Patent Publication Number: US-6708632-B2

Title: Fabric tensioning device for sewing machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fabric tensioning device for stretching work fabric in the sewing location of a sewing machine. 
     2. Description of Related Art 
     Devices for tensioning a piece of tube-like fabric, such as material for socks and wrist bands, using a cylindrical frame are used in embroidering on a sewing machine. One of such a fabric tensioning devices is disclosed in International Patent Publication Number WO00/53836. This device has a cylindrical frame  101  which is placed to cover the outside of the cylinder bed (not shown) of the sewing machine as shown in FIG.  11 . The cylindrical frame  101  includes a sewing window  102  for exposing the sewing area of the cylinder bed, a core material clamping member  105  for clamping down thick core material C against the cylindrical frame  101 , and a fabric clamping member  103  for clamping down the fabric and the core material C against the cylindrical frame  101 . The fabric is arranged to cover the core material C which is arranged to cover the sewing window  102 . The core material clamping member  105  is formed in a rectangular shape with a closed front end so that the core material C can be clamped in one stroke. The core material clamping member  105  is attached to the cylindrical frame  101  to be able to open and close vertically. 
     However, with this fabric tensioning device, the core material clamping member  105  clamps down the core material C from the rear to the front simultaneously on both the left and right side of cylindrical frame  101 . Therefore, the cylindrical shape of the core material C tends to be lower on the rear side or cause a localized deformation, thereby essentially making it difficult to properly fit the entire core material C around the circumference of cylindrical frame  101 . Thus, the core material C is difficult to set since it is necessary to straighten or restretch the stretched core material C. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fabric tensioning device for a sewing machine that can solve the abovementioned problem by holding down the core material on the left side and the right side individually so that it can be easily stretched in a properly aligned manner on the outer periphery of the cylindrical frame. 
     In order to solve the abovementioned problem, the fabric tensioning device according to the present invention comprises a cylindrical frame having a sewing window, a core material clamping member for clamping down a core material against the cylindrical frame and a fabric clamping member for clamping down the fabric and the core material against the cylindrical frame. The core material covers the sewing window, and the fabric covers the core material. The fabric clamping member is able to open or close against the cylindrical frame. The core material clamping member consists of two members provided with one on each side of the left and right sides of the cylindrical frame. The two members extend in the axial (front and rear) direction and can open or close against the cylindrical frame independently. 
     The core material clamping members can open or close in either a vertical direction or a lateral direction. However, the two core material clamping members can be mounted on the left and right sides of the cylindrical frame at the rear ends of the two clamping members respectively. Therefore, the two core material clamping members can open or close their respective front end in the lateral direction in order to make it easier to stretch the core material at the same height on the front and rear against the cylindrical frame. Furthermore, tighteners can be provided protrusively on the outer surface of the cylindrical frame extending along the left and right edges of the sewing window in order to prevent the core material from slackening or deforming. A core material clamping member can be provided under each tightener. 
     The core material clamping member does not have a specific shape requirement. The core material clamping member can be made of a long rod or a strip extending in the axial (front and rear) direction. Several clamps along the axial direction can be provided on the inside of the core material clamping member so that the oblong core material clamping member can press down various parts of the core material. Additionally, a temporary latch can engage the cylindrical frame at the front end of the core material clamping member in order to hold the shape of the core material until the work fabric is stretched. 
     The fabric clamping material does not have a specific constitution requirement. The fabric clamping material can have two fabric clamps, one on each side of the left and right sides of the fabric clamping member, and a band that tightens the fabric clamping member and the core material clamping members together against the cylindrical frame. The two fabric clamps can face the core material clamping member from the outside. Slip guards made of processed fabric can be provided on the outer surface of the core material clamping members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a cylinder bed according to an embodiment of the present invention. 
     FIG. 2 is a front view of the bed according to an embodiment of the present invention. 
     FIG. 3 is a disassembled perspective view showing a cylindrical frame guide device provided on the bed according to an embodiment of the present invention. 
     FIG. 4 is a perspective view of a fabric tensioning device of the bed according to an embodiment of the present invention. 
     FIG. 5 is a side view of the fabric tensioning device according to an embodiment of the present invention. 
     FIG. 6 is a partially broken front view of the fabric tensioning device according to an embodiment of the present invention. 
     FIG. 7 is a plan view of the fabric tensioning device according to an embodiment of the present invention. 
     FIG. 8 is a cross-sectional view showing how an core material and a work fabric are mounted on the fabric tensioning device according to an embodiment of the present invention. 
     FIG. 9 is a plan view showing how the core material and the work fabric are tensioned according to an embodiment of the present invention. 
     FIG. 10 is a cross-sectional view showing how the core material and the work fabric are tensioned according to an embodiment of the present invention. 
     FIG. 11 is a perspective view of a fabric tensioning device of the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention on an embroidering sewing machine will be described below with reference to the accompanying drawings. A head  1  and a cylinder bed  2  are displaced in the vertical direction in the machine frame (not shown) of a sewing machine as shown in FIGS. 1-2. A needle  3  is attached to the bottom end of the head  1  while a bobbin case  4  and a needle plate  11  are provided at the front end of the cylinder bed  2 . A Y-direction moving body  5  is supported by the top surface of the cylinder bed  2 , and a base plate  6  is connected vertically to the moving body  5 . Three rollers  8  are displaced on the front side of the base plate  6  in order to support a drive ring  7  while two guide rollers  10  are provided on the back side of the base plate  6  and engage two bottom grooves  9  on the left and right sides of the cylinder bed  2 . 
     A X-direction moving body  13  is supported via a rail  12  provided on the top of the Y-direction moving body  5  while a pulley  14  is provided at the left and right ends of moving body  13  respectively. A wire rope  15  is provided on the pulleys  14  and is tightly stretched by means of a spring  16  while the rope  15  is wrapped around the middle of the drive ring  7 . The Y-direction moving body  5  and the X-direction moving body  13  are connected to a sewing frame driving device (not shown) of the sewing machine, and the Y-direction moving body  5  strokes the drive ring  7  in a reciprocating manner in the axial direction (front and rear direction) of the cylinder bed  2  via the base plate  6  while the X-direction moving body  13  rotates the drive ring  7  in a reciprocating manner around the axis of the cylinder head  2  via the wire rope  15 . 
     A cylindrical frame  19  of the fabric tensioning device  18  is placed to cover the outside of the cylinder bed  2  in an embroidering process of a piece of tube-like fabric such as material for socks and wrist bands. The cylindrical frame  19  is attached to the drive ring  7  via the rear end of the mounting part  19   a . A latching piece  20  and a flange  21  are provided protrusively on the rear outer periphery of the cylindrical frame  19  while a lever  22  that engages with the latching piece  20  and a spring  23  that elastically contacts with flange  21  are provided on the drive ring  7 . Thus, the cylindrical frame  19  is connected tightly to the drive ring  7  via the lever  22  and the spring  23 . The cylindrical frame  19  and the drive ring  7  are driven together in the axial and circumferential directions relative to the axis of the cylinder bed  2  in order to sew the fabric stretched around the cylindrical frame  19  in the cooperation of the needle  3  and the bobbin case  4 . 
     A pair of arms  25  protrude on the left and right sides of the front end of the cylinder bed  2 , and a needle plate  11  is affixed horizontally on arms  25  as shown in FIG.  3 . Curved surfaces  11   a  are formed on the left and right shoulder areas of the needle plate  11  close to the inner surface of the cylindrical frame  19 . A boss  26  equipped with a needle hole  26   a  protrudes low in the center flat area of needle plate  11 . The front end of a bobbin case drive shaft  31  extends into an opening  29  formed below the needle plate  11 , and the bobbin case  4  is mounted on the bobbin case drive shaft  31 . 
     A guide member  27  is provided in opening  29  for supporting the cylindrical frame  19  from the inside. The guide member  27  consists of a connecting part  27   a  in the rear end and two side wall parts  27   b  on the left and right sides, together forming a rectangular shape. The connecting part  27   a  is affixed detachably with a screw  32  to the front end surface of the cylinder bed  2  below the bobbin case drive shaft  31 . The side walls  27   b  cover the outside of the arms  25 . A curved plate  33  is affixed by welding or the like on the outside of each side wall part  27   b , and the curved plates  33  form a partial cylindrical surface  30  that contacts concentrically with the inside of the cylindrical frame  19  for the side wall parts  27   b.    
     A protection cover  28  is provided below the guide member  27 , and the cover  28  covers the bobbin case  4  from its underside. The protection cover  28  consists of flat parts  28   a  and a curved part  28   b  forming a U-shape as it is viewed from the front, wherein the curved part  28   b  forms a partial cylindrical surface  36  having the same curvature as the partial cylindrical surface  30  of the guide member  27  for the cover  28 . Semispherical protrusions  34  are provided on the flat parts  28   a  while holes  35  are provided on the side walls  27   a  to fit the protrusions  34 . The protection cover  28  is mounted detachably on the guide member  27  by means of fitting between the protrusions  34  and the holes  35  as the flat parts  28   a  are inserted on the inside of the side wall parts  27   b.    
     The cylindrical frame  19  comprises a sewing window  37  that exposes the needle plate  11 , a core material clamping member  38  that clamps down the core material C covering the sewing window  37  against the cylindrical frame  19 , a fabric clamping member  39  that clamps down the work fabric W covering the core material C together with the core material C against cylindrical frame  19 , and a support member  40  that supports the core material C and the work fabric W in the middle position of sewing window  37 , as shown in FIGS. 4-7. The core material C is a shape-keeping material that prevents the work fabric W from sinking and is made of a material such as cardboard, unwoven fabric, etc. It is possible to sew by stretching the work fabric W directly over the cylindrical frame  19  without using the core material C if the work fabric W consists of a rigid material such as leather, felt, etc. 
     The sewing window  37  has a length corresponding to the axial stroke length of the cylindrical frame  19  while a slip guard  42  made of rubber is glued on the cylindrical frame  19  along the respective front and rear edges of the sewing window  37 . A tightener  43  made of a steel strip or rubber is protrusively provided along the left and right side edges of the sewing window  37 . A support member  40  is formed into a curved shape having a curvature approximately equal to that of the outside diameter of the cylindrical frame  19  and is fastened at fastening areas  40   a  at each end with screws  44  that are screwed into screw holes  43   a  of the tighteners  43  in an axially adjustable manner spanning over the sewing window  37 . A notch  45  is formed on the rear mounting part  19   a  of the cylindrical frame  19  to allow the spring  23  of the drive ring  7  to enter. The inside of the front end of the cylindrical frame  19  is attached with an annular plate  46 , and a portion of the annular plate  46  is provided with a protruding positive stop  47  for positioning the core C from the front end. 
     The core material clamping member  38  made of a steel strip is formed in an oblong shape in the axial direction, which is longer than the sewing window  37 , on the left and right hand sides of the cylindrical frame  19  respectively under the tightener  43 . The rear end of the core material clamping member  38  is affixed to the flange  21  with a screw  49  on the left and right sides of cylindrical frame  19  respectively while the front end of the core material clamping member  38  is provided in such a way as to be able to open individually to the left and right relative to the cylindrical frame  19 . Clamping pieces  50  are provided at multiple places inside the core material clamping member  38  and bend in an angle going from top to bottom for elastically contacting the core material C. Temporary latches  51  bend inward at the front end of the core material clamping member  38  in such a way that the temporary latches  51  can elastically engage the annular plate  46  through notches  52  provided on the cylindrical frame  19  in order to hold the core material clamping member  38  temporarily in a closed state. 
     The fabric clamping member  39  comprises, on the left and right sides, a pair of fabric clamps  56  that are oblong in the axial direction and open at the front end. The rear ends of the left and right fabric clamps  56  are connected by a connecting part  55  thus causing the fabric clamping member  39  to have a substantially rectangular shape with an open-ended front. Each fabric clamp  56  is made of a steel strip having a length approximately equal to that of the core material clamping member  38 , and the fabric clamps  56  face the core material clamping member  38  from the outside. Slip guards  53  are made of rubber plates with grooves and are intended to sandwich the work fabric W with the fabric clamps  56  that are glued on the outside of the core material clamping member  38 . A bracket  57  is attached to the left side of the connecting part  55  which is made of a steel plate in a shape that spans the cylindrical frame  19 . A threaded shaft  58  is provided on the bracket  57  on the outside of the left fabric clamp  56 , and the fabric clamping member  39  is fastened to the flange  21  of the cylindrical frame  19  by means of the threaded shaft  58  so that the fabric clamping member  39  can open or close in the lateral (left and right) direction. 
     An oblong surface fastener tape  60  is adhered to the outside surface of each fabric clamp  56 , and a surface fastener belt  61  with open ends is latched to the tape  60  in such a way as to be adjustable in the axial direction in order to coordinate with the support member  40 . An engaging hole  62  is provided at the front end of the left and right fabric clamps  56 , and a surface fastener belt  63  is threaded through the engaging hole  62 . The left and right fabric clamps  56  and the left and right core material clamping members  38  can be tightened against the cylindrical frame  19  in the front and rear of the needle plate  11  where the sewing actions occur by means of the front and rear fastener belts  61  and  63 . The surface fastener belts  61  and  63  can be provided with surface fasteners for the entire surface on the front and back or can be provided only on both ends. 
     The method of using the fabric tensioning device  18  in the sewing machine constituted as described above will be described as follows. In embroidering a piece of tube-like fabric, the cylindrical frame  19  is positioned to cover the outside of the cylinder bed  2 , the mounting area  19   a  is fitted into the drive ring  7 , the flange  21  is clamped to the spring  23 , the lever  22  is engaged with the engaging piece  20 , and the cylindrical frame  19  is mounted tightly on the drive ring  7 , as shown in FIG.  1 . 
     Next, the fabric clamping member  39  is opened toward the left side of the cylindrical frame  19 , and the core material C is moved to abut against the positive stop  47 , as shown in FIGS. 7-8. The core material C is supported by the supporting member  40 , covers the sewing window  37 , and is clamped down against the cylindrical frame  19  to be stretched by means of the core material clamping members  38  on the left and right sides. The following operating advantages can be achieved with the fabric tensioning device  18  of this embodiment: 
     (1) Since the two core material clamping members  38  on the left and right sides are attached to the cylindrical frame  19  in such a way as to be able to open independently, it is possible to clamp down the core material C against the cylindrical frame  19  on the left and right sides independently and align it against the outer periphery of the cylindrical frame  19  easily and accurately. The shape of the remaining portion of the core material C can be adjusted, and the right side of the core material can be clamped by the right core material clamping member  38  to stretch the entire core material C in a smooth cylindrical shape after clamping the left side of the core material with the left core material clamping member  38 . The order of the steps can be reversed to start with the right side. 
     (2) Since the front ends of the left and right side core material clamping members  38  are arranged to be able to open toward the left and right sides of the cylindrical frame  19  respectively, the core material C is less likely to be stretched in a skewed manner and the material can be easily stretched against the cylindrical frame  19  evenly from the front to the rear at the same height. This is in contrast to the prior art wherein the clamping member opened and closed in the vertical direction. 
     (3) Since the temporary latches  51  are provided at the front end of the core material clamping member  38 , the core material C can be held in a smooth, cylindrical shape by temporarily latching one side of the core material C, which makes it easy to adjust the other side of the work fabric W with both hands and to stretch it out neatly. 
     (4) Since the core material clamping members  38  are provided below the tighteners  43 , it is possible to securely prevent the core material C from slackening and deformation while it is temporarily latched. 
     (5) Since the multiple clamping pieces  50  are provided in the inside of the core material clamping members  38 , it is possible to hold various parts of the core material C with an even force using the core material clamping members  38  which are oblong in the axial direction. 
     Next, the work fabric W is placed on top of the core material C as shown in FIGS. 9-10. The fabric clamping member  39  is closed, and the work fabric W is clamped down against the cylindrical frame  19  via the core material C with the left and right fabric clamps  56 . Next, both ends of the front and rear surface fastener belts  61  and  63  are moved to contact and stick together, and they are tightened in order to cause the fabric clamps  56  to tighten against the cylindrical frame  19  together with the core material clamping members  38  to stretch the work fabric W against the cylindrical frame  19 . The following operating advantages can be achieved with the fabric tensioning device  18  of this embodiment: 
     (6) Since the two fabric clamps  56  on the left and right sides are tightened against the cylindrical frame  19  by means of the two front and rear surface fastener belts  61  and  63 , the work fabric W is evenly clamped down on four sides of the needle plate  11 , thus making it possible to stretch it out securely on the cylindrical frame  19  without causing any clamp marks or slack. 
     (7) Since the fabric clamping member  39  is provided in such a way as to be able to open or close in the lateral direction, the core material C and the work fabric W can be neatly and quickly spread out to cover the fully exposed sewing window  37  as shown in FIG.  7 . 
     (8) Since the fabric clamping member  39  is pivot mounted on the flange  21  via the threaded shaft  58  located on the outside of the left side fabric clamp  56 , it is possible to provide a wide space between the left side fabric clamp  56  and the cylindrical frame  19  when the fabric clamping member  39  is opened, thereby allowing the core material C and the work fabric W to be inserted easily in the space as shown in FIG.  8 . 
     (9) Since the left and right fabric clamps  56  face the left and right core material clamping members  38  from the outside, they can be tightened together with two surface fastener belts  61  and  63  to hold the work fabric W and the core material C against the cylindrical frame  19  securely and simultaneously. 
     (10) Since the slip guards  53  are provided on the outside surfaces of the core material clamping members  38 , the work fabric W can be clamped without slack between the core material clamping members  38  and the fabric clamps  56 . 
     (11) Since the surface fastener belts  61  and  63  having open ends on one side are used, the fabric clamps  56  can be tightened by a one-touch operation without causing any slack. 
     (12) Since the rear surface fastener belt  61  is engaged with the surface fastener tape  60  in such a way as to be adjustable in the axial direction, it is possible to tighten the fabric clamps  56  closer to the back of the embroidering position as needed according to the embroidering pattern. 
     (13) Since the front surface fastener belt  63  is threaded through the engaging hole  62  of the fabric clamp  56 , the belt  63  is less likely to get lost. 
     The following operating advantages can be achieved with the sewing machine of this embodiment: 
     (14) Since the cylindrical frame  19  is guided by means of the guide member  27 , which is independent of the needle plate  11 , it is possible to install the needle plate  11  permanently on the cylinder bed  2  in order to use the needle plate  11  not only for the cylindrical frame  19  but also for other types of frames such as a rectangular frame or an annular frame, thus eliminating the need to replace the needle plate  11  for different applications. 
     (15) Since the curved surfaces  11   a  are provided on the left and right shoulder areas of the needle plate  11  close to and facing the inner surface of the cylindrical frame  19 , it is possible to feed the work fabric W smoothly without being stuck on the needle plate  11  and to provide a wide area on the needle plate  11  for supporting the work fabric W. 
     (16) Since the partial cylindrical surface  30  is formed on the left and right side walls  27   b  of the guide member  27  concentric and close to the cylindrical frame  19 , the cylindrical frame  19  can be guided parallel to the cylinder bed  2  with high precision. 
     (17) Since the guide member  27  is formed in an open-ended rectangular shape, it is possible to attach the guide member  27  rigidly on the cylinder bed  2  via the connecting part  27   a , thus effectively preventing vibration. 
     (18) Since the partial cylindrical surface  30  is formed on the left and right side walls  27   b  of the guide member  27 , it is possible to install the bobbin case  4  and form a wide area for the partial cylindrical surface  30 , thereby using the limited space under the needle plate  11  effectively. 
     (19) Since the protection cover  28  is provided detachably on the guide member  27 , the bobbin case  4  is not exposed, thereby making it safer when the cylindrical frame  19  is not used. The bobbin case  4  can be removed or installed easily by removing the cover  28  during the bobbin exchange. 
     (20) Since the partial cylindrical surface  36  is formed on the protection cover  28 , the guide surface  36  provides a wide surface for guiding the cylindrical frame  19  in cooperation with the partial cylindrical surface  30  of the guide surface  27 . 
     This invention should not be construed to be restricted with the embodiment described above, but rather can be constructed in various other ways without leaving the gist of the invention as described below: 
     (a) To pivot-mount the fabric clamping member  39  by a shaft at the rear end so that it can open or close vertically; 
     (b) To form the entire structure of the fabric clamping member  39  with a rod material in an open-ended rectangular shape; 
     (c) To form a slit oblong in the axial direction in one of the fabric clamps  56  of the fabric clamping member  39 , and cause the rear belt  61  to engaged the slit in such a way as to make its position adjustable; 
     (d) To form the core material clamping member  38  with a rod material in an oblong shape in the axial direction; 
     (e) To support rotatably the core material clamping member  38  at its rear end via a shaft and a spring mechanism relative to the cylindrical frame  19 . 
     (f) To provide the core material clamping member  38  and the fabric clamps  56  in positions vertically separated on both the left and right sides of the cylindrical frame  19 ; and 
     (g) To form a portion of the guide device for the cylindrical frame  19  that corresponds to the protection cover  28  integral with the guide member  27  and provide on the outside of the guide member  27  a partial cylindrical surface with an open portion at the top like a C-shape. 
     In the fabric tensioning device for a sewing machine according to the present invention, the two core material clamping members on the left and right sides are mounted on the cylindrical frame in such a way as to be opened or closed independently, so that they press down the core material on both sides of the cylindrical frame independently, thus making it possible to stretch the material easily while matching it properly on the outer circumference of the cylindrical frame.