from the balls, the adapter coupling <NUM> is disengaged from the ball bushing <NUM>, whereby to disengage torque transmission between the adapter coupling <NUM> and the rotary screw rod <NUM>.

In this embodiment, the self-locking device comprises: a first friction sleeve <NUM>, a second friction sleeve <NUM>, a release torque spring <NUM>, and a self-locking torque spring <NUM>, wherein the second friction sleeve <NUM> is sleeved outside the first friction sleeve <NUM>, an outer end face of the first friction sleeve <NUM> abuts against an inner end face of the second friction sleeve <NUM>, and the first friction sleeve <NUM> and the rotary screw rod <NUM> are positioned via a squared section, i.e., in the circumferential direction, the first friction sleeve <NUM> and the rotary screw rod <NUM> rotate synchronously therebetween, while the second friction sleeve <NUM> rotates freely relative to the rotary screw rod <NUM>; and in the axial direction, the outer end face of the first friction sleeve <NUM> abuts against the inner end face of the second friction sleeve <NUM>. Meanwhile, the release torque spring <NUM> is sleeved over the second friction sleeve <NUM>, the release torque spring <NUM> always embraces the second friction sleeve <NUM> in the initial state, and the self-locking torque spring <NUM> is sleeved over the first friction sleeve <NUM>. The self-locking device in this embodiment reduces the mount space, mainly the axial space, which facilitates reducing the overall size of the electric actuator.

When the inner tube <NUM> in the electric actuator extends out normally, the drive motor activates, via the clutch device, the rotary screw rod <NUM> to rotate forwardly; and after the inner tube <NUM> extends out till a predetermined position, the drive motor stops. At that position, when the inner tube <NUM> has a retraction tendency, an axial end face of the first friction sleeve <NUM> abuts against an axial end face of the second friction sleeve <NUM>; since the self-locking torque spring <NUM> serves to embrace the first friction sleeve <NUM> to produce a resistance and meanwhile the second friction sleeve <NUM> is also embraced by the release torque spring <NUM> in a normal state, a friction resistance is produced when the end face of the first friction sleeve <NUM> abuts against the end face of the second friction sleeve <NUM>; the friction resistance generates a resistance against the rotary screw rod <NUM> to prevent the rotary screw rod <NUM> from reverse rotation, thereby implementing self-locking.

In the case of normal retraction of the electric actuator, the drive motor drives, via the clutch device, the rotary screw rod <NUM> to rotate reversely; at this point, the rotating torque of the rotary screw rod <NUM> overcomes the self-locking force provided by the self-locking device, and the rotary screw rod <NUM> continues reverse rotation.

When the electric actuator needs to retract rapidly before extending out to the predetermined position, this embodiment enables unlocking of the self-locking device, thereby achieving the purpose of rapid release. In this embodiment, the unlocking is mainly implemented via the second driving member. The second driving member specifically comprises: a push block <NUM>, the push block <NUM> being preferably integrated with the pull lever, i.e., in this embodiment, the self-locking device and the clutch device share one pull lever <NUM>; the push block <NUM> is provided with a guiding face <NUM>; the release torque spring <NUM> comprises a pin <NUM> extending radially; wherein the guiding face <NUM> is disposed on a side face of the push block <NUM>, such that when the pull lever <NUM> is pulled to move, the guiding face <NUM> on the push block <NUM> abuts against the pin <NUM> to outwardly expand the release torque spring <NUM>; when the release torque spring <NUM> is expanded outwardly, the resistance between the release torque spring <NUM> and the second friction sleeve <NUM> will be diminished correspondingly. In this state, when the end face of the first friction sleeve <NUM> abuts against the end face of the second friction sleeve <NUM>, the second friction sleeve <NUM> will rotate synchronously along with the first friction sleeve <NUM>; as such, the first friction sleeve <NUM> does not produce a resistance against the rotary screw rod <NUM>, thereby achieving a resistance-free state of the rotary screw rod <NUM>. At this point, if the clutch device disengages the connection, the self-locking device will also be unlocked. Under this state, the rotary screw rod <NUM> is substantially in a freely idling state, which enables rapid retraction of the driving nut <NUM>.

Additionally, in this embodiment, by gradually pushing the release torque spring <NUM> via the guiding face <NUM>, the self-locking device is gradually diminished, such that the self-locking device will not vanish abruptly, thereby achieving an objective of stepless adjustment.

In view that the clutch device and the self-locking device are both provided in this embodiment, the axial force is transmitted in the following manner:
When the inner tube <NUM> of the electric actuator extends till a predetermined position and has a tendency of retraction, the axial force of the inner tube <NUM> is transmitted to the driving nut <NUM>; the driving nut <NUM> transmits the axial force to the rotary screw rod <NUM>; when the rotary screw rod <NUM> is subjected to the axial force, the ball bushing <NUM> abuts against the shoulder position of the rotary screw rod <NUM>, such that the axial force applied against the rotary screw rod <NUM> is first transmitted to the ball bushing <NUM>; since the end face of the ball bushing <NUM> abuts against the end face of the first friction sleeve <NUM>, i.e., the ball bushing <NUM> and the first friction sleeve <NUM> are axially limited, the axial force is transmitted to the first friction sleeve <NUM>; since the tail end face of the first friction sleeve <NUM> abuts against the inner end face of the second friction sleeve <NUM>, the axial force is transmitted to the second friction sleeve <NUM>; and since a conical roller bearing <NUM> is provided between the tail end face and the tail pull head <NUM> of the second friction sleeve <NUM>, the axial force will be finally transmitted to the tail pull head <NUM> via the conical roller bearing <NUM>.

In this embodiment, the ball bushing <NUM>, the first friction sleeve <NUM>, and the second friction sleeve <NUM> jointly constitute an axial limit kit, wherein the rotary screw rod <NUM> transmits the axial force to the tail pull head <NUM> via the axial limit kit; from the perspective of the overall process of axial force transmission, the adapter coupling <NUM> in this embodiment is never subjected to the action of the axial force; therefore, it is also labor-saving to turn the adaptor coupling <NUM>.

Meanwhile, since the clutch device is not subjected to the axial force from the rotary screw rod <NUM>, the service life of the clutch device may be significantly improved. Of course, it is noted that, if the self-locking device is not provided in the electric actuator, a shaft sleeve-like construction may be additionally provided to the rotary screw rod <NUM>, serving as an axial limit kit.

In this embodiment, the first friction sleeve <NUM> preferably comprises a front sleeve and a rear sleeve, and a thrust bearing is provided to abut against the axial middle between the front sleeve and the rear sleeve; in an alternative embodiment, the first friction sleeve <NUM> may be an integral sleeve.

In this embodiment, the first driving member comprises: a swing link <NUM> connected to the pull lever <NUM>. In an actual installation, an upper end of the swing link <NUM> is rotatably connected to the pull lever <NUM>. Specifically, a notch is provided at the bottom of the pull lever <NUM>, the top of the swing link <NUM> is positioned in the notch; the middle of the swing link <NUM> is rotatably mounted on a swing link sleeve <NUM>; a lower end of the swing link <NUM> is connected to the adapter coupling <NUM>, such that when the pull lever <NUM> is pulled to move, the swing link <NUM> swings to push the adapter coupling <NUM> to move axially.

In order to optimize manipulation of the clutch device and the self-locking device, the operation sequence of the clutch device and the self-locking device is optimized in this embodiment:
As illustrated in <FIG> and <FIG>, in the initial state, the guiding face <NUM> of the push block <NUM> needs to move a segment of stroke to be in contact with the pin <NUM> of the release torque spring <NUM>; this segment of stroke may be understood as an idle stroke of the push block <NUM>; during this idle stroke, the clutch device operates normally, such that the adapter coupling <NUM> is first turned; meanwhile, upon reset, the self-locking device is first self-locked, and then the clutch device performs power engagement, offering an advantage that after the self-locking device produces a self-locking force, the rotating speed of the rotary screw rod <NUM> decreases, such that when the adapter coupling <NUM> is engaged with the ball bushing <NUM>, no damages are caused to the adapter coupling <NUM> and the ball bushing <NUM>, thereby significantly extending their service life.

It is noted that the constructions of the self-locking device and the clutch device are not limited to those illustrated in this embodiment. An exemplary self-locking device may merely comprise one third friction sleeve, wherein the third friction sleeve rotates synchronously with the rotary screw rod <NUM>, and the release torque spring <NUM> is sleeved over the third friction sleeve; in the initial state, the release torque spring <NUM> embraces the third friction sleeve to produce a resistance against the rotary screw rod <NUM>; in this case, the release torque spring <NUM> serves as the self-locking torque spring <NUM>; after the release torque spring <NUM> is pushed to move by the push block <NUM>, the resistance from the release torque spring <NUM> against the third friction sleeve vanishes. An exemplary clutch device may be implemented by an alternative combination of the spline sleeve <NUM> and the spline.

Claim 1:
An electric actuator comprising: a housing (<NUM>, <NUM>), a drive motor, a transmission assembly (<NUM>, <NUM>), a rotary screw rod (<NUM>) and a driving nut (<NUM>), the drive motor activating, via the transmission assembly, the rotary screw rod (<NUM>) to rotate, rotation of the rotary screw rod (<NUM>) bringing the driving nut (<NUM>) to move axially along the rotary screw rod (<NUM>), the electric actuator further comprises
a clutch device (<NUM>, <NUM>, <NUM>) provided between the transmission assembly and the rotary screw rod (<NUM>) and configured to engage or disengage power transmission between the transmission assembly and the rotary screw rod (<NUM>);
a self-locking device (<NUM>, <NUM>) configured to produce a friction resistance against the rotary screw rod (<NUM>) when the rotary screw rod (<NUM>) rotates reversely, wherein the self-locking device comprises a release torsion spring (<NUM>) for unlocking the self-locking device; and characterized in that the electric actuator further comprises
a hand-rotatory release device provided on the housing, the hand-rotatory release device comprising a first driving member (<NUM>), a second driving member (<NUM>, <NUM>) and a release rotary knob (<NUM>) for activating the first driving member and the second driving member, the first driving member being connected to the clutch device, the second driving member being configured to connect the self-locking device, and the release rotary knob (<NUM>) being turned to present an initial state and a completely released state, wherein in the course of switching from the initial state to the completely released state, the first driving member activates the clutch device to disengage the power connection, and the second driving member activates the release torsion spring (<NUM>) to release.