Patent Abstract:
A device to introduce the upper thread into the eye of the needle ( 7 ) of a sewing machine which includes two guide clips ( 49, 51 ) having two inlet sections ( 53, 55 ) ending in a narrow point. The two guide clips ( 49, 51 ) are generally identical and can spread evenly when encountering the needle. The grasping hook ( 57 ) that lies in a plane in the center of the two guide clips ( 49, 51 ) is always guided exactly centered into the eye ( 25 ) of the needle ( 7 ). In addition, the two guide clips ( 49, 51 ) are mounted for tilting movement about a horizontal axis (B).

Full Description:
BACKGROUND  
         [0001]    The object of this invention is a device to introduce the upper thread into the eye of the needle of a sewing machine.  
           [0002]    It is difficult, especially for older persons, to thread a needle with a necessarily very small eye. For one thing, one has to have a very steady hand and for another thing the end of the thread to be pushed through the eye must be free of frayed fibers. For this tedious work, there have been devices introduced that thread the eye partially by hand using an assisting device, or filly automatically with the touch of a button. Regardless of whether the threading is done by hand or automatically using a suitable device, a very fine hook is always necessary to grasp the thread on the other side of the eye and to form a loop of thread when pulled through the eye. For fine needles, such as those in common use for household sewing machines, the thickness of the hook is approximately 0.2 mm. This results in the smallest forces exerted on the hook bending it, thus rendering the entire device to which the hook is anchored unusable. These forces exerted on the hook can occur if, for example, the sewing needle is slightly bent and the eye is not in the prescribed position as a result so that the hook tilting into it hits the needle. For this reason, most known threading devices have guide clips or plates to the side of the hook with conically diverging ends.  
           [0003]    An example of this can be found in U.S. Pat. No. 2,538,395. The interior sides of the guide clips, i.e. the two surfaces opposite one another, extend parallel to one another and have a separation that is slightly larger than the thickness of the needle. This means that for each needle size, the right size guide clips must be provided. For a thicker needle, it would not be possible for it to be placed in between the guide clips, and for a thinner needle, it would not be centered and thus the hook would be bent. In order to counteract the bending of the hook and to guide a slightly bent needle in between the two guide clips, the threader is hung elastically. The elastic support protects the hook, but—as already mentioned above—not against bending when a non-centered thin needle is grasped.  
           [0004]    From U.S. Pat. No. 5,615,629, another fully automatic threading device is known whereby the two guide clips are produced from an elastic sheet material and whose interior sides run parallel to one another. The ends of the two guide clips can be deflected outward and thus enable a centering with respect to the needle. Most fine hooks are, however, not protected against bending by this known device since the needle cannot be exactly centered in the middle between the two guide clips when, as shown explicitly in an example of U.S. Pat. No. 5,615,629 in FIG. 6, one clip deviates, thus no longer guaranteeing that it will meet the eye of the needle lying in the middle.  
         SUMMARY  
         [0005]    The object of this invention is to create a device to introduce the upper thread into the eye of the needle, wherein the hook always lies exactly in the middle between the two guide clips regardless of the position of the needle and regardless of its thickness.  
           [0006]    This object is met by a device with guide clips that include two first sections that are parallel to one another and two second sections that converge together at an angle and are adjacent to the first sections. The second sections transition into curved fourth sections whose peaks have a smaller distance from one another than the adjacent first sections. The curved fourth sections are followed by diverging fifth sections. Advantageous embodiments of this invention are further described below.  
           [0007]    The similar design of the two guide clips located to the side of the hook, as well as their symmetric suspension makes it possible to always hold the hook located between them exactly at the same distance from the two interior sides of the clips and thus to introduce it into the eye of the needle without contact. Furthermore, the tilting suspension of the plate carrying the guide clips enables an essentially frictionless centering of the two guide clips with respect to the axis of the needle and thus with respect to the eye of the needle. A bent needle will tilt the plate until the guide clips lie symmetric to the needle. The separation of the guide clips at its narrowest point is smaller than the diameter of the thinnest needle. This makes it possible to acceptably center onto the eye of the needle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    This invention is explained in more detail based on a preferred embodiment. In the drawings:  
         [0009]    [0009]FIG. 1 is a partial view of a sewing machine at the front end of the upper and lower arm with needle post and push sole,  
         [0010]    [0010]FIG. 2 is an enlarged representation of the needle post and the stem with the threader,  
         [0011]    [0011]FIG. 3 is a horizontal section view taken along line III-III in FIG. 8 through the threader and the needle when the two guide clips are centered about the needle.  
         [0012]    [0012]FIG. 4 is a view similar to FIG. 3, but prior to the first contact of the grasping clips with the needle,  
         [0013]    [0013]FIG. 5 is an enlarged portion of FIG. 1 with the hook already passed through the eye of the needle,  
         [0014]    [0014]FIG. 6 is a view of the swivel arm with the tilt plate hinged to it and tilted to the side by angle alpha,  
         [0015]    [0015]FIG. 7 is an enlarged view of the swivel arm and the plate shortly before the needle centers the guide clips,  
         [0016]    [0016]FIG. 8 is a view of the device with the upper thread in place,  
         [0017]    [0017]FIG. 9 is a view of the device after the thread hook has grasped the upper thread,  
         [0018]    [0018]FIG. 10 is a side view of FIG. 9. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    In FIG. 1, the front ends of the lower arm  1 , the upper arm  3 , the needle holder  5  and the needle  7  are shown, as are a push sole  9  and the push shaft  11  of a household sewing machine, for example. Indicated below the push sole  9  are the openings  13  for the conveyer as well as the stitch hole  15  for the needle  7 . To the side of the needle  7  and the needle holder  5  is a threader  19  represented that is fixed, preferably onto the stem  17 , said stem  17  moveable vertically at the lower end. The stem  17  with the threader  19  can be lowered to the height of the needle eye  25  by means of a hand lever  21  fastened to the lower end of an actuator  23  (see FIG. 2), and can be rotated in the lowered position about axis A. This rotation is done by means of a coulisse  24  located at the upper section of the actuator  23 . A pin  26  that is fastened to the stem  17  engages this coulisse.  
         [0020]    Lowering and tilting the threader  19  in the described manner is known from the state of the art. Therefore, it is not described in further detail. A known arrangement can be found in DE 914815.  
         [0021]    The device, abbreviated as “threader  19 ”, includes a support  27 , which in the embodiment shown in FIG. 3 is cylindrical, with which the threader  19  can be coupled to the lower end of the stem  17 . A swivel arm  29  is attached to the support  27 . The support  27  and the swivel arm  29  are preferably manufactured in a single piece and are preferably made of plastic. A thread guide sheet  31  wraps around both the support  27  to some extent as well as the swivel arm  29  and extends out tangentially over the support  27 , in the shape of a downward-facing support bracket  33 , and ends to the side of and away from the end of the swivel arm  29  as a bent angled section  35  acting as an feed plate  37 . An open V-shaped slit  39  with an adjacent guide curve  41  is mortised into the feed plate  37  (see FIG. 6). The guide curve  41  is shaped like a “V” placed on end as seen from the side. The thread guide sheet  31  is held on the rear of the swivel arm  29  with suitable fasteners. For example, nubs formed on the swivel arm  29  can be provided as the fasteners, said nubs passing through holes  43  in the thread guide sheet  31  and that are connected to the latter by ultrasonic welds.  
         [0022]    A tilting U-shaped plate  45  is fastened (see FIG. 6 also) to the thread guide sheet  31 , with the plate being wrapped around the thread guide sheet  31  from below with some play. The plate  45  can be hinged by means of bulges  47  formed on both of its sides  45 ′ and  45 ″ that lie opposite to one another, for example. These bulges  47  mate with a hole (not shown) in the thread guide sheet or in recesses attached to it accordingly. At the side  45 ″, two guide clips  49  and  51  that are at right angles to the surface of the side  45 ″, are being stamped out of the plate  45 , which is made of sheet material. See FIG. 7. The two first sections  49 ′ and  51 ′ of the guide clips  49 ,  51  that directly attach to the side  45 ″ of the plate run parallel and are made from an elastic material. Adjacent to these are the two sections  49 ″ and  51 ″, which converge in a cone shape. Adjacent to this are two curved sections  49 ′″ and  51 ′″ whose peaks S′ and S″ are separated from one another by distance a, shown in FIG. 6. This distance a represents the narrowest point between the two guide clips  49 ,  51 . The two end sections  53 ,  55  of the guide clips  49 ,  51  come after the peaks (S′ and S″) diverging along a V shape. End section  55  at the right side can be somewhat longer than end section  53  at the left side in a preferred embodiment. Lying in plane E exactly in the center between the two first sections  49 ′,  51 ′ is a thread hook  57  (FIG. 6). The thread hook  57  is not located exactly between the guide clips  49 ,  51 , but is below them and its rear end is fastened to the side  45 . The hook  57  is of a very fine design so that it can be passed through the eye  25  of even very thin needles  7 , for example of only 0.6 mm width. The thickness of the hook  57  is of the order of magnitude of 0.2 mm. The hook  57  is made of sheet material.  
         [0023]    The U-shaped plate  45  is connected at a point far enough from the lower edge  59  of the thread guide sheet  31  so that the plate  45  can be tilted about its tilt axis B, which is formed by the bulge  47  and the hole behind it, within a prescribable range. The tilt range is a few degrees, for example +/−3 degrees.  
         [0024]    Below, the functioning of the threader  19  is described in more detail. In a known fashion, the stem  17 , along with the hook  57  fastened to its lower end and the two guide clips  49  and  51 , is lowered by pushing down on the hand lever  21  and rotated clockwise shortly before reaching the lowest position. This rotation is accomplished by means of the partially shown coulisse  24  at the upper end of the stem  17 . If an unbent needle  7  is present, the two ends  53 ,  55  of the two guide clips  49 ,  51  meet the needle  7  at the same time and symmetrically. When the stem  17  is further turned, the two guide clips  49  and  51  are spread apart at the same time and in the same amount and the hook  57  located between the two guide clips  49  and  51  can pass through the eye  25  of the needle  7  without touching it. This ideal initial position is not shown in the figures. If the axis of the needle, however, is located offset with respect to the intended position (see FIG. 3), guide clip  49  encounters the needle first. Due to the force acting on the guide clip  49  in the direction of the arrow x (FIG. 4), the plate  45 , to which the two guide clips  49  and  51  as well as the hook  57  are fastened, tilts in a counter clockwise fashion about axis B and centers the two guide clips  49  and  51  about the needle  7 . By further rotating the stem  17 , the hook  57 , which now lies exactly in front of the eye  25  due to the tilting motion of the plate  45 , is pushed through it and extends through the eye  25 , as shown in FIG. 10.  
         [0025]    An upper thread  63 , which is held in a thread guide  61  at the needle holder  5  of the sewing machine, can be threaded through to the slot  41  under the support bracket  33  and the two guide clips  49  and  51 , as shown in FIG. 8. By means of the V-shaped design of the slot  41 , the upper thread  63  approaches the hook  57  from below, as shown in FIG. 9. As soon as the pressure is let off of the hand lever  21 , the stem  17  tilts back and the hook  57  grasps the upper thread  63  and pulls it through the needle eye  25  and throws it upward after rotating by a few degrees of angle and beginning its vertical motion. The loop formed by the hook  57  can be grasped by hand and the end of the thread can be pulled through the needle eye  25 . The threader  19  returns by spring force to its raised protected position beneath the upper arm  3 .

Technology Classification (CPC): 3