JPH0535078U - Sewing machine thread cutting device - Google Patents

Abstract

(57) [Abstract] [Purpose] The needle thread loop is not obstructed in the hook and the amount of thread remaining at the time of thread cutting can be made constant, and the strength of the knife holder can be improved. To provide a thread cutting device of a sewing machine which can be easily adjusted. [Structure] A lower knife 19 having a lower knife 19 fixed by lower knife setscrews 20 and 21 is rotatably supported on the lower shaft metal 2, and an upper knife holder 4 is rotatable on its shaft portion 5a. Supported by. An adjusting screw hole 5bc is formed in the lower knife 19, and an adjusting screw 50 is screwed into the adjusting screw hole 5bc. In addition, the lower knife 19 has an adjusting screw 50
A through hole 19aa is formed to expose the rotation operation part of the. Loosen the lower knife setscrews 20 and 21 to remove the through hole 1
The adjusting screw 50 is rotated through 9aa to rotate the screws 20, 2
When 1 is tightened, the upward tilting angle of the lower knife is changed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thread cutting device of a sewing machine, and more particularly to a thread cutting device of a sewing machine which has an upper knife and a lower knife and moves them in an engaging direction to cut a thread.

[0002]

[Prior Art]

 Conventionally, a thread cutting device of this type of sewing machine is used to cut a thread just below a needle hole of a needle plate to shorten a thread leg connected to a work cloth. When using this thread cutting device to cut a thread, it is necessary to properly adjust the engagement state between the cutting edge of the upper knife and the cutting edge of the lower knife to adjust the cutting quality. That is, when the engagement pressure between the upper knife and the lower knife is insufficient or the engagement posture is inclined, the thread cannot be completely cut, or the thread cannot be cut at all. It becomes. On the contrary, if the upper knife and the lower knife are adjusted so as to collide with each other excessively, the knife may be damaged. Therefore, the sharpness of the knife is adjusted not only at the factory shipment stage but also at the sewing factory as the sharpness decreases.

As a means for adjusting the sharpness of the thread of this female, there is an application filed as Japanese Patent Application No. Hei 2-21702. In this technology, the upper knife is screwed to the upper knife holder with one fixing screw, and the upper knife holder has a notch that extends to the tip side of the upper knife beyond the fixing screw and opens to the holder side end. A bifurcated part is formed, a screw hole is formed in one of the bifurcated parts, and a through hole having a diameter larger than that of the screw hole is formed in the other part of the forked part. Through holes are formed, adjusting screws are screwed into the screw holes through the through holes, and the adjusting screw is tightened so that the upper knife is curved together with the other of the forked portions and is pressed against the lower knife. It is a thing. In other words, in order to increase the sharpness, it suffices to lower the upper knife relative to the lower knife by appropriately rotating the adjusting screw.

[0004]

However, in the above-mentioned conventional technique, a notch is formed in the knife holder for adjusting the sharpness of the knife to form a bifurcated part, and the bifurcated part is curved to tilt the upper knife. Therefore, in order to allow the operator to easily rotate the adjusting screw, the thickness of the upper knife and the thickness of the portion of the bifurcated portion where the through hole is formed must be reduced. Therefore, there is a problem that the strength of the upper knife attachment portion is reduced and the upper knife attachment portion is easily damaged.

On the other hand, if the thickness of that portion is increased to increase the strength, the adjusting screw must be large and have high strength, and at that time, a large force is required to rotate the adjusting screw. Therefore, there is a problem that it is difficult to perform the adjustment work that requires delicate adjustment, the knife holder itself becomes large, and it becomes difficult to downsize the thread cutting device.

Further, in the above-mentioned conventional device, since the upper knife is biased toward the lower knife, that is, toward the rotary hook, the lower knife also moves toward the rotary hook. Therefore, when forming the seam where the upper knife is not engaged with the lower knife, the distance between the upper knife and the rotary hook becomes narrower, which hinders the thread from coming out of the hook of the needle thread loop. At the time of cutting, the lower knife is urged toward the rotary hook by the upper knife and the gap between the hook and the hook becomes even narrower, and the upper thread cannot move on the thread sliding surface of the lower knife immediately before the thread is cut. There is also a problem in that the remaining amount of the upper thread that continues to the needle is not constant because the thread stops at the end and is cut.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent unthreading of a hook of a needle thread loop from being hindered and to keep a remaining thread amount during thread cutting constant. At the same time, it is an object of the present invention to provide a thread cutting device for a sewing machine, which can improve the strength of a knife holder and facilitate the work of adjusting the meshing blade pressure of the knife.

[0008]

[Means for Solving the Problems]

 To achieve this object, the thread cutting device of the sewing machine of the present invention is provided below the needle plate of the sewing machine bed, and is provided with a pair of knife holders rotatably supported about parallel axes and one knife of the knife holders. It has an upper knife that is fixed to the holder with an upper knife set screw, and a lower knife that is fixed to the other knife holder with a lower knife set screw and faces the lower surface side of the upper knife. In the thread cutting device of the machine that moves the thread in the direction of the lower direction to cut the thread, the thread is formed on the tip side of the lower knife than the screw hole of the lower knife set screw formed on the lower knife mounting surface of the other knife holder. Adjusting screw hole, an adjusting screw screwed into the adjusting screw hole so as to be retractable from the lower female mounting surface, and formed through the adjusting screw hole at a portion of the lower female member facing the adjusting screw hole. Also has a small diameter It is equipped with a door.

[0009]

[Action]

 In the present invention having the above structure, the needle plate is removed from the sewing machine bed to expose the female holder, and the lower female set screw is loosened. After that, the adjusting screw exposed in the through hole of the lower knife is pivotally operated through the through hole with a hexagon wrench or the like to finely adjust the amount of protrusion from the lower knife mounting surface of the adjusting screw. Therefore, the lower knife tilts with respect to the knife holder, and the lower knife set screw is tightened again to fix the lower knife.

[0010]

【Example】

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

A rotary hook 3 is screwed into the tip of a lower shaft 1 which is provided in the sewing machine bed 30 and is rotated by a sewing machine motor. A lower knife holder 5 is rotatably supported on a stepped front end 2a of a lower shaft metal 2 which supports the lower shaft 1, and the lower knife holder 5 has an annular groove 2b formed on the tip 2a. It is prevented from coming off by a retaining ring 6 fitted in it. The lower knife holder 5 comprises a ring-shaped shaft portion 5a, a lower knife mount 5b formed on a flange portion adjacent to the shaft portion 5a, and an arm portion 5c also formed on the flange portion.

An upper knife holder 4 is rotatably supported on a shaft portion 5a of the lower knife holder 5, and the upper knife holder 4 is composed of an upper knife mount 4a and a bifurcated arm portion 4b. On the upper knife mounting base 4a of the upper knife holder 4, an upper knife 15 having a flat plate-shaped cutting tooth portion 15a formed on the lower surface at the tip thereof is detachably fixed by upper knife setscrews 17 and 18.

On the other hand, a pair of screw holes 5bb are formed on the lower knife mounting surface 5ba of the lower knife holder 5b of the lower knife holder 5 that extends in an arc shape, and the mounting is performed between the screw holes 5bb. An adjustment screw hole 5bc is formed on the tip side of the table 5b. The adjusting screw 50 is screwed into the adjusting screw hole 5bc. By rotating the adjusting screw 50, the adjusting screw 50 can be projected and retracted upward from the lower female mounting surface 5ba.

The lower knife 19 comprises a base portion 19a fitted to the lower knife attachment surface 5ba and a thread separating portion 19b. Through holes larger than the diameter of the screw holes 5bb are formed in the base portion 19a at the portions facing the pair of screw holes 5bb, and the lower female setscrews 20 and 21 are provided through the through holes. The lower knife 19 is fixed to the lower knife holder 5 by being screwed into the 5bb. At this time, the adjusting screw 50 is housed in the adjusting screw hole 5bc.

A through hole 19aa having a diameter smaller than that of the adjusting screw hole 5bc is formed in a portion of the base portion 19a of the lower knife 19 opposed to the adjusting screw hole 5bc, and the adjusting screw is formed in the through hole 19aa. The turning operation unit of 50 is exposed. The thread cutting portion 19b of the lower knife 19 is formed with a sword tip 19ba, a thread sliding surface 19bb extending from the sword tip 19ba to the base 19a side, a hook portion 19bc extending from the sword tip 19ba to the opposite side, and a spherical projection portion. The cut tooth portion 19bd is formed and a guide portion 19be extending between the hook portion 19bc and the cut tooth portion 19bd for guiding the thread to be cut to the cut tooth portion 19bd.

Therefore, as will be described later, when the lower knife 19 is rotated forward to engage with the upper knife 15, the sword tip 19ba is caught by the hook 3 and the cloth side limb of the upper thread loop is caught. And the lower thread are separated into the hook portion 19bc, and the needle side limb of the upper thread loop is separated into the thread sliding surface 19bb. Then, when both knives are further turned in the engaging direction, the cloth side limb of the upper thread loop and the lower thread hung on the hook portion 19bc are formed on the spherical protrusion through the guide portion 19be. To the cutting tooth portion 19bd, which is cut in cooperation with the cutting tooth portion 15a of the upper female 15. Until this cutting, the needle side limb of the upper thread loop slides on the thread sliding surface 19bb, and the needle remaining thread length is secured by a predetermined amount.

Next, a configuration for reciprocally rotating the female holders 4 and 5 will be described.

That is, a forked shaft 7 is rotatably supported in the sewing machine bed 30 in parallel with the lower shaft 1, and one end of the forked shaft 7 has a thread cutting lever 8 having two arm portions. Are fixed by screws 9. The other end of the bifurcated shaft 7 is connected to a known power transmission mechanism (not shown), and the bifurcated shaft 7 is reciprocally rotated by a predetermined angle in response to a thread cutting signal.

A hole 8 a extending parallel to the forked shaft 7 is formed through one arm of the thread cutting lever 8. The hole 8 a is slid on the forked arm 4 b of the upper knife 4. A shaft portion of the roller 10 that is movably held is inserted, an annular groove 10a is formed in the shaft portion, and a retaining ring 11 is fitted in the annular groove 10a. A threaded hole 8b is formed in the other arm portion of the thread cutting lever 8, and a stepped screw 13 for rotatably supporting the connecting rod 12 at one end is screwed into the threaded hole 8b. ing. On the other hand, a screw hole 5d is formed in the arm portion 5c of the lower knife holder 5, and a stepped screw 14 for rotatably supporting the other end of the connecting rod 12 is screwed into the screw hole 5d. ing.

The upper knife holder 4 and the lower knife holder 5 are arranged at the standby position shown in FIG. 2 via the thread cutting lever 8 and the connecting rod 12 at the time of stitch formation, and at the time of thread cutting. Is rotated forward to the thread cutting position shown in FIG. 3 and then returned to the standby position.

That is, in response to the thread cutting signal, when the thread cutting lever 8 is rotated forward by a predetermined angle in the clockwise direction in FIG. 2 via the power transmission mechanism, the upper knife holder 4 is rotated via the roller 10. Is rotated counterclockwise. On the other hand, with the forward rotation of the thread cutting lever 8, the screw hole 8b thereof is also forward rotated, and the lower knife holder 5 is forwardly rotated clockwise in FIG. 2 via the connecting rod 12. Therefore, the upper knife 15 and the lower knife 19 are moved in a direction in which they engage with each other, and thread cutting is performed.

In this thread trimming device, in order to adjust the sharpness of the thread, the needle plate 31 is removed from the sewing machine bed 30, and the thread trimming lever 8 is manually rotated to attach the lower knife to the lower knife holder 5. The knife 19 is exposed in a substantially horizontal state at the needle plate mounting opening of the sewing machine bed. In this state, the lower knife set screws 20 and 21 are loosened so that the lower knife 19 can be tilted with respect to the lower knife holder 5. Then, a hexagon wrench T is fitted into the rotary operation portion of the adjusting screw 50 exposed in the through hole 19aa of the lower knife 19 and rotated, and the adjusting screw 50 is moved from the lower knife mounting surface 5ba. Finely move it in the protruding direction or in the direction in which the lower female mounting surface 5ba is retracted. After that, the lower knife set screws 20 and 21 are tightened again to fix the lower knife 19, and the engagement state with the upper knife 15 is visually confirmed. If the engagement state is not appropriate, the adjustment work described above may be repeated.

Since the lower knife 19 is tilted in the direction of the upper knife 15 as described above, the thread pulling out of the hook at the time of forming stitches is greater than that in the conventional method of tilting the upper knife 15 toward the lower knife 19. Not only is the quality kept, but the amount of thread remaining on the needle during thread cutting is constant.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

[0025]

As is clear from the above description, since the present invention is a method of moving the lower knife in the direction of urging the upper knife, the rotary hook of the upper thread loop at the time of seam formation. Not only can the amount of thread remaining on the needle be kept constant during thread cutting without disturbing thread loss from the machine, but also the needle plate can be removed and the sharpness can be adjusted visually while the sewing machine is not tilted. The strength of the knife holder can be improved compared to the conventional technology in which a notch is formed in the knife holder, and the adjustment work itself does not have to be performed by removing the lower knife from the knife holder, which is an advantage that it can be performed easily in a short time. Have.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a thread cutting device, showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a standby position of the thread cutting device.

FIG. 3 is a cross-sectional view showing a cutting position of the thread cutting device.

FIG. 4 is an explanatory diagram for explaining a fixed posture of a lower knife with respect to a lower knife holder.

[Explanation of symbols]

 1 Lower shaft 3 Rotating hook 4 Upper knife holder 5 Lower knife holder 5b Lower knife mount 5ba Lower knife mount surface 5bb Screw hole 5bc Adjustment screw hole 8 Thread trimmer lever 15 Upper knife 17 Upper knife set screw 18 Upper knife set screw 19 Bottom Female 19aa Through hole 20 Lower knife set screw 21 Lower knife set screw 30 Sewing machine bed 31 Needle plate 50 Adjustment screw

Claims (1)

[Scope of utility model registration request] 1. A pair of knife holders provided below the needle plate of the sewing machine bed and rotatably supported about parallel axes, and an upper knife fixed to one of the knife holders by an upper knife set screw. And fixed to the other knife holder with the lower knife set screw,
A thread cutting device of a sewing machine that has a lower knife facing the lower surface side of the upper knife and moves the respective knife in a direction in which the knife is engaged with each other to cut the thread, wherein a lower knife mounting surface of the other knife holder is provided. An adjustment screw hole formed on the tip side of the lower knife than the formed screw hole of the lower knife set screw, an adjustment screw screwed into the adjustment screw hole so as to be retractable from the lower knife mounting surface, and the lower screw. A thread cutting device for a sewing machine, comprising: a through hole formed in a portion of the knife facing the adjusting screw hole and having a diameter smaller than that of the adjusting screw.