Patent Publication Number: US-2011061480-A1

Title: Quick-release mechanism of an actuator

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an actuator, and more particularly to a quick-release mechanism of an actuator. 
     In the field of electromechanics, various actuators, which can convert electrical energy into mechanical energy, are widely used to supply power as drive units. A conventional linear actuator has the advantages of light weight, compact structure, convenient operation, easy installation, low noise, high rigidity and low price. Therefore, all kinds of linear actuators have been popularly applied to different products such as automated equipments, motor-driven hospital beds and massage chairs. The actuators serve to stably output power for driving the products and are able to enhance precision of the automated equipments. 
     The conventional actuator is generally equipped with a quick-release mechanism. As an example, in normal state, a motor-driven hospital bed is drivable by the actuator to adjust the angle and height of the bed face. The hospital bed must be driven at slow speed. Otherwise, a patient may be negatively affected. However, in case that an emergency takes place and the patient on the hospital bed must be emergently treated, it will be necessary to quickly restore the hospital bed to a horizontal position at a lower height to facilitate the emergency treatment. At this time, the transmission path of the conventional actuator must be interrupted, permitting the hospital bed to be more quickly restored to its home position.  FIG. 1  shows the clutch mechanism  1  of the conventional actuator for interrupting the transmission path. 
     The clutch mechanism  1  substantially includes a worm wheel  2  drivable by a motor to rotate. One end of a transmission sleeve  3  is coaxially fixedly fitted in the worm wheel  2 , whereby the transmission sleeve  3  is movable along with the worm wheel  2 . A clutch collar  4  is fitted on the other end of the transmission sleeve  3  and slidable along the axis thereof. A push shaft  5  is freely rotatably coaxially fitted through the worm wheel  2 , the transmission sleeve  3  and the clutch collar  4 . A clutch tray  6  is coaxially fixedly fitted on the push shaft  5  to engage with or disengage from the clutch collar  4 . A spring  7  is compressed between the clutch collar  4  and the worm wheel  2  for resiliently pushing the clutch collar  4  to engage with the clutch tray  6 . Accordingly, when the worm wheel  2  is driven by the motor to rotate, through the transmission sleeve  3 , the clutch collar  4  and the clutch tray  6 , the push shaft  5  is simultaneously driven and rotated to output power. When it is necessary to quickly release the push shaft  5 , the clutch collar  4  is pushed to disengage from the clutch tray  6  for quickly releasing the push shaft  5 . 
     However, the above clutch mechanism  1  has some defects. For example, the clutch mechanism  1  is composed of numerous components so that the structure of the clutch mechanism  1  is complicated. As a result, the clutch mechanism  1  has a considerably large volume and is manufactured at higher cost. Moreover, the clutch mechanism  1  is composed of so many components that the possibility of failure of the clutch mechanism  1  is increased. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a quick-release mechanism of an actuator, which has smaller number of components and is manufactured by simplified process at lower cost. 
     It is a further object of the present invention to provide the above quick-release mechanism of the actuator, which has smaller volume and shortened power transmission distance. 
     To achieve the above and other objects, the quick-release mechanism of the actuator of the present invention includes: a worm wheel having a circular body section, a shaft hole extending through the body section along a curvature center line thereof; a rod-like push body coaxially fitted through the shaft hole; and a clutch unit having a first clutch section and a second clutch section, the first clutch section being connected with the worm wheel, the second clutch section being connected with the push body, the first and second clutch sections being movable relative to each other between a disengaging position and an engaging position, when positioned in the engaging position, the first and second clutch sections being engaged with each other to drivingly couple the worm wheel with the push body, when positioned in the disengaging position, the first and second clutch sections being disengaged from each other to uncouple the worm wheel from the push body, the clutch unit further having a resilient member, which provides resilient force for making the first and second clutch sections engaged with each other, said quick-release mechanism being characterized in that: the first clutch section is integrally formed at one end of the body section; the second clutch section is relatively unrotatably fitted on the push body and slidable along an axis of the push body between the disengaging position and the engaging position, whereby when positioned in the engaging position, a first end of the second clutch section is engaged with the first clutch section; and the clutch unit further includes a stopper member fixedly disposed on the push body and adjacent to a second end of the second clutch section, the resilient member being compressed between the stopper member and the second clutch section. 
     The present invention can be best understood through the following description and accompanying drawings wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective exploded view of a conventional clutch mechanism; 
         FIG. 2  is a perspective view of a preferred embodiment of the present invention; 
         FIG. 3  is a perspective exploded view of the preferred embodiment of the present invention; 
         FIG. 4  is a perspective assembled view of the preferred embodiment of the present invention; 
         FIG. 5  is a sectional view of the preferred embodiment of the present invention, in which the clutch unit is positioned in the engaging position; 
         FIG. 6  is a perspective view of the preferred embodiment of the present invention, in which the clutch unit is positioned in the engaging position; 
         FIG. 7  is a sectional view of the preferred embodiment of the present invention, in which the clutch unit is positioned in the disengaging position; and 
         FIG. 8  is a perspective view of the preferred embodiment of the present invention, in which the clutch unit is positioned in the disengaging position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to  FIGS. 2 to 9 . According to a preferred embodiment, the quick-release mechanism  10  of the actuator of the present invention includes a worm wheel  20 , a push body  30 , a clutch unit  40  and a shift section  50 . 
     The worm wheel  20  has a circular body section  21  and a shaft sleeve  22  integrally formed in the body section  21  at a curvature center thereof. 
     The shaft sleeve  22  has a length larger than a thickness of the body section  21 . Two ends of the shaft sleeve  22  axially protrude from two ends of the body section  21 . The shaft sleeve  22  has a shaft hole  23  extending through the shaft sleeve  22  along a curvature center line of the body section  21 . 
     The push body  30  is rod-like and has a rod section  31  coaxially fitted through the shaft hole  23  and freely rotatable within the shaft hole  23 . The push body  30  further has a D-shaped cut section  32  one end of which is coaxially connected with one end of the rod section  31 . 
     The clutch unit  40  includes a first annular clutch section  41  coaxially formed on an end face of the body section  21  and a second clutch section  42  having the form of an annular block. The second clutch section  42  is coaxially slidably fitted on the D-shaped cut section  32  of the push body  30 . A first end of the second clutch section  42  complementarily faces the first clutch section  41 . A stopper member  43  is fixedly disposed at the other end of the D-shaped cut section  32 . A resilient member  44  is compressed between the stopper member  43  and a second end of the second clutch section  42 . The resilient member  44  always exerts a resilient force onto the second clutch section  42  in a direction to the first clutch section  41  to make the first end of the second clutch section  42  engaged with the first clutch section  41 . 
     To speak more specifically, the first clutch section  41  has an annular recess  411  formed on the end face of the body section  21 . The curvature center line of the annular recess  411  coincides with the curvature center line of the body section  21 . Multiple keys  412  and key slots  413  are alternately integrally formed on outer circumferential wall of the annular recess  411  in parallel to each other. 
     The second clutch section  42  has a main body  421  as a circular block. A D-shaped through hole  422  is formed through the main body  421  along an axis thereof, in which the D-shaped cut section  32  is fitted. Accordingly, the second clutch section  42  is rotatable along with the push body  30  and reciprocally slidable along the axis of the push body  30  between a disengaging position and an engaging position. Multiple key slots  423  and keys  424  are alternately formed on outer circumference of the first end of the main body  421  in parallel to each other. Accordingly, when the second clutch section  42  is positioned in the engaging position, the first end of the main body  421  extends into the annular recess  411 . Under such circumstance, the key slots  423  and keys  424  of the second clutch section and the keys  412  and key slots  413  of the first clutch section are complementarily inserted in and engaged with each other. In this case, the first and second clutch sections  41 ,  42  are engaged and coupled with each other. When the second clutch section  42  is positioned in the disengaging position, the main body  421  of the second clutch section  42  is moved out of the annular recess  411 . Under such circumstance, the first and second clutch sections  41 ,  42  are disengaged and uncoupled from each other. At this time, the first and second clutch sections  41 ,  42  are independently from each other without drivingly engaged with each other. 
     The resilient member  44  is a compression spring fitted on the D-shaped cut section  32  of the push body  30 . Two ends of the resilient member  44  respectively abut against the end face of the second end of the main body  421  and the stopper member  43 . The resilient member  44  always exerts a resilient force onto the second clutch section  42  in a direction to the first clutch section  41  to make the main body  421  engaged in the annular recess  411 . 
     The shift section  50  includes an annular hook groove  51  formed on the circumference of the main body  421  and a shift body  52  having two arms extending from one end of the shift body  52  in a U-shaped configuration. A middle section of the shift body  52  is pivotally connected to a housing of the actuator, whereby the shift body  52  can be pivotally rotated. Free ends of the two arms of the shift body  52  are formed with oppositely extending hooks  521 . The hooks  521  are inlaid in the hook groove  51 , whereby when rotating the shift body  52 , the main body  421  is driven to move the second clutch section  42  from the engaging position to the disengaging position. 
     According to the above arrangement, in use of the quick-release mechanism  10 , a user only needs to pull an outward extending pull cord  60  to rotate the shift body  52  and shift the second clutch section  42  to the disengaging position. In this case, the worm wheel  20  is uncoupled from the push body  30 , permitting the push body  30  to be independently rotated and quickly restored to its home position. In comparison with the prior art, in addition to the convenient release, the quick-release mechanism  10  of the actuator of the present invention further has the following advantages:
     1. The first clutch section  42  of the clutch unit  30  of the quick-release mechanism  10  is not an independent component as in the prior art. Instead, the first clutch section  42  is integrally formed on the given worm wheel of the actuator. Accordingly, the clutch unit  30  has smaller number of components to achieve the same clutch effect as the prior art. Therefore, the quick-release mechanism  10  can be manufactured by simplified process at lower cost.   2. The first clutch section  42  is integrally formed on the worm wheel  20  of the actuator. Therefore, it is unnecessary to reserve an additional axial space on one side of the worm wheel  20  for accommodating the independent clutch component as in the prior art. Accordingly, the volume of the actuator is reduced as a whole. Moreover, the power transmission distance between the worm wheel  20  and the push body  30  is shortened, whereby the actuator can more precisely drive the push body.   

     The above embodiment is only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiment can be made without departing from the spirit of the present invention.