sewing machine

Abstract

Sewing machine (100) which forms a stitch by catching a loop of an upper thread (U) formed by a sewing needle (13) below a stitch plate (11) using a catching element (191), the sewing machine (100) comprising: a stitch release device (40) which causes the loop of the upper thread (U) to avoid passing through a position in which the catching element (191) catches the loop of the upper thread (U), the loop being formed after the sewing needle (13) has passed through a lower dead center in an upward and downward movement.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a sewing machine which can prevent the formation of a stitch from a loop of an upper thread formed by a sewing needle. State of the art

[0002] A sewing operation of a sewing machine is performed by interlacing an upper thread with a lower thread to form a stitch when needed. Specifically, a sewing needle having an upper thread passed through a needle eye passes through a fabric to protrude downward from the fabric and then moves upward. As the sewing needle, reaching a bottom dead center, moves upward, the upper thread below the fabric undergoes slack, and then a loop of the upper thread is formed. At the same time, a shuttle, which rotates in synchronization with an up / down movement of the sewing needle, catches the upper thread forming the loop with a blade tip at a position where the sewing needle has moved upward slightly beyond the bottom dead center.The shuttle rotates, a thread take-up lever moves upward at a position where the blade tip passes a predetermined position to cause the shuttle to pass through the loop of the upper thread, and the lower thread reaching the fabric from a bobbin case is entwined with the upper thread to form a stitch.

[0003] In the prior art sewing machine, when the shuttle is caused to pass through the loop of the upper thread caught by the shuttle, the occurrence of a stitch skip in which no knot is formed between the upper thread and the lower thread is detected by optically detecting whether the loop crosses the bobbin case by means of a photoelectric detector (see, for example, JP 2000-197 786 A).

[0004] DE 10 2010 043 760 A1 discloses an automatic jump testing device for a sewing machine. EP 1 367 168 A1 describes a double-needle sewing machine for forming a square seam on a fabric. Summary of the invention

[0005] The prior art sewing machine can detect the occurrence of a skipped stitch; however, it is difficult to stop the sewing machine immediately upon detection of the skipped stitch and to prevent the formation of a stitch after the skipped stitch occurs.

[0006] When a stitch is formed after a skipped stitch occurs, the next stitch is formed in a state where no knot is formed at the skipped stitch occurrence position. Consequently, a position where a stitch pitch is large is generated, greatly deteriorating sewing quality. As a result, when a stitch is formed after a skipped stitch occurs, the threads must be untied and the sewing process must be performed again. In addition, if an unnecessary stitch is formed, the surface of a sewing object will be damaged by the tightening of the knot of the stitch, and the sewing object may be wasted.

[0007] An object of the present invention is to reduce the formation of an unnecessary stitch. (1) A sewing machine according to the present invention is a sewing machine that forms a stitch by catching a loop of an upper thread formed by a sewing needle below a needle plate using a catching member. The sewing machine includes a stitch-escape device. The stitch-escape device causes the loop of the upper thread to avoid passing through a position where the catching member catches the loop of the upper thread, the loop being formed after the sewing needle passes through a bottom dead center in an up-and-down motion. (2) In the sewing machine according to (1), the stitch exhaust device comprises a blowing nozzle which blows air toward the loop of the upper thread formed by the sewing needle in order to avoid passage through the position at which the catching member catches the loop of the upper thread. (3) In the sewing machine according to (2), the blowing nozzle blows air downstream in an operating direction in which the catching member catches the loop of the upper thread. (4) In the sewing machine according to any one of (1) to (3), the sewing machine further comprises a stitch skip detection device and a control unit. The stitch skip detection device detects a stitch skip. The control unit causes the stitch skip device to perform a stitch skip operation at a stitch point upon detection of a stitch skip by the stitch skip detection device. (5) In the sewing machine according to (4), when a stitch skip is detected by the stitch skip detecting device, the control unit stops the drive of a sewing machine motor which is a sewing drive source and causes the stitch skip device to perform the stitch skip operation until the sewing needle stops the upward and downward movement. (6) In the sewing machine according to (4) or (5), the stitch escape detecting device comprises an optical sensor which determines whether the loop of the upper thread passes through a passing position of the loop of the upper thread which is detected by the catching member.

[0008] According to the present invention, since a loop of an upper thread formed after passing through a bottom dead center can be brought close to a position deviating from a catching position of a catching member by the stitch omission device, it is possible to actively generate a stitch omission when necessary.

[0009] When an unintentional stitch skip occurs, it is possible to suppress the formation of a stitch after the occurrence of the skip by performing a skip operation. Accordingly, it is possible to reduce re-stitching or waste of a sewing object due to the occurrence of a skip. Short description of the characters Fig. 1 is a perspective view showing the vicinity of a needle locating position in a sewing machine according to an embodiment of the present invention. Fig. 2 is a block diagram showing a control system of the sewing machine. Fig. 3A is a diagram showing a relationship between a loop of an upper thread and a moving locus of a reed tip, and Fig. Figure 3B is a diagram showing the appropriate arrangement of a blowing nozzle. Fig. 4A is a diagram showing a relationship between a loop of an upper thread and a catching position of a reed tip, and Fig. Figure 4B is a diagram showing a loop state by appropriately blowing air. Fig. 5 is a flowchart showing a stub outlet detection process. Fig. 6 is a flowchart showing a stub outlet execution control. Detailed descriptionOverall configuration of the sewing machine

[0010] Hereinafter, a sewing machine 100 according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a perspective view showing the vicinity of a throat plate 11 of the sewing machine 100, showing a state in which a slide plate adjacent to the throat plate 11 is removed to reveal a shuttle mechanism therein. Fig. 2 is a block diagram showing a control system of the sewing machine 100.

[0011] As in Fig. 1 and Fig. 2, the sewing machine 100 includes a sewing machine frame serving as a housing, a needle up-down movement mechanism that causes a sewing needle 13 to move up and down at a tip of an arm of the sewing machine frame, a shuttle mechanism that forms a stitch in cooperation with the needle up-down movement mechanism, a feed mechanism that performs an operation of feeding a sewing material as a sewing object using a feed dog 14 in synchronization with the up-and-down movement of the sewing needle 13, a stitch skip detection device 30 that detects the occurrence of a stitch skip, a stitch skip device 40 that generates a stitch skip, and a control unit 90 that controls operations of elements of the sewing machine.

[0012] In addition to the above-mentioned configuration, the sewing machine 100 includes various necessary mechanisms; however, these mechanisms are the same as known configurations and are therefore not described in this embodiment.

[0013] In describing the sewing machine 100, an upper side in a vertical direction is referred to as "top", a lower side in the vertical direction is referred to as "bottom", a downstream side in a fabric feeding direction in a horizontal direction is referred to as "front", an upstream side in the fabric feeding direction is referred to as "rear", a left side in a state where the sewing machine faces the rear side in the horizontal direction is referred to as "left", and a right side is referred to as "right". sewing machine frame

[0014] The sewing machine frame includes a bed (sewing machine bed) having a horizontal bed surface on which a work fabric is placed, an upright body arranged to project upward from one end of the bed, and an arm (sewing machine arm) extending from the upper part of the upright body substantially parallel to the bed, the bed and arm extending in the right-left direction. The needle up-down movement mechanism is incorporated into the tip of the arm, and the shuttle mechanism, the feed mechanism, the stitch exit detection device 30, and the stitch exit device 40 are incorporated into the bed. Needle up-down movement mechanism

[0015] The needle up-and-down movement mechanism includes an arm shaft as a sewing machine main shaft (not shown), which rotatably extends in the arm and is connected to a sewing machine motor 12, a crank mechanism formed at a tip of the arm shaft, a needle bar which is driven to move up and down by the crank mechanism and extends in the vertical direction, and a sewing needle 13 supported at a lower end of the needle bar. When the arm shaft rotates by driving the sewing machine motor 12, the rotation is converted into an up-and-down movement by the crank mechanism and transmitted to the needle bar. Accordingly, the needle bar and the sewing needle 13 perform an up-and-down movement corresponding to a time of reciprocating movement with respect to one revolution of the arm shaft. Transport mechanism

[0016] The feed mechanism uses the sewing machine motor 12 as a drive source, converts a torque of the sewing machine motor 12 into an up-and-down motion and a forward-and-backward motion, and combines the motions to impart an elliptical motion in the front-to-back direction to the feed dog 14. Through this elliptical motion, the feed dog 14 causes a tooth tip thereof to protrude and retract vertically through an opening formed in the throat plate 11 and move forward in the feed direction to shift a fabric placed on the upper surface of the throat plate 11 toward the front at a predetermined pitch when the tooth tip protrudes from the upper surface of the throat plate 11. Shuttle mechanism

[0017] As in Fig. 1, the shuttle mechanism includes a horizontal shuttle 15, a shuttle shaft base 17 which rotatably supports a shuttle shaft 16 along the vertical direction, and a transmission mechanism which transmits a torque of the sewing machine motor 12 to the shuttle shaft 16.

[0018] The horizontal shuttle 15 includes a center shuttle 18 that accommodates a bobbin around which a bobbin thread is wound, and an outer shuttle 19 that rotates together with the shuttle shaft 16 on the outer periphery of the bobbin case and the center shuttle 18. The center shuttle 18 includes a rotation stopper that mates with a recessed portion of the needle plate 11 and maintains a stopped state with respect to the rotation of the outer shuttle 19 during sewing.

[0019] The transmission mechanism transmits the rotation to the shuttle shaft 16 at twice the speed of the arm shaft. This means that the outer shuttle 19 performs two revolutions with respect to one needle location.

[0020] The horizontal shuttle 15 is arranged on the right side of a needle hole 20. The outer shuttle 19 includes, on its outer periphery, a blade tip 191 as a catching member for capturing a loop of an upper thread U formed by the sewing needle 13. The blade tip 191 is arranged to pass in the vicinity of the right side of the stitching point position. The outer shuttle 19 receives rotation in a direction F to move backward when the blade tip 191 passes in the vicinity of the stitching point position. The blade tip 191 is formed in a shape that tapers towards the rear.

[0021] When the sewing machine motor 12 is driven, the shuttle shaft 16 and the outer shuttle 19 rotate at twice the up / down movement speed of the needle, the loop of the upper thread U formed by the sewing needle 13 passing through the bottom dead center is caught by the blade tip 191 of the outer shuttle 19, the middle shuttle 18 is caused to pass through the loop of the upper thread U, and the lower thread drawn from the bobbin is inserted into the loop of the upper thread U. By causing a thread take-up lever to pull the upper thread U upward, the upper thread U and the lower thread are intertwined with each other to form a knot in the fabric. Stitch outlet detection device

[0022] As in Fig. 2, the stitch skip detection device 30 includes a light emitter 31 which emits light of a predetermined wavelength, a drive unit 32 thereof, a light receiver 33 which receives and detects the light having the predetermined wavelength from the light emitter 31, and a signal amplifier 34 which amplifies a detection signal from the light receiver 33, and detects the occurrence of stitch skip by optically detecting whether the loop of the upper thread U caught by the horizontal shuttle 15 passes in the vicinity of the upper surface of the middle shuttle 18.

[0023] As described above, in the horizontal shuttle 15, the blade tip 191 of the outer shuttle 19 catches a loop based on a slack of the upper thread U formed by the sewing needle 13 passing through the bottom dead center and moving upward again, and inserts the lower thread into the loop of the upper thread U by causing the loop to pass the middle shuttle 18 with the bobbin while pulling and enlarging the loop.

[0024] In this operation, one end of the upper thread U is in the needle hole 20 and the other end thereof moves in the direction F along a circular outer peripheral edge of the upper surface of the middle shuttle 18. That is, the other end of the upper thread U moves from a position in the vicinity of the needle hole of the circular outer peripheral edge of the upper surface of the middle shuttle 18 to a position farthest from the outer peripheral edge.

[0025] An optical path L1 from the light emitter 31 to the light receiver 33 in the stitch exit detection device 30 is configured to pass slightly above the upper surface of the center shuttle 18 along a plane perpendicular to the shuttle shaft 16 of the horizontal shuttle 15 while passing through the passing area of ​​the upper thread U. That is, the light emitter 31 and the light receiver 33 are mounted on the shuttle shaft base 17 with the horizontal shuttle 15 interposed between them, such that the optical path L1 passes through the position that is a certain degree farther from the needle hole 20 than the shuttle shaft 16 along the front-back direction.

[0026] The light receiver 33 can be arranged in the same direction at the same position as the one shown in Fig. 1 shown light emitter 31; at the position of the light receiver 33 of Fig. 1, a mirror may be arranged and the light receiver 33 may receive reflected light of the light emitted by the light emitter 31.

[0027] When the light emitter 31 and the light receiver 33 are arranged at the two ends of the optical path L1, the upper thread U, which crosses the outer peripheral edge of the upper surface of the middle shuttle 18 from the needle hole 20, forcibly passes through the optical path L1.

[0028] The control unit 90, which controls the stitch skip detection device 30, monitors a known arm shaft angle at which the upper thread U is caught by the sewing needle 13 and the loop is drawn by the horizontal shuttle 15, using an encoder 21 that detects an arm shaft angle, and detects the occurrence of a stitch skip depending on whether a detection signal of the upper thread U is input from the light receiver 33 within a predetermined angle range (referred to as the needle thread detection range) including the arm shaft angle. That is, if the passage of the upper thread U is not detected by the light receiver 33, it is understood that a stitch skip is occurring. Branch outlet device

[0029] As in Fig. 1 and Fig. 2, the stitch exhaust device 40 includes a blowing nozzle 41 which blows air toward a loop of the upper thread U formed by the sewing needle below the needle plate 11 in a direction in which the loop deviates from the catching position of the reed tip 191 of the outer shuttle 19, a solenoid valve 42 which switches the blowing nozzle 41 into an air supply and an air supply stop state, and a drive circuit 43 which actuates the solenoid valve 42.

[0030] The arrangement and direction of the nozzle 41 will be described below with reference to Fig. 3A and Fig. 3B and Fig. 4A and Fig. 4B.

[0031] Fig. 3A and Fig. 3B show in plan view a state in which the sewing needle 13 passing through the bottom dead center and rising again forms a loop of the upper thread U, and Fig. 4A and Fig. 4B show the state in a front view. The reference symbol K in Fig. 3A and Fig. 3B denotes a movement locus of the blade tip 191 of the outer shuttle 19 and the reference symbol P in Fig. 4A and Fig. 4B indicates a catching position of the loop of the upper thread U by the blade tip 191.

[0032] The loop of the upper thread U is formed by a slack of the upper thread U to the shuttle side of the sewing needle 13 due to the upward movement of the sewing needle 13, and the blade tip 191 of the outer shuttle 19 is positioned to enter its movement locus K when the upper thread U has a slack ( Fig. 3A) and the catch position P of the blade tip 191 is within the loop ( Fig. 4A).

[0033] The blowing nozzle 41 is arranged in a direction in which air is blown from a position near the horizontal shuttle on the front side of the sewing needle 13 toward the sewing needle 13. The blowing nozzle 41 can bend the loop of the upper thread U formed on the shuttle side of the sewing needle 13 by blowing air in this direction and arranging it toward the rear side, and the loop of the upper thread U is ejected to the outside of the moving locus K of the blade tip 191 of the outer shuttle 19 ( Fig. 3B), and the catch position P of the blade tip 191 is outside the loop ( Fig. 4B). Accordingly, the upper thread U is prevented from being caught by the reed tip 191, no knot is formed at the stitch point, and thus a stitch skip occurs.

[0034] The solenoid valve 42 is formed in the middle of an air supply path from a high-pressure air source to the blowing nozzle 41, and an ON state and an OFF state are switched by the control unit 90 via the drive circuit 43.

[0035] The control unit 90 monitors the known arm shaft angle at which the blade tip 191 of the outer shuttle 19 passes through the catching position of the loop of the upper thread U, using the encoder 21 which detects the arm shaft angle, and controls the electromagnetic valve 42 to supply air to the blowing nozzle 41 only within a predetermined angle range (referred to as the stitch discharge execution range) including the arm shaft angle of the catching position. Sewing machine control system

[0036] As in Fig. 2, in the sewing machine 100, the drive circuit 12a for driving the sewing machine motor 12, the counter circuit 21a of the detection signal of the encoder 21 which detects the arm shaft angle, the drive unit 32 of the light emitter 31 of the stitch outlet detecting device 30, the signal amplifier 34 of the light receiver 33, and the drive circuit 43 of the electromagnetic valve 42 which controls the air blowing operation of the stitch outlet device 40 are connected via an interface not shown.

[0037] Encoder 21 outputs two types of phase signals indicating an arm shaft angle. An encoder A phase signal output by encoder 21 is a minimum unit signal, and a pulse is output every time the arm shaft angle changes by 1°. An encoder Z phase signal output by encoder 21 is a pulse signal, with one period corresponding to one revolution of the arm shaft.

[0038] The control unit 90 can detect the arm shaft angle by counting the number of pulses of the encoder A-phase signal with the encoder Z-phase signal as the origin.

[0039] The control unit 90 is a microprocessor which includes a memory (not shown) in which programs for performing various processes or controls or data used in the programs are stored, and which performs various controls based on the programs.

[0040] By executing a program, the control unit 90 performs a stub outlet detection process and a stub outlet execution control.

[0041] The stitch skip detection process is a process for detecting the occurrence of a stitch skip by means of the stitch skip detection device 30 during sewing, and is repeatedly executed in a predetermined cycle during sewing.

[0042] The stitch skip execution control is a control for quickly stopping the sewing machine motor 12 when the occurrence of stitch skip is detected in the stitch skip detecting process, repeating stitch skip for each needle using the stitch skip device 40 until the arm shaft stops completely, and preventing the formation of a stitch after the occurrence of the stitch skip. Stitch outlet detection process

[0043] The stub outlet detection process performed by the control unit 90 will be described below with reference to the Fig. The flowchart shown in Figure 5 is described.

[0044] First, when starting the puncture outlet detection process, the control unit 90 turns off a puncture outlet detection flag (step S1).

[0045] The A / D of the control unit 90 converts the output signal of the light receiver 33 and detects the resulting signal as a sensor value (step S3).

[0046] Then, the control unit 90 calculates the arm shaft angle based on the encoder A phase signal and the encoder Z phase signal, and turns on the stitch skip detection flag (step S7) if the arm shaft angle is within the upper thread detection range (YES in step S5). If the calculated arm shaft angle is not within the upper thread detection range, the determination result in step S5 is NO, the determination result in step S15 is NO, and the process flow returns to step S3.

[0047] When the upper thread U passes through the horizontal shuttle 15 and the upper thread U interrupts the optical path L1 between the light emitter 31 and the light receiver 33, the amount of light input to the light receiver 33 decreases. When the output signal of the light receiver 33 decreases, the control unit 90 determines that the upper thread U is detected.

[0048] Based on the sensor value in the upper thread detection range, the control unit 90 determines whether the upper thread U is detected (step S9), and turns off the stitch skip detection flag (step S11) when the upper thread U is detected (YES in step S9). After detecting the upper thread, the process flow is looped if the arm shaft angle is within the upper thread detection range (YES in step S13), the process flow returns to step S3 if the arm shaft angle deviates from the upper thread detection range (NO in step S13), and until the arm shaft angle enters the upper thread detection range, the determination result of step S5 is NO, the determination result of step S15 is NO, and the process flow returns to step S3.

[0049] On the other hand, when the upper thread U is not detected within the upper thread detection range and the arm shaft angle deviates from the upper thread detection range, the stitch skip detection flag is turned on in step S7, the determination result of step S9 is NO, the process flow returns to step S3, the determination result of step S5 is NO, and the process flow proceeds to step S15.

[0050] In step S15, it is determined whether the stitch omission detection flag is on or off, and if the stitch omission detection flag is on, it is determined in step S17 that stitch omission occurs.

[0051] When the control unit 90 includes an operation panel having a display function and detects the occurrence of a stitch omission, notification control for displaying the occurrence of a stitch omission on the operation panel may be performed. Stub outlet execution control

[0052] The stab outlet execution control performed by the control unit 90 will be described below with reference to the Fig. The flowchart shown in Figure 6 is described.

[0053] First, the control unit 90 determines whether occurrence of a stitch omission is detected in the above-mentioned stitch omission detecting process (step S21), and terminates the stitch omission execution control when occurrence of a stitch omission is not detected.

[0054] When occurrence of stitch skipping is detected, the sewing machine motor 12 is controlled to stop (step S23).

[0055] Next, the control unit 90 determines whether the arm shaft completely stops rotating based on the encoder A phase signal from the encoder 21 (step S25). For example, in this determination, a count value of a current pulse of the encoder A phase signal is recorded and compared with the previous recording to determine whether the count value varies. If the count value varies, the arm shaft continues to rotate due to inertia. If the count value does not vary, it is determined whether the non-varying state is maintained for a prescribed time. If the non-varying state is maintained for the prescribed time, it is determined that the arm shaft completely stops.

[0056] If it is determined in step S25 that the arm shaft does not stop completely, the control unit 90 determines whether the current arm shaft angle is within the stub outlet execution range based on the count values ​​of the encoder A phase signal and the encoder Z phase signal from the encoder 21 (step S27).

[0057] It is therefore understood that when the arm shaft angle is within the stitch skip execution range, the sewing needle 13 forms or has formed a loop of the upper thread U at a stitching point following the stitch skip point. Accordingly, by turning on the electromagnetic valve 42 to blow air from the blowing nozzle 41 and retract the loop with a wind pressure, the loop is ejected from the range of the moving locus K of the blade tip 191 of the outer shuttle 19 (to a position deviating from the tuck position P) (step S29). Then, the process flow returns to step S25.

[0058] When the arm shaft angle deviates from the stitch exit execution range, the sewing needle 13 does not form a loop of the upper thread U, and thus the solenoid valve 42 is switched to the OFF state or maintained in the OFF state (step S31). Then, the process flow returns to step S25.

[0059] In step S25, it is again determined whether the arm shaft completely stops rotating. If the arm shaft does not stop rotating, the process of determining whether the arm shaft angle is within the sting discharge execution range is performed in step S27. If the arm shaft completely stops rotating, the sting discharge execution control is terminated. If air blowing is occurring at this time, the solenoid valve 42 is controlled to stop the air blowing. Technical advantages of the embodiment

[0060] As described above, the sewing machine 100 is a sewing machine which catches a loop of an upper thread U formed by the sewing needle 13 below the throat plate 11 using the reed tip 191 as a catching member to form a stitch, and which includes the stitch discharging device 40 which causes the loop of the upper thread U formed after the sewing needle 13 passes through the bottom dead center in an up-and-down movement to retreat from the moving locus K of the reed tip 191 (to come close to a position deviated from the catching position P).

[0061] Accordingly, it is possible to actively perform a stub outlet operation if necessary.

[0062] The stitch outlet device 40 of the sewing machine 100 comprises the blowing nozzle 41, which blows out air in a direction in which the loop of the upper thread U formed by the sewing needle 13 deviates from the area of ​​the movement locus K of the blade tip 191.

[0063] Accordingly, it is possible to realize the operation of retracting the loop of the upper thread U in a predetermined direction in a non-contact state of the upper thread U or the sewing needle 13, to avoid a situation in which the upper thread U is caught or needle breakage is caused due to contact with the sewing needle 13, and to reduce the occurrence of a situation in which a sewing operation is prevented from realizing stable sewing.

[0064] Since air is blown out, the blowing nozzle 41 can be arranged separately from the sewing needle 13 to avoid the vicinity of a needle locating position where various elements are concentrated and which is very narrow, and it is easily possible to ensure a formation space of the blowing nozzle 41.

[0065] Since the blowing nozzle 41 of the stitch discharging device 40 faces the downstream side in the operating direction, when the blade tip 191 catches a loop of the upper thread U and blows air substantially toward the rear, the loop of the upper thread U falls in a direction in which the loop is spaced apart from the blade tip 191. For example, even when the blade tip 191 moves to the catching position at high speed, it is possible to retract the loop more satisfactorily and thus realize stitch discharging more satisfactorily.

[0066] The sewing machine 100 includes the stitch skip detection device 30 which detects the occurrence of a stitch skip, and the control unit 90 which causes the stitch skip device 40 to perform a stitch skip operation at a next stitch point after a stitch skip is detected by the stitch skip detection device 30.

[0067] Accordingly, when an inadvertent puncture omission occurs, it is possible to avoid the formation of a puncture due to subsequent needle localization.

[0068] Since the formation of an unnecessary stitch after a stitch skip is avoided, it is possible to prevent a thread pull mark due to a knot formed in a work piece in which a stitch skip occurs, and to reduce the number of pieces of work piece wasted due to the skip. Even if a work piece is not wasted due to the skip, it is possible to reduce the labor required to unravel the unnecessary stitch after the skip, thus reducing the workload.

[0069] When a stitch skip is detected by the stitch skip detecting device 30 in the stitch skip execution control, the control unit 90 stops the drive of the sewing machine motor 12 as a sewing drive source and executes a stitch skip operation using the stitch skip device 40 until the up-and-down movement of the sewing needle 13 stops.

[0070] Accordingly, it is possible to more effectively reduce the formation of an unnecessary stitch after a stitch omission occurs.

[0071] Since the stitch skip detecting device 30 includes the light emitter 31 and the light receiver 33 as an optical sensor that detects passage of the loop through the passing position of the loop of the upper thread U detected by the blade tip 191 of the outer shuttle 19 (the light emitter 31 and the light receiver 33 as an optical sensor that determines whether the loop passes through the passing position of the loop of the upper thread U detected by the blade tip 191 of the outer shuttle 19), it is possible to efficiently detect the occurrence of stitch skip in a non-contact manner.

[0072] In the stitch skip detection device 30, by arranging the light emitter 31 and the light receiver 33 to form an optical axis L1 in the vicinity of the upper surface of the center shuttle 18, it is possible to extend the time required for the detected loop of the upper thread U to pass through the optical axis L1 as much as possible. Since the detection signal from the light receiver 33 can be easily distinguished from noise, it is possible to detect the occurrence of a stitch skip with high accuracy.

[0073] In particular, by disposing the optical axis L1 on the side farther from the needle hole 20 than the shuttle shaft 16, it is possible to further lengthen the time required for the detected loop of the upper thread U to pass through the optical axis L1 and thereby detect the occurrence of stitch skipping with higher accuracy.

[0074] By using scattered light as the light emitted from the light emitter 31 and causing a light-receiving surface of the light receiver 33 to have a vertical width, it is possible to further lengthen the time required for the detected loop of the upper thread U to pass through the optical axis L1 and thereby detect the occurrence of stitch skipping with higher accuracy. Miscellaneous

[0075] In the sewing machine 100, the horizontal shuttle 15 is used as an example; however, there are no restrictions on the type of shuttle used to implement stitch skipping. For example, even with a vertical shuttle or a semi-rotary shuttle, a loop of an upper thread is caught by a reed tip to form a knot. Accordingly, when the loop of the upper thread U is retracted to deviate from a thread catching position of the reed tip of the shuttle, the stitch skipping device can implement stitch skipping in a similar manner to the horizontal shuttle 15.

[0076] A stitch skip operation can also be performed by applying the stitch skip device to a sewing machine that performs a sewing operation by catching a loop of an upper thread U using a tip of a looper instead of the shuttle. That is, it is possible to realize a stitch skip by retracting the loop to deviate from the upper thread catching position of the looper.

[0077] The stitch skip detection device 30 is not limited to the horizontal shuttle 15, but can also detect stitch skips with a vertical shuttle, a semi-rotary shuttle, and a looper. The vertical shuttle, the semi-rotary shuttle, and the looper detect a loop of an upper thread U and pull the detected loop to a predetermined position. Accordingly, when the arm shaft angle at the loop pulling position is within a predetermined range, it is possible to detect a stitch skip depending on whether the pulled loop of the upper thread U is optically detected.

[0078] The blowing nozzle 41 of the branch outlet device 40 blows air in the direction of movement of the blade tip 191; however, the blowing direction can also be reversed as long as a blowing timing can be moved forward.

[0079] In the stitch outlet device, a member for retracting a loop of an upper thread U from the catching position of the reed tip is not limited to the blowing nozzle; rather, the loop of the upper thread can also be retracted by pushing the loop in a predetermined direction using a contact member. Installation space must be ensured for the contact member and for an actuator for operating the contact member.

Claims

[1] A sewing machine (100) which forms a stitch by engaging a loop of an upper thread (U) formed by a sewing needle (13) below a needle plate (11) using a catching member (191), the sewing machine (100) comprising: a stitch escape device (40) which causes the loop of the upper thread (U) to avoid passage through a position where the catching member (191) catches the loop of the upper thread (U), the loop being formed after the sewing needle (13) has passed through a bottom dead center in an upward and downward movement. [2] A sewing machine according to claim 1, wherein the stitch exhaust device (40) comprises a blowing nozzle (41) which blows air toward the loop of the upper thread (U) formed by the sewing needle (13) to prevent passage through the position where the catching member (191) catches the loop of the upper thread (U). [3] A sewing machine according to claim 2, wherein the blowing nozzle (41) blows air downstream in an operating direction in which the catching member (191) catches the loop of the upper thread (U). [4] Sewing machine according to one of claims 1 to 3, further comprising: a stitch outlet detecting device (30) which detects a stitch outlet; and a control unit (90) which causes the stitch outlet device (40) to perform a stitch outlet operation at a stitch point after detection of a stitch outlet by the stitch outlet detection device (30). [5] A sewing machine according to claim 4, wherein upon detection of a stitch skip by the stitch skip detecting device (30), the control unit (90) stops the drive of a sewing machine motor (12), which is a sewing drive source, and causes the stitch skip device (40) to perform the stitch skip operation until the sewing needle (13) stops the upward and downward movement. [6] A sewing machine according to claim 4, wherein the stitch exit detecting device (30) comprises an optical sensor (33) which determines whether the loop of the upper thread (U) passes through a passing position of the loop of the upper thread (U) detected by the catching member (191). [7] A sewing machine according to claim 5, wherein the stitch exit detecting device (30) comprises an optical sensor (33) which determines whether the loop of the upper thread (U) passes through a passing position of the loop of the upper thread (U) detected by the catching member (191).

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