Patent Publication Number: US-6712015-B1

Title: Oblique thread-guiding link of a sewing machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to an oblique thread-guiding link of a sewing machine, in which the swing arm is obliquely mounted in the sewing machine. 
     2. Description of the Prior Art 
     FIGS. 1 and 2 show a conventional sewing machine. A swing arm  91  is pivotally mounted in the sewing machine. The center of the swing arm  91  has a sleeve  911  having a shaft hole  912 . A pivot shaft  92  is axially fitted through the shaft hole  912 . Two ends of the pivot shaft  92  are perpendicularly pivotally mounted between two sidewalls  93   a ,  93   b  of the sewing machine. A front swing arm  91   a  forward radially projects from a first side of the sleeve  911 . A rear swing arm  91   b  rearward radially projects from a second side of the sleeve  911 . The front swing arm  91   a  is positioned above a needle holder mechanism  94  and aligned and coupled therewith. The rear end of the rear swing arm  91   b  is positioned above a driving mechanism  95  and coupled therewith. When the driving mechanism  95  up and down drives the rear swing arm  91   b , the front swing arm  91   a  is swung along with the rear swing arm  91   b  to drive the needle holder mechanism  94  to move up and down. At the same time, a thread guiding rod  96  mounted on outer side of the pivot shaft  92  is driven and swung to guide the stitch thread into the needle holder mechanism  94 . 
     Referring to FIGS. 1 and 2, the front and rear swing arms  91   a ,  91   b  of the swing arm  91  are respectively positioned on left and right sides of the sleeve  911 . Therefore, the central axis  9   a  of the front swing arm  91   a  does not coincide with the central axis  9   b  of the rear swing arm  91   b . Instead, the axis  9   a  is spaced from the axis  91   b  by a distance D. Therefore, when the driving mechanism  95  drives the swing arm  91  to swing up and down about the pivot shaft  92 , the action force F will create a bending moment M onto the swing arm  91 . As a result, when the swing arm  91  quickly up and down swing, the swing arm  91  is vibrated to emit a noise. This tends to speed the wearing the pivot shaft. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide an oblique thread-guiding link of a sewing machine, including a swing arm having a front section defined as a front swing arm and a rear section defined as a rear swing arm. The center of the swing arm is formed with a shaft hole in which a pivot shaft is tightly fitted. Two ends of the pivot shaft are obliquely pivotally mounted in two opposite sidewalls of the housing of the sewing machine. One end of the pivot shaft protrudes from the housing of the sewing machine. The front end of the front swing arm is positioned above a needle holder mechanism and aligned and coupled therewith. The rear end of the rear swing arm is positioned above a driving mechanism and aligned and coupled therewith. One end of a thread-guiding fixing seat is fixedly connected with the protruding end of the pivot shaft and is driven by the swing arm to swing. A thread-guiding bar is fixed at the second end of the thread-guiding fixing seat and formed with multiple thread-guiding eyelets. 
     It is a further object of the present invention to provide the above oblique thread-guiding link of the sewing machine, in which the front and rear ends of the swing arm are straightly projectively positioned above the needle holder mechanism and the driving mechanism to correspondingly couple therewith. The application force point and the resistance force point are positioned on the same straight line so as to eliminate the vibration and noise produced when the swing arm swings. 
     It is still a further object of the present invention to provide the above oblique thread-guiding link of the sewing machine, in which two collars are respectively fitted on two ends of the pivot shaft. The bodies of the collars are inlaid in the sidewalls of the sewing machine. One end of the body of each collar is formed with a flange for abutting against inner side of the sidewall of the sewing machine. Accordingly, the pivot shaft can stably swing in a predetermined position without axially sliding. 
     The present invention can be best understood through the following description and accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a view of the structure of a conventional sewing machine; 
     FIG. 2 is a view showing the operation of the swing arm of the conventional sewing machine; 
     FIG. 3 is a perspective exploded view of the present invention; 
     FIG. 4 is a top view showing the structure of the present invention; and 
     FIG. 5 is a perspective exploded view of the driving mechanism of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIGS. 3 to  5 . The oblique thread-guiding link of the sewing machine of the present invention includes: a swing arm  1 ; a pivot shaft  2  snugly tightly fitted in the swing arm  1 , two ends  2   a ,  2   b  of the pivot shaft  2  being obliquely pivotally mounted between two opposite sidewalls  71   a,    71   b  of the sewing machine  7 ; a needle holder mechanism  3  drivingly coupled with front end of the swing arm  1 ; a driving mechanism  4  coupled with rear end of the swing arm  1 ; a thread-guiding fixing seat  5  fixedly connected with one end  2   a  of the pivot shaft  2 , the thread-guiding fixing seat  5  being drivable by the pivot shaft  2  to swing; and a thread-guiding bar  6 , a first section  61  of the thread-guiding bar  6  being tightly fixed on the thread-guiding fixing seat  5 , a second section  62  of the thread-guiding bar  6  being formed with multiple thread-guiding eyelets  621  for guiding the thread into the needle holder mechanism  3 . The front and rear ends of the swing arm  1  are straightly projectively positioned above the needle holder mechanism  3  and the driving mechanism  4  and correspondingly coupled therewith. The application force point and the resistance force point are positioned on the same straight line so as to eliminate the vibration and noise produced when the swing arm  1  swings. 
     Referring to FIGS. 3 and 4, the swing arm  1  of the present invention is integrally formed. The swing arm  1  has a sleeve section  11  formed with a central axial shaft hole  10 . The pivot shaft  2  is snugly fitted in the shaft hole  10 . A front swing arm  12  forward radially projects from the middle of outer circumference of the sleeve section  11 . In addition, a rear swing arm  13  rearward radially projects from the middle of outer circumference of the sleeve section  11 . The central axis  120  of the front swing arm  12  coincides with the central axis  130  of the rear swing arm  13 . The front end of the front swing arm  12  is positioned above a needle holder mechanism  3  and aligned and coupled therewith. The rear end of the rear swing arm  13  is positioned above a driving mechanism  4  and aligned and coupled therewith. 
     Two ends  2   a ,  2   b  of the pivot shaft  2  are obliquely pivotally mounted in two shaft seats  72  of two opposite sidewalls  71   a ,  71   b  of the sewing machine  7 . One end  2   a  of the pivot shaft  2  protrudes from one sidewall  71   a  of the sewing machine  7  for connecting with the thread-guiding fixing seat  5 . 
     Two retainer rings  22  are locked on the pivot shaft  2  on two sides of the swing arm  1 . Two axial thrust bearings  23  are fitted on the pivot shaft  2  between the outer sides of the retainer rings  22  and the shaft seats  72  of the sewing machine  7 , whereby the swing arm  1  can more smoothly swing. 
     The needle holder mechanism  3  includes a coupling member  31  having a first coupling section  311  coupled with the front end of the front swing arm  12  of the swing arm  1 . The needle holder mechanism  3  further includes a link seat  32  pivotally connected with a second coupling section  312  of the coupling member  31 . The link seat  32  is formed with a fitting through hole  321 . The needle holder mechanism  3  further includes a connecting rod  33  fitted in the fitting hole  321  of the link seat  32 . The needle holder mechanism  3  further includes a needle holder  34  tightly fixed at bottom end of the connecting rod  33 . Multiple needles  341  are locked on the needle holder  34 . 
     Referring to FIGS. 3 and 5, the driving mechanism  4  includes a ball joint  41  connected with rear end of the rear swing arm  13  and a link  42 . The spherical head section  411  of the ball joint  41  is snugly fitted in a first end of the link  42 . A second end of the link  42  stably rides on a transmission cam  43 . When the transmission cam  43  is driven and rotated by a motor (not shown), the link  42  is moved up and down to drive the swing arm  1  to swing up and down. 
     A first end of the thread-guiding fixing seat  5  is tightly fixedly connected with a section of the pivot shaft  2  protruding from the housing of the sewing machine. A second end  52  of the thread-guiding fixing seat  5  is driven by the pivot shaft  2  to swing up and down. The end face of the second end of the thread-guiding fixing seat  5  is formed with a connecting face  521 . The connecting face  521  and a line normal to the axis  20  of the pivot shaft  2  contain an angle A1. The axis  20  of the pivot shaft  2  and a horizontal line  70  normal to the sidewalls  71   a ,  71   b  of the sewing machine  7  contain an angle A2. The angle A1 is equal to the angle A2. That is, when the first end  51  of the thread-guiding fixing seat  5  is fixedly mounted on the pivot shaft  2 , the connecting face  521  is parallel to the sidewall  71   a  of the sewing machine. 
     The first section  61  of the thread-guiding bar  6  is fixed on the connecting face  521  of the second end of the thread-guiding fixing seat  5 , whereby the thread-guiding bar  6  can be up and down swung along with the thread-guiding fixing seat  5 . The second section  62  of the thread-guiding bar  6  is formed with multiple thread-guiding eyelets  621  for guiding multiple threads into the needle holder mechanism  3 . 
     The needle holder mechanism  3  and the driving mechanism  5  pertain to prior art and are not included in the scope of the present invention. The present invention is characterized in that the pivot shaft  2  fitted in the swing arm  1  is obliquely pivotally mounted between the two opposite sidewalls of the sewing machine  7 . The central axes  120 ,  130  of the front and rear swing arms  12 ,  13  coincide with each other. The front end of the front swing arm  12  is positioned above a needle holder mechanism  3  and aligned and coupled therewith. The rear end of the rear swing arm  13  is positioned above a driving mechanism  4  and coupled therewith. By means of the obliquely arranged swing arm, the problems of vibration and noise produced when the conventional sewing machine operates by reason that the axes of the front and rear swing arms do not coincide with each other can be eliminated. 
     In addition, two collars  8  are respectively fitted on two ends of the pivot shaft  2 . The bodies  81  of the collars  8  are inlaid in the sidewalls  71   a ,  71   b  of the sewing machine  7 . One end of the body  81  of each collar  8  is formed with a flange  82  for abutting against inner side of the sidewall  71   a ,  71   b  of the sewing machine  7 . Accordingly, the pivot shaft  2  can stably swing in a predetermined position without axially sliding. 
     The oblique thread-guiding link of the sewing machine of the present invention has the following advantages: 
     1. The front and rear ends of the swing arm  1  are straightly projectively positioned above the needle holder mechanism  3  and the driving mechanism  4  to correspondingly couple therewith. The application force point and the resistance force point are positioned on the same straight line so as to eliminate the vibration and noise produced when the swing arm  1  swings. 
     2. Two collars  8  are respectively fitted on two ends of the pivot shaft  2 . The bodies  81  of the collars  8  are inlaid in the sidewalls  71   a ,  71   b  of the sewing machine  7 . One end of the body  81  of each collar  8  is formed with a flange  82  for abutting against inner side of the sidewall  71   a ,  71   b  of the sewing machine  7 . Accordingly, the pivot shaft  2  can stably swing in a predetermined position without axially sliding. 
     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.