Patent Publication Number: US-7717050-B2

Title: Presser foot drive structure for embroidery machine

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to embroidery machine, and more particularly, to a presser foot drive structure for embroidery machine. 
   2. Description of the Related Art 
   As well known in the art, an industrial embroidery machine is a type of machine in which an embroidery frame fixing a sheet of fabric moves horizontally in x- and y-axial directions in order to embroider a desired pattern on the fabric, while a needle bar capable of sewing moves up and down. A sewing machine carries a sheet of fabric using a geared carriage to sew the fabric sheet. In contrast, the embroidery machine performs needlework while the embroidery frame, fixing the sheet of fabric, is carried in x- and y-axial directions. Accordingly, the precise and constant-speed movement of the embroidery frame has a close relationship with the quality of an embroidered pattern. 
   Thus, as a source of power for driving the needle bar of the embroidery machine in a vertical direction, a servo motor, an induction motor, the speed of which can be controlled, or the like is used. As a power source for carrying the embroidery frame in x- and y-axial directions, a stepping motor, which ensures good positioning and is easy to control, is typically used. 
   Generally, 12 to 24 sewing machines are connected with each other along one spindle in order to improve the productivity of embroidery machine. Since the sheet of fabric must be sewn with various colors of thread corresponding to an embroidery design, each sewing machine has 6 to 12 needle bars, which are equipped with different colors of thread. 
   These days, users are demanding the ability to easily input, copy and store embroidery designs while performing simple editing on the designs. The users are also demanding various functions, such as an automatic thread color change function, which is enabled according to an embroidery design, a trimming function of automatically cutting a thread when sewing is finished, a function of interrupting the operation of the machine and raising an alarm when a thread is inadvertently cut, an outage restoration function of restarting the embroidery machine when the sewing machine stops due to a power failure, and the like. 
   In addition to the above-mentioned attempts to improve embroidery quality, embroidery machine providers are adopting industrial computers or microcomputers to embroidery machines in order to meet user demands for multi-functional embroidery machine operation. 
     FIG. 1  is a perspective and partially expanded view illustrating an embroidery machine of the prior art,  FIG. 2A  is a perspective view illustrating a presser foot drive structure of the embroidery machine of the prior art, and  FIG. 2B  is an expanded view of part “A” of  FIG. 2A . As shown in  FIG. 1 , a plurality of sewing heads is arranged in the front portion of a sewing machine  1 , along the length thereof. In the front portion of a sewing arm  3  of each sewing head, there is provided a needle bar support case  4 , which has a plurality of presser feet  5  acting as cloth pressing members. 
   The presser foot  5  serves to prevent a sheet of cloth to be sewn from coming loose when it is being sewn, and is provided so as to be vertically movable in cooperation with a needle bar (see the reference number  6  in  FIG. 2A ). 
   As shown in  FIGS. 2A and 2B , the needle bar  6  acts as a guide shaft for the vertical movement of the presser foot  5 . Presser foot supports  12  and  13  for mounting the presser foot  5  on the needle bar  6  in a vertically and reciprocally movable fashion are located in two places on the presser foot  5 , such as the top end and the middle section of the presser foot  5 , so that a needle bar holder  14  at the bottom end of the needle bar  6  does not pass through the middle section of the presser foot  5 . This acts as a factor limiting the reduction of the stroke of the presser foot  5 , that is, the distance between the upper dead point and the lower dead point of the presser foot  5 . 
   The needle bar  6 , which should always have a predetermined stroke length, vertically moves through the middle section of the presser foot  5 . In the vertical movement of the presser foot  5 , in order to avoid excessive interference with the needle bar holder  14 , the stroke of the presser foot  5  should have a predetermined length that is determined according to the stroke of the needle bar  6 . 
   When the presser foot  5  is located at the lower dead point  5 , a predetermined gap is always maintained between a pressing portion, which presses the sheet of cloth to be sewn, and the middle section, which is slidably supported on the needle bar. Thus, in the presser foot  5  pressing portion, where the sheet of cloth to be sewn is pressed, supporting force for the needle bar  6  is unreliable. Since the needle bar  6  is assembled through the presser foot  5 , it is complicated to replace the presser foot  5  when it is fractured or broken. It is also necessary to disassemble the needle bar  6  and reset the upper and lower dead points of the needle bar. 
   SUMMARY OF THE INVENTION 
   The present invention has been made to solve the foregoing problems with the prior art, and therefore the present invention provides a presser foot drive structure of an embroidery machine, in which the stroke of a presser foot can be set to be smaller than that of a needle bar. 
   The present invention also provides a presser foot drive structure of an embroidery machine, in which the force supporting a needle bar is enhanced while the shaking of a presser foot is reduced. 
   The present invention further provides a presser foot drive structure of an embroidery machine, which can facilitate the replacement of a presser foot and eliminates inconveniences, such as the requirement to disassemble a needle bar or reset the upper and lower dead points when replacing the presser foot. 
   According to an aspect of the present invention, there is provided a presser foot drive structure of an embroidery machine, by which a vertically movable presser foot for preventing a sheet of cloth to be sewn from rising in a sewing operation is vertically moved inside a sewing head. The presser foot drive structure includes a presser foot drive holder, which is vertically slidably mounted on the outer circumference of a vertically driven needle bar; a presser foot drive shaft, which is disposed parallel to the needle bar and mounted on the presser foot drive holder; and the presser foot, which is disposed at the lower end of the presser foot drive shaft and vertically reciprocates. 
   According to an embodiment of the present invention, the presser foot drive structure may further include a presser foot drive block, which is engaged with the presser foot drive holder, and a presser foot drive lever for driving the presser foot drive block. 
   According to another embodiment of the present invention, the presser foot may be detachably assembled to the lower end of the presser foot drive shaft. 
   According to a further embodiment of the present invention, the presser foot drive block may include a body, having a C-shaped cross section, and a connecting member, stored inside the body and having an engaging recess in one side thereof. 
   According to another embodiment of the present invention, the presser foot drive structure may further include a guide holder, which slides vertically and holds and supports the presser foot drive shaft. 
   According to yet another embodiment of the present invention, the guide holder may include an upper guide holder, fastened to the presser foot driving holder, and a lower guide holder, disposed at the distal end of the needle bar. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a perspective and partially expanded view illustrating an embroidery machine; 
       FIG. 2A  is a perspective view illustrating a presser foot drive structure of the embroidery machine of the prior art; 
       FIG. 2B  is an expanded view of part “A” of  FIG. 2A ; 
       FIG. 3  is a perspective view illustrating the installed state of a presser foot drive structure of an embroidery machine according to an embodiment of the present invention; 
       FIG. 4  is a side elevation view illustrating the presser foot drive structure of the present invention; 
       FIG. 5A  is a perspective view illustrating the partially installed state of the present invention; and 
       FIG. 5B  is an expanded view of part “B” of  FIG. 5A . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter a presser foot drive structure of an embroidery machine according to an embodiment of the present invention will be described more fully with reference to the accompanying drawings. 
     FIG. 3  is a perspective view illustrating the installed state of a presser foot drive structure of an embroidery machine according to an embodiment of the present invention,  FIG. 4  is a side elevation view illustrating the presser foot drive structure of the present invention,  FIG. 5A  is a perspective view illustrating the partially installed state of the present invention, and  FIG. 5B  is an expanded view of part “B” of  FIG. 5A . 
   Referring to  FIGS. 3 to 5A , the presser foot drive structure of the embroidery machine of the present invention generally includes a presser foot drive holder  27 , a presser foot drive shaft  30  arranged parallel to a needle bar  34  via the presser foot drive holder  27 , a presser foot  25 , which is disposed at the lower end of the presser foot drive shaft  30  and is vertically movable, and guide holders  28  and  29  disposed at lower portions of the needle bar  34 , so that the lower portions of the needle bar  34  are inserted into and supported by the guide holders  28  and  29  in a vertically slidable fashion. 
   As shown in  FIGS. 4 ,  5 A and  5 B, the presser foot drive holder  27  has a stepped profile when seen from the side, and is vertically slidable and mounted on the outer circumference of the needle bar  34 , which vertically extends through the inner circumference thereof. The presser foot holder  27  is also provided with an engaging protrusion  27   a , which protrudes a predetermined length and is inserted into and supported by an engaging recess, which will be described later. 
   The upper guide holder  28 , as shown in  FIGS. 4 ,  5 A and  5 B, has an L-shaped cross section when seen from the side. The upper guide holder  28  is in close contact with the presser foot drive holder  27 , and the needle bar  34  extends through the inner circumference of the upper guide holder  28 . The presser foot drive shaft  30  is fixed, at the top portion thereof, to the underside of the upper guide holder  28 , and is arranged parallel to the needle bar  34 . 
   As shown in  FIGS. 4 ,  5 A and  5 B, the lower guide holder  29  has a diagonally mirrored L-shaped cross section. The lower end (distal end) of the needle bar  34  is inserted into the lower guide holder  29  to a predetermined depth, and the presser foot drive shaft  30  extends through the lower guide holder  29 . Accordingly, the upper and lower guide holders  28  and  29  are detachably attached to the needle bar  34  and the presser foot drive holder  27 . The upper and lower guide holders  28  and  29  support the presser foot drive shaft  30  such that the presser foot drive shaft  30  is vertically slidable. 
   As shown in  FIGS. 4 ,  5 A and  5 B, the presser foot  25  is fastened at the top end thereof to the lower end of the presser foot drive shaft  30 , and thus vertically reciprocates together with the needle bar  34 . 
   The presser foot drive structure also includes a presser foot drive block  26 , as shown in  FIGS. 4 ,  5 A and  5 B. The presser foot drive block  26  includes a body  26   a , which has a C-shaped cross section when seen from the side, and a connecting member  26   b , which has a substantially T-shaped cross section and is stored inside the body  26   a . An engaging recess  26   b - 1  having a C-shaped cross section protrudes from one side of the connecting member  26   b , so that the engaging protrusion  27   a  of the pressure foot drive holder  27  is inserted thereinto. The needle bar drive shaft  24  vertically extends through the body  26   a  and the connecting member  26   b  of the presser foot drive block  26 . 
   A connecting link  42  is fixedly attached at one end thereof to the body  26   a  of the presser foot drive block  26 , and is pivotally connected at the opposite end thereof to one end of a presser foot drive lever  41 . The presser foot drive lever  41  is connected at the opposite end thereof to a presser foot drive rod  40 . Reference numeral  25   a , which has not yet been described, indicates a needle hole, which a needle passes through. 
   Now, the operation of the present invention having the above-mentioned construction will be described. 
   As shown in  FIGS. 3 to 5B , when a spindle  20  is rotated by the driving force of a motor (not shown), the presser foot drive rod  40  rotates around the spindle  20  and, concurrently, the presser foot drive block  26 , which is connected to the presser foot drive lever  41  via the connecting link  42 , is vertically and reciprocally moved. 
   Concurrently, the needle bar  34 , which is connected to the presser foot drive holder  27 , which is engaged with the presser foot drive block  26 , moves vertically inside a sewing heads  22 , and the presser foot  25 , which is coupled to the lower end of the presser foot drive shaft  30 , which is placed parallel to the needle bar  34 , also moves vertically. 
   As mentioned above, the presser foot  25  moves vertically using the presser foot drive holder  27  and the presser foot drive shaft  30 , independent of the vertical movement of the needle bar  34 . Unlike a conventional structure, in which the needle bar  34  extends through the presser foot  25 , the drive structure of the present invention uses the needle bar  34  as a guide shaft for the vertical movement of the presser foot  25  while allowing the needle bar  34  to vertically move parallel to the presser foot  25 , so that the stroke of the presser foot  25  can be set to be small, independently of the stroke of the needle bar  34 . 
   In addition, since the lower guide holder  29  is coupled with the presser foot  25  at the distal end of the needle bar  34 , it is possible to enhance the supporting force for the needle bar  34 , particularly at a portion where the presser foot  25  is provided, to which the largest external force is applied owing to interference with a sewing material such as a sheet of cloth to be sewn, and also to minimize the shaking of the presser foot  25  using the lower guide holder  29 . 
   Furthermore, since the presser foot  25  is detachably assembled to the presser foot drive shaft  30 , when the presser foot  25  is damaged or broken, the presser foot  25  can be easily replaced by detaching it from the lower end of the presser foot drive shaft  30 . Moreover, it is also possible to eliminate inconveniences, such as the requirement to disassemble the needle bar  34  or reset the upper and lower dead points in the event of replacement of the presser foot  25 . 
   According to the present invention, as set forth above, the presser foot drive structure is operated independently from the structure for vertically lifting and lowering the needle bar, so that the reduced stroke of the presser foot can decrease noises and vibration in the sewing head. 
   In addition, the optimum stroke of the presser foot, which can minimize noises and vibration in the sewing head, can be easily realized. 
   The presser foot drive holder and the guide holder, disposed at the distal end of the needle bar, can enhance the supporting force for the needle bar, particularly at a portion where the presser foot is provided, and can also reduce the shaking of the presser foot. 
   Furthermore, since the presser foot has a detachable configuration, it is easy to replace the presser foot, and it is unnecessary to disassemble the needle bar or reset the upper and lower dead points. 
   Although the presser foot drive structure of an embroidery machine of the present invention has been described with reference to the drawings, the present invention is not intended to be limited by the above illustrated embodiment and drawings. Rather, it should be understood that those skilled in the art can make various modifications and variations without departing from the scope of the present invention as defined in the accompanying claims.