Abstract:
A needle threading device of a sewing machine, wherein an operating lever is manually operated to move down against spring action until a threading hook secured to the lower end of a threading bar comes to a position where there is an eye of machine needle. The threading bar is then axially rotated. With the axial rotation of the threading bar, the threading hook is rotated to pass through the needle eye. With release of the operating lever from the manual operation, the threading bar is moved up by spring action while the threading hook catches an upper thread of the sewing machine and is pulled out of the needle eye.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a sewing machine and a needle threading device mounted to a sewing machine. 
   2. Related Art 
   So far, many inventions have been made in connection with a device for threading a needle of sewing machine. For example, the Japanese patent laid open 2003-38886 discloses a needle threading device of a sewing machine wherein a threading bar is moved down in association with operation of a threading lever, and is stopped at a position where the eye of machine needle is located. 
   As the threading lever is further pressed down, the threading bar is rotated by means of a cam which is so formed to rotate the threading bar. Then a hook is inserted into the eye of needle from the rear side to the front side of the needle. The operator hangs the upper thread to the hook and releases or moves up the threading lever. Then the hook is moved back as the threading bar is moved up and the upper thread is pulled to pass through the needle eye. Thus the threading operation is finished. 
   OBJECT OF THE INVENTION 
   However the conventional threading devices require the machine operator to pay a special attention for guiding the upper thread to hang it to the hook. Further the machine operator is required to hold the upper thread as is hanged to the hook until the hook is moved back and the threading bar is moved up. Otherwise, the upper thread may slip out from the hook. Namely the machine operator of little experience will often fail to thread the machine needle. It is, therefore, an object of the invention to eliminate the defects and inconveniences of the prior art and to provide a threading device wherein the upper thread may be guided to the hook without requirement of the machine user to hold the upper thread, and the upper thread may be securely held in a pocket of the hook before the hook is moved back and slipped out from the needle eye. 
   SUMMARY OF THE INVENTION 
   The sewing machine of the invention is provided with a needle having a needle eye formed at the lower end thereof, a threading hook which may be inserted or passed through the needle eye and may catch an upper thread of sewing machine which is brought to engage the threading hook, a hook inserting means for inserting the threading hook through the needle eye and for pulling the threading hook out of the needle eye, a thread holding means for holding the upper thread with a tension applied thereto, a thread moving means which is operated in association with the hook inserting means to move the upper thread held by the thread holding means to a position where the upper thread may be caught by the threading hook which is inserted through the needle eye, the threading hook being pulled back from the needle eye to pass the upper thread through the needle eye. 
   The thread moving means is operated to move the upper thread in a manner that the upper thread is caught by the threading hook which is inserted through the needle eye and is pulled back from the needle eye. In a preferred embodiment, the upper thread is brought to a position where the upper thread is caught by the threading hook when the threading hook is retreated from the needle eye. 
   It is preferable that the threading hook, the hook inserting means, the thread holding means and the thread moving means are normally maintained in a vertically higher position with respect to the machine needle and are moved down as is necessary. In the structure, the thread holding means and the thread moving means are moved up and down with the threading hook in association with operation of the hook inserting means. 
   It is preferable that the upper thread to be passed through the needle eye is attached to the thread holding means by the machine operator when the latter is in a lower position with respect to the machine needle. 
   In a preferred embodiment, the thread holding means holds the upper thread on the side of machine needle where the threading hook is protruded through toward the machine operator such that the upper thread may be moved up along the needle to a position where the upper thread is caught by the threading hook as the thread holding means is moved up by the thread moving means. The threading hook is typically of a shape of horizontally extending shank having a downwardly extending thread catching hook, the hook being pulled back from the needle eye as the upper thread is moved up along the needle in contact therewith to a position where the upper thread is caught by the hook. The threading operation is finished when the threading hook is pulled back because the upper thread is caught by the threading hook and is passed through the needle eye together with the threading hook. 
   In a preferred embodiment, the thread inserting means, the threading hook and the thread holding means are normally urged in the upper direction by spring action and are normally held in an upper inoperative position. The thread inserting means is manually operated against spring action to move down the threading hook and the thread holding means to a lower operative position where the threading hook is inserted through the eye of machine needle and the thread holding means moves the upper thread to a position where the upper thread is caught by the threading hook. 
   Subsequently when the thread inserting means is released from manual operation, the thread inserting means is moved up by spring action while the threading hook is pulled back from the needle eye catching the upper thread held by the thread holding means. 
   The thread moving means includes a mechanism for jumping up the thread holding means to a position where the upper thread is caught by the threading hook as the latter is pulled back from the needle eye. 
   Typically the threading hook is supported by a threading member which is moved down as the thread inserting means is moved down from an upper inoperative position to a lower operative position where the threading member is rotated in a manner that the threading hook is passed through the eye of machine needle. Subsequently the threading means is released and returned to the upper inoperative position by spring action while the threading member is rotated back and the threading hook is accordingly pulled back from the needle eye and is returned to the upper inoperative position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     
       FIG. 1 
     
     ( a ) is a front elevational view of a threading device of the invention showing the structure thereof. 
     ( b ) is a rear side view of the threading device. 
     
       FIG. 2 
     
     ( a ) is a perspective view of the threading device shown as located at a lower position. 
     ( b ) is an exploded view of the threading device. 
     
       FIG. 3 
     
     ( a ) is a perspective view of the essential part of the threading device. 
     ( b ) is the rear side view of the essential part of the threading device. 
     
       FIG. 4 
     
     ( a ) is a side elevational view of the essential part of threading device showing an auxiliary mechanism for holding the upper thread to be threaded. 
     ( b ) is a perspective view of the auxiliary mechanism for holding the upper thread to be threaded. 
     ( c ) is an exploded view of the auxiliary mechanism for holding the upper thread to be threaded. 
     
       FIG. 5 
     
     ( a ) is a front elevational view of the auxiliary mechanism for holding the upper thread shown as located at an upper position relative to a machine needle. 
     ( b ) is a perspective view of the auxiliary mechanism for holding the upper thread shown as located at a lower position relative to the machine needle. 
     ( c ) is a front elevational view of the auxiliary mechanism for holding the upper thread shown as located at the lower position relative to the machine needle. 
     ( d ) is a plan elevational view of the auxiliary mechanism shown in lateral section as located at the lower position relative to the machine needle. 
     
       FIG. 6 
     
     ( a ) is a perspective view of the auxiliary mechanism for holding the upper thread shown as located at the lower position relative to the machine needle with a threading hook being inserted through the eye of machine needle. 
     ( b ) is a plan elevational view of the auxiliary mechanism for holding the upper thread shown in lateral section as located at a lower position relative to the machine needle with the threading hook being inserted through the eye of machine needle. 
     ( c ) is a side elevational view of the auxiliary mechanism for holding the upper thread shown in vertical section as located at the lower position relative to the machine needle with the threading hook being inserted through the eye of machine needle. 
     
       FIG. 7 
     
     ( a ) is a perspective view of the auxiliary mechanism for holding the upper thread shown as located at the lower position relative to the machine needle with the threading hook being inserted through the eye of machine needle. 
     ( b ) is a front elevational view of the auxiliary mechanism for holding the upper thread shown as located at the lower position relative to the machine needle with the threading hook being inserted through the eye of machine needle. 
     ( c ) is a plan elevational view of the auxiliary mechanism for holding the upper thread shown in lateral section as located at the lower position relative to the machine needle with the threading hook being inserted through the eye of machine needle. 
     ( d ) is a side elevational view of the threading hook shown in vertical section as inserted through the eye of machine needle with the upper thread being moved to hang to the threading hook. 
     
       FIG. 8 
     
     ( a ) is a perspective view of the auxiliary mechanism for holding the upper thread shown as having inserted the upper thread through the eye of machine needle. 
     ( b ) is a plan elevational view of the auxiliary mechanism for holding the upper thread shown in lateral section as having inserted the upper thread through the eye of machine needle. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention will now be described in reference to preferred embodiments as shown in the attached drawings. As particularly shown in  FIGS. 1 and 2 , The invention is substantially composed of a threading shaft member A, a fixed guide member B, an operating member C, a thread holding member D and so on. These members A, B and C are mounted on a needle bar holder  1 . The needle bar holder  1  is swingingly movable in a machine arm (not shown) and holds a needle bar  16  by means of upper and lower supports  1   a ,  1   a  such that the needle bar may be vertically reciprocated and may swing with the needle bar holder  1  laterally of the cloth feeding direction. 
   As shown in  FIG. 2(   b ), the threading shaft member A includes a threading bar  2 , a guide pin  3  and a threading member  4 . The guide pin  3  is arranged normal to the threading bar  2  as laterally extending therethrough with both ends protruded at an upper part about ⅓ of the entire length of the threading bar  2 . The guide pin  3  is operated by way of the operating member C and a guide member  9  to vertically move the threading bar  2  as will be described in detail hereinlater. 
   As shown in  FIG. 2(   b ), the threading member  4  includes an arm  4   a , a threading hook  4   b , a hollow cylindrical part  4   c  and a protrusion  4   d . The threading member  4  is secured to the lower end of the threading bar  2  by means of the hollow cylindrical part  4   c  with a pin or the like diametrically inserted into the hollow cylindrical part  4   c  and into the threading bar  2  which is axially inserted into the hollow cylindrical part  4   c . such that the threading member  4  may be rotated as the threading bar  2  is rotated. The protrusion  4   d  is formed as a part of the hollow cylindrical part  4   c  and is operated to move the thread holding member D up and down as will be described in detail hereinlater. 
   The threading hook  4   b  is arranged at one end part of the arm  4   a  and is opposite to the hollow cylindrical part  4   c  which is arranged at the other end of the arm  4   a . The threading hook  4   b  is of a size which may freely pass through an eye  17  of a machine needle  17  which is attached to the lower end of a needle bar  16  as will be described in detail hereinlater. The arm  4   a  has a pair of spaced guides  4   e ,  4   e  provided therewith on both sides of the threading hook  4   b  such that the guides  4   e ,  4   e  may engage the opposite edges of the machine needle  17  as the arm  4   a  is moved toward the needle  17 . Further the threading member  4  has a thread anchor  4   f  formed therewith adjacent the hollow cylindrical part  4   c  for anchoring and guiding the upper thread as will be described in detail hereinlater in reference to  FIGS. 5 through 8 . 
   The guide pin  3  and the arm  4   a  of the threading member  4  are arranged with a predetermined angle provided therebetween. The angle is determined by the rotation angle of the threading bar  2  which is axially rotated by cooperation between the guide pin  3  and a guide groove  7  of the fixed guide member B as will be described in detail hereinlater. The threading bar  2  is normally urged in the upper direction by a coil spring  5  which is provided around the threading bar  2  between the guide pin  3  and the lower support  1   a  of the needle bar holder  1 . Namely the threading member  4  secured to the lower end of the threading bar  2  is normally located at an upper position. 
   As particularly shown in  FIG. 1(   a ) and  FIG. 2(   b ), the fixed guide member B is mounted to the needle bar holder  1 . The fixed guide member B includes a fixed plate  6  having the guide groove  7  formed thereat which is in engagement with the guide pin  3 . The guide groove  7  has a first region for vertically guiding the threading bar  2  by means of the guide pin  3  and a second region for axially rotating the threading bar  2  by means of the guide pin  3 . Precisely the guide groove  7  includes an upper straight region  7   a  for vertically moving the threading bar  2  while the threading bar  2  is not axially rotated, the next slightly inclined region  7   b  for vertically moving the threading bar  2  while the threading bar  2  is axially rotated and the lowest set groove region  7   c.    
   The inclined region  7   b  of the guide groove  7  is so formed as to enable the threading hook  4   b  to avoid the parts of sewing machine while the hook is moved down in threading operation. The set groove region  7   c  is the second region in which the guide pin  3  is positioned to rotate the threading member  4  to a predetermined position. Thus the guide groove  7  is so formed as to guide the guide pin  3  such that the threading hook  4   b  of the threading member  4  may move toward the eye  17   a  of the machine needle  17  attached to the lower end of the needle bar  16 . Namely the threading bar  2  begins to axially rotate when the guide pin  3  comes to engage the inclined groove region  7   b , and when the guide pin  3  comes to engage the set groove region  7   c , the threading bar  2  is further rotated to pass the threading hook  4   b  through the needle eye  17   a.    
   The inclined groove region  7   b  rotates the guide pin  3  axially of the threading bar  2  as the guide pin  3  is moved down along the inclined groove region  7   b . The threading bar  2  and the arm  4   a  of the threading member  4  are rotated accordingly. The set groove region  7   c  is continuous from the inclined region  7   b  in the lower direction and is opened toward the inclined direction. 
   As shown in  FIG. 2(   b ), the needle bar  16  has a positioning member  13  secured thereto. The positioning member  13  engages guide pin  3  when the threading member  4  comes to the position opposite to the eye  17   a  of machine needle  17 , and stops the downward movement of the threading bar  2  and then axially rotates the threading bar  2 . The positioning member  13  includes a vertically extended plate having a laterally extended stopper projection  13   a  formed at the lower end thereof, the stopper projection  13   a  having a cutout  13   b  formed thereat for receiving the guide pin  3 , and further includes a connecting member  13   c  for connecting the positioning member  13  to the needle bar  16 . The stopper projection  13   a  has an upper side formed generally horizontal and extended into the cutout  13   b.    
   The stopper projection  13   a  and the cutout  13   b  of the positioning member  13  determine the position where the threading hook  4   b  may pass through the needle eye  17   a  while preventing the vertical movement of the guide pin  3 , thereby to prevent the damage of the threading hook  4   b  and the machine needle  17 . The connecting member  13   c  of the positioning member  13  is secured to the needle bar  16  at an appropriate position by means of a screw or the like such that the guide pin  3  may be stopped in accordance with variation of the height of the needle eye  17   a.    
   The operating member C is provided so as to be vertically moved relative to the fixed guide member B. The operating member C includes a movable base  8 , a movable guide  9  formed with a guide groove portion  10  and further includes an operating lever  11 . The movable base  8  is formed with a vertical hole  8   a  through which the threading bar  2  is inserted in a manner that the movable base  8  is supported by the threading bar  2 . 
   As shown in  FIGS. 1 and 2 , the operating member C has the movable base  8  and the movable guide  9  formed in one body with the guide groove portion  10  formed between the movable base  8  and the movable guide  9 . The guide groove portion  10  is placed in engagement with the fixed guide plate  6  of the fixed guide member B so as to guide the vertical movement of the operating member C. The movable base  8  is connected to the threading shaft member A with the threading bar  2  being inserted through the vertical hole  8   a  of the movable base  8 . The coil spring  5  is mounted around the threading bar  2  between the underside of the movable base  8  and the lower needle bar support  1   a  such that the movable base  8  is normally urged in the upward direction by the coil spring  5 . 
   As shown in  FIGS. 1 and 2 , the movable guide  9  has a slot  9   a  formed thereat. The slot  9   a  receives the guide pin  3  so as to vertically move guide pin  3  and the threading bar  2  accordingly as the operating member C is vertically moved. The slot  9   a  is inclined at an appropriate angle, generally 45°, but not strictly limited to the mentioned angle. The slot  9   a  is inclined in the direction opposite to the inclined groove region  7   b  of the guide groove  7 . 
   The inclined slot  9   a  is so inclined to give a desired rotation speed of the guide pin  3  as the inclined slot  9   a  moves along the inclined groove region  7   b  of the guide groove  7 . In case the inclination of the inclined slot  9   a  is acute, the rotation speed of the guide pin  3  is fast and in case the inclination of the inclined slot  9   a  is obtuse, the rotation speed of the guide pin  3  is slow. Namely the rotation speed of the threading bar  2  and of the arm  4   a  of the threading member  4  is determined by the degree of inclination of the slot  9   a . The slot  9   a  may be formed as generally extending horizontal. In this case, the rotation speed of the guide pin  3  is fastest. 
   The operating lever  11  includes a trunk  11   b  having a knob  11   a  formed at the lower end of thereof. The trunk  11   b  is extended vertically from the movable base  8  and is formed with a projection  11   c  laterally extended therefrom. The knob  11   a  may be pressed down with a finger of machine operator against the force of the coil spring  5  to move down the threading shaft member A. The operating member C is mounted to the fixed guide member B with the groove portion  10  being placed in engagement with the guide plate  6  of the fixed guide member B. 
   As shown in  FIGS. 3 and 4 , the thread holding member D includes a base  20  that is a base plate  20   a , a movable plate  21 , a thread holder  22  having a thread holding part  23 . The base plate  20   a  is secured to the sewing machine arm (not shown). The base plate  20   a  has a lower part  20   b  bent generally normal to the base plate  20   a . The lower part  20   b  has a vertical guide groove  20   b   1  formed thereat. The movable plate  21  is arranged in engagement with the vertical guide groove  20   b   1  such that the movable plate  21  may be vertically movable relative to the base plate  20   a . Further the base plate  20   a  has an arm  20   c  formed at the upper part thereof to which the upper end of a tension spring  25  is anchored. 
   The movable plate  21  includes a body  21   a  having a pair of pins  21   b ,  21   ba  which are inserted into the vertical groove  20   b   1  of the base plate  20   a  such that the movable plate  21  may be vertically moved as guided by the vertical groove  20   b   1 . The movable plate  21  is bent at the lower end thereof to provide a horizontally flat surface  21   c  which is to be pressed down by the protrusion  4   d  of the threading member  4  such that the movable plate  21  may be moved down. The movable plate  21  has an upper part  21   d  for anchoring the lower end of the tension spring  25 . Thus the movable plate  21  is normally urged in the upper direction by the tension spring  25 . 
   The thread holder  22  has a pivot hole  22   a  by which the thread holder  22  is pivotally mounted to the movable plate  21 . The thread holder  22  has one end bent to be an engaging part  22   b  which is to be pressed down by the lateral projection  11   c  of the operating lever  11  on one side of the pivot hole  22   a . Further the thread holder  22  has an arm  22   c  on the other side of the pivot hole  22   a , the arm  22   c  having a thread holding assembly  23  arranged on the free end  22   c   1  thereof. The thread holding assembly  23  includes a dish-shaped thread presser  23   a  which is mounted on the free end  22   c   1  of the arm  22   c  by a screw  23   c  with a coil spring  23   b  intervened therebetween. As a means for changing the position of the thread holder  22 , a toggle spring  24  is arranged between the movable plate  21  and the thread holder  22  such that the thread holder  22  may swing around the pivot  22   a  between a lower position as shown with solid line and a upper position shown with imaginary line as shown in  FIG. 3(   b ). The toggle spring  24  is shown as one of the examples which may be used. 
   With the combination of the constituent elements as mentioned above, the threading operation will now be described in reference to  FIGS. 5 through 8 . 
   As shown in  FIG. 5(   a ), the upper thread n which is guided by a thread guide  19   a  on a needle holder  19  is hanged to the thread hanger  4   f  of the threading member  4  and is then held by the thread holder  23  as extended across the needle axis on the front side of the machine needle  17 . As the operating lever  11  is moved down against the force of the coil spring  5 , the guide pin  3  which is in engagement with the inclined slot  9   a  of the movable guide  9  is moved down along the vertical guide groove  7  of the fixed guide member B and the threading bar  2  is, therefore, moved down. Then the protrusion  4   d  of the threading member  4  mounted to the lower end of the threading bar  2  is pressed against the horizontally flat surface  21   c  of the movable plate  21 , and the movable plate  21  is moved down against the force of the tension spring  25  to the lowest position K. 
   The downward movement of the guide pin  3  is stopped as the guide pin  3  comes to engage the stopper projection  13   a  of the positioning member  13 , and the threading bar  2  is stopped accordingly while the threading hook  14   b  of the threading member  4  is located at a level of the eye  17   a  of the machine needle  17 . In this case, the thread holding assembly  23  is located at a level that is lower than the needle eye  17   a . As the operating lever  11  is further moved down, the threading bar  2  is axially rotated by the guide pin  3  which is in engagement with the slot  9   a  of the movable guide  9 . With rotation of the threading bar  2 , the arm  4   a  of the threading member  4  is rotated accordingly, and the threading hook  4   b  is passed through the needle eye  17   a  of the machine needle  17  as shown in  FIGS. 6(   a ) through ( c ). 
   Immediately after the threading hook  4   b  is passed through the needle eye  17   a , the lateral projection  11   c  of the operating lever  11  is pressed against the engaging part  22   b  of the thread holder  22 . Then the thread holder  22  is rotated around the pivot  22   a  and the thread holding assembly  23  is jumped up axially of the machine needle  17  to the position slightly above the position of the needle eye  17   b  due to the jump up force of the toggle spring  24  which acts as a position setting means of the thread holding assembly  23  as shown in  FIGS. 7(   a ) and ( b ). 
   In this condition, the upper thread n is hanged to the threading hook  4   b  which is in the position as passed through the needle eye  17   b  as shown in  FIGS. 7(   c ) and ( d ). Subsequently when the operating lever  11  is released, the operating lever  11  is moved up by the coil spring  5 , and the threading bar  2  is moved up accordingly while the threading member  4  is rotated to retreat the threading hook  4   b  from the needle eye  17   a  as shown in  FIGS. 8(   a ) and ( b ). Thus the threading operation is finished. As the threading bar  2  is moved up, the movable member  21  is released and is moved up by the tension spring  25 . The thread holder  22  which is moved up with the movable member  21  is stopped by a projection or the like of the machine arm (not shown) engaging the arm  22   c  of the thread holder  22 ), and is rotated back to the inoperative position where the thread holding assembly  23  is located in the lower position. Incidentally in this embodiment the toggle spring  24  is used as a means for changing the position of the thread holder  22 . However the toggle spring  24  may be replaced with a rotary solenoid or a spring activated link mechanism.