Patent Publication Number: US-7905190-B2

Title: Sewing machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-39095 filed on Feb. 16, 2006, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a sewing machine provided with a thread wiper which is actuated for securement of an amount of thread immediately before the cutting of a needle thread by a thread cutting mechanism so that a predetermined amount of needle thread located downstream relative to a needle eye of a sewing needle is secured. 
     2. Description of the Related Art 
     When workpiece cloth is sewn by various types of sewing machines, it has been conventionally ideal that a needle thread is prevented from dropping out of a needle eye and moreover, an end of the needle thread is prevented from remaining on an upper side of the workpiece cloth. Various types of sewing machines have been proposed which prevent the needle thread from dropping out of the needle eye or the end of the needle thread from remaining at the upper side of the workpiece cloth. 
     JP-A-2004-290293 discloses a sewing machine including a picker for retaining a needle thread. The picker is provided in front of a rotary hook provided in a front end of interior of a cylinder bed. The picker is pivotable over a needle thread retaining position, a standby position and a retreated position. The picker is designed to be switchable so as to be moved to the three positions via a linking member coupled to a picker driving motor. In the disclosed sewing machine, the picker is switched to the needle thread retaining position when the needle thread is cut. As a result, the needle thread engages the picker so that a predetermined amount of remaining thread can be secured. 
     JP-A-H08-57181 discloses a thread cutter for sewing machines including a movable cutting blade which is moved from a standby position to a pivot position (a first half of reciprocal movement) in cutting a thread so that a needle thread and a bobbin thread at the workpiece cloth side engage the movable cutting blade. The timing of returning movement of the cutting blade (a second half of the reciprocal movement) is changed in synchronization with rise of a thread take-up, that is, retarded so that an amount of remaining needle thread after thread cutting is adjustable, whereupon no picker is necessitated. 
     In the sewing machine disclosed by JP-A-2004-290293, however, the front end of the cylinder bed is extended to the distal end side since the picker is disposed in front of the rotary hook. Accordingly, the distance from the sewing needle to the cylinder bed is increased, whereupon a sewable area is narrowed in the cross direction in the case where an embroidery is sewn on a cap. Furthermore, since the picker driving motor is necessitated as well as the picker and the linking member, the size of the cylinder bed is increased. The production cost of the sewing machine is increased since the number of components is increased. 
     Additionally, although no picker is necessitated in the thread cutter disclosed by JP-A-H08-57181, an amount of remaining needle thread depends upon the synchronization of rise of the thread take-up with the timing of the second half of reciprocation of the cutter blade. As a result, an amount of remaining needle thread tends to be adversely affected by the material of workpiece cloth or needle thread. 
     SUMMARY 
     Therefore, an object of the present disclosure is to provide a sewing machine in which no picker is necessitated such that the size of the cylinder bed can be reduced and a sewable range can be increased and a necessary amount of needle thread remaining after thread cutting can be secured reliably and accurately. 
     The present disclosure provides a sewing machine comprising a thread take-up; a thread take-up driving mechanism which drives the thread take-up; a sewing machine motor which drives the thread take-up driving mechanism; a thread cutting mechanism including a fixed cutting blade and a movable cutting blade both of which cut the needle thread and a movable cutting blade driving mechanism which drives the movable cutting blade; a thread wiper which wipes the cut needle thread away over workpiece cloth to be sewn; a wiper driving mechanism which drives the thread wiper; a thread tension adjuster which adjusts a tension of the needle thread; a thread tension adjuster driving mechanism which drives the thread tension adjuster; and a control device coupled to the sewing machine motor, the thread cutting mechanism, the wiper driving mechanism and the thread tension adjuster driving mechanism, wherein the control device is configured to execute a needle thread cutting operation including driving the movable cutting blade to a predetermined pivot location (S 12 ); driving the wiper driving mechanism for protruding the wiper by a predetermined stroke (S 17 ); driving the thread take-up driving mechanism to lower the thread take-up by a predetermined distance (S 18 ); driving the wiper driving mechanism to draw back the wiper by a predetermined amount corresponding to the lowering of the thread take-up (S 19 ); driving the movable cutting blade to a standby position (S 21 ); driving the thread tension adjusting mechanism to release the thread tension adjusting mechanism (S 23 ); and driving the thread take-up driving mechanism to move the thread take-up to an original uppermost position (S 24 ). 
     According to the above-described arrangement, the control device firstly controls the movable cutting blade driving mechanism when receiving a needle thread cutting command upon end of a sewing process. In the state previous to cutting of the needle thread where the needle thread is caught by the movable cutting blade, the control device controls the wiper driving mechanism so that the distal end of the thread wiper engages the needle thread and then so that the wiper driving mechanism is operated for securement of the predetermined amount of needle thread. In this case, the predetermined amount of needle thread located downstream relative to the needle eye of the sewing needle is secured by the thread wiper. Thus, the predetermined extra amount of needle thread is secured. In this state, the control device controls the movable cutting blade driving mechanism so that the needle thread is cut by the movable cutting blade. Consequently, an amount of remaining needle thread after cutting can be increased according to an amount of operation of the wiper for securement of thread amount. 
     In the above-described case, an extra amount of remaining needle thread after cutting thereof can be secured by the thread amount securing operation of the thread wiper without picker nor picker driving motor provided in the cylinder bed. Consequently, the production cost can be reduced as the result of a reduction in the number of components, and the size of the cylinder bed can be reduced. Furthermore, a necessary amount of remaining needle thread after thread cutting can be secured reliably and accurately. Additionally, since no picker is necessitated, the distance between a rotary hook and the front end of the cylinder bed can be shortened. Consequently, a sewable area can be enlarged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the embodiment with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a whole multi-needle embroidery machine of one embodiment in accordance with the present disclosure; 
         FIG. 2  is a front view of a needle bar case; 
         FIG. 3  is a partial longitudinally sectional left side view of the needle bar case; 
         FIG. 4  is a partial enlarged side view of the needle bar case as shown in  FIG. 3 ; 
         FIG. 5  is a partial front view of the interior of the needle bar case; 
         FIG. 6  is a partial plan view of the interior of the needle bar case; 
         FIG. 7  is a plan view of a thread cutting mechanism; 
         FIG. 8  is a block diagram showing a control system of the multi-needle embroidery machine; 
         FIGS. 9A and 9B  are flowcharts showing the thread cutting control; and 
         FIG. 10  is a view similar to  FIG. 3 , showing the case where a thread amount securing operation has been carried out by a wiper. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     One embodiment of the present disclosure will be described with reference to the accompanying drawings. The disclosure is applied to a multi-needle embroidery machine in the embodiment. 
     Referring to  FIG. 1 , the multi-needle embroidery machine M of the embodiment is shown. The multi-needle embroidery machine M includes a pair of left and right support legs  1 , a pillar  2  standing from rear ends of the support legs  1 , an arm  3  extending frontward from an upper end of the pillar  2 , a needle bar case  5  which is mounted on a head  4  which is a distal end of the arm  3  so as to be movable horizontally, a cylinder bed  6  extending frontward from a lower end of the pillar  2 , a frame moving mechanism (not shown) which moves a carriage  7  and accordingly an embroidery frame (not shown) mounted on the carriage  7  in the X-direction and the Y-direction perpendicular to the X-direction and the like. The description of the frame moving mechanism will be eliminated. 
     In the head  4  are provided a needle bar driving mechanism  30  selectively transmitting a vertical driving force to one of a plurality of needle bars  10  provided in the needle bar case  5 , a needle bar releasing mechanism  31  which intermits transmission of the driving force of the needle bar driving mechanism  30  and a wiper driving mechanism  32  driving a thread wiper  62  for a wiping operation. 
     On a front end of the cylinder bed  6  are mounted a thread cutting mechanism  33  (see  FIG. 7 ) for cutting a needle thread  28  and a bobbin thread, a rotary hook  6 A (see  FIG. 3 ) and the like. When a needle bar changeover motor  83  (see  FIG. 8 ) is driven at the time of embroidery thread change, the needle bar case  5  is horizontally moved so that the needle bar driving mechanism  30  corresponds to one of the needle bars  10 . 
     The needle bar case  5  is provided with six needle bars  10  extending vertically, six thread take-ups  11  which are swingably mounted on the needle bar case  5  at locations corresponding to the needle bars  10  respectively, a first needle bar guiding member  12  and a second needle bar guiding member  13  both fixed to the needle bar case  5  to guide the needle bars  10 , a horizontally extending first thread retaining member  14  supported on both ends of a fixed plate  17  secured to the needle bar case  5 , six second thread retaining members  16  which are provided so as to correspond to sewing needles  15  mounted on lower ends of the needle bars  10  respectively, a presser foot  21  and the like. 
     A tension guide  8  is formed integrally on an upper end of the needle bar case  5  and provided with six thread tension adjusting mechanisms  9  as shown in  FIG. 3 . Each thread tension adjusting mechanism  9  includes a thread tension adjusting knob  9   a  which adjusts a resilient biasing force pressing a movable disc against a fixed disc, neither disc being shown. Each thread tension adjusting mechanism  9  is constructed so that the needle thread  28  is held between the movable and fixed discs so as to be tensioned. A thread tension disc opening solenoid  85  (shown only in  FIG. 8 ) is provided in each thread tension adjusting mechanism  9  so as to be located in the needle bar case  5 . When each thread tension disc opening solenoid  85  is operated, the movable disc is slightly moved away from the fixed disc such that the thread tension adjusting mechanism  9  is released, whereupon the needle thread  28  is not tensioned. 
     A coupling member  18  is secured to a vertically middle part of each needle bar  10 . The coupling member  18  has a coupling pin  18   a  to which is transmitted a drive force from the needle bar driving mechanism  30 . A compression coil spring  19  (see  FIG. 4 ) is provided about each needle bar  10  between the coupling member  18  and the first needle bar guiding member  12 . The compression coil spring  19  upwardly biases the needle bar  10 . Six sewing needles  15  are attached to lower ends of the needle bars  10  respectively. Embroidering needle threads  28  are supplied from thread spools (not shown) provided on an upper part of the arm  3  to the needles  15  respectively. The first thread retaining member  14  is provided for retaining the needle thread  28  drawn up by the thread wiper  62 . The first thread retaining member  14  has a hook-shaped thread retaining tape  14   a  and reinforcement plates  14   b  holding the tape  14   a  therebetween. 
     The needle bar case  5  is moved right and left by a needle bar changeover motor  83  so that one of the sewing needles  15  is switched to a sewing location opposed to a needle hole (not shown) of a distal end of the cylinder bed  6 . As a result, the drive force of the sewing machine motor  81  is transmitted through a sewing machine main shaft to the needle bar driving mechanism  30  so that the needle bar  10  selected by the vertical drive of the needle bar driving mechanism  30  is driven up and down, forming stitches on workpiece cloth in cooperation of the needle  15  and the rotary hook  6 A. 
     The following will describe a thread take-up driving mechanism  22  vertically driving the thread take-up  11 . The thread take-up  11  is mounted on a support shaft  23  so as to be vertically swingable as shown in  FIG. 3 . A thread take-up swinging lever  25  is secured to a thread take-up swinging shaft  24  which is caused to pivot by rotation of the sewing machine main shaft. The swinging lever  25  has a distal end on which a rolling member  26  engages a bifurcated part  11   a  of the thread take-up  11 . Accordingly, when sewing is carried out, the thread take-up  11  is reciprocally driven vertically via the swinging shaft  24  and the swinging lever  25 . 
     Next, the needle bar driving mechanism  30  will be described. Referring to  FIGS. 4 to 6 , the needle bar driving mechanism  30  comprises a base needle bar  35  provided in parallel with the needle bar  10 , a driving member  36  mounted on the base needle bar  35  so as to be slidable and non-rotatable, a transmitting member  37  mounted together with the driving member  36  so as to be capable of being vertically driven and so as to be rotatable relative to the base needle bar  35  and a first helical spring  38  (see  FIG. 5 ) having one end abutting the driving member  36  and the other end abutting the transmitting member  37  thereby to bias the transmitting member  37  to a transmitting location where the transmitting member  37  is capable of transmitting a drive force. 
     The driving member  36  has upper and lower driving members  36   a  and  36   b  both fitted with the base needle bar  35  and a connecting member  36   c  connecting the driving members  36   a  and  36   b  to each other. A first coil spring  38  is provided about the upper driving member  36   a . A stopper  39  is secured to a left side surface of the lower driving member  36   b  in order to limit rotation of the transmitting member  37  to a predetermined angle. The transmitting member  37  is mounted between the upper and lower driving members  36   a  and  36   b . The transmitting member  37  has first and second engagement members  40  and  41  each of which engages the coupling pin  18   a , and an abutment pillar  42  to which a rotating force is transmitted so that the needle bar  10  is released by the needle bar releasing mechanism  31 . The first engagement member  40  has an inclined part  40   a  (see  FIG. 5 ) which is provided for rotating the transmitting member  37  in the direction of arrow A in  FIG. 6  when the inclined part  18   a  in the released state abuts the first engagement member  40 . 
     The needle bar releasing mechanism  31  will be described. The needle bar releasing mechanism  31  includes a drive motor  46  comprising a pulse motor and mounted on a fixing member  45 , a sector gear brought into mesh engagement with a driving gear  46   a  secured to an output shaft of the drive motor  46 , a guided plate  50  which is guided by guide pins  49   a  and  49   b  both secured to the fixing member  48  so as to be vertically movable, a first linking member  51  having a lower end swingably coupled to a central part of the guided plate  50 , a second linking member  52  swingably coupled to an upper end of the first linking member  51 , an abutting member  53  swinging together with the second linking member  52  and a stopper  54  fixed to the fixing member  48 . 
     A front half of the sector gear  47  has a lower end which is in abutment with an abutment pin  55  secured to the lower end of the guided plate  50 . The fixing members  45  and  48  are fixed to predetermined positions on the left sewing machine frame  56  respectively. The abutting member  53  has a shaft  53   a  pivotally mounted on the fixing member  48  and fixed to the second linking member  52  by a screw  57 , a first abutting part  53   b  abutting the abutment pillar  42  of the transmitting member  37  and a second abutting part  53   c  abutting the stopper  54 . A second helical spring  59  is fitted with a right end of the shaft  53   a . The second helical spring  59  has one end fixed to a screw  58  in threading engagement with the fixing member  48 . The abutting member  53  is biased in the direction of arrow C in  FIG. 4  by the second helical spring  59  except when releasing the needle bar  10 . The second abutting part  53   c  is in abutment with the stopper  54 . 
     When the needle bar  10  is to be released by the needle bar releasing mechanism  31 , the drive motor  46  is driven so that the sector gear  47  is caused to pivot in the direction of arrow D in  FIG. 4  to move the guided plate  50  downward. The lower end of the first linking member  51  is moved downward as the result of movement of the guided plate  50 . With the movement of the first linking member  51 , the second linking member  52  is rotated about the shaft center of the shaft  53   a  in the direction opposite arrow C together with the abutting member  53 . Since the abutting member  53  presses the abutment pillar  42  of the transmitting member  37  in abutment with a first abutting part  53   b , 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 ). The first and second engaging members  40  and  41  are disengaged from the coupling pin  18   a  as the result of the rotation of the transmitting member  37 . Accordingly, the needle bar  10  is moved to an uppermost position by the biasing force of the compression coil spring  19 . In this released state, the raising and lowering drive force of the needle bar driving mechanism  30  is not transmitted to the needle bar  10 . 
     The following will describe the case where the needle bar  10  is switched from the aforesaid released state to a transmissible state where the raising and lowering drive force of the needle bar driving mechanism  30  is transmissible to the needle bar  10 . Firstly, the transmitting member  37  is driven upward by the sewing machine motor  81  so that the coupling pin  18   a  is caused to abut against the inclined part  40   a  from above, whereupon the transmitting member  37  is rotated in the direction of arrow A in  FIG. 6 . Consequently, the transmitting member  37  is moved upward such that the coupling pin  18   a  is located between the first and second engagement members  40  and  41 . Accordingly, the biasing force of the helical spring  38  rotates the transmitting member  37  in the direction of arrow B in  FIG. 6 , so that the coupling pin  18   a  engages the first and second engagement members  40  and  41  thereby to be coupled to the needle bar  10  so that the needle bar  10  is vertically movable. 
     A wiper driving mechanism  32  moves the thread wiper  62  forward and then draw the thread wiper  62  back when a thread of jump stitch is cut, a thread is changed to another or a thread is cut at the end of sewing, whereby the needle thread  28  extending downward through an eye  15   a  of the needle  15  is hooked on the distal end of the thread wiper  62  to be wiped away. In the embodiment, however, the thread wiper  62  is designed to carry out a thread amount securing operation so that a predetermined amount of needle thread  28  located downstream relative to the needle eye  15   a  of the needle  15  may be secured. As shown in  FIGS. 3 to 6 , the wiper driving mechanism  32  includes the drive motor  46  commonly used to drive the needle bar releasing mechanism  31 , a sector gear  47  formed with a detected part  60 , a wiper origin detector  61  which detects an origin of a wiper  62 , the wiper  62 , a coupling plate  63  having both ends swingably coupled to the wiper  62  and the sector gear  47 , a guide member  64  guiding the wiper  62  and a cover member  65  of the guide member  64 . 
     The thread wiper  62  has a coupling wall  62   a  swingably coupled to the coupling plate  63  and a hook  62   b  provided for drawing up the needle thread  28 . The thread wiper  62  is held between the guide member  64  and the cover member  65  so as to be slidable along a guide groove  64   a  formed in the guide member  64 . The guide groove  64  guiding the thread wiper  62  is constructed to be capable of moving the thread wiper  62  rearward from a standby position when the drive motor  46  is driven to cause the sector gear  47  to pivot in the direction of arrow D as shown in  FIGS. 4 and 6 . The wiper origin detector  61  comprises a photointerrupter provided with a light receiving device and a light emitting device. The wiper origin detector  61  detects, as an origin, a position of the thread wiper  62  in the case where a lower edge of the detected part  60  passes between the light receiving device and the light emitting device. 
     In the thread wiping, the drive motor  46  is driven so as to be rotated in a predetermined direction so that the sector gear  47  is rotated in the direction of arrow E in  FIG. 4 . Since the coupling plate  63  is moved forward with the rotation of the sector gear  47 , the thread wiper  62  coupled to the lower end of the coupling plate  63  passes through the first thread retaining member  14  while being guided along the guide groove  64   a , thereby moving forward by a predetermined stroke. At this time, since the hook  62   b  of the thread wiper  62  is moved to a thread wiping position below the needle  15 , the hook  62   b  engages the needle thread  28  located downstream relative to the needle eye  15   a  (see two-dot chain line as shown in  FIG. 2 ). In this state, when the drive motor  46  is driven so as to be reverse rotated, the thread wiper  62  is returned to the stand-by position via the sector gear  47  and the coupling plate  63 . At this time, the needle thread  28  in engagement with the hook  62   b  of the thread wiper  62  is wiped away over the workpiece cloth to be retained by the thread retaining tape  14   a  of the first thread retaining member  14 . 
     Next, the thread cutting mechanism  33  provided on the cylinder bed  6  will be described. As shown in  FIG. 7 , a fixing plate (not shown) secured to the cylinder bed  6  is provided at the upper side of the rotary hook  6 A, and a movable cutting blade  70  is pivotally mounted on a support pin  71  secured to the fixing plate. Furthermore, an operating lever  72  extending in the cross direction has a front end coupled to the movable cutting blade  70  and a rear end coupled to a movable cutting blade driving mechanism (not shown) having a thread cutting motor  84  (see FIG.  8 ). The movable cutting blade  70  is reciprocally swingable between a standby position shown by solid line and a maximum pivot position shown by two-dot chain line. Furthermore, a fixed cutting blade  73  cutting the needle thread  28  and bobbin thread in cooperation with the movable cutting blade  70  is fixed to the fixing plate with the blade portion thereof directed forward. Upon output of a needle thread cutting command, the positive rotation of the thread cutting motor  84  moves the operating lever  72  forward (a first half of reciprocal movement). With the forward movement of the operating lever  72 , the movable cutting blade  70  is caused to pivot to the maximum pivot position. As the result of pivoting of the movable cutting blade  70 , both needle thread  28  and bobbin thread are seized by the movable cutting blade  70 . In this case, the needle thread  28  is divided into a part of the needle thread  28  at the sewing needle side and another part of the needle thread  28  at the workpiece cloth side. 
     Subsequently, the thread cutting motor  84  is reverse rotated so that the operating lever  72  is moved rearward. In this case, the part of the needle thread  28  located at the workpiece cloth side and seized by the movable cutting blade  70  and the bobbin thread are cut by the blade part of the fixing blade  73  simultaneously. 
     Next, the control system of the multi-needle embroidery machine M will be described with reference to the block diagram of  FIG. 8 . A control device  75  controlling the multi-needle embroidery machine M comprises a microcomputer including a central processing unit (CPU)  76 , a read only memory (ROM)  77  and a random access memory (RAM). Various signals are supplied to the control device  75 . The signals include a rotation phase signal of the sewing machine main shaft detected by the rotation phase detector  80  and a signal delivered from the wiper origin detector  61  detecting the origin of the thread wiper  62 . Furthermore, the control device  75  delivers drive signals to a drive circuit  88  of a sewing machine motor  81 , a drive circuit  89  of the drive motor  46  operating the needle bar releasing mechanism  31  and the wiper drive mechanism  32 , a drive circuit  90  of the needle bar change motor  83 , a drive circuit  91  of the thread cutting motor  84 , a drive circuit  92  of the thread tension disc opening solenoid  85  and drive circuits  94  and  95  of the X-axis and Y-axis drive motors  86  and  87 . 
     The ROM  77  stores a drive control program for controlling the motors  81 ,  83 ,  84 ,  86  and  87  for the purpose of executing embroidery sewing, a plurality of types of sewing data and a control program for thread cutting which is peculiar to the invention and will be described later. In the thread cutting control, the thread wiper  62  is operated by the wiper driving mechanism  32  in the thread cutting so that a predetermined amount of thread is secured, whereby a predetermined amount of needle thread  28  is secured by the thread wiper  62 . The RAM  78  is provided with a sewing data memory on which sewing data is used for sewing and various necessary memories. 
     A thread cutting control executed by the control device  75  will be described with reference to  FIGS. 9A and 9B  which are flowcharts. Symbol Si (where i=11, 12, 13 . . . ) in  FIGS. 9A and 9B  designates each step. The thread cutting control starts when the embroidery sewing has been finished and a needle thread cutting command has been delivered. Upon stat of the thread cutting control, firstly, the thread cutting motor  84  is normally rotated when a rotation phase signal delivered from the rotation phase detector  80  indicates a timing of first half of reciprocal movement which moves the movable cutting blade  70  of the thread cutting mechanism  33  by a first half of reciprocal movement (S 11 : Yes), whereupon the movable cutting blade  70  is caused to pivot to the maximum pivot position (S 12 ). As a result, the needle thread  28  and the bobbin thread are seized by the movable cutting blade  70  by the first half of the reciprocal movement of the movable cutting blade  70 . In this case, the needle thread  28  is divided into the needle thread  28  part at the sewing needle side and the needle thread  28  part at the workpiece cloth side. 
     Subsequently, the drive motor  46  is driven so that the needle bar releasing mechanism  31  is operated (S 14 ) when the needle bar  10  has been moved to the uppermost position (S 13 : Yes). As a result, the needle bar  10  is stopped at the uppermost position, whereby the needle bar  10  is retained at the uppermost position, whereupon the needle bar  10  is not vertically moved in synchronization with the sewing machine main shaft. Subsequently, when the thread take-up  11  is moved to the uppermost position (S 15 : Yes), the sewing machine motor  81  is stopped (S 16 ). 
     Subsequently, the drive motor  46  is driven so that the thread wiper  62  is moved (projected) forward by maximum stroke (S 17 ). As a result, the needle thread  28   a  located downstream relative to the needle eye  15   a  of the needle  15  assumes a location where the needle thread  28   a  is engageable with the hook  62   b  of the wiper  62 . Next, the sewing machine motor  81  is reverse rotated by a predetermined slight rotational angle, so that the thread take-up  11  is moved downward by a slight distance (S 18 ). The drive motor  46  is driven by a slight rotational angle in synchronization with the downward movement of the thread take-up  11 , so that the thread wiper  62  is returned so that the needle thread  28  loosened as the result of downward movement of the thread take-up  11  is drawn in. More specifically, the thread wiper  62  is moved rearward with the thread take-up  11  being moved downward while the hook  62   b  of the thread wiper  62  is in engagement with the needle thread  28   a  at the sewing needle side. Accordingly, the needle thread  28   a  at the sewing needle side is rendered gradually longer such that an extra amount of needle thread  28  is secured. In this case, when the amount of needle thread  28   a  secured by the rearward movement of the thread wiper  62  (drawing) is below a predetermined amount (S 20 : No), S 18  and S 19  are repeated so that the thread amount securing operation is carried out by the wiper  62 . 
     More specifically, as shown in  FIG. 10 , the needle thread  28   a  located downstream relative to the needle eye  15   a  of the needle  15  at the workpiece cloth side is bent into a generally inclined L-shape such that a secured amount of the needle thread  28  is gradually increased. When the secured amount of needle thread reaches a predetermined amount (20 to 25 mm, for example; and S 20 : Yes), the thread cutting motor  84  is reverse rotated so that the movable cutting blade  70  is returned to the standby position, whereupon the needle thread  28  at the workpiece cloth side and the bobbin thread are simultaneously cut by the fixed cutting blade  73  (S 21 ). Since an amount of needle thread secured by the thread amount securing operation of the thread wiper  62  is readily supplied through the needle eye  15   a  from the thread take-up  11  side by the lowering of the thread take-up  11 , a predetermined extra amount of thread of the needle thread  28  is reliably secured. 
     Subsequently, the drive motor  46  is re-driven so that the thread wiper  62  wipes the needle thread  28  with movement thereof by maximum stroke rearward movement after the thread amount securing operation (S 22 ). In this case, the needle thread  28  is retained by the thread retaining tape  14   a  of the first thread retaining member  14  as described above. Subsequently, the thread tension disc opening solenoid  85  is driven so that the thread tension adjusting mechanism  9  is opened (S 23 ). In this state, the sewing machine motor  81  is positively rotated by a rotational angle of reverse rotation at S 18  so that the thread take-up  11  is moved upward to the original position (S 24 ). 
     Since the thread tension adjusting mechanism  9  is already open in the upward movement of the thread take-up  11 , an amount of needle thread necessary for upward movement of the thread take-up  11  is fed from the side of the thread tension adjusting mechanism  9  to which no thread tension is applied, that is, from a thread spool. Accordingly, an amount of thread at the needle thread end extending through the needle eye  15   a  of the needle  15  is prevented from being reduced. Thereafter, the drive of the thread tension opening solenoid  85  is stopped and the thread tension adjusting mechanism  9  is operated (S 25 ). The thread cutting control is thus finished. 
     When the needle thread  28  is seized by a beak of an outer rotary hook of a rotary hook  6 A in starting a subsequent sewing operation, the movable cutting blade  70  pivots to a location of maximum pivot so that the needle thread  28  is seized by the movable cutting blade  70 . As a result, the needle thread end  28   a  remaining on the upper side of the workpiece cloth is drawn into the lower side of the workpiece cloth. In other words, the needle thread end  28   a  no longer remains at the upper side of the workpiece cloth. 
     Thus, the multi needle embroidery sewing machine M is provided with the needle bar  10 , thread take-up  11 , thread take-up driving mechanism  22 , thread cutting mechanism  33 , thread wiper  62  and wiper driving mechanism  32 . When receiving a needle thread cutting command for actuating the thread cutting mechanism  33 , the control device  75  controls the movable cutting blade driving mechanism and the thread wiper driving mechanism so that the thread wiper  62  executes a thread amount securing operation to ensure the predetermined amount of needle thread located downstream relative to the eye  15   a  of the needle  15  in the case where the needle thread  28  which has been seized by the movable cutting blade  70  is in a state previous to the cutting of the needle thread  28 . Accordingly, the needle thread  28  is cut by the movable cutting blade  70  after the thread wiper  62  in engagement with the needle thread  28  has been operated for securing a thread amount when the needle thread  28  which has been seized by the movable cutting blade  70  is in a state previous to the cutting of the needle thread  28 . As a result, an extra remaining amount of needle thread  28  cut can be obtained according to an amount of thread amount securing operation of the thread wiper  62 . 
     Thus, an extra amount of needle thread remaining after the cutting of the needle thread can be secured by the operation of the thread wiper  62  for securing a thread amount without provision of a picker and a drive motor driving the picker in the cylinder bed  6 . Consequently, a reduction in the number of components can reduce the manufacturing costs, and the size of the cylinder bed  6  can be reduced. Furthermore, a necessary amount of needle thread remaining after thread cutting can be secured reliably and accurately. Additionally, since no picker is necessary, the distance between the rotary hook  6 A and the front end of the cylinder bed  6  can be reduced. Consequently, a sewing range can be increased. 
     Furthermore, the control device  75  controls the thread take-up driving mechanism  22  so that when the thread wiper  62  is to be caused to execute the thread amount securing operation, the thread take-up  11  is lowered a predetermined distance so that a predetermined amount of thread is secured by the thread wiper  62 . Thus, the predetermined amount of thread can easily be secured by the lowering of the thread take-up  11 . 
     Furthermore, the embroidery machine M further comprises the thread tension adjusting mechanism  9  which adjusts a tension of the needle thread  28  and the thread tension driving mechanism which drives the thread tension adjusting mechanism  9 . When the thread wiper  62  is caused to execute the thread amount securing operation, the control device  75  controls the thread tension driving mechanism so that the thread tension adjusting mechanism  9  is opened so that a predetermined amount of needle thread  28  can easily be secured by the opening of the thread tension adjusting mechanism  9 . 
     Furthermore, the embroidery machine M further has the needle bar releasing mechanism  31  turns on and off the driving force of the needle bar driving mechanism  30  driving the needle bar  10 . When the thread wiper  62  is to be operated to ensure a predetermined amount of thread, the control device  75  controls the needle bar releasing mechanism  31  so that the drive of the needle bar  10  is interrupted by the needle bar releasing mechanism  31 . Accordingly, since the needle bar  10  is stopped at the uppermost position, an extra amount of needle thread  28  secured by the thread wiper  62  can be rendered stable. Moreover, the interference can reliably be avoided between the sewing needle  15  mounted on the lower end of the needle bar  10  and the thread wiper  62 . 
     Modified forms of the foregoing embodiment will be described in the following. The thread tension adjusting mechanism  9  may be opened at S 18  where the thread cutting control is executed as described above. In this case, the needle thread  28  drawn out by the thread amount securing operation of the thread wiper  62  is easily supplied from the thread spool through the thread take-up  11  and the needle eye  15   a  to the thread wiper  62 . Consequently, an amount of thread remaining after the thread cutting can reliably be secured. Furthermore, an amount of operation for drawing out the needle thread  28  by the thread wiper  62  may optionally be settable according to a type, size and material of the needle thread  28 . Thus, the invention should not be limited to the foregoing embodiment. Those who are skilled in the art can modify the foregoing embodiment into various forms without departing from the gist of the invention. The invention encompasses these modifications. 
     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.