Locking for electric motor rotation of a linear actuator

Abstract

The present invention relates to a linear actuator having an improved electric motor. In particular, the present invention focuses on an improved technical solution for braking or locking a rotating electric motor using an electromechanical locking mechanism. This mechanism uses a solenoid having a non-rotating locking element that can be displaced by solenoid action and is positioned to engage with a rotating locking element. In particular, the solution was found to enable a remarkably small solenoid with significantly reduced requirements for stroke length to be effectively locked in a single direction or in both directions for the rotation of the motor.

Description

Technology Field

[0001] The present invention relates to a linear actuator having an improved electric motor. In particular, the present invention focuses on an improved technical solution for braking or locking of an electric motor. Throughout this specification, the term "motor" may be referred to as an electric motor.

[0002] Linear actuators and electric motors are useful for transmitting mechanical power to a machine to raise or otherwise move a load. Locking or braking is desirable to prevent the movement of such lifting machines from being reversed, and is particularly desirable to ensure that external forces applied to the machine do not rotate the motor when power to the motor is switched off. In lifting machines, such locking or braking enables the machine to maintain the load in place even after the motor is electrically switched off. Background Technology

[0003] In some applications, it has been common practice to rely on friction limiting in lifting machines and / or motors to achieve a sufficient degree of braking or locking. The rotational mechanical power of the motor is often converted and transmitted through gearing devices where friction is inevitably introduced, thereby assisting in load-holding operations. Certain gearings, such as worm gears, can be specially designed to achieve high friction. Motors equipped with such gearing are sometimes referred to as "self-locking." Another means of achieving braking is to introduce a wrap spring clutch into the rotating shaft of the machine. An example of this is disclosed in US Patent No. 9,369,026. When properly installed, a wrap spring clutch can exert a higher frictional force when the shaft rotates in one direction than in another.

[0004] The braking effect can be further activated by deploying a motor specifically designed to exhibit so-called detent torque or cogging torque resulting from magnetic interaction between the motor's stator and rotor even when the motor is switched off.

[0005] The aforementioned solution has the disadvantage of not providing sufficiently safe and reliable locking. An additional drawback is that energy is consumed to overcome friction and / or cogging torque because the braking effect remains during the operation of the machine and motor. Relying on friction is not always satisfactory because the braking effect depends, for example, on lubrication, manufacturing tolerances, and wear. An additional disadvantage of relying on friction is when excessively large torque is applied to the rotating shafts of the machine and motor, for example, in the case of a fault. In such situations, the rotating shafts and motor rotate unintentionally more, causing unstable locking.

[0006] Locking of the rotation of an electric motor may also be accomplished by using ring-shaped discs for locking (as a complement or alternative to any of the solutions described above). Examples thereof are disclosed, for instance, in US 2008 / 0251329 and EP 1320176. A ring-shaped disc attached to a shaft or other rotating element may be optionally moved from a position that does not engage with a ring-shaped disc fixedly positioned on the opposite side to a locking or braking position that engages with and frictionally interferes with the fixed ring-shaped disc. One or the other disc may be moved axially by an external force. The external force may be any known type. In some applications, an electromagnetic force is preferred to activate this motor lock, for example, by using a solenoid mechanism. The mechanism is configured as a spring return. The solenoid enables movement of the locking part in a direction parallel to the motor shaft axis. The solenoid is in the shape of a ring through which the motor shaft passes. The solenoid of the disclosed design is centrally positioned on the motor shaft. This requires large and heavy coil winding.

[0007] These solutions have the additional disadvantage of being unnecessarily bulky. Relying on friction between the surfaces of the two ring-shaped discs is also a disadvantage, as it is known that friction characteristics depend on external factors that cannot be properly controlled over the motor's lifespan. As mentioned above, another disadvantage of relying on friction arises when excessively large torque is applied to the motor shaft. In such situations, the friction between the surfaces of the two ring-shaped discs is overcome, leading to unreliable locking. Unacceptable noise is associated with the snapping sound of the relatively large rings back and forth when starting and stopping the motor. Achieving a reliable motor lock incurs costs because strict manufacturing tolerances must be adhered to. Particularly for motors requiring rotation locking in only one direction, such motor lock designs are often more powerful and feature-rich than necessary for their intended use. Furthermore, for motor locks that lock in both directions, it is preferable to propose a design with less bulk.

[0008] Other known motor locking mechanisms include a solenoid actuation pin, wherein the pin is positioned to selectively engage with or disengage from a gear wheel. An example is disclosed in US 2010 / 0319477. The gear wheel is also used as the actuation part of a mechanism that reduces the rotational speed of the motor output shaft. The gear wheel forms part of the gearing mechanism and is positioned in close proximity to the motor. This arrangement has the disadvantage of unreliable engagement with the lock. Additionally, it requires a large solenoid mechanism with a long stroke, resulting in a bulky and costly design. Another disadvantage is that if excessive torque is applied to the motor shaft, the solenoid mechanism may be damaged, causing the mechanism to malfunction.

[0009] Another solenoid-operable motor lock design is known in which locking occurs when a pin is driven radially relative to the motor shaft within a longitudinal groove of the shaft. An example of this is disclosed in US 2017 / 0170708. An additional disadvantage of this design is that it weakens the motor shaft. This is an additional drawback because the weak motor shaft may break if excessively large torque is applied to the motor shaft.

[0010] In gear wheel locking, for solutions using the aforementioned pin as well as rotating and retaining rings, the electromagnetically operated lock is not necessarily equally effective for rotation in both directions. This can be seen as a disadvantage in the event of a lock malfunction. If the lock is not released, motor rotation is impossible in either direction, and recovery in a fault situation is more difficult.

[0011] One important application area for motor braking or motor locking is linear actuators, particularly spindle and nut-driven linear actuators. These linear actuators often include a drive motor with additional gearing devices beyond the spindle and nut themselves. Such devices are increasingly used, for example, in furniture where a piece of furniture is adjusted to a user-selectable setting and an electric motor is used to maintain that setting during the switch-off. The problem to be solved

[0012] The aforementioned problems, defects, and disadvantages of known electromagnetically operated motor locks are at least partially resolved by a motor locking mechanism comprising an electromechanical transducer as presented below. In particular, the solution found that a remarkably small electromechanical solenoid with a much reduced requirement for stroke length can be deployed to effectively lock in a single direction for rotation. Embodiments illustrate an electromechanical solenoid that moves a non-rotating locking portion in a direction parallel to the motor shaft axis, whereas other embodiments have an electromechanical solenoid that moves a non-rotating locking portion in a direction orthogonal to the motor shaft axis. Meanwhile, by arranging two small electromechanical solenoids with the same reduced stroke length, a bidirectional lock can also be illustrated. means of solving the problem

[0013] A motor comprising a lock mechanism according to the present invention may operate on a rotating locking element, for example, a dedicated locking disk or a dedicated locking sleeve. Cam elements are composed of a locking disk or a locking sleeve. Each cam has a non-engageable side positioned opposite an engageable side. In some embodiments, the non-engageable side is a sloping side and the engageable side is a steep side. The steep side is typically approximately orthogonal to the surface of the locking disk or locking sleeve. This cam design ensures high strength of the cams against shear forces. The cams are durable, and the rotating locking element can be designed to be lighter and smaller than is feasible with conventional cams.

[0014] The motor locking mechanism according to the present invention focuses primarily on locking rotation in only one direction, thereby creating design freedom and reducing costs. This creates a lightweight and reliable unidirectional motor lock, allowing the motor to operate in one direction even in fault situations where the motor shaft is jammed and the lock preventing the motor from rotating in another direction may not be easily released, thereby reversing the direction of rotation to escape the fault situation. Even when a bidirectional embodiment is applied, if a fault situation locks one solenoid mechanism, the other solenoid mechanism can be released by reversing the lock as long as it is not locked or is not affected by the fault and can operate.

[0015] A rotary locking element may be attached to the shaft of a motor, for example, to the output end or the rear end of the motor shaft. In this specification, the output end and the front end are used interchangeably. The same applies to the rear end and the rear end.

[0016] The mass of the elements that move during locking and unlocking is much smaller than in other known designs, and therefore any interfering noise can be ignored. In the motor lock according to the present invention, the small stroke of a diminutive solenoid can be amplified by a pivot arm deflected by a leaf spring, wherein the pivot arm supports a nonrotating locking element at its distal end.

[0017] The electromechanical solenoid comprises a coil. One end of the coil is provided as the coil itself, serving as the base of the solenoid, which is suitably used to secure the solenoid directly or indirectly to the motor housing. On the upper side opposite the coil, a non-rotating locking element is positioned to be displaced by the operation of the solenoid and to engage with a rotating locking element. When locking occurs under load, the two locking elements come into contact, and a lateral force acts on the pivot arm and thereby on the solenoid. Since the force must be able to pivot back and forth between an extended position and a retracted position, it is applied to the pivot arm, which is supported only by the bending of the leaf spring or the hinge. In some embodiments, it is suitable to support the solenoid at a point near the upper side opposite the non-rotating locking element, thereby stabilizing the solenoid against a tilting force. In preferred embodiments, a support at the upper side of the solenoid must support a portion of the pivot arm where the leaf spring is bent or hinged. The support member must be fixed to the motor housing directly or indirectly.

[0018] In one embodiment, the motor locking mechanism includes a torque limiting clutch positioned between the motor shaft and the rotary locking element. The torque limiting clutch essentially anticipates and prevents damage to the locking mechanism, i.e., the rotary locking element, when excessive torque is applied to the motor shaft.

[0019] In its basic form, no arbitrary overload is intended to occur in the rotary locking element in terms of excessive torque. However, it has been found that such torque overload cases can nevertheless occur in certain situations, such as fault situations. One of these fault situations occurs when the locking mechanism is activated while the electric motor is operating. Another overload fault may occur when excessive torque is applied to the motor shaft while the electric motor is already stopped and locked through the locking mechanism. Most critically, an overload situation can be characterized by a sudden impact acting on the rotary locking element.

[0020] Due to the characteristics of small and lightweight components, the motor lock may be damaged. In particular, there may be a risk that the cam of the rotary locking element itself may be damaged, or that the entire structure of the rotary locking element may be damaged, or that the non-rotating locking element may be damaged.

[0021] These problems are solved by the motor locking mechanism of the present invention by placing a torque limiting clutch between the motor shaft and the rotating locking element, thereby basically anticipating and preventing the damage.

[0022] A torque limiting clutch can be introduced at various different positions in relation to two elements: the motor shaft and the rotary locking element:

[0023] Between the inner surface of the cup-shaped or hollow end of the rotary locking element and the outer side of the motor shaft - thereby establishing a clutch integrated with the rotary locking element.

[0024] Between the inside of the cup-shaped or hollow distal end of the motor shaft and the outside of the rotating locking element.

[0025] Between the proximal and distal parts of the motor shaft, a clutch is set at a certain distance from the rotating locking element.

[0026] It is further noted that the rotary locking element on which the torque limiting clutch acts may be either a disc type or a sleeve type as described above.

[0027] Various clutch principles can be applied as follows:

[0028] Piezo crystal electromechanical clutch

[0029] dog clutch

[0030] torque limiter

[0031] centrifugal clutch

[0032] Circlip - Locking Ring Principle

[0033] coil spring having a single turn winding

[0034] Coil spring with multiple turning windings

[0035] When considering a coil spring principle clutch, it should be noted that it is possible to include various materials and dimensions of the wire, which is typically wound spirally. Additionally, the wire can have a cross-sectional shape suitable for circular, rectangular, trapezoidal, elliptical, etc.

[0036] A coil spring torque limiting clutch may include a first end of a coil wire being fixed to a motor shaft or a rotating locking element, and a second end of the coil wire maintaining a free end. Alternatively, the second end of the coil wire may be fixed to the same element to which the first end is fixed to the second end.

[0037] In this specification, the term torque limiting clutch is defined as any active or passive mechanism that serves to limit the torque acting on a rotary locking element to a predetermined maximum value. Embodiments of a torque limiting clutch include any combination of any of the features described above, but are not limited thereto.

[0038] The existence of these and other features distinguishes the current motor locking mechanism from other known electromagnetically operated motor locks.

[0039] The present invention can be further summarized by observing the following examples:

[0040] A linear actuator comprises an electric motor, a spindle driven by said reversible motor, and a spindle nut mounted on the spindle and fixed to rotation, said spindle nut positioned to move between two end positions. The electric motor comprises a rotor including a stator attached to a motor housing and a motor shaft, and the motor is configured to be electrically controlled to selectively rotate the rotor in one of two opposite angular directions. The electric motor further comprises an electromechanical locking mechanism, said electromechanical locking mechanism comprises an electromechanical transducer attached immovably to the motor housing and comprising a non-rotating locking element, said electromechanical transducer is configured to be electrically controlled to selectively displace the non-rotating locking element between a projected position and a retracted position, and the electromechanical locking mechanism also comprises a rotary locking element including at least one cam attached to the motor shaft and projecting toward the transducer, said cam comprising a non-rotating side opposite to a rotatable side. A non-rotating locking element is positioned to protrude toward a rotating locking element and to be interferably locked with at least one cam by optionally engaging with the engageable side of at least one cam. An electromechanical converter is configured to control engagement by maintaining the non-rotating locking element in a position that does not engage with the engageable side of at least one cam when power is supplied to the electromechanical converter, and the electromechanical converter further includes a spring element positioned to maintain the non-rotating locking element in a position that engages with the engageable side of at least one cam when power is not supplied to the electromechanical converter. By this, the electromechanical locking mechanism is configured to lock the motor shaft in one rotational direction, thereby locking the motor in a single direction.

[0041] In an example of a linear actuator, the electromechanical transducer is an electromechanical solenoid comprising a coil and a non-rotating locking element. However, other types of electromechanical transducers may also be used. For example, piezoelectric actuators or microactuators may be mentioned.

[0042] When the motor is locked and under load, the compressive load-holding force is transferred from the rotary locking element to the non-rotating locking element. The pivot arm may form an angle with the surface of the rotary locking element on the side supporting the meshable cam side. This angle may be less than 30 degrees, or less than 15 degrees, or less than 12 degrees, or less than 9 degrees, and, for example, greater than 3 degrees or greater than 6 degrees.

[0043] In an embodiment of a linear actuator, the electromechanical solenoid comprises a pivot arm, the distal end of the pivot arm forms a non-rotating locking element, the pivot arm further comprises an armature configured to be activated by current in a coil, and the spring element comprises a leaf spring configured to deflect the pivot arm toward the rotating element. Due to the gear ratio of the linear actuator, that is, the gear ratio generated by the spindle and the transmission or reduction gear, a strong force applied to the linear actuator, for example in a height-adjustable table, will be reduced to a significantly lower force on the actuator's motor shaft. Thus, even if a heavy load is applied to the actuator, it can be locked by using a locking mechanism having a small electromechanical solenoid that uses a leaf spring as a spring element.

[0044] In an embodiment of a linear actuator, the electromechanical solenoid is executed by a micro-signal relay. In this case, the set of contacts of the relay may be omitted, left unused, or used to provide a feedback signal indicating whether the locking mechanism is locked.

[0045] In an embodiment of a linear actuator, the electromechanical transducer further includes a support member configured to be immovably attached to the housing and to support the electromechanical solenoid against tilting force and shear force. This support member helps ensure that the small electromechanical solenoid, which uses a leaf spring as a spring element, locks sufficiently even when a heavy load is applied to the actuator.

[0046] In an embodiment of a linear actuator, the longitudinal axis of the motor shaft is offset from the longitudinal axis of the solenoid coil.

[0047] In an embodiment of a linear actuator, the longitudinal axis of the motor shaft and the longitudinal axis of the solenoid coil are parallel but do not coincide.

[0048] In an embodiment of a linear actuator, a rotary locking element is formed as a locking disk, and at least one cam is positioned on an otherwise essentially flat side of the disk facing the solenoid, and the disk is positioned near the solenoid such that a non-rotatable locking member engages with the engageable side of at least one cam.

[0049] In an embodiment of a linear actuator, the longitudinal axis of the motor shaft and the longitudinal axis of the solenoid coil are orthogonal.

[0050] In an embodiment of a linear actuator, a rotary locking element is formed as a locking sleeve, at least one cam is positioned on a curved surface of the sleeve, which is otherwise essentially circular, toward the solenoid, and the sleeve is positioned near the solenoid to allow a non-rotary locking member to interact with an engaging side of at least one cam.

[0051] In an embodiment of a linear actuator, a locking mechanism is positioned at the output end of the motor shaft.

[0052] In an embodiment of a linear actuator, the locking mechanism is positioned at the rear end of the motor shaft of the motor.

[0053] In an embodiment of a linear actuator, the motor includes a torque limiting clutch disposed between a rotary locking element and a motor shaft. The torque limiting clutch may be a coil spring having multiple rotary windings, the windings are connected to the motor shaft with a rigid grip, and the free end of the coil spring is attached to a slot within the rotary locking element.

[0054] In one embodiment, the motor includes a rotating member that facilitates the detection of rotation, such as a ring magnet for a Hall sensor or an optical disc for an optical sensor. The rotating member is fixedly positioned on the motor shaft, and at least one rotation sensor, namely a Hall sensor or an optical sensor, is fixed directly or indirectly to the housing.

[0055] In an embodiment of a linear actuator, at least one rotation sensor is mechanically and electrically connected to a printed circuit board, and the printed circuit board is immovably attached to a motor housing.

[0056] In an embodiment of a linear actuator, the printed circuit board also maintains an electromechanical converter and provides an electrical connection thereto.

[0057] In one embodiment, the motor includes a controller configured to receive a signal from at least one rotation sensor, the controller includes a processor, and the controller is configured to perform position, speed, and direction control for the motor. Furthermore, the controller can switch a non-rotating locking element between its protruding position and its retracted position by switching the current to the coil of the solenoid on or off.

[0058] In one embodiment, the electromechanical locking mechanism comprises a rotary locking element including two sets of cams arranged in opposite directions, and two electromechanical transducers, each electromechanical transducer being arranged such that its non-rotating locking element selectively engages with each of the two sets of cams arranged in opposite directions.

[0059] In another embodiment, the exterior of the motor housing exhibits a flat geometric structure and is preferably formed with two parallel planar surfaces on each side, said planar surfaces are connected by arc-shaped surfaces.

[0060] The present invention additionally includes an actuator system comprising a linear actuator as described above, a drive circuit configured to drive an electric motor of the linear actuator, a control box including at least a power supply, and a cable connecting the linear actuator to the drive circuit within the control box.

[0061] In an actuator system comprising a linear actuator mechanism having a spindle and a nut driven by an electric motor according to any one of the embodiments described above, the actuator mechanism is configured for use in a load pattern where the load is generally expected to be in a single direction, such that rotation of the motor shaft in the opposite direction to the expected load requires much more power than rotation in the opposite direction with respect to the expected load. An example of this could be a height-adjustable table with a heavy load placed on top of the table, where the actuator mechanism is configured to raise and lower the table, respectively. In this case, much more power is required to raise the table because the motor can be considered to be operating against the expected load rather than lowering the table which is operating against the expected load. In this situation, the unidirectionality of the locking mechanism ensures that the locking mechanism is configured to lock the motor shaft in the direction (locking direction) relative to rotation, so that the table is lowered, i.e., the motor operates against the expected load. Correspondingly, the locking mechanism is not locked in the opposite direction (non-locking direction), and the motor operates in response to the expected load to raise the table. The present invention also relates to such a height-adjustable table.

[0062] In an embodiment of the present invention, the motor includes a controller and an angle position sensor. The controller includes data collection and data processing capabilities and is configured to determine the angle position, angular velocity, total number of rotations, etc., of the motor shaft using the sensor signal.

[0063] In combination with other operations of the controller, it may be configured to control the timing and switching on or off of a solenoid driving a non-rotating locking element. In an operating phase where the motor is operating in one direction, when the controller instructs the motor to stop while maintaining the load, the controller may be configured to take measures to facilitate the desired motor lock operation. The instruction to stop may be given, for example, by a user pressing a button or by a signal from an external control system.

[0064] According to the present invention, a specific control method may be employed to set and release a motor lock.

[0065] To set the lock, the following may apply:

[0066] While the motor is operating to move a load, and, for example, external intervention from a user or an external control system instructs the controller that the motor must stop, the controller is configured to perform the following: After stopping the motor rotation, the controller may be configured to check the angle position sensor signal for a short, predetermined time interval. The motor is stopped but remains switched on. If the controller is satisfied that no rotation has occurred during the said time interval, the controller is configured to cut off power to the motor, the controller, and the solenoid.

[0067] This displaces the non-rotating locking element of the motor lock to bring the rotating locking element and the locking edge into contact in the shape of a locking disc or locking sleeve, and the sharp protrusion of the locking edge catches the cam on the side that can be engaged, thereby effectively locking the motor against rotation in the locking direction after the motor can be blocked.

[0068] When the lock is released, the appropriate control is determined by the direction of rotation performed after the lock is released. Here, the control depends on whether the desired direction of operation after release is the locking direction or the non-locking direction.

[0069] If the intended direction is the non-locking direction, the control is configured to simply switch on the controller, solenoid, and motor.

[0070] If the intended direction is the locking direction, the controller is configured to switch on the solenoid but does not start rotating the motor in the locking direction. The controller may be configured to operate the motor in the next step to produce a good release of the lock.

[0071] Rotation in the non-locking direction must be sufficient to ensure that the non-rotating locking element can be separated from the cam of the rotating locking element. For example, the number of cams in the locking disk or locking sleeve can determine the minimum rotation by the motor in the non-locking direction. Thus, if the number of cams is n, the minimum rotation executed by the controller can be 1 / n of 360 degrees.

[0072] This action compensates for the movement of the sharp protrusion on the distal end of the leaf spring from the position where it is pressed against the meshable side of the cam. After this initial increment, the controller confirms that the lock has been released and is configured to cause the motor to rotate in the locking direction.

[0073] Accordingly, the following method for operating the actuator mechanism also serves to summarize the present invention:

[0074] In an embodiment, the following applies to a method for operating an actuator comprising an electric motor according to one of the aforementioned embodiments. This method is an operation of stopping and locking the motor while operating the actuator mechanism. This method consists of the following steps:

[0075] Step of moving a load using an actuator mechanism,

[0076] A step of providing a signal to the controller indicating that the motor must stop while the motor is operating to move a load,

[0077] Step of stopping the rotation of an electric motor using electric control,

[0078] A step of continuously checking the angle position sensor signal during a predetermined time interval,

[0079] A step of keeping the motor in a stopped state so that it remains electrically switched on,

[0080] A step of switching off power to the motor, solenoid, and motor control system if the controller determines that no rotation occurs during the above time interval.

[0081] In an embodiment, the following applies to a method for operating an actuator comprising an electric motor according to one of the aforementioned embodiments. This method involves starting by unlocking the motor and then operating the actuator mechanism in the locking direction. This method consists of the following steps:

[0082] A step of providing a signal to an actuator while the power to the motor, motor control system, and solenoid is switched off to start operation in the locking direction, for example, by a user pressing a button or by a signal from an external control system.

[0083] Step of switching on power to the controller.

[0084] The stage where the solenoid is switched on but the motor has not yet started rotating.

[0085] A step of unlocking by using an actuator mechanism that operates gradually in the non-locking direction, wherein the controller rotates the motor at least one revolution in the non-locking direction to unlock it, and confirming whether the locking mechanism has been released.

[0086] A step in which the controller rotates the motor in the locking direction according to this initial increment. Brief explanation of the drawing

[0087] These and other features and advantages of the present invention will become apparent from the following detailed description of the present invention. FIG. 1a is a schematic drawing illustrating an example of a linear actuator. FIG. 1b is a drawing illustrating an example of an actuator system in which a linear actuator is controlled by a control box. FIG. 2a is a partially exploded view of a first embodiment of a motor in a linear actuator according to the present invention. FIG. 2b is a perspective view of a second embodiment of a motor in a linear actuator according to the present invention. FIG. 3 is a perspective view of a rotary locking element. FIG. 4a is a perspective view of an electromechanical solenoid. FIGS. 4B and FIGS. 4C are drawings illustrating additional details of an electromechanical solenoid. FIG. 5 is a side view of the locking mechanism when engaged. FIGS. 6a and FIGS. 6b are a side view and a perspective view of a first embodiment of a motor according to the present invention. FIGS. 7a and FIGS. 7b are a side view and a perspective view of a second embodiment of a motor according to the present invention. FIGS. 8a and 8b are a side view and a perspective view of a third embodiment of a motor according to the present invention based on a first embodiment. FIGS. 9a and 9b are a side view and a perspective view of a fourth embodiment of a motor according to the present invention based on a second embodiment. FIGS. 10 to 13 illustrate a fifth embodiment of an electric motor having a locking mechanism based on a first embodiment including a torque limiting clutch. FIGS. 14 to 18 illustrate a sixth embodiment of an electric motor having a locking mechanism based on a second embodiment including a torque limiting clutch. FIGS. 19 to 22 illustrate a seventh embodiment of an electric motor having a locking mechanism based on the second and sixth embodiments. FIG. 23 is a perspective view of the rear end of a motor according to a first embodiment of the present invention, showing the state in which the motor housing is removed. FIG. 24 is a drawing illustrating a height-adjustable table having linear actuators, wherein the table is loaded by a weight placed thereon. FIGS. 1 through 9 illustrate embodiments of a motor having a worm gear mechanism. This is for illustrative purposes only. The present invention is not limited to a motor driving a specific device. Specific details for implementing the invention

[0088] FIG. 1a is a schematic diagram illustrating an example of a linear actuator (1). The linear actuator (1) comprises an electric motor (10), a transmission or reduction gear (3) typically having multiple stages, a spindle (4) having a thread (5), a spindle nut (6) engaging with the thread (5), and a tube-shaped activation element (7). A mounting bracket (8) is provided at the end of the activation element (7) for mounting the linear actuator (1) to a carrying element, for example. The spindle nut (6) is fixed indirectly or directly to rotation. In some linear actuators, the spindle nut is connected directly to the carrying element, for example, without the use of an activation element. When the spindle (4) is rotated by the motor (10), the spindle nut (6) moves along the spindle (4) and thus converts rotation between two end positions into linear motion of the spindle nut (6) and / or the activation element (7). Furthermore, the linear actuator (1) includes an electromechanical locking mechanism (40) placed in the motor (10). This locking mechanism will be described in more detail below. For some motor types, the electric motor (10) can drive the spindle (4) directly, so the transmission (3) can be avoided. Although other types of electric motors may be used, the electric motor (10) is typically a reversible electric DC motor.

[0089] Typically, linear actuators are used in actuator systems controlled by a control box. An example of such an actuator system (9) is illustrated in FIG. 1B. A linear actuator (1) is connected to a control box (13) via a cable (12), and the control box (13) includes at least a power supply (14), a controller (15), and a drive circuit (16) for the linear actuator (1). The drive circuit (16), and also the electric motor (10) of the actuator (1), are controlled by a control signal from the controller (15). Typically, the controller (15) includes a microcomputer. The control box (13) is generally placed in the equipment where the linear actuator (1) is used. These devices may represent any one of several different applications, such as trucks, agricultural machinery, industrial automation equipment, hospital and nursing beds, leisure beds and chairs, tables or other height-adjustable furniture products, and various other similar applications. The power supply (14) is typically connected to a mains AC supply net having a power cable (17). Furthermore, the control box (13) is connected to a remote control (18) to allow the operation of the linear actuator (1) to be controlled by a person near the actuator. The connection between the remote control (18) and the control box (13) may be a wired connection as shown in FIG. 1b, but a wireless communication system such as a wireless link or an infrared link may also be used. The control box may also be configured to control an actuator system having multiple linear actuators. The control box then includes a drive circuit for each linear actuator. Each drive circuit, and also the electric motors of the actuators, are individually controlled by control signals from the controller, which means that some or all of the actuator motors can operate simultaneously.

[0090] FIG. 2a is a partially exploded view illustrating a first embodiment of a motor (10) having a locking mechanism (40) in a linear actuator according to the present invention.

[0091] An electromechanical locking mechanism (40) is installed in the electric motor (10), and the motor (10) includes a stator and a rotor (not shown). The stator is attached to a motor housing (20). The motor housing (20) includes a slender, elongated housing portion, and its exterior is formed of, for example, a flat geometric shape and two parallel planar surfaces (26), which are shown connected by arc-shaped surfaces (24, 25) on each side. A motor (10) having such a flat external geometric shape may be desirable in places where space is constrained, for example, as in a linear actuator. The motor housing (20) further includes a rear housing portion (22) and an end cover (23).

[0092] The rotor includes a motor shaft (31), and at one end the motor shaft (31) includes a protrusion at the front end configured to act as an output end (not shown). In the example of FIG. 2a, the output end is connected to drive the worm of the worm gear mechanism (11). The motor shaft (31) is supported by a bearing (34) at the rear end (32).

[0093] The motor (10) is configured to be electrically controlled to selectively switch between clockwise rotation and counterclockwise rotation.

[0094] The locking mechanism (40) includes an electromechanical solenoid (41) that is immovably attached to the motor housing (20, 22, 23). The electromechanical solenoid (41) is an electromechanical transducer comprising a coil (42) and a pivot arm (43). Hereinafter, the electromechanical solenoid may also be simply referred to as a solenoid. It should be noted that other forms of electromechanical transducers may also be used instead of the electromechanical solenoid (41).

[0095] The locking mechanism (40) further includes a rotating locking element (45), and in this embodiment, is shown as a disc-shaped locking element attached directly or indirectly to the motor shaft (31).

[0096] The locking mechanism (40) further includes a nonrotating locking element (44), FIG. 2a illustrates a rotating locking element (45) and a nonrotating locking element (44) arranged to engage, and this engagement can be selectively controlled by a solenoid (41).

[0097] The motor shaft (31) includes a longitudinal axis (33). The solenoid (41) includes a coil (42), and the solenoid coil (42) includes a longitudinal axis (53). In the embodiment of FIG. 2a, the motor (10) is illustrated such that the motor shaft longitudinal axis (33) is parallel to but does not coincide with the coil longitudinal axis (53). By this, the two axes are offset from each other.

[0098] The rotary locking element (45) includes a longitudinal axis (48). As shown in FIG. 2a, the longitudinal axis (33) of the motor shaft (31) and the longitudinal axis (48) of the rotary locking element (45) coincide. The rotary locking element (45) rotates together with the motor shaft (31), and their rotational motions are identical.

[0099] FIG. 2a further illustrates a motor (10), wherein a rotary locking element (45) comprises at least one cam (47) (three cams are shown) protruding in a direction toward a solenoid (41), and a non-rotating locking element (44) of a pivot arm (43) protrudes in a direction toward the rotary locking element (45). The non-rotating locking element (44) is positioned to enter a locking position when engaged with at least one cam (47). This is possible when the current to the coil of the solenoid (41) is switched off.

[0100] The rotation locking element (45) includes a surface (49) facing the pivot arm (43).

[0101] FIG. 2a further illustrates that the base of the solenoid (41) is fixed to a printed circuit board (50) and subsequently fixed to a rear housing portion (22). The non-rotating locking element (44) is supported by a support member (27) on the upper side opposite the coil, thereby stabilizing the solenoid (41) against tilting force and shearing force. The support member (27) is positioned to support the pivot arm (43) at the hinged end. The support member (27) is formed as an integral part of the end cover (23).

[0102] In an embodiment of the electric motor (10) of a linear actuator according to the present invention illustrated in FIG. 2a, it can be seen that the motor (10) includes a rotating member (51) that facilitates the detection of rotation. The rotating member (51) is positioned on a motor shaft (31) and rotates together with the motor shaft. The rotating member (51) may be various configurations, such as a ring magnet for a Hall sensor or an optical disc for an optical sensor. The electric motor (10) further includes at least one rotation sensor (52), such as a Hall sensor or an optical sensor, and the sensor (52) is fixed directly or indirectly to a housing. FIG. 2a illustrates two Hall sensors that may be desirable in some applications.

[0103] At least one rotation sensor (52) is mechanically and electrically connected to a printed circuit board (50), which is fixed directly or indirectly to a housing (20, 22, 23), and the printed circuit board (50) also holds a solenoid (41) and provides an electrical connection to this solenoid. Nevertheless, this is not the only option. It is equally possible for the rotation sensor (52) and the solenoid (41) to be attached and connected independently.

[0104] FIG. 2b illustrates a second embodiment of the present invention in which a rotary locking element of a locking mechanism (60) is formed as a locking sleeve (63), wherein at least one cam (61) (four cams are shown) is positioned on a surface (62) of the sleeve that is otherwise essentially circularly curved toward a solenoid (64). The locking sleeve (63) is positioned near the solenoid (64) so ​​that a non-rotatable locking element (65) interacts with an engaging side (66) of at least one cam (61).

[0105] The second embodiment further includes an end cover not shown in FIG. 2b.

[0106] The motor shaft (31) includes a longitudinal axis. The solenoid (64) includes a coil, and the solenoid coil includes a longitudinal axis. In the embodiment of FIG. 2, the electric motor (10) is illustrated such that the motor shaft longitudinal axis is orthogonal to the coil longitudinal axis. Thus, the two axes are offset from each other.

[0107] Referring to the first embodiment of FIG. 2a, FIG. 3 illustrates a rotating locking element (45) formed as a locking disk, wherein at least one cam (47) (three cams are shown) is positioned on the otherwise essentially flat side of the disk toward the solenoid (41). The locking disk (45) is positioned near the solenoid (41) so that a non-rotating locking member (44) interacts with the steep side of the cams (47).

[0108] FIG. 3 illustrates that each cam (47) has an engageable side (76) (illustrated as a steep side) and a non-engageable side (75) (illustrated as a slanted side) opposite it, with the steep side being approximately orthogonal to the surface of the rotational locking element (45). The engageable side may also have other forms that can be locked with the non-rotational locking member (44). The non-engageable side (75) cannot be engaged because it is located at a point away from the non-rotational locking member (44). This does not require a slant. It is equally non-engageable even without a slant. As described below, there is an arrangement and angle of pivot arms that make the non-engageable side (75) non-engageable. FIG. 3 illustrates that the rotary locking element is designed with a small size and reduced weight compared to conventional cams, but with high strength in mind, and this strength is achieved by designing a non-interlockable side (75) with a large installation area.

[0109] The electric motor (10) is lockable in a single direction for rotation using a locking mechanism (40) and is locked only in one of the rotational directions, either clockwise or counterclockwise. This is achieved by adjusting the topographical configuration of a ring-shaped area (46) placed on the surface of a rotational locking element (45), which is when rotation is attempted only in one of the rotational directions in which the topography of the ring-shaped area (46) engages lockably with a non-rotational locking element (44).

[0110] The rotary locking element (45) includes the rotation axis (48) shown in FIG. 2a.

[0111] The locking mechanism (40) of the first embodiment comprises an electromechanical solenoid (41) immovably attached to a motor housing (20, 22, 23) as shown in FIG. 4a, wherein the solenoid (41) comprises a coil (42), a yoke (72) which may be formed from an angular bracket, and a movable armature (74) in the form of a pivot arm (43). Further detailed description of an example of the electromechanical solenoid (41) is shown in FIG. 4b and FIG. 4c.

[0112] The armature (74) will be made of a magnetic material. The pivot arm (43) supports a non-rotating locking element (44) formed at the distal end of the armature (74). The armature (74) is hinged to the yoke (72) and held in place by a leaf spring (73) attached to the yoke (72) and bent approximately 90 degrees, so that when power is not supplied to the electromechanical solenoid (41), the pivot arm (43) and thus the non-rotating locking element (44) remain in their protruding position. This situation is illustrated in FIG. 4b. When current passes through the coil (42), it generates a magnetic field that activates the armature (74) by pulling the armature toward the coil (42) with a magnetic force exceeding the force provided by the leaf spring (73). This means that the pivot arm (43) and thus the non-rotating locking element (44) move to their retracted position. This situation is illustrated in FIG. 4c. When the current through the coil is cut off again, the pivot arm (43) returns to its protruding position by the force provided by the leaf spring (73).

[0113] For example, due to the gear ratio of the linear actuator caused by the spindle (4) as well as the transmission or reduction gear (3), the strong force applied to the linear actuator, for example in a height-adjustable table, is reduced to a significantly lower force on the actuator's motor shaft. Therefore, even when a heavy load is applied to the actuator, the actuator can be locked using a locking mechanism having a small electromechanical solenoid, as shown in FIGS. 4a and 4b, using a leaf spring (73) as a spring element.

[0114] In one embodiment, the electromechanical solenoid may therefore be executed by a micro-signal relay. In this case, the set of contacts of the relay may be omitted, left unused, or used to provide a feedback signal indicating whether the locking mechanism is locked. As an example of such a feedback signal, power may be supplied to the coil when the locking mechanism is to be released after being locked. However, the non-rotating locking element may be pressed upward against the engagementable side of the cam and thus present difficulties during separation. In this case, the relay contacts will indicate that the non-rotating locking element is still in its protruding position even when power is supplied to the coil, and the motor may be controlled to rotate gradually in the non-locking direction to release the lock before the intended rotation in the locking direction begins. As another example, it may be mentioned that when power is not supplied to the coil and thus the non-rotating locking element is in its protruding and locked position, the relay contacts may be connected (i.e., short-circuited) to the motor terminals. This increases the cogging torque of the motor, so that in the event of a mechanical defect in the rotating locking element, for example, the final speed of the motor in the locking direction will be reduced at least.

[0115] The solenoid (41) is configured to be electrically controlled to selectively switch the non-rotating locking element (44) between an extended position and a retracted position, as indicated by the dotted line 35. When power is not supplied to the electromechanical solenoid (41, 64), the spring element or leaf spring (73) holds the pivot arm (43), and thus the non-rotating locking element (44) engages with the rotating locking element (45, 63) in its extended position. Thus, when no current flows through the winding of the coil (42), the non-rotating locking element takes its extended position.

[0116] When the coil (42) is magnetized by an electric current, the plate spring (73) and the pivot arm (43) are elastically bent toward the coil (42), thereby moving the armature (74) closer to the coil (42), and the non-rotating locking element (44) is placed in its contracted position.

[0117] FIG. 5 illustrates the engagement principle between a rotary locking element (45) (shown as a disk) and a non-rotating locking element (44) in a first embodiment of the present invention. In the drawing, the current to the solenoid is cut off and the pivot arm (43) is in its protruding position.

[0118] FIG. 5 further illustrates that the non-rotating locking element (44) is the distal end of the armature (74).

[0119] The armature (74) of the pivot arm (43) is supported against tilting force and shear force by a support member (27) (see FIG. 2a) that is immovably attached to the housing (20, 22, 23) at a point (78).

[0120] In FIG. 5, reference numeral 77 indicates the engagement point between the rotating locking element (45) and the non-rotating locking element (44). If an external load is applied to attempt to rotate the disk (45) to the right in the direction of the moving point (77) as can be seen in the drawing, this will be effectively prevented by the engagement between the pivot arm (43) and the engageable side (76) of the cam (47).

[0121] However, if an external load attempts to rotate the rotating locking element or disk (45) to the left in the direction of the point (77) moving as can be seen in the drawing, this is possible even if the pivot arm (43) is in its protruding position. The pivot arm (43) and the corresponding non-rotating locking element (44) will slide past the cams due to the flexibility of the pivot arm (43), provided that the external load is sufficiently large.

[0122] FIG. 5 further illustrates that in a protruding position, the armature (74) of the pivot arm (43) contacts the interlockable side (76) (see FIG. 3) of the cam (47), where the armature (74) forms an angle (79) with the lower side of the rotary locking element (45). The locking and load-holding force is transmitted as a compressive force to the armature (74) of the pivot arm (43) and subsequently to the support member (27) (see FIG. 2a).

[0123] Similarly, in the second embodiment according to FIG. 2b, the cams (62) are on a curved surface, and the tangents touching them at the position of the engagementable side (61) of the cam will also form an angle with the armature (74) of the pivot arm when positioned in an arrangement similar to that shown in FIG. 5. In FIG. 2b, when the rotary locking element (63) is formed as a sleeve and the longitudinal axis of the solenoid coil is orthogonal to the longitudinal axis of the motor shaft (31), the locking and load-holding force is also transmitted as a compressive force to the armature of the pivot arm.

[0124] Generally, in the embodiments illustrated in FIG. 2b and FIG. 5, the load-holding force is a force transmitted from a rotating locking element to a non-rotating locking element.

[0125] It is a feature of the present invention that the angle (79) is, for example, less than 30 degrees, or less than 15 degrees, or less than 12 degrees, or less than 9 degrees, and, for example, greater than 3 degrees or greater than 6 degrees. Keeping the angle (79) small has the advantage that the solenoid is positioned very close to the rotary locking element (45). This makes it possible to construct a compact motor lock. Positioning the motor lock at such a small angle (79) further ensures the unidirectionality of the locking action.

[0126] FIGS. 6 through 9 illustrate four configurations of electromechanical locking mechanisms according to the present invention. These vary depending on the selection of the rotary locking element and the selection of where the motor end is positioned. FIGS. 6a and 6b illustrate a first embodiment of an electromechanical locking mechanism having a disc element positioned at the rear end (71). FIGS. 7a and 7b illustrate a second embodiment of an electromechanical locking mechanism having a sleeve element positioned at the rear end (71). FIGS. 8a and 8b illustrate a third embodiment of an electromechanical locking mechanism based on the first embodiment having a disc element positioned at the output end (70). FIGS. 9a and 9b illustrate a fourth embodiment of an electromechanical locking mechanism based on the second embodiment having a sleeve element positioned at the output end (70).

[0127] In another embodiment of the electromechanical locking mechanism according to the present invention, the motor includes a torque limiting clutch disposed between the motor shaft and the rotary locking element.

[0128] Additional embodiments will be described below: Generally, any overload in terms of excessive torque is not intended to occur in the rotary locking element (45, 63). Nevertheless, it is known that such torque overload cases occur in certain situations, such as fault situations. Such fault situations may occur when the locking mechanism (40, 60) is activated while the electric motor (10) is operating. Another overload fault may be when excessive torque is applied to the motor shaft (31) while the electric motor (10) is already stopped and locked through the locking mechanism (40, 60). Most importantly, the overload situation may be of a nature such as a sudden impact acting on the rotary locking element (45, 63).

[0129] Due to the characteristics of small and lightweight components, the locking mechanism (40, 60) may be damaged. In particular, there may be a risk of damaging the cam of the rotating locking element (45, 63) itself, damaging the entire structure of the rotating locking element (45, 63), or damaging the non-rotating locking element (44).

[0130] FIGS. 10 through 13 illustrate a fifth embodiment based on an electromechanical locking mechanism of the first or fourth embodiment, wherein the locking mechanism (40, 60) comprises a torque limiting clutch in the form of a coil spring having multiple turns winding (36) disposed between a motor shaft (31) and a rotary locking element (45). To simplify the illustration of the invention, the worm gear mechanism (11) and the motor housing (22, 23) are not illustrated.

[0131] In the fifth embodiment, the locking mechanism (40, 60) operates as described in the first embodiment. A torque limiting clutch in the form of a coil spring (36) is positioned between the inner surface of the cup-shaped or hollow end (38) of the rotary locking element (45, 63) and the outer side of the motor shaft (31), thereby establishing a clutch integrated with the rotary locking element (45). The free end (37) of the coil spring (36) is seated in the slot (39) of the rotary locking element (45, 63). The coil spring (36) is connected to the motor shaft (31) with its winding, for example, with a tight grip, so that when the non-rotating locking element (44) is in a retracted position, the rotary locking element (45, 63) rotates together with the motor shaft (31). As shown in FIG. 12, the rotary locking element (45, 63) surrounds a part of the motor shaft (31) but can rotate relative to it and is therefore connected to the drive through the coil spring (36).

[0132] In normal operation, the coil spring (36) will not slide on the motor shaft (31). The grip of the coil spring is adjusted to be strong enough to prevent such sliding from occurring. The friction between the coil spring (36) and the motor shaft (31) is large enough to prevent any sliding during normal operation.

[0133] In the case of a fault, if an excessively large torque is applied to the rotating locking element (45, 63), this torque will cause sliding between the coil spring (36) and the motor shaft (31). Therefore, the torque limiting clutch basically anticipates and prevents damage to the locking mechanism (40, 60).

[0134] When the non-rotating locking element (44) is in a protruding position, the rotating locking element (45, 63) is maintained in a non-rotating position, that is, maintained against rotation. The same applies to the motor shaft (31) maintained against rotation through the rotating locking element (45, 63), thereby locking the electric motor (10) in a single direction, either clockwise or counterclockwise.

[0135] FIGS. 14 to 18 illustrate a sixth embodiment based on an electromechanical locking mechanism of the second or third embodiment, wherein the locking mechanism (40, 60) comprises a torque limiting clutch in the form of a coil spring (67) disposed between a motor shaft (31) and a rotary locking element (63). The locking mechanism (40, 60) may be covered by a housing (28) as shown in FIG. 14.

[0136] In the sixth embodiment, the locking mechanism (40, 60) operates as described in the first and second embodiments. A torque limiting clutch in the form of a coil spring (67) is positioned between the inner surface of the cup-shaped or hollow end (68) of the rotary locking element (63) and the outer side of the motor shaft (31), thereby establishing a clutch integrated with the rotary locking element (63). The free end (69) of the coil spring (67) is seated in the slot (39) of the rotary locking element (63). The coil spring (67) is connected to the motor shaft (31) with its winding, for example, with a firm grip, so that when the non-rotating locking element (65) is in a retracted position, the rotary locking element (63) rotates together with the motor shaft (31). As shown in FIG. 18, the rotary locking element (63) surrounds a part of the motor shaft (31) but can rotate against it and is therefore connected to the drive through the coil spring (63).

[0137] When the non-rotating locking element (65) is in a protruding position as shown in FIG. 17, the rotating locking element (63) is maintained in a non-rotating position, that is, maintained against rotation. The same applies to the motor shaft (31) maintained against rotation through the rotating locking element (63), thereby locking the electric motor (10) in a single direction, either clockwise or counterclockwise.

[0138] The sixth embodiment of the electric motor (10) can anticipate and prevent damage to the locking mechanism (40, 60) in a manner similar to that described in the fifth embodiment when excessive force is applied to the motor shaft (31).

[0139] FIGS. 19 through 22 illustrate a seventh embodiment based on the electromechanical locking mechanism of the second and sixth embodiments. In the seventh embodiment, the electromechanical locking mechanism is bidirectional. For the sake of illustration, only the motor shaft (31) of the electric motor and the electromechanical locking mechanism (90) are illustrated.

[0140] The locking mechanism (90) has a rotary locking element (91) embodied as a locking sleeve having two rows of cams arranged in opposite directions. This means that one row of cams has a side that can be engaged toward a clockwise rotational direction and the other side that can be engaged toward a counterclockwise rotational direction. Each row of cams includes four cams. The locking mechanism (90) includes two solenoids (92, 93), both of which are attached to the same printed circuit board (94) but are attached to opposite sides of each. Each of the two solenoids (92, 93) has a non-rotating locking element (95, 96) connected thereto. The non-rotating locking element (95, 96) is positioned to engage with the engageable sides (97, 98) of the cams (99, 100) as in the embodiments described above. FIGS. 21 and 22 illustrate both the engaging sides (97, 98) and the non-engaging sides (101, 102) of each cam (99, 100) belonging to one of the cam rows. The planes of each engaging side (97, 98) face each other but are not in the same plane. The engaging sides (97, 98) of the two rows of cams are positioned in relation to the non-rotating locking elements (95, 96) of each solenoid, so that when one of the non-rotating locking elements (95, 96) engages with the engaging sides (101, 102) of the cams of the corresponding row, the angular positions of the rotating locking element (91) are different from the corresponding positions for the other non-rotating locking element. This is to prevent both non-rotating locking elements from being under load simultaneously. It is confirmed that arranging the cams in this manner is always possible by reversing them to release at least one of the rotation directions.

[0141] The locking mechanism (90) also includes a coil spring (103) of a cup-shaped or hollow end (104) of a rotary locking element (91). The coil spring (103) has two free ends (104, 105) rotatably displaceable in a slot within the rotary locking element (91).

[0142] When the non-rotating locking elements (95, 96) are in a protruding position and thereby engage with the interlockable sides (97, 98) of the cams (99, 100), the rotating locking element (91) is maintained in a non-rotating position, that is, maintained against rotation. The same applies to the motor shaft (31) maintained against rotation through the rotating locking element (91), thereby locking the electric motor (10) in both clockwise and counterclockwise directions.

[0143] In principle, the locking mechanism (90) locks the electric motor (10) in only one direction because the load on the motor shaft may be either clockwise or counterclockwise. Depending on the situation, the load on the motor shaft (31) is displaced, for example, from clockwise to counterclockwise. In this situation, the locking mechanism (90) can lock the electric motor.

[0144] An electric motor having a locking mechanism (90) may also experience the aforementioned fault situation in which an excessive load is applied to the non-rotating locking element (91). In this situation, the winding of the coil spring (103) will slide against the motor shaft (31) as described above and will apply frictional force to the motor shaft (31) when the motor shaft rotates. Again, this essentially prevents and avoids damage to the locking mechanism (90).

[0145] FIG. 23 includes a controller (81) configured to receive a signal (82) from at least one rotation sensor (83) for an electric motor (80), and the controller includes a processor (84), and the controller can perform position, speed, and direction control for the electric motor. Furthermore, the controller can switch the locking mechanism (85) on or off by switching the current to the coil (86) on or off.

[0146] FIG. 24 illustrates a table comprising an actuator mechanism (90) driven by an electric motor (10). The actuator mechanism is suitable for raising and lowering the table, and rotation of the motor shaft against the expected load (thereby raising the table) requires much more power than rotation in the opposite direction against the expected load (lowering the table). In the case of the first through sixth embodiments of the locking mechanism, the unidirectionality of the locking mechanism (40, 60) indicates by itself that it is suitable for locking against rotation in the direction in which the weight pushes the table downward.

[0147] In particular, FIG. 24 illustrates one possible embodiment of an actuator mechanism (110) and includes a motor (10) that drives the actuator, which is a linear actuator operating according to the nut and spindle principle. The load (111) is illustrated in the form of a weight that is raised and lowered. The loading pattern of the actuator is configured to controllably raise or lower the weight by converting the rotation of the motor in a known manner into motion that extends or contracts the length of the linear actuator. In this case, when the motor (10) rotates relative to the load, the weight moves upward. When the motor rotates relative to the load, the weight moves downward. Therefore, much more power is required to move the weight upward than to move it downward. The locking mechanism (40, 60) of the motor (10) has a unidirectional feature that operates only in the direction in which the motor locks, thereby turning off the power to the motor and keeping the actuator mechanism (90) from moving downward when locked.

[0148] If the current to the locking mechanism is unintentionally interrupted, a fault situation may occur. If such an interruption occurs while the table is descending, the solenoid loses magnetization, and as a result, the non-rotating locking element suddenly comes into contact with the rotating locking element. The rotation of the rotating locking element stops immediately. Due to the inertia of the table, the locking mechanism may be damaged if the impact is large. For example, if the non-rotating or rotating locking element breaks, the table may continue to descend at an uncontrollably increased speed. The presence of a torque limiting clutch (36) will cause sliding to occur between the clutch (36) and the motor shaft (31) when properly regulated. This will protect the locking mechanism from breaking. Instead, the table may continue to descend at a much reduced speed, or the table may actually be braked or stopped in a fault situation. Explanation of the symbols

[0149] 1: Linear actuator 4: Spindle 6: Spindle nut 9: Actuator system 10: Electric motor 13: Control box 14: Power 15: Controller 16: Driving circuit 17: Power cable 18: Remote control 20, 22, 23: Motor housing 27: Support member 31: Motor shaft 36, 67: Multi-turn winding 37, 69: Free end 39: Slot 40, 60: Electromechanical locking mechanism 41, 64, 92, 93: Electromechanical transducers 42, 86: Coils 43: Pivot arm 44: Non-rotating locking element 45, 63, 91: Rotational locking elements 47, 61: Cams 73: Leaf spring

Claims

Claim 1 Electric motor (10); spindle (4) driven by the electric motor (10); A linear actuator (1) comprising: a spindle nut (6) mounted on the spindle (4) and fixed to rotation, wherein the spindle nut (6) is positioned to move between two end positions; wherein the electric motor (10) comprises a rotor comprising a stator and a motor shaft (31) attached to a motor housing (20); wherein the electric motor (10) is configured to be electrically controlled to selectively rotate the rotor in one of two opposite angular directions; wherein the electric motor further comprises an electromechanical locking mechanism (40, 60), wherein the electromechanical locking mechanism (40, 60) is an electromechanical transducer (41, 64) that is immovably attached to the motor housing (20) and comprises a nonrotating locking element (44), wherein the electromechanical transducer (41, 64) 64) comprises the electromechanical transducer (41, 64) configured to be electrically controlled to selectively shift the non-rotating locking element (44) between a projected position and a retracted position, and the rotating locking element (45, 63) comprising at least one cam (47, 61) attached to the motor shaft (31) and protruding in a direction toward the electromechanical transducer (41, 64), wherein the at least one cam (47, 61) comprises a non-engageable side opposite to an engageable side, and the non-rotating locking element (44) comprises the rotating locking element (45,63) is positioned to protrude in a direction toward and selectively engage with the engageable side of the at least one cam (47, 61) to interferentially lock with the at least one cam (47, 61), and the electromechanical converter (41, 64) is configured to control the engagement by maintaining the non-rotating locking element (44) in a position not engaged with the engageable side of the at least one cam (47, 61) when power is supplied to the electromechanical converter (41, 64), and the electromechanical converter (41, 64) further includes a spring element positioned to maintain the non-rotating locking element (44) in a position engaged with the engageable side of the at least one cam (47, 61) when power is not supplied to the electromechanical converter (41, 64), thereby the electromechanical locking mechanism (40, 60) [regarding] rotation of the motor shaft (31) A linear actuator configured to lock in a rotational direction, thereby locking the electric motor (10) in a unidirectional manner. Claim 2 A linear actuator according to claim 1, characterized in that the electromechanical converter (41, 64) is an electromechanical solenoid comprising a coil (42, 86) and a non-rotating locking element (44). Claim 3 A linear actuator according to claim 2, wherein the electromechanical solenoid comprises a pivot arm (43), the distal end of the pivot arm (43) forms the non-rotating locking element (44), the pivot arm further comprises an armature (74) configured to be activated by current in the coil (42, 86), and the spring element comprises a leaf spring (73) configured to deflect the pivot arm (43) toward the rotating locking element (45, 63). Claim 4 A linear actuator according to claim 2, characterized in that the electromechanical solenoid is executed by a subminiature signal relay. Claim 5 A linear actuator according to claim 2, wherein the electromechanical converter (41, 64) further comprises a support member (27) that is immovably attached to the housing (20) and configured to support the electromechanical solenoid against tilting force and shearing force. Claim 6 A linear actuator according to claim 2, wherein the rotary locking element (45) is formed as a locking disk. Claim 7 A linear actuator according to claim 6, characterized in that the longitudinal axis (33) of the motor shaft (31) and the longitudinal axis (48) of the coil (42) are parallel but do not coincide. Claim 8 A linear actuator according to claim 2, wherein the rotary locking element (45, 63) is formed as a locking sleeve. Claim 9 A linear actuator according to claim 8, characterized in that the longitudinal axis (33) of the motor shaft (31) and the longitudinal axis of the coil (42) are orthogonal. Claim 10 A linear actuator according to claim 1, characterized in that the motor includes a torque limiting clutch disposed between the rotary locking element (45, 63) and the motor shaft (31). Claim 11 A linear actuator according to claim 10, wherein the torque limiting clutch is a coil spring having multiple turns windings (36, 67), the windings (36, 67) are connected to the motor shaft (31) with a tight grip, and the free end (37, 69) of the coil spring is attached to a slot (39) within the rotary locking element (45, 63). Claim 12 A linear actuator according to claim 1, comprising a rotating member that facilitates the detection of rotation, wherein the rotating member is fixedly disposed on the motor shaft and comprises at least one rotation sensor, wherein the sensor is fixed directly or indirectly to a housing. Claim 13 A linear actuator according to claim 12, wherein the motor comprises a printed circuit board immovably attached to the motor housing, and the at least one rotation sensor is mechanically and electrically connected to the printed circuit board. Claim 14 A linear actuator according to claim 13, wherein the printed circuit board also retains the electromechanical converter (41, 64) and provides an electrical connection thereto. Claim 15 A linear actuator according to claim 12, comprising a controller configured to receive a signal from at least one rotation sensor, wherein the controller comprises a processor, wherein the controller is configured to perform position, speed, and direction control for a motor, and wherein the controller is further configured to switch the non-rotation locking element between its protruding position and its retracted position by switching the current to the coil on or off. Claim 16 A linear actuator according to claim 1, wherein the electromechanical locking mechanism comprises a rotary locking element (91) comprising two sets of cams arranged in opposite directions, and two electromechanical transducers (92, 93), each of which is arranged such that its non-rotating locking element selectively engages with each of the two sets of cams arranged in opposite directions. Claim 17 An actuator system (9) comprising: a linear actuator (1) according to any one of claims 1 to 16; a control box (13) comprising a driving circuit (16) configured to drive an electric motor (10) of the linear actuator (1) and at least one power source (14); and a cable (12) connecting the linear actuator (1) to the driving circuit (16) within the control box (13). Claim 18 A height-adjustable table comprising an actuator system (9) according to paragraph 17.

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