JPS6253700A - Yarn cutting mechanism of sewing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thread cutting mechanism for a sewing machine.

[Conventional technology]

A conventional thread cutting mechanism is composed of a fixed knife F and a moving knife M, and shears the thread in a manner similar to a knife.

(1) When the moving knife moves forward When the moving knife M rotates clockwise in Fig. 4(a), the separating section M1 prevents the threads to be sheared (the bobbin thread and the upper thread UT of the fabric section) from being sheared. The yarn (needle thread UN on the needle side) is separated, and the unsheared yarn is moved clockwise while being hooked on the hook M2, while the loosened yarn to be sheared is moved clockwise. While the scalpel M is rotating, it is strongly pressed outward by the circular arc portion M3 of the moving scalpel M and is bent into a "〈" shape, and then the outward pressure is removed at the end of the circular arc portion M3. Then, due to the tension of this thread, this thread becomes
It suddenly moves to the blade part M4 (see FIG. 4(b)).

(2) When the moving knife moves back When the moving knife M rotates counterclockwise in FIG. 4(b), the thread to be sheared is moved in the direction of the fixed knife F while being held by the blade M4 It is sheared by a fixed scalpel F and a moving knife M.

[Problem that the invention seeks to solve]

However, the needle thread UT on the 4j side of the thread to be sheared, which is in contact with the circular arc portion M3 of the moving knife M, moves while remaining in contact with the circular arc portion M3 as the moving knife M rotates due to the frictional resistance of the circular arc portion M3. 2 In addition, the tension of the bobbin thread of the thread to be sheared that is in contact with the circular arc portion M3 may loosen the bobbin thread tension by the bobbin case, or depending on the type of thread, the tension may be insufficient, and this bobbin thread may be Even when the movable knife M rotates, it remains bent in the shape of "<" and sometimes does not slide on the arcuate portion M3.

Therefore, in either case, the thread to be sheared is cut by the blade M4.
There was a problem that the thread was not held properly and the thread was not cut.

[Means for solving problems]

In this invention, the thread to be sheared is held by a thread pulling mechanism during the forward movement of the moving knife, and at the maximum forward movement position of the moving knife,
Holding the blade of the moving scalpel on the movement trajectory,
This allows for reliable thread cutting.

〔Example〕

In Fig. 0, which describes the first embodiment of the present invention based on Fig. 1, l is a fixed scalpel whose base is fixed to the machine frame with screws, and a blade portion 1a is provided opposite the needle hole NH. ing. 2 is a movable scalpel whose base is rotatably supported by a screw. The outer end of the movable scalpel 2 is formed into an arc shape, and one side □ is provided with a blade portion 2a facing the blade portion 1a of the fixed knife I, and the other side is cut out to form a hook. 02b and a separating section 2c are formed.

Reference numeral 3 denotes an arm whose center part is supported by a screw, one end of which is connected to the movable scalpel 2 via an arm 4, and the other end is brought into contact with a cam (not shown) via a connecting rod 5. There is. 6
1 is a thread shifting plate, one end of which is rotatably supported by a screw, and a guide groove 6b in the shape of an "E" is formed at the base. A protrusion 6a is provided on the side of the protrusion 6a facing the thread to be sheared immediately before the thread is cut, and the tip of the protrusion 6a is cut out to hold the thread to be sheared immediately before the thread is cut. A recess is formed. Reference numeral 7 designates a stand for attaching the bottle, which is fixed to the connecting rod 5 with screws, and a pin 7a provided on the stand 7 for attaching the bottle is guided through the guide groove 6b of the thread shifting plate 6.

The connecting rod 5, the thread shifting plate 6, the bin mounting stand 7, and the bin 7
A and the like constitute a thread pulling mechanism.

Next, the effect will be explained.

(a) When the moving knife 2 rotates counterclockwise in FIG. 1(a), the cutting section 2C separates the threads to be sheared (the bobbin thread and the upper thread UT of the cloth section). The unsheared yarn (needle-side needle thread UN) is separated, and the unsheared yarn is separated by the hook part 2b.
The yarn to be sheared is moved counterclockwise while being hooked to the thread, and the thread to be sheared is positioned between the outer end of the movable scalpel 2 and the protrusion 6a of the arm 6 (see Fig. 2(b)). )reference)
.

Then, when the moving knife 2 further rotates counterclockwise, the thread to be sheared is moved onto the movement locus of the blade section 2a of the moving knife 2 while being held by the protrusion 6a (first
(See figure (c)).

(b) During the double movement of the moving knife When the moving knife 2 is rotated clockwise in FIG. , is sheared by the fixed knife 1 and the moving knife 2.

FIG. 2 is a diagram showing a second embodiment of the invention. lO
is a thread shifting plate formed in a three-shape shape, one end of which is pivotably supported, and the other end provided with a notch for holding the thread to be sheared. A cam 11 has a notch 11a on a part of its outer peripheral surface, and rotates in conjunction with the cam that drives the connecting rod 5. 12 is a cam follower that follows the cam surface, and one end is pivotally supported on the machine frame. A connecting rod 13 connects the thread shifting plate and the cam follower. The thread shifting plate 10, the cam 11, the notch lla,
The cam follower 12 and the connecting rod 13 constitute a thread pulling mechanism.

This thread shifting mechanism operates at the same timing as in the above embodiment, and the thread to be sheared is separated by the separating section 2C of the moving knife 2 between the outer end of the moving knife 2 and the notch of the thread shifting plate. When the movable knife 2 is further rotated, the thread to be sheared is moved onto the movement trajectory of the blade portion 2a of the movable knife 2 while being held in the notch. Thereafter, thread cutting is performed by cooperation between the moving knife and the fixed knife.

Further, the driving means for the thread shifting member according to the present invention can be replaced with an electromagnet, an air cylinder, etc. in addition to the means shown in the illustrated embodiment.

FIG. 3 is a diagram showing a third embodiment of the invention. 20
is a thread shifting spring serving as a thread shifting mechanism, one end of which is fixed to the movable knife 2 with a screw 21.

The other end is a circular arc portion 22 so as to protrude outward by the circular arc portion M3 of the movable scalpel 2 in the natural state, and the tip is bent into a hook shape, and the inclined portion 23 is as shown in Fig. 3 (b) in the natural state.
) protrudes inward from the blade portion M4 of the moving knife 2.

When the movable knife 2 rotates clockwise as shown in FIG. 3(a) and the threads UN and L to be cut come into contact with the arcuate portion 22, the thread tension spring 20 moves the thread When the thread UN/L to be cut is bent by the tension as shown in FIG. 3rd by elastic force
Restore as shown in figure (b).

When the movable knife 20 starts to move back and rotate counterclockwise from this state, the thread UN-L to be cut is moved by the thread pulling spring 20.
It is reliably guided into the blade part 2a of the moving scalpel along the inclined part 23 of the movable scalpel.

The above thread trimming mechanism has been explained for a lockstitch sewing machine that forms a stitch with an upper thread and a bobbin thread, but this thread trimming mechanism can also be used for thread trimming on a chain stitch sewing machine such as a single chain stitch or double chain stitch. It can also be applied to mechanisms.

〔Effect of the invention〕

Since the present invention has the above-described configuration, the thread to be sheared can be held on the movement trajectory of the blade of the moving scalpel,
Therefore, there is an effect that the yarn to be sheared can be reliably sheared.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) respectively show a first embodiment of the present invention and are diagrams for explaining the thread cutting operation, and FIG. 2 shows a second embodiment of the present invention. The figure shown in FIG. 3 is a figure showing the third embodiment, and FIG. 4(a). (b) is a diagram for explaining the conventional thread cutting operation. In the figure, 1 is a fixed knife, 2 is a moving knife, and 6 is a thread shifting plate.

Claims (1)

[Claims] The forward movement of the moving knife separates the yarn to be sheared and the yarn not to be sheared, and during the forward movement of the moving knife, the yarn to be sheared is pressed in the opposite direction to the center of rotation of the moving knife to apply tension. By removing the pressing force applied to the yarn to be sheared at the maximum forward movement position of the knife, the blade of the moving scalpel is positioned on the movement trajectory, and the movement of the yarn located on the trajectory is made to move backward. In a thread cutting mechanism that shears by cooperation of a knife and a fixed knife, the thread to be sheared is held during forward movement of the moving knife, and the blade of the moving knife is held at the maximum forward movement position of the moving knife. A thread trimming mechanism for a sewing machine, characterized in that a thread trimming mechanism is provided for holding the thread on the movement trajectory of the sewing machine.