EP2508664A1

EP2508664A1 - Sewing machine thread-cutting device

Info

Publication number: EP2508664A1
Application number: EP11747212A
Authority: EP
Inventors: Yoshikazu Suzuki
Original assignee: Jaguar International Corp
Current assignee: Jaguar International Corp
Priority date: 2010-02-23
Filing date: 2011-02-15
Publication date: 2012-10-10
Anticipated expiration: 2031-02-15
Also published as: JP5342692B2; EP2508664A4; JPWO2011105248A1; WO2011105248A1; EP2508664B1

Abstract

The present invention provides a thread cutting device for a sewing machine that reliably hooks and catches a thread and guides it to a fixed blade. Furthermore, the present invention provides a thread cutting device for a sewing machine whose maintenance such as a replacement of a fixed blade can be carried out easily. The thread cutting device comprises a thread catcher that has a hook portion for hooking a thread and reciprocates linearly under a needle plate to hook and catch the thread on the hook portion in the periphery of an inner hook 21 of a horizontal hook and a fixed blade that cuts the thread caught by the thread catcher. The horizontal hook has a hood 24, under which the thread catcher can reciprocate, in a part of the upper portion of a side wall portion forming a bobbin compartment that accommodates a bobbin of the inner hook 21, and a guiding member 26 that guides the thread to the area located under the hood 24 where the thread catcher 14 reciprocates is provided on the upper surface of the hood 24.

Description

TECHNICAL FIELD

The present invention relates to a thread cutting device for a sewing machine that can cut an upper thread and a lower thread after completion of an sewing operation for forming a seam on a processed fabric, which is an item to be sewn, while allowing each of them to have a proper length to be left so as to be able to carry out the subsequent sewing operation on another processed fabric successively.

BACKGROUND ART

Conventionally, the upper thread and the lower thread that have been used in sewing are cut upon completion of an sewing operation for forming a seam on a processed fabric, which is an item to be sewn, using a sewing machine. There has been a problem of deterioration in quality of the subsequent sewing operation to be carried out on another processed fabric when the upper thread and the lower thread are drawn out excessively before being cut.
Furthermore, in order to ensure the beautiful finish of the item to be sewn or in order to efficiently carry out processing upon completion of the sewing operation, it is preferable that the upper thread and the lower thread are cut at the position closer to the needle hole of a needle plate. However, when the upper thread and the lower thread have been cut at the position excessively close to the needle hole of the needle plate, the upper thread and the lower thread cannot be entwined well with each other in the subsequent sewing operation and thereby the upper thread might come out of the eye of the needle, which has been a problem.
Hence, in order to make sure that the upper thread and the lower thread are cut, with a proper length being left, various thread cutting apparatuses have been developed that can cut threads automatically upon completion of a sewing operation. For example, Patent Document 1 discloses a thread cutting apparatus in which after catching a thread with a first thread catcher, a second thread catcher catches a thread extending between a thread catching portion of the first thread catcher and a needle hole of a needle plate and then guides it to a fixed blade. According to Patent Document 1, a thread can be cut at the position closer to the needle hole of the needle plate and the thread to be left on the sewing machine after being cut can be kept longer since the thread is looped back through the first thread catcher.

PRIOR ART DOCUMENTS

Patent Documents

[Patent Document 1] JP2008-259753A

SUMMARY OF THE INVENTION

Problem to be solved by the invention

In the thread cutting apparatus disclosed in Patent Document 1, however, the thread catching portion provided at the tip of the first thread catcher has often failed to catch the thread. This is caused by various states that the thread takes upon completion of a sewing operation. Therefore, there has been a problem in that every time the thread catching portion fails to catch the thread, it is necessary to carry out a thread catching operation and a thread cutting operation again, which is troublesome.
Furthermore, the fixed blade is provided with the blade thereof standing below the needle plate in a substantially vertical direction. Therefore, when some failures such as a damage of a part of the blade or wear progression occur, it is necessary to disassemble components surrounding it to replace the fixed blade and thus the maintenance thereof is cumbersome, which has been a problem.
The present invention was made with such situations in mind. The present invention is intended to provide a thread cutting device for a sewing machine that reliably hooks and catches a thread and guides it to a fixed blade. Furthermore, the present invention also is intended to provide a thread cutting device for a sewing machine whose maintenance such as a replacement of a fixed blade can be carried out easily.

Means for solving problem

In order to achieve the above-mentioned object, a thread cutting device for a sewing machine according to a first invention which cuts at least one of an upper thread and a lower thread extended between a horizontal hook and a needle hole of a needle plate comprises a thread catcher that has a hook portion for hooking a thread and reciprocates linearly under the needle plate to hook and catch the thread on the hook portion in a periphery of an inner hook of the horizontal hook, and a fixed blade that cuts the thread caught by the thread catcher, wherein the horizontal hook has a hood, under which the thread catcher can reciprocate, in a part of the upper portion of a side wall portion forming a bobbin compartment that accommodates a bobbin of the inner hook, and a guiding member that guides the thread to the area located under the hood where the thread catcher reciprocates is provided on the upper surface of the hood.
A thread cutting device for a sewing machine according to a second invention is characterized in that in the first invention, the guiding member is formed of one or more projections and guides the lower thread, which is drawn out from the upper portion of the inner hook, downward of the hood by reciprocation of the thread catcher.
A thread cutting device for a sewing machine according to a third invention is characterized in that in the second invention, the inner hook has a projecting member biased upwards by an elastic member under the hood and the projecting member is pushed down when the thread catcher moves downward of the hood.
A thread cutting device for a sewing machine according to a fourth invention is characterized in that in any one of the first to third inventions, the thread catcher is composed of two plate-like members, and linear reciprocation thereof changes its position relative to the fixed blade provided between the two plate-like members.
A thread cutting device for a sewing machine according to a fifth invention is characterized in that in the fourth invention, the fixed blade is provided between the two plate-like members in a direction crossing the thread hooked by the hook portion of the thread catcher.
A thread cutting device for a sewing machine according to a sixth invention is characterized in that in any one of the first to fifth inventions, the fixed blade is provided slidably in a direction crossing a direction in which the thread catcher reciprocates.
In the first invention, the thread catcher reciprocates linearly under the needle plate, for example, in the direction substantially parallel to the needle plate and thereby hooks and catches the thread on the hook portion in the periphery of the inner hook of the horizontal hook. The thread hooked on the hook portion by reciprocation of the thread catcher is guided to the fixed blade in the state of being caught by the thread catcher to be cut. The horizontal hook has a hood, under which the thread catcher can reciprocate, in a part of the upper portion of the side wall portion forming the bobbin compartment that accommodates a bobbin of the inner hook. A guiding member that guides the thread to the area located under the hood where the thread catcher reciprocates is provided on the upper surface of the hood. Accordingly, the thread guided downward of the hood can be hooked reliably by the hook portion of the thread catcher. This allows the thread to be guided to the fixed blade, with the thread being caught by the thread catcher.
In the second invention, the guiding member is formed of one or more projections and guides the lower thread, which is drawn out from the upper portion of the inner hook, downward of the hood by reciprocation of the thread catcher. This allows the thread to be guided reliably downward of the hood, under which the thread catcher can reciprocate. Accordingly, the thread can be hooked reliably by the hook portion of the thread catcher, which makes it possible for the thread to be guided to the fixed blade, with the thread being caught by the thread catcher.
In the third invention, the inner hook has the projecting member biased upwards by the elastic member under the hood and the projecting member is pushed down by the thread catcher when the thread catcher moves downward of the hood. Since the thread catcher reciprocates and moves downward of the hood, the lower thread is guided downward of the hood from between the projection provided on the upper surface of the hood and the projecting member that has been pushed down and then to the lower part of the thread catcher. Accordingly, the lower thread enters the hook portion of the thread catcher and thus the lower thread that has entered the hook portion of the thread catcher can be hooked reliably by the hook portion of the thread catcher.
In the fourth invention, the thread catcher is composed of two plate-like members, and linear reciprocation thereof changes its position relative to the fixed blade provided between the two plate-like members. Accordingly, the thread hooked and caught by the hook portion of the thread catcher is hooked so as to cross over the two plate-like members, and the fixed blade is provided between the two plate-like members. This allows the thread hooked by the hook portion to be cut reliably by the fixed blade.
In the fifth invention, the fixed blade is provided between the two plate-like members in the direction crossing the thread hooked by the hook portion of the thread catcher. This makes it possible for the thread hooked and caught by the hook portion by reciprocation of the thread catcher to be guided to the fixed blade to be cut reliably.
In the sixth invention, the fixed blade can slide in the direction crossing the direction in which the thread catcher reciprocates, for example, in the direction substantially orthogonal to the direction of reciprocation. Therefore, in the case where a part of the fixed blade is damaged, the fixed blade can be used for cutting the thread successively without being replaced by sliding it in such a manner that an undamaged part can be used. Accordingly, the frequency of maintenance can be reduced. Furthermore, the fixed blade can be replaced easily.

Effects of the invention

According to the present invention, the horizontal hook has a hood, under which the thread catcher can reciprocate, in a part of the upper portion of the side wall portion forming the bobbin compartment that accommodates a bobbin of the inner hook, and the guiding member that guides the thread to the area located under the hood where the thread catcher reciprocates is provided on the upper surface of the hood. Therefore, the thread guided downward of the hood can be hooked reliably by the hook portion of the thread catcher. This allows the thread to be guided to the fixed blade, with the thread being caught by the thread catcher.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the configuration of a thread cutting device for a sewing machine according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view at the sideways plane of the thread cutting device for the sewing machine according to the embodiment of the present invention.
FIG. 3 is a perspective view showing the configuration of an inner hook of a horizontal hook of the sewing machine according to the embodiment of the present invention.
FIG. 4 is a control block diagram for the thread cutting device for the sewing machine according to the embodiment of the present invention.
FIG. 5 shows plan views illustrating rotational states of a rotating hook.
FIG. 6 is a plan view showing the state of a thread catcher of the sewing machine according to the embodiment of the present invention at the time when a needle has reached the lowest point.
FIG. 7 is a cross-sectional view, at the sideways plane, showing the state of the needle and the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the needle has reached the lowest point.
FIG. 8 is a plan view showing the state of the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the needle has ascended from the lowest point to a predetermined height.
FIG. 9 is a cross-sectional view, at the sideways plane, showing the state of the needle and the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the needle has ascended from the lowest point to the predetermined height.
FIG. 10 is a plan view showing a rotational state of the rotating hook of the sewing machine according to the embodiment of the present invention at the time when the needle has ascended from the lowest point to the predetermined height.
FIG. 11 is a plan view showing the state of the thread catcher of the sewing machine according to the embodiment of the present invention at the time when a point of the rotating hook hooks an upper thread (the state shown in FIG. 5D).
FIG. 12 is a cross-sectional view, at the sideways plane, showing the state of the needle and the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the point of the rotating hook hooks the upper thread (the state shown in FIG. 5D).
FIG. 13 is a plan view showing a rotational state of the rotating hook of the sewing machine according to the embodiment of the present invention at the time when the upper thread comes off the rotating hook.
FIG. 14 is a plan view showing the state of the thread catcher of the sewing machine according to the embodiment of the present invention immediately prior to a thread cutting operation.
FIG. 15 is a cross-sectional view, at the sideways plane, showing the state of the needle and the thread catcher of the sewing machine according to the embodiment of the present invention immediately prior to the thread cutting operation.
FIG. 16 is a plan view showing the state of the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the thread catcher has been moved to the position most distant from the horizontal hook.
FIG. 17 is a cross-sectional view, at the sideways plane, showing the state of the needle and the thread catcher of the sewing machine according to the embodiment of the present invention at the time when the thread catcher has been moved to the position most distant from the horizontal hook.
FIG. 18 is a plan view showing a rotational state of the rotating hook of the sewing machine according to the embodiment of the present invention at the time when the thread catcher has been moved to the position most distant from the horizontal hook.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a thread cutting device for a sewing machine according to an embodiment of the present invention is described with reference to the drawings showing the embodiment. In the following description, the front-back and side-to-side directions viewed from the sewing operator who operates the sewing machine are described as a front-back direction and a sideways direction. FIG. 1 is a plan view showing the configuration of the thread cutting device for the sewing machine according to the embodiment of the present invention. FIG. 2 is a cross-sectional view at the sideways plane of the thread cutting device for the sewing machine according to the embodiment of the present invention.
As shown in FIG. 1, in the thread cutting device for the sewing machine according to this embodiment, a bobbin 11 is mounted on an inner hook 21 of a horizontal hook 10 to feed a lower thread 12. An upper thread 13 is passed through the eye of a needle and is entwined with the lower thread 12 by a vertical motion of the needle to form a seam on a processed fabric, which is an item to be sewn.
As shown in FIG. 2, the needle 2 is provided so as to be able to move vertically above a needle hole 9 of a needle plate 8. The upper thread 13 shown in FIG. 1 is passed through the eye 3 of the needle 2 and is entwined with the lower thread 12 shown in FIG. 1 by the vertical motion of the needle 2.
Furthermore, the thread catcher 14 has a tip bent portion 141 formed with the tip thereof being bent upwards and a hook portion 142 provided in the vicinity of a root portion of the tip bent portion 141. The hook portion 142 is formed as a folded portion bent towards the left-hand side. The thread catcher 14 reciprocates linearly in the sideways direction (the direction parallel or substantially parallel to the needle plate 8) under the needle plate 8. Accordingly, at least one of the upper thread 13 and the lower thread 12 that is extended between the horizontal hook 10 and the needle hole 9 of the needle plate 8 is hooked and caught by the hook portion 142 and then is guided to a fixed blade 15 arranged on the left-hand side of the horizontal hook 10 to be cut.
In this embodiment, the thread catcher 14 is formed to be split in two. That is, two plate-like members are arranged at a predetermined interval and only the tips of the tip bent portions 141 are joined with each other. It should be understood that the tip bent portions 141 may not be joined together and the thread catcher 14 may be formed with a single member.
Furthermore, the fixed blade 15 is provided between the two plate-like members of the thread catcher 14. Therefore, when the thread catcher 14 reciprocates linearly in the sideways direction, the position thereof relative to the fixed blade 15 provided between the two plate-like members changes. Since the thread is hooked by the hook portion 142 in such a manner as to cross the two plate-like members, the fixed blade 15 provided between the two plate-like members allows the thread hooked by the hook portion 142 to be cut reliably by the fixed blade 15.
In this embodiment, the fixed blade 15 is provided between the two plate-like members in the direction crossing the thread hooked by the hook portion 142 of the thread catcher 14. Therefore, it also is possible, for example, to arrange the fixed blade 15 in a substantially horizontal direction and then to screw it from above to fix it. This allows the maintenance such as a replacement of the fixed blade 15 to be carried out easily.
When the fixed blade 15 is interposed between, for example, plate-like members to be fixed, it can also slide in the direction crossing (the direction substantially orthogonal to) the direction in which the thread catcher 14 reciprocates. Therefore, in the case where a part of the fixed blade 15 is damaged, the fixed blade 15 can cut the thread successively without being replaced by sliding it in such a manner that an undamaged part can be used. Accordingly, the frequency of replacing the fixed blade 15 is reduced and thereby the frequency of maintenance can be reduced.
The horizontal hook 10 is arranged inside the tip side (the left-hand side) of a bed portion of the sewing machine, which is not shown, and in the vicinity of a stitch point to which the needle 2 is moved by a needle drive mechanism, which is not shown. The horizontal hook 10 can rotate around a hook shaft provided vertically, which is not shown. That is, the horizontal hook 10 is provided with a rotatable rotating hook 22 and an inner hook 21 that does not rotate and can be set inside the rotating hook 22.
The rotating hook 22 rotates at twice the speed, i.e. twice the rotation number, of the main spindle (not shown), which moves the needle 2 vertically, and thereby rotates two revolutions while the needle 2 makes one cycle. Furthermore, the bobbin 11 with the lower thread 12 wound thereon can be mounted replaceably and rotatably inside the inner hook 21. The upper portion of the horizontal hook 10 is being opened and the lower thread 12 to be drawn out from the bobbin 11 is fed along a predetermined path of the lower thread and is entwined with the upper thread 13 to form a seam.
FIG. 3 is a perspective view showing the configuration of the inner hook 21 of the horizontal hook 10 of the sewing machine according to the embodiment of the present invention. The horizontal hook 10 of the sewing machine according to this embodiment is different from conventional ones in being provided with a hood 24, under which the thread catcher 14 can reciprocate, in a part of the upper portion of a side wall portion forming a bobbin compartment that accommodates the bobbin 11 of the inner hook 21, and a guiding member 26 that guides the thread to the area where the thread catcher 14 under the hood 24 reciprocates, on the upper surface of the hood 24.
In other words, projections 261, 262 are provided as the guiding member 26 on the upper surface of the hood 24 of the inner hook 21, and they are formed to be higher than other parts. The lower thread 12 is hooked by the guiding member 26, namely the projection 261, and is guided downward of the hood 24. This allows the thread catcher 14 that can reciprocate under the hood 24 to reliably hook and catch the lower thread 12 guided downward of the hood 24 by the hook portion 142. Thus, the thread catcher 14 can guide the lower thread 12 to the fixed blade 15, with the lower thread 12 being caught thereby.
Furthermore, a projecting member 27 biased upwards by an elastic member 28 is provided under the hood 24 on the upper surface of the inner hook 21. In FIG. 3, the elastic member 28 is formed in the form of a plate spring but is not particularly limited as long as it has a configuration that bias upwards.
With the presence of the projecting member 27, the lower thread 12 guided downward of the hood 24 comes into contact with the projecting member 27. Therefore, the lower thread 12 is kept between the projecting member 27 and the projections 261, 262, which are the guiding member 26 provided on the upper surface of the hood 24, without departing the underneath of the hood 24, and is guided to the lower part of the thread catcher 14. When the thread catcher 14 moves downward of the hood 24, the tip bent portion 141 comes into contact therewith to push the projecting member 27 it down. However, when the tip bent portion 141 moves downward of the hood 24, the lower thread 12 guided downward of the hood 24 and then to the lower part of the thread catcher 14 and the upper thread 13 entwined with the lower thread 12 by a vertical motion of the needle 2 do not depart the underneath of the hood 24. Therefore, the hook portion 142 reliably passes by the lower thread 12 and the upper thread 13 and can hook and catch them reliably at the time when the thread catcher 14 is pulled back.
FIG. 4 is a control block diagram for the thread cutting device for the sewing machine according to the embodiment of the present invention. As shown in FIG. 4, a control section 50 comprises: a ROM 52 that stores various programs for carrying out various motion controls and processing, which will be described later, a sewing data for carrying out various types of sewing, and other various setting data; a CPU51 that runs various programs stored in the ROM 52; a RAM 53 that serves as a work area when the various programs are run; an input interface 54 and an output interface 55 that are connected to the CPU 51, the ROM 52 and the RAM 53 through a bus; and various drive circuits 56, 56, ....
The input interface 54 receives the input of signals for, for example, start, stop, a sewing pattern selection, and speed setting of the sewing machine and then transmits the signals thus received to the CPU 51. The output interface 55 transmits signals for carrying out a predetermined motion control to the drive circuits 56, 56, ... according to the command from the CPU 51.
The control section 50 drives each actuator and controls its operation in a way that the CPU 51 carries out arithmetic processing according to the signals, the input of which are received, using the RAM 53 as a work area based on the various programs stored in the ROM 52 and outputs output signals corresponding to the results of arithmetic processing to various actuators. For example, by driving an actuator that serves as a drive source for the thread catcher 14 in the direction of normal rotation or reverse rotation at a predetermined timing, the thread catcher 14 reciprocates linearly at the predetermined timing.
Preferably, for example, a stepping motor, which is not shown, is used as the drive source for the thread catcher 14. This is because when a suitable link mechanism, for example, a slider link mechanism is used, the rotary movement of the stepping motor can be converted into linear reciprocation and thereby the reciprocation of the thread catcher 14 can be controlled precisely. It should be understood that another mechanism such as a cam link also may be used.
The stepping motor, which is the drive source for the thread catcher 14, is also a drive source for moving the needle 2 vertically and operates in conjunction with, for example, a main driving motor (not shown) for rotating the rotating hook 22. With respect to the driving amounts of the main driving motor and stepping motor, the pulse number corresponding to the travel distance gained by the reciprocation is determined beforehand and then is stored in the ROM 52, which is a storing part of the control section 50. This allows the reciprocation of the thread catcher 14 to link with the vertical motion of the needle 2, i.e. the rotary movement of the rotating hook 22.
Hereinafter, the relationship between the reciprocation of the thread catcher 14 and the rotary movement of the rotating hook 22 is described in detail with reference to the drawings.
FIG. 2 shows the state of the thread catcher 14 and the needle 2 at the time when the needle 2 has descended a few millimeters from the highest point. With the location where the needle 2 has descended a few millimeters from the highest point being taken as a starting point, the rotating hook 22 rotates in conjunction with the vertical motion of the needle 2.
First, as the needle 2 descends from the starting point to the lowest point, the rotating hook 22 rotates approximately one revolution. FIG. 5 shows plan views illustrating the rotational states of the rotating hook 22. FIG. 5A shows the state of the rotating hook 22 when the needle 2 is located at the highest point, FIG. 5B shows the state of the rotating hook 22 when the needle 2 is located at the starting point, at which it is located when descending a few millimeters from the highest point, FIG. 5C shows the state of the rotating hook 22 when the needle 2 is located at the lowest point, and FIG. 5D shows the state of the rotating hook 22 at the time when the point 25 of the rotating hook 22 hooked the upper thread 13.
First, the needle 2 is allowed to ascend to the highest point so that the point 25 is located at the position shown in FIG. 5A, and then the needle 2 is allowed to descend a few millimeters from the highest point to be located at the starting point. Thus, the point 25 of the rotating hook 22 rotates to the position shown in FIG. 5B in the direction indicated with an arrow (counterclockwise when viewed from above).
Then, the needle 2 is allowed to descend to the lowest point and thereby the point 25 rotates to the position shown in FIG. 5C in the direction indicated with an arrow (counterclockwise when viewed from above). The position of the point 25 is the same as that shown in FIG. 5A, which means that it has rotated one revolution. In this case, the point 25 of the rotating hook 22 hooks the upper thread 13 when having rotated to the position shown in FIG. 5D.
While the needle 2 is stopped in the state where it is allowed to descend to the lowest point, the thread catcher 14 is moved downward of the hood 24. FIG. 6 is a plan view showing the state of the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the needle 2 has reached the lowest point. FIG. 7 is a cross-sectional view, at the sideways plane, showing the state of the needle 2 and the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the needle 2 has reached the lowest point.
The lower thread 12 is guided from the underneath of the hood 24 of the inner hook 21 to the needle hole 9 of the needle plate 8. When the thread catcher 14 moves downward of the hood 24, the tip bent portion 141 of the thread catcher 14 can meet reliably the lower thread 12 that has been guided. The lower thread 12 is guided to the lower part of the thread catcher 14.
In other words, when the tip bent portion 141 of the thread catcher 14 moves downward of the hood 24, it pushes the projecting member 27 down against the biasing force of the elastic member 28. Accordingly, the lower thread 12 is guided from between the projections 261, 262, which are the guiding member 26 provided on the upper surface of the hood 24, and the projecting member 27 that has been pushed down, downward of the hood 24 and then to the lower part of the thread catcher 14.
Subsequently, with the needle 2 being maintained at the lowest point, the thread catcher 14 is pulled back a few millimeters to the left (in the direction away from the horizontal hook 10) and then the needle 2 is allowed to ascend. The thread catcher 14 remains at the pulled-back position.
FIG. 8 is a plan view showing the state of the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the needle 2 has ascended from the lowest point to a predetermined height. FIG. 9 is a cross-sectional view, at the sideways plane, showing the state of the needle 2 and the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the needle 2 has ascended from the lowest point to the predetermined height. Furthermore, FIG. 10 is a plan view showing a rotational state of the rotating hook 22 of the sewing machine according to the embodiment of the present invention at the time when the needle 2 has ascended from the lowest point to the predetermined height.
The point 25 of the rotating hook 22 shown in FIG. 10 is located on the extended line connecting the rotation center of the rotating hook 22 and the needle 2, with the needle 2 having ascended from the lowest point to the predetermined height, that is, immediately under the needle hole 9 of the needle plate 8. Accordingly, the point 25 hooks the upper thread 13 that is in a looped state in the vicinity of the needle hole 9 of the needle plate 8, and the upper thread 13 thus hooked by the point 25 then enters the inner hook 21 in conjunction with a rotation of the rotating hook 22. The part of the upper thread 13, located on the upper side, whose one side has entered the inner hook 21 moves on the upper surface of the inner hook 21.
FIG. 11 is a plan view showing the state of the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the point 25 of the rotating hook 22 hooks the upper thread 13 (the state shown in FIG. 5D). FIG. 12 is a cross-sectional view, at the sideways plane, showing the state of the needle 2 and the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the point 25 of the rotating hook 22 hooks the upper thread 13 (the state shown in FIG. 5D).
As shown in FIG. 12, the upper thread 13 hooked by the point 25 enters the inner hook 21 in conjunction with a rotation of the rotating hook 22. On the other hand, as shown in FIGS. 10 and 11, the part of the upper thread 13 located on the upper side moves on the upper surface of the inner hook 21 in keeping with the rotation of the rotating hook 22.
When the needle 2 further ascends to a point just before the highest point, a thread take-up lever, which is not shown, that can move in the sideways direction and is provided above moves to the right from the leftmost side, and thereby the upper thread 13 is reeled out from a spool of thread. A movement of the thread take-up lever for a predetermined distance at a suitable timing allows a predetermined length of upper thread 13 to be reeled out. Accordingly, the upper thread 13 can be prevented, for example, from coming out of the eye 3 of the needle 2.
Furthermore, FIG. 13 is a plan view showing a rotational state of the rotating hook 22 of the sewing machine according to the embodiment of the present invention at the time when the upper thread 13 comes off the rotating hook 22. When the rotating hook 22 has rotated to the position shown in FIG. 13, a thread cast-off part 221 of the rotating hook 22 is aligned with a thread cast-off part 211 of the inner hook 21. Accordingly, the upper thread 13 hooked by the point 25 of the rotating hook 22 enters the inner hook 21 and comes off the rotating hook 22 at the thread cast-off part 221 (211). The upper thread 13 that has come off the rotating hook 22 is slacked by the amount (length) by which it has entered the inner hook 21. The upper thread 13 slacked through entering the inner hook 21 and coming off the rotating hook 22 is present on the thread cast-off part 221 (211) side. Therefore, the hook portion 142 of the thread catcher 14 can hook it reliably.
Subsequently, the thread catcher 14 is pulled back, with the rotating hook 22 being stopped. Accordingly, the slacked upper thread 13 present on the thread cast-off part 221 (211) side is hooked by the hook portion 142 and is then guided to the position just before the fixed blade 15. At this point, the upper thread 13 that has come off the rotating hook 22 is guided to the position just before the fixed blade 15, with its state being slacked by the amount by which it has entered the inner hook 21. At the same time, the lower thread 12 also is hooked by the projection 262 which is the guiding member 26 provided on the upper surface of the hood 24 of the inner hook 21 to be guided to the position just before the fixed blade 15, with the amount of the lower thread 12 to be left being ensured.
When the thread take-up lever, which is not shown, provided above is moved to the right in this state, the upper thread 13 is reeled out from the spool of thread only, but does not come out of the eye 3 of the needle 2 even when the thread is cut off. Therefore, the subsequent sewing operation can be carried out successively.
FIG. 14 is a plan view showing the state of the thread catcher 14 of the sewing machine according to the embodiment of the present invention immediately prior to a thread cutting operation. FIG. 15 is a cross-sectional view, at the sideways plane, showing the state of the needle 2 and the thread catcher 14 of the sewing machine according to the embodiment of the present invention immediately prior to the thread cutting operation.
As is understood from the comparisons between FIG. 11 and FIG. 14 as well as between FIG. 12 and FIG. 15, the upper thread 13 hooked by the hook portion 142 of the thread catcher 14 moves to a position just before the fixed blade 15, with the hook portion 142 hooking the upper thread 13 and the lower thread 12. In this state, the thread take-up lever, which is not shown, provided above is moved to the rightmost side so that the upper thread 13 hooked by the hook portion 142 is prevented from coming out of the eye 3 of the needle 2. Accordingly, a predetermined amount of upper thread 13 can be reeled out from the spool of thread.
Subsequently, the thread catcher 14 is moved to the leftmost position, i.e. the position most distant from the horizontal hook 10, and thereby the upper thread 13 and the lower thread 12 that are hooked and caught by the hook portion 142 to be guided are then cut by the fixed blade 15. FIG. 16 is a plan view showing the state of the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the thread catcher 14 has been moved to the position most distant from the horizontal hook 10. FIG. 17 is a cross-sectional view, at the sideways plane, showing the state of the needle 2 and the thread catcher 14 of the sewing machine according to the embodiment of the present invention at the time when the thread catcher 14 has been moved to the position most distant from the horizontal hook 10. Furthermore, FIG. 18 is a plan view showing a rotational state of the rotating hook 22 of the sewing machine according to the embodiment of the present invention at the time when the thread catcher 14 has been moved to the position most distant from the horizontal hook 10.
As shown in FIGS. 16 to 18, the thread catcher 14 moves to the position where the hook portion 142 passes by the fixed blade 15, with the upper thread 13 and the lower thread 12 being hooked and caught by the hook portion 142. This allows the upper thread 13 and the lower thread 12 thus guided to be cut by the fixed blade 15. With respect to the amount of the upper thread 13 to be left, a predetermined amount is ensured when the thread take-up lever, which is not shown, provided above moves to the rightmost side. Therefore, the upper thread 13 does not come out of the eye 3 of the needle 2. Accordingly, it is possible to carry out the subsequent sewing operation successively by cutting the upper thread 13 and the lower thread 12, with a proper length thereof being left, so that the subsequent sewing operation can be carried out on another processed fabric successively without any additional operations.
As described above, according to this embodiment, the horizontal hook 10 has the hood 24, under which the thread catcher 14 can reciprocate, in a part of the upper portion of the side wall portion forming the bobbin compartment that accommodates the bobbin 11 of the inner hook 21, and the guiding member 26 that guides the thread downward of the hood 24 is provided on the upper surface of the hood 24. Therefore, the hook portion 142 of the thread catcher 14 can reliably hook the thread guided downward of the hood 24 and the thread can be guided to the fixed blade 15 in the state of being caught by the thread catcher 14. Furthermore, even when a part of the fixed blade 15 is damaged, the fixed blade 15 is allowed to slide and thereby can cut the thread successively using an undamaged part without being replaced. Accordingly, the frequency of maintenance can be reduced.
The use of the thread cutting device for the sewing machine according to this embodiment is not limited to cutting both the upper thread 13 and the lower thread 12. Even in the case where, for example, either one of them has run out in operation, it also is possible to cut only the upper thread 13 or only the lower thread 12.
In addition to the above, the present invention may be embodied in other forms obtained by variously modifying the above-mentioned embodiment without departing from the spirit thereof.

2 Needle
3 Eye
8 Needle Plate
9 Needle Hole
10 Horizontal Hook
11 Bobbin
14 Thread Catcher
15 Fixed Blade
21 Inner Hook
22 Rotating Hook
24 Hood
26 Guiding Member
27 Projecting Member
28 Elastic Member
141 Tip Bent Portion
142 Hook Portion
261, 262 Projections

Claims

A thread cutting device for a sewing machine, which cuts at least one of an upper thread and a lower thread extended between a horizontal hook and a needle hole of a needle plate, comprising:
a thread catcher that has a hook portion for hooking a thread and reciprocates linearly under the needle plate to hook and catch the thread on the hook portion in a periphery of an inner hook of the horizontal hook; and

a fixed blade that cuts the thread caught by the thread catcher, wherein

the horizontal hook has a hood, under which the thread catcher can reciprocate, in a part of the upper portion of a side wall portion forming a bobbin compartment that accommodates a bobbin of the inner hook, and a guiding member that guides the thread to the area located under the hood where the thread catcher reciprocates is provided on the upper surface of the hood.
The thread cutting device for a sewing machine according to claim 1, wherein the guiding member is formed of one or more projections and guides the lower thread, which is drawn out from the upper portion of the inner hook, downward of the hood by reciprocation of the thread catcher.
The thread cutting device for a sewing machine according to claim 2, wherein the inner hook has a projecting member biased upwards by an elastic member under the hood and the projecting member is pushed down when the thread catcher moves downward of the hood.
The thread cutting device for a sewing machine according to any one of claims 1 to 3, wherein the thread catcher is composed of two plate-like members, and linear reciprocation thereof changes its position relative to the fixed blade provided between the two plate-like members.
The thread cutting device for a sewing machine according to claim 4, wherein the fixed blade is provided between the two plate-like members in a direction crossing the thread hooked by the hook portion of the thread catcher.
The thread cutting device for a sewing machine according to any one of claims 1 to 5, wherein the fixed blade is provided slidably in a direction crossing a direction in which the thread catcher reciprocates.