Abstract:
A travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism comprises a fixed holder, a positioning holder and an adjusting apparatus. By adjusting the relative position of the center of the rotating element of the motor and the control shaft using the adjusting apparatus, the control element on one end of the control shaft will rotate synchronously, and a mechanism connected to the other end of the control shaft will also rotate to a beginning and an end points of a different travel. By such arrangements, when the control element is driven by the motor, the mechanism connected to the control shaft will operate according to different travels, thus achieving the objective of adjusting travel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sewing machine, and more particularly to a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism. 
     2. Description of the Prior Art 
     A sewing machine has many reciprocating mechanisms such as needle, cloth delivering gear and shuttle that all move in a reciprocating manner or produce a travel that the reciprocating rotary motion is converted to the reciprocating linear motion. To avoid unwanted loosening after adjustment which can lead to uncertain operation, the conventional sewing machines rarely have an adjustable structure. 
     In view of this, the inventor of the present invention has developed a beginning/end adjusting positioning structure for a travel of a sewing machine motor drive mechanism. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism, an adjusting apparatus is disposed between the positioning holder fixing the motor and the fixed holder fixed on the sewing machine. A control shaft is pivotally inserted through the positioning holder and the fixed holder, so that the positioning holder can rotate around the control shaft. The rotating element of the motor is engaged with the control element on one end of the control shaft, and the other end of the control shaft is provided with a swing arm. The rotating element of the motor rotates back and forth to drive the control element to swing back and forth, and thus the swing arm on the other end of the control shaft will produce a back and forth travel. When the adjusting apparatus performs the adjustment, the positioning holder can rotate around the control shaft, synchronously driving the control element and the control shaft to rotate an adjusting angle to achieve the adjustment objective. 
     The secondary objective of the present invention is provide a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism, through cooperation of the locking element in the adjusting apparatus and the positioning portion of the positioning holder, the locking element can enhance the stability of the adjusting positioning structure of the present invention during the adjustment. 
     To achieve the above objectives, a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism in accordance with the present invention is provided, the sewing machine includes a control shaft, on the control shaft is provided a control element, and the travel beginning/end adjusting positioning structure comprises a fixed holder, a positioning holder and an adjusting apparatus. The fixed holder includes a through hole and a fixing portion. The fixing portion includes an insertion hole. The fixed holder is fixed on the base of the sewing machine. The positioning holder is provided with a through hole in alignment with the through hole of the fixed holder, and a positioning portion opposite the fixing portion of the fixed holder. The positioning portion is formed with a through hole. The fixed holder has a side for mounting a motor, and a rotating shaft of the motor is inserted through the through hole of the fixed holder and the through hole of the fixed holder. A rotating element is mounted on the rotating shaft of the motor and engaged with the control element of the control shaft. The adjusting apparatus includes an adjusting element, and a locking element screwed to the adjusting element. The locking element is in the form of a column and formed with an arc peripheral surface and a threaded hole in the arc peripheral surface. The adjusting shaft of the adjusting element is inserted through the fixing portion of the fixed holder and the through hole of the positioning portion of the positioning folder, and the locking element is screwed with the adjusting element. The arc peripheral surface of the locking element is partially engaged in the through hole of the positioning portion. By such arrangements, adjusting the adjusting element of the adjusting apparatus can control the rotating element assembled on the rotating shaft of the motor of the positioning holder to rotate an angle around the control shaft, synchronously changing the position of the respective elements connected to the rotating element, so that the travel of the swing mechanism connected to the control shaft can be assuredly adjusted and positioned. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective assembly view of a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism in accordance the present invention; 
         FIG. 2  is a perspective exploded view of the travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism in accordance the present invention; 
         FIG. 3  is a planar end view of the travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism (not adjusted) in accordance the present invention; 
         FIG. 4  is a perspective view showing that the locking element of the adjusting apparatus is partially engaged in the through hole of the positioning portion in accordance with the present invention; 
         FIG. 5  is a side view of the adjusting apparatus which has performed the adjustment in accordance with the present invention; 
         FIG. 6  is an operational view showing how the adjusting apparatus performs the adjustment in accordance with the present invention; 
         FIG. 7  is a top view showing that the locking element is provided with a limiting cylinder on each of two opposite ends thereof; 
         FIG. 8  is a perspective view showing that the locking element is provided with the limiting cylinder on each of two opposite ends thereof; 
         FIG. 9  is a planar view showing that the locking element is partially engaged in the positioning portion of the positioning holder and limited by the limiting portions of the positioning portion; 
         FIG. 10  is a perspective view showing that the locking element is partially engaged in the positioning portion of the positioning holder and limited by the limiting portions of the positioning portion; and 
         FIG. 11  is a planar view showing that the head portion of the adjusting element includes a stopping surface. 
     
    
    
     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. 1-3  showing a travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism in accordance with a preferred embodiment of the present invention, the sewing machine  10  is provided with a control shaft  20  on a base  11  thereof. A first end of the control shaft  20  is provided with a swing arm  21  which is drivingly connected to a cloth delivering gear, and on a second end of the control shaft  20  is provided a control element  22  in the form of a sector gear. The travel beginning/end adjusting positioning structure for a sewing machine motor drive mechanism in accordance with the present invention comprises a fixed holder  30 , a positioning holder  40  and an adjusting apparatus  50 . 
     The fixed holder  30  is plate-shaped and includes a central through hole  31 , and a pivoting hole  32  in a top end thereof. The fixed holder  30  is further provided with a fixing portion  33  vertically bent from a bottom end thereof. The fixing portion  33  includes an elongated insertion hole  331 . The fixed holder  30  is fixed on the base  11  of the sewing machine  10 . 
     The positioning holder  40  is plate-shaped and provided with a through hole  41  in alignment with the through hole  31  of the fixed holder  30 , and a pivot hole  42  in alignment with the pivoting hole  32  of the fixed holder  30 . The positioning holder  40  and the fixed holder  30  are pivotally connected by inserting a pivot element  43  through the pivoting hole  32  of the fixed holder  30  and the pivot hole  42  of the positioning holder  40 . The positioning holder  40  is further provided with a positioning portion  44  which is vertically bent from a bottom end thereof opposite the fixing portion  33  of the fixed holder  30 . The positioning portion  44  is formed with a through hole  441 . The fixed holder  30  has a side for mounting a motor  60 , and a rotating shaft  61  of the motor  60  is inserted through the through hole  41  of the fixed holder  30  and the through hole  31  of the fixed holder  30 . A rotating element  62  is mounted on the rotating shaft  61  of the motor  60 . Furthermore, the pivot element  43  in the present embodiment is provided with a pivot sleeve  430  extending toward the pivoting hole  32  and the pivot hole  42 . The pivot sleeve  430  is centrally hollow in such a manner that the control shaft  20  can be rotatably inserted through the pivot sleeve  430 , and the positioning holder  40  is rotatably mounted on the pivot sleeve  430  without direct contacting the control shaft  20 , avoiding the improper friction due to contact between the control shaft  20  and the positioning holder  40 . 
     The adjusting apparatus  50  includes an adjusting element  51  and a locking element  52  screwed to the adjusting element  51 . The adjusting element  51  is a screw and has a disc-shaped head portion  510  and a threaded adjusting shaft  511  which extends from a center of the head portion  510  and is smaller in outer diameter than the head portion  510 . The locking element  52  is in the form of a column and formed with an arc peripheral surface  520  opposite the through hole  441 . In the arc peripheral surface  520  is formed a threaded hole  521  in alignment with the adjusting shaft  511 . The adjusting apparatus  50  is assembled in such a manner that the adjusting shaft  511  of the adjusting element  51  is inserted through the insertion hole  331  of the fixing portion  33  of the fixed holder  30  and the through hole  441  of the positioning portion  44  of the positioning folder  40  and screwed into the threaded hole  521  of the locking element  52 , and the head portion  510  abuts against the fixing portion  33  outside the insertion hole  331 . The arc peripheral surface  520  of the locking element  52  is engaged in the through hole  441  of the positioning portion  44  of the positioning holder  40 , as shown in  FIG. 4 , so that the adjusting element  51  of the adjusting apparatus  50  can be rotated to make the locking element  52  move close to or away from the head portion  510  of the adjusting element  51 , adjusting the relative position of the positioning holder  40  and the fixed holder  30 . 
     In the present embodiment, the adjusting apparatus  50  is further provided with an elastic element  53  mounted on the adjusting element  51 , and both ends of the elastic element  53  push against the fixing portion  33  of the fixed holder  30  and the positioning portion  44  of the positioning holder  40  for providing an elastic prestress to the positioning holder  40 , the fixed holder  30  and to the whole adjusting apparatus  50 , thus making sure that the adjusting apparatus  50  is kept in the positioned state after adjustment. 
     The aforementioned is the summary of the positional and structural relationship of the respective components of the preferred embodiment in accordance with the present invention. 
     For a better understanding of the present invention, its operation and function, reference should be made to the following description: 
     When in use, as long as the adjusting element of the adjusting apparatus  50  is adjusted by rotation, the locking element  52  screwed on the adjusting element  51  will rotate along the thread on the adjusting element  51  to push the positioning portion  44  of the positioning holder  40  to move, further changing the distance between the fixing portion  33  of the fixed holder  30  and the positioning portion  44  of the positioning holder  40 . As shown in  FIG. 5 , the positioning holder  40  is made to pivot around the pivot sleeve  430  of the pivot element  43 . Referring to  FIG. 6 , since the positioning portion  44  pivots around the pivot sleeve  430  by an adjusting angle θ, the motor  60  on the positioning holder  40  will also rotate the angle θ. Since the rotating element  62  of the motor  60  is engaged with the control element  22 , the control shaft  20  on the control element  22  will also rotate the adjusting angle θ, and so will the swing arm  21  on the first end of the control shaft  20 , moving the distal end of the swing arm  21  which was originally at a middle point O 1  of the travel to a secondary middle point O 2 , so that the beginning point a 1  and the end point a 2  of the travel a 1   a   2  which were originally formed around the middle point O 1  will be changed to the travel beginning point b 1  and the travel end point b 2  of the travel b 1   b   2 , immediately making the beginning and end points of the travel of the swing arm rotate. By such arrangements, it can effectively and immediately adjust the travel of a structure connected to the distal end of the swing arm  21  to satisfy the requirements of the actual operation, adjusting the error in the production conveniently and quickly. 
     Through cooperation of the through hole  441  of the positioning portion  44  of the positioning holder  40  and the locking element  52 , the locking element  52  is prevented from rotating around an axis of the adjusting shaft  511  of the adjusting element  51 . Through cooperation of the peripheral surface of the locking element  52  and the through hole  441 , the locking element  52  can rotate around the peripheral surface thereof, so that while the adjusting element  51  is adjusted by rotation, the locking element  52  can rotate along with the adjusting shaft  511  of the adjusting element  51 . 
     The through hole  441  is formed into a square through hole, and the locking element  52  is in the form of a column, so that when the adjusting shaft  511  of the adjusting element  51  is inserted through the through hole  441  and screwed into the threaded hole  521  of the locking element  52 , the arc peripheral surface  520  of the locking element  52  will be partially engaged in the through hole  441  of the positioning portion  44  of the positioning holder  40 , preventing the locking element  52  from rotating around the axis of the adjusting shaft  511 . Hence, it can avoid the loosening of the locking element  52  when the motor  60  vibrates, further enhancing the stability of the present invention. 
     In addition, when the locking element  52  presses against the positioning portion  44  of the positioning holder  40 , since the locking element  52  is in the form of a column, besides that the peripheral surface  520  of the locking element  52  is partially engaged in the through hole  441  of the positioning portion  44  of the positioning holder  40 , the locking element  52  will contact the positioning portion  44  with both upper and lower sides thereof being pressed against by the positioning portion  44 . Moreover, when the adjusting element  51  is adjusted to make the positioning portion  44  of the positioning holder  40  move, the positioning portion  44  will lean slightly due to pivoting. Since the locking element  52  is in the form of a column, it will rotate to cooperate with the positioning portion  44  in the extending direction of the arc peripheral surface  520  no matter how many degrees the positioning portion  44  leans. In terms of the present embodiment, the locking element  52  in the form of a column rotates around the axis of the column to keep the arc peripheral surface  520  pressing against the upper and the lower sides of the positioning portion  44  without leading to adjustment error. 
     Referring to  FIGS. 7 and 8 , the locking element  52  in the above embodiment can also be coaxially provided on each of two end surfaces thereof with a limiting cylinder  522  which is smaller in diameter than the locking element  52 , so that when the arc peripheral surface  520  of the locking element  52  is partially engaged in the through hole  441  of the positioning portion  44  of the positioning holder  40 , the two limiting cylinders  522  can push against side surfaces of the positioning portion  44  for assisting limiting the locking element  52  to the positioning portion  44 , enhancing the firmness of the locking element  52 . 
     Referring to  FIGS. 9 and 10 , the positioning portion  44  of the positioning holder  40  in the above embodiment can also be provided with a limiting portion  442  protruding at each of two opposite sides of the through hole  441  in such a manner that the locking element  52  can be arranged between the two limiting portions  442  for enhancing the stability of the locking element  52 . 
     Referring to  FIG. 11 , the head portion  510  of the adjusting element  51  can also be formed with an arc convex stopping surface  512  on an end thereof which contacts the fixing portion  33 . By partially engaging the stopping surface  512  in the insertion hole  331 , the head portion  510  of the adjusting element  51  can be automatically aligned with the center of the insertion hole  331 . Further, under the action of the elastic prestress provided by the elastic element  53 , the adjusting element  51  can be assuredly maintained in alignment with the center of the insertion hole  331 , keeping the whole adjusting apparatus  50  in the optimal cooperation state. 
     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.