EP3636861B1

EP3636861B1 - Actuator for an electric lock and method of actuating an electric lock

Info

Publication number: EP3636861B1
Application number: EP18200061.2A
Authority: EP
Inventors: Herbert Meyerle
Original assignee: SimonsVoss Technologies GmbH
Current assignee: SimonsVoss Technologies GmbH
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2021-08-04
Anticipated expiration: 2038-10-12
Also published as: EP3636861A1

Description

TECHNICAL FIELD

The invention relates to an actuator for an electric lock and to a method of actuating an electric lock. The invention relates in particular to actuators and methods that may be used to couple a manually operable actuation element, such as a rotary knob, to a locking element, such as a latch or locking bolt.

BACKGROUND

Electric actuators may be provided in lock cylinders, door fittings, or electric locks for increased user convenience, safety, and control. Electric lock actuators may be used to displace a locking element, such as a latch or locking bolt, in response to a successful authentication of a user. Electric lock actuators may be used to selectively couple a manually operable actuation element, such as a door handle or rotary door knob, to a locking element.
An electric actuator for a lock should have a compact construction and should afford safety against manipulation attempts.
Electric actuators that comprise a spindle drive or other rotary-to-linear motion conversion mechanism have a compact construction. Exemplary electric actuators for locks that convert a rotary motion of a motor output shaft to a linear displacement are described in, e.g., DE 10 2004 046778 B4 and EP 2 963 212 A1 . EP 2 927 396 A1 discloses another exemplary coupling arrangement for a lock cylinder.
Conventional electric actuators that comprise a spindle drive or other rotary-to-linear motion conversion mechanism may be prone to manipulation attempts in which torque or an angular momentum is applied to the electric actuator or a component to which the electric actuator is mounted. For illustration, exertion of a force onto the electric actuator or a component housing the electric actuator, such as by hitting with a hammer or other mechanical tool, can create a torque pulse. Inertia of components of the electric actuator that are rotatably mounted in a housing of the actuator, such as a spindle of a spindle drive, can result in a relative rotary movement between the spindle and the housing of the actuator. Repeated application of torque pulses bears the risk that the spindle drive can be manipulated, due to the relative rotary movement between the spindle and the housing of the actuator.

SUMMARY

There is a need in the art for devices and methods that have a compact construction while affording enhanced safety. There is in particular a need in the art for devices and methods that provide enhanced safety against manipulation attempts in which a series of torque pulses is applied. More particularly, there is a need in the art for devices and methods that have a compact construction and afford enhanced safety against manipulation attempts in which a series of torque pulses is applied.
An electric actuator for a lock and a method as recited in the independent claims are provided. The dependent claims define embodiments.
According to embodiments of the invention, an electric actuator is provided which comprises a rotatably mounted drive sub-unit and a rotatably mounted driven sub-unit. The driven sub-unit may comprise or may be coupled to a spindle of a spindle drive. The drive sub-unit and the driven sub-unit may have rotation axes which extend parallel to each other, but which are offset from each other. The drive sub-unit and the driven sub-unit may have a geometrical shape and mass which are respectively selected such that the driven sub-unit partially or fully compensates a rotation of the drive sub-unit that is caused by a pulse of angular momentum or torque.
According to embodiments of the invention, an electric actuator is provided which comprises a rotatably mounted drive sub-unit and a rotatably mounted driven sub-unit. The driven sub-unit may comprise or may be coupled to a spindle of a spindle drive. The drive sub-unit and the driven sub-unit may have rotation axes which extend parallel to each other, but which are offset from each other. A first moment of inertia of the drive sub-unit and a second moment of inertia of the driven sub-unit may be matched to each other.
Matching the first and second moments of inertia allows safety to be enhanced, in particular for manipulation attempts which involve the application of a series of torque pulses to the actuator.
Matching the first and second moments of inertia may be done in such a way that the driven sub-unit substantially compensates a rotation of (or a torque on) the drive sub-unit that is generated by an angular momentum or torque pulse on the housing.
An actuator for an electric lock according to an aspect of the invention comprises a stator of an electric motor. The actuator comprises a drive sub-unit which is rotatably mounted. The drive sub-unit comprises a rotor of the electric motor, a drive shaft fixed to the rotor in a torque-proof manner or integral with the rotor, and a drive wheel fixed to the drive shaft in a torque-proof manner. The actuator comprises a driven sub-unit which is rotatably mounted. The driven sub-unit comprises a driven shaft extending parallel to the drive shaft and a driven wheel fixed to the driven shaft in a torque-proof manner. The driven wheel is engaged with the drive wheel. The drive sub-unit has a first moment of inertia, I₁, and the driven sub-unit has a second moment of inertia, I₂, wherein |I₁ - I₂| / max (I₁, I₂) is less than 20%
In embodiments, the first and second moments of inertia may be matched such that |I₁ - I₂| / max (I₁, I₂) < 10%, optionally |I₁ - I₂| / max (I₁, I₂) < 5%.
The first and second moments of inertia may be substantially equal to each other.
As explained above, matching the first moment of inertia and the second moment of inertia to each other has the effect that manipulatory torque or angular momentum pulses applied onto a housing or bracket to which the actuator is mounted do not result in a significant undesired rotation of the driven shaft, because the first and second moments of inertia cause torques of identical magnitude but opposite directions to act on the drive sub-unit and the drive sub-unit. The meshing engagement of the drive wheel and the driven wheel causes the net torque to be small or even substantially zero, preventing or substantially reducing an undesired rotation of the driven shaft in response to manipulatory actions that involve the application of a series of torque pulses.
The drive sub-unit may have a first rotation axis, and the driven sub-unit may have a second rotation axis which is parallel to the first rotation axis, but offset from the first rotation axis in a direction transverse to the first rotation axis.
The first moment of inertia may be a moment of inertia of the drive sub-unit relative to the first rotation axis, and the second moment of inertia may be a moment of inertia of the driven sub-unit relative to the second rotation axis.
The electric lock may comprise a manually operable actuation element, such as a rotary knob, having an actuation element rotation axis. The first moment of inertia may be a moment of inertia of the drive sub-unit relative to the actuation element rotation axis, and the second moment of inertia may be a moment of inertia of the driven sub-unit relative to the actuation element rotation axis.
A weight may be attached to a toothed portion of the driven wheel to ensure that the first and second moments of inertia satisfy |I₁ - I₂| / max (I₁, I₂) < 20%, optionally |I₁ - I₂| / max (I₁, I₂) < 10%, further optionally |I_I - I₂| / max (I₁, I₂) < 5%.
The actuator may further comprise a control member that is linearly displaceable along an axis of the driven shaft.
The actuator may comprise a spindle drive coupled to the driven shaft and the control member to effect a linear displacement of the control member.
The spindle drive may comprise a coil spring coupled to the driven shaft. The coil spring may be included in the driven sub-unit.
The coil spring may have a variable pitch along the axis.
The coil spring may have end windings and a center portion between the end windings, wherein the center portion of the coil spring has a variable pitch.
The coil spring may comprise a portion having zero pitch or negative pitch.
Such a configuration of the coil spring further increases safety against mechanical manipulation, such as against the application of force pulses in a direction parallel to the first rotation axis of the drive sub-unit.
The spindle drive may comprise a projection projecting from the control member and engaged with the coil spring.
The projection may be a finger projecting from the control member in a direction transverse, in particular perpendicular, to a center axis of the coil spring.
The finger may have a longitudinal axis in the direction transverse to the center axis of the coil spring. A length of the finger along its longitudinal axis may be greater than a width and height of the finger in the directions transverse to its longitudinal axis.
The actuator may further comprise a guide arrangement for guiding linear displacement of the control member.
The guide arrangement may secure the control member against pivoting.
The guide arrangement may comprise at least one guide rail.
The actuator may further comprise a coupling mechanism adapted to selectively couple a manually operable actuation element with a locking element when the coupling mechanism is in an engaged state.
The control member may have a first position in which it causes the coupling mechanism to be in the engaged state and a second position in which it causes the coupling mechanism to be in a disengaged state.
The actuator may further comprise a bias mechanism coupled to the control member to bias the control member to the second position.
The bias mechanism may provide enhanced safety against mechanical manipulation attempts. For illustration, when there is a small mismatch between the first and second moments of inertia due to manufacturing tolerances, the bias mechanism ensures that the control element will be moved towards a position in which the lock is safe when torque pulses are applied in an attempt of fraudulent tampering.
The bias mechanism may comprise a bias spring.
The actuator may further comprise a control circuit adapted to power the electric motor to displace the control member from the second position to the first position in response to a successful authentication of an access element.
An electric lock cylinder according to an embodiment comprises the actuator according to an embodiment.
The electric lock cylinder may comprise a rotary knob.
The actuator may be adapted to selectively couple the rotary knob with a locking element, such as a latch or locking bolt, of the lock cylinder.
An electric door fitting according to an embodiment comprises the actuator according to an embodiment.
The electric door fitting may comprise a rotary knob or a handle.
The actuator may be adapted to selectively couple the rotary knob or handle with a locking element, such as a latch or locking bolt, of the electric door fitting.
An electric lock according to an embodiment comprises the actuator according to an embodiment.
The electric lock may comprise a rotary knob or a handle.
The actuator may be adapted to selectively couple the rotary knob or handle with a locking element, such as a latch or locking bolt, of the electric lock.
A method of controlling an electric lock using an electric actuator may comprise performing an authentication procedure for an access element, and, in response to a successful authentication of the access element, activating an electric motor of the actuator.
The actuator used in the method may comprise a drive sub-unit which is rotatably mounted. The drive sub-unit may comprise a rotor of the electric motor, a drive shaft fixed to the rotor in a torque-proof manner or integral with the rotor, and a drive wheel fixed to the drive shaft in a torque-proof manner. The actuator may comprise a driven sub-unit which is rotatably mounted. The driven sub-unit may comprise a driven shaft extending parallel to the drive shaft, and a driven wheel fixed to the driven shaft in a torque-proof manner. The driven wheel is engaged with the drive wheel. The drive sub-unit has a first moment of inertia, I₁, and the driven sub-unit has a second moment of inertia, I₂, wherein |I₁ - I₂| / max (I₁, I₂) is less than 20%.
The electric lock may comprise a manually operable actuation element. Activating the electric motor may cause the manually operable actuation element to be coupled with a locking element such that a manual operation of the manually operable actuation element displaces the locking element.
The actuator used in the method may be the actuator according to an embodiment.
The actuator and method according to an embodiment may be used to selectively couple a manually operable actuation element, such as a door handle or rotary door knob, with a locking element, such as a latch or locking bolt.
Various effects can be attained by the actuator and method according to embodiments. The provision of a drive sub-unit and a driven sub-unit that have matching first and second moments of inertia allows safety to be enhanced, in particular for manipulation attempts involving the application of a series of torque or angular momentum pulses. The provision of a drive sub-unit and a driven sub-unit that have rotation axes which extend in parallel also is particularly suitable for using a spindle drive or other rotary-to-linear motion conversion mechanism having a compact construction, which can engage and disengage a coupling mechanism by linear displacement of a control element in a direction parallel to the first and second rotation axes. The provision of a bias mechanism that biases the control element can further enhance robustness against manipulation attempts which involve the application of a series of torque or angular momentum pulses.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in detail with reference to the drawings in which like or identical reference signs are used to designate like or identical elements.

Fig. 1 is a partial broken-away perspective view of an electric lock comprising an actuator according to an embodiment.
Fig. 2 is partial perspective view of components of the actuator according to an embodiment.
Fig. 3 is partial perspective view of components of the actuator according to an embodiment.
Fig. 4 is perspective view of the actuator according to an embodiment when a control element is in a first position.
Fig. 5 is perspective view of the actuator according to an embodiment when a control element is in a second position.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described in detail with reference to the drawings. While embodiments will be described in the context of electric door locks comprising an actuator for selectively coupling a rotary door knob to a locking element (such as a latch or locking bolt), embodiments of the invention are not limited to this particular use of the actuator.
As will be explained in more detail below, an actuator according to an embodiment comprises a drive sub-unit and a driven sub-unit, which are both mounted to be rotatable relative to a common frame. A first moment of inertia of the drive sub-unit, I₁, is matched to a second moment of inertia of the driven sub-unit, I₂, wherein |I₁ - I₂| / max (I₁, I₂) is less than 20%, optionally less than 10%, further optionally less than 5%.
It will be appreciated that due to manufacturing tolerances or other small deviations, the first and second moments of inertia may be considered to be substantially equal or matched to each other even when there is a small mismatch. For illustration, the first and second moments of inertia may be considered to be substantially equal or matched to each other when a modulus of a difference of the first and second moments of inertia divided by the maximum of the first and second moments of inertia, |I₁ - I₂| / max (I₁, I₂), where I₁ designates the first moment of inertia and I₂ designates the second moment of inertia, is less than 20%, preferably less than 10%, further preferably less than 5%.
Fig. 1 is a partial broken-away perspective view of an electric lock 1. The electric lock 1 comprises a rotary knob 11.
The electric lock 1 comprises an actuator 20. The actuator 20 may be operative to selectively couple the rotary knob 11 or another manually operable actuation element to a locking element such as a latch or locking bolt, in order to allow the locking element to be displaced by user-operation of the manually operable actuation element.
The actuator 20 may be housed in a lock cylinder, in a door fitting, and/or in a sleeve 12 extending from the rotary knob 11. The sleeve 12 may be integral with the rotary knob 11.
The actuator 20 may comprise an electric motor having a stator 14 and a rotor. The stator 14 may be mounted via a support bracket 13, e.g., within the sleeve 12. A drive shaft 22 may be integral with the rotor or may be attached to the rotor in a torque-proof manner. A drive wheel 23 may be attached to the drive shaft 22 in a torque-proof manner. The rotor of the electric motor, the drive shaft 22 and the drive wheel 23 in combination form a rotatably mounted drive sub-unit of the actuator 20. The drive sub-unit may be mounted rotatably relative to a frame, such as a reference frame defined by the stator 14 of the electric motor or by the mounting bracket 13. The drive sub-unit may be rotatable about a first rotation axis which is defined by the axis of the drive shaft 22.
The actuator 20 comprises a driven sub-unit which is rotatably mounted. The driven sub-unit comprises a driven shaft 32 and a driven wheel 33 which is fixed to the driven shaft 32 in a torque-proof manner. The driven sub-unit may comprise a spindle of a spindle drive, which may be formed by a coil spring 34 attached to the driven shaft 32 in a torque-proof manner. The driven sub-unit may be mounted rotatably relative to a reference frame, such as a reference frame defined by the stator 14 of the electric motor or by the mounting bracket 13. The drive sub-unit may be rotatable about a second rotation axis which is defined by the axis of the driven shaft 32.
The first rotation axis defined by the drive shaft 22 and the second rotation axis defined by the driven shaft 32 extend parallel to each other, but are offset from each other in a direction perpendicular to the first rotation axis.
The drive sub-unit formed by the rotor of the electric motor, the drive shaft 22, and the drive wheel 23 has a first moment of inertia. The first moment of inertia may be a moment of inertia of the drive sub-unit relative to the first rotation axis.
The driven sub-unit comprising the driven wheel 33, the driven shaft 32, and the optional coil spring 34 has a second moment of inertia. The second moment of inertia may be a moment of inertia of the driven sub-unit relative to the second rotation axis.
The drive sub-unit may consist of those components of the actuator 20 that are attached to the drive wheel 23 in a torque-proof manner. Accordingly, the first moment of inertia may be the moment of inertia of the drive wheel 23 and all those components of the actuator 20 that are attached to the drive wheel 23 in a torque-proof manner.
The driven sub-unit may consist of those components of the actuator 20 that are attached to the driven wheel 33 in a torque-proof manner. Accordingly, the second moment of inertia may be the moment of inertia of the driven wheel 33 and all those components of the actuator 20 that are attached to the driven wheel 33 in a torque-proof manner.
According to embodiments of the invention, the drive sub-unit and the driven sub-unit are designed in such a manner that the first moment of inertia is matched to the second moment of inertia. As explained above, it will be appreciated that deviations between the first and second moments of inertia may be unavoidable due to, e.g., manufacturing tolerances. Such deviations do not adversely affect the security and reliability of the actuator, provided that the first and second moments of inertia remain essentially equal, i.e., provided that |I₁ - I₂| / max (I₁, I₂), where I₁ designates the first moment of inertia and I₂ designates the second moment of inertia, is less than 20%, preferably less than 10%, further preferably less than 5%.
When a series of torque or angular momentum pulses is applied to the rotary knob 11 or the sleeve 12 in an attempt of fraudulent manipulation, the mechanical manipulation attempt does not result in a significant rotation of the coil spring 34 that would advance a linearly displaceable control element 41 (which will be described in more detail below). The torques on (or the angular displacement of) the drive sub-unit and the driven sub-unit are small and may essentially cancel. This prevents or reduces a rotation of the coil spring 34 relative to a frame in which the control element 41 is linearly displaceable.
The coil spring 34 of the driven sub-unit may form the input of a spindle drive, which will be explained in more detail with reference to Figs. 2 and 3.
Figs. 2 and 3 show partial perspective views of components of the actuator 20. The actuator may comprise a control element 41. The control element 41 may be mounted so as to be linearly displaceable in a frame of reference in which the drive sub-unit and the driven sub-unit of the actuator 20 are rotatably mounted. For illustration, guide rails 51, 52 may extend parallel to the drive shaft 22 and the driven shaft 32. The guide rails 51, 52 may guide linear displacement of the control element 41. The guide rails 51, 52 may be rigidly attached to a frame or housing of the actuator, e.g., to the support bracket 13. The guide rails 51, 52 may abut on and engage mating surfaces of the control element 41 so as to prevent a pivoting motion of the control element relative to the frame or housing of the actuator.
It will be appreciated that the control element 41 is not part of the driven sub-unit because it is not rotatably mounted. In particular, the control element 41 is not taken into consideration when determining the second moment of inertia of the driven sub-unit, because it is secured against rotation by the guide rails 51, 52.
A projection 44 projecting from the control element 41 may be disposed to extend into a space between adjacent coils of the coil spring 34. The projection 44 may be formed on a component 41 which may be embedded within a shell of the control element 41. The projection 44 may be finger-shaped, having a length (measured in a direction transverse to a center axis of the coil spring 43) which is greater than the width and height of the projection 44 (measured in the two directions transverse to the longest axis of the projection 44).
The projection 44 and the coil spring 34 may be formed of metal to reduce frictional forces.
For increased safety, the coil spring 34 may have a variable pitch along the axis. The coil spring 34 may have end windings and a center portion between the end windings, wherein the center portion of the coil spring has a variable pitch. The coil spring 34 may even comprise a portion having zero pitch or negative pitch.
Such a configuration of the coil spring 34 further increases safety against mechanical manipulation, such as against the application of force pulses in a direction parallel to the first rotation axis of the drive sub-unit and the second direction axis of the driven sub-unit.
In use of the actuator 20, the electric motor of the actuator 20 may be selectively activated. Activation of the electric motor causes the coil spring 34 to be rotated via the drive shaft 22, the drive wheel 23, the driven wheel 33 which is meshingly engaged with the drive wheel 23, and the driven shaft 22. Rotation of the coil spring 34 causes the control element 41 to be linearly displaced in a direction which is parallel to the first rotation axis of the drive sub-unit and the second rotation axis of the driven sub-unit.
The actuator 20 may be used in various ways for implementing locking and/or unlocking operations. For illustration, in an embodiment, the actuator 20 may be operative to displace the control element 41 between a first position (shown in Fig. 4) and a second position (shown in Fig. 5). When the control element 41 is in the first position, the control element 41 may cause a coupling mechanism (not shown) to be in an engaged state in which the rotary knob 11 or other manually operable actuation element of the lock is mechanically coupled, via the coupling mechanism, to a locking element (such as a latch or locking bolt). When the control element 41 is in the second position, the coupling mechanism may be disengaged, such that a manual operation of the rotary knob 11 or other manually operable actuation element is not transmitted to the locking element.
Various implementations of such coupling mechanisms are known in the art. For illustration, the control element 41 may engage a pin (which may be provided on the control element 41 or which may be coupled to the control element 41) with a mating recess for engaging the coupling mechanism, and may disengage the pin from the mating recess for disengaging the coupling mechanism.
For further safety enhancement, the actuator 20 may comprise a bias mechanism that biases the control element 41 into the second position. More generally, the actuator 20 may comprise a bias mechanism that biases the control element 41 into a safe position, i.e., a position in which the rotary knob 11 or other manually operable actuation element is decoupled from the locking element of the lock or in which the lock is otherwise maintained in a safe (typically locked) position.
The bias mechanism may comprise a bias spring 61 or other resilient element. The bias spring 61 or other resilient element may have a first end abutting on a shoulder 62 of the control element 41 and an opposite second end that abuts on a shoulder 63 that is fixed relative to the housing or frame of the actuator 20. For illustration, a shoulder 63 may be formed so as to be integral with or fixedly attached to the guide rail 51. The bias spring 61 may be arranged such that the guide rail 51 extends through the bias spring 61 to prevent a buckling deformation or other kinking of the bias spring 61.
Various effects are attained by the bias spring 61. For illustration, if a small mismatch between the first and second moments of inertia causes a small remnant rotation of the coil spring 34 in response to fraudulent manipulation, the bias spring 61 will ensure that the control element 41 is always displaced towards a position in which the lock remains safe. For illustration, the bias spring 61 can ensure that the control element 41 is always displaced towards a position in which a coupling mechanism between the rotary knob 11 or other manually operable actuation element and the locking element of the lock is disengaged.
In use of the actuator 20, operation of the actuator 20 may be controlled by a control circuit (not shown). The control circuit may perform an authentication of an access element. The access element may be a transponder, portable phone, portable computing device, or other access element. In response to a successful authentication, the control circuit may activate the electric motor to mechanically couple the rotary knob 11 or other manually operable actuation element and the locking element of the lock, for example.
Various techniques may be used to match the first moment of inertia of the drive sub-unit to the second moment of inertia of the driven sub-unit. For illustration, a weight 35 may be attached to a toothed portion of the driven wheel 33. A mass and/or radial mass distribution of the weight 35 may be selected such that the first moment of inertia of the drive sub-unit, I₁, is matched to the second moment of inertia of the driven sub-unit, I₂, such that |I₁ - I₂| / max (I₁, I₂) is less than 20%.
While embodiments have been described with reference to the drawings, alterations and modifications may be implemented in other embodiments. For illustration, the actuator according to an embodiment does not need to be housed in a sleeve of a rotary door knob, but may also be arranged at other locations, e.g., in a lock cylinder or in a door fitting.

Claims

An actuator (20) for an electric lock (1), the actuator (20) comprising:
a stator (14) of an electric motor;

a drive sub-unit which is rotatably mounted, the drive sub-unit comprising:
a rotor of the electric motor;

a drive shaft (22) fixed to the rotor in a torque-proof manner or integral with the rotor; and

a drive wheel (23) fixed to the drive shaft (22) in a torque-proof manner;

a driven sub-unit which is rotatably mounted, the driven sub-unit comprising:
a driven shaft (32) extending parallel to the drive shaft (22);

a driven wheel (33) fixed to the driven shaft (32) in a torque-proof manner, the driven wheel (33) being engaged with the drive wheel (23);

wherein the drive sub-unit has a first moment of inertia, I₁, and the driven sub-unit has a second moment of inertia, I₂, characterized in that |I₁ - I₂| / max (I₁, I₂) is less than 20%.
The actuator of claim 1, further comprising:
a control member (41) that is linearly displaceable along an axis of the driven shaft (32);

wherein a spindle drive (34, 44) of the actuator is coupled to the driven shaft (32) and the control member (41) to effect a linear displacement of the control member (41).
The actuator of claim 2,
wherein the spindle drive (34, 44) comprises a coil spring (34) coupled to the driven shaft (32).
The actuator of claim 3,
wherein the coil spring (34) has a variable pitch along the axis of the driven shaft (32), optionally where the coil spring (34) comprises a portion having zero pitch or negative pitch.
The actuator of any one of claims 3 to 4, wherein the spindle drive (34, 44) comprises a projection (44) projecting from the control member (41) and engaged with the coil spring (34).
The actuator of any one of claims 2 to 4, further comprising:
a guide arrangement (51, 52) for guiding linear displacement of the control member (41), optionally wherein the guide arrangement (51, 52) secures the control member (41) against pivoting.
The actuator of claim 6,
wherein the guide arrangement (51, 52) comprises at least one guide rail (51, 52).
The actuator of any one of claims 2 to 7, further comprising:
a coupling mechanism adapted to selectively couple a manually operable actuation element (11) with a locking element when the coupling mechanism is in an engaged state,

wherein the control member (41) has a first position in which it causes the coupling mechanism to be in the engaged state and a second position in which it causes the coupling mechanism to be in a disengaged state.
The actuator of claim 8, further comprising:
a bias mechanism (61) coupled to the control member (41) to bias the control member (41) to the second position, optionally wherein the bias mechanism (61) comprises a bias spring (61),

wherein the actuator optionally further comprises a control circuit adapted to power the electric motor (13) to displace the control member (41) from the second position to the first position in response to a successful authentication of an access element.
The actuator of any one of the preceding claims,
wherein |I₁ - I₂| / max (I₁, I₂) is less than 10%, optionally less than 5%.
An electric lock cylinder, comprising:
the actuator of any one of claims 1 to 10.
An electric door fitting, comprising:
the actuator of any one of claims 1 to 10.
An electric lock (1), comprising:
a rotary knob (11); and

the actuator according to any one of claims 1 to 10.
A method of controlling an electric lock (1), using the actuator of any one of claims 1 to 10, the method comprising:
performing an authentication procedure for an access element; and

in response to a successful authentication of the access element, activating the electric motor (13) of the actuator.
The method of claim 14, wherein the electric lock (1) comprises a manually operable actuation element (11), and wherein activating the electric motor (13) causes the manually operable actuation element (11) to be coupled with a locking element such that a manual operation of the actuation element (1) displaces the locking element.