Abstract:
An adjusting structure for a swing arm and a swinging center that control travel of a sewing machine comprises an adjusting apparatus and corresponding structures cooperating with the adjusting apparatus. The adjusting apparatus is provided on the pivotal portion with a sliding groove and a sliding block that can horizontally slide with respect to each other. Between the sliding groove and the sliding block are further provided an adjusting bolt and an elastic element. By rotating the adjusting bolt, the relative position between the swinging center around which the whole swing arm pivots and the whole structure of the swing arm can be changed in the horizontal direction accurately and conveniently, thus assuredly adjusting the start point of the travel of the presser foot, achieving the objective of accursedly adjusting position of the travel sensing apparatus.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a sewing machine, and more particularly to an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine. 
         [0003]    2. Description of the Prior Art 
         [0004]    In the existing sewing machines, there are many mechanisms used to convert circular motion into linear reciprocating motion, therefore, the control of the travel of the presser feet has great influence on sewing quality. Different presser feet are designed to meet different sewing needs, which require the presser foot to have different travels, for example: when buttons are sewed, the presser foot should be specially designed in such a manner that one end of the presser foot is fixed on one end of the presser foot shaft, and the structure of the presser foot which presses the cloth can move along with the cloth. The corresponding total travel of the presser foot, as shown in  FIG. 1 , includes a first travel X 1  starting from a start point X 11  and ending at an end point X 12  along the long side of the button hole, a second travel Y 1  in the horizontal direction starting from a start point Y 12  and ending at an end point Y 22 , a third travel X 2  starting at a start point X 21  and ending at an end point X  22 , and a fourth travel Y 2  starting at a start point Y 21  and ending at an end point Y 22 . When the presser foot is located at the start point X 11  of the first travel X 1 , the first sensing electrode of the travel sensor in the sewing machine will be turned on to make the sewing machine sew the long side of the button hole which starts from the start point X 11  and ends at the end point of the first travel X 1 . After moving to a position where the second sensing electrode is turned on, the presser foot will start moving horizontally along with the cloth from the start point Y 21  of the fourth travel Y 2  to the end point Y 22  and then directly turns to the start point X 21  of the third travel X 2  for performing the sewing operation along the third travel X 2  and finally turns to the start point Y 21  of the fourth travel Y 2  for performing the sewing operation along the fourth travel until reaching the start point X 11  of the first travel X 1 . 
         [0005]    After the sewing machine is used for a period of time, some parts will become loose, hence, the positions where first and the second sensing electrodes are turned on are often different from the correct positions of the presser foot, which will produce a defective button hole, for example, as shown in  FIG. 1-1 , the two long sides of the button hole are different in length. 
         [0006]    To solve the above problem, the positions where the first and the sensing electrodes of the travel sensing apparatus are turned on and the positions of the presser foot are designed to be adjusted, so that the start point of the respective travels of the presser foot can be controlled. However, since the corresponding adjusting structure is in the form of a cam, in the principle of mechanical designing, it is known that the cam may normally lead to non-single-direction displacement during the adjustment, in other words, when the displacement in the horizontal direction is needed to be adjusted, the displacement in the horizontal direction will be caused synchronously, thus leading to unneeded displacement, so that the travel of the presser foot is thus quite uncertain. 
         [0007]    The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary objective of the present invention is to provide an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine, which utilizes the adjusting apparatus disposed on the swing arm and the pivot shaft which is the swinging center as well as the adjusting bolt of the adjusting apparatus and the elastic element that are disposed between the respective elements to horizontally adjust the relative position and the relation of the whole structure of the swing arm except the swinging center namely the pivot shaft, and immediately position the elements after adjustment. By such arrangements, the swing arm can be accurately brought into contact with the sensing portions of the travel sensing apparatus without complicated adjustment. 
         [0009]    The secondary objective of the present invention is to provide an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine which utilizes the elastic element and the adjusting bolt disposed between the swing arm and the adjusting apparatus to maintain the relevant elements in the optimal elastic prestress state, namely in the optimal pressing state, thus achieving the objective of maintaining the whole structure in the optimal stable state. 
         [0010]    The third objective of the present invention is to provide an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in which the adjusting apparatus is directly mounted on the swing arm and the pivot shaft without any complicated structure or cam, so the assembly of the whole structure is simple, convenient and quick. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic view of a conventional travel for sewing a button hole 
           [0012]      FIG. 1-1  is a schematic view showing that the start and end points of the travel for swing the button hole have error; 
           [0013]      FIG. 2  is a partial exploded view of an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a first embodiment of the present invention; 
           [0014]      FIG. 3  is a planar assembly view of the adjusting structure for a swing arm and a swinging center that control travel of a sewing machine; 
           [0015]      FIG. 4  is a planar operational view of  FIG. 3 ; 
           [0016]      FIG. 5  is another planar operational view of  FIG. 3   
           [0017]      FIG. 6  is a partial exploded view of an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a second embodiment of the present invention; 
           [0018]      FIG. 7  is a planar assembly view of  FIG. 6 ; 
           [0019]      FIG. 8  is a planar assembly view of an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a third embodiment of the present invention; and 
           [0020]      FIG. 9  is a planar assembly view an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    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. 
         [0022]    Referring to  FIG. 2  showing an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a first embodiment of the present invention, the sewing machine includes a suspension arm  100  which is provided at a free end thereof with a presser foot shaft  10  and a fixing rack  20  adjacent to the presser foot shaft  10 . The fixing rack  20  is formed by bending a plate-shaped element and provided with a travel sensing apparatus A in the suspension arm  100 . The travel sensing apparatus A includes a sensor  30 , and a swing arm assembly B which is moved by a presser foot  11  disposed at a bottom of the presser foot shaft  10 . The swing arm assembly B includes a main body  40  for turning on/off the sensor  30 , and a sliding element  50  which is vertically and movably inserted in the main body  40 . A first end of the sliding element  50  is inserted in a bottom end of the main body  40  while a second end of the sliding element  50  protrudes toward the presser foot  11  to a height where the sliding element  50  can be moved by the presser foot  11  when the presser foot  11  horizontally moves to the start and end points of the travel. Since such structures are conventional, no further explanations are provided herein. 
         [0023]    The sensor  30  includes a first sensing portion  31 , a second sensing portion  32  and a movable induction portion  33  disposed between the first and the second sensing portions  31 . The first sensing portion  31 , the second sensing portion  32  and the induction portion  33  are in the form of a metal sheet electrode. Each of the first sensing portion  31 , the second sensing portion  32  and the induction portion  33  is connected to a computer through a wire  34 . The induction portion  33  can be moved by the main body  40  of the swing arm assembly B in such a manner that the induction portion  33  can move toward any one of the two sensing portions  31 ,  32  when the presser foot  11  moves to the start and end points of the travel to push the sliding element  50  and rotate the swing arm  40 . Besides the metal sheet electrodes, the first sensing portion  31 , the second sensing portion  32  and the induction portion  33  in the present embodiment can also be in the form of a photosensitive interrupt sensing element. 
         [0024]    The fixing rack  20  is formed with a threaded hole  200  for locking a pivot shaft  21 . The pivot shaft  21  is pivotally connected to the swing arm assembly B, so that the whole swing arm assembly B can pivot about the pivot shaft  21 . The pivot shaft  21  includes a first end with an outer thread, a middle portion in the form of a cylinder, and a second end formed into a disk-shaped head. The middle portion of the pivot shaft  21  is bigger in outer diameter than the first end of the pivot shaft  21  but smaller in outer diameter than the second end of the pivot shaft  21 . 
         [0025]    The present invention is characterized in that: 
         [0026]    The main body  40  of the swing arm assembly B is provided at a bottom thereof with a pivotal portion  41  in alignment with the threaded hole  200  of the fixing frame  20 . The pivotal portion  41  is a rectangular frame and formed in a center thereof with a hollow rectangular horizontally-extending sliding groove  410 . The pivotal portion  41  is formed in a side surface thereof with an adjusting threaded hole  411  in such a manner that an adjusting apparatus  60  can be screwed into the adjusting threaded hole  411  to perform the adjustment. 
         [0027]    The pivotal portion  41  includes a first side  412 , a second side  413 , a top end  414  and a bottom end  415  that are connected together. The pivotal portion  41  is centrally further provided in each of the top end  414  and the bottom end  415  with a fixing threaded hole  416 ,  417  for insertion of the corresponding elements of the adjusting apparatus  60 . 
         [0028]    The adjusting apparatus  60  includes a sliding block  61  which is square-shaped in cross section allowed to slide relative to the sliding groove  410 . The sliding block  61  is slidably disposed in the sliding groove  410  of the pivotal portion  41  in such a manner that its top and bottom end surfaces that are disposed in the sliding groove  410  abut against the top end  414  and the bottom end  415  of the pivot portion  41 . The sliding block  61  is centrally formed with a pivot hole  610  for insertion of the pivot shaft  21 . When the pivot shaft  21  is fixed in the threaded hole  200 , the pivot hole  610  of the sliding block  61  is just mounted on the pivot shaft  21  in such a manner that the sliding block  61  can rotate on the pivot shaft  21 . 
         [0029]    The sliding block  61  is provided at an end exposed out of the sliding groove  410  with two opposite protruding ears  612  extending in an up and down direction, and each of the two opposite protruding ears  612  includes a horizontally-extending sliding slot  611 . A fixing element  64  in the form of a bolt is inserted through each of the sliding slots  611  and screwed into each of the fixing threaded holes  416 ,  417 , so that the sliding block  61  can be fixed by screwing the fixing elements  64  and released to slide horizontally in the sliding groove  410  by unscrewing the fixing elements  64 . 
         [0030]    The adjusting apparatus  60  is further provided with an elastic element  62  in the form of a coil spring and an adjusting bolt  63 . The elastic element  62  is disposed between the sliding groove  410  and the sliding block  61 . In the present embodiment, the elastic element  62  is disposed in the sliding groove  410  and elastically presses against the second side  413  of the pivotal portion  41  and a first end surface of the sliding block  61 . The adjusting bolt  63  is screwed in the adjusting threaded hole  411  in the first side  412  of the sliding groove  410  and inserted in the sliding groove  410  while pushing against a second end surface of the sliding block  61 . Before adjustment, as shown in  FIG. 3 , the elastic element  62  which is elastically disposed between the sliding groove  410  and the sliding block  61  can provide an elastic prestress between the sliding block  61  and the adjusting bolt  63 . 
         [0031]    When in adjustment, the relative position of the main body  40  with respect to the sliding block  61  and the pivot shaft  21  which is the swinging center of the whole swing arm assembly B can be adjusted by rotating the adjusting bolt  63 , so that the induction portion  33  connected to the main body  40  can be pre-adjusted to contact the first sensing portion  31  as shown in  FIG. 4 . When the presser foot  11  starts moving, the sliding element  50  and the main body  40  will be driven to rotate around the pivot shaft  21 , and then the induction portion  33  will be moved to contact the second induction portion  33  to change a different travel. As shown in  FIG. 5 , in other words, when the induction portion  33  is brought into contact with the first sensing portion  31 , the sewing machine in accordance with the present invention will sew the button hole along the first travel X 1 , and then when the induction portion  33  is brought into contact with the second sensing portion  32 , the sewing machine in accordance with the present invention will sew the button hole along the second travel Y 1  and then the third travel X 2 . After the induction portion  33  is brought into contact with the first sensing portion  31  again, the sewing machine in accordance with the present invention will sew the button hole along the fourth travel Y 2 . 
         [0032]    With the above structures, the present invention can offer the following functions: 
         [0033]    1. Micro-adjustment, quick and high accuracy: with rotation of the adjusting bolt  63  and the pushing of the elastic element  62 , the relative position of the pivotal portion  41  of the main body  40  with respect to the sliding block  61  and the pivot shaft  21  can be quickly adjusted in such a manner that the main body  40  and the pivot shaft  21  only move horizontally relative to each other without causing height difference, so that when the presser foot  11  moves, the swing arm assembly B can accurately move the induction portion  33  to contact the first sensing portion  31  and the second sensing portion  32 , ensuring high accuracy and quality of sewing of the button hole. 
         [0034]    2. Stable overall structure: since the elastic element  62  is elastically disposed between the sliding groove  410  of the pivotal portion  41  of the main body  40  and the sliding block  61  of the pivot shaft  21 , the swing arm assembly B, the pivot shaft  21  and the adjusting apparatus  60  can be assuredly positioned, offering a stable overall structure. 
         [0035]    Referring to  FIGS. 6 and 7  which show an adjusting structure for a swing arm and a swinging center that control travel of a sewing machine in accordance with a second embodiment of the present invention, besides the protruding ears  612 , the sliding block  61  is further formed on the end exposed out of the sliding groove  41  with a laterally-extending L-shaped horizontally extending portion  613 . The horizontally extending portion  613  covers an opening of the sliding groove  410  and includes a threaded hole  614  in an end thereof extending across the first side  412 . An adjusting bolt  63 ′ is screwed into the threaded hole  614  and pushes against the first side  412 . An elastic element  62 ′ in the present embodiment is disposed between the first side  412  and the sliding block  61  and can also offer the above function. 
         [0036]    As shown in  FIG. 8 , the adjusting apparatus  60  can also be configured such that the sliding block  61  having an engaging portion  615  with continuous teeth is mounted on the pivot shaft  21 , and the pivotal portion  41  is formed on an inner surface of the top end  43  with an engaging portion  413  to be engaged with the engaging portion  615  of the sliding block  61 . The sliding block  61  is formed with a bigger disc-shaped head portion on an end thereof exposed out of the sliding groove  410 , so that the user can pull the head portion  616  in the adjustment to make the sliding block  61  move away from the sliding groove  410  along the axial direction of the pivot shaft  21 . After the pivotal portion  41  is moved to a proper position, the sliding block  61  will be re-installed on the pivot shaft  21  in the sliding groove  410 , and the engaging portion  615  will be re-engaged with the engaging portion  413  of the sliding groove  410 . 
         [0037]    As shown in  FIG. 9 , the sliding block  61  can also be in the form of a column and includes a sector engaging portion  617  to be engaged with the engaging portion  413  of the sliding groove  410  in the above embodiment. The pivotal portion  41  can be horizontally moved for adjustment by rotating the sliding block  61 . 
         [0038]    In the present invention, between the sliding element  50  and the main body  40  is additionally provided an arc elastic plate  51  for producing an elastic frictional force when the sliding element  50  is moved in the main body  40 . The elastic plate  51  is disposed at one side of the bottom end of the main body  40  where the sliding element  50  is inserted, so that when the sliding element  50  is inserted in the main body  40 , the elastic plate  51  will elastically push against the sliding element  50 . 
         [0039]    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.