Abstract:
A drive structure for driving an upper thread wiper of a sewing machine is provided, wherein the upper thread wiper and a drive device for driving the upper thread wiper are disposed on the cantilever and located close to the end of the needle shaft. In addition to that the drive device simplifies relative motion transmission structure, the cooperative arrangement between the upper thread wiper and the drive device further improves the power transmission efficiency and stability. The upper thread wiper can be quickly and easily assembled onto or removed from the wiper arm through a quick release device. Moreover, the drive structure is further provided with a clutch device which is capable of effecting or interrupting power transmission as desired.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sewing machine, and more particularly to a drive structure for driving an upper thread wiper of a sewing machine. 
     2. Description of the Prior Art 
     Conventionally, the power source of a drive structure for an upper thread wiper of a sewing machine is transmitted by a mainshaft which is mounted on a base of the sewing machine, which a continuous power transmitting system. The structure of this kind of power transmitting system is complicated and difficult to adjust, and consequently has a high manufacturing and maintenance cost. Hence, the applicant of this application has invented “a coaxially clockwise driven needle shaft and upper thread wiper of a sewing machine”, wherein the structures of the power of the upper thread wiper and the needle shaft have been simplified. However, the applicant of the present invention is not satisfied with the improvement made in the “a coaxially clockwise driven needle shaft and upper thread wiper of a sewing machine” and has made further improvement to the drive structure for the upper thread wiper. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a drive structure for an upper thread wiper of a sewing machine, wherein the upper thread wiper and a drive device for driving the upper thread wiper are disposed on the cantilever and located close to the end of the needle shaft. In addition to that the drive device simplifies relative motion transmission structure, the cooperative arrangement between the upper thread wiper and the drive device further improves the power transmission efficiency and stability. 
     To achieve the above object, a drive structure for driving an upper thread wiper of a sewing machine, the sewing machine comprises a base and a cantilever extending from the base, on the cantilever is disposed a needle-shaft driving shaft for driving a needle shaft mounted on the cantilever to repeatedly move up and down. The upper thread wiper of the sewing machine is disposed on a wiper arm. A drive device is disposed between the needle-shaft driving shaft and the wiper arm. The drive device is provided with a drive member and a motion-transmission rod for converting rotation of the needle-shaft driving shaft into swing motion of the wiper arm. One end of the drive member is drivingly connected to and driven by the needle-shaft driving shaft. Another end of the driving member is pivoted to one end of the motion-transmission rod via a pin. Another end of the motion-transmission rod is formed with a cylindrical inserting portion. One end of the wiper arm is formed with a second pivot portion for insertion of a fixing pivot which is fixed to the cantilever, and the upper thread wiper is fixed at another end of the wiper arm, and the wiper arm is formed with a pivot hole for insertion of the inserting portion. 
     Another object of the present invention is to provide a drive structure for an upper thread wiper of a sewing machine, wherein the upper thread wiper can be quickly and easily assembled onto or removed from the wiper arm. 
     To achieve the above object, a quick release device is disposed between the upper thread wiper and the wiper arm. A free end of the wiper arm is an engaging end which is formed with a first stop portion. The upper thread wiper has a connecting end. The quick release device includes a positioning sleeve and a key, the positioning sleeve is formed with an inserting portion for accommodation of the connecting end and also for insertion of the engaging end of the wiper arm, the positioning sleeve includes an elastic portion which is provided with a spiral spring to push against the key, the positioning sleeve is formed with a second stop portion, the elastic portion is provided with an engaging portion to be elastically engaged with the first stop portion of the wiper arm, the key is formed with a first chamber for accommodation of the spring and the elastic portion so as to provide an elastic force for separating the key and the positioning sleeve from each other, the key is formed with an extending portion which extends toward the second stop portion, and at a distal end of the extending portion is formed a stop flange which is stopped and pressed against the second stop portion to make the engaging portion elastically engaged in the first stop portion, or pressing the key can make the engaging portion of the elastic portion disengage from the first stop portion, so that the upper thread wiper is removed from wiper arm. 
     Yet, another object of the present invention is to provide a drive structure for an upper thread wiper of a sewing machine, which is capable of effecting or interrupting power transmission. 
     To achieve the above object, the drive device is further provided with a clutch device for driving the needle shaft, the oscillating member is provided with a clutch hole for the clutch rod to engage in and disengage from the clutch hole, the clutch rod is pivotally inserted in the driven portion of the drive member, and one end of the clutch rod that extends out of the driven portion is driven by the clutch device, the clutch device includes a clutch member, a switch member, a press member, an flexible member, and a support pivot, the clutch member is slidably mounted on the needle-shaft driving shaft and fixed on the clutch rod, a push member is sleeved on the needle-shaft driving shaft to provide an elastic force to push the clutch member toward the drive member. 
     The switch member is formed with a third pivot portion for insertion of a pivot which is fixed on the cantilever, the switch member is formed with a push portion which extends toward the clutch member, so that the clutch member is pushed by the push member to rest against the push portion, when the switch member moves, the push portion will push the clutch member to make the clutch rod engage in or disengage from the oscillating member. 
     The support pivot is inserted through the press member and the flexible member and has one end fixed to the switch member and another screwed with a bolt, so that the flexible member is pushed by the bolt to provide a force for pushing the press member toward the cantilever, the press member is formed with a press portion for a user to press. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a drive structure for driving an upper thread wiper of a sewing machine in accordance with a first preferred embodiment of the present invention; 
         FIG. 2  is an assembly view of a drive device, a quick release device and a clutch device in accordance with the present invention; 
         FIG. 3  is an exploded view of the drive device, the quick release device and the clutch device in accordance with the present invention; 
         FIG. 4  is an operational view of the drive device of a drive structure for driving an upper thread wiper of a sewing machine in accordance with the present invention; 
         FIG. 5  is a side view showing that the drive member of the drive device in accordance with the present invention cooperates with the rod-inserting member; 
         FIG. 6  is a perspective view of a drive structure for driving an upper thread wiper of a sewing machine in accordance with a second preferred embodiment of the present invention; 
         FIG. 7  is a perspective view of a drive structure for driving an upper thread wiper of a sewing machine in accordance with a third preferred embodiment of the present invention; 
         FIG. 8  is an exploded view of a drive device of the present invention; 
         FIG. 9  is a cross sectional view of the drive device in accordance with the present invention; 
         FIG. 10  is an operational cross sectional view of the drive device in accordance with the present invention; and 
         FIG. 11  is an operational view of the assembly the drive device, the quick release device and the clutch device shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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. 
     Referring to  FIGS. 1-4 , a drive structure for driving an upper thread wiper  18  of a sewing machine  10  in accordance with a first preferred embodiment of the present invention is shown, wherein the sewing machine  10  essentially comprises a base  11  and an L-shaped cantilever  12  extending upward from the base  11 . In the base  11  is disposed a mainshaft  13  to be rotated by a motor (not shown). On the cantilever  12  is disposed a needle-shaft driving shaft  14  which is in parallel with and rotated by the mainshaft  13 . The needle-shaft driving shaft  14  has one end rotated by the mainshaft  13  and has another end provided with an oscillating member  17  which is connected by a connecting rod  16  to a connecting block  150  disposed on a needle shaft  15 , so that the needle shaft  15  is driven by the needle-shaft driving shaft  14  to repeatedly move up and down. Since the driving structure for driving the needle shaft  15  to move is a conventional structure, further descriptions are omitted. 
     The upper thread wiper  18  of the sewing machine  10  is driven by a wiper arm  19 , and this is also a conventional structure. The present invention is characterized in that a drive device  20  is disposed between the oscillating member  17  for driving the needle shaft  15  and the wiper arm  19 , so as to make the wiper arm  19  swing horizontally, unlike the conventional up-and-down movement of the needle shaft  15  driven by the needle-shaft driving shaft  14 . 
     Referring to  FIGS. 3 and 4 , the oscillating member  17  is such a structure that the outer diameter at both ends of the oscillating member  17  is larger than the outer diameter in the middle portion of the oscillating member  17 . One end of the oscillating member  17  is formed an inserting hole  170 , and the needle-shaft driving shaft  14  is inserted and fixed in the inserting hole  170  of the oscillating member  17  by bolts  171 . Another end of the oscillating member  17  is connected to one end of the connecting rod  16  by a connecting shaft  172 , and another end of the connecting rod  16  is pivoted to the connecting block  150  and serves to drive the needle shaft  15  to move. In the middle portion of the oscillating member  17  is defined a clutch hole  173  for insertion of one end of a clutch rod  174 , and another end of the clutch rod  174  is connected to the drive device  20 . 
     The drive device  20  is provided with a drive member  21 , a motion-transmission rod  22 , a rod-inserting member  23 , an oscillating element  24  and a linking rod  25  which are interconnected to one another and serve to transmit power to the wiper arm  19 . The drive member  21  is an elongated block whose middle portion is slightly bent, in the middle portion of the drive member  21  is formed a through hole  210  for insertion of the needle-shaft driving shaft  14 , one end of the drive member  21  is formed with a driven portion  211  in the form of a hole for insertion of the clutch rod  174 , and another end of the drive member  21  is formed with two ears  212 . The motion-transmission rod  22  has one end inserted between the two ears  212 , each of the ears  212  is formed with a pin hole  213 , and a pin  214  is inserted through the pin holes  213  of the ears  212  and the end of the motion-transmission rod  22 , so that the motion-transmission rod  22  is pivoted to the drive member  21  by the pin  214 . 
     The end of the motion-transmission rod  22  inserted between the ears  212  is formed with a first pivot portion  220  which includes two opposed flat surfaces and two opposed arc-shaped surfaces (not numbered). The pin  214  is inserted through the two opposed flat surfaces, and there is a clearance between the first pivot portion  220  and the two ears  212 , so that the first pivot portion  220  can move along the pin  214  between the two ears  212  so as to absorb the displacement of the motion-transmission rod  22  caused when the motion-transmission rod  22  moves up and down while being driven to swing back and forth by the drive member  21 , and caused by the horizontal swing of the rod-inserting member  23 . At a bottom of the first pivot portion  220  is a cylindrical first inserting portion  221  whose outer diameter is smaller than that of the first pivot portion  220 . 
     The rod-inserting member  23  is L-shaped and includes a perpendicular inserting rod  230  at one end thereof. The first inserting portion  221  of the motion-transmission rod  20  is inserted through the inserting rod  230 , and on an end of the first inserting portion  221  that extends out of the inserting rod  230  is sleeved an elastic member  222 . The end of the first inserting portion  221  that extends out of the inserting rod  230  is formed with an annular groove (not numbered) in which a washer (not numbered) and a C-shaped retainer  223  are engaged to prevent the elastic member  222  from disengaging from the first inserting portion  221 . The elastic member  222  has one end pushed against the end of the inserting rod  230  of the rod-inserting member  23 , so as to provide an elastic force between the rod-inserting member  23  and the motion-transmission rod  22 , making the rod-inserting member  23  and the motion-transmission rod  22  slide more stably with respect to each other. 
     Another end of the rod-inserting member  23  is U-shaped to form a shaft-retaining portion  231  in the form of a hole and a slit  232  in communication with the shaft-retaining portion  231 . A rotary shaft  234  has one end inserted in the shaft-retaining portion  231 , and a bolt  233  is screwed through the slit  232  to retain the rotary shaft  234  within shaft-retaining portion  231  in a clamping manner, so that the rotary shaft  234  can be driven to rotate by the rod-inserting member  23 . 
     One end of the oscillating element  24  is formed with a rotary-shaft hole  240  for insertion of another end of the rotary shaft  234 , and two bolts  241  are laterally screwed in the rotary-shaft hole  240  to fix the rotary shaft  234 , so that the oscillating element  24  is drivingly connected to the rotary shaft  234 . At another end of the oscillating element  24  is formed a horizontal oscillating portion  242  which is formed with a central hole  243  for insertion of a first bolt  244 , so as to pivotally connect the oscillating element  24  to the linking rod  25 . 
     The linking rod  25  is an elongated block with two circular ends. Each end of the linking rod  25  is formed with a bolt hole  250  for insertion of the first bolt  244  and a second bolt  251 , respectively, and the second bolt  251  has one end inserted in the wiper arm  19  so as to drive the wiper arm  19 . 
     The wiper arm  19  is an L-shaped structure, and one end of the wiper arm  19  is formed with a cylindrical hollow second pivot portion  190  which is to be pivotally connected a corresponding part of the cantilever  12 . For example, in the second pivot portion  190  is inserted a fixing pivot  260  which has one end fixed to a first corner of a triangle mounting frame  26 , the rotary shaft  234  is pivoted to a second corner of the mounting frame  26 , and another fixing pivot  260  is fixed to a third corner of the mounting frame  26 , so as to fix the mounting frame  26  to a bottom of the cantilever  12 . 
     At a middle portion of the wiper arm  19  is defined a pivot hole  191  for insertion the one end of the second bolt  251 , and a bolt  192  is laterally screwed in the pivot hole  191  to fix the second bolt  251 , so that the wiper arm  19  is pivotally and drivingly connected to the linking rod  25 . 
     When the needle-shaft driving shaft  14  rotates back and forth, the drive member  21 , the drive member  21  will swing synchronously and coaxially with the oscillating member  17  since it is drivingly connected to the oscillating member  17  by the clutch rod  174 . The motion-transmission rod  22 , as shown in  FIGS. 4 and 5 , will move up and down repeatedly between two positions a 1  and b 1  to make the inserting rod  230  of the rod-inserting member  23  and the first inserting portion  221  slide with respect to each other. Meanwhile, the inserting rod  230  moves horizontally between the positions a 1  and b 1 , so that the rotary shaft  234  at another end of the rod-inserting member  23  will have a rotating angle θ, and the oscillating element  24  will rotate by the rotating angle θ. Consequently, the first bolt  244  of the linking rod  25  is driven to move repeatedly between two positions a 2  and b 2 , and the second bolt  251  of the linking rod  25  is driven to move repeatedly between two positions a 3  and b 3 , so that the wiper arm  19  will rotate around the second pivot portion  190  to drive the upper thread wiper  18  to rotate. 
     A drive device  20  in accordance with a second embodiment of the present invention can also be simplified as shown in  FIG. 6 , wherein the drive member  21  and the oscillating member  17  on the needle-shaft driving shaft  14  can be integral with each other, so that the power can be transmitted directly to the drive member  21  and the oscillating member  17  from the needle-shaft driving shaft  14 . The drive member  21  is pivoted to a motion-transmission rod  22  which has an first inserting portion  221  inserted in the pivot hole  191  of the wiper arm  19 , and on an end of the first inserting portion  221  that extends out of the pivot hole  191  are sleeved an elastic member  222  and a C-shaped retainer  223 . The second pivot portion  190  at one end of the wiper arm  19  is pivoted to a corresponding part of a sewing machine, and another end of the wiper arm  19  is assembled to the upper thread wiper  18 . The drive device  20  of this embodiment is also capable of transmitting power as the drive device  20  of the first embodiment. The drive member  21  has two ears  212  at two ends thereof, a pin  214  is inserted through the two ears  212 . The end of the motion-transmission rod  22  inserted between the ears  212  is a formed with a first pivot portion  220  for insertion of the pin  214 , there is a clearance between the first pivot portion  220  and the two ears  212 , and another end of the oscillating member  17  is drivingly connected to the needle shaft  15  by a connecting shaft  172 . 
     Further, a drive device  20  in accordance with a third embodiment of the present invention can also be simplified as shown in  FIG. 7 , wherein the drive member  21  and the oscillating member  17  on the needle-shaft driving shaft  14  can be integral with each other, so that the power can be transmitted directly to the drive member  21  and the oscillating member  17  from the needle-shaft driving shaft  14 . The drive member  21  is pivoted to a motion-transmission rod  22  which has a first inserting portion  221  inserted in one end of an oscillating element  24 . The oscillating element  24  has a middle portion pivoted in the cantilever  12  and another end pivoted to one end of a linking rod  25 , and another end of the linking rod  25  is pivoted in a pivot hole  191  of the wiper arm  19  to drive the wiper arm  19  to swing. 
     In the middle portion of the oscillating element  24  is defined a rotary-shaft hole  240  for insertion of a connecting pivot  245  fixed on the cantilever  12 , and both ends of the oscillating element  24  are formed with an passing hole  246  for insertion of the first inserting portion  221 . On an end of the first inserting portion  221  that extends out of the passing hole  246  are sleeved an elastic member  222  and a C-shaped retainer  223 , so as to provide an elastic force between the first inserting portion  221  and the oscillating element  24 . 
     At another end of the oscillating element  24  is formed a horizontal oscillating portion  242  which is formed with a central hole  243  for insertion of a first bolt  244 , so as to pivotally connect the oscillating element  24  to the linking rod  25 . 
     The linking rod  25  is an elongated block with two circular ends. Each end of the linking rod  25  is formed with a bolt hole  250  for insertion of the first bolt  244  and a second bolt  251 , respectively, and the second bolt  251  has one end inserted in the wiper arm  19  so as to drive the wiper arm  19 . 
     At a middle portion of the wiper arm  19  is defined a pivot hole  191  for insertion the one end of the second bolt  251 , and a bolt is laterally screwed in the pivot hole  191  to fix the second bolt  251 , one end of the wiper arm  19  is formed with a second pivot portion  190  which is to be pivotally connected a corresponding part of the cantilever  12 , and another end of the wiper arm  19  is assembled to the upper thread wiper  18 . The drive device  20  of this embodiment is also capable of transmitting power as the drive device  20  of the first embodiment. The drive member  21  has two ears  212  at two ends thereof, a pin  214  is inserted through the two ears  212 . The end of the motion-transmission rod  22  inserted between the ears  212  is a formed with a first pivot portion  220  for insertion of the pin  214 , there is a clearance between the first pivot portion  220  and the two ears  212 , and another end of the oscillating member  17  is drivingly connected to the needle shaft  15  by a connecting shaft  172 . 
     Between the upper thread wiper  18  and the wiper arm  19  can also be disposed a quick release device  30  and corresponding structures for enabling the upper thread wiper  18  to be quickly assembled onto or removed from the wiper arm  19 , as shown in  FIGS. 3 ,  8 - 10 , the quick release device  30 , wherein the free end of the wiper arm  19  is formed with a laminar engaging end  193  which is formed with a first stop portion  194  in the form of a cavity opens upward. Adjacent to the first stop portion  194  is disposed a laminar elastic piece  195  which is bent upward to provide an upward elastic force. 
     The upper thread wiper  18  has a hooking end for cooperating with the needle shaft  15  to hook thread, another end of the upper thread wiper  18  is a horizontal connecting end  180  which is formed with two threaded connecting holes  182 , and at both sides of the connecting end  180  is formed a protruding third stop portion  181 . 
     The quick release device  30  includes a positioning sleeve  31  and a key  32 . The positioning sleeve  31  is rectangular in cross section and formed with an second inserting portion  310  which has a width approximately equal to that of the connecting end  180  so as to accommodate the connecting end  180 . At an opening end of the second inserting portion  310  are formed two concave engaging portions  311  for engaging with the stop portions  181 . Two bolts  33  are inserted through a bottom surface of the positioning sleeve  31  and screwed into the connecting holes  182  of the connecting end  180 , and the engaging end  193  of the wiper arm  19  is inserted in the second inserting portion  310 . 
     At a top surface of the positioning sleeve  31  are formed two parallel slots  312  so as to create an elastic portion  313  which is integral with the positioning sleeve  31  at a position close to the engaging end  193  of the wiper arm  19  and has a free end extending toward the upper thread wiper  18 . The free end of the elastic portion  313  extends out of the second inserting portion  310  and is formed with a positioning groove  314  for holding one end of a spiral spring  34 , and another end of the spiral spring  34  is pushed against the key  32 . At the opening end of the second inserting portion  310  of the positioning sleeve  31  is formed a U-shaped second stop portion  315  which is located above the free end of the elastic portion  313  to restrict the key  32 . The elastic portion  313  is provided at a bottom surface thereof with a triangle protruding engaging portion  316  to be elastically engaged with the first stop portion  194  of the wiper arm  19 , as shown in  FIG. 9 . 
     The key  32  is a rectangular block which is formed with a first chamber  320  which opens toward the positioning sleeve  31  for accommodation of the spiral spring  34  and the free end of the elastic portion  313 . The spiral spring  34  pushes against the bottom of the first chamber  320  to provide an elastic force for separating the key  32  and the positioning sleeve  31  from each other. At an upper edge of an opening end of the first chamber  320  is formed an extending portion  321  which extends toward the second stop portion  315 , and at a distal end of the extending portion  321  is formed a stop flange  322  perpendicular to the extending portion  321 . At the corner defined between the extending portion  321  and the stop flange  322  are formed two slanting guide portions  323  which are lower than the stop flange  322 , and at a top surface of each of the guide portions  323  is formed a horizontal stop surface  324 . 
     The key  32  is sleeved on the free end of the elastic portion  313  in such a manner that the stop flange  322  is inserted into the positioning sleeve  31  and stopped against the second stop portion  315 . When the key  32  is pressed to compress the spiral spring  34 , the extending portion  321  of the key  32  is located under the second stop portion  315 , the free end of the elastic portion  313  is elastically deformable upward and downward. At this moment, as shown in  FIG. 10 , the engaging portion of the elastic portion  313  can be disengaged from the first stop portion  194  by pulling the upper thread wiper  18  from the wiper arm  19 , and thus the upper thread wiper  18  can be removed from wiper arm  19 . Similarly, to assemble the upper thread wiper  18  to the wiper arm  19 , the key  32  is firstly pressed to make the engaging portion  316  elastically engaged in the first stop portion  194 , when the key  32  is released, it will be pushed back by the spiral spring  34  to the position where the stop flange  322  is stopped against the second stop portion  315  again, and the key  32  and the free end of the elastic portion  313  will be pressed toward the first stop portion  194  of the wiper arm  19 , so that the engaging portion  316  is engaged in the first stop portion  194  to prevent the upper thread wiper  18  from disengaging from the wiper arm  19 , as shown in  FIG. 9 . 
     Moreover, the drive device  20  is further provided with a clutch device  40  for driving the needle shaft  15 , as shown in  FIGS. 1-3 , the oscillating member  17  is provided with a clutch hole  173  for the clutch rod  174  to insert in and out. The clutch rod  174  is pivotally inserted in the driven portion  211  of the drive member  21 , and the end of the clutch rod  174  that extends out of the driven portion  211  is driven by the clutch device  40 , so as to control the clutch rod  174  to insert in or disengage from the clutch hole  173  of the oscillating member  17 . 
     The clutch device  40  includes a clutch member  41 , a switch member  42  for controlling the position of the clutch member  41 , a press member  43 , a flexible member  44  in the form of a spiral spring, and a support pivot  45  fixed to the switch member  42 . At the bottom of the cantilever  12  is provided a base frame  121  for mounting the aforementioned structures. The base frame  121  is bent to form an L-shaped structure and has a vertical end fixed to a rear surface of the cantilever  12  by two bolts. A horizontal end of the base frame  121  is formed with a limiting hole  122  located adjacent to the vertical end, and is further formed with two symmetrical first positioning portions  123  and  124  and a connecting portion  125  connected between the two first positioning portions  123 ,  124  in such a manner that the two first positioning portions  123 ,  124  are two holes located on the same circle whose center is the limiting hole  122 , and a width of the connecting portion  125  is smaller than a diameter of the two first positioning portions  123 . 
     The clutch member  41  of the clutch device  40  is a disc-shaped structure and formed with a driving-shaft hole  410  for insertion of the needle-shaft driving shaft  14 , so that the clutch member  41  is slidably mounted on the needle-shaft driving shaft  14 . Around a periphery of the clutch member  41  is formed a positioning hole  411  for insertion of the clutch rod  174  when the clutch rod  174  is in parallel to the needle-shaft driving shaft  14 . A push member  412  in the form of a spiral spring is sleeved on the needle-shaft driving shaft  14  and biased between the driving-shaft hole  410  of the clutch member  41  and the needle-shaft driving shaft  14  to provide an elastic force for the clutch member  41  to push the clutch rod  174  toward the drive member  21 . 
     The switch member  42  is a polygonal plate abutted against a top surface of the horizontal end of the base frame  121 , and at one end of the switch member  42  is formed a third pivot portion  420  in the form of a hole. A pivot  46  is inserted through the limiting hole  122  and the third pivot portion  420  and retained by a C-shaped retainer. At the middle portion of a top surface of the switch member  42  is formed a cylindrical push portion  421  which extends to an end of the clutch member  41  that is not pushed by the push member  412 , so that the clutch member  41  can be pushed by the push member  412  to rest against the push portion  421 , and thus the clutch member  41  can be driven to move by the push portion  421 . When the switch member  42  moves, the push portion  421  will push the clutch member  41  to make the clutch rod  174  engage in or disengage from the oscillating member  17 . 
     The press member  43  is disposed below the horizontal end of the base frame  121  and aligned with the first positioning portions  123 ,  124  and the connecting portion  125 . The press member  43  is formed with a second chamber  430  open downward for accommodation of the flexible member  44 . The support pivot  45  is inserted through the flexible member  44  and the second chamber  430  and fixed by a bolt  450 , so that the flexible member  44  is pushed by the bolt  450  toward the bottom of the second chamber  430 , so as to provide a force for pushing the press member  43  toward the bottom surface of the horizontal end of the base frame  121 . At a top surface of the press member  43  is formed a protruding second positioning portion  431  to be selectively engaged with the first positioning portions  123  and  124 . At a bottom surface of the press member  43  is formed a press portion  432  which horizontally extends out of the press member  43 , so that the user can press the press portion  432  and push it to move along the connecting portion  125  to control the positions of the switch member  42  and the clutch member  41 , so as to effect or interrupt power transmission. 
     When the second positioning portion  431  of the press member  43  is engaged in the positioning portion  123  of the drive member  21 , the switch member  42  which is driven by the press member  43  via the support pivot  45  will rotate around the pivot  46  to rotate to the push portion  421  and toward the drive member  21 . The clutch member  41  will drive the clutch rod  174  to move toward the drive member  21 , so that the clutch rod  174  can be inserted into the clutch hole  173  of the oscillating member  17  to effect power transmission. When the second positioning portion  431  of the press member  43  is engaged in the positioning portion  124  of the drive member  21 , the switch member  42  is simultaneously driven to rotate to the push portion  421  to push the clutch member  41  to move away from the drive member  21 , the clutch rod  174  will be disengaged from the clutch hole  173  of the oscillating member  17  to interrupt power transmission, namely, the power from the needle shaft  15  will be blocked from being transmitted to the upper thread wiper  18 . 
     The rotary shaft  234  of the mounting frame  26  and the fixing pivot  260  can be pivoted or fixed to the bottom surface of the horizontal end of the base frame  121 . 
     What mentioned above are the structural relations of the main components of the present invention, for a better understanding of the function and operation of the present invention, please refer to the following descriptions. 
     Firstly, the power of the drive device  20  for driving the upper thread wiper  18  directly comes from the needle-shaft driving shaft  14  that drives the needle shaft  15  instead of coming from the base  11  of the sewing machine, so that the structure of the sewing machine base is simplified. The drive device  20  is directly mounted on the cantilever  12 , so that it can move synchronously with the needle shaft  15 , reducing action error and power loss. 
     Secondly, the drive device  20  is located on the cantilever  12  which is within the user&#39;s vision, instead of on the base  11  or at the bottom of the sewing machine  10  which is beyond the user&#39;s vision, making the maintenance, operation and assembly of the drive device  20  much easier. 
     Thirdly, the quick release device  30  enables the upper thread wiper  18  to be quickly assembled onto or removed from the wiper arm  19 . 
     Fourthly, the user can press the clutch device  40  to effect or interrupt power transmission while doing sewing, making the power transmission control easier. Furthermore, the press member  43  uses the second positioning portion  431  to selectively engage with the two symmetrical first positioning portions  123  and  124 , improving the positioning effect of the clutch. 
     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.