Patent Publication Number: US-7908027-B2

Title: Sewing machine

Description:
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application 2006-088153, filed on, Mar. 28, 2006 the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present disclosure is directed to a sewing machine that secures user safety when foreign objects such as user&#39;s fingers approach the sewing needle. 
     BACKGROUND 
     Sewing machines provided with safety covers have been suggested to keep external objects such as user&#39;s fingers away from a vertically moving sewing needle during a sewing operation. Also sewing machines have been suggested where a safety operation of some sort is executed upon optical detection of external objects such as user&#39;s fingers approaching the sewing needle. 
     A safety cover described in JP H11-267388 B (patent document 1) includes an arm coupled rotatably to a lower end of a presser bar, a protective plate formed integrally to a front end of the arm, and a lens provided in an open window of the protective plate. The protective plate of the safety cover is switchable between an active position that covers the front side of the needle bar and a retracted position retracted rearward. 
     A cloth presser unit of a sewing machine described in JP 2002-306878 A (patent document 2) is provided with two pairs of optical sensors composed of two light-receiving portions and two light-emitting portions. The two upwardly-oriented light-receiving portions are disposed on the upper surface of a presser holder that covers the upper side of a cloth presser foot so as to embrace the vertical movement locus (vertical reciprocating area of the sewing needle) of the sewing needle. The two downwardly-oriented light-emitting portions are disposed so as to confront the two light-receiving portions from above. When light projected from the respective light-emitting portions to the light-receiving portions are blocked by a foreign object, a control unit activates the needle swing/needle release pulse motor to drive the needle-bar release mechanism and block the transmission of drive force to the needle bar. 
     In order to employ the safety cover described in patent document 1 to a sewing machine, the presser foot needs to be removed from the presser bar. Thus, incorporation of the safety cover is cumbersome and time consuming for the user. Also, even if the safety cover is rotated to the retracted position, the safety cover still becomes an impediment upon needle threading, needle replacement, and presser foot replacement, providing poor workability. 
     According to the cloth presser unit of a sewing machine described in patent document 2, when light projected from the light-emitting portions to the light-receiving portions is blocked by foreign objects (such as user&#39;s fingers) in the vertical movement locus, a detection of foreign object is made. The problem with such configuration is that the detection range that allows detection of foreign object is extremely small. In order to increase the detection range, multiple pairs of light sensors are required, which brings adverse effects to cost reduction and compact spacing. 
     SUMMARY 
     An object of the present disclosure is to provide a sewing machine capable of securing user safety when foreign objects such as user&#39;s fingers approach the sewing needle by employing a configuration which is easy to install, provides good workability, is cost saving, and allows compact spacing. 
     The sewing machine of the present disclosure includes a needle bar that has a sewing needle attached in a lower end thereof; a needle-bar vertical drive mechanism that vertically moves the needle bar by a sewing machine motor via a sewing machine main shaft; an imaging unit that captures image of at least the sewing needle and a moving object that is in close proximity of the sewing needle; a distance calculating portion that calculates a distance between the sewing needle and the moving object based on image data captured by the imaging unit; a judging portion that makes a judgment that the distance calculated by the distance calculating portion is equal to or less than a predetermined distance; and a control portion that controls execution of a predetermined safety operation based on a judgment result of the judging portion. 
     According to such configuration, when a moving object such as a finger approaches the sewing needle during a sewing operation, an image of the sewing needle and the moving object that has approached the sewing needle are captured, and the distance (proximity distance) between the sewing needle and the moving object is calculated based on the image data captured. In case the calculated proximity distance is equal to or less than a predetermined distance, a predetermined safety operation is executed. Thus, user safety is reliably secured in case user&#39;s fingers approach the sewing needle. 
     In such case, mere provision of a single imaging unit allows wide-range detection of the moving object approaching the sewing needle. Hence, considerable enhancement of user safety can be achieved. Furthermore, the configuration of the present disclosure is easy to install, provides good workability, is cost saving, and allows compact spacing. 
     Also, the sewing machine of the present disclosure includes a needle bar that has a sewing needle attached in a lower end thereof; a needle-bar vertical drive mechanism that vertically moves the needle bar by a sewing machine motor via a sewing machine main shaft; an imaging unit that captures image of at least the sewing needle and a moving object that is in close proximity of the sewing needle; a time calculating portion that calculates a time taken for the moving object to enter a vertical movement locus of the sewing needle based on image data captured by the imaging unit; a judging portion that makes a judgment that the time calculated by the time calculating portion is equal to or less than a predetermined time; and a control portion that controls execution of a predetermined safety operation based on a judgment result of the judging portion. 
     According to such configuration, the time taken (arrival time) for the moving object to enter the vertical movement locus of the sewing needle is calculated based on the image data containing the image of the sewing needle and the moving object approaching the proximity of the sewing needle. In case the calculated arrival time is equal to or less than the predetermined time, the predetermined safety operation is executed. Thus, user safety can be reliably secured in case foreign objects such as user&#39;s fingers approach the sewing needle. 
     In such case also, mere provision of a single imaging unit considerably enhances user safety. Also, the configuration of the present disclosure is easy to install, provides good workability and moreover is cost saving and allows compact spacing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the illustrative aspects with reference to the accompanying drawings, in which, 
         FIG. 1  is a front view of a lockstitch sewing machine in its entirety in accordance with a first illustrative aspect of the present disclosure; 
         FIG. 2  is a front view of a lockstitch sewing machine in its entirety with an embroidery unit attached; 
         FIG. 3  is a partial front view illustrating an inner configuration of a head of the lockstitch sewing machine; 
         FIG. 4  is a partial front view illustrating a needle-bar vertical drive mechanism and a needle-bar release mechanism; 
         FIG. 5  is a partial side view illustrating a needle-bar vertical drive mechanism and a needle-bar release mechanism; 
         FIG. 6  is a vertical sectional front-view of a first cam member; 
         FIG. 7  is a block diagram of a control system of the lockstitch sewing machine; 
         FIGS. 8A ,  8 B and  8 C are flowcharts of a safety control; 
         FIG. 9  illustrates an image data captured immediately before sewing start; 
         FIG. 10  illustrates an image data captured after sewing start; 
         FIG. 11  illustrates an image data captured after sewing start; and 
         FIGS. 12A and 12B  are flowcharts of the safety control in accordance with a second illustrative aspect of the present disclosure; 
     
    
    
     DETAILED DESCRIPTION 
     A first embodiment of the present disclosure is described with reference to  FIGS. 1 to 11 .  FIG. 1  illustrates a lockstitch sewing machine M with an embroidery unit detached, and  FIG. 2  illustrates the lockstitch sewing machine M with the embroidery unit attached to enable embroidery sewing. 
     Referring to  FIG. 1 , the lockstitch sewing machine M includes a bed  1 , a pillar  2  standing on the right end of the bed  1 , and an arm  3  extending leftward from the upper end of the pillar  2  so as to confront the bed  1 . The bed  1  is provided with a free arm (not shown) allowing attachable/detachable attachment of an embroidery unit  12  (refer to  FIG. 2 ) thereto and the attachment of the embroidery unit  12  allows execution of embroidery sewing by the lockstitch sewing machine M. 
     The bed  1  includes a cloth feed mechanism, a loop taker, and a thread cutting mechanism (none of which are shown). The cloth feed mechanism is provided with a feed dog vertically moving mechanism that vertically moves the feed dog and the feed dog longitudinally moving mechanism that longitudinally moves the feed dog (neither of which are shown). The loop taker is composed of a horizontal rotary shuttle containing a bobbin (not shown) therein and operates in cooperation with the sewing needle  6 . The thread cutting mechanism cuts a needle thread and a bobbin thread. 
     A start/stop switch  7  that instructs start and stop of a sewing operation is provided in the front face of the arm  3 . Provided in the front face of the pillar  2  is a liquid crystal display  8  capable of displaying color images. The liquid crystal display  8  displays various normal stitch patterns (normal patterns), various function names, pattern names, and various messages, and the like. Touch keys (not shown) composed of transparent electrodes are provided in the front face of the liquid crystal display  8  and pattern selection of the patterns to be sewn and selection of functions to be executed are rendered by operating the applicable touch keys. 
     Provided in the underside of the head  4 , more specifically in the portion forward relative to a needle bar  5  is a downwardly oriented image sensor  9  capable of capturing color images. The image sensor  9  is configured by a CCD (charge coupled device) imaging element and captures images of a workpiece cloth W (refer to  FIGS. 9 to 11 ) placed on the upper surface of the bed  1  from a substantially upward direction. 
     When the workpiece cloth W to be sewn is placed on the upper surface of the bed  1 , the image sensor  9  obtains an image of a substantially rectangular imaging range illustrated in  FIG. 10 . The imaging range captures the sewing needle  6  attached to the lower end of the needle bar  5 , a presser foot  11  attached to the lower end of the presser bar  10  and the moving object  73  in close proximity of the sewing needle  6  in addition to the workpiece cloth W. 
     Referring to  FIG. 3 , provided in the head  4  of the lockstitch sewing machine M is a needle-bar vertical drive mechanism  15 , a thread tension mechanism  80 , a needle-bar swing mechanism  90  and a needle-bar release mechanism  30  (refer to  FIG. 4 ). The needle-bar vertical drive mechanism  15  vertically drives the needle bar  5 . The thread tension mechanism  80  applies tension on the needle thread residing in a needle thread route extending from a thread spool (not shown) to the sewing needle  6 . The needle-bar swing mechanism  90  swings the needle bar  5  in a direction perpendicular (lateral direction) to a cloth feed direction. The needle-bar release mechanism  30  blocks the transmission of drive force that vertically moves the needle bar  5 . The needle-bar swing mechanism  90  and the needle-bar release mechanism  30  are driven by a drive force of a single common drive motor  40 . 
     Next, a description will be given on the needle-bar vertical drive mechanism  15  based on  FIGS. 3 to 5 . 
     A vertically oriented needle-bar support  16  is disposed in the substantially central portion of the head  4 . The upper end of the needle-bar support  16  is pivoted to a frame F by a pivot pin  17 , whereby the needle-bar support  16  is rendered swingable relative to the frame F. The needle bar  5  is supported vertically movably by the needle-bar support  16  and the sewing needle  6  is attachably/detachably attached to the lower end of the needle bar  5 . 
     Secured at the distal end of a sewing machine main shaft  18  rotated by a sewing machine motor  56  (refer to  FIG. 7 ) is a thread take-up crank  19 . At one end of the thread take-up crank  19 , a needle-bar crank rod  20  is coupled rotatably at one end thereof (the upper end in  FIGS. 3 and 4 ) and a needle-bar clamp  21  is coupled at the other end thereof. The above described needle bar  5  is vertically moved via the needle-bar clamp  21  and a later described coupling mechanism  22 . 
     Next, a description will be given on the coupling mechanism  22 . The needle bar  5  has the needle-bar clamp  21  supported slidably thereto and a securing element  23  secured thereto. The securing element  23  has an upper end of a vertically-oriented swinging element  24  rotatably pivoted thereto. The swinging element  24  is elastically biased by a torsion spring  25  so that an engagement projection  24   a  provided in the lower end of the swinging element  24  is engaged with an engagement recess  21   a  of the needle-bar clamp  21 . 
     When the sewing machine main shaft  18  is rotated by the sewing machine motor  56 , the needle-bar clamp  21  is vertically moved via the thread take-up crank  19  and the needle-bar crank rod  20 . At this time, the needle bar  5  is vertically reciprocated via the coupling mechanism  22 . 
     Next, a description will be given on the needle-bar release mechanism  30  that blocks synchronization of the needle bar  5  and the sewing machine main shaft  18 . 
     Referring to  FIGS. 4 and 5 , a vertically oriented rotary shaft  31  is secured in the substantial lower-half portion of the left side of the needle-bar support  16 . The rotary shaft  31  has rotatably pivoted thereto a blocking plate  32  being integrally formed by an activating plate  33  in plate-form and a drive lever  34 . The lateral width of the activating plate  33  corresponds to the substantial left-half width of the needle-bar support  16  and the vertical length of the of the activating plate  33  corresponds to the length of the substantial lower half of the needle-bar support  16 . 
     An engagement pin  35  is secured at the distal end of the drive lever  34  and the engagement pin  35  is capable of abutting a blocking cam  44   b  (refer to  FIG. 6 ) of a later described first cam  44  from the rearward direction. Also, the blocking plate  32  is biased counterclockwise in plan view by a coil spring  36  and the activating plate  33  is capable of engaging with an engagement projection  24   b  of the swinging element  24  from the rearward direction. 
     When the first cam  44  is rotated clockwise, the engagement pin  35  is moved rearward by the blocking cam  44   b . At this time, the blocking plate  32  is rotated clockwise in plan view and the activating plate  33  is engaged with the engagement projection  24   b . Thus, the engagement projection  24   a  of the swinging element  24  is separated from the engagement recess  21   a  of the needle-bar clamp  21 , thereby blocking the transmission of the drive force that vertically moves the needle bar  5 . 
     An extension coil spring  38  is hooked on a spring receptacle  37  mounted on the needle-bar support  16 . When the engagement projection  24   a  of the swinging element  24  is separated from the engagement recess  21   a  of the needle-bar clamp  21 , the needle bar  5  swings to the uppermost position by the extension coil spring  38  and is maintained at the uppermost position. After the transmission of drive force to vertically move the needle bar  5  has been blocked, the blocking plate  32  returns to a stand-by position as illustrated in  FIG. 4 . When the needle-bar clamp  21  is lifted from this state, the engagement projection  24   a  automatically engages with the engagement recess  21   a  with guidance of a sloped guide surface  21   b  of the needle-bar clamp  21 . Thus, the coupling of the needle bar  5  and the sewing machine main shaft  18  is reestablished to allow vertical movement of the needle bar  5 . 
     Referring to  FIG. 3 , a drive motor  40  composed of a step motor is disposed in the mid portion of the head  4  and a drive gear  41  is secured to a drive shaft of the drive motor  40 . Secured on an auxiliary frame  43  below the drive shaft of the drive motor  40  is a rear end of a longitudinally-oriented first pivot shaft  42 . Referring to  FIG. 6 , the first pivot shaft  42  has the first cam  44  pivoted rotatably thereto. The first cam  44  has formed thereto a swing cam  44   a  eccentric with respect to the first pivot shaft  42  and a blocking cam  44   b  projecting rearward. 
     Immediately after power is supplied to the lockstitch sewing machine M, the drive motor  40  is driven for initializing purposes and initial setting is performed. When a sewing process is executed in this state, the needle bar  5  is moved vertically as well as being swung by the drive of the drive motor  40  proportionate to the swing width. Then stitches are formed on the workpiece cloth W by using a needle thread subject to optimized thread tension. 
     The first cam  44  reaching a predetermined phase angle by the drive of the drive motor  40  denotes a start of a blocking period where synchronization between the needle bar  5  and the sewing machine main shaft  18  is blocked. In the blocking period, since the engagement pin  35  is moved rearward by the blocking cam  44   b , the blocking plate  32  is rotated clockwise in plan view and the engagement projection  24   a  of the swinging element  24  is separated from the engagement recess  21   a  of the needle-bar clamp  21 . Thus, the synchronization of the needle bar Sand the sewing machine main shaft  18  is blocked and the needle bar  5  is slid to the uppermost position by the extension coil spring  38  and retained at the uppermost position. 
     Referring to  FIG. 2 , the embroidery unit  12  includes a body frame  12   a , an embroidery frame  13  that holds the workpiece cloth W, a Y-direction drive portion  14 , and an X-direction drive mechanism (not shown). The Y-direction drive portion  14  houses therein a Y-direction drive mechanism (not shown) that drives the embroidery frame  13  in the Y-direction (longitudinal direction). The X-direction drive mechanism (not shown) is contained in the body frame  12   a  and drives the Y-direction drive portion  14  in the X-direction (lateral direction). 
     The Y-direction drive portion  14  is provided with a carriage (not shown) and the carriage has the embroidery frame  13  attached attachably/detachably thereto via a connection portion (not shown). The X-direction drive mechanism drives the Y-direction drive mechanism inclusive of the carriage in the X-direction by the drive of an X-shaft drive motor  60 . The Y-direction drive mechanism drives the carriage in the Y-direction by the drive of a Y-shaft drive motor  61 . 
     When the embroidery unit  12  is attached to the free arm, the X-shaft drive motor  60  and the Y-shaft drive motor  61  establish electrical connection with a control unit  50  of the lockstitch sewing machine M. The control unit  50  controls the drive of the X-shaft drive motor  60  and the Y-shaft drive motor  61  respectively. By connecting the embroidery frame  13  having the workpiece cloth W attached thereto to the carriage, the embroidery frame  13  can be moved in the X- and Y-directions, thereby allowing formation of embroidery patterns on the workpiece cloth W. 
     Next, a description will be given on a control system of the lockstitch sewing machine M. 
     Referring to  FIG. 7 , the control unit  50  is configured by a computer including a CPU  51 , a ROM  52 , a RAM  53  and an electrically-rewritable nonvolatile flash memory (F/M)  54 . 
     The control unit  50  has connected thereto a start/stop switch  7 , a timing signal generator  55  that detects the rotational position of the sewing machine main shaft  18 , and the image sensor  9  respectively. Also, the control unit  50  has connected thereto a drive circuit  62  for the sewing machine motor  56 ; a drive circuit  63  for the drive motor  40 ; a drive circuit  64  for a cloth feed motor  57  that drives the cloth feed mechanism; a drive circuit  65  for a thread cut motor  58  that drives the thread cut mechanism; a display drive circuit  66  for the liquid crystal display  8 ; a drive circuit  67  for a warning buzzer  59 ; and two drive circuits  68  and  69  respectively. When the embroidery unit  12  is attached to the lockstitch sewing machine M, the X-shaft drive motor  60  is connected with the drive circuit  68  and the Y-shaft drive motor  61  is connected with the drive circuit  69 . 
     The ROM  52  has preinstalled therein a sewing control program that sews various utility patterns and embroidery patterns; control programs for display control in general; and a later described control program for safety control. Areas for providing flags, pointers, counters, registers, and buffers and the like required for execution of various controls are allocated in the RAM  53  on a required basis. 
     Next, the safety control executed by the control unit  50  of the lockstitch sewing machine M will be described based on the flowcharts indicated in  FIGS. 8A ,  8 B and  8 C. The reference symbol Si (i=11, 12, 13 . . . ) in the drawings indicate each step number of the control. 
     The control unit  50  starts the control when power is supplied to the lockstitch sewing machine M. First, an imaging process is executed by the image sensor  9  (step S 11 ). In the imaging process, the control unit  50  captures image of the front side portion of the sewing needle  6  within the rectangular imaging range (refer to  FIGS. 9 to 11 ). The image is captured from the direction rearward relative to the sewing needle  6 . Imaging of a portion of the workpiece cloth W, a presser foot  11 , a portion of the sewing needle  6 , and the moving object  73  are allowed in the imaging range. When the imaging process is terminated, the control unit  50  proceeds to step S 12  to determine whether a start operation has been operated on the start/stop switch  7  or not. In case a start operation is not operated (NO), the control unit  50  repeats steps S 11  and S 12 . In case a start operation has been operated on the start/stop switch  7  in step S 12  (YES), the control unit  50  proceeds to step S 13 , and the image data containing the status immediately before sewing start is stored in the flash memory  54 . The image data may be stored in the RAM  53  instead of the flash memory  54 . 
     Next, the control unit  50  proceeds to step S 14  to execute a sewing process by driving the sewing machine motor  56 . When the sewing process is executed, the control unit  50  judges whether or not a stop operation is operated on the start/stop switch  7  (step S 15 ). In case the stop operation is not operated on the start/stop switch  7  (No), the control unit  50  executes the imaging process (step S 16 ) by the image sensor  9  while continuing the sewing process and executes a moving object detection process (step S 17 ) based on the image data captured. In the moving object detection process, the control unit  50  compares the image data captured immediately before sewing start (refer to  FIG. 9 ), in other words, the image data containing no images of moving objects  73 , and the image data captured in step S 16  after sewing start (refer to  FIG. 10  or  FIG. 11 ). 
     In the moving object detection process, first, the control unit  50  binarizes the image data is by using a “threshold value” that identifies the components of the sewing machine such as the presser foot  11 , the presser bar  10 , and the sewing needle  6  and the moving object  73  by the control unit  50 . Then, the control unit  50  executes noise cancellation process, and the like on the image data and thereafter executes an outline extraction process that extracts the outlines of the presser foot  11 , the presser bar  10 , the sewing needle  6  and the moving object  73 . 
     Among the objects contained in the image data immediately before sewing start, the sewing needle  6  is moved vertically with regularity, and the workpiece cloth W is moved with regularity in the sewing direction in correlation with the cloth feed movement. On the other hand, user&#39;s fingers and various objects such as scissors used by the user involve irregular motion. Thus, such objects hinder safety when they come into contact with the sewing needle  6 . Such being the case, the control unit  50  excludes objects assuming regular motion from the moving object  73  and detects only the objects assuming irregular motion as the moving object  73 . A needle drop position N of the sewing needle  6  taken on the workpiece cloth W is predetermined in the image data. 
     Subsequently, the control unit  50  proceeds to step S 18  and judges whether or not a moving object  73  has been detected by the moving object detection process. If no moving object  73  has been detected (NO), the control unit  50  repeats steps S 15  onwards. If a moving object  73  has been detected (YES), the control unit  50  proceeds to step S 19  and calculates the horizontal distance between the sewing needle  6  and the moving object  73  as a proximity distance D. Then, the control unit  50  proceeds to step S 21  and determines whether or not an embroidery mode is selected. In case of sewing a normal pattern without attachment of the embroidery unit  12  upon sewing start, the embroidery mode will not be selected. In case the embroidery mode is not selected in step S 21  (NO), the control unit  50  proceeds to step S 30  and judges the value of the proximity value Din a step-by-step manner. Then, the predetermined safety operation is executed based on the result of judgment of the proximity distance D. 
     If proximity distance D is greater than 50 mm (D&gt;50 mm), in other words, if there is no possibility of the moving object  73  contacting (interfering) with the sewing needle  6 , the control unit  50  repeats steps S 15  onwards. If the proximity distance D is equal to or less than 50 mm and greater than 30 mm (50 mm≧D&gt;30 mm), the control unit  50  proceeds to step S 31  and warns the user by the warning buzzer  59 . If the proximity distance D is equal to or less than 30 mm and greater than 10 mm (30 mm≧D≧10 mm), the control unit  50  proceeds to step S 32  and executes a deceleration process that decelerates the rotational speed of the sewing machine motor  56  to a predetermined speed. Then, the control unit  50  warns the user by activating the warning buzzer  59  (step S 33 ) and displays a warning message to the liquid crystal display  8  (step S 34 ). 
     If the proximity distance D is equal to or less than 10 mm (D≦10 mm), in other words, if the moving object  73  is in immediate proximity of the sewing needle  6 , the control unit  50  proceeds to step S 35  and executes a release operation that blocks synchronization of the needle bar  5  and the sewing machine main shaft  18 . In the release operation, the needle bar  5  is released via the needle-bar release mechanism  30  by driving the drive motor  40 . Next, the control unit  50  proceeds to step S 36  and brings the sewing machine motor  56  to an emergency halt. Then, the control unit  50  warns the user of the emergency halt by activating the warning buzzer  59  (step S 37 ) and displays a warning message to the liquid crystal display  8  (step S 38 ). Thereafter, the control unit  50  repeats steps S 11  onwards. 
     On the other hand, when the embroidery unit  12  is attached upon sewing start to sew embroidery patterns, the embroidery mode is selected. If the embroidery mode is selected in step S 21  (YES), the control unit  50  proceeds to step S 22  and judges the value of the proximity distance D in a step-by-step manner. Then, a predetermined safety operation is executed based on the result of judgment of the proximity distance D. The judgment value applied for step-by-step judgment of the proximity distance D by the control unit  50  in the embroidery mode is set at a larger value as compared to non-embroidery mode values (such as 50 mm, 30 mm and 10 mm applied in the above step S 30 ). 
     If the proximity value D is greater than 100 mm (D&gt;100 mm), in other words if there is no possibility of the moving object  73  contacting the sewing needle  6 , the control unit  50  repeats steps S 15  onwards. If the proximity distance D is equal to or less than 100 mm and greater than 50 mm (100 mm≧D&gt;50 mm), the control unit  50  proceeds to step S 23  and executes the deceleration process that decelerates the rotational speed of the sewing machine motor  56  to a predetermined speed. Then, the control unit  50  warns the user by activating the warning buzzer  59  (step S 24 ) and displays a warning message to the liquid crystal display  8  (step S 25 ). 
     If the proximity distance D is equal to or less than 50 mm (D≦50 mm), in other words, if the moving object  73  is in immediate proximity of the sewing needle  6 , the control unit  50  proceeds to step S 26  and executes the release operation of the needle bar  5 . In the release operation, the needle bar  5  is released via the needle-bar release mechanism  30  by driving the drive motor  40 . Next, the control unit  50  proceeds to step S 27  and brings the sewing machine motor  56  to an emergency halt. Then, the control unit  50  warns the user of the emergency halt by activating the warning buzzer  59  (step S 28 ) and displays a warning message to the liquid crystal display  8  (step S 29 ). Thereafter, the control unit  50  repeats steps S 11  onwards. 
     When the stop operation is operated on the start/stop switch  7  the control unit  50  makes a YES judgment in step S 15  and stops the drive of the sewing machine motor  56  (step S 20 ). 
     Next, a description will be given on the safety operation carried out in accordance with the above configuration. 
       FIG. 9  illustrates image data GD 0  captured immediately before the start operation of the start/stop switch  7 . The image data GD 0  does not contain any moving object  73  such as user&#39;s fingers whatsoever but only contains a portion of the workpiece cloth W, the presser foot  11 , the sewing needle  6  and a portion of the presser bar  10 . The image data GD 0  is stored in the flash memory  54 . 
       FIG. 10  illustrates image data GD 1  captured after start operation of the start/stop switch  7  and the start of normal pattern sewing. The image data GD 1  contains user&#39;s fingers as moving objects  73  in addition to a portion of the workpiece cloth W, the presser foot  11 , the sewing needle  6  and a portion of the presser bar  10 . In the image data GD 1 , the presser foot  11  is consistently placed in a substantially fixed position and the workpiece cloth W is moved horizontally in the sewing direction intermittently. Also, the presser bar  10  and the sewing needle  6  are vertically driven with regularity. Thus, the portion of workpiece cloth W, the presser foot  11 , the sewing needle  6  and the portion of the presser bar  10  are excluded from the moving object  73  detected by the moving object detection process. 
     On the other hand, objects such as user&#39;s fingers and hands have no regularity in their motion. Thus, such objects with no regular motion are detected as a moving object  73  by the moving object detection process. The state illustrated by  FIG. 10  has a proximity distance L 1  greater than 50 mm, thus, there is no possibility of the moving object  73  contacting the sewing needle  6 , therefore no warning operation (activation of the warning buzzer  59 , display of warning message, and the like) is executed whatsoever. 
       FIG. 11  illustrates image data GD 2  captured during the sewing operation. The image GD 2  contains user&#39;s fingers in addition to the objects excluded from moving objects  73  in the moving object detection process. In the state illustrated in  FIG. 11 , since the proximity distance L 2  is approximately 15 mm, it is highly probable that the moving object  73  will contact the sewing needle  6 . Thus, the rotational speed of the sewing machine motor  56  is decelerated, the warning buzzer  59  is activated and the warning message is displayed to the liquid crystal display  8 . This leads to improvement in safety since the user is allowed to avoid danger by retracting his/her fingers. 
     Though not shown, when user&#39;s fingers approach the immediate proximity of the needle drop position N of the sewing needle  6  (within several mm for example), the sewing machine motor  56  is brought to an emergency halt and the warning buzzer  59  is activated to announce the emergency halt of the sewing machine and the warning message is displayed to the liquid crystal display  8 . Thus, user safety is improved since the user is allowed to avoid danger by immediate retraction of his/her fingers. 
     As described above, according to the present embodiment, when moving objects  73  such as user&#39;s fingers approach the sewing needle  6  during the sewing operation, an image of the sewing needle  6  and the moving object  73  in close proximity of the sewing needle  6  are captured, based upon which the distance between the sewing needle  6  and the moving object  73  is calculated as the proximity distance D. Then, if the calculated proximity distance D is equal to or less than the predetermined distance, the predetermined safety operation is executed. Thus, when user&#39;s fingers or the like approach the sewing needle  6 , user safety can be secured reliably. 
     In such case, mere provision of a single imaging sensor  9  allows wide-range detection of a moving object  73  approaching the sewing needle. Hence, considerable enhancement of user safety can be achieved. Furthermore, the configuration of the present disclosure is easy to install, provides good workability, is cost saving and allows compact spacing. Thus, user safety can be secured reliably when user&#39;s fingers or the like approach the sewing needle  6 . 
     In case the calculated proximity distance D is equal to or less than the predetermined distance, the predetermined safety operation is executed based on the result of the step-by-step judgment of the value of the proximity distance D. According to such configuration, the safety operation and the sewing operation can be executed simultaneously by controlling the sewing machine motor  56  to decelerate to a predetermined speed or lower or to stop based on the magnitude of proximity of the moving object  73  to the sewing needle  6 . That is, in case the sewing needle  6  and the moving object  73  are distant, in other words, in case the proximity distance D is of substantial amount, the sewing operation can be continued with the sewing machine motor  56  decelerated to a state allowing immediate halt, thereby allowing execution of the sewing process while preparing for execution of the safety operation. On the other hand, if the moving object  73  is in immediate proximity of the sewing needle  6 , in other words, if the proximity distance D is extremely small, the sewing machine motor  56  may be brought to an emergency halt to stop the sewing process and prioritize the execution of the safety operation. 
     Since the vertical movement of the needle bar  5  is stopped by the release operation of the needle-bar release mechanism  30 , the vertical movement of the needle bar  5  can be stopped immediately even when the sewing machine motor  56  is idle. Thus, the safety of the moving object  73  can be improved even if the moving object  73  is in immediate proximity of the sewing needle  6 . 
     Activation of the warning buzzer  59  and displaying of warning messages to the liquid crystal display  8  allow user perception of the approach of the moving object  73  to the sewing needle  6 , thereby enabling quick avoidance of dangerous situations. 
     Next, a second embodiment arrived by partially modifying the safety control (refer to  FIGS. 8A ,  8 B and  8 C) of the above described first embodiment will be described with reference to  FIGS. 12A and 12B . 
     The present embodiment is arranged to execute a predetermined safety operation when the time taken for the moving object  73  to enter the vertical moving locus (area in which the sewing needle  6  vertically reciprocates) of the sewing needle  6 , in other words, the time taken for the moving object  73  to reach the needle drop position N of the sewing needle  6  is short. Referring to  FIG. 12A , the control unit  50  initially executes steps S 41  to S 48  when this control is started. Steps S 41  to S 48  correspond to steps S 11  to S 18  of the first embodiment. 
     If a moving object  73  is detected in step S 48  (YES), the control unit  50  proceeds to step S 49  and calculates the time taken for the moving object  73  to reach the needle drop position N as an arrival time T. The arrival time T is calculated based on the moving speed of the moving object  73  and the distance between the position of the moving object  73  to the needle drop position N of the sewing needle  6 . Also, the moving speed of the moving object  73  is obtained based on the time interval between each imaging process (imaging interval) when the control unit  50  executes plurality instances of the imaging process (step S 46 ) and the distance (moving distance) traveled by the moving object  73  between the imaging intervals. 
     Next, the control unit  50  proceeds to step S 50  of  FIG. 12B  and the value of the arrival time T is judged in a step-by-step manner. Then, the predetermined safety operation is executed based on the result of the judgment of the arrival time T. If the arrival time T is greater than two seconds (T&gt;2), in other words, if the time taken for the moving object  73  to contact the sewing needle  6  is long, the control unit  50  repeats steps  45  onwards. If the arrival time T is equal to or less than 2 seconds and greater than 1 second (2 seconds≧T&gt;1 second), the control unit  50  proceeds to step S 51  and warns the user by the warning buzzer  59 . 
     If the arrival time T is equal to or less than 1 second and greater than 0.1 second (1 second≧T&gt;0.1 second), the control unit  50  proceeds to step S 52  and executes the deceleration process that decelerates the rotational speed of the sewing machine motor  56  to a predetermined speed. Then, the control unit  50  warns the user by activating the warning buzzer  59  (step S 53 ) and displays a warning message to the liquid crystal display  8  (step S 54 ). 
     If the arrival time T is equal to or less than 0.1 second (T≦0.1 second), in other words, if the moving object  73  reaches the proximity of the sewing needle  6  in a short time, the control unit  50  proceeds to step S 55  and executes a release operation of the needle bar  5 . In the release operation, the needle bar  5  is released via the needle-bar release mechanism  30  by driving the drive motor  40 . Next, the control unit  50  proceeds to step S 56  and brings the sewing machine motor  56  to an emergency halt. Then, the control unit  50  warns the user of the emergency halt by activating the warning buzzer  59  (step S 57 ) and displays a warning message to the liquid crystal display  8  (step S 58 ). Thereafter, the control unit  50  repeats steps S 41  onwards. 
     As described above, according to the present embodiment, the time taken for the moving object  73  to enter the vertical movement locus is calculated as arrival time T based on the image data containing the sewing needle  6  and the moving object  73  in close proximity of the sewing needle  6 . In case the calculated arrival time T is equal to or less than the predetermined time, the predetermined safety operation is executed. Thus, when foreign objects such as user&#39;s fingers approach the sewing needle  6 , user safety can be secured reliably. 
     In the present embodiment also, considerable enhancement of user safety can be achieved by mere provision of a single image sensor  9 . Further, user safety can be secured reliably when foreign objects such as user&#39;s fingers approach the sewing needle  6  with a configuration which is easy to install, provides good workability in low cost and compact spacing. 
     The predetermined safety operation is executed based on the result of the step-by-step judgment of the value of the arrival time T. Thus, the safety operation and the sewing operation can be executed simultaneously based on the magnitude of proximity of the moving object  73  to the sewing needle  6 . In other words, in case the arrival time T is of substantial amount, the sewing process may be executed while preparing for execution of the safety operation. On the other hand, if the arrival time T is extremely short, the sewing operation may be stopped to prioritize the execution of the safety operation. 
     The present disclosure is not limited to the foregoing embodiments but may be modified or expanded as follows. 
     A danger zone may be designated in areas where user safety may be hindered in the safety control indicated in  FIGS. 8A ,  8 B and  8 C and the predetermined safety control may be executed when a moving object  73  enters the predetermined danger zone. More specifically, a step may be introduced in which the control unit  50  judges whether or not a moving object  73  has entered the predetermined danger zone based on the image data captured in step S 11  when the start operation is operated on the start/stop switch  7  (YES in step S 12 ). Then, when the control unit  50  determines that the moving object  73  has entered the danger zone, the warning buzzer  59  may be activated and a warning may be displayed on the liquid crystal display  8 . 
     The image sensor  9  is not limited to a CCD image sensor but may employ a CMOS image sensor and other various imaging elements. 
     The foregoing description and drawings are merely illustrative of the principles of the present disclosure and are not to be construed in a limited 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 disclosure as defined by the appended claims.