EP2524987B1

EP2524987B1 - Sewing machine

Info

Publication number: EP2524987B1
Application number: EP20120168200
Authority: EP
Inventors: Shinichi Sakamoto
Original assignee: Juki Corp
Current assignee: Juki Corp
Priority date: 2011-05-18
Filing date: 2012-05-16
Publication date: 2014-05-14
Anticipated expiration: 2032-05-16
Also published as: CN102808295A; JP2012254287A; JP6031255B2; CN102808295B; EP2524987A1

Description

The present invention relates to a sewing machine equipped with a lower thread cutting device disposed inside a bed.
A sewing machine according to a related art is disclosed in, for example, JP2003-154184A .
With reference to Fig. 21 and Fig. 22, a thread cutting device that cuts a lower thread T by clipping it from above and below will be described. The lower thread T connected to a cloth extends substantially horizontally below an upper plane surface of a cloth feed base between an eye of a throat plate and the cloth when finishing sewing. The thread cutting device 100 includes a lower moving knife 101 including an edge portion 101A and an upper moving knife 102 including an edge portion 102A. The lower moving knife 101 and the upper moving knife 102 are supported rotatably around a horizontal axis. When cutting the thread, while advancing the lower and upper moving knives 101 and 102, by rotating the lower moving knife 101 so that the edge portions 101A, 102A cross each other, the edge portions 101A, 102A clip and cut the lower thread T extending horizontally. The thread cutting device 100 further includes a guide member 103 for guiding the lower thread T to the position between the edge portions 101A, 102A. The guide member 103 extends above the upper moving knife 102. Specifically, when the moving knives 101 and 102 advance so as to cross the path of the lower thread T, the guide member 103 moves integrally with the moving knives 101 and 102 and pushes the lower thread T down so as to position the lower thread T on the path of both moving knives 101 and 102.
However, in some cases where the tension of the lower thread T is too strong, the lower thread T slides on the guide member 103, and the lower thread T enters the space between the guide member 103 and the upper moving knife 102 and deviates from the path of the edge portions 101A, 102A, and it becomes impossible to cut the lower thread T.
An object of the present invention is to provide a sewing machine capable of reliably cutting a lower thread without using a guide member that is provided integrally with a pair of moving knives.
According to an aspect of the present invention, a sewing machine includes a cloth feed base on which a cloth is placed, a stitch forming means for forming stitches by an upper thread and a lower thread on the cloth placed on the cloth feed base, and a thread cutting device disposed below the cloth feed base and having a lower knife and an upper knife that cuts the lower thread in cooperation with the lower knife. The cloth feed base has a bulged portion protruding upward to separate the lower thread and the cloth from each other. The bulged portion has a portion defining at least a part of a gap portion serving as a movement path of the upper knife, the movement path being above the lower surface of the cloth feed base.
According to an aspect of the present invention, the bulged portion protruding upward is provided on the cloth feed base to separate the lower thread and the cloth, and the bulged portion is provided to form a gap portion serving as the movement path of the upper knife and the lower knife, so that the upper knife can be guided to the gap formed between the thread and the cloth by the bulged portion, and the lower thread can be reliably cut. After the cutting, the shorter the remaining length of the lower thread connected to the cloth, the higher the sewing quality, and for realizing this, the lower thread path may be arranged along the cloth feed base (along the cloth), that is, along the horizontal direction. However, in the conventional case, the upper and lower knives move below the cloth feed base, so that if the lower thread path is made parallel to the cloth feed base, the lower thread cannot be captured by the upper and lower knives. According to the present invention, even when the lower thread path is set to extend along the cloth (along the cloth feed base) as much as possible, the movement path of the upper and lower knives can reliably capture and cut the lower thread, so that the lower thread can be reliably cut, and the remaining length of the thread connected to the cloth can be shortened. Further, even without using a guide member provided integrally with the upper and lower knives, the lower thread can be reliably cut.
Other aspects and advantages of the present invention will be apparent from the following description, drawings, and the claims.
The following description of embodiments of the present invention describes the present invention in greater detail with reference to the drawings including:

Fig. 1:: a side view of a sewing machine according to an embodiment of the present invention;
Fig. 2:: a top view of a cloth feed base of the sewing machine at the time when the sewing is finished;
Fig. 3:: a perspective view showing a schematic configuration of a bulged portion of the cloth feed base;
Fig. 4:: a front perspective view of a lower thread cutting device in a closed condition;
Fig. 5:: a rear perspective view of the lower thread cutting device;
Fig. 6:: a rear view of the back side of the lower thread cutting device;
Fig. 7:: a back view of the lower thread cutting device in which a thread cutting lever is not illustrated;
Fig. 8:: a front perspective view of the lower thread cutting device in an opened condition;
Fig. 9:: a rear perspective view of the lower thread cutting device in the opened condition;
Fig. 10:: a perspective view showing a positional relationship between the lower thread cutting device and the bulged portion of the cloth feed base in the present embodiment;
Fig. 11:: a perspective view showing a groove of the cloth feed base shown in Fig. 3;
Fig. 12:: a perspective view showing a state during thread-cutting by the thread cutting device according to the present embodiment;
Fig. 13:: a perspective view showing a state during the thread-cutting by the thread cutting device according to the present embodiment;
Fig. 14:: a top view of a modification of a cloth feed base provided in the sewing machine;
Fig. 15:: a perspective view showing a schematic configuration of a bulged portion of the cloth feed base shown in Fig. 14;
Fig. 16:: an exploded perspective view of a modification of a thread cutting device;
Fig. 17:: a front perspective view of the lower thread cutting device shown in Fig. 16;
Fig. 18:: a rear perspective view of the lower thread cutting device shown in Fig. 16;
Fig. 19:: a rear view of the lower thread cutting device shown in Fig. 16;
Fig. 20:: a front perspective view illustrating an opened condition of the lower thread cutting device shown in Fig. 16;
Fig. 21:: a perspective view of a conventional thread cutting device; and
Fig. 22:: another perspective view of the thread cutting device shown in Fig. 21.

A sewing machine 10 according to an embodiment shown in Fig. 1 and Fig. 2 is an automatic-control eyelet sewing machine that forms overlock stitches and a buttonhole B on a cloth H.
The sewing machine 10 includes a bed portion 11 having a substantially rectangular box shape, a vertical drum portion 12 provided on the rear portion of the bed portion 11, an arm portion 13 extending forward substantially parallel to the bed portion 11 from the upper portion of the vertical drum portion 12, a cloth feed base 16 on which a cloth (workpiece) H is placed and which moves the cloth within a horizontal plane, a cloth presser 17 that presses the cloth H against the upper surface of the cloth feed base 16, a cloth cutting knife 41 for forming a buttonhole and a knife receiver 42.
The upper shaft is provided to extend in the front-rear direction (Y direction in Fig. 1) of the arm portion 13 inside the arm portion 13. In the arm portion, the upper shaft that is rotated by a main shaft motor not illustrated is provided to extend in the front-rear direction. A lower shaft is connected to the upper shaft via a transmission mechanism including a timing belt, and a rotative force of the upper shaft is transmitted via the transmission mechanism to rotate the lower shaft.
In the front head portion 13a of the arm portion 13, a needle bar 15 is provided so as to be moved up and down by a known needle bar up-down drive mechanism (not illustrated) that is driven by the upper shaft and to be moved for needle oscillation in the left-right direction (X direction in Fig. 2) by a known needle oscillation mechanism (not illustrated). To the lower end portion of the needle bar 15, a sewing machine needle 14 is fixed, and through a thread insertion hole at the tip end (lower end) of the sewing machine needle 14, an upper thread is inserted. The sewing machine needle 14 projects downward and withdraws by penetrating through an eye (not illustrated) made in a throat plate 11A (Fig. 2) provided in the bed portion 11 according to up-down movements of the needle bar 15. The needle oscillation mechanism has a conventional configuration that enables mechanical adjustment of the needle oscillation width.
In the bed portion 11, a looper (not illustrated) having a hole on the tip end through which the lower thread T2 is inserted is provided just below the throat plate 11A. The looper is connected to the lower shaft and swings in synch with the up-down movements of the needle bar 15. By the cooperation of the looper that swings and the sewing machine needle 14 that moves up and down by penetrating through the throat plate 11, the upper thread T1 and the lower thread T2 interlace with each other to form buttonholing chainstitches. The sewing machine needle 14 and the looper form a stitch forming means. The stitch forming means in the present invention is not limited to the sewing machine needle 14 and looper of the present embodiment, and includes other known stitch forming means.
The needle bar 15 and the looper are connected to a turning mechanism 71 having a turning pulse motor and a timing belt, rotate around a vertical axis in synch with each other, and accordingly, eyelet sewing stitches are formed on the peripheral edge portion of an droplet-shaped eyelet forming a part of a buttonhole.
The cloth feed base 16 that is in a hollow rectangular shape as a whole is provided movably on the upper surface of the bed portion 11, and is movable in the left-right direction (X direction) and the front-rear direction (Y direction) by operations of an X-axis pulse motor and a Y-axis pulse motor provided inside the bed portion 11.
A cloth H can be placed on the upper surface of the cloth feed base 16, and the cloth presser 17 is provided on the cloth feed base 16 so as to move up and down to press or release the cloth H against or from the upper surface of the cloth feed base 16. The cloth presser 17 presses both sides of buttonhole stitches that should be formed on the cloth H. This cloth feed base 16 is set so that the cloth cutting knife 41 and the knife receiver 42 face each other above and below a position at which the buttonhole B is to be formed on the cloth H placed on the upper surface of the cloth feed base in a state where the cloth feed base is positioned at a predetermined origin, and at this position, the buttonhole B is formed.
The cloth feed base 16 moves to a sewing start position ahead (right in Fig. 2) of the origin according to starting of the sewing machine, and is driven so that the cloth H placed on the cloth feed base 16 relatively moves to a necessary position just below the sewing machine needle 14. In cooperation with this driving, the needle bar 15, the looper, and the turning mechanism 71 are driven, and accordingly, overlock stitches are formed around the buttonhole B.
After sewing is completed, the cloth feed base 16 moves in the Y direction from the final stitch formed position, and moves the cloth so that the portion at which the buttonhole B is to be formed comes to a position facing the cloth cutting knife 41 and the knife receiver 42, and the state shown in Fig. 2 is obtained. At this time, between the eye of the throat plate 11A and the final stitch formed position on the cloth H, the lower thread T2 extends along the Y direction.
The cloth cutting knife 41 is disposed on one side (rear side) in the Y direction of the position at which the looper is provided in the bed portion 11, and disposed at a position matching the origin of the cloth feed base 16 as described above.
Then, when the cloth H reaches the cloth cutting position, that is, when the cloth H is disposed between the knife receiver 42 and the cloth cutting knife 41, the knife receiver 42 moves down toward the cloth cutting knife 41 by an operation of a drive means (not illustrated) such as an air cylinder. By this downward movement, the cloth H set between the knife receiver 42 and the cloth cutting knife 41 is pushed and cut, and accordingly, the buttonhole B is formed.
Near the moving-up/down region of the sewing machine needle 14 of the cloth feed base 16, a bulged portion 161 long in the Y direction and divided substantially bilaterally symmetrically is formed. The cloth cutting knife-side end edge of this bulged portion 161 is formed straight along the X direction, and protrudes upward so that a level difference is formed between this and the upper plane surface of the cloth feed base 16. Accordingly, as shown in Fig. 13, the cloth H on the cloth feed base 16 is bent at the boundary between the upper end face of the cloth feed base 16 and the upper surface of the bulged portion 161.
In the bulged portion 161, a substantially oval hole portion 162 opened so as to expose the upper side of the throat plate 11A and a guide hole portion 162A opened on the Y-axis direction line passing through the center of the hole portion 162 are formed along the Y direction. The oval shape along the Y direction of the hole portion 162 is for allowing the throat plate 11A to relatively move according to movement of the cloth feed base 16.
When finishing sewing, the lower thread T2 passing between the cloth H and the throat plate 11A passes through the inside of the guide hole portion 162 and becomes almost straight. On the other hand, the cloth H positioned on the upper end face of the cloth feed base 16 and pressed by the cloth presser 17 is bent at the boundary with the upper surface of the bulged portion 161. Therefore, the paths of the bent cloth H and the lower thread T2 are separated up and down at the bulged portion 161.
At the end portion on the cloth presser 17 side of the hole portion 162, a groove 163 opened to the guide hole portion 162A is formed, and the groove 163 extends along the X direction with a predetermined width K in the Y direction (Fig. 11) and forms a gap portion. Specifically, the cloth feed base 16 includes the bulged portion 161 protruding upward for separating the lower thread T2 and the cloth H from each other and a groove 163 that is formed in the bulged portion 161 along the X direction and forms a gap portion as a movement path above the lower surface of the cloth feed base 16 of the movement path of the upper knife 52. The bulged portion 161 is fixed to the cloth feed base 16 via a cloth feed plate by attaching screws not illustrated in a plurality of fixation holes provided along the front-rear direction. By selecting fixation holes, the attaching position of the bulged portion 161 can be changed along the front-rear direction Y.
The sewing machine 10 includes an upper thread cutting device (not illustrated) that cuts the upper thread T1 and a lower thread cutting device 50 (thread cutting device) that cuts the lower thread T2. The upper thread cutting device may use a known thread cutting structure, so that description thereof is omitted.
The lower thread cutting device 50 is disposed below the cloth feed base 16 as shown in Fig. 1.
As shown in Fig. 4 to Fig. 6, the lower thread cutting device 50 includes a lower knife 51 in a narrow and long plate shape having an edge portion 51A formed on the tip end lower side edge, an upper knife 52 in a narrow and long plate shape having an intermediate portion joined rotatably to the lower knife 51 by a support shaft 56 and an edge portion 52A formed on the tip end upper side edge, an air cylinder 53 as an actuator fixed to the bed 11, a link mechanism 54 that transmits extending and contracting movements of the air cylinder 53 to the lower knife 51 and the upper knife 52 and rotates the lower knife 51 and the upper knife 52 around the support shaft 56 to make the edge portions 51A and 52A approach and separate from each other (open and close), and a support base 55 that is fixed to the bed 11 and support the components described above.
The support base 55 formed by bending a plane plate material includes a bottom portion 553 extending horizontally, a first wall portion 551 as a wall portion that is bent along the X direction line from the bottom portion 553 to stand to support the link mechanism 54, and a second wall portion 552 that is bent along the Y direction line from the bottom portion 553 to stand to fix and support the air cylinder 53. In the bottom portion 553, a plurality of slots 554 extending in the Y direction are formed, and the support base is fixed to and positioned on the bed portion 11 (sewing machine frame) by inserting fixation screws 555 (guide members) through the slots 554. By loosening the fixation screws 555 and sliding the support base 55 in the range of the lengths of the slots 554, position adjustment in the Y direction can be made. The guide members are not limited to screws, and may be other known members fixable to the bed portion 11.
In the bottom portion 553 from which the first wall portion 551 stands, the plurality of slots 554 along the front-rear direction are formed, and by inserting the guide members 555 through the slots 554 and sliding the thread cutting device 50 with respect to the bed portion 11, the thread cutting position is adjustable along the front-rear direction.
The air cylinder 53 includes a pair of rods 531 that can extend and contract in the up-down direction, and to the upper portions of the pair of rods 531, an engagement piece 532 bent in a substantially L shape is fixed. To the bent portion of the engagement piece 532, the link mechanism 54 is joined.
The link mechanism 54 includes a first link mechanism and a second link mechanism. The first link mechanism includes a first link member 541 and an L-shaped thread cutting lever 542. The first link member 541 extends in the up-down direction. The first link member 541 has an upper end portion joined to and supported on the engagement piece 532 rotatably, and a lower end portion joined to the thread cutting lever 542. The thread cutting lever 542 has a horizontal end portion joined to the lower end portion of the first link member 541, and an intermediate portion supported rotatably on the first wall portion 551 by a support shaft 543. The first link mechanism is disposed on the inner wall surface side of the first wall portion 551.
In the upper end portion of the thread cutting lever 542, a slot 544 long along the longitudinal direction (up-down direction) is formed.
When the rods 531 of the air cylinder 53 move up and down, in conjunction with this movement, the first link member 541 moves up and down, and the thread cutting lever 542 rotates around the support shaft 543.
The second link mechanism of the link mechanism 54 includes a second link member 545 and a third link member 546. The second link member 545 has a lower end portion supported rotatably on the first wall portion 551 and an upper end portion joined rotatably to the base end portion of the upper knife 52. The third link member 546 has a lower end portion supported rotatably on the first wall portion 551 and an upper end portion joined rotatably to the center portion side of the upper knife 52. The second link mechanism is disposed on the outer wall surface side of the first wall portion 551. The second link member 545 and the third link member 546 are parallel to each other.
As shown in Fig. 8, at the center portion of the third link member 546, a convex portion 547 convexed outward is formed. To the convex portion 547, the lower end portion of the fourth link member 548 that joins the third link member 546 and the lower knife 51 is joined rotatably. The upper end portion of the fourth link member 548 is joined rotatably to the base end portion of the lower knife 51 by a support shaft 57. To the support shaft 57, a pin 549 is attached, and the pin 549 fits in the slot 544 of the thread cutting lever 542 slidably in the longitudinal direction and rotatably. This pin 549 transmits the swing of the thread cutting lever 542 around the support shaft 543 to the fourth link member 548, so that the fourth link member 548 swings the third link member 546 by following the swing of the thread cutting lever 542. Accordingly, the second link 545 and the third link member 546 swing around their lower ends, and the upper knife 52 swings in the X direction.
The support shaft 57 supporting the pin 549 is joined to the lower knife 51, so that the lower knife 51 swings around the support shaft 56, and both edge portions 52A and 51A open and close (approach or separate from each other).
Specifically, the link mechanism 54 includes a second link member 545 having one end portion joined rotatably to the base end portion of the upper knife 52 and the other end portion supported rotatably on the wall portion 551, and a third link member 546 provided parallel to the second link member 545 and having one end portion joined rotatably to the center portion of the upper knife 52 and the other end portion supported rotatably on the wall portion 551, and the upper knife 52 and the lower knife 51 is opened and closed by a pantograph mechanism formed by the second link member 545, the third link member 546, the upper knife 52, and the wall portion 551.
The link mechanism 54 includes the thread cutting lever 542 having one end portion supported rotatably on the wall portion 551 and the other end portion in which a slot 544 is formed, and the fourth link member 548 having one end portion joined rotatably to the lower knife 51 via the slot 544 of the thread cutting lever 542 and the other end portion joined rotatably to the third link member 546, and the lower knife 51 is interlocked with the thread cutting lever 542 and the pantograph mechanism is also interlocked with the thread cutting lever 542 by a toggle mechanism formed by the upper knife 52, the fourth link member 548, and the thread cutting lever 542.
Hereinafter, operations of the lower thread cutting device 50 are described in detail.
Fig. 4 to Fig. 6 show a case where the lower knife 51 and the upper knife 52 are in a closed state. In this state, the rods 531 of the air cylinder 53 extend and the engagement piece 532 is positioned at the upper position. When the rods 531 contract, the engagement piece 532 moves down, so that the first link member 541 whose upper end is supported by the engagement piece 532 also moves down to rotate the thread cutting lever 542 in the arrow Y1 direction.
The rotative movement is transmitted to the fourth link member 548 via the pin 549, and the fourth link member 548 also moves in the arrow Y1 direction (Fig. 7). Accordingly, the second link member 545, the third link member 546, the lower knife 51, and the upper knife 52 also move in the arrow Y1 direction. At this time, the pin 549 slides inside the slot 544, so that the positional relationship between the lower knife 51 and the upper knife 52 changes and they open as shown in Fig. 8 and Fig. 9.
From the opened state, when the rods 531 of the air cylinder 53 extend, the first link member 541 also moves up to rotate the thread cutting lever 542 in the arrow Y2 direction. This rotative movement is transmitted to the fourth link member 548 via the pin 549, and the fourth link member 548 also moves in the arrow Y2 direction. Accordingly, the second link member 545, the third link member 546, the lower knife 51, and the upper knife 52 also move in the arrow Y2 direction. At this time, the pin 549 slides inside the slot 544, so that the positional relationship between the lower knife 51 and the upper knife 52 changes and they open as shown in Fig. 4 to Fig. 6.
A pantograph mechanism is formed by the second link member 545, the third link member 546, the upper knife 52, and the first wall portion 551. This pantograph mechanism is interlocked by a toggle mechanism formed by the upper knife 52, the fourth link member 548, and the thread cutting lever 542. In detail, the upper knife 52 and the fourth link member 548 are moved by a biasing force of the thread cutting lever 542, and closed with respect to the lower knife 51. The fourth link member 548 and the lower knife 51 form a toggle mechanism, so that at the moment of thread cutting at which the lower knife 51 and the upper knife 52 close to each other, a great force can be generated.
Then, when moving the upper knife 52 to the thread cutting position by actuation of the air cylinder 53, as shown in Fig. 10, the upper knife 52 is disposed so that its movement path is set to make the upper knife 52 enter the groove 163 of the cloth feed base 16. As shown in Fig. 11, the predetermined width K of the groove 163 is formed to a length that allows the upper knife 52 to move according to a position adjustable range of the lower thread cutting device 50.
At the time of thread cutting, as shown in Fig. 12, the lower thread T2 and the cloth H are separated from each other by the bulged portion 161 of the cloth feed base 16 to form a space. At this time, the cloth H may be left pressed by the cloth presser 17.
The upper knife 52 in an opened state is housed inside the groove 163 of the cloth feed base 16, so that the point of the upper knife 52 is positioned so that it can pass through the space between the lower thread T2 and the cloth H. When the lower thread cutting device 50 switches to a closed state, as shown in Fig. 13, the upper knife 52 gradually shortens its distance to the lower knife 51 while being guided by the groove 163, and finally, the upper knife 52 and the lower knife 51 close to each other, and accordingly, the lower thread T2 is cut.
As described above, the lower thread cutting device 50 is slidable in the Y direction in the range of the lengths of the slots 554, so that by adjusting the position of the lower thread cutting device 50 before thread cutting, the cutting position of the lower thread T2 can also be adjusted.
As described above, according to the present embodiment, on the cloth feed base 16, the bulged portion 161 protruding upward to separate the lower thread T2 and the cloth H from each other is provided, and the groove 163 serving as a movement path of the upper knife 52 is formed in the bulged portion 161, so that the upper knife 52 can be guided into the space between the lower thread T2 and the cloth H formed by the bulged portion 161, and the lower thread T2 can be reliably cut. Therefore, without using a guide member integral with the pair of moving knives which is used in the conventional case, the lower thread T2 can be reliably cut.
Conventionally, a state where the upper knife easily enters the position between the cloth H and the cloth feed base 16 must be formed by releasing the cloth H from the cloth feed base 16. Therefore, cutting of the lower thread T2 was performed after the cloth presser 17 moved up and released the cloth H. On the other hand, in the sewing machine 10 of the present embodiment, a space is formed in advance between the cloth H and the lower thread T2 by the bulged portion 161, so that thread cutting can be performed in the state where the cloth is pressed by the cloth presser 17. In this case, the lower thread T2 can be cut while the cloth feed base 16 moves from the sewing finish position to the position at which the buttonhole B is formed. Specifically, cutting of the lower thread T2 can be performed in combination with other operations, so that the total sewing time for buttonholing can be shortened.
The position at which the lower thread T2 is cut by the lower thread cutting device 50 is adjustable by sliding the support base 55a along the thread extending direction (Y direction), so that the length of the lower thread T2 after it is cut can be adjusted.
The upper knife 52 and the lower knife 51 are opened and closed by a pantograph mechanism, so that the upper knife 52 and the lower knife 51 can be opened and closed by a simple configuration.
Further, the pantograph mechanism includes a toggle mechanism, so that the thread can be reliably cut even if the external force for cutting is small.
Further, in the sewing machine 10 according to the embodiment described above, a case where the groove 163 is entirely formed by the bulged portion 161 is illustrated and described, however, it is also possible that at least a part of the groove is formed by the bulged portion. Hereinafter, a modification of the sewing machine is described. In the following description, the same components as in the embodiment described above are denoted with the same reference numerals and description thereof is omitted.
As shown in Fig. 14 and Fig. 15, the right side (lower thread cutting device 50a side) bulged portion 161a of the pair of left and right bulged portions 161a and 161b is shorter in the Y direction than the left side (opposite) bulged portion 161b. In the upper surface of the cloth feed base 16a, a notched portion 164a extending in the X direction is formed below the portion on the inner side (cloth presser 17 side) of the bulged portion 161a so as to face this portion. The bulged portion 161a is separated from the cloth presser 17 so that a gap portion 163a is formed by the end face of the notched portion 164a of the cloth feed base 16a and the inner end face of the right side bulged portion 161a. This gap portion 163a becomes a movement path of the upper knife 52.
The inner side end portion of the bulged portion 161a has a recessed shape curved as a whole, and on the other hand, the inner side end portion of the bulged portion 161b curves only at the end portion on the front side, and the other portion is formed by straight notching. Accordingly, the region on the extension of the movement path of the upper knife 52 can be formed as a space to prevent the left side bulged portion 161b from interfering with the upper knife 52.
Next, a modification of a lower thread cutting device is described with reference to Fig. 16 to Fig .20. As shown in Fig. 16 to Fig. 19, the lower thread cutting device 50A has a structure substantially similar to the structure of the lower thread cutting device 50 according to the above-described embodiment. Specifically, the lower thread cutting device 50A includes a lower knife 51a for cutting a thread, an upper knife 52a that is supported rotatably by the lower knife 51a, opens and closes substantially along the up-down direction, and cuts a thread in cooperation with the lower knife 51a, an air cylinder 53a as an actuator serving as a drive source, a link mechanism 54a that conducts an extending/contracting movement of the air cylinder 53a to the lower knife 51a and the upper knife 52a and makes edge portions of these lower knife 51a and upper knife 52a approach or separate from each other (open and close), and a support base 55a that supports these components.
The upper knife 52a is bent so that the base end portion thereof is spaced from the lower knife 51a. The support base 55a includes a wall portion 551a for supporting the link mechanism 54a and a bottom portion 553a extending horizontally from the lower end portion of the wall portion 551a. To the bottom portion 553a, a block member 556a for fixing the air cylinder 53a to the bottom portion 553a is attached. The block member 556a is fixed to the bottom portion 553a of the support base 55a by auxiliary screws 558a inserted through the through holes 557a. On the surface facing the air cylinder 53a of the block member 556a, a screw hole (not illustrated) for fixing the air cylinder 53a is formed. In the block member 556a, a slot 556ab is formed in the Y direction (front-rear direction). In the bottom portion 553a of the support base 55a, slots 554a along the Y direction (thread extending direction or the front-rear direction) are formed. The support base 55a is positionally adjusted along the Y direction by the slots 554a and 556ab, and fixed to the sewing machine frame at a predetermined position by fixation screws 555a. The slots 554a are formed in the block member 556a, the slot 556ab is formed in the support base 55a, respectively, however, it is also easily conceived that a plurality of slots are provided in the block member 556a or the support base 55a to adjust the position of the support base 55a.
A pair of rods 531a of the air cylinder 53a can extend and contract in the up-down direction, and to upper portions of the pair of rods 531a, an engagement piece 532a that engages with the link mechanism 54a is attached. The engagement piece 532a is fixed to the pair of rods 531a by flat head screws 69a. When the flat head screws 69a are used, space-saving can be realized more than in the case using hexagon socket head bolts. One end portion of the engagement piece 532a is bent downward, and this bent portion is joined to the link mechanism 54a.
In the air cylinder 53a, through holes 533a are formed to face the screw holes of the block member 556a. By screwing fixation screws 534a to the screw holes of the block member 556a via the through holes 533a, the air cylinder 53a is fixed to the block member 556a.
The link mechanism 54a includes a first link member 541a whose one end portion is joined rotatably to the engagement piece 532a and an L-shaped thread cutting lever 542a joined to the other end portion of the first link member 541a, and these are disposed on the inner wall surface side of the wall portion 551a.
By following the extending/contracting movement of the air cylinder 53a via the engagement piece 532a, the first link member 541a transmits power of the air cylinder 53a to the thread cutting lever 542a. On the other end portion of the first link member 541a, a projection 541b is formed.
An intermediate portion of the thread cutting lever 542a is supported rotatably on the wall portion 551a by a support shaft 543a. An end portion of the shorter side portion of the thread cutting lever 542a is joined rotatably to the first link member 541a, and an end portion of the longer side portion projects from the wall portion 551a. In the end portion (the other end portion) of the longer side portion of the thread cutting lever 542a, a slot 544a is formed.
When the rods 531a of the air cylinder 53a move up and down, in conjunction with this, the first link member 541a moves up and down, and the thread cutting lever 542a rotates around the support shaft 543a.
The link mechanism 54a includes a second link member 545a joined to the base end portion of the upper knife 52a and a third link member 546a joined to the center portion of the upper knife 52a, and these are disposed on the outer wall surface side of the wall portion 551a. The second link member 545a and the third link member 546a are parallel to each other. One end portion of the second link member 545a is joined rotatably to the base end portion of the upper knife 52a, and the other end portion is supported rotatably on the wall portion 551a. In the portion on which the other end portion of the second link member 545a is supported of the wall portion 551a, a slot 551b extending along the up-down direction is formed. By moving a rotary shaft 545c of the other end portion of the second link member 545a in the up-down direction along the slot 551b, the position of the upper knife 52a can be adjusted.
Here, the base end portion of the upper knife 52a is bent, so that the base end portion of the upper knife 52a engages with the outer side surfaces of the second link member 545a and the third link member 546a. On one end portion of the third link member 546a, a shaft body 546b integrated with the third link member is provided, and the center portion of the upper knife 52a is joined rotatably to this shaft body 546b via a thrust collar 60a. The shaft body 546b is integrated with the third link member 546a, so that the strength can be improved, and by the thrust collar 60a, the upper knife 52a is prevented from rattling. On the other hand, the other end portion of the third link member 546a is supported rotatably on the wall portion 551a.
On the center portion of the third link member 546a, a convex portion 547a convexed outward is formed, and to this convex portion 547a, a fourth link member 548a that joins the third link member 546a and the lower knife 51a is joined via a shoulder screw 61a. The fourth link member 548a is held and joined by the shoulder screw 61a, so that the lower knife 51a can be prevented from rattling.
The shaft 62a of the shoulder screw 61a is eccentric with the screw head 63a. The shaft 62a of the shoulder screw 61a passes through the base end portion of the lower knife 51 and is fixed to the fourth link member 548a by a set screw 64a. Here, when fixation by the set screw 64a is released and the screw head 63a of the shoulder screw 61a is rotated, the shaft 62a rotates around the rotation axis of the screw head 63a, and the position of the shaft 62a changes. According to this change, the position of the base end portion of the lower knife 51a also changes, and the opening/closing position of the tip end portion of the lower knife 51 is adjusted.
To one end portion of the fourth link member 548a, a pin 549a that engages in the slot 544a of the thread cutting lever 542a is attached via a washer 549b and a shoulder screw 549c. The shoulder screw 549c and one end portion of the fourth link member 548a hold the pin 549a therebetween, so that rattling in the axial direction is prevented.
The pin 549a transmits the rotative movement of the thread cutting lever 542a to the fourth link member 548a, so that the fourth link member 548a swings the third link member 546a by following the rotative movement of the thread cutting lever 542a. The movement of the third link member 546a is also transmitted to the second link member 545a via the upper knife 52a, so that the upper knife 52a and the second link member 545a also swing together with the third link member 546a. The fourth link member 548a moves the lower knife 51a as well, so that the lower knife 51a and the upper knife 52a have opening and closing movements. In Fig. 20, the case where the lower knife 51a and the upper knife 52a are in an opened state is shown.
By changing the position of the second link member 545a by rotating the shoulder screw 61a and moving the rotary shaft 545c in the up-down direction, the positions in the up-down direction of the lower knife 51a and the upper knife 52a can be adjusted (for example, refer to the alternate long and two short dashed line shown in Fig. 19). In detail, in the state where fixation by the set screw 64a is released, when the rotary shaft 545c is moved up or down along the slot 551b, by following this up or down movement, the position of the other end portion of the second link member 545a changes, and the position of the upper knife 52a also changes. When the position of the upper knife 52a is adjusted, in conjunction with this, the lower knife 51a also moves, and at this time, fixation by the set screw 64a is released, so that without restricting the movement of the lower knife 51a, the fourth link member 548a and the shoulder screw 61a move by following this movement. Specifically, the knife position adjustment mechanism that performs positional adjustment of the lower knife 51a and the upper knife 52a includes the slot 551b of the wall portion 551a, the rotary shaft 545c, the second link member 545a, the shoulder screw 61a, and the fourth link member 548a. Thus, by providing the knife position adjustment mechanism for the second link member 545a and the fourth link member 548a, the positions of the lower knife 51a and the upper knife 52a can be adjusted.
Further, the lower thread cutting device 50A is provided with a stopper member 80a for adjusting the movable range of the first link member 541a. The stopper member 80a includes a base portion 81a attached to the wall portion 551a and a restricting portion 82a that is bent with respect to the base portion 81a and extends in the up-down direction.
In the base portion 81a, a pair of slots 84a extending in the up-down direction are formed, and by inserting fixation screws 85a through the slots 84a and screwing these to the wall portion 551a, the base portion 81a is fixed to the wall portion 551a. By moving up and down the base portion 81a along the slots 84a via the fixation screws 85a, the position in the up-down direction of the whole stopper member 80a can be adjusted.
In the restricting portion 82a, a guide hole 83a extending in the up-down direction is formed, and the projection 541b of the first link member 541a engages in this guide hole 83a. By adjusting the position in the up-down direction of the stopper member 80a, the upper end position of the guide hole 83a is also adjusted, so that the top dead point of the projection 541b of the first link member 541a, that is, the movable range of the upper side of the first link member 541a can be changed.
Thus, the stopper member 80a that adjusts the movable range of the first link member 541a is attached to the support base 55a in a position adjustable manner, so that by adjusting the position of the stopper member 80a, the movable range of the first link member 541a can be adjusted.
The present invention is not limited to the embodiments described above, but is changeable as appropriate.
For example, in the embodiment described above, the case where the drive source of the lower thread cutting device 50 is the air cylinder 53 is illustrated and described, however, for example, other actuators such as a motor or solenoid can also be used as the drive source.

Claims

A sewing machine (10) comprising:
a cloth feed base (16, 16a) on which a cloth (H) is placed;

a stitch forming means (14) for forming stitches by an upper thread (T1) and a lower thread (T2) on the cloth (H) placed on the cloth feed base (16, 16a); and

a thread cutting device (50, 50A) disposed below the cloth feed base (16, 16a) and having a lower knife (51, 51a) and an upper knife (52, 52a) that cuts the lower thread (T2) in cooperation with the lower knife (51, 51a),

characterized in that

the cloth feed base (16, 16a) has a bulged portion (161, 161a) protruding upward to separate the lower thread and the cloth from each other, and

the bulged portion (161, 161a) has a portion defining at least a part of a gap portion (163, 163a) serving as a movement path of the upper knife (52, 52a), the movement path being above a lower surface of the cloth feed base (16, 16a).
The sewing machine (10) according to claim 1, wherein the gap portion (163) is configured as a groove formed in the bulged portion (161).
The sewing machine (10) according to claim 1, wherein the gap portion (163a) is formed by a notched portion (164a) formed in the cloth feed base (16a) to allow the upper knife (52a) to pass through, and an end portion of the bulged portion (161a).
The sewing machine (10) according to claim 3, wherein the cloth feed base (16a) further includes another bulged portion (161b) disposed in a separated manner from the bulged portion (161a), and a face of the other bulged portion (161b) facing the gap portion (163a) has a shape that is spaced away from the movement path of the upper knife (52a).
The sewing machine (10) according to claim 1, wherein the thread cutting device (50, 50A) comprises:
a link mechanism (54, 54a) for opening and closing the upper knife (52, 52a) and the lower knife (51, 51 a), and

a support base (55, 55a) supporting the upper knife (52, 52a), the lower knife (51, 51a), and the link mechanism (54, 54a),

wherein the support base (55, 55a) is provided such that a position of the support base (55, 55a) is adjustable relative to a sewing machine frame (11) along a direction intersecting the movement path of the upper knife (52, 52a).
The sewing machine (10) according to claim 5, further comprising:
an actuator (53, 53a) serving as a drive source for the link mechanism (54, 54a),

wherein the link mechanism (54, 54a) comprises a first link member (541, 541a) for transmitting power of the actuator (53, 53a).
The sewing machine (10) according to claim 6, wherein the link mechanism (54, 54a) further comprises:
a second link member (545, 545a) having one end portion joined rotatably to a base end portion of the upper knife (52, 52a) and the other end portion supported rotatably on the support base (55, 55a), and

a third link member (546, 546a) provided parallel to the second link member (545, 545a) and having one end portion joined rotatably to a central portion of the upper knife (52, 52a) and the other end portion supported rotatably on the support base (55, 55a),

wherein the upper knife (52, 52a) and the lower knife (51, 51a) are opened and closed by a pantograph mechanism formed by the second link member (545, 545a), the third link member (546, 546a), the upper knife (52, 52a), and the support base (55, 55a).
The sewing machine (10) according to claim 7, wherein the link mechanism (54, 54a) further comprises:
a thread cutting lever (542, 542a) having one end portion supported rotatably on the support base (55, 55a) and the other end portion formed with a slot, and

a fourth link member (548, 548a) having one end portion joined rotatably to the lower knife (51, 51a) via the slot of the thread cutting lever (542, 542a) and the other end portion joined rotatably to the third link member (546, 546a),

wherein the lower knife (51, 51a) interlocks with the thread cutting lever (542, 542a), and the pantograph mechanism also interlocks with the thread cutting lever (542, 542a), by a toggle mechanism formed by the upper knife (52, 52a), the fourth link member (548, 548a) and the thread cutting lever (542, 542a).
The sewing machine (10) according to claim 8, wherein the support base (55, 55a) comprises a wall portion (551, 551a) for supporting the link mechanism (54, 54a) and a bottom portion (553, 553a) extending horizontally from a lower end portion of the support base (55, 55a),
wherein the bottom portion (553, 553a) is formed with a plurality of slots (554, 554a) along a direction intersecting the movement path of the upper knife (52, 52a), and guide members (555, 555a) are inserted through the slots (554, 554a) such that the thread cutting device (50, 50A) slidable to adjust a cutting position of the lower thread (T2) along the direction in which the lower thread (T2) extends.
The sewing machine (10) according to claim 8, wherein the first link member (541a) transmits the power of the actuator (53a) to the thread cutting lever (542a) by following the actuator (53a), and
a stopper member (80a) is attached to the support base (55a) such that a position thereof is adjustable to adjust a movable range of the first link member (541a).
The sewing machine (10) according to claim 8, wherein a knife position adjustment mechanism (551 a, 545c, 61 a, 548a) for adjusting the positions of the lower knife (51, 51a) and the upper knife (52, 52a) is provided to the second link member (545, 545a) and the fourth link member (548, 548a).