Actuator with self-locking assist device

An actuator with self-locking assist device comprises an actuator and a self-locking assist device, wherein the self-locking assist device is disposed at one end of the actuator, and the friction force between the self-locking assist device and the actuator is used to improve the self-locking capability of the actuator, thus preventing the uncontrollable movement of the actuator caused by the influence of the load carried.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an actuator, and more particularly to an actuator with self-locking assist device.

2. Description of the Prior Art

Actuator is usually used in various kinds of equipments (such as ventilator, automatic door, cupboard, satellite antenna hoisting device, elevating wheelchair, height-adjustable hospital bed, drawing table, massage chair, transportation equipment, height-adjustable computer desk or rehabilitation equipment) to achieve automatic operation.

As shown inFIG. 1, an actuator10comprises a first pipe11and a second pipe12inserted in the first pipe11. In the first pipe11is axially pivoted a screw13on which is axially mounted a gear131. Through the gear131the screw13is connected to and rotated by a power source. The second pipe12has one end positioned at one end of a nut132and is to be pushed to move back and forth along the first pipe11.

After further analyzing the above structure, we found it still has the following problems: once the actuator10is used for carrying load, after the screw13stops rotating, the self-locking of the actuator10depends on the friction among relative components. Hence, the phenomenon that the weight of the load makes the actuator move due to the incapability of self-locking is likely to occur, making the second pipe12which previously extended out move back into the first pipe11again, and as a result, the actuator10will move uncontrollably because of the influence of the load carried, and thus the safe use of the actuator cannot be ensured.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide an actuator with self-locking assist device, wherein the friction force between the self-locking assist device and the actuator is used to improve the self-locking capability of the actuator.

To achieve the above object, a self-locking assist device in accordance with the present invention comprises:

an actuator including at least two pipes and a transmission assembly, the one pipe is received in the other pipe, the transmission assembly is disposed in the actuator and dynamically connected with the first and second pipe, in one end of the one of the pipes is defined an adjusting hole; and

a self-locking assist device including a stop member, an elastic member and a limit member movably disposed in the adjusting hole of the actuator, respectively, in such a manner that the stop member is abutted against the transmission assembly, the elastic member is pressed against the stop member to generate a friction therebetween, and the stop member is pressed against the elastic member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 2, an actuator with self-locking assist device in accordance with a preferred embodiment of the present invention comprises an actuator20and a self-locking assist device30axially disposed on the actuator20.

The actuator20comprises a first pipe21, a second pipe22and a transmission assembly23.

The first pipe21has an open end211and a close end212, and in the close end212of the first pipe21is axially formed an adjusting hole213. The second pipe22also has an open end221and a close end222, and in the close end222of the second pipe22is defined an adjusting hole223. The second pipe22has a cross section smaller than that of the first pipe21. The open ends221,211of the second and first pipes22,21are oppositely arranged, and the second pipe22is movably disposed in the first pipe22. The assembling direction of the two pipes21and22correspond to their extension direction.

The transmission assembly23comprises a screw231, a drive gear232and a driven nut233. The screw231is axially disposed in the close end212of the first pipe21of the actuator20in such a manner that the lower end of the screw231is opposite the adjusting hole213of the first pipe21. The drive gear232is mounted on the screw231and dynamically connected with the power source. The driven nut233is coaxially and dynamically connected with the drive gear232, and one end of the driven nut233is coaxial assembled to the open end221of the second pipe22. When the drive gear232drives the screw231to rotate, the driven nut233will be caused to make the second pipe22extend out or retract into the first pipe21.

The self-locking assist device30, as shown inFIGS. 2 and 3, comprises a stop member31, an elastic member32and a limit member33. The stop member31is a ball, the elastic member32is a spring, and the limit member33is a bolt, and they are received in the adjusting hole213of the first pipe21, respectively in such a manner that the stop member31is abutted against the transmission assembly23, the elastic member is pressed against the stop member31, and the stop member31is pressed against the elastic member32to generate friction therebetween, with the displacement of the limit member33, the limit member33is caused to push the stop member31via the elastic member32, thus adjusting a friction force of the stop member31applied to the transmission assembly23. Or, (as shown inFIGS. 4 and 5), the self-locking assist device30comprises two stop members31, two elastic members32and two limit members33, they can be received in each of the adjusting holes213,223of the first and second pipes21,22, respectively, in such a manner that the stop members31are frictionally abutted against both ends of the screw231of the transmission assembly23, the threaded portions of the limit members33are screwed in the adjusting holes213and223of the first and second pipes21,22, and the elastic members32are biased between the stop members31and the limit members33. With the displacement of the limit members33, the push force of the elastic members32applied to the stop members31can be adjusted, meanwhile, the push force of the stop members31applied on the screw231is also adjusted, thus adjusting the friction force between the stop members31of the self-locking assist device30and the screw231of the transmission assembly23, and the value of the friction force is determined by the amount of compression and elasticity of the elastic members32.