LINEAR ACTUATOR

Abstract

Linear actuator comprising an electric motor (2) which through a transmission (3) drives a spindle unit, where the spindle unit comprises at least one spindle (4) with a spindle nut (5), where the spindle (4) is equipped with a bearing (8). In connection with the spindle unit there is an adjustment element (6), typically tubular. In order to retain the adjustment element (6) in a given position when the power supply for the electric motor (2) is interrupted, a brake (11) comprising a spring (15) and a cylindrical element (12) is provided. The cylindrical element (12) has a threaded pin (12a) on which a nut (13) is arranged, and where the spring (15) is positioned around the cylindrical element (12) between one side of the nut (12) and a stop (14) on the cylindrical element (12) such that the spring (15) presses the nut (13) with its other side against a contact surface (16). The brake power is thus generated by the nut rubbing against the contact surface with its one side. It is thus an alternative brake construction having a simple construction and where the spring only exerts a compressive force. The brake power can be adjusted to the spring power, and the friction between the nut and the contact surface and finally the thread pitch on the nut.

Claims

1. A linear actuator comprising an electric motor (2) with a motor shaft, a transmission (3) in connection with the motor shaft, a spindle unit in connection with the transmission, where the spindle unit comprises at least one spindle (4) with a spindle nut (5), and where the spindle (4) is equipped with a bearing (8), an adjustment element (6) in connection with the spindle unit, a brake (11) comprising a spring (15), and a cylindrical element (12) for retaining the adjustment element (6) in a given position when the power supply for the electric motor (2) is interrupted, wherein the cylindrical element (12) has a threaded pin (12a) on which a nut (13) is arranged, and where the spring (15) is positioned around the cylindrical element (12) between one side of the nut (12) and a stop (14) on the cylindrical element (12) such that the spring (15) presses the nut (13) with its other side against a contact surface (16).

2. The linear actuator according to claim 1, wherein the spring (15) is a coil spring.

3. The linear actuator according to claim 1, wherein the spring (15) is a torsional spring.

4. The linear actuator according to claim 1, wherein the brake (11) is arranged on a rear end, the shaft of the spindle (4).

5. The linear actuator according to claim 1, wherein the brake (11) is arranged on the motor shaft.

6. The linear actuator according to claim 1, wherein the cylindrical element (12) is constructed as a separate element.

7. The linear actuator according to claim 1, further comprising a housing (1) and that the contact surface (16) is constituted by a side surface of the housing (1).

Description

[0013] A linear actuator according to the invention will be described more fully below with reference to the accompanying drawing, in which:

[0014] FIG. 1 shows a linear actuator comprising a two-part housing, where one part has been removed,

[0015] FIG. 2 shows a detailed section of the brake of the actuator,

[0016] FIG. 3 shows a longitudinal section of the section of FIG. 2, and

[0017] FIG. 4 shows a perspective view of the section of FIG. 2.

[0018] FIG. 1 shows an actuator comprising a two-part housing 1 made from plastic with a reversible electric motor 2, which through a worm gear 3 drives a spindle 4 with a spindle nut 5 to which an activation rod 6 (also known as the inner tube) surrounded by an outer tube 7 functioning as a guide for the activation rod 6 is secured. With its one end the spindle 4 is embedded with a bearing 8 in the housing 1. The actuator is mounted in the structure in which it should be incorporated by means of a rear mounting 9 mounted at the rear end of the housing 1 and a front mounting 10 at the free end of the activation rod 6.

[0019] The rear end, the shaft 4a of the spindle 4, is equipped with a brake mechanism 11 as described more fully with reference to FIGS. 2, 3 and 4 of the drawing. A cylindrical element 12 in the form of a bushing, which is secured against rotation, having a portion with external threads 12a, is mounted on the shaft 4a of the spindle 4. On the threaded pin 12a, a nut 13 is arranged. A stop 14 in the form of a ring is secured to an end, the front end of the cylindrical element 12. Between this stop 14 and the front side of the nut 13, a coil or a coil spring 15 is arranged, which exerts a compressive force on the nut 13. As the threads on the cylindrical element 12 and the nut 13 are non-self-locking, the nut 13 will be pushed backwards against a contact surface 16, which is here constituted by a side of a seat 17 for the bearing 8 for the spindle 4. On the rearmost end of the spindle 4, a clutch part 18 for interconnection with an output stage of the transmission of the actuator is mounted. As it appears from the drawing, the bearing is embedded on a ring-shaped part 19 of the cylindrical element 12 and the clutch part 18.