Abstract:
A drive arrangement for the drive elements for the threading of the upper thread into the eye of a sewing machine needle is provided. Instead of individual drives for lowering the threading device and rotating it as well as threading the thread regulator to deflect the upper thread around the thread brake, drives not used at that time for the needle rod, the presser foot pressure, and the thread brake are utilized. In this way, two to three additional electric drives can be omitted and thus the controlling expense can be reduced.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Swiss Application no. 00354/06, filed Mar. 3, 2006, which is incorporated herein by reference as if fully set forth. 
       BACKGROUND 
       [0002]    The invention relates to a drive arrangement for the drive elements for threading the upper thread into the eye of the needle of a sewing machine. 
         [0003]    Drive arrangements for threading devices of this type are known in many embodiments. They serve to relieve the operator of the sewing machine from the tedious threading of the upper thread into the eye of the needle. Simple threading aids are operated manually, i.e. the upper thread is inserted into a suitable tool and this facilitates the treading process. In automatic threading devices first the thread must be placed in front of the device before the latter then performs the threading process via separate drives in the sewing machine. 
         [0004]    The most frequently used automatic threading devices pivot the threader around a horizontal axis downwards from a resting position in the upper arm towards the needle. Further, motorized threading devices are also known in which, similar to the manually operated ones, the threading device is guided vertically downwards along an actuator rod parallel to the needle rod and is pivoted out of this position around said actuator rod. These known threading devices require a suitable electric drive for the lowering process, e.g., a stepper motor, which guides the threading device via a toothed rod downwards and, after the threading, back upwards. Here, the pivoting motion inevitably occurs in a curved path, along which the device at the end of the lowering motion is additionally rotated around the actuator rod. 
         [0005]    Both the threading devices with motion around the horizontal axis in the upper arm of the sewing machine as well as those that are vertically displaced by an electric motor need comparatively much space. This leads to a voluminous upper arm housing, which limits the direct visual contact of the operator to the sewing area. 
       SUMMARY 
       [0006]    One object of the present invention comprises providing a drive arrangement for the drive elements for a threader, which requires little space and which, in the resting position, also can essentially be retracted entirely into the upper arm and thus prevents any hindrance to handling during the sewing operation. 
         [0007]    This object is attained by a drive arrangement for the drive elements for a threader having the features of the present invention, in which the threader is embodied such that it can be connected to the needle rod actuator that is decoupled from the needle rod. Advantageous embodiments of the device are described below. 
         [0008]    By omitting a separate, individual drive, the invention achieves maintaining a small space that is necessary for the processing motions of the threading device, so that there is sufficient room inside a narrow housing. Further, supervision devices are omitted, which control and/or synchronize the respective position of the needle rod and thus the eye of the needle and the threading device. All motions necessary for threading occur automatically synchronized. By omitting one or more additional drive motors for the threading device and alternatively also for the controllable threading motor, the necessary controls and/or the already mentioned synchronization of the individual drives connected thereto is also omitted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention is described in the following using an illustrated exemplary embodiment. Shown are: 
           [0010]      FIG. 1  is a schematic perspective representation of a sewing machine with a lowered threader, 
           [0011]      FIGS. 2   a - d  are views showing four separate positions of the threader, and 
           [0012]      FIGS. 3   a - d  are schematic representation of the operating processes of the drive of the threading device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]      FIG. 1  shows in a schematic representation a household sewing machine  1  with a base plate  3 , a free arm  5 , as well as an upper arm  7 . The free arm as well as the upper arm are connected to each other by the machine housing  9  A threading device  11  is arranged in the front end of the upper arm  7 , which can be deployed from the bottom  13  of the upper arm  7 . In  FIG. 1  the threading device  11  is entirely deployed, i.e. lowered. On the upper side of the upper arm  7  schematically a spool holder for the upper thread is shown having an upper thread spool  15 . Further, reference character  17  indicates a needle, having an eye of the needle  19  at its lower end. The needle  17  is connected to the bottom end of a needle rod  21 . A presser foot rod  23  is shown behind the needle rod  21 , with the presser foot  25  being mounted to its lower end. 
         [0014]    The elements, briefly described above, are illustrated schematically in more detail in  FIGS. 2   a  through  2   d , separated from the sewing machine. In  FIG. 2   a , the presser foot rod  23  with the presser foot  25  is lifted off the stitching plate  27  on the lower arm  5  by a distance α. The raising of the presser foot  25  occurs in a manner known per se by a lifter lever (or can be motorized), which is not shown therefore to improve visibility. A toothed rod  29  with an actuator  31  is mounted and guided longitudinally parallel to the presser foot rod  23 . A spring  37  is clamped between the lower end  33  of the toothed rod and a bracket  35  mounted to the presser foot rod  23  in a fixed manner. The spring is only slightly stressed when the presser foot  25  is raised. The toothed rod  29  is engaged with a sprocket  39 , which can be driven by an electric motor, e.g., a stepper motor  41 . The reference characters  42   a  and  42   b  indicate longitudinal guides for the presser foot rod  23 . 
         [0015]    In  FIG. 2   b  the presser foot rod  23  with the presser foot  25  is lowered to the stitching plate  27  via the lifting lever (not shown) or in a motorized manner. Simultaneously the toothed rod  29  has been lowered by the stepper motor  41  and thus the spring  37  has been stressed further. The tensile force of the spring  37  serves to press the presser foot rod  23  with the presser foot  25  toward the stitching plate  27  using the bracket  35 . Thus the pressure of the presser foot  25  to the stitching plate and/or the sewing material (not shown) positioned between the presser foot  25  and the stitching plate  27  can be adjusted by the stepper motor  41 . 
         [0016]    The two functions shown in  FIGS. 2   a  and  2   b  are known from prior art and are used in higher priced sewing machines. 
         [0017]    In  FIG. 2   b  it is further discernible that the actuator  31 , which is not included in conventional sewing machines, is positioned at a short distance above the two-armed lever  43 . The two-armed lever  43  is linked to a threader  45  in a mobile fashion. The first leg  43   a  of the lever  43  extends below the actuator  31  at a distance; the second leg  43   b  of the lever  43  carries a hook  43   c  on a free end thereof. The hook is located outside the vertical displacement area of the needle rod actuator  47  in the position of the toothed rod  29  shown in  FIG. 2   b . The actuator is connected to the driving device, needle drive  49  for short. The needle drive  49  with the needle rod actuator  47  is known from prior art and comprises, as shown in  FIGS. 2   c  and  2   d , a crank drive  51 . The actuator  47  is decoupled from the needle rod  21  in the positions shown in  FIGS. 2   b  through  2   d . When now the toothed rod  29  is further lowered by the stepper motor  41  out of the position shown in  FIG. 2   b  into the position shown in  FIG. 2   c  the actuator  31  pivots the leg  43   a  of the lever  43  clock-wise such that the hook-shaped end  43   c  reaches a position below the needle rod actuator  47  ( FIG. 2   c ). Preferably, a suitable bolt  53  is arranged at the needle rod actuator  47 . Now, the threader  45  can be lowered ( FIG. 2   d ) by the needle rod actuator  47  via the needle drive  49 . 
         [0018]    During the lowering of the threader  45 , a threading hook  55  is inevitably pivoted around the axis A of the threader  45  in a curve not shown and the threading process can be performed. The threading process is not described in greater detail, because it can occur in differently operating devices regardless of the processing steps described in  FIGS. 2   a  through  2   d.    
         [0019]    After the threading process the needle drive  49  guides the needle rod actuator  47  upwards, which simultaneously causes the threader  45  to be returned into the resting position by the tensile force of a second spring  57  stressed during the lowering of the threader  45 . 
         [0020]    Similar to the exemplary embodiment in  FIGS. 1 and 2   a - 2   d , for the motion drive of the threader  11  with the already existing drives for the needle rod  21  and the presser foot pressure the transfer of the upper thread can also lead to a deflection, which increases the wrapping angle of the thread brake  61 , and thus leads to the insertion of the thread regulator (not shown) having an existing drive, namely the drive motor  59  for the thread brake  61 . In  FIGS. 3   a  through  3   d , in four steps, it is shown schematically how, on the one side, the structure of the braking force occurs in the thread brake  61  with the drive motor  59  of the thread brake  61  and how a thread deflection lever  73  can be operated by the same motor. 
         [0021]    In the illustrations in  FIGS. 3   a - 3   d , the thread brake  61  is shown, which comprises two discs that can be elastically pressed against each other (not shown in detail). The two discs are located axially behind the thread brake  61 , shown schematically as a circular plate. An actuator disc  63 , its periphery being embodied as a sprocket, which is engaged by a driving sprocket  65  of the drive motor  59 , is arranged between the drive motor  59  and the thread brake  61 . At the face of the actuator disc  63 , a toothed segment  67  is arranged pivotal around the rotary axis A of the actuator disc  63 , which includes a protrusion  69  on one side. The protrusion  69  contacts the cam  71  in the resting position ( FIG. 3   c ). A thread displacement lever  73  is pivotally arranged on a pivot axis B located outside the periphery of the actuator disc  63 . In the area of the deflection of the thread deflection lever  73 , the lever is provided with a toothed segment  75 , which engages the teeth of the toothed segment  67  on the actuator disc  63 . An actuator hook  77  is formed at the free end of the thread displacement lever  73 . 
         [0022]      FIG. 3   c  shows, as already mentioned, the resting position of the actuator disc  63 , in which the first toothed element  67  contacts the cam  71  and in which the thread brake  61  and the two discs forming the thread brake  61  are at a distance (from each other) so that the upper thread can be inserted thereto. In a known fashion, after the threading of the thread by the drive motor  59 , the thread brake  61  and/or a spindle are driven, thus the two discs of the thread brake  61  approach one another. Here, the cam  71  moves on the actuator disc  63  counter-clock wise by approx. 180° ( FIG. 3   b ). When the thread tension must be increased even more, the drive motor  59  further rotates the actuator disc  63  in the counter-clockwise direction until the cam  71  approaches the protrusion  69  on the first toothed segment  67  from the other side (cf.  FIG. 3   a ). 
         [0023]    At the beginning of the threading process for the upper thread the thread brake  61  is in the resting position according to  FIG. 3   c . In order to achieve an optimum deflection of the upper thread into the thread brake  61  and/or to insert the thread into the thread regulator, the upper thread  79 , initially extending in a straight manner, must be deflected towards the thread brake  61 . This occurs via the thread deflection lever  73 , with its actuator hook  77  grasping the upper thread and transferring it from the initial position X into the deflection position Y. In order to transfer the thread deflection lever  73  from position X into position Y the rotational direction of the drive motor  59  is reversed so that the actuator disc  63  rotates in the clockwise direction. Here, the cam  71  also rotates the first toothed segment  67  in the clockwise direction and thereby pivots the thread deflection lever  73  engaging the toothed segment  67  into the position Y ( FIG. 3   d ). 
         [0024]    As soon as the thread deflection lever  73  reaches position Y, the upper thread leaps over a deflection protrusion, not shown, and is guided there such that the thread deflection lever  73  is returned into the resting position by rotating the drive motor  59  in the opposite rotational direction and, when the motor  59  continues to rotate in the same rotational direction the thread brake  61 , according to  FIGS. 3   b  and/or  3   a , can be stressed. The drive motor  59  of the thread brake  61  therefore performs two entirely different tasks: at the beginning of the threading process the thread deflection lever  73  pivots out of the resting and catching position into the transfer position Y and subsequently it serves to regulate the thread brake  61 . 
       LIST OF REFERENCE CHARACTERS 
       [0000]    
       
           1  sewing machine 
           3  base plate 
           5  free arm 
           7  upper arm 
           9  machine housing 
           11  threading device 
           13  bottom of 
           15  upper thread spool 
           17  needle 
           19  eye of the needle 
           21  needle rod 
           23  presser foot rod 
           25  presser foot 
           27  stitching plate 
           29  toothed rod 
           31  actuator 
           33  bottom end of  29   
           35  bracket 
           37  spring 
           39  sprocket 
           41  stepper motor 
           42  longitudinal guidance 
           43  two-armed lever 
           45  threader 
           47  needle rod actuator 
           49  needle drive 
           51  crank drive 
           53  bolt 
           55  threading hook 
           57  spring 
           59  drive motor for thread brake 
           61  thread brake 
           63  actuator disc 
           65  sprocket for downward drive 
           67  toothed segment 
           69  protrusion 
           71  cam 
           73  thread deflection lever 
           75  toothed segment 
           77  actuator hook 
           79  upper thread