Abstract:
A sewing machine includes a threader including a threading hook for passing a thread through an eye of a needle. The sewing machine includes a threader driver driving the threader so that the threading hook is advanced through or retreated through the eye of the needle. The sewing machine includes a thread drawer including a thread drawing member wiping the thread extending through the needle eye downward, the thread drawing member also drawing a looped thread having been passed through the needle eye by the threading hook. The sewing machine includes a thread drawer driver provided independent of the threader driver for moving the thread drawer so that the thread is wiped and a thread loop is released from a looped state. The sewing machine includes a control unit controlling the threader driver and the thread drawer driver.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a sewing machine in which a sewing thread can automatically be released from a thread loop formed when a sewing needle is threaded, a threading control program and a recording medium on which the threading control program is recorded.  
         [0003]     2. Description of the Related Art  
         [0004]     There have conventionally been proposed sewing machines provided with threading means for automatically threading a sewing needle. For example, JP-8-173676-A discloses a technique for catching a thread by a hook having been passed through an eye of the needle and returning the hook through the needle eye such that the needle thread is passed through the needle eye, while the thread is guided by thread guide grooves or the like and held by thread holders. JP-6-254279-A discloses thread drawing means for wiping a leading end of the cut thread off the cloth after a thread cutting operation such as in completion of sewing and introducing the thread end to an upper thread nipper.  
         [0005]     In the sewing machine disclosed in JP-8-173676-A, however, the thread having been passed through the needle eye forms a loop between the needle eye and the hook. The thread loop is drawn with fingers of an operator so that a free end side part of the thread is pulled back through the needle eye, whereby the needle is threaded. JP-51-24353-A discloses a first nipper holding a thread cut during the sewing and a second nipper catching the thread held by the first nipper. The thread caught by the second nipper is passed through the needle eye by a thread extruder. The thread having been passed through the needle eye is caught by a third nipper, which is then moved upward so that the thread is completely passed through the needle eye. In the disclosed sewing machine, however, three nippers are provided for catching and pulling back the thread through the needle eye. Moreover, since the three nippers are moved individually, the structure of the sewing machine is complicated.  
       SUMMARY OF THE INVENTION  
       [0006]     Therefore, an object of the present invention is to provide a sewing machine in which the thread can be released from the thread loop formed during the threading operation by thread drawing means so that the thread is passed through the needle eye and the structure of the sewing machine can be simplified.  
         [0007]     The present invention provides a sewing machine comprising a threader including a threading hook for passing a thread through an eye of a needle and a thread drawer including a thread drawing member wiping the thread extending through the needle eye downward, the thread drawing member also drawing a looped thread having been passed through the needle eye by the threading hook.  
         [0008]     The threading hook on which the operator has set the thread is pulled back through the needle eye, so that the thread is passed through the needle eye by the threading hook. The thread formed into a loop shape can be drawn by the thread drawing member of the thread drawer. Consequently, the thread can be passed through the needle eye so that the sewing can be initiated.  
         [0009]     In the above-described construction, it is preferred that when the looped thread is drawn by the thread drawing member, the thread drawer draws the thread to a position where the thread is released from a looped state.  
         [0010]     In another preferred form, a part of the thread between the needle and the threading hook is drawn by the thread drawing member while the threading hook in engagement with the thread is spaced away from the needle rearward.  
         [0011]     Furthermore, the sewing machine further comprises a thread holding member holding an end of the thread caught on the threading hook before the thread is passed through the needle eye. In this case, the thread drawing member is engaged with the thread after the thread has been released from a held state by means of the thread holding member, thereby drawing the thread.  
         [0012]     In further another preferred form, the thread drawing member draws a free end side of the looped thread formed by the threading hook. Furthermore, the thread drawing member preferably has a shorter distance of movement in a case of releasing the thread from the looped state than a distance of movement in a case of wiping the thread.  
         [0013]     In further another preferred form, the thread drawing member has a distal end positioned higher in a case of releasing the thread from the looped state than in a case of wiping the thread. Further, the thread drawing member releases the thread from the looped state in a middle of a movement locus thereof in a case of wiping the thread.  
         [0014]     Furthermore, the sewing machine is preferably a multi-needle sewing machine including a plurality of needle bars provided with needles respectively. Additionally, the thread drawing member preferably carries out a thread drawing operation while a distal end of the threading hook on which the thread is caught is located lower than the needle eye. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Other objects, features and advantages of the present invention will become clear upon reviewing the following description of the invention with reference to the accompanying drawings, in which:  
         [0016]      FIG. 1  is a perspective view of a multi-head sewing machine in accordance with one embodiment of the present invention;  
         [0017]      FIG. 2  is a front view of a needle bar case;  
         [0018]      FIG. 3  is a partial left side view of an embroidery sewing machine;  
         [0019]      FIG. 4  is a partial right side view of the embroidery sewing machine;  
         [0020]      FIG. 5  is a partial front view of the embroidery sewing machine;  
         [0021]      FIG. 6  is a partial plan view of the embroidery sewing machine;  
         [0022]      FIG. 7  is a right side view of the embroidery sewing machine, showing a stage of a threading operation;  
         [0023]      FIG. 8  is also a right side view of the embroidery sewing machine, showing another stage of the threading operation;  
         [0024]      FIG. 9  is a longitudinal section of a sewing needle and its periphery in the threaded state;  
         [0025]      FIG. 10  is a plan view of a sewing needle and its periphery in the threaded state;  
         [0026]      FIG. 11  is a plan view of the sewing needle and its periphery with a thread loop being formed;  
         [0027]      FIG. 12  is a schematic block diagram showing an electrical arrangement of a control unit; and  
         [0028]      FIG. 13  is a flowchart showing a threading control program. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     One embodiment of the present invention will be described with reference to the drawings. In the embodiment, the invention is applied to an industrial or occupational multi-head sewing machine including three multi-needle embroidery sewing machines which can embroider three same embroidery patterns on respective caps at the same time.  
         [0030]     The multi-head sewing machine M will first be described. Referring to  FIG. 1 , the multi-head sewing machine M comprises an embroidering machine body frame  1  extending in the right-and-left direction, and a generally rectangular machine support plate  2  mounted on the rear top of the frame  1  so as to extend in the right-and-left direction. Three multi-needle embroidery sewing machines M 1  to M 3  are mounted on the support plate  2  so as to be juxtaposed in the right-and-left direction. The embroidery sewing machines M 1  to M 3  have the same structure.  
         [0031]     Each of the embroidery sewing machines M 1  to M 3  includes an arm  3  having a distal end on which a sewing head  4  is mounted. The head  4  has a front end on which a needle bar case  5  is mounted so as to be moved in the right-and-left direction. Six needle bars  10  are supported on the needle bar case  5  so as to be vertically moved. A sewing needle  15  having a needle eye  15   a  is fixed to each needle bar  10 . A stud  6  is continuous to the arm  3  and has a lower end to which a sewing bed body  7  is continuous. The sewing bed body  7  is fixed to the machine support plate  2 . The sewing bed body  7  has a front end from which a cylinder bed  8  extends forward. The cylinder bed  8  has a front end on which a thread loop taker (not shown) and the like are provided. The multi-head sewing machine M includes an operation panel  9  disposed at the right end thereof. An operator operates the operation panel  9  to enter various commands.  
         [0032]     Referring now to  FIGS. 3 and 4 , each head  4  includes the needle bar case  5 , a lift driving mechanism  30  transmitting a vertically driving force from a sewing machine motor  110  to the needle bar  10  and a needle bar releasing mechanism  31  cutting off transmission of driving force between the needle bar  10  and the lift driving mechanism  30 . Each head  4  further includes a thread drawing mechanism  32  further including a thread drawing member  62  and a threading mechanism  33  passing a thread through an eye  15   a  of a sewing needle  15  by means of a threading hook  83 .  
         [0033]     Referring to  FIGS. 2 and 3 , each needle bar case  5  includes six vertically extending needle bars  10 , six needle thread take-up levers  11  located so as to correspond to the respective needle bars  10  and attached so as to be moved vertically. Each needle bar case  5  further includes first and second needle bar guiding members  12  and  13  both fixed to the needle bar case  5  to guide the needle bar  10  and a first thread holding member  14  extending in the right-and-left direction and supported on a fixing plate  17  having both ends secured to the needle bar case  5 . Each needle bar case  5  still further includes six second thread holding members  16  disposed so as to correspond to the respective needles  15  and six presser feet  24  disposed so as to correspond to the respective needles  15 .  
         [0034]     A connecting member  18  is secured to a middle portion of each needle bar  10 . The connecting member  18  includes a connecting pin  18   a  to which a driving force from the lift driving mechanism  30  is transmitted. A compression coil spring  19  is provided around the needle bar  10  between the connecting member  18  and the first needle bar guiding member  12 . The compression coil spring  19  biases the needle bar  10  upward. The needles  15  are attached to the lower ends of the respective needle bars  10 . An embroidering thread T is supplied from a thread spool  21  mounted on a spool holder base  20  to each of the six needles  15 .  
         [0035]     The first thread holding member  14  holds the thread T drawn by the thread drawing mechanism  32 . The first thread holding member  14  includes a thread holding tape  14   a  further including hook sides of two pieces of hook-type magic tape (registered trademark). The hook sides are superposed so as to confront each other. The first thread holding member  14  further includes a pair of reinforcing plates  14   b  holding the thread holding tape  14   a  therebetween.  
         [0036]     Each second thread holding member  16  preliminarily holds a leading end of the thread T caught on the threading hook  83  before the thread T is passed through the needle eye  15   a . The second thread holding member  16  includes a holding portion  16   a  holding the thread T cut by a blade  16   a  and a guiding portion  16  chaving a forwardly protruding distal end and guiding the thread T to the holding portion  16   a . The operator passes the thread T from the right side to the rear of the guiding portion  1   c . When guided to the blade  16   a , the thread T is drawn downwardly forward so that the thread T is cut by the blade  16   a  and held by the holding portion  16   b  and the front of the needle bar case  5  therebetween. Thus, the leading end of the thread T is held.  
         [0037]     Each needle bar case  5  is moved right and left so that a desired one of the needles  15  is switched into a sewing position corresponding to a needle hole (not shown) formed in the distal end of the cylinder bed  8 , whereby one of the needle bars  10  is selected. A rotating force developed by the motor  110  is transmitted via the driving shaft  22 , a V belt and the like to the lift driving mechanism  30  as a vertically driving force. The lift driving mechanism  30  is then driven vertically so that the needle bar  10  is vertically moved and accordingly, the corresponding needle thread take-up lever  11  is vertically swung. Further, stitches are formed using the thread T with a selected color by the cooperation of the needle  15  of the needle bar  10  and the thread loop taker.  
         [0038]     Referring now to  FIGS. 3, 5  and  6 , the lift driving mechanism  30  includes a base needle bar  35  disposed in parallel with the needle bar  10  and a driving member  36  mounted on the base needle bar  35  so as to be slidable and non-rotatable. The lift driving mechanism  30  further includes a transmitting member  37  mounted so as to be vertically driven together with the driving member  36  and so as to be rotatable relative to the base needle bar  35 . The lift driving mechanism  30  still further includes a first coil spring  38  having one of two ends abutting the driving member  36  and the other end abutting the transmitting member  37  so that the transmitting member  37  is biased to a transmitting position where the driving force is transmitted to the needle bar  10 .  
         [0039]     The driving member  36  includes upper and lower driving members  36   a  and  36   b  both fitted with the base needle bar  35  and a connecting portion  36   c  connecting the upper and lower driving members  36   a  and  36   b . A first coil spring  38  is fitted with the upper driving member  36   a . A stopper  39  is secured to a left side of the lower driving member  36   b . The stopper  39  limits rotation of the transmitting member  37  to a predetermined angle. The transmitting member  37  is disposed between the upper and lower driving members  36   a  and  36   b . The transmitting member  37  includes first and second engaging members  40  and  41  engaging the connecting pin  18   a  and an abutment pillar  42  to which a rotating force from the needle bar releasing mechanism  31  is transmitted in order that the needle bar  10  may be released. The first engaging member  40  includes an inclined portion  40   a  turning the transmitting member  37  in the direction of arrow A in  FIG. 6  when the connecting pin  18   a  in the released state abuts the first engaging member  40 .  
         [0040]     The needle bar releasing mechanism  31  includes a driving motor  46  mounted on the fixing member  45  and comprising a pulse motor and a sector gear  47  in mesh engagement with an output shaft  46   a  of the driving motor  46 . The needle bar releasing mechanism  31  further includes a guided plate  50  guided by guide pins  49   a  and  49   b  secured to the fixing member  48  so that the guided member is vertically moved. The needle bar releasing mechanism  31  still further includes a first linking member  51  having a lower end connected to a central portion of the guided plate  50  so that the lower end is swung and a second linking member  52  connected to an upper end of the first linking member  51  so as to be swung, an abutting member  53  swung with the second linking member  52  and a stopper  54  fixed to the fixing member  48 . The sector gear  47  has a front half further having a lower end abutting an abutment pin  55  secured to a lower end of the guided plate  50 . The fixing members  45  and  48  are fixed to a left-side sewing machine frame  56 .  
         [0041]     The abutting member  53  includes a shaft  53   a  rotatably mounted on the fixing member  48  and fixed to the second linking member  52  by a small screw  57 , a first abutting portion  53   b  abutting the abutment pillar  42  of the transmitting member  37  and a second abutting portion  53   c  abutting the stopper  54 . A second coil spring  59  is wound on a right end of the shaft  53   a . The second coil spring  59  has one end fixed to a screw  58  in thread engagement with the fixing member  48 . The abutting member  53  is biased in the direction of arrow C in  FIG. 3  by the second coil spring  59  except when the needle bar  10  is jumped, whereupon the second abutting portion  53   c  is in abutment with the stopper  54 .  
         [0042]     In order that the needle bar  10  may be jumped to be released by the needle bar releasing mechanism  31 , the driving motor  46  is driven so that the sector gear  47  is rotated in the direction of arrow Din  FIG. 3 , whereby the guided plate  50  is moved downward. The movement of the guided plate  50  further moves the lower end of the first linking member  51  downward. With the downward movement of the first linking member  51 , the second linking member  52  is rotated in the direction opposite arrow C about the shaft  53   a  together with the abutting member  53 . By the rotation, the abutting member  53  presses the abutment pillar  42  of the transmitting member  37  which is further in abutment with the first abutting portion  53   b , so that the transmitting member  37  is rotated in the direction of arrow A in  FIG. 6  until the abutment pillar  42  abuts the stopper  39  (see the abutment pillar  42  shown by two-dot chain line in  FIG. 6 ). As the result of rotation of the transmitting member  37 , the first and second engaging members  40  and  41  are released from engagement with the connecting pin  18   a . Consequently, the needle bar  10  is biased by the compression coil spring  19  thereby to be caused to jump to an upper limit position, whereby the needle bar  10  is in a released state in which a lifting force of the lift driving mechanism  30  is prevented from being transmitted to the needle bar  10 .  
         [0043]     On the other hand, in order that the needle bar  10  may be switched from the released state to a transmissible state in which the lift driving force of the lift driving mechanism  30  is transmissible to the needle bar  10 , the transmitting member  37  is moved upward by the sewing machine motor  110  so that the connecting pin  18   a  abuts the inclined portion  40   a  from above, whereby the transmitting member  37  is rotated in the direction of arrow A in  FIG. 6 . Further, when moved upward so that the connecting pin  18   a  is located between the first and second engaging members  40  and  41 , the transmitting member  37  is rotated in the direction of arrow B in  FIG. 6  by the biasing force of the coil spring  38 , whereby the connecting pin  18   a  engages the first and second engaging members  40  and  41  such that the needle bar  10  is in the transmissible state.  
         [0044]     The thread drawing mechanism  32  wipes the thread T extending downward through the needle eye  15   a  when the thread has been cut by a thread cutting mechanism (not shown) provided in the cylinder bed  8  at the time of completion of the sewing or needle change. The thread having been passed through the needle eye  15   a  and having a loop L is released from a looped state by the thread drawing mechanism  32  and caught on the threading hook  83 .  
         [0045]     Referring to  FIGS. 3, 5  and  6 , the thread drawing mechanism  32  includes the driving motor  46 , the sector gear  47  formed with a detected portion  60 , a thread drawing member origin detector  61  for detecting the detected portion  60 , and a thread drawing member  62 . The thread drawing mechanism  32  further includes a coupling plate  63  having both ends coupled to the thread drawing member  62  and the sector gear  47  respectively so that the coupling plate  63  is swung. The thread drawing mechanism  32  still further includes a guiding member  64  guiding the thread drawing member  62  and a cover  65  for the guiding member  64 . The thread drawing member  62  includes a standing portion  62   a  coupled to the coupling plate  63  so as to be swung and a hook  62   b  for drawing the thread T. The thread drawing member  62  is held between the guiding member  64  and the cover  65  and supported in a guide groove  64   a  formed in the guiding member  64  so that the thread drawing member  62  is slid. The origin detector  61  comprises a photo-interrupter including a light emitting element and a light detecting element. The origin detector  61  detects, as an origin, a position of the thread drawing member  62  when the lower edge of the detected portion  60  passes between the light emitting and detecting elements. The guide groove  64  guiding the thread drawing member  62  is formed so that the thread drawing member  62  is allowed to be moved rearward from a standby position as shown in  FIGS. 4 and 6  when the driving motor  46  is driven to rotate in the direction of arrow D in  FIG. 3  in order that the needle bar releasing mechanism  31  may be driven.  
         [0046]     In wiping the thread, the sector gear  47  to which the driving force is transmitted from the driving motor  46  is rotated in the direction of arrow E in  FIG. 3 . With the rotation of the motor  46 , the coupling plate  63  is moved downwardly forward so that the thread drawing member  62  coupled to the lower end of the coupling plate  63  passes through the first thread holding member  14  while being guided by the guide groove  64   a . Thus, the thread drawing member  62  is slid to the thread wiping position where the hook  62   b  is located below the needle  15 . The hook  62   b  is engaged with the thread T which extends downward after having been passed through the needle eye  15   a  (see two-dot chain line in  FIG. 3 ). When the thread drawing member  62  is returned to the standby position in the aforesaid state, the thread T in engagement with the thread drawing member  62  is held by the thread holding tape  14   a  of the first thread holding member  14  when passing through the first holding member  14 .  
         [0047]     Referring now to  FIGS. 4 and 5 , the threading mechanism  33  includes a threading motor  70  comprising a pulse motor, a rack  71  meshed with an output shaft  70   a  of the threading motor  70  and having a guide groove  71   a  which is engaged with guide pins  72   a  and  72   b  fixed to the right machine frame  73 , and an extension spring  76  having two ends. One end of the extension spring  76  is connected to a connecting pin  74  fixed to a lower end of the rack  71  and the other end of the extension spring  76  is connected to a connecting protrusion  75  fixed to a guide frame  77 . As a result, the extension spring  76  biases the rack  71  upward. The threading mechanism  33  further includes the guide frame  77  fixed to the right machine frame  73  and formed with a guide groove  77   a , a crank plate  78  located on the right of the guide frame  77  and connected via the connecting pin  74  to a lower end of the rack  71 , and a link block  80  formed into the shape of a rectangular parallelepiped. A first guided pin  79  is engaged with a guide groove  77   a  formed in a lower end of the crank plate  78 . The link block  80  is connected via the first guided pin  79  to a left side of the guide frame  77  so as to be moved. The threading mechanism  33  still further includes a pair of right and left thread catching members  81  and  82  fixed to a distal end of the link block  80  and having inclined portions  81   a  and  82   a  both guiding the thread T to the threading hook  83 . The threading hook  83  has a hook  83   a  on which the thread T held between the thread catching members  81  and  82  is caught. A threading hook detector  111  (see  FIG. 12 ) detects a position of the threading hook  83 .  
         [0048]     A second guided pin  84  engaged with the guide groove  77   a  is fixed to a middle portion of the link block  80 . The guide groove  77   a  includes an inclined portion  77   b  and a horizontal portion  77   c . In the threading operation, the link block  80  is firstly guided downwardly forward and horizontally forward subsequently.  
         [0049]     A threading operation by the thread drawing mechanism  32  and the threading mechanism  33  will now be described.  FIG. 7  illustrates the threading hook  83  and the thread drawing member  62  both of which are in the standby state. In this state, the threading motor  70  is driven to move the rack  71  downward while the rack  71  is being guided by the guide pins  72   a  and  72   b . As a result, the crank plate  78  connected to the rack  71  and the link block  80  connected to the crank plate  78  are firstly moved downwardly forward along the inclined portion  77   b  of the guide groove  77   a  and subsequently horizontally forward along the horizontal portion  77   c . Further, the link block  80  is moved so that the hook portion  83   a  of the threading hook  83  passes through the needle eye  15   a  as shown in  FIGS. 4 and 9 . The link block  80  is stopped at a thread catching position where the second guided pin  84  abuts the front end of the guide groove  77   a.    
         [0050]     Referring to  FIGS. 2 and 4 , the operator sets the thread T guided by the thread guides  85  and  86  and the like, on the thread catching members  81  and  82  from the right side. The thread T is then cut by the blade  16   a  of the second thread holding member  16 . A free end of the thread T is held between the holding portion  16   b  and front face of the needle bar case  5 , whereby the thread T is held. In this case, when the operator upwardly draws the thread T caught on the thread catching members  81  and  82 , the thread T is guided to the threading hook  83  by the inclined portions  81   a  and  82   a  of the respective thread catching members  81  and  82  to be caught on the hook portion  83   a , as shown in  FIGS. 9 and 10 .  
         [0051]     Subsequently, the threading motor  70  is driven to move the threading hook  83  rearward by a predetermined distance. The threading hook  83  is stopped at a thread releasing position located in the rear of the needle  15 . The driving motor  46  is then driven to move the hook portion  62   b  of the thread drawing member  62  through a thread loop L to a thread drawing position located lower than the loop L on the same locus as that in the thread wiping operation, so that the free end side F of the thread loop L is engaged with the hook portion  62   b , as shown in  FIG. 8 . This thread drawing position is located higher than the thread wiping position and a distance of the hook portion  62   b  moved is shorter than that in the thread wiping. In this case, the free end of the thread T held by the second thread holding member  16  is released such that the thread T is loosened, and the thread loop L is in engagement with the threading hook  83 . Accordingly, the width of the thread loop L in the right-and-left direction is increased without the thread loop hanging down between the threading hook  83  and the needle eye  15   a , as shown in  FIG. 11 . Further, since the hook  83   a  is located lower than the needle eye  15   a , the thread loop L is substantially perpendicular to the thread drawing member  62 , as shown in  FIG. 8 . Consequently, the thread drawing member  62  can reliably be passed through the loop L and engaged with the thread T.  
         [0052]     Subsequently, when the thread drawing member  62  is returned to the standby position by the driving motor  46 , the free end side F of the thread loop L held between the threading hook  83  and the needle eye  15   a  is drawn so that the thread loop L is pulled back through the needle eye  15   a  and disengaged from the threading hook  83 . Consequently, the thread T forming the loop L is released from the looped state. Further, the thread T is held by the thread holding tape  14   a  of the first thread holding member  14  when the thread drawing member  62  passes the first thread holding member  14  while drawing the free end side F of the thread T. Thus, the thread T is completely passed through the needle eye  15   a . Subsequently, the threading motor  70  is driven to return the threading hook  83  to the standby position, whereby the threading operation is completed.  
         [0053]     On the other hand, the operation panel  9  is operated so that various commands concerning the sewing or the like are supplied. The operation panel  9  includes a display  90 , input means  91  including a threading switch  92  (see  FIG. 12 ) and a flexible disc drive (FDD)  93 . The threading switch  92  is operated so that a command for operating the threading mechanism  33  is supplied and so that a command for operating the thread drawing mechanism  32  releasing the thread with the loop L from the looped state.  
         [0054]     A control unit  100  including a computer  101  will be described with reference to  FIG. 12 . The control unit  100  controls overall sections and mechanisms of the embroidery sewing machines M 3  to M 3  including the threading mechanism  33  and the thread drawing mechanism  32 . The control unit  100  includes the computer  101  further including CPU  102 , ROM  103 , RAM  104  and buses  105  connecting these devices. The control unit  100  further includes an input/output interface  106  for input into and output from the computer  101 , a drive circuit  107  connected to the input/output interface  106  to drive the sewing machine motor  110 , a drive circuit  108  for the driving motor  46  and a drive circuit  109  for the threading motor  70 .  
         [0055]     To the input/output interface  106  are connected the thread drawing member origin detector  61  detecting the position of the thread drawing member  62  and the threading hook detector  111  detecting the position of the threading hook  83 . ROM  103  stores a threading control program for driving the motors  46  and  70  so that a threading operation is carried out. RAM  104  stores various data such as position data received from the thread drawing member origin detector  61  and the threading hook detector  111 .  
         [0056]      FIG. 13  is a flowchart showing the threading control program executed by the computer  101  of the control unit  100  in order that a thread T may be passed through the eye  15   a  of the needle  15 . The threading control program will now be described. Reference symbol Si (where i=10, 11, . . . ) designates an operation step.  
         [0057]     The operator operates the threading switch  92  of the operation, panel  9  to enter a command (step S 10 ). The computer  101  delivers a command to the drive circuit  109  when the sewing machine is in the sewing stop state (YES at step S 1 ). As a result, the threading hook  83  is driven by the threading motor  70 , so that the threading hook  83  is moved toward the threading position while the position of the threading hook  83  is being detected by the threading hook detector  111  (step S 12 ). When the threading hook  83  has been moved to the threading position (YES at step  513 ), the threading motor  70  is stopped in a state where the threading hook  83  has been passed through the needle eye  15   a  (step S 14 ).  
         [0058]     Subsequently, when the thread T is caught on the thread hook  83  and the threading switch  92  is then re-operated so that a command is supplied (YES at step S 15 ), the computer  101  supplies a command to the drive circuit  109  in response to the command from the threading switch  92 . As a result, the threading motor  70  is driven so that the threading hook  83  is moved backward through the needle eye  15   a  toward the thread releasing position while the position of the threading hook  83  is being detected by the threading hook detector  111  (step S 16 ). When the threading hook  83  has reached the thread releasing position after movement by a predetermined distance (YES at step S 17 ), threading the needle  15  is then carried out and the threading motor  70  is stopped (step S 18 ).  
         [0059]     Subsequently, when the computer  101  delivers a command to the drive circuit  108 , the drive motor  46  is driven to rotate the sector gear  47  in the direction of arrow E in  FIG. 3  so that the thread drawing member  62  is moved toward the origin (step S 19 ). Thereafter, when the origin of the thread drawing member  62  has been detected by the origin detector  61  (YES at step S 20 ), a predetermined number of pulses is supplied to the drive motor  46  at the origin so that the thread drawing member  62  is moved to the thread drawing position (step S 21 ). Consequently, the free end side F of the thread loop L extending from the hook  83  to the needle eye  15   a  is engaged with the hook  62   b  of the thread drawing member  62  and thereafter, the drive motor  40  is stopped. In this case, the drive motor  46  is driven in the opposite direction so that the thread drawing member  62  with which the thread loop L is in engagement is returned to the standby position, whereupon the thread T is released from the looped state (step S 22 ) and the threading motor  70  is driven to move the threading hook  83  to the standby position and subsequently, the threading control program is finished.  
         [0060]     The following effects can be achieved from the above-described multi-head sewing machine M. The multi-head sewing machine is constructed so that the thread drawing member  62  of the thread wiper  32  for wiping the thread in the thread change or the like is moved to the thread drawing position, whereby the thread with the loop L between the needle eye  15   a  and the threading hook  83  in the threading operation is released from the looped state. Consequently, the number of parts of the multi-head sewing machine M is reduced such that the structure thereof can be simplified. Further, the production cost of the multi-head sewing machine M can be reduced, whereas the thread T can reliably be passed through the needle eye  15   a . Accordingly, useless labor by the operator and a useless working time can be reduced.  
         [0061]     Furthermore, when the thread drawing member  62  engages the thread loop L, the thread loop L is held between the needle eye  15   a  and the threading hook  83  without hanging downward. Additionally, since the distal end of the threading hook  63  is located lower than the needle eye  15   a , the thread drawing member  62  becomes almost perpendicular to the thread loop L. Further, the thread drawing member  62  passes through the thread loop L while the thread T is released from the holding by the second thread holding member  16  such that the thread loop L is loosened into a spread state. Consequently, the thread drawing member  62  can reliably engage the thread loop L.  
         [0062]     Furthermore, since the thread drawing member  62  engages and draws the free end side F of the thread loop L, the thread T can smoothly be pulled out through the needle eye  15   a  without uselessly drawing out the thread from the thread spool  21 .  
         [0063]     Furthermore, the distance by which the thread drawing member  62  is moved for release of the thread is shorter than that thereof for thread wiping. Further, the thread drawing position is located higher than the thread wiping position, the size of the drive motor  46  need not be increased for the purpose of release of the thread loop L. Additionally, the thread drawing member  62  is moved in the release of the looped thread along the same movement locus as in the thread wiping. Consequently, the structure of the multi-head sewing machine M can be simplified since no complicated mechanisms are required which moves the thread drawing member  62  along a complicated movement locus for the release of the thread T from the threaded loop L.  
         [0064]     Modified forms of the foregoing embodiment will now be described. In the foregoing embodiment, the present invention is applied to the embroidery sewing machines M 1  to M 3  each of which is provided with the needle bar case  5  in which a plurality of needles  15  and needle bars  10  are mounted on the single head  4 . However, the invention may be applied to a sewing machine comprising a single head provided with a single sewing needle.  
         [0065]     The invention is applied to the multi-head sewing machine M composed of three embroidery sewing machines M 1  to M 3  in the foregoing embodiment. However, the invention may be applied to a single-head sewing machine composed of a single sewing machine. Further, the invention is applied to the industrial or occupational multi-head sewing machine M in the foregoing embodiment. However, the invention may be applied to a household sewing machine for personal use.  
         [0066]     The lift driving mechanism  30  and the driving force transmitting means are inseparable from the cloth moving mechanism in the foregoing embodiment. However, the cloth moving mechanism may be separable from the lift driving mechanism  30  and the driving force transmitting means as disclosed in Japanese Patent No. 3178022.  
         [0067]     In the foregoing embodiment, the threading hook  83  and the thread drawing member  62  are located in the rear of the needle  15 . However, either one or both of the threading hook and thread drawing member may be disposed in front of the needle or side by side.  
         [0068]     In the foregoing embodiment, the thread drawing member  62  passes through the thread loop L and then engages the thread T while the threading hook  83  and the thread T are in engagement with each other. However, the thread drawing member  62  may engage the thread loop while the threading hook and the thread are disengaged from each other.  
         [0069]     The thread T is held between the thread holding tapes  14   a  of the first thread holding member  14  in the foregoing embodiment. However, unless the thread is inadvertently moved or if the thread can be released from the holding by the first thread holding member upon sewing, the thread may merely be placed on a member thereby to be held. Further, upon start of sewing, the thread T is drawn by the needle  15  without operation of the first thread holding member  14 , so that the thread T is released from the held state. However, the first thread holder may comprise an actuator so that the thread is released in a positive manner, instead.  
         [0070]     The thread drawing member  62  is reciprocally moved along a linear passage in the foregoing embodiment. However, the thread drawing member may reciprocally be moved along an arc passage or may be moved in one way along a passage. In the foregoing embodiment, the distance by which the thread drawing member  62  is moved for release of the thread loop L is shorter than that thereof for thread wiping. However, the thread drawing member  62  is moved along a linear passage both for the release of the thread loop L and for thread wiping. Two linear passages may be provided both for the release of the thread loop L and for thread wiping respectively.  
         [0071]     In the foregoing embodiment, the invention is applied to the multi-head sewing machine M in which the operator is located in front of the sewing machine in the sewing as viewed in  FIG. 1 . However, the invention may be applied to a single-head sewing machine or the like in which the operator is located on the right or left of the sewing machine. Since the position of the operator changes in this sewing machine, it is desirable that the threading hook and the thread drawing member a removed along a track differing from the one in the foregoing embodiment, for example, so that the tracks of the threading hook and the thread drawing member are moved toward the operator.  
         [0072]     An article to be sewn is moved by a cylindrical cap frame in the above-described multi-head sewing machine M. However, the invention may be applied to a sewing machine in which an article to be sewn is moved by a flat embroidery frame. Further, the invention may be applied to a sewing machine which is not provided with any embroidery frame and an article to be sewn is moved by a feed dog, by a feed roller or manually.  
         [0073]     The free end side F of the thread loop L is located on the left of the needle  15  in the foregoing embodiment as shown in  FIG. 11 . Accordingly, the hook  62   b  of the thread drawing member  62  is open to the left side. However, the free end side of the thread loop may be located on the right of the needle so that the hook of the thread drawing member is open to the right side, instead.  
         [0074]     The pulse motor is used as the drive motor  46  in the foregoing embodiment. Another type of motor, a solenoid or an air cylinder may be used as the drive motor, instead. Further, a recording medium on which the threading control program is recorded should not be limited to ROM. A flexible disc or a CD-ROM may serve as the recording medium. Additionally, the above-described multi-head sewing machine M includes the sewing bed  7  having a cylinder bed  8 . However, the sewing bed may have a flat bed.  
         [0075]     The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limiting sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the invention as defined by the appended claims