Thread take-up mechanism and sewing machine

Abstract

To provide a mechanism for exchanging a thread take-up lever, capable of changing only a part of movement process for forming a seam to make optimum adjustment corresponding to the thickness of a sewing object, and a sewing machine.SOLUTION: A mechanism for exchanging a thread take-up lever 2, which can change the motion of a thread take-up lever 9 interlocked with an arm shaft 3, comprises a cylindrical cam 10 disposed on the arm shaft 3, having a plurality of cam surfaces 10b and 10c, a contact part 9c disposed on the thread take-up lever 9, in contact with any one of the cam surfaces 10b and 10c, and a switching body 12 for changing the contact part 9c from a position in contact with one of the cam surfaces 10b and 10c to another position in contact with another one.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a thread take-up switch mechanism provided in a double chainstitch sewing machine, and to a sewing machine equipped with this thread take-up switch mechanism. [Background technology]

[0002] Sewing machines capable of performing double chain stitching as specified by symbols 406, 407, etc. in JIS-L0120 have been known. As shown in Figs. 4 to 6, such sewing machines are equipped with needles (in the illustrated example, the needles are composed of three needles, a first needle 4, a second needle 5, and a third needle 6), a looper 7, a thread take-up 9, and a feed mechanism (not shown). A first needle thread T1, a second needle thread T2, and a third needle thread T3 are inserted into the needle holes of the first needle 4, the second needle 5, and the third needle 6, respectively, and the looper 7 is provided at a position where it can capture the looper thread T4. These members work together to perform a double chain stitch on a sewing object (not shown) such as a cloth. The double chain stitch shown in the figures indicates a stitch with symbol 407.

[0003] Here, a method for forming a double chainstitch stitch will be described with reference to the drawings. First, in Fig. 4(a), the first needle 4, etc. is located at the lowest point, and the looper 7 is located at the rightmost point. Next, as shown in Fig. 4(b), the first needle 4, etc. rises, causing a loop to be formed in the first needle thread T1, etc. Then, the looper 7 moves to the left, and the tip of the looper 7 enters into the loop.

[0004] After that, as shown in Fig. 5(a), the looper 7 captures all the loops, and the first needle 4 etc. rise further. At this time, the first needle thread T1 etc. is tightened by a thread take-up (not shown). Then, as shown in Fig. 5(b), the first needle 4 etc. rises to the highest point, and the looper 7 moves to the leftmost point while capturing the looper thread T4. In addition, the fabric is moved from the rear to the front by a feed mechanism (not shown), so that the stitches are fed forward a predetermined amount overall.

[0005] Thereafter, as shown in FIG. 6(a), the looper 7 moves to the right. At this time, the first needle 4 etc. descends while scooping up the looper thread T4, so the first needle thread T1 etc. and the looper thread T4 cross. Then, as shown in FIG. 6(b), the looper 7 moves to the right and then moves forward. As a result, the entanglement between the looper 7 and the first needle thread T1 is released. Meanwhile, the first needle 4 etc. descends while scooping up the looper thread T4, so a new stitch is formed. Thereafter, the procedure from FIG. 4(a) onwards is repeated to perform a double chainstitch.

[0006] When a double chainstitch is performed, the needle thread path (thread route) changes significantly at each stage of stitch formation due to the up and down movement of the needle and the reciprocating motion of the looper. To absorb these changes, the thread take-up lever is moved up and down in accordance with the up and down movement of the needle. Specifically, the thread is supplied to the needle side by lowering the take-up lever, and the thread on the needle side is collected and tightened by raising the take-up lever. In other words, the needle thread is supplied and collected by the take-up lever according to the stage of stitch formation, allowing the stitch to be formed stably.

[0007] The type of fabric to be sewn and the number of layers of fabric to be layered vary depending on the intended product. In other words, the thickness of the object to be sewn varies, and so does the thread path of the needle thread. Therefore, if the amount of needle thread supplied can be optimized according to the thickness of the object to be sewn, it becomes possible to stably and appropriately form stitches.

[0008] A known prior art technique that focuses on this point is, for example, Patent Document 1. Patent Document 1 proposes a switching mechanism that uses an eccentric pin mechanism in a lockstitch sewing machine to change the phase (operation timing) and vertical stroke of the thread take-up lever according to the thickness of the sewing object. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2009-195449 A Summary of the Invention [Problem to be solved by the invention]

[0010] As described above, in Patent Document 1, the link that drives the thread take-up lever is changed by the eccentric pin mechanism. In other words, when adjustment is made according to the thickness of the sewing object, both the phase and the vertical stroke of the thread take-up lever change at the same time. For this reason, even if the technology of the lockstitch sewing machine according to Patent Document 1 is applied to a double chainstitch sewing machine, the problem of both the phase and the vertical stroke of the thread take-up lever changing at the same time will occur, as in Patent Document 1, and it is difficult to make optimal adjustment according to the thickness of the sewing object. In addition, it is difficult to change only a part of the operation process, such as making the timing of the thread take-up lever faster than before only at a certain stage in the formation of a stitch, with the technology of Patent Document 1.

[0011] In consideration of these problems, the present invention aims to provide a thread take-up lever switching mechanism that allows for changing only part of the operational process related to stitch formation, thereby enabling optimal adjustment according to the thickness of the material to be sewn, and a sewing machine equipped with this thread take-up lever switching mechanism. [Means for solving the problem]

[0012] The present invention relates to a mechanism for changing the operation of a thread take-up lever that is connected to a shaft of a double chainstitch sewing machine, the mechanism comprising a plurality of cam surfaces, and The upper shaft is attached to the outer periphery of the upper shaft so as to be slidable in the axial direction. a cylindrical cam that is attached to the balance and a contact portion that is provided on the balance and contacts any one of the cam surfaces; The position of the cylindrical cam relative to the A switching body for switching the input signal to the input terminal. A plurality of cam surfaces having different cam profiles are arranged in the axial direction on the outer peripheral surface of the cylindrical cam, and the switching body slides the cylindrical cam from a position where one of the plurality of cam surfaces contacts the contact portion to a position where another of the plurality of cam surfaces contacts the contact portion. It is characterized by the above.

[0013] In such a balance switching mechanism, it is preferable that one of the plurality of cam surfaces is set so that the timing at which the balance descends from the highest point is earlier than that of the other of the cam surfaces.

[0014] In such a balance switching mechanism, it is preferable that one of the plurality of cam surfaces is set so that the uppermost point of the balance is higher than another of the cam surfaces.

[0015] The present invention also provides a balance change mechanism that is provided in a double chainstitch sewing machine and is capable of changing the operation of a balance that is linked to an upper shaft, the balance change mechanism including a cylindrical cam that has a plurality of cam surfaces and is provided on the upper shaft, a contact portion that is provided on the balance and contacts one of the plurality of cam surfaces, and a change body that changes the contact portion from a position that contacts one of the plurality of cam surfaces to a position that contacts the other one of the plurality of cam surfaces, The balance swings about a fulcrum to move the thread holding part up and down, and when the fulcrum is located between the thread holding part and the contact part, the contact part is located below the cylindrical cam, and when the contact part is located between the thread holding part and the fulcrum, the contact part is located above the cylindrical cam. It is characterized by:

[0016] The present invention also relates to a sewing machine including any one of the above-mentioned thread take-up lever switching mechanisms. Effect of the Invention

[0017] In the take-up switching mechanism of the present invention, a cylindrical cam having a plurality of cam surfaces is provided on the upper shaft, and a contact portion that contacts one of the cam surfaces is provided on the take-up. The contact portion can be changed by the switching body from a position where it contacts one of the plurality of cam surfaces to a position where it contacts another one. In other words, by operating the switching body, it is possible to select the most suitable cam surface from among the plurality of cam surfaces that drive the take-up according to the thickness of the sewing object. Also, by changing the shape of the cam surface, it is possible to change only a part of the operation process related to stitch formation. [Brief description of the drawings]

[0018] [Figure 1] 1 is a perspective view showing an embodiment of a sewing machine according to the present invention; [Diagram 2] 2 is an explanatory diagram of a balance switching mechanism shown in FIG. 1. [Diagram 3] 2 is an operational diagram of the thread take-up, looper, and needle in the sewing machine shown in FIG. 1. [Figure 4] FIG. 2 is an explanatory diagram of a double chain stitch performed by the sewing machine shown in FIG. [Diagram 5]FIG. 5 is an explanatory diagram relating to a step performed after the step shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram relating to a step performed after the step shown in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of a sewing machine according to the present invention will be described with reference to the drawings. In the following description, for convenience, the directions of right, left, front, rear, up, down, and X, Y, and Z will be described in the drawings.

[0020] FIG. 1 shows a sewing machine 1 that embodies the sewing machine according to the present invention. The sewing machine 1 is equipped with a thread take-up switching mechanism 2 (see FIG. 2) including a switching body 12 described later. An upper shaft 3 that is rotated by a sewing machine motor (not shown) is provided on an arm section 1a of the sewing machine 1, and a lower shaft that is rotated by the sewing machine motor (not shown) is provided on a bed section 1b. A needle (in this embodiment, three needles are included: a first needle 4, a second needle 5, and a third needle 6) and a thread take-up 9 are connected to the upper shaft 3, and a looper 7 and a feed mechanism (not shown) are connected to the lower shaft. The sewing machine 1 is also equipped with a first needle thread T1, a second needle thread T2, a third needle thread T3, and a looper thread T4 that are wound around thread spools. The first needle thread T1, the second needle thread T2, and the third needle thread T3 are passed through a thread tensioner 8, a thread take-up 9, and the like, and are passed through the needle holes of the first needle 4, the second needle 5, and the third needle 6, respectively. The looper thread T4 passes through the thread tensioner 8 and is held in a position where it can be captured by the looper 7. When the sewing machine motor rotates, the elements connected to the upper shaft 3 and the lower shaft work together to perform the double chainstitch shown in Figures 4 to 6.

[0021] Before providing a detailed description of the sewing machine 1 and the thread take-up switching mechanism 2 of this embodiment, the inventor will explain the results of his / her study of double chainstitching. After extensive study by the inventor on the double chainstitching shown in Figures 4 to 6, he / she discovered that when sewing thin fabric, a fuller stitch with less shrinkage can be obtained by advancing the needle thread supply phase in the thread take-up 9 compared to the operation in the conventional double chainstitching (advancing the timing at which the thread take-up 9 descends from the highest point compared to the conventional operation). The sewing mechanism of the double chainstitch is very complicated and the exact operation has not yet been grasped, but it is expected that the amount of needle thread in the initially formed stitch increases when the first needle 4, second needle 5, and third needle 6 shown in Figure 6(b) descend and the next stitch is formed (when the first needle thread T1, second needle thread T2, and third needle thread T3 captured by the looper 7 come out of the looper 7) as the take-up lever 9 quickly supplies the first needle thread T1, etc. to the side of the first needle 4, etc., and some of this increased amount of thread remains even after tightening, resulting in a plump stitch. Figure 6(b) shows the state in which the upper shaft 3 has rotated to an angle of 300°, assuming that the angle of the upper shaft 3 is 0° when the first needle 4, etc. is at its lowest point (as shown in Figure 4(a)). On the other hand, when the take-up 9 rises, a portion of the supplied first needle thread T1, etc. is collected and the stitch is tightened, but if this timing is too early, excessive tension will be applied to the first needle thread T1, etc., causing the first needle thread T1, etc. to break. For this reason, it is said that it is best not to change the timing at which the take-up 9 rises, regardless of the thickness of the material to be sewn.

[0022] In addition, when performing double chain stitching, the looper 7 moves in the front-rear and left-right directions relative to the cloth being sewn, but does not move up-down. In other words, even if the thickness of the cloth being sewn changes, the consumption of the looper thread T4 basically does not change. On the other hand, the first needle 4, the second needle 5, and the third needle 6 move up and down relative to the cloth being sewn with the first needle thread T1, the second needle thread T2, and the third needle thread T3 passing through their respective needle holes, so the consumption of the first needle thread T1, etc. changes depending on the thickness of the cloth being sewn. Therefore, when sewing thick cloth, it is useful to increase the amount of thread supplied by the thread take-up 9, in other words, to increase the stroke of the thread take-up 9.

[0023] The balance switching mechanism 2 shown in Fig. 2 is constructed based on these findings. The balance switching mechanism 2 of this embodiment is composed of a balance 9, a cylindrical cam 10, a compression spring 11, and a switching body 12. However, as will be described later, the compression spring 11 is not essential.

[0024] The balance 9 includes a plate-shaped main body 9a. One end (left end) of the main body 9a is provided with a V-shaped thread holding portion 9b that protrudes from the front to the rear. As shown in FIG. 1, the first needle thread T1, the second needle thread T2, and the third needle thread T3 are hung on the thread holding portion 9b and hold them from below. One end of the main body 9a is provided with a cylindrical contact portion 9c that protrudes from the rear to the front. The contact portion 9c contacts a left cam surface 10b or a right cam surface 10c of the cylindrical cam 10, which will be described later. The middle portion of the main body 9a (a portion between the thread holding portion 9b and the contact portion 9c) is provided with a cylindrical fulcrum portion 9d that protrudes from the front to the rear. The fulcrum portion 9d is rotatably supported by a sewing machine frame (not shown), and the main body 9a swings so that the thread holding portion 9b moves up and down around the fulcrum portion 9d. Although not shown, the balance 9 is biased by a spring (not shown) in the direction of the arrow shown (counterclockwise when viewed from the rear to the front).

[0025] The cylindrical cam 10 is attached to the upper shaft 3 so as to be non-rotatable in the circumferential direction and slidable in the axial direction. In this embodiment, as such a mechanism, the upper shaft 3 is provided with a key 3a, and the cylindrical cam 10 is provided with an opening 10a having a circular portion through which the upper shaft 3 is inserted and a rectangular portion through which the key 3a is inserted. In addition, two cam surfaces (left cam surface 10b and right cam surface 10c) are provided on the outer circumferential surface of the cylindrical cam 10. The cam profiles of the left cam surface 10b and the right cam surface 10c are partially the same, but partially different. Here, a portion where the cam profiles are the same, the outer circumferential surfaces of the left cam surface 10b and the right cam surface 10c are completely aligned, and there is no step in the axial direction is referred to as a stepless portion 10d, and a portion where the cam profiles are different, the outer circumferential surfaces of the left cam surface 10b and the right cam surface 10c are misaligned, and there is a step in the axial direction is referred to as a step portion 10e. In this embodiment, since the cam lift amount of the left cam surface 10b is larger than that of the right cam surface 10c, the step portion 10e is provided so that the left cam surface 10b protrudes radially outward more than the right cam surface 10c.

[0026] In this embodiment, the compression spring 11 is inserted through the upper shaft 3 so as to be located on the left side of the cylindrical cam 10, and biases the cylindrical cam 10 from left to right.

[0027] The switching body 12 includes a slide plate 12a that extends in the left-right direction with the left and right ends extending downward. The left and right ends of the slide plate 12a are formed into an inverted U-shape as shown in the figure. A switching lever 12b that is exposed from the housing of the sewing machine 1 as shown in Fig. 1 is provided on the upper part of the slide plate 12a. As shown in Fig. 2, the switching body 12 is attached so that the cylindrical cam 10 and the compression spring 11 attached to the upper shaft 3 are sandwiched between the left and right ends.

[0028] In this type of thread take-up switching mechanism 2, when the first needle thread T1, the second needle thread T2, and the third needle thread T3 are hung on the thread holding portion 9b of the thread take-up 9 as shown in Fig. 1 and tension of the first needle thread T1, etc. is applied, a force acts on the thread take-up 9 to rotate it in the direction of the arrow shown in Fig. 2 (counterclockwise when viewed from rear to front). Here, the contact portion 9c in this embodiment is located below the cylindrical cam 10 and contacts the cylindrical cam 10 from below. In other words, since the cylindrical cam 10 is provided on the upper shaft 3 with high rigidity, it can withstand the tension of the first needle thread T1, etc. with ease.

[0029] In the thread take-up switching mechanism 2 of this embodiment, the contact portion 9c comes into contact with the right cam surface 10c when the switching body 12 is moved to the left. That is, in this state, the thread holding portion 9b operates in accordance with the cam profile of the right cam surface 10c by the contact portion 9c that comes into contact with the right cam surface 10c. When the switching body 12 is moved to the right, the cylindrical cam 10 moves to the right by the biasing force of the compression spring 11, so that the contact portion 9c comes into contact with the left cam surface 10b. That is, in this state, the thread holding portion 9b operates in accordance with the cam profile of the left cam surface 10b. Therefore, for example, if the right cam surface 10c adopts a profile suitable for sewing thin fabrics and the left cam surface 10b adopts a cam profile suitable for sewing thick fabrics, sewing can be performed under optimal conditions according to the thickness of the sewing object by moving the switching body 12.

[0030] In addition, when the contact portion 9c is in contact with the right cam surface 10c, when the switching body 12 is moved to the right, the contact portion 9c collides with the step portion 10e. However, since the cylindrical cam 10 is attached to the upper shaft 3 so as to be slidable in the axial direction and is biased by the compression spring 11, even if the switching body 12 is moved to the right in this state, the compression spring 11 is compressed and the impact when the step portion 10e collides with the contact portion 9c can be absorbed. In addition, the cylindrical cam 10 also rotates with the rotation of the upper shaft 3, and as a result, the contact portion 9c that was in contact with the step portion 10e approaches the stepless portion 10d, and the cylindrical cam 10 automatically moves to the right by the biasing force of the compression spring 11. In other words, when the cylindrical cam 10 has multiple cam profiles, the step portion 10e may be provided depending on the cam lift amount, but by configuring it as in this embodiment, it is possible to prevent problems during switching.

[0031] Here, with regard to the left cam surface 10b and the right cam surface 10c in this embodiment, the operation of the thread holding part 9b when the contact part 9c is in contact with the left cam surface 10b and the operation of the thread holding part 9b when the contact part 9c is in contact with the right cam surface 10c will be described with reference to the operation diagram in Fig. 3. When the sewing machine motor rotates as described above, the upper shaft 3 and the lower shaft rotate accordingly, so that the first needle 4, the second needle 5, the third needle 6, and the thread take-up lever 9 connected to the upper shaft 3, and the looper 7 and the feed mechanism connected to the lower shaft move at a predetermined timing and with a predetermined stroke, as shown in the operation diagram in Fig. 3. In the operation diagram of the thread take-up lever up-down position shown in Fig. 3, the broken lines indicate the up-down positions of the thread holding part 9b in the conventional double chain stitch. In addition, the dotted line indicates the upper and lower positions of the thread holding portion 9b when the contact portion 9c is in contact with the left cam surface 10b, and the solid line indicates the upper and lower positions of the thread holding portion 9b when the contact portion 9c is in contact with the right cam surface 10c.

[0032] As described above, the inventors have found that it is preferable to advance the needle thread supply phase in the thread holding unit 9b when the sewing object is thin when performing double chain stitching. It is also preferable not to change the timing at which the thread holding unit 9b rises regardless of the thickness of the sewing object. In this embodiment, a profile suitable for sewing thin fabrics is adopted for the right cam surface 10c, and the thread holding unit 9b is made to move along the solid line in the up / down position of the thread take-up lever in FIG. 3 by moving the switching body 12 to the right. That is, in this case, only the timing at which the thread holding unit 9b descends is advanced compared to the conventional double chain stitching shown by the dashed line in FIG. 3, so that thin sewing objects can be sewn suitably.

[0033] On the other hand, when the sewing object is thick in double chain stitching, it is preferable to increase the stroke amount of the thread holding part 9b from the conventional stroke amount, while not changing the timing at which the thread holding part 9b rises, as described above. The left cam surface 10b in this embodiment adopts a profile suitable for sewing thick fabrics, and by moving the switching body 12 to the left, the thread holding part 9b moves along the dashed line in the up / down position of the thread take-up lever in Fig. 3. That is, in this case, only the stroke amount S1 of the thread holding part 9b is increased compared to the stroke amount S in the conventional double chain stitching shown by the dashed line in Fig. 3, so that the thick sewing object can be sewn suitably.

[0034] Although the embodiments embodying the present invention have been illustrated above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the spirit of the present invention described in the claims unless otherwise specifically limited in the above description. Furthermore, the effects of the above embodiments are merely examples of the effects resulting from the present invention, and do not mean that the effects of the present invention are limited to the above effects.

[0035] For example, the balance switching mechanism 2 of this embodiment is provided with the compression spring 11 to prevent collision between the contact part 9c and the step part 10e during switching. However, it is possible to eliminate the need for the compression spring 11 by using other collision prevention means, for example, by forming the step part 10e gently, that is, by inclining the step part 10e.

[0036] For example, the fulcrum 9d of the balance 9 in this embodiment is provided in the middle of the main body 9a (between the thread holding part 9b and the contact part 9c), but it may be provided at the end of the main body 9a opposite to the side where the thread holding part 9b is provided, with the contact part 9c provided in the middle of the main body 9a (the contact part 9c is provided between the thread holding part 9b and the fulcrum 9d).In this case, taking into consideration the tension of the first needle thread T1 and the like acting on the thread holding part 9b, it is preferable that the contact part 9c is configured to be located above the cylindrical cam 10.

[0037] In addition, although the cylindrical cam 10 in this embodiment has two cam surfaces, the left cam surface 10b and the right cam surface 10c, the number of cam surfaces may be three or more. In addition, although the left cam surface 10b is configured to have a larger cam lift amount than the right cam surface 10c in this embodiment, the right cam surface 10c may be configured to have a larger cam lift amount. If the cam lift amount of the right cam surface 10c is larger, it is preferable to configure the compression spring 11 to be located on the right side of the cylindrical cam 10, taking into consideration the step portion 10e. [Explanation of symbols]

[0038] 1: Sewing machine 2: Balance switching mechanism 3: Upper shaft 9: Balance 9b: Thread holding part 9c: Contact part 9d:Fulcrum part 10: Cylindrical cam 10b: Left cam surface 10c: Right cam surface 12: Switching body

Claims

1. A lever change mechanism that is provided in a double chainstitch sewing machine and can change the operation of a lever that is linked to an upper shaft, a cylindrical cam having a plurality of cam surfaces and attached to an outer periphery of the upper shaft so as to be slidable in an axial direction of the upper shaft; a contact portion provided on the balance and adapted to come into contact with any one of the cam surfaces; a switching body that switches a position of the cylindrical cam relative to the contact portion in the axial direction, A plurality of cam surfaces having different cam profiles are provided on an outer peripheral surface of the cylindrical cam and aligned in the axial direction, The switching body is a balance switching mechanism that slides the cylindrical cam from a position where one of the multiple cam surfaces contacts the contact portion to a position where another of the multiple cam surfaces contacts the contact portion.

2. 2. The balance switching mechanism according to claim 1, wherein one of the plurality of cam surfaces is set so that the timing at which the balance descends from the highest point is earlier than that of the other of the cam surfaces.

3. 2. The balance switching mechanism according to claim 1, wherein one of the plurality of cam surfaces is set so that the highest point of the balance is higher than another of the cam surfaces.

4. A balance change mechanism provided in a double chainstitch sewing machine, capable of changing the operation of a balance linked to an upper shaft, a cylindrical cam provided on the upper shaft and including a plurality of cam surfaces; a contact portion provided on the balance and adapted to come into contact with any one of the cam surfaces; a switching body that changes the contact portion from a position where the contact portion contacts one of the plurality of cam surfaces to a position where the contact portion contacts another of the plurality of cam surfaces, The balance swings around a fulcrum portion to move the thread holding portion up and down, and when the fulcrum portion is located between the thread holding portion and the contact portion, the contact portion is located below the cylindrical cam, and when the contact portion is located between the thread holding portion and the fulcrum portion, the contact portion is located above the cylindrical cam.

5. A sewing machine comprising the thread take-up switch mechanism according to any one of claims 1 to 4.

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