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Title:
LINEAR ACTUATOR
Document Type and Number:
WIPO Patent Application WO/2019/001654
Kind Code:
A1
Abstract:
A linear actuator comprising a console, an outer tube connected to the console, an electric motor, a transmission, and a spindle connected to the electric motor via the transmission, a spindle nut on the spindle, an inner tube connected to the spindle nut, and where the electric motor is connected to the console. The object underlying the invention is to provide a linear actuator which can be assembled in a simple manner. This object is solved with a linear actuator according to the preamble of claim 1, where the console comprises openings (21,22) and the electric motor comprises fingers (27, 28, 29), and where the fingers engage with the openings to secure the electric motor to the console.

Inventors:
KNUDSEN MARTIN (DK)
SØRENSEN RENÉ (DK)
Application Number:
DK2018/000030
Publication Date:
January 03, 2019
Filing Date:
June 28, 2018
Export Citation:
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Assignee:
LINAK AS (DK)
International Classes:
F16H25/20; H02K7/06
Foreign References:
US20100139429A12010-06-10
US20030121676A12003-07-03
US20170056579A12017-03-02
US20110018371A12011-01-27
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Claims:
Claims

1 . Linear actuator (1 ) comprising a console (2), an outer tube (3) connected to the console (2), an electric motor (7), a transmission (14), and a spindle (13) in connection with the transmission (14), a spindle nut (16) on the spindle (13) connected to the electric motor (7) via the transmission (14), an inner tube (4) connected to the spindle nut (16), and where the electric motor (7) is connected to the console (2), characterized in that the console (2) comprises openings (21 ,22) and that the electric motor (7) comprises fingers (27,28,29), and where the fingers (27,28,29) engage the openings (21 ,22) to secure the electric motor (7) to the console (2).

2. Linear actuator according to claim 1 , characterized in that the fingers (27,28,29) protrudes out of the openings (21 ,22), and that a free end of the fingers (27,28,29) is bent.

3. Linear actuator according to claim 1 , characterized in that at least one finger (28) comprises a first section (30) parallel to an axis of rotation of the electric motor (7) and a second section (31 ) extending in circumferential direction around the axis, and where the second section (31 ) is bent relatively to the first section (19).

4. Linear actuator according to claim 3, characterized in that the second section (31 ) comprises a width measured along the axis of rotation of the electric motor (7) which is increasing in a direction towards the first section (30).

5. Linear actuator according to claim 4, characterized in that the second section (31 ) comprises a lower edge (33) in contact with the console (2), where the lower edge (33) is inclined in a direction towards the first section (30).

6. Linear actuator according to any of claims 2 to 5, characterized in that at least two fingers (27,28) are provided and where the two fingers (27,28) have second sections (31 ) extending in opposite directions in the circumferential direction.

7. Linear actuator according to claim 6, characterized in that the two fingers (27,28) are arranged symmetrically with respect to a plane through the axis of rotation of the electric motor (7).

8. Linear actuator according to any of claims 1 to 7, characterized in that at least three fingers (27,28,29) are provided.

9. Linear actuator according to claim 8, characterized in that the fingers (27,28,29) are distributed evenly in the circumferential direction.

10. Linear actuator according to any of claims 1 to 9, characterized in that the electric motor (7) comprises a motor housing (26) made of a sheet- metal and the fingers (27,28,29) constitute a part of the motor housing (26).

Description:
Linear actuator

The present invention relates to a linear actuator comprising a console, an outer tube connected to the console, an electric motor, a transmission, and a spindle in connection with the transmission, a spindle nut on the spindle, an inner tube connected to the spindle nut, and where the electric motor is connected to the console.

When the linear actuator is assembled, the electric motor should be fixedly connected to the console, which according to prior art linear actuators, is done by means of screws. To this end, the electric motor and the console should be equipped with threaded holes and corresponding screw holes, respectively. In order to connect the two parts, the screw holes of the console must be aligned with the threaded holes of the electric motor. Upon alignment, a screw must be inserted and tightened in each of the aligned holes. An electric motor is typically connected to a console by means of three screws. This makes assembly of the linear actuator rather complicated, time consuming and thus costly.

The object underlying the invention is to provide a linear actuator which can be assembled in a simpler manner.

This object is achieved with a linear actuator according to the preamble of claim 1 , where the electric motor comprises fingers, and the console comprises openings, and where the fingers engage the openings to secure the electric motor to the console. Such a construction allows for a relatively simple assembly. The electric motor is positioned in the appropriate position relative to the console, for example inserted into a receiving part of the console.

In an embodiment of the invention, the fingers protrude out of the openings, and a free end of the fingers is bent. Hence, the fingers are guided through the openings in the console until they protrude out of the openings. Subsequently, a free end of the fingers protruding out of the opening is bent to fix the electric motor and the console. Bending of the fingers is a relatively simple step.

In an embodiment of the invention, at least one finger comprises a first section, parallel to an axis of rotation of the motor, and a second section extending in circumferential direction around the axis, where the second section is bent relative to the first section. It is not necessary for the first section and the second section to be exactly parallel to an axis of rotation of the electric motor nor to point exactly in the circumferential direction around the axis. It is sufficient that the majority of the first section and the second section extend in the mentioned direction. The finger thus has an L- shape, where the second section is bent relatively to the first section such that an end of the second section is moved closer to the axis of rotation of the electric motor.

In an embodiment of the invention, the second section comprises a width measured along the axis of rotation of the electric motor, which is increasing in a direction towards the first section. This increases the rigidity and thereby the stability of the second section.

In an embodiment of the invention, the second section comprises a lower edge in contact with the console, where the lower edge is inclined in a direction towards the first section. When the end of the second section is bent towards the axis of rotation of the electric motor, the electric motor is immovably fixed to the console.

In an embodiment of the invention, at least two fingers are provided, which have second sections extending in opposite directions in the circumferential direction. During bending of the second sections of these two fingers, no rotational forces, which could twist the electric motor relative to the console, are created. Further, each of the first sections of the two fingers will engage opposite wall sections of the corresponding openings in the console. The fingers can therefore not be displaced in the openings of the console. The electric motor is therefore immovably fixed to the console and thus able to withstand torque and other forces occurring during operation of the linear actuator.

In an embodiment of the invention, the two fingers are arranged symmetrically with respect to a plane through the axis. This simplifies the assembly.

In an embodiment of the invention, at least three fingers are provided. This provides a connection between the motor and the gear housing which is sufficient to withstand the torque and forces which occur during operation of the linear actuator.

In an embodiment of the invention, the fingers are distributed evenly in the circumferential direction. In other words, the distances in the circumferential direction between two fingers are almost equal.

In an embodiment of the invention, the electric motor comprises a motor housing made of a sheet-metal and the fingers constitute a part of the motor housing. The motor housing is cylindrical. Thus, the fingers have the right form to engage with the openings of the console. In an embodiment of the invention, the console comprises a friction bearing supporting the end of the shaft of the electric motor. This friction bearing facilitates the insertion of the electric motor in the console. Furthermore, it allows for a two-point support of the shaft.

An embodiment of the invention will be described in more detail with reference to the drawing, in which:

Fig. 1 shows a perspective view of a linear actuator,

Fig. 2 shows a perspective view of a linear actuator with a longitudinal partial section through the console, outer and inner tube, as well as spindle and spindle nut,

Fig. 3 shows a front view of a linear actuator,

Fig. 4 shows an exploded perspective view of the components of a linear actuator,

Fig. 5 shows a side view of the electric motor of the linear actuator, and

Fig. 6 shows a perspective view of the assembled linear actuator.

In all figures the same reference numerals are used for the same elements.

Fig. 1 shows a perspective of a linear actuator 1 comprising a console 2, an outer tube 3 and an inner tube 4 guided in this. For mounting the linear actuator 1 , a rear end is equipped with a rear mounting 5 and at a front end of the inner tube 4 there is a front mounting 6. As it appears from both Fig. 1 and Fig. 2, the linear actuator 1 comprises an electric motor 7, typically a reversible electric motor, which can be either a DC or AC motor for low voltage or mains voltage. The electric motor 7 is mounted to the bottom of the console 2 and the rear mounting 5 is mounted to the rear end of the console 2.

The linear actuator 1 comprises a socket 8 for connecting the linear actuator 1 to a power supply or an electric controller. The outer tube 3 comprises a rectangular cross-section, in particular a square cross-section, i.e. the outer tube 3 comprises four walls 9,10,1 1 ,12.

The linear actuator 1 further comprises a spindle 13, driven by the electric motor 7 through a transmission 14, which is a worm gear, where an extension of the shaft of the electric motor 7 is designed as a worm 25 in engagement with a worm wheel 15, which is in driving connection with the spindle 13.

A spindle nut 16 with internal threads engage the external threads of the spindle 13. The spindle nut 16 is guided inside the outer tube 3 and is secured against rotation.

The front most part of the spindle nut 16 is adapted for receiving the inner tube 4. More specifically, the rear part of the inner tube 4 can be fastened to the spindle nut 16 by means of corresponding threads on both parts, or the spindle nut 16 can have a projecting edge or shoulder on which the inner tube 4 can be accommodated. Activation of the motor 7 will, via the transmission 14, cause the spindle 13 to rotate, whereby the spindle nut 16 and inner tube 4 will travel along the longitudinal axis of the spindle 13 in a direction depending on the direction of rotation of the electric motor 7.

The front end of the outer tube 3 comprises a bushing 17 for guiding the inner tube 4. The bushing 17 can be designed with a seal to prevent ingress of dust and moisture between the bushing 17 and outer tube 3 and the inner tube 4, respectively. Fig. 4 shows an exploded perspective view of components of a linear actuator 1 , in particular an electric motor 7, a console 2, and a control box 18.

The console 2 comprises a receiving part 19 for the electric motor 7. A ring- shaped wall 20 is made integral with the receiving part 19. The top of the receiving part 19 comprises a number of through-going openings 21 ,22. Furthermore, the console 2 comprises a friction bearing 23 supporting a top 24 of the shaft 25 of the electric motor 7.

The electric motor 7 comprises a motor housing 26 of a sheet-metal. The sheet-metal is bent to a cylindrical form and encloses the electric motor 7.

At an end facing towards the console 2, the motor housing 26 comprises three fingers 27, 28, 29. The fingers 27, 28, 29 comprise a first section 30 which is essentially parallel to an axis of rotation of the electric motor 7 and a second section 31 extending in circumferential direction around the axis.

When the electric motor 7 is mounted to the console 2, the fingers 27, 28, 29 are guided through the openings 21 , 22 (an opening for the finger 29 is not visible in the drawings). When the second section 31 of the fingers 27, 28, 29 has passed through the openings 21 , 22, they are bent radially inwardly. More precisely, an end 32 of the second section 31 of the fingers 27, 28, 29 is pushed in a direction towards the axis of rotation of the electric motor 7. Hereby, the electric motor 7 is fixedly connected to the console 2. When the second section 31 is bent relatively to the first section 30, there is a risk of the first section 30 also being bent or twisted. However, such twisting is limited by the slit-form of the openings 21 , 22.

As can be seen in Fig. 5, the fingers 27, 28 comprise an L-shape. Measured in a direction parallel to the axis of rotation of the electric motor 7, the second section 31 comprises a width, which increases in a direction towards the first section 30. Therefore, the fingers 27, 28 comprise a lower edge 33 which is inclined in a direction towards the first section 30.

When the second sections 31 are bent radially inwardly, the electric motor 7 is pulled further into the receiving part of the console 2 and thereby secured firmly to the console 2.

The ring-shaped wall 20 is a means facilitating the alignment of the electric motor 7 to the required position with respect to the console 2.

As can be seen in Fig. 4, the electric motor 7 comprises three fingers 27, 28, 29. Two, four or more fingers can be used, if appropriate.

Two of the fingers 27, 28 have second sections 31 extending in opposite directions in the circumferential direction. Hereby, these two fingers 27, 28 are arranged symmetrically with respect to a plane through the axis of rotation of the electric motor 7.

The fingers 27, 28, 29 are distributed evenly in the circumferential direction to achieve a uniform load distribution. When the electric motor 7 is activated, it creates a torque which propagates to the motor housing 26. The torque must be accommodated by the console 2. By having the second sections 31 of the two fingers 27, 28 extend in opposite directions, the console 2 can accommodate the torque in either direction of rotation of the shaft 25.

The use of the fingers 27, 28 ,29 greatly facilitates the connection of the electric motor 7 to the console 2. In a first step, the electric motor 7 is positioned with respect to the console 2, and the fingers 27, 28, 29 are guided through the openings 21 , 22. Thereafter only a radially acting pressure force is necessary to bend the second sections 20 of the fingers 27, 28, 29, radially inwardly, i.e. towards the rotation axis of the electric motor.




 
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