Abstract:
A motor with a braking mechanism for an actuator includes a main body, a rotating shaft and a braking mechanism. The rotating shaft is disposed through the center of the main body. The braking mechanism includes a friction element and a torsion spring, the friction element is arranged on the external periphery of the rotating shaft, and the torsion spring is elastically clamped at an outer edge of the friction element and an end of the torsion spring is fixed to main body. When the rotating shaft rotates in one direction, the torsion spring abuts the friction element to brake and decelerate the rotating shaft. With small wear and tear of the torsion spring, the service life can be extended. With a large contact area between the friction element and the rotating shaft, a good braking effect can be achieved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a motor used for a linear actuator, and in particular to a motor with a braking mechanism for the actuator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Linear actuator primarily uses driving components such as a motor, a worm and a worm wheel to drive a lead screw rod, while using the lead screw rod to drive a telescopic pipe installed to the lead screw rod for a linear extension or retraction movement. Since the structure and installation of the linear actuator are simpler and easier than those of pneumatic and hydraulic cylinders, the linear actuator has been used extensively in various equipments such as hospital beds and electric chairs or in any other areas that require extension and retraction operations. 
         [0003]    In the conventional linear actuators as disclosed in European Patent Publication No. EP0662573B1 and PCT Publication No. WO2004-027290A2, the linear actuator disclosed in EP0662573B1 comprises: a worm; a lead screw rod; a worm wheel module fixed to an end of the lead screw rod and including a worm wheel; and a torsion spring installed around the external periphery of a cylindrical annulus. In WO2004-027290A2, a thermal conductive element is provided for dissipating heat generated by frictions during the operation of the torsion spring with the annulus. 
         [0004]    However, the torsion spring of the conventional linear actuator is fixed, and the cylindrical annulus rotates with the worm wheel, so that heat is generated by frictions produced between the torsion spring and the cylindrical annulus, usually made from plastic and the heat may melt or damage the cylindrical annulus easily, thus reducing the service life significantly. Further, only the linear contact between the torsion spring and the rotating cylindrical annulus is provided for a braking effect or a speed reduction effect, but such a braking effect or a speed reduction effect is limited because the effective contact area between the torsion spring and the ring is small. 
         [0005]    In view of the aforementioned drawbacks of the prior art, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally provided a feasible solution in accordance with the present invention to overcome the drawbacks of the prior art. 
       SUMMARY OF THE INVENTION 
       [0006]    Therefore, it is a primary objective of the present invention to provide a motor with a braking mechanism for an actuator, wherein a torsion spring is tightly bound around a friction element to brake or decelerate a rotating shaft, so that the tear and wear of the torsion spring can be minimized and the service life of the motor can be extended. In addition, a large contact area between the friction element and the rotating shaft provides a good braking effect. 
         [0007]    To achieve the foregoing objectives, the present invention provides a motor with a braking mechanism for an actuator, and the motor comprises a main body, a rotating shaft and a braking mechanism, wherein the rotating shaft is disposed though the center of the main body; the braking mechanism includes a friction element and a torsion spring, and the friction element is arranged on the external periphery of the rotating shaft, and the torsion spring is arranged to elastically clamp the friction element and an end of the torsion spring is fixed to the main body. When the rotating shaft rotates in a direction, the torsion spring forces the friction element to brake or decelerate the rotating shaft. 
         [0008]    To achieve the foregoing objectives, the present invention provides a motor with a braking mechanism for an actuator, wherein the actuator includes a base; the motor with the braking mechanism comprises a main body, a rotating shaft and a braking mechanism, and the main body is fixed to the base; the rotating shaft is disposed through the center of the main body and extends into the base; the braking mechanism includes a friction element and a torsion spring; the friction element is arranged on the external periphery of the rotating shaft; and the torsion spring is arranged to elastically clamp an outer edge of the friction element, and an end of the torsion spring is fixed into the base. When the rotating shaft rotates in a direction, the torsion spring forces the friction element to brake or decelerate the rotating shaft. 
         [0009]    The present invention has the following effects. In prior art, the cylindrical annulus is driven by the worm wheel to rotate relative to the torsion spring, thus causing problems of frictional losses, heat accumulation, and overheating. The friction element is used in a non-power transmission coupling and essentially the friction element would not follow the rotating shaft for continuous rotation, thus effectively solving the above-mentioned problems in prior art. The braking mechanism installed to the rotating shaft of the motor of the actuator can achieve a better braking effect with a small action force. The friction element and the torsion spring do not produce any relative frictional rotation in between, thus naturally causing no concern of melting the friction element. When the rotating shaft rotates in a specific direction, the damp between the rotating shaft and the friction element is small and will not affect the transmission performance of the motor. In the process of retracting a telescopic pipe, the braking effect and the speed reduction can be achieved. A steady speed is maintained for descending or retracting the telescopic pipe, so as to improve the user&#39;s comfort in use. The present invention also has the advantages of a simple structure, a low cost, and a small volume. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded perspective view of a first preferred embodiment of the present invention; 
           [0011]      FIG. 2  is a perspective view showing the external appearance of the first preferred embodiment of the present invention; 
           [0012]      FIG. 3  is a partial cross-sectional view of  FIG. 2 ; 
           [0013]      FIG. 4  is a schematic view showing the operation of the first preferred embodiment of the present invention applied in a linear actuator; 
           [0014]      FIG. 5  is an exploded perspective view of a second preferred embodiment of the present invention; 
           [0015]      FIG. 6  is an exploded perspective view of a third preferred embodiment of the present invention; 
           [0016]      FIG. 7  is an exploded perspective view of a fourth preferred embodiment of the present invention; 
           [0017]      FIG. 8  is an assembled view showing the external appearance of the fourth preferred embodiment of the present invention; 
           [0018]      FIG. 9  is a partial cross-sectional view of  FIG. 8 ; 
           [0019]      FIG. 10  is an exploded perspective view of a fifth preferred embodiment of the present invention; 
           [0020]      FIG. 11  is a partial cross-sectional view of  FIG. 10 ; 
           [0021]      FIG. 12  is an exploded perspective view of a sixth preferred embodiment of the present invention; 
           [0022]      FIG. 13  is an assembled view of the sixth preferred embodiment of the present invention; 
           [0023]      FIG. 14  is a partial cross-sectional view of  FIG. 13 ; 
           [0024]      FIG. 15  is an exploded perspective view of a seventh preferred embodiment of the present invention and an actuator; and 
           [0025]      FIG. 16  is an assembled view of the seventh preferred embodiment of the present invention and an actuator. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The technical characteristics and contents of the present invention will become apparent with the following detailed description and related drawings. The drawings are provided for the purpose of illustrating the present invention only, but not intended for limiting the scope of the invention. 
         [0027]    With reference to  FIGS. 1 to 3  showing a motor with a braking mechanism for an actuator in accordance with the present invention, the motor  1  comprises a main body  10 , a rotating shaft  20  and a braking mechanism  30 . 
         [0028]    The main body  10  comprises a cylindrical casing  11 , components such as a rotor, a stator and a coil (not shown in the figure) contained in the casing  11 , and a plurality of screw holes  111  formed at a rear end surface of the casing  11 . The main body  10  of this preferred embodiment further comprises a fastening element  12  substantially in a stepped shape and having a through hole  121  and an insertion hole  122  formed thereon, and the through hole  121  is provided for allowing a screw element  13  to threadedly connected into the screw hole  111  to combine the fastening element  12  with the casing  11 . 
         [0029]    The rotating shaft  20  is disposed through the central position of the main body  10 , and both ends of the rotating shaft  20  extend outwards from the casing  11 , and a worm rod  21  is formed at an end of the rotating shaft  20 . 
         [0030]    The braking mechanism  30  includes a friction element  31  and a torsion spring  32 . The friction element  31  of this preferred embodiment is made of metal or plastic and substantially in the shape of a circular ring, and a cut groove  311  is formed on the circular ring for producing a contraction in a radial direction of the friction element  31  when the friction element  31  is elastically clamped by the torsion spring  32 . In addition, a coarse pattern  313  is formed on the external surface of the friction element  31 , such that when the torsion spring  32  is arranged on the coarse pattern  313 , an axial movement of each spring coil can be restrained, and a retaining force between the torsion spring  32  and the friction element  31  can be increased. The friction element  31  is arranged on the external periphery of the rotating shaft  20 . The torsion spring  32  can be a right-hand rotating torsion spring, so that when the rotating shaft  20  rotates counterclockwise, the torsion spring  32  produces a contraction in a radial direction. On the other hand, when the rotating shaft  20  rotates clockwise, the torsion spring  32  produces an expansion in a radial direction. In this preferred embodiment, the torsion spring  32  includes a positioning arm  321 , and the torsion spring  32  is arranged to elastically clamp on the external periphery of the friction element  31  in such a manner that the positioning arm  321  of the torsion spring  32  is inserted into the insertion hole  122  and fixed thereto. 
         [0031]    With reference to  FIG. 4 , the motor  1  of the present invention is installed to a linear actuator  5 , and the linear actuator  5  comprises a base  51 , a transmission mechanism  52 , an outer pipe  53 , a telescopic pipe  54  and other components. The transmission mechanism  52  includes a lead screw rod  521 , a worm wheel  522 , a nut  523  and other components, wherein an end of the outer pipe  53  is fixed to the base  51 , and an end of the lead screw rod  521  is disposed inside the base  51  and the other end of the lead screw rod  521  is disposed into the outer pipe  53 . The worm wheel  522  is fixed to the lead screw rod  521  and disposed in the base  51 . An end of the telescopic pipe  54  and the nut  523  are coupled with each other, and the other end of the telescopic pipe  54  pierces the outer pipe  53 , and the nut  523  and the lead screw rod  521  are threadedly connected to each other to achieve the transmission effect. An end of the motor  1  of the present invention is fixed to the base  51 , and the worm rod  21  of the rotating shaft  20  is engaged with the corresponding worm wheel  522  to achieve the transmission effect, so as to constitute the linear actuator  5 . 
         [0032]    When in use, the rotating shaft  20  is driven by the components inside the main body  10  to produce a rotation. When the worm wheel  522  is driven by the worm rod  21  to rotate clockwise, the lead screw rod  521  drives the telescopic pipe  54  to retract into the outer pipe  53 , and an end of the torsion spring  32  fixed and tightly bounded with the friction element  31  can produce a contraction in a radial direction, and the elasticity of the torsion spring  32  provides an elastic clamping force and the friction effect between the internal wall of the friction element  31  and the surface of the rotating shaft  20  to decelerate the rotating speed of the rotating shaft  20  and the lead screw rod  521 . Therefore, when the linear actuator  5  is installed to an electric bed or a chair, the speed for the telescopic pipe  54  to retract into the outer pipe  53  is slower, so as to improve the comfort of the user. 
         [0033]    On the other hand, when the worm wheel  522  is driven by the worm  21  to rotate counterclockwise, the lead screw rod  521  drives the telescopic pipe  54  to extend out of the outer pipe  53 , and the rotating shaft  20  rotates in a direction opposite to the rotating direction of the torsion spring  32 , such that the rotating shaft  20  drives the friction element  31  to expand the torsion spring  32  in a radial direction. Now, the friction element  31  is released to reduce the friction damping caused by the rotation of the rotating shaft  20 , so that the rotating shaft  20  can rotate easily inside the friction element  31  without affecting the transmission performance of the motor  1 . 
         [0034]    With reference to  FIG. 5  showing a motor in accordance with the second preferred embodiment of the present invention, the main difference between the motor  1   a  of this preferred embodiment and the motor  1  of the first preferred embodiment lies in that the friction element  31   a  is comprised of three arc plates  312   a  that are combined into a substantially circular ring. The invention is not limited to such arrangement only, but any friction element comprised of two or more arc plates  312   a  can be used in the present invention. Each arc plate  312   a  is arranged on the external periphery of the rotating shaft  20 . The torsion spring  32  is elastically arranged on the external periphery of the three arc plates  312   a , and the positioning arm  321  of the torsion spring  32  is inserted into the insertion hole  122 . 
         [0035]    With reference to  FIG. 6  showing a motor in accordance with the third preferred embodiment of the present invention, the main difference between the motor  1   b  of this preferred embodiment and the motor of the foregoing preferred embodiment lies in that the friction element  31   b  is comprised of three arc plates  312   b , and a protruding ring  112  extends from a distal surface of the casing  11 , and each arc plate  312   b  is arranged on the external periphery of the rotating shaft  20 . A portion of the torsion spring  32   b  is tightly arranged on the protruding ring  112 , and another portion is elastically arranged on each arc plate  312   b.    
         [0036]    With reference to  FIGS. 7 to 9  showing a motor in accordance with the fourth preferred embodiment of the present invention, the main difference between the motor  1   c  of this preferred embodiment and the motor of the foregoing preferred embodiment lies in that the friction element  31   c  is comprised of three stepped arc plates  312   c . Similarly, the friction element  31   c  can be a structure with two stepped arc plates  312   c . The fastening element  12   c  is comprised of an outer ring  123   c , an inner ring  124   c  coupled to and formed inside the outer ring  123   c , and a groove passage  125   c  formed between the outer ring  123   c  and the inner ring  124   c , and each arc plate  312   c  is arranged on the external periphery of the rotating shaft  20 . A portion of the torsion spring  32   c  is contained in the groove passage  125   c  and tightly arranged on the external periphery of the inner ring  124   c , and another portion of the torsion spring  32   c  is elastically arranged on a large-diameter external periphery of each arc plate  312   c  (as shown in  FIG. 9 ). 
         [0037]    With reference to  FIGS. 10 and 11  showing a motor in accordance with the fifth preferred embodiment of the present invention, the main difference between the motor  1   d  of this preferred embodiment and the motor of the foregoing preferred embodiment lies in that the friction element  31   d  is comprised of three stepped arc plates  312   d , and the fastening element  12   d  has an outer ring  123   d , and the fastening element  12   d  has a slot  126   d  formed therein, and each arc plate  312   d  is arranged on the external periphery of the rotating shaft  20 , and the torsion spring  32   d  is elastically arranged on the external periphery of the three arc plates  312   d  and contained in the outer ring  121   d , and the positioning arm  321   d  of the torsion spring  32   d  is fixed into the slot  126   d  (as shown in  FIG. 11 ). 
         [0038]    With reference to  FIGS. 12 and 14  showing a motor in accordance with the sixth preferred embodiment of the present invention, the main difference between the motor  1   e  of this preferred embodiment and the motor of the foregoing preferred embodiment lies in that the friction element  31   e  is also comprised of three arc plates  312   e , and the casing  11  has a accommodating chamber  114  formed inside an end cover  113  and an insertion slot  115  formed in the accommodating chamber  114 , and the friction element  31   e  and the torsion spring  32   e  are installed in the accommodating chamber  114 , and each arc plate  312   e  is arranged on the external periphery of the rotating shaft  20 . The torsion spring  32   e  is elastically arranged on the external periphery of the three arc plates  312   e , and the positioning arm  321   e  of the torsion spring  32   e  is fixed into the insertion slot  115  (as shown in  FIG. 14 ). In addition, a restricting sleeve  14  is provided for abutting and positioning the friction element  31   e , wherein the restricting sleeve  14  may prevent moisture or dusts outside the casing  11  from being stuck or attached onto the friction element  31   e  and the torsion spring  32   e.    
         [0039]    With reference to  FIGS. 15 and 16  showing a motor in accordance with the seventh preferred embodiment of the present invention, the main difference between the motor  1   f  of this preferred embodiment and the motor of the foregoing preferred embodiment lies in that each arc plate  312   a  of the friction element  31   a  is arranged on the external periphery of the rotating shaft  20  at an internal end of the worm rod  21  (as shown in  FIG. 16 ). The torsion spring  32  is elastically arranged on the external periphery of the three arc plates  312   e . In addition, a positioning slot  511  is formed in the base  51 , and the positioning arm  321  of the torsion spring  32  is fixed into the positioning slot  511 . 
         [0040]    In summation of the description above, the motor with a braking mechanism for actuators of the present invention can achieve the expected objectives and improve over the prior art, and comply with the patent application requirements, and is thus duly filed for patent application. 
         [0041]    While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.