Patent Publication Number: US-7210418-B2

Title: Sewing apparatus, thread cassette therefor and control program therefor

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a sewing apparatus including a sewing mechanism in which a thread cassette holding a needle thread is used and a control program therefor. 
   2. Description of the Related Art 
   U.S. Pat. No. 3,749,039 to Russell A. Fritts discloses a sewing apparatus with a cassette mount to which a thread cassette holding a needle thread wound on a thread spool is attached. In the disclosed sewing apparatus, a user pushes the thread cassette downward while holding the thread cassette in hand, in order that the thread cassette may be attached to the cassette mount of the sewing apparatus. Furthermore, when the thread cassette is to be ejected from the cassette mount, the user raises the thread cassette while holding the cassette in hand. 
   The above-described manual handling of the thread cassette imposes load on the user, and furthermore, force applied to the thread cassette differs in the magnitude from one user to another. Accordingly, each mechanism of the sewing apparatus is required to have a sufficient performance to cope with every condition. For example, the thread cassette is not always attached to the cassette mount under a constant condition. Accordingly, when threading is carried out upon attachment of the thread cassette, an operating condition of the threading mechanism needs to be determined so as to be reliably carried out in a wide range. As a result, the construction of the sewing apparatus is complicated. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the present invention is to provide a sewing apparatus in which the thread cassette is carried by a carrier so that thread cassette can be attached to and ejected from the cassette mount under a constant condition. 
   The present invention provides a sewing apparatus in which a thread cassette holding a needle thread wound is used, comprising a cassette mount to which the thread cassette is detachably attached, a carrier carrying the thread cassette between an attachment start position and an attachment finish position in the cassette mount, and a control device for controlling rotation of a motor that moves the carrier. 
   In the above-described sewing apparatus, the control device controls the carrier so that the thread cassette is automatically inserted into and ejected from the cassette mount. Furthermore, the thread cassette can be attached to the cassette mount under a predetermined condition. 
   In a preferred form, the carrier includes a contract member brought into contact with the thread cassette or a supporting member when the thread cassette is supported by the supporting member and a driver for moving or rotating the contact member. Furthermore, the control device controls the driver so that the contact member is moved or rotated in a predetermined direction for insertion of the thread cassette into the cassette mount. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will become clear upon reviewing the following description of an embodiment of the invention, made with reference to the accompanying drawings, in which: 
       FIG. 1  is a front view of a sewing apparatus and a thread cassette in accordance with one embodiment of the present invention; 
       FIG. 2  is a broken front view of the sewing apparatus; 
       FIG. 3  is a right side view a thread tensioning mechanism and a needle thread take-up; 
       FIG. 4  is a schematic diagram of a carrying mechanism; 
       FIG. 5  is a block diagram showing an electrical arrangement of the sewing apparatus; 
       FIG. 6  is a flowchart showing an overall control program; 
       FIG. 7  is a flowchart showing a subroutine for thread cassette inserting process; 
       FIG. 8  is a flowchart showing a subroutine for a sewing process; 
       FIG. 9  is a flowchart showing a subroutine for a thread cassette ejecting process; 
       FIG. 10  is a front view of the sewing apparatus of a first modified form, showing a carrying mechanism using pinions; 
       FIG. 11  is a front view of the sewing apparatus of a second modified form, showing a carrying mechanism moving an engagement claw; and 
       FIG. 12  is a front view of the sewing apparatus of a third modified form, showing a supporting member of the thread cassette. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   One embodiment of the present invention will be described with reference to the accompanying drawings. Referring to  FIGS. 1 to 4 , a sewing machine  10  serving as a sewing apparatus comprises a sewing mechanism including a sewing needle  12  moved up and down and a shuttle  14  rotated in synchronization with the movement of the needle  12  as disclosed in Japanese Patent Application No. 2000-398263 filed by the assignee of the present application. The sewing machine  10  further comprises a cassette mount  22  to which a thread cassette  20  holding a needle thread used in the sewing mechanism is detachably attached. In use of the sewing machine  10 , the thread cassette  20  is attached to the cassette mount  22 . 
   The thread cassette  20  includes a thread accommodating cavity  23  for accommodating a thread spool  24  on which a needle thread  18  is wound. The thread spool  24  accommodated in the cavity  23  is covered with a lid (not shown). When the thread cassette  20  is attached to the cassette mount  22 , the user draws the needle thread  18  out of the thread spool  24 , extending the thread along a guide groove (not shown) formed in the top of the thread cassette  20  so that the thread extends around the thread cassette. More specifically, the needle thread  18  is drawn upward from the thread spool  24 , being extended leftward along the guide groove and then bent downward, as viewed in  FIG. 1 . The needle thread  18  is then bent rightward at the lower portion of the thread cassette  20 . The thread cassette  20  has an opening  28  formed therein so as to face the needle thread  18  extending horizontally and so as to be open downward. A needle thread take-up moving space  30  extending vertically is defined in the thread cassette  20  so as to communicate with the opening  28 . 
   A distal end of the needle thread  18  is bent forward, getting out of the guide groove. The needle thread  18  is then bent leftward, and the distal end of the thread is engaged with a thread engaging member  32  provided on the left front of the thread cassette  20 . Thus, the needle thread  18  extends along the front of the thread cassette  20 . 
   Furthermore, the sewing machine  10  is provided with a needle thread take-up  34  and a needle thread take-up eyelet  36  as disclosed in Japanese Patent Application No. 2002-91561 filed by the assignee of the present application. When the thread cassette  20  is attached to the sewing machine  10 , the needle thread  18  extending in the right-and-left direction is once moved in the rear of the sewing machine  10  along the needle thread take-up eyelet  36  with downward movement of the thread cassette  20 . Upon further downward movement of the thread cassette  20 , the needle thread  18  is moved in front of the sewing machine  10  to be caught on the needle thread take-up  34 . The needle thread take-up  34  and the needle thread take-up eyelet  36  are inserted into the needle thread take-up moving space  30  through the opening  28  below the thread cassette  20  lowered. 
   The sewing machine  10  is further provided with a threading mechanism  38  causing the needle thread  18  to pass through a hole (not shown) of the needle with the downward movement of the thread cassette  20  as disclosed in Japanese Patent application No. 2002-91558 filed by the assignee of the present application. The threading mechanism  38  comprises a threading hook mechanism  40  disposed on the left of the cassette mount  22  and a thread tensioning mechanism  42  disposed on the right of the cassette mount  22 . When the thread cassette  20  is moved downward in the cassette mount  22 , a threading shaft (not shown) having a threading hook (not shown) is moved downward by a first pressed member pressed by the thread cassette  20 . Furthermore, the threading shaft is swung to be rotated in the rear of the hole of the needle  12  so that the threading hook is caused to go into the hole (not shown) of the needle  12  and then leave the hole. 
   When the thread cassette  20  is moved downward in the cassette mount  22 , a supporting member  46  is moved downward by a second pressed member (not shown). The supporting member  46  has a thread catching member  44  catching the needle thread  18  of the thread cassette  20 . The thread catching member  44  is temporarily stopped in front of the hole of the needle  12  so that the needle thread  18  is tensioned. The supporting member  46  is moved upward when the threading hook catches the needle thread  18  and then leaves. A distal end of the needle thread  18  is disengaged from a thread engaging member  32  when the needle thread  18  is caught by the thread catching member  44  and moved downward. 
   Thus, the needle thread  18  extending in the right-and-left direction along the front of the thread cassette  20  is caught by the thread catching member  44  and then moved downward. The needle thread  18  is tensioned by the thread catching member  44  in front of the hole of the needle  12 . The needle thread  18  is then brought through the needle hole by the threading hook of the threading mechanism. 
   The sewing machine  10  includes a carrying mechanism  48  for carrying the thread cassette  20  vertically between an attachment start position and an attachment finish position relative to the cassette mount  22 . The carrying mechanism  48  includes two pulse motors  50  and  52  mounted in the sewing machine  10 , pulleys  54  and  56  fixed to motor shafts of the respective pulse motors, timing belts  58  and  50  conveyed by the respective pulleys, rotatable driven rollers  62  provided at bent portions of the timing belts respectively, and rubber rollers  64  and  66  rotated via the timing belts by the pulse motors respectively. 
   The rubber rollers  64  and  66  are disposed so that portions of circumferences of the rollers are opposed to each other so as to project to the inside of the cassette mount  22  at locations slightly lower than an entrance (top end) of the cassette mount respectively. A space between the rubber rollers  64  and  66  is set to be slightly smaller than a width of the thread cassette  20 . When the thread cassette  20  is inserted into the cassette mount  22  so as to be located at the attachment start position between the rubber rollers  64  and  66 , the rollers are elastically deformed slightly and brought into contact with flat right and left side faces of the thread cassette  20  respectively. The rubber rollers  64  and  66  are brought into contact with upper side faces of the thread cassette  20  even when the thread cassette reaches the lowermost attachment finish position. 
   When the pulse motors  50  and  52  are rotated in a predetermined direction, the rubber rollers  64  and  66  are rotated so that the thread cassette  20  is moved while being held by the rubber rollers, whereby the thread cassette is attached to or ejected from the cassette mount  22 . The rubber rollers  64  and  66  serve as contact members in the invention. The pulse motors  50  and  52  serve as drivers for the contact members. The aforesaid flat side faces of the thread cassette  20  serve as contacted members. 
   A light emitting element  70  and a light detecting element  72  both serving as a first detector are disposed just above the projecting portions of the rubber rollers  64  and  66 , near the entrance of the cassette mount  22  so as to be opposed to each other. A limit switch  76  is disposed at a vertically middle portion of the cassette mount  20  below the projecting portions of the rubber rollers  64  and  66 . The limit switch  76  detects a vertically middle position of the thread cassette  20  in the cassette mount  22 . The limit switch  76  serves as an ejection detector and includes a detecting section located on a movement path of the thread cassette  20  so as to be brought into contact with the left side face of the thread cassette. The cassette mount  22  includes a lowermost horizontal portion on which another limit switch  80  serving as a second detector is disposed. The limit switch  80  includes a detecting section projecting upward from the horizontal portion. The limit switch  80  is disposed so as to be brought into contact with the underside of the thread cassette  20  on the movement path of the thread cassette. The ejection detector may be used as the limit switch  80 . 
   The aforesaid pulse motors  50  and  52  are connected via respective drive circuits  90  and  92  to a control device  88  as shown in  FIG. 5 . The motors  50  and  52  are thus controlled by the control device  88  The control device  88  comprises CPU  82 , ROM  84 , RAM  86 , etc. ROM  84  stores a control program for controlling the pulse motors  50  and  52  and a control program for controlling the sewing operation. Necessary data is temporarily written onto RAM  86  during execution of each control program. The control device  88  has a timing function to successively writing counts onto RAM  86  so that time-up is detected. 
   The light emitting element  70 , light detecting element  72  and limit switches  76  and  80  are connected to the control device  88  so that the results of detection is supplied to the control device. To the control device  88  are further connected an ejection button  94  operated so that the pulse motors  50  and  52  are driven in order that the thread cassette  20  may be ejected from the cassette mount  22 , a sewing machine motor  96  for driving the sewing mechanism  16 , a start/stop button  98  for starting or stopping the sewing machine motor  96 , LCD  100  for displaying various messages and patterns, and a transparent touch panel  102 . The sewing machine motor  96  is connected via a drive circuit  103  to the control device  98 . 
     FIGS. 6 to 9  illustrate operations for inserting the thread cassette  20  into and ejecting the thread cassette  20  from the cassette mount  22 . When the sewing machine  10  is connected to the power supply, the control device  88  carries out a thread cassette inserting process (S 100 ), sewing process (step S 200 ), and thread cassette ejecting process (step S 300 ) successively. In the thread cassette inserting process (step S 100 ), the control device  88  firstly clears the timer (step S 102 ) and then displays, on LCD  100 , a message urging the user to insert the thread cassette  20  into the cassette mount  22  (step S 104 ). Based on the fact that the light detecting element  72  is detecting a predetermined amount of light from the light emitting element  70 , the control device  88  is on standby until the thread cassette  20  is inserted into the entrance of the cassette mount  22  (step S 106 ). 
   When the user inserts the thread cassette  20  slightly into the cassette mount  22  from above, light emitted from the light emitting element  70  is intercepted by the thread cassette  20 . Accordingly, since the light detecting element  72  cannot detect the predetermined amount of light from the light emitting element  70 , the control device  88  detects the thread cassette  20  having been inserted in the cassette mount  22  (YES at step S 106 ). Consequently, the control device  88  detects the thread cassette  20  having reached a drive start position where rotation of the rubber rollers  64  and  66  is started. The thread cassette  20  is brought into contact with the rubber rollers  64  and  66  below the light emitting and detecting elements  70  and  72 . The rubber rollers  64  and  66  are elastically deformed slightly thereby to adhere closely to the side faces of the thread cassette  20 . Thus, the thread cassette  20  is held between the rubber rollers  64  and  66 . 
   The control device  88  then displays on the LCD  100  a message that the thread cassette  20  is under transfer in the cassette mount  22  (step S 108 ). The pulse motors  50  and  52  are rotated so that the rubber rollers  64  and  66  move the thread cassette  20  downward (step S 110 ). More specifically, the pulse motor  50  for driving the right-hand rubber roller  64  is rotated counterclockwise thereby to rotate the roller counterclockwise, whereas the pulse motor  52  for driving the left-hand rubber roller  66  is rotated clockwise thereby to rotate the roller clockwise. As a result, the thread cassette  20  held between the rubber rollers  64  and  66  is automatically moved downward in the cassette mount  22 . Accordingly, the user need not operate the sewing machine  10  to input rotational directions for the respective pulse motors  50  and  52  every time when the thread cassette  20  is inserted into the cassette mount  22 , whereupon the convenience of the sewing machine  10  can be improved. When the thread cassette  20  is moved downward by the rollers  64  and  66 , the limit switch  76  is pressed by the left-hand side wall of the cassette to be turned on. The status of the limit switch  76  is monitored by the control device  88 . 
   The control device  88  starts the counting operation of the timer (step S 112 ) when the pulse motors  50  and  52  are rotated. The control device  88  is on standby until the thread cassette  20  is moved downmost by the rubber rollers  64  and  66  (step S 14 ). When the limit switch  80  is pressed by the underside of the thread cassette  20 , the control device  88  recognizes this (step S 114 ), whereupon the control device detects the thread cassette  20  having reached a drive stop position where the rubber rollers  64  and  66  in rotation are stopped. Thus, the control device  88  detects normal transfer of the thread cassette  20  into the cassette mount  22 . Successively, the control device  88  stops rotation of the pulse motors  50  and  52  (step S 116 ) so that rotation of the rubber rollers  64  and  66  is stopped. Thus, since the transfer (insertion) of the thread cassette  20  is automatically stopped, the user need not operate the sewing machine  10  to stop rotation of the pulse motors  50  and  52  every time when the thread cassette  20  is inserted into the cassette mount  22 , whereupon the convenience of the sewing machine  10  can be improved. 
   The control device  88  then controls the LCD  100  so that a message indicative of completion of transfer of the thread cassette  20  is displayed on the LCD for a predetermined period of time (steps S 118  to S 130 ). With downward movement of the thread cassette  20  in the cassette mount  22 , the threading mechanism  38  causes the needle thread  18  to pass through the hole of the needle  12 , and the needle thread is also caught by the thread take-up lever  34 , whereupon the preparation for start of the sewing operation is substantially completed. 
   The control device  88  stops the pulse motors  50  and  52  (step S 132 ) when the thread cassette  20  has not been transferred to the lowermost position in the cassette mount  22  for some reason (for example, wear of the rollers  64  and  66 ) within a predetermined period of time from rotation of the motor  50  and  52  (YES at step S 130 ). Thus, the transfer (insertion) of the thread cassette  20  by the rollers  64  and  66  is automatically stopped when push of the limit switch  80  is not detected within the predetermined period of time after start of rotation of the motors  50  and  52 . Accordingly, no particular input is required for stop of the motors  50  and  52  even when the thread cassette  20  has not reached the predetermined position in the cassette mount  22 . Consequently, the convenience of the sewing machine  10  can be improved. 
   The control device  88  then displays on the LCD  100  a transfer error message indicative of failure in the transfer of the thread cassette in the cassette mount  22 , and the display of the transfer error message is continued until absence of the thread cassette  20  in the cassette mount  22  is detected (steps S 134  to S 140 ). The control device  88  detects the absence of the thread cassette  20  in the cassette mount  22  when the limit switch  76  is not pressed by the thread cassette  20  and accordingly turned off and when the light detecting element  72  receives a predetermined amount of light. The limit switch  76  and the light emitting and detecting elements  70  and  72  serve as a thread cassette detector. Furthermore, the thread cassette  20  is sometimes ejected manually from the cassette mount  22  for re-insertion. This is also detected by the thread cassette detector. Successively, when determining that the thread cassette  20  is absent in the cassette mount  22  (step S 136 ), the control device  88  displays on the LCD  100  the instruction to insert the thread cassette  20  in the same manner as at the time of connection to the power supply (step S 104 ). 
   A sewing process (step S 200 ) is executed for a normal sewing operation when the thread cassette insertion process (step S 100 ) is completed with the thread cassette located at the lowermost position in the cassette mount  22  as described above. In the sewing process, the control device  88  automatically selects a straight stitch as an initial pattern (step S 202 ) and displays on the LCD  100  a pattern selecting screen on which a pattern other than the straight stitch can be selected (step S 204 ). When the pattern is changed via the transparent touch panel  102  by the user (YES at step S 206 ), a pattern changing process according to the changes is carried out (step S 208 ). When the start/stop button  98  is operated for start of the sewing operation (YES at step S 210 ), the control device  88  controls the sewing machine motor  96  and the like so that a sewing operation is carried out for the selected pattern (steps S 212  to S 216 ). 
   When the ejection button  94  is operated by the user after completion of the above-described sewing process (YES at step S 304 ), the control device  88  displays, on the LCD  100 , a message indicating that the thread cassette  20  is being ejected (step S 306 ) and then controls the pulse motors  50  and  52  so that the pulse motors and rubber rollers  64  and  66  are rotated a predetermined amount so that the thread cassette  20  is moved upward (step S 308 ). Successively, the control device  88  starts count by the timer function (step S 310 ). More specifically, when the ejection button  94  is depressed by the user, the pulse motor  50  driving the right-hand rubber roller  64  is rotated clockwise and the pulse motor  52  driving the left-hand rubber roller  66  is rotated counterclockwise, whereupon the thread cassette  20  is moved upward in the cassette mount  22 . Thus, the rubber rollers  64  and  66  are rotated in the respective directions so that the thread cassette  20  is automatically transferred (ejected) from the cassette mount  22 . Accordingly, the user need not operate the sewing machine for input of the rotational directions of the pulse motors  50  and  52 . 
   The aforesaid amount of rotation is set so that the thread cassette  20  projects sufficiently from the top of the sewing machine  10  in order that the thread cassette having been moved upward may manually be pulled out. Thus, the rubber rollers  64  and  66  are rotated by the predetermined amount rotation so that the thread cassette  20  is automatically transferred (ejected) from the cassette mount  22 . Accordingly, since the user need not input an amount of rotation of the rubber rollers  64  and  66  every time the thread cassette  20  is transferred, the convenience of the sewing machine can be improved. The number of pulses supplied to each of the pulse motors  50  and  52  which are controlled in ejection of the thread cassette  20  is determined on the basis of the predetermined amount of rotation. Furthermore, the control device  88  determines whether the pulse motors  50  and  52  and the rubber rollers  64  and  66  have been rotated by the predetermined amount of rotation, based on the number of drive pulses supplied to the pulse motors  50  and  52  in the ejection process. 
   The control device  88  stops the pulse motors  50  and  52  (step S 332 ) when the thread cassette  20  has not been moved upward to a lowermost position where the detecting section of the limit switch  76  is not pressed by the side walls of the thread cassette, within a predetermined period of time starting from rotation of the pulse motors for some reason (for example, wear of the rubber rollers) (YES at step S 330 ). Thus, the transfer or ejection of the thread cassette  20  by the rubber rollers  64  and  66  is automatically stopped when depression of the limit switch  76  is not detected within a predetermined period of time from start of rotation of the pulse motors  50  and  52 . Accordingly, the user need not operate the sewing machine to stop the pulse motors  50  and  52  even when the thread cassette  20  does not reach a predetermined position under a predetermined condition. Consequently, the convenience of the sewing machine can be improved. 
   The control device  88  then displays, on the LCD  100 , a transfer error message indicative of failure in the transfer of the thread cassette in the cassette mount  22 , and the display of the transfer error message is continued until the absence of the thread cassette  20  in the cassette mount  22  is detected (steps S 334  to S 340 ). Whether the thread cassette  20  is present in the cassette mount  22  is detected by a thread cassette detector comprising the limit switch  76  and light emitting and detecting elements  70  and  72 . More specifically, the control device  88  detects the absence of the thread cassette  20  in the cassette mount  22  when the limit switch  76  is not pressed by the thread cassette  20  and accordingly turned off and further when the light detecting element  72  receives the predetermined amount of light. Thus, the thread cassette  20  having been manually pulled out is detected. Successively, when determining that the thread cassette  20  is absent in the cassette mount  22  (step S 336 ), the control device  88  clears the timer and display (step S 338 ), returning to the thread cassette insertion process (step S 100 ). 
   In the foregoing embodiment, the sewing machine  10  includes the threading mechanism  38  having a member moved by the thread cassette  20 , and the thread cassette  20  is automatically transferred by the transfer mechanism  48 . Accordingly, the transfer speed of the thread cassette  20 , the load for the transfer, etc. are constant as compared with the case where the thread cassette is manually transferred. Consequently, since operating conditions of the threading mechanism  38  are unified, the threading mechanism can be designed more easily as compared with the case where the threading mechanism is designed according to numerous operating conditions of the manual operation. 
   The pulse motors  50  and  52  are provided as the actuators operated in the insertion and ejection of the thread cassette  20  in the foregoing embodiment. However, the actuators may be operated for either insertion or ejection of the thread cassette, instead. Furthermore, although the pulse motors serve as the actuators in the foregoing embodiment, servo motors or solenoids may be used as the actuators, instead. 
   The two pulse motors  50  and  52  are provided for rotating the two rubber rollers  64  and  66  respectively in the foregoing embodiment. However, a single pulse motor may be provided for rotating the two rubber rollers  64  and  66 , or the transfer mechanism  48  may comprise a single pulse motor and a single rubber roller rotated by the single pulse motor for the insertion and ejection of the thread cassette  20 , instead. Furthermore, the exclusive pulse motors  50  and  52  are provided for the rubber rollers  64  and  66  respectively in the foregoing embodiment. However, another pulse motor provided for another function in the sewing machine may be used to rotate the rubber rollers  64  and  66 , instead. Such a motor may include a pulse motor for swinging a needle, a pulse motor for automatic threading, a pulse motor for automatic thread tensioning and a pulse motor for adjusting feed pitch of a feed dog. 
   In the foregoing embodiment, the insertion of the thread cassette  20  into the cassette mount  22  is detected by the light emitting and detecting elements  70  and  72  so that the pulse motors  50  and  52  automatically start. However, the user may operate an insertion button provided on the sewing machine so that the pulse motors start, instead. 
   Furthermore, in the foregoing embodiment, the control device  88  stops the pulse motors  50  and  52  when the thread cassette  20  has not been transferred to the lowermost position in the cassette mount  22  for some reason within the predetermined period of time from rotation of the motor  50  and  52 . Although the count starts from the time when the rotation of the pulse motors starts, it may start from the time when the limit switch  76  is depressed by the side walls of the thread cassette  20 , instead, for example. Thus, the count may start from another phase. Furthermore, the time when the driver is stopped is determined on the basis of the aforesaid predetermined period of time in the foregoing embodiment. However, the time may be determined on the basis of the number of drive pulses supplied to the pulse motors  50  and  52 , instead. The count of the drive pulses may start from the time when rotation of the pulse motors starts or the time when the limit switch  76  is depressed by the side walls of the thread cassette  20 , instead. Thus, the count of the drive pulses may start from another phase. 
   The thread cassette  20  holds the needle thread  18  wound on the thread spool  24  in the foregoing embodiment. However, the needle thread  18  need not be wound on a core member such as the thread spool and may be drawable, instead. Furthermore, the thread cassette  20  has a wall surrounding the thread spool  24  in the foregoing embodiment. If only the thread spool can be disposed in the thread cassette  20 , the wall may or may not be provided. 
   In the foregoing embodiment, reach of the reach of cassette  20  to the drive stop position where the drive of the pulse motors  50  and  52  is stopped is detected by the limit switch  80  having been depressed by the underside of the thread cassette. However, the reach may be determined on the basis of a predetermined period of time starting from a predetermined phase such as ON-OFF time of the limit switch  76  or the number of drive pulses supplied to the pulse motors  50  and  52  (an amount of rotation), instead. 
   The rubber rollers  64  and  66  are brought into contact with the thread cassette  20  in the foregoing embodiment. However, a pair of pinions  104  and  106  may be provided instead of the rubber rollers as shown in  FIG. 10 . In this case, the thread cassette  20  has racks which are formed on the opposed side walls thereof so as to be engaged with the pinions  104  and  106 , so that the thread cassette is transferred while the pinions and racks are engaged with each other. 
   Furthermore, the sewing machine  10  may be provided with a pair of vertically movable engagement claws  112  and  114 , instead of the rubber rollers  64  and  66 , as shown in  FIG. 11 . In this case, the thread cassette  20  is formed with depressions  116  and  118  engaging the engagement claws  112  and  114 . The engagement claws  112  and  114  are engaged with the depressions  116  and  118  respectively so that the thread cassette  20  is transferred. More specifically, the thread cassette  20  may be transferred using a moved contact member instead of the rotating contact member. In this construction, a space between arms  120  and  122  with the engagement claws  112  and  114  respectively are spread slightly larger than the width of the thread cassette  20  in the right-and -left direction, only when the arms project above the sewing machine  10 , whereby the claws are engaged with the respective depressions  116  and  118 . 
   The rubber rollers  64  and  66  are brought into contact with the thread cassette  20  in the foregoing embodiment. However, as shown in  FIG. 12 , a cassette supporting member  124  supporting the thread cassette  20  may be brought into contact with the rubber rollers  64  and  66 , whereby the cassette supporting member is vertically moved together with the thread cassette by the rubber rollers so that the thread cassette is transferred, insteadly. 
   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.