Patent Publication Number: US-6666158-B2

Title: Looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine. 
     2. Description of the Prior Art 
     The housing of a conventional sewing machine includes a machine bed, a machine column erecting on right end of the machine bed and a machine arm integrally connected with the top end of the machine column and suspending and leftward extending. A lower driving shaft is mounted in the machine bed and an upper driving shaft is disposed in the machine arm. The lower driving shaft via a toothed belt drives the upper driving shaft, whereby the two driving shafts rotate in accordance with a set timing. A needle bar is fitted through the end of the machine arm. The needle is mounted at bottom end of the needle bar and driven by the upper driving shaft to up and down sew a sewing material. A needle plate is disposed on the machine bed in the needle stroke position. A lower knotting hook is mounted in the machine bed near the needle stroke position. The lower knotting hook is driven by the lower driving shaft and cooperates with the needle to knot the thread and complete the sewing operation. 
     In order to achieve beautiful seam, in each stitching operation, the looper thread must be properly loosened. Conventionally, a thread take-up cam is mounted on the lower driving shaft. Thread guide plates are respectively mounted on two sides of the thread take-up cam. The looper thread is passed through one thread guide plate and then wound over the rim of the thread take-up cam and then passed through the other thread guide plate and finally passed through the eyelet of the lower knotting hook. The thread take-up cam is driven by the lower driving shaft and cooperatively rotates by one circle in each needle stroke travel. The thread take-up cam serves to pull and take up (that is, loosen) the looper thread. Accordingly, the seam on the sewing material will not crimp. 
     It is necessary to adjust the length of each thread take-up travel in accordance with the thickness and variety of the sewing material so as to adjust the tension of the looper thread to an optimal extent. Therefore, a convenient adjustment of the looper thread take-up apparatus is required. In addition, the thread take-up cam rotates at high speed so that the looper thread is subject to breakage and tangling in the groove of the thread take-up cam. Under such circumstance, it is necessary to detach the thread take-up cam for clearing up the tangling thread. Then, the thread take-up cam is again mounted on the lower driving shaft. In addition to the thread take-up cam, many other components are mounted on the lower driving shaft. Therefore, it is a professional task to detach the thread take-up cam from the lower driving shaft of the sewing machine. Moreover, after clearing up the tangling thread, it is necessary to again laboriously install the thread take-up cam back to its home position. Furthermore, after installed back to the home position, it is necessary to again adjust the timings of the respective components. It often takes one or more than one day to complete these procedures. Such complicated works can be hardly independently done by a clothes manufacturer and specialists of the original manufacturer of the sewing machine are required to complete the works. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine. The looper thread take-up apparatus is externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Accordingly, the looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure. In case the looper thread breaks and tangles with the thread take-up cam, it is easy and convenient to clear up the tangling thread from outer side of the sewing machine. 
     It is a further object of the present invention to provide the above looper thread take-up apparatus in which the looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Therefore, the laborious and troublesome task of detachment of the thread take-up cam can be avoided. 
     According to the above objects, the looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine of the present invention includes a thread guide structure and a thread take-up cam. The thread guide structure includes a thread guide plate formed with a slot, and two thread guide eyelets respectively disposed on two sides of the slot. The looper thread take-up structure further includes a looper thread tension adjustment structure disposed beside the thread guide structure. The looper thread is first passed through the looper thread tension adjustment structure to adjust the tension and then sequentially passed through the two thread guide eyelets of the thread guide structure and finally guided to the lower knotting hook of the sewing machine. The thread guide structure and the looper thread tension adjustment structure are mounted on outer side of the housing of the sewing machine and are adjacent to the outer end of the lower driving shaft of the sewing machine. The thread take-up cam is detachably disposed at outer end of the lower driving shaft of the sewing machine and rotatable along with the lower driving shaft. The thread take-up cam is directly detachable from the outer end of the lower driving shaft, whereby the lower driving shaft directly drives the thread take-up cam to rotate so as to take up the looper thread passing through the two thread guide eyelets of the thread guide structure. 
     The looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine further includes a thread guide tube disposed on outer face of machine column of the housing of the sewing machine, whereby the looper thread passing out of one of the thread guide eyelets of the thread guide structure is passed through the thread guide tube and guided to the lower knotting hook of the sewing machine. 
     In the above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine, the thread take-up cam is fixed at outer end of the lower driving shaft via a coupling structure. The coupling structure includes: a clamping member fitted at outer end of the lower driving shaft, the thread take-up cam being fixed at one end of the clamping member, the other end of the clamping member being formed with a split and fitted at the outer end of the lower driving shaft, an end of the split being formed with two slopes; a tightening wedge wedged between the slopes of the split of the clamping member; and a bolt passed through the clamping member from one end to the other end thereof, the bolt being screwed into the tightening wedge, by means of tightening the bolt, the tightening wedge pressing the slopes of the split, whereby the other end of the clamping member is radially expanded to abut against the wall of a shaft hole of a pulley fixed at outer end of the lower driving shaft and tightened in the shaft hole. 
     Alternatively, the looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine of the present invention includes a thread guide structure, a looper thread tension adjustment structure and a thread take-up cam. The thread guide structure includes a thread guide plate formed with a slot, and two thread guide eyelets respectively disposed on two sides of the slot. The thread guide structure being disposed on outer side of the housing of the sewing machine and adjacent to outer end of the lower driving shaft of the sewing machine. The looper thread tension adjustment structure is disposed beside the thread guide structure. The looper thread is first passed through the looper thread tension adjustment structure to adjust the tension and then sequentially passed through the two thread guide eyelets of the thread guide structure and finally guided to the lower knotting hook of the sewing machine. The thread take-up cam passes through the slot of the thread guide structure and is detachably disposed at outer end of the lower driving shaft of the sewing machine and rotatable along with the lower driving shaft. The thread take-up cam is directly detachable from the outer end of the lower driving shaft so as to take up the looper thread passing through the two thread guide eyelets of the thread guide structure. 
     The above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine further includes a thread guide tube disposed on outer face of machine column of the housing of the sewing machine. The looper thread passing out of one of the thread guide eyelets of the thread guide structure is passed through the thread guide tube and guided to the lower knotting hook of the sewing machine. 
     In the above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine, the thread take-up cam is fixed at outer end of the lower driving shaft via a coupling structure. The coupling structure includes: a clamping member fitted at outer end of the lower driving shaft, the thread take-up cam being fixed at one end of the clamping member, the other end of the clamping member being formed with a split and fitted at the outer end of the lower driving shaft, an end of the split being formed with two slopes; a tightening wedge wedged between the slopes of the split of the clamping member; and a bolt passed through the clamping member from one end to the other end thereof, the bolt being screwed into the tightening wedge, by means of tightening the bolt, the tightening wedge pressing the slopes of the split, whereby the other end of the clamping member is radially expanded to abut against the wall of a shaft hole of a pulley fixed at outer end of the lower driving shaft and tightened in the shaft hole. 
     The present invention can be best understood through the following description and accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective exploded view of the present invention; 
     FIG. 2 is a perspective exploded view of the present invention, showing that the present invention is about to be mounted at outer end of the lower driving shaft of the sewing machine; 
     FIG. 3 is a perspective assembled view of the present invention; 
     FIG. 4 is a perspective assembled view of the present invention, showing that the present invention is about to be mounted at outer end of the lower driving shaft of the sewing machine; 
     FIG. 5 is a perspective assembled view of the present invention, showing that the present invention is mounted at outer end of the lower driving shaft of the sewing machine; 
     FIG. 6 is a right view of the present invention, showing that the present invention is mounted at outer end of the lower driving shaft of the sewing machine; 
     FIG. 7 is a top view of the present invention, showing that the present invention is mounted at outer end of the lower driving shaft of the sewing machine; 
     FIG. 8 is a perspective exploded view of the present invention, showing that the present invention is about to be mounted at outer end of the lower driving shaft of another type of sewing machine; 
     FIG. 9 is a perspective assembled view of the present invention, showing that the present invention is about to be mounted at outer end of the lower driving shaft of the other type of sewing machine; 
     FIG. 10 is a right view of the present invention, showing that the present invention is mounted at outer end of the lower driving shaft of the sewing machine; and 
     FIG. 11 is a top view of the present invention, showing that the present invention is mounted at outer end of the lower driving shaft of the sewing machine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to FIGS. 1 to  7 . The present invention provides a looper thread take-up apparatus  20  externally added to outer end of lower driving shaft of a sewing machine. The looper thread take-up apparatus  20  includes a thread guide structure  21  and a thread take-up cam  22 . The thread guide structure  21  includes a thread guide plate  23  formed with a slot  24  and two thread guide members  43   a ,  43   b  respectively locked on two sides of the slot  24  of the thread guide plate  23  by screws  44 . Each thread guide member  43   a ,  43   b  has a thread guide eyelet  25   a ,  25   b . The thread take-up cam  22  is upward passed through the slot  24  of the thread guide plate  23  from lower side thereof. The thread guide structure  21  further includes a thread guide bar  59 . One end of the thread guide bar  59  is locked on one end of the thread guide plate  23  by a screw  60 , coupling seat  64  and a screw  65 . The other end of the thread guide bar  59  is extended into the groove  62  between the two cam plates  61   a ,  61   b  of the thread take-up cam  22  to ride on the other end of the thread guide plate  23 . The thread guide bar  59  is formed with a guide slit  63 . The looper thread is passed through the guide slit  63  and guided by the thread guide bar  59 . 
     The present invention is characterized in that the looper thread take-up apparatus  20  further includes a looper thread tension adjustment structure  26  disposed beside the thread guide structure  21 . The looper thread  27  is first passed through the tension adjustment structure  26  to adjust the tension and then is sequentially passed through the thread guide eyelets  25   a ,  25   b  of the thread guide structure  21 . Finally, the looper thread  27  is guided to the lower knotting hook  32  of the sewing machine. 
     The looper thread tension adjustment structure  26  is mounted on upper side of the thread guide plate  23 . The thread guide plate  23  is locked beside the bracket  46  via a coupling member  45 . The bracket  46  via two screws  47  are locked at the ends of two bolts  48 . The two bolts  47  are passed through a protective hood  49  and locked on outer side of the housing  28  of the sewing machine. The looper thread tension adjustment structure  26  and the thread guide structure  21  are adjacent to outer end of the lower driving shaft  29  of the sewing machine. 
     The thread take-up cam  22  via a coupling structure  50  is fixedly disposed at outer end of the lower driving shaft  29  and rotatable along therewith. The thread take-up cam  22  can be directly detached from the outer end of the lower driving shaft  29 . The lower driving shaft  29  can directly drive the thread take-up cam  22  to rotate so as to take up the looper thread  27  passing through the thread guide eyelets  25   a ,  25   b  of the thread guide structure  21 . 
     The looper thread take-up apparatus of the present invention further includes a thread guide tube  30  which via a coupling plate  66  and a screw  67  is mounted on front face of the machine column  31  of the housing  28 . The looper thread  27  passing out of one thread guide eyelet  25   b  of the thread guide structure  21  is passed through the thread guide tube  30  and guided to the lower knotting hook  32 . 
     A thread guide slat  68  is sandwiched between the looper thread tension adjustment structure  26  and the thread guide plate  23 . One end of the thread guide slat  68  is clamped between the looper thread tension adjustment structure  26  and the thread guide plate  23 . The other end of the thread guide slat  68  is formed with two thread guide orifices  69   a ,  69   b . After the looper thread  27  is downward conducted from the thread rack (not shown) on upper side of the sewing machine, the looper thread  27  is passed through the thread guide orifices  69   a ,  69   b  of the thread guide slat  68  and then passed through the looper thread tension adjustment structure  26 . The looper thread tension adjustment structure  26  includes a thread guide seat  33 , a spacing ring  34 , a bolt  35 , two tension controlling discs  36 , a felt collar  37 , a spring seat  38 , a spring  39 , a sleeve  40  and a tension adjustment rotary switch  41 . The thread guide seat  33  via the bolt  35  is locked on the thread guide plate  23 . Two thread guide orifices  42   a ,  42   b  are respectively formed on two sides of the thread guide seat  33 . The tension controlling discs  36 , felt collar  37 , spring seat  38 , spring  39  and sleeve  40  are sequentially fitted on the bolt  35 . The tension adjustment rotary switch  4  is rotatably fitted on top end of the bolt  35 . The looper thread  27  is first passed through one thread guide orifice  42   a  on one side of the thread guide seat  33  and then passed between the two tension controlling discs  36  and finally passed through the other thread guide orifice  42   b  on the other side of the thread guide seat  33 . After passing through the looper thread tension adjustment structure  26 , a resistance is provided against the looper thread  27 . The magnitude of the resistance is adjusted by means of rotating the tension adjustment rotary switch  41 . The looper thread tension adjustment structure  26  pertains to prior art and is not included in the scope of the present invention. 
     The thread take-up cam  22  is fixed at outer end of the lower driving shaft  29  via the coupling structure  50 . The coupling structure  50  includes a clamping member  51 , a tightening wedge  52  and a bolt  53 . The pulley  54  of the sewing machine has a hub on left side of the shaft hole  55 . The hub is mounted at the outer end of the lower driving shaft  29  of the sewing machine. The right side of the shaft hole  55  of the pulley  54  is vacant. 
     The thread take-up cam  22  via the screw  56  is fixed at right end of the clamping member  51 . The left end of the clamping member  51  is formed with a split  57  and fitted at outer end of the lower driving shaft  29 . The end of the split  57  is formed with two slopes  58 . The tightening wedge  52  is wedged between the slopes  58  of the split  57  of the clamping member  51 . The bolt  53  is passed through the clamping member  51  from right end to left end thereof. The bolt  53  is screwed into the tightening wedge  52 . By means of tightening the bolt  53 , the tightening wedge  52  presses the slopes  58  of the split  57 , whereby the left end of the clamping member  51  is radially expanded to abut against inner face of the hub of right side of the shaft hole  55  of the pulley  54  and thus tightened in the shaft hole  55 . Accordingly, the clamping member  51  is indirectly fixed at outer end of the lower driving shaft  29 . 
     Referring to FIGS. 8 to  11 , the looper thread take-up apparatus  20  of the present invention can be installed on almost any other type of sewing machine. In the case that the position of the fixing hole of the sewing machine is different, various sizes and specifications of brackets  46  and bolts  48  can be provided to overcome this problem. 
     The characteristics of the present invention can include the thread guide structure disposed adjacent to outer end of the lower driving shaft of the sewing machine, the looper thread tension adjustment structure disposed beside the thread guide structure and the thread take-up cam fixedly disposed at outer end of the lower driving shaft and rotatable along with the lower driving shaft. 
     After the looper thread  27  is conducted from the thread rack (not shown) on upper side of the sewing machine, the looper thread  27  is passed through the thread guide orifices  69   a ,  69   b  of the thread guide slat  68  and then passed through one thread guide orifice  42   a  on one side of the thread guide seat  33  of the looper thread tension adjustment structure  26  and then passed through the other thread guide orifice  42   b  on the other side of the thread guide seat  33 . After passing through the looper thread tension adjustment structure  26 , a resistance is provided against the looper thread  27 . The magnitude of the resistance is adjusted by means of rotating the tension adjustment rotary switch  41 . After the resistance is provided to the looper thread  27 , the looper thread  27  first passes through the thread guide eyelet  25   a  of one thread guide member  43   a  and then passes over one cam plate  61   a  of the thread take-up cam  22  and then passes through the guide slit  63  of the thread guide bar  59  extending into the groove  62  of the thread take-up cam  22 . Then, the looper thread  27  passes through the other cam plate  61   a  of the thread take-up cam  22  and then passes through the thread guide eyelet  25   b  of the other thread guide member  43   b . Thereafter, the looper thread  27  passes through the thread guide tube  30  and finally is guided to the lower knotting hook  32  of the sewing machine. 
     The present invention enables the looper thread  27  to pass through the looper thread take-up apparatus  20  externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure fixedly mounted on the lower driving shaft in the housing of the sewing machine. Accordingly, in case the looper thread breaks and tangles with the thread take-up cam, it is easy and convenient to clear up the tangling thread from outer side of the sewing machine. 
     According to the above arrangement, the looper thread take-up apparatus of the present invention has the following advantages: 
     1. The looper thread take-up apparatus of the present invention is externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Accordingly, the looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure. In case the looper thread breaks and tangles with the thread take-up cam, it is easy and convenient to clear up the tangling thread from outer side of the sewing machine. 
     2. The looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Therefore, the laborious and troublesome task of detachment of the thread take-up cam can be avoided. 
     The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.