Patent Publication Number: US-6904853-B2

Title: Take-up cam phase adjustment structure of looper thread take-up apparatus of a sewing machine

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is related to a take-up cam phase adjustment structure of looper thread take-up apparatus of a sewing machine. A locking member (such as a screw) for locking the driven wheel on the rotary shaft is positioned on outer side of the housing of the sewing machine. After the locking member is unscrewed and loosened, the phase of the take-up cam mounted in the housing can be directly adjusted from outer side of the housing. 
   2. Description of the Prior Art 
   This applicant&#39;s U.S. patent application Ser. No. 10/303,959, filed on Nov. 26, 2002, entitled “SEWING MACHINE”, now U.S. Pat. No. 6,668,739, discloses a looper thread take-up structure 23. By means of turning the looper thread take-up structure 23, the relative phase between the looper thread take-up structure 23 and the take-up cam 46 can be adjusted. In order to more conveniently adjust the relative phase between the looper thread take-up structure 23 and the take-up cam 46, the present invention provides a take-up cam phase adjustment structure of the looper thread take-up apparatus of a sewing machine. The take-up cam phase adjustment structure can be easily directly adjusted from outer side of the housing of the sewing machine. 
   SUMMARY OF THE INVENTION 
   It is therefore a primary object of the present invention to provide a take-up cam phase adjustment structure of looper thread take-up apparatus of a sewing machine. The sewing machine includes a lower driving shaft for driving a lower knotting hook. The looper thread take-up apparatus of the sewing machine includes: a rotary shaft pivotally mounted in the sewing machine; a take-up cam tightly fixed on a second end of the rotary shaft; a thread-guiding plate mounted on the housing for correspondingly pressing a stitching thread against the rim of the take-up cam; and a transmission mechanism connected between the lower driving shaft and the rotary shaft. The transmission mechanism includes a transmission wheel coupled with the lower driving shaft of the sewing machine and a driven wheel coupled with the rotary shaft. The take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine includes: a first locking member for locking the transmission wheel on the lower driving shaft; a second locking member for locking the driven wheel on the rotary shaft; and a turning section disposed at one end of the rotary shaft. After an operator unscrews and loosens any of the first and second locking members, by means of rotating the turning section, the relative radial positions between the take-up cam and the lower driving shaft is drivingly adjustable. 
   It is a further object of the present invention to provide the above take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine. One end of the lower driving shaft and/or a first end of the rotary shaft outward protrudes from a first sidewall of the housing of the sewing machine. 
   It is still a further object of the present invention to provide the above take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine, in which another turning section is further disposed at the other end of the rotary shaft. 
   It is still a further object of the present invention to provide the above take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine, in which the turning section is a groove. 
   It is still a further object of the present invention to provide the above take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine, in which the tuning section is a protruding plate. 
   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 the present invention; 
       FIG. 2  is a perspective assembled view of the present invention; 
       FIG. 3  is a top view of the sewing machine of the present invention; 
       FIG. 4  is a sectional view taken along line  4 — 4  of  FIG. 3 ; 
       FIG. 5  is a sectional view taken along line  5 — 5  of  FIG. 3 , showing that the phase of the take-up cam has not yet been adjusted and also showing the left end face of the rotary shaft; 
       FIG. 6  is a right view according to  FIG. 3 , showing that the phase of the take-up cam has not yet been adjusted and also showing the right end face of the rotary shaft; 
       FIG. 7  is a sectional view according to  FIG. 5 , showing that the phase of the take-up cam has been adjusted and also showing the left end face of the rotary shaft; and 
       FIG. 8  is a sectional view according to  FIG. 6 , showing that the phase of the take-up cam has been adjusted and also showing the right end face of the rotary shaft. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIGS. 1  to  4 . The present invention provides a take-up cam phase adjustment structure of looper thread take-up apparatus of a sewing machine. The sewing machine includes a housing  1  having a machine bed  11 , a column  12  and an arm  13 . A lower driving shaft  3  is disposed in the machine bed  11 . One end of the lower driving shaft  3  is connected with a lower knotting hook  31 . The column  12  is erectly disposed on a first side of the machine bed  11 . One end of the arm  13  is connected with upper end of the column  12 . The arm  13  suspensively extends from the column  12  to upper side of the second side of the machine bed  11 . 
   Referring to  FIGS. 1 ,  2  and  3 , the looper thread take-up apparatus  2  of the sewing machine includes a rotary shaft  21  pivotally mounted in the machine bed  11  of the sewing machine. A first end  211  of the rotary shaft  21  outward protrudes from a first sidewall  1   a  of the housing  1 . The looper thread take-up apparatus  2  further includes a take-up cam  23  tightly fixed on a second end  212  of the rotary shaft  21 . The looper thread take-up apparatus  2  further includes a thread-guiding plate  24  mounted on the housing  1  for correspondingly pressing the stitching thread against the rim of the take-up cam  23 . The looper thread take-up apparatus  2  further includes a transmission mechanism  4  connected between the lower driving shaft  3  and the rotary shaft  21 . The transmission mechanism  4  includes a driven wheel  41  fitted on the first end  211  of the rotary shaft  21  and tightly locked on the rotary shaft  21  by a second locking member  221  (such as a screw). The transmission mechanism  4  further includes a transmission wheel  42  coupled with the lower driving shaft  3  of the sewing machine and a positive drive belt  43  engaged between the driven wheel  41  and the transmission wheel  42  for drivingly rotating the rotary shaft  21 . The transmission mechanism  4  is not limited to the above type. 
   The take-up cam phase adjustment structure of the looper thread take-up apparatus of the sewing machine is characterized in that the take-up cam phase adjustment structure includes: a first locking member  321  (such as a screw) for locking the transmission wheel  42  on the lower driving shaft  3 ; a second locking member  221  (such as a screw) for locking the driven wheel  41  on the rotary shaft  21 ; and a turning section  25  disposed at any end of the rotary shaft  21  (or both ends of the rotary shaft  21 ). After an operator unscrews and loosens the first locking member  321  for locking the transmission wheel  42  on the lower driving shaft  3  or unscrews and loosens the second locking member  221  for locking the driven wheel  41  on the rotary shaft  21 , by means of rotating the turning section  25 , the relative positions between the take-up cam  23  and the lower driving shaft  3  can be drivingly adjusted to meet different requirements of sewing operation. 
   One end of the lower driving shaft  3  or the first end of the rotary shaft  21  outward protrudes from the first sidewall  1   a  of the housing  1 . Alternatively, both the end of the lower driving shaft  3  and the first end of the rotary shaft  21  outward protrude from the first sidewall  1   a  of the housing  1 . 
   Referring to  FIGS. 6 and 8 , the tuning section  25  can be a flat groove, cross groove or otherwise shaped groove, whereby a user can turn the rotary shaft  21  with a screwdriver or manually. Alternatively, the turning section  25  can be a protruding plate for a user to manually turn the rotary shaft  21 . This is not limited. 
   Referring to  FIGS. 2 and 6 , when adjusting the phase of the take-up cam  23 , the second locking member  221  for locking the driven wheel  41  on the rotary shaft  21  or the first locking member  321  for locking the transmission wheel  42  on the lower driving shaft  3  can be directly unscrewed and loosened from outer side of the housing  1  of the sewing machine. Thereafter, the operator can fit a tool (such as a screwdriver) with the turning section  25  at one end of the rotary shaft  21  to turn the same. Accordingly, the rotary shaft  21  is freely rotated within the shaft hole of the driven wheel  41 . At the same time, the take-up cam  23  is rotated along with the rotary shaft  21  so that the phase of the take-up cam  23  is adjusted.  FIGS. 7 and 8  show the take-up cam after adjusted. The driven wheel  41  is not drivingly rotated so that the lower driving shaft  3  and the lower knotting hook  31  are not driven. Therefore, the operator can easily turn and adjust the take-up cam  23  to a predetermined phase. After adjusted, the operator only needs to screw and tighten the second locking member  221  for locking the driven wheel  41  on the rotary shaft  21 . At this time, the adjustment of the phase of the take-up cam is completed. 
   According to the above arrangement, the operator can directly adjust the phase of the take-up cam from outer side of the housing of the sewing machine without disassembling the housing. Therefore, the adjustment of the phase of the take-up cam is facilitated and speeded. 
   The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.