Abstract:
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.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an actuator, and more particularly to an actuator with self-locking assist device. 
         [0003]    2. Description of the Prior Art 
         [0004]    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. 
         [0005]    As shown in  FIG. 1 , an actuator  10  comprises a first pipe  11  and a second pipe  12  inserted in the first pipe  11 . In the first pipe  11  is axially pivoted a screw  13  on which is axially mounted a gear  131 . Through the gear  131  the screw  13  is connected to and rotated by a power source. The second pipe  12  has one end positioned at one end of a nut  132  and is to be pushed to move back and forth along the first pipe  11 . 
         [0006]    After further analyzing the above structure, we found it still has the following problems: once the actuator  10  is used for carrying load, after the screw  13  stops rotating, the self-locking of the actuator  10  depends 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 pipe  12  which previously extended out move back into the first pipe  11  again, and as a result, the actuator  10  will move uncontrollably because of the influence of the load carried, and thus the safe use of the actuator cannot be ensured. 
         [0007]    The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
       SUMMARY OF THE INVENTION 
       [0008]    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. 
         [0009]    To achieve the above object, a self-locking assist device in accordance with the present invention comprises: 
         [0010]    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 
         [0011]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is an assembly view of a conventional actuator; 
           [0013]      FIG. 2  is a cross sectional view of an actuator with one self-locking assist device; 
           [0014]      FIG. 3  is an amplified view of a part of  FIG. 2 ; 
           [0015]      FIG. 4  is a cross sectional view of an actuator with two self-locking assist devices; and 
           [0016]      FIG. 5  is an amplified view of a part of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The present invention will be clearer from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 
         [0018]    Referring to  FIG. 2 , an actuator with self-locking assist device in accordance with a preferred embodiment of the present invention comprises an actuator  20  and a self-locking assist device  30  axially disposed on the actuator  20 . 
         [0019]    The actuator  20  comprises a first pipe  21 , a second pipe  22  and a transmission assembly  23 . 
         [0020]    The first pipe  21  has an open end  211  and a close end  212 , and in the close end  212  of the first pipe  21  is axially formed an adjusting hole  213 . The second pipe  22  also has an open end  221  and a close end  222 , and in the close end  222  of the second pipe  22  is defined an adjusting hole  223 . The second pipe  22  has a cross section smaller than that of the first pipe  21 . The open ends  221 ,  211  of the second and first pipes  22 ,  21  are oppositely arranged, and the second pipe  22  is movably disposed in the first pipe  22 . The assembling direction of the two pipes  21  and  22  correspond to their extension direction. 
         [0021]    The transmission assembly  23  comprises a screw  231 , a drive gear  232  and a driven nut  233 . The screw  231  is axially disposed in the close end  212  of the first pipe  21  of the actuator  20  in such a manner that the lower end of the screw  231  is opposite the adjusting hole  213  of the first pipe  21 . The drive gear  232  is mounted on the screw  231  and dynamically connected with the power source. The driven nut  233  is coaxially and dynamically connected with the drive gear  232 , and one end of the driven nut  233  is coaxial assembled to the open end  221  of the second pipe  22 . When the drive gear  232  drives the screw  231  to rotate, the driven nut  233  will be caused to make the second pipe  22  extend out or retract into the first pipe  21 . 
         [0022]    The self-locking assist device  30 , as shown in  FIGS. 2 and 3 , comprises a stop member  31 , an elastic member  32  and a limit member  33 . The stop member  31  is a ball, the elastic member  32  is a spring, and the limit member  33  is a bolt, and they are received in the adjusting hole  213  of the first pipe  21 , respectively in such a manner that the stop member  31  is abutted against the transmission assembly  23 , the elastic member is pressed against the stop member  31 , and the stop member  31  is pressed against the elastic member  32  to generate friction therebewteen, with the displacement of the limit member  33 , the limit member  33  is caused to push the stop member  31  via the elastic member  32 , thus adjusting a friction force of the stop member  31  applied to the transmission assembly  23 . Or, (as shown in  FIGS. 4 and 5 ), the self-locking assist device  30  comprises two stop members  31 , two elastic members  32  and two limit members  33 , they can be received in each of the adjusting holes  213 ,  223  of the first and second pipes  21 ,  22 , respectively, in such a manner that the stop members  31  are frictionally abutted against both ends of the screw  231  of the transmission assembly  23 , the threaded portions of the limit members  33  are screwed in the adjusting holes  213  and  223  of the first and second pipes  21 ,  22 , and the elastic members  32  are biased between the stop members  31  and the limit members  33 . With the displacement of the limit members  33 , the push force of the elastic members  32  applied to the stop members  31  can be adjusted, meanwhile, the push force of the stop members  31  applied on the screw  231  is also adjusted, thus adjusting the friction force between the stop members  31  of the self-locking assist device  30  and the screw  231  of the transmission assembly  23 , and the value of the friction force is determined by the amount of compression and elasticity of the elastic members  32 . 
         [0023]    While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.