Stitch exit and thread break detection device on a sewing machine

Abstract

Stitch skip and thread break detection device (10), intended for use on a sewing machine, for detecting a needle thread (3) by means of a photoelectric sensor (11), wherein the needle thread (3) extends from a sewing machine needle penetrating a fabric, is detected by a tip (1a) of a shuttle (1) and passes through the shuttle (1) to pass through a bobbin thread, thereby detecting stitch skip and thread break, wherein a light path (L1) extending from a light emission part (13) to a light receiving part (15) of the photoelectric sensor (11) is set to pass through the passage area of ​​the needle thread (3) and to cross the shuttle (1) orthogonally to the axis of rotation (A1) of the shuttle (1), and wherein the passage of the needle thread (3) is detected according to the amount of light received by the light receiving part (15).

Description

TECHNICAL FIELD

[0001] The invention relates to a stitch skip and thread breakage detecting device on a sewing machine for detecting a needle thread by means of a photoelectric sensor, wherein the needle thread extends from a sewing machine needle penetrating through a fabric, is caught by the tip of a shuttle, and is passed through the shuttle to pass through a bobbin thread, thereby detecting stitch skip and thread breakage. STATE OF THE ART

[0002] Sewing on a sewing machine is accomplished by intertwining a needle thread and a bobbin thread as needed to form a stitch. Specifically, a sewing machine needle with a needle thread pierces the fabric, protrudes from the underside of the fabric, and then ascends. When the machine needle, which has reached a bottom dead center, begins to ascend, the needle thread is released to form a loop. Simultaneously, a shuttle, which rotates in conjunction with the vertical movement of the machine needle, catches the looped needle thread with its tip at a position where the machine needle has moved upward slightly beyond the bottom dead center. The shuttle rotates, and a balancing device ascends at a position where the tip has passed a certain position, thereby removing the looped needle thread from the shuttle tip and pulling it upward.Thus, the bobbin thread that has left a bobbin case and reached the fabric is entwined with the needle thread to form a stitch.

[0003] In such a sewing process, in some cases, due to a mismatch between the vertical movement of the machine needle and the timing of the shuttle's rotation, or due to the degree of thread tension, etc., the shuttle point fails to pick up the loop. This results in stitch skips, in which one or more stitches are missed. Furthermore, even if the needle thread breaks, no stitch formation occurs.

[0004] In view of the above-mentioned problem, according to a method for detecting skipped stitches in a sewing machine disclosed in JP 2000-197786 A, in a sewing machine in which a needle thread caught by the tip of a shuttle passes once while a sewing machine needle moves vertically once, and in this case, the leading thread portion of the looped needle thread crosses the surface of a bobbin case accommodated in the shuttle, the presence or absence of the crossing leading thread portion is detected in a non-contact manner by means of a photoelectric detector capable of responding to reflected light. To this end, the photoelectric detector is arranged to emit light toward the surface of the bobbin case (in one embodiment, at an angle of approximately 45° to the rotation axis of the shuttle).Furthermore, according to the invention disclosed in JP 2000-197 786 A, the photoelectric detector may preferably be constructed as a photoelectric color difference detector capable of detecting the color of the thread by comparing it with the color of the surface of the bobbin case.

[0005] However, in the invention disclosed in JP 2000-197 786 A, the following problems arise when detecting the passage of the needle thread by means of a reflection-type photoelectric sensor for radiating a light toward the surface of the bobbin case.

[0006] First, because the light is radiated toward the surface of the bobbin case, in a phase limited to the rotation cycle of the shuttle, as the rotation speed of the shuttle increases, the detection time of the needle thread by the photoelectric sensor shortens, thereby increasing the possibility that the sensor fails to detect the actual passage of the needle thread and thus mistakenly determines that the thread has not passed.

[0007] Furthermore, the stitch-leakage detection method of JP 2000-197786 A is difficult to apply to a sewing machine having a horizontal shuttle. A needle plate and a needle plate slider are located in the area opposite (above) the surface of the bobbin case to be accommodated in the horizontal shuttle, making it difficult to position the photoelectric sensor so that it can emit light toward the surface of the bobbin case to be accommodated in the horizontal shuttle.

[0008] Furthermore, because one of the reflected light radiations—the reflected light from the surface of the bobbin case and the reflected light from the passing needle thread—is always received by the photoelectric sensor, the passage of the needle thread must be detected by comparing these reflected light radiations. In JP 2000-197 786 A, the needle passage is detected based on a color difference. Highly sensitive detection requires a dedicated photoelectric sensor, not just a low-cost general-purpose sensor.

[0009] DE 2014 2020 209 A1 discloses a sensor assembly for a sewing machine. DE 30 25 058 A1 discloses a bobbin thread detector device. JP 2002-301 290 A describes a bobbin thread sensor. DE 40 24 846 C1 discloses a sewing machine with a thread monitor for performing a display and / or switching function when a thread fault occurs. EP 1 716 390 B1 discloses a device for the optical analysis, including two-dimensional analysis, of a thread or yarn. A stitch-forming machine with a measuring sensor is described in DE 38 39 733 C2. SUMMARY OF THE INVENTION

[0010] Thus, in a stitch skip and thread breakage detecting device on a sewing machine for detecting a needle thread by means of a photoelectric sensor, wherein the needle thread extends from a sewing machine needle penetrating a fabric, is caught by the tip of a shuttle, and is passed through the shuttle to pass through a bobbin thread, thereby detecting stitch skip and thread breakage, the object of the invention is to facilitate application of the device to a horizontal shuttle, improve the accuracy of stitch skip and thread breakage detection by the device, and enable low-cost realization of the device. The detecting device has one of the following features (1) ~ (6). (1) A stitch skip and thread breakage detecting device for use in a sewing machine for detecting a needle thread by means of a photoelectric sensor, wherein the needle thread extends from a sewing machine needle penetrating a fabric, is caught by the tip of a shuttle, and passes through the shuttle to pass through a bobbin thread, thereby detecting stitch skip and thread breakage, wherein a light path ranging from a light emitting part to a light receiving part of the photoelectric sensor is set to pass through the passage area of ​​the needle thread and traverse the shuttle orthogonal to the rotation axis of the shuttle, and wherein the passage of the needle thread is detected according to the amount of light received by the light receiving part. (2) A stitch-missing and thread-breakage detecting device having the feature recited in (1), wherein, when the two sides of the shuttle are separated by a plane including the rotation axis and the center axis of the sewing machine, the light-emitting part is arranged on the side toward which the tip which has caught the needle thread advances. (3) A stitch-dropping and thread-breakage detecting device having the feature recited in (1) or (2), wherein the optical axis of a light to be emitted from the light-emitting part coincides with the end face of the shuttle which is located on the side opposite to a sub-shaft for transmitting rotational power to the shuttle. (4) A stitch-out and thread-breakage detecting device having the feature listed in any one of (1) to (3), wherein the shuttle is a horizontal shuttle. (5) A stitch omission and thread breakage detecting device having the feature recited in (1) or (2), wherein the light receiving part is constituted by multiple light receiving elements, and wherein the light receiving elements are respectively arranged in different horizontal and vertical positions. (6) A stitch skip and thread breakage detecting device having the feature listed in (5), wherein the multiple light receiving elements detect the amounts of light received by them, respectively.

[0011] According to the stitch dropout and thread breakage detecting device having the feature listed in (1), since the optical path from the light emitting part to the light receiving part of the photoelectric sensor is set to pass through the passage area of ​​the needle thread and traverse the shuttle orthogonally to the rotation axis of the shuttle, the moving direction of the needle thread moving while being caught by the tip of the shuttle and the traversing direction of the light path are brought closer to each other, and the time period in which the light path to the light receiving part is blocked by the needle thread is lengthened, thereby lengthening the detection time of the needle thread by the photoelectric sensor. This improves the accuracy of stitch dropout and thread breakage detection.This further facilitates the application of the photoelectric sensor to the horizontal shuttle by inserting the light path from the light emitting part to the light receiving part into a space between the upper end surface of the horizontal shuttle and a needle plate or the like.

[0012] Furthermore, since detection is performed according to a difference between the amounts of light received when the light path to the light receiving part is blocked and not blocked by the needle thread, sufficient detection accuracy can be provided even when using inexpensive general-purpose light emitting and receiving elements as the photoelectric sensor.

[0013] In the latter half of the shuttle, where the needle thread passes through the shuttle, the behavior of the looped portion of the needle thread is unstable due to the needle thread emerging from the shuttle, compared to the portion where the former half of the needle thread is pulled from the tip. Furthermore, when the light from the light-emitting diode or the like propagates, as the distance from the light-emitting part of the photoelectric sensor to the object to be detected decreases, the shadow cast by the object to be detected becomes larger, making variations in the amount of light received by the light-receiving part clear, thus facilitating the detection of such variations.

[0014] According to the stitch dropout and thread breakage detecting device having the feature listed in (2), in the portion where the former half of the needle thread is pulled from the tip, a light can be emitted from the light emitting part located near the needle thread, and variations in the received light amount can be detected in a stable and unambiguous manner, thereby enabling improvement in the accuracy of the stitch dropout and thread breakage detection.

[0015] In the case where the optical axis of the light emitted from the light-emitting part of the photoelectric sensor is spaced outward from the end face of the shuttle, when the light is irradiated onto the passing needle thread, the shadow of the light is projected onto the shuttle, raising concerns that variations in the amount of received light caused by the passage of the needle thread cannot be sufficiently detected in the light-receiving part. On the other hand, when the optical axis of the light emitted from the light-emitting part of the photoelectric sensor crosses the shuttle, the passing needle thread enters the shadow of the shuttle, raising concerns that variations in the amount of received light caused by the passage of the needle thread cannot be sufficiently detected in the light-receiving part.

[0016] According to the stitch dropout and thread breakage detecting device having the feature listed in (3), since the optical axis of the light emitted from the light emitting part coincides with the end face of the shuttle, neither the shadow of the passing needle thread is projected onto the shuttle nor the passing needle thread enters the shadow of the shuttle; rather, variations in the amount of received light caused by the passage of the needle thread can be sufficiently detected in the light receiving part, thereby enabling improvement in the accuracy of stitch dropout and thread breakage detection.

[0017] According to the stitch-missing and thread-breaking detecting device having the feature listed in (4), the needle thread passing through the horizontal shuttle can be detected by the photoelectric sensor, thereby enabling the stitch-missing and thread-breaking detection.

[0018] According to the stitch dropout and thread breakage detecting device having the feature listed in (5), when the multiple light receiving elements of the light receiving part of the photoelectric sensor are respectively arranged in different horizontal and vertical positions, a light receiving part having a wide detection range can be constructed at low cost.

[0019] According to the stitch skip and thread break detection device having the feature listed in (6), the final detection of stitch skip and thread break can be performed according to the detection results of the multiple light receiving elements, thereby making it possible to improve the accuracy of the stitch skip and thread break detection. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 shows a perspective view of a centered horizontal shuttle portion of a sewing machine including a stitch skip and thread breakage detecting device (hereinafter referred to as stitch skip (etc.) detecting device) according to an embodiment of the invention. Fig. 2 shows a perspective view of the Fig. 1, viewed from an angle different from that of Fig. 1 is different. Fig. 3 shows a block diagram of a control system of the sewing machine including the stitch skip (etc.) detecting device according to the embodiment of the invention. Fig. 4 shows a waveform diagram of an output signal of a photoelectric sensor included in the stub outlet (etc.) detecting device according to the embodiment of the invention, with an encoder Z-phase signal. Fig. 5 shows a flowchart of a stub outlet (etc.) detection processing operation by the stub outlet (etc.) detecting apparatus according to the embodiment of the invention. Fig. 6A is a typical plan view and Fig. 6B is a vertical section of a shuttle and the light emitting part of a photoelectric sensor of the sewing machine according to the embodiment of the invention. Fig. 7 is a typical vertical section of the shuttle and the light emitting part of the photoelectric sensor of the sewing machine according to the embodiment of the invention, showing another example of the arrangement of the light emitting part. Fig. 8 is a typical vertical section of the shuttle and the light emitting part of the photoelectric sensor of the sewing machine according to the embodiment of the invention, showing another example of the arrangement of the light emitting part. Fig. 9A is a typical diagram showing an arrangement of three light-receiving elements constituting the light-receiving part of the photoelectric sensor according to the embodiment of the invention; Fig. 9B shows a parallel circuit diagram of the three light receiving elements and Fig. 9C is a typical representation of a combination of an upper and a lower sensor area. Fig. 10A, Fig. 10B, Fig. 10C and Fig. 10D show typical representations of different states of a needle thread passing through a shuttle, with the light receiving part of Fig. 9 arranged together. Fig. Fig. 11A shows a typical waveform diagram of variations in the total times of the three light receiving elements when the needle thread is in the state of Fig. 10A happens, Fig. Fig. 11B shows a typical waveform diagram of variations in the total times of the three light receiving elements when the needle thread is in the state of Fig. 10B happens, Fig. Fig. 11C shows a typical waveform diagram of variations in the total times of the three light receiving elements when the needle thread is in the state of Fig. 10C happens, and Fig. Fig. 11D shows a typical waveform diagram of variations in the total times of the three light receiving elements when the needle thread is in the state of Fig. 10D happens.

[0020] Fig. Fig. 12A1 shows a typical waveform diagram of variations in the total times of two upper light receiving elements when the needle thread is in the state of Fig. 10A happens, Fig. 12A2 shows a typical waveform

[0021] Diagram of variations of the total times of two lower light receiving elements; Fig. Fig. 12B1 shows a typical waveform diagram of variations in the total times of the two upper light receiving elements when the needle thread is in the state of Fig. 10B happens, Fig. 12B2 shows a typical waveform diagram of variations in the total times of two lower light receiving elements; Fig. Fig. 12C1 shows a typical waveform diagram of variations in the total times of the two upper light receiving elements when the needle thread is in the state of Fig. 10C happens, and Fig. 12C2 shows a typical waveform diagram of variations in the total times of the two lower light-receiving elements; and Fig. 12D1 shows a typical waveform diagram of variations in the total times of two upper light receiving elements when the needle thread is in the state of Fig. 10D happens, Fig. 12D2 shows a typical waveform diagram of variations in the total times of the two lower light receiving elements. DETAILED DESCRIPTION

[0022] Referring now to the drawings, a description will be given of a stitch skip (etc.) detecting device on a sewing machine according to the invention.

[0023] Fig. 1 and Fig. 2 shows a perspective view of a horizontal shuttle centering area of ​​a sewing machine which includes a stitch-out (etc.) detecting device 10 according to an embodiment of the invention, and Fig. 3 shows a block diagram of the same.

[0024] As in Fig. As shown in Figure 3, the stitch-leave (etc.) detecting device 10 includes a photoelectric sensor 11 and a CPU substrate 12. The CPU substrate 12 is connected to the photoelectric sensor 11 and a sewing machine control substrate 20. The photoelectric sensor 11 includes a light-emitting part 13 and its driving part 14, and a light-receiving part 15 and its signal-amplifying part 16.

[0025] Fig. 1 and Fig. 2 show a horizontal shuttle 1, a pinhole 2, the light emitting part 13 and the light receiving part 15. The horizontal shuttle 1 has a tip 1a and rotates horizontally in the direction of arrow F.

[0026] When a sewing machine needle (not shown) descends into the needle hole 2, reaches the bottom dead center, and then rises, the needle thread forms a loop. While the tip 1a catches the loop of the needle thread, the horizontal shuttle 1 rotates in the direction of arrow F. When the horizontal shuttle 1 further rotates by approximately half a rotation, the needle thread is pulled by the machine needle to slip out of the horizontal shuttle 1, and the loop of the needle thread passes through the horizontal shuttle 1. That is, during sewing, the needle thread extending from the machine needle passing through a fabric is caught by the tip 1a of the horizontal shuttle 1 and passes above the horizontal shuttle 1 to pass through a bobbin thread. The needle thread passing through the horizontal shuttle 1 is detected by the photoelectric sensor 11.

[0027] A light path L1 extending from the light-emitting part 13 to the light-receiving part 15 of the photoelectric sensor 11 is set to pass through the needle thread passage area and traverse the horizontal shuttle 1 orthogonally to the rotation axis A1 of the horizontal shuttle 1. In this embodiment, due to the use of the horizontal shuttle 1, the light path L1 traverses just above the upper end surface 1b of the horizontal shuttle 1. Separating the two sides of the horizontal shuttle 1 by a plane containing the rotation axis A1 of the horizontal shuttle 1 and the center axis A2 of the machine needle, the light-emitting part 13 is located on the side F1 toward which the tip 1a, which has picked up the needle thread 3, advances. The light-receiving part 15 is located on the opposite side F2.If a mirror is arranged at the shown position of the light receiving part 15 and the light is reflected back from the light emitting part 13 towards the side F1, then the light receiving part 15 can also be located on the same side as the light emitting part 13, ie on the side F1.

[0028] The CPU substrate 12 functions as a means for detecting the passage of the needle thread 3 based on the amount of light received by the light receiving part 15.

[0029] The sewing machine control substrate 20 receives the phase signal of the sewing machine's harmonic shaft (main shaft) output from an encoder 21. An encoder A phase signal 31, to be input from the sewing machine control substrate 20 to the CPU substrate 12, is a smallest unit signal; in the present embodiment, one pulse is output at a harmonic shaft rotation of 1°. An encoder Z phase signal 32, to be input from the sewing machine control substrate 20 to the CPU substrate 12, is a pulse signal, with one cycle corresponding to one revolution of the harmonic shaft. While the harmonic shaft rotates once, the horizontal shuttle rotates twice, and the machine needle reciprocates once.

[0030] A drive control signal from the CPU substrate 12 is supplied to the drive part 14 of the photoelectric sensor 11, thereby driving the light-emitting part 13 to emit light. A photoelectric conversion signal corresponding to the amount of light received by the light-receiving part 15 is amplified by the signal amplifying part 16 and converted into an output signal 34, which is then supplied to the CPU substrate 12. A needle thread detection region is set in advance, namely, in a phase region in which, when the tip 1a picks up the needle thread 3, the needle thread 3 blocks the light path L1 extending from the light-emitting part 13 to the light-receiving part 15 of the photoelectric sensor 11, or in a phase region including such a region.

[0031] Based on the encoder A-phase signal 31 and the encoder Z-phase signal 32, the CPU substrate 12 checks whether the output signal 34 of the photoelectric sensor 11 is changed by the passage of the needle thread 3 in the needle thread detection range. Specifically, if any change caused by the passage of the needle thread 3 is detected, the CPU substrate 12 determines that the needle thread 3 has passed normally, that is, no stitch skipping or thread breakage has occurred; and if no change caused by the passage of the needle thread 3 is detected but the needle thread detection range is ended, the CPU substrate 12 determines that stitch skipping or thread breakage has occurred, and outputs a stitch skipping (etc.) detection signal 33 to the sewing machine control substrate 20.

[0032] Fig. 4 shows a part of the waveform of the output signal 34 of the photoelectric sensor 11, which is monitored by an external computer 30 connected to the CPU substrate 12.

[0033] The following is a description of a branch outlet (etc.) detection processing operation using a flow chart, which is shown in Fig. 5 is shown.

[0034] First, at the start of the stub outlet (etc.) detection processing operation, the CPU substrate 12 turns off a stub outlet (etc.) detection flag (step S1).

[0035] The A / D of the CPU substrate 12 converts the output signal 34 of the photoelectric sensor 11 to obtain a photoelectric sensor value (step S2).

[0036] Next, the CPU substrate 12 calculates a harmonic angle based on the encoder A-phase signal 31 and the encoder Z-phase signal 32. If the harmonic angle is within the needle thread detection range (YES in step S3), it turns on the stitch skip (etc.) detection flag (step S4). Before this, if the arm shaft angle is outside the needle thread detection range, NO in step S3 and NO in step S8, and the processing returns to step S2.

[0037] When the needle thread 3 blocks the light path L1 between the light emitting part 13 and the light receiving part 15 during its passage through the horizontal shuttle 1, the amount of light received by the light receiving part 15 changes. As shown in Fig. As shown in Figure 4, the output signal 34 of the photoelectric sensor 11 undergoes a change at a location 34a, the changed location 34a resulting from the blockage of the light path L1 by the needle thread 3. Upon detecting such a change, the CPU substrate 12 determines that the needle thread 3 is detected.

[0038] The CPU substrate 12 checks whether the needle thread 3 is present in the needle thread detection area based on the photoelectric sensor value. If the needle thread 3 is detected (YES in step S5), it turns off the stitch skip (etc.) detection flag (step S6). After the needle thread is detected, if the harmonic angle is within the needle thread detection area, the processing is looped (YES in step S7). If the harmonic angle has passed the needle thread detection area, the processing returns to step S2 (NO in step S7). After that, before entering the needle thread detection area, NO in step S3 and NO in step S8, the processing returns to step S2.

[0039] On the other hand, when the needle thread 3 is not detected in the needle thread detecting area but actually passes through the needle thread detecting area: NO in step S5, whereby the processing returns to step S2, and NO in step S3, whereby the processing goes to step S8.

[0040] In step S8, the stitch skip (etc.) detection flag is checked for its ON or OFF state, and if it is ON, it is determined that stitch skip or thread breakage has occurred, and in step S9, the stitch skip (etc.) detection signal 33 is output to the sewing machine control substrate 20.

[0041] Here, upon receiving the stitch skipping (etc.) detection signal 33, the sewing machine control substrate 20 executes sewing operation stop control and notification control to inform a user through a display device that stitch skipping, etc., has been detected.

[0042] The arrangement of the light emitting part 13 will now be described with reference to Fig. 6 to 8 described.

[0043] When applying a light-emitting element, e.g. a light-emitting diode, to the light-emitting part 13, as in Fig. 6B, Fig. 7 and Fig. 8, a conical expansion of the radiation area 40 results according to the distance to the light emitting part 13.

[0044] As in Fig. 6B, the optical axis AL of the light emitting part 13 is orthogonal to the rotation axis A1 of the horizontal shuttle 1 and exists above the upper end surface 1b of the horizontal shuttle 1, the shadow of the needle thread 3 overlaps with the shadow area 41 of the horizontal shuttle 1, thereby raising the possibility that even if the light receiving part 15 is arranged on the side F2 of the horizontal shuttle 1, the passage of the needle thread 3 cannot be detected.

[0045] Similarly, when the optical axis AL exists below the upper end surface 1b of the horizontal shuttle 1 (when the optical axis AL crosses the shuttle 1), the shadow of the horizontal shuttle 1 may overlap with the shadow area of ​​the needle thread 3.

[0046] For effective thread detection, as in Fig. 7, the arrangement is such that the optical axis AL, which is orthogonal to the rotation axis A1 of the horizontal shuttle 1, coincides with the upper end surface 1b of the horizontal shuttle 1, whereby the entire shadow 42 of the needle thread is projected separately from the shadow area 41 of the horizontal shuttle 1; further, the light receiving part 15 is arranged in an area in which the shadow 42 of the needle thread is projected. In the embodiment shown with reference to Fig. In the structure described in 1 ~ 5, the light path L1 uses the arrangement as described above.

[0047] In this case, it is the case with an optical system whose radiation area spreads conically in this way, as in Fig. 8, the optical axis AL is not required to coincide with the upper end surface 1b of the horizontal shuttle 1; rather, a light path may be formed that traverses the horizontal shuttle 1, as viewed from the upper end surface 1b of the horizontal shuttle 1, orthogonally to the rotation axis A1, and this light path may be used as an effective light path for detecting the passage of the needle thread 3. That is, the optical axis AL may not be the shortest optical path from the light-emitting part 13 to the light-receiving part 15.

[0048] Furthermore, since the horizontal shuttle 1 has a sub-shaft (not shown) for transmitting rotational power to the horizontal shuttle 1 arranged on the bottom side, the upper end surface 1b exists on the side opposite the sub-shaft. In a vertical shuttle, the optical axis AL is also arranged on the end surface opposite the sub-shaft.

[0049] The Fig. 1 and Fig. The light path L1 shown in Figure 2 is also shown in Fig. 6A. On the horizontal plate of Fig. 6A, a straight line orthogonal to a straight line connecting the rotation axis A1 and the center axis A2 of the machine needle is defined as a reference light path L0. The light path L1 from the light emitting part 13 to the light receiving part 15 of the photoelectric sensor 11 is arranged on the opposite side of the center axis A2 of the machine needle via the reference light path L0. Even when arranging a light path at a position remote from the center axis A2 of the machine needle with the reference light path L0 as a reference, as shown in Fig. 4, a sufficient change in the output signal 34 is provided and thus the detection of stitch omissions etc. is enabled.

[0050] However, to further improve the detection accuracy, the light emitting part 13 can be brought as close as the needle thread 3, preferably on the side F1 where the behavior of the needle thread 3 is stable. For this purpose, preferably, as shown in Fig. 6A, a light path L2 parallel to the reference light path L0 and close to the central axis A2 of the machine needle with the reference light path L0 as a reference may be employed, or a light path L3 which is inclined relative to the optical axis AL and enables the light emitting part 13 to be arranged in a range of more than 0° to less than 90°, or the like, whereby the light emitting part 13 can be arranged as close as the needle thread 3 in the range of 0° to less than 90°.

[0051] Here, the above-mentioned page F1 corresponds, as in Fig. 6A, to a section (section F1) extending in a direction from 0° to 180° downstream of the shuttle's rotation direction F, with the rotation axis A1 as the center (observation point) and the position of the machine needle's center axis A2 as 0°. Furthermore, the side F2 corresponds to a section (section F2) extending in a direction from 180° to 360°.

[0052] In this case, in addition to the light-emitting diode, a laser diode can also be used as the light-emitting element to be applied to the light-emitting part 13.

[0053] A description will now be given of the arrangement of the light receiving part 15 with reference to the Fig. 9 and Fig. 10.

[0054] Because a semiconductor element used as such a light-receiving element is typically used to measure the luminance of broadly diffused light, the light-receiving area is small, approximately 0.5 mm x 0.5 mm. In addition, the smaller the area of ​​the semiconductor element, the greater the number of semiconductor elements that can be cut from a semiconductor; therefore, the smaller the area of ​​the semiconductor element, the lower the cost per semiconductor element.

[0055] However, the semiconductor element for use in the light receiving part 15 according to the invention must have a width of 1 mm or more in the vertical direction; this is due to its relationship to the position of the needle thread 3 passing above the horizontal shuttle 1 and the arrangement of the light emitting part 13 serving as a light source.

[0056] Furthermore, because the needle thread 3 passes above the horizontal shuttle 1 in the horizontal direction, the shadow 42 of the needle thread 3 is also projected in the horizontal direction. Therefore, if the semiconductor element is widely present in the horizontal direction, the detection area for detecting the projected shadow 42 of the needle thread 3 increases.

[0057] To increase the detection area, a method for arranging the semiconductor elements in a matrix-like manner is expected; however, because the semiconductor element package is located outside the essential sensing area, a waste of space results.

[0058] Therefore, if the semiconductor elements are arranged side by side in the horizontal direction as the light receiving part 15 and are arranged in different positions in the vertical direction, the range for detecting the horizontally projected shadow 42 of the needle thread 3 is expanded, whereby the detection sensitivity for the shadow 42 of the needle thread 3 can be improved using small-area semiconductor elements. For example, if, as in Fig. 9A, three semiconductor elements 15a, 15b, and 15c are arranged in different vertical positions, then the detection range can be expanded. As shown in Fig. As shown in Figure 9A, the three semiconductor elements 15a, 15b, and 15c are mounted on a substrate 15K, arranged in different horizontal and vertical positions. The necessary condition for such an offset is that the actual detection areas (light-receiving surfaces) of the semiconductor elements are offset.

[0059] Furthermore, semiconductor elements arranged in multiple numbers, for example, as in Fig. 9B, the semiconductor elements 15a, 15b, and 15c may be connected in parallel; in this way, the received light quantities detected by the respective semiconductor elements can be summed.

[0060] Furthermore, as a method for improving the accuracy of detection of stitch omissions etc. of the Fig. 9A and Fig. 9B, a method is available in which, as shown in Fig. 9C, the three semiconductor elements are grouped into upper and lower sensor regions, specifically, semiconductor elements 15a and 15b are arranged in the upper sensor region 15m, and semiconductor elements 15b and 15c are arranged in the lower sensor region 15n. Specifically, as the sum value of the upper sensor region 15m, the respective light quantities detected by semiconductor elements 15a and 15b are summed, and the respective light quantities detected by semiconductor elements 15b and 15c are summed, thereby detecting the occurrence of stitch skipping, etc. Only when stitch skipping, etc., is detected in both the upper and lower sensor regions 15m and 15n does the sewing machine control substrate 20 determine that stitch skipping has occurred.

[0061] Although the needle thread 3 normally passes along the upper end surface 1b of the horizontal shuttle 1, when sewing a stepped portion in which fabric pieces overlap each other and thus have a partially greater thickness, or when a sewing pitch is changed, the needle thread 3 provides a residual portion; therefore, when the needle thread 3 passes through the upper end surface 1b of the horizontal shuttle 1, it may act violently and thus run skewed or float.In such a case, in the method in which the three semiconductor elements 15a, 15b, and 15c are summed for detection purposes, the photoelectric sensor 11 may not be able to detect the needle thread 3 because variations in the amount of received light caused by the shadow 42 of the needle thread 3 are small; this results in the possibility that the sensor may erroneously detect such a case as a stitch skip or thread breakage.

[0062] Fig. 10A shows a state in which the needle thread 3 exists along the upper end surface 1b of the shuttle 1; Fig. 10B shows a state in which the needle thread 3 floats above the shuttle 1; Fig. 10C shows a state in which the needle thread 3 runs obliquely, with the semiconductor element 15a being 3 / 4 open, the semiconductor element 15b being fully closed, and the semiconductor element 15c being half open; and Fig. 10D shows a state in which the needle thread 3 is skewed, with the semiconductor element 15a fully open, the semiconductor element 15b three-quarters open, and the semiconductor element 15c fully closed. In a fully closed state, where the shadow of the needle thread 3 completely covers the actual detection area (the light-receiving surface) of the semiconductor element, the output value is 1, while in a fully open state, where the shadow does not cover the actual detection area (the light-receiving surface) of the semiconductor element at all, the output value is 0.

[0063] Fig. 11A to 11D show output values ​​provided by the method of summing the respective outputs of the semiconductor elements 15a, 15b and 15c, and Fig. 12A1, A2 ~ D1 and D2 show output values ​​provided by the method of grouping the semiconductor elements 15a, 15b into the upper sensor area 15m and grouping the semiconductor elements 15b, 15c into the lower sensor area 15n and summing the output values ​​of each area. Fig. 11A ~ 11D and Fig. 12A1, A2 ~ D1 and D2 correspond to the states of the needle thread 3 of Fig. 10A ~ 10D. Fig. 12 A1, B1, C1 and D1 show the output value of the upper sensor range 15m, while Fig. 12A2, B2, C2 and D2 show the output value of the upper sensor range 15n.

[0064] According to the method of summing the respective outputs of the semiconductor elements 15a, 15b and 15c, the state of Fig. 10A correspond output value of Fig. 11A, which leads to the state of Fig. 10B corresponding output value of Fig. 11B and the condition of Fig. 10C corresponding output value of Fig. 11C, that the sum value of the outputs of the semiconductor elements 15a, 15b and 15c does not exceed a threshold value TH, thereby enabling detection of the shadow 42 of the needle thread 3. At the output value of Fig. 11D, which leads to the state of Fig. 10D, however, the area of ​​the shadow 42 of the needle thread 3 corresponding to the actual detection area (the light-receiving surface) is insufficient, and thus the sum value of the outputs of the semiconductor elements 15a, 15b, and 15c exceeds the threshold value TH; therefore, although the needle thread 3 actually passes, the sensor cannot detect the needle thread 3, but erroneously detects stitch skipping or thread breakage.

[0065] On the other hand, in the method of grouping the semiconductor elements 15a and 15b into the upper sensor area 15m and grouping the semiconductor elements 15b and 15c into the lower sensor area 15n and summing the output values ​​of each area as shown in Fig. 12A1, A2 ~ D1 and D2, a detection of the needle thread 3 in each of the Fig. 10A ~ 10D shown states are possible. In the state of Fig. 10D, as in Fig. 12 D2, the sum value of the semiconductor elements 15b and 15c exceeds the threshold value TH; however, as shown in Fig. 12 D1, the sum value of the semiconductor elements 15a and 15b does not exceed the threshold value TH, the sewing machine control substrate 20 can determine that the needle thread is present.

[0066] Thus, because the detection results in each area can be calculated independently and the presence of the needle thread 3 can be detected in any of the areas, even if the needle thread 3 passing through the horizontal shuttle 1 acts vigorously, the light receiving part 15 can detect variations in the amount of light received.

[0067] As described above, multiple light-receiving elements are staggered, and needle thread detection is performed in multiple, differently positioned areas. Here, if the needle thread can be detected in any of the areas, it can be determined that stitch skipping and thread breakage have not occurred. If the needle thread cannot be detected in any of the areas, it can be determined that stitch skipping or thread breakage has occurred, thereby enabling final detection of stitch skipping and thread breakage. This can improve the accuracy of stitch skipping and thread breakage detection.

[0068] In the above-mentioned stitch-missing (etc.) detecting device according to the embodiment, since the light path L1 from the light-emitting part 13 to the light-receiving part 15 of the photoelectric sensor 11 is set to pass through the passage area of ​​the needle thread 3 and traverse the shuttle 1 orthogonally to the rotation axis A1 of the shuttle 1, the moving direction of the needle thread 3, which moves while being caught by the tip 1a of the shuttle 1, and the traversing direction of the light path L1 are brought closer to each other, thereby increasing the time period during which the light path L1 to the light-receiving part 15 is blocked by the needle thread 3 and thus the detection time of the needle thread 3 by the photoelectric sensor 11. This can improve the accuracy of stitch-missing and thread breakage detection.This can further facilitate the application of the photoelectric sensor 11 to the horizontal shuttle 1 by inserting the light path L1 from the light emitting part 13 to the light receiving part 15 into a narrow space between the upper end surface 1b of the horizontal shuttle 1 and a needle plate, etc.

[0069] Furthermore, since the needle thread passage is detected by a difference between the amounts of light received when the light path L1 to the light receiving part 15 is blocked and not blocked by the needle thread 3, it is possible to apply inexpensive general-purpose light emitting and receiving elements to the photoelectric sensor 11 while achieving sufficient detection accuracy.

[0070] In the latter half section F2 around the shuttle, where the needle thread 3 passes through the shuttle 1, the behavior of the loop portion of the needle thread 3 is unstable due to the slippage of the needle thread 3 from the shuttle 1, compared to the section F1 where the former half of the needle thread 3 is pulled from the tip 1a. Furthermore, when light is propagated from a light-emitting diode or the like, as the distance from the light-emitting part 13 of the photoelectric sensor 11 to an object to be detected (the needle thread 3) becomes smaller, the shadow of the object to be detected becomes larger, thereby making it possible to detect variations in the amount of light received by the light-receiving part 15 in a simple and unambiguous manner.

[0071] In the stitch dropout (etc.) detecting device according to the embodiment, by irradiating light from the light emitting part 13 disposed adjacent to the needle thread 3 onto the former half cut F1 where the needle thread 3 is pulled from the tip 1a, variations in the received light amount can be detected in a stable and unambiguous manner, thereby enabling improvement in the accuracy of stitch dropout and thread breakage detection.

[0072] In the case that the optical axis AL of light emitted from the light emitting part 13 of the photoelectric sensor 11 is upwardly away from the upper end surface 1b of the boat 1 (state of Fig. 6B), when light is irradiated onto the passing needle thread 3, its shadow is projected onto the shuttle 1, giving rise to a concern that variations in the amount of received light caused by the passage of the needle thread 3 cannot be sufficiently detected in the light receiving part 15. Furthermore, in the case where the optical axis AL of light emitted from the light emitting part 13 of the photoelectric sensor 11 traverses the shuttle below the upper end surface 1b, the passing needle thread 3 enters the shadow of the shuttle 1, giving rise to a concern that variations in the amount of received light caused by the passage of the needle thread 3 cannot be sufficiently detected in the light receiving part 15.

[0073] In the branch outlet (etc.) detection device according to the embodiment of Fig.7, since the optical axis AL of light emitted from the light emitting part 13 coincides with the upper end surface 1b of the shuttle 1, neither the shadow of the passing needle thread 3 is projected onto the shuttle, nor the passing needle thread 3 enters the shadow of the shuttle 1, thereby enabling sufficient detection of variations in the amount of received light caused by the passage of the needle thread 3, and thus enabling improvement in the accuracy of the stitch dropout and thread breakage detection.

[0074] Further, in the stitch skip (etc.) detecting device according to the embodiment, the needle thread 3 passing through the horizontal shuttle 1 can be detected by the photoelectric sensor 11, thereby enabling detection of stitch skip and thread breakage.

[0075] Here, in the above embodiment, a structure comprising a set of sewing machine needles and a horizontal shuttle is shown. However, the stitch skip (etc.) detecting device according to the present invention can also be applied to the respective horizontal shuttles in a twin-needle lockstitch sewing machine with two sets of machine needles and horizontal shuttles. In this case, the effectiveness of the detection operation can be improved if reporting control is performed to report on which of the two shuttles stitch skip, etc., has occurred.

[0076] Furthermore, in the above embodiment, a structure using a horizontal shuttle is shown. However, in the stitch leakage (etc.) detecting device according to the embodiment, the light path from the light emitting part 13 to the light receiving part 15 of the photoelectric sensor 11 may also be set to traverse the upper end surface in the direction of the rotation axis A1 on the tip side when the upper end surface is viewed vertically. Thus, the device can also be applied to a sewing machine with a vertical shuttle.

[0077] Furthermore, although the branch outlet (etc.) detecting device according to the embodiment uses a transmission-type sensor constituted by the light-emitting part 13 and the light-receiving part 15, a regression-reflection-type sensor constituted by a light-projector-receiver including a light-emitting part and a light-receiving part integrated with each other, and a mirror arranged opposite to the light-projector-receiver, may also be used. In this case, a coaxial reflection-type sensor is preferred as the regression-reflection-type sensor. In particular, the use of a fiber sensor with concentrically arranged fibers can facilitate size reduction.By using a regression reflection type sensor, when detecting a thread passing through a shuttle, both the light from the projection side and the reflected light from the mirror can be blocked, making it possible to increase the difference between signals in the light reception period compared to a transmission type sensor. A mirror is provided on one side of the needle outlet (etc.) detection device to simplify its assembly, further simplifying the connection of a control substrate and a cable, thereby making it possible to reduce the size and facilitate adjustment.

Claims

[1] A stitch skip and thread breakage detection device (10) intended for use on a sewing machine, for detecting a needle thread (3) by means of a photoelectric sensor (11), wherein the needle thread (3) extends from a sewing machine needle penetrating a fabric, is detected by a tip (1a) of a shuttle (1), and passes through the shuttle (1) to pass through a bobbin thread, thereby detecting stitch skip and thread breakage, wherein a light path (L1) extending from a light emitting part (13) to a light receiving part (15) of the photoelectric sensor (11) is set to pass through the passage area of ​​the needle thread (3) and traverse the shuttle (1) orthogonal to the rotation axis (A1) of the shuttle (1), and wherein the passage of the needle thread (3) is detected according to the amount of light emitted by the light receiving part (15). is received. [2] A stitch skip and thread breakage detecting device according to claim 1, wherein, when the two sides of the shuttle (1) are separated from each other by a plane including the rotation axis (A1) and the center axis (A2) of the sewing machine, the light emitting part (13) is arranged on the side where the tip (1a) which has caught the needle thread (3) advances. [3] A stitch-dropping and thread-breakage detecting device according to claim 1 or 2, wherein the optical axis (AL) of a light to be emitted from the light-emitting part (13) coincides with the end face (1b) of the shuttle (1) which is located on the side opposite to a sub-shaft for transmitting rotational power to the shuttle (1). [4] Stitch-out and thread-breakage detecting device according to one of claims 1 to 3, wherein the shuttle (1) is a horizontal shuttle. [5] A stitch omission and thread breakage detecting device according to claim 1 or 2, wherein the light receiving part (15) is formed by multiple light receiving elements, and wherein the light receiving elements are respectively arranged in different horizontal and vertical positions. [6] A stitch-missing and thread-breakage detecting device according to claim 5, wherein said multiple light-receiving elements detect the amounts of light received by them, respectively.

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