JPH03218794A - Needle thread vibration preventing mechanism - Google Patents

Abstract

PURPOSE:To prevent a needle thread from being vibrated when a rotary hook catches the loop of the needle thread, to form stitches with proper twist return and to use a sewing machine for a long period by crimping the needle thread by a crimping means when catching the needle thread loop by the rotary hook at least for each stitch and releasing the needle thread when supplying and tightening the needle thread. CONSTITUTION:A needle thread 1 is passed through a through-hole 11c on an outside plate 11b of a crimper 11 and perpendicularly hung down between the outside plate 11b and an inside plate 11a of an elastic material. In the state of positioning a sewing needle at an upper dead point, crossing needle and bobbin threads by the rotary hook and tightening up the needle thread by a balance, a ball object 8 is housed in a fixed shaft 6 by an outer pipe 7. When the needle thread forms the loop in the lower direction of an object to be sewn and the rotary hood catches this loop, the ball object 8 protrudes from an engaging hole 7a of the outer pipe 7 by the energization of a spring 9 and the inside plate 11a is pushed toward the outside plate 11b. Then the needle thread 1 is pushed so as to crimped between the inside and outside plates 11a and 11b of the crimper 11. The needle thread is pressed in such a way while the outer pipe 7 is moved for a length L of the longitudinal opening of the engaging hole 7a.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is designed to prevent the rotary hook from swinging when the needle thread forming a loop below the workpiece is captured by vertical movement of the thread take-up, etc. This invention relates to a mechanism for preventing upper thread swinging.

[Prior art] The needle thread, which forms a loop below the workpiece due to the vertical movement of the thread take-up, is hooked onto the tip of the rotary hook, passes through the rotary hook, intersects with the bobbin thread, and forms a stitch. Although it is a thing,
When this upper thread swings above the workpiece due to the up and down movement of the sewing needle, the loop formed below the workpiece also swings accordingly, preventing it from catching the tip of the rotary hook and forming a stitch. This will cause inconvenience.

In order to eliminate this inconvenience, a swing prevention mechanism has been proposed that holds down the needle thread between the thread take-up and the sewing needle and prevents the needle thread from swinging.

FIG. 3 is a diagram showing such a conventional rocking prevention mechanism. In the anti-swing mechanism shown in FIG. 2(a), 2a is a first plate fixed to the sewing machine body between the thread take-up lever and the sewing needle, and 2b is a second plate provided facing the first plate 2a. It is a plate. 3 passes through the second plate body 2b and connects the first plate body 2
It is a screw body whose tip is screwed into a. 4 engages one end with the screw body 3 and the other end with the second plate body 2.
b, and the second plate 2b is brought into contact with the first plate 2a.
It is biased against. If the upper thread 1 is passed between the plates 2a and 2b of the rocking prevention mechanism having the above structure as shown in the figure, the rocking prevention mechanism will press down the upper thread 1 by the bias of the spring 4, so the upper thread will be threaded. 1 can be prevented from swinging.

Further, the presser foot pressure applied to the upper thread 1 can be adjusted by moving the threaded body 3 back and forth. On the other hand, the anti-swing mechanism 5 shown in FIG. 5(b) is made of a U-shaped rubber material, etc., and is fixed to the sewing machine body between the thread take-up lever and the sewing needle, and is designed to pinch the upper thread 1 as shown in the figure. It is possible to prevent the upper thread 1 from swinging by pressing it.

[Problems to be solved by the invention] However, the conventional technology has the following problems. The anti-swing mechanisms shown in Figures 3 (a) and (b) hold down the needle thread both when supplying the needle thread by vertical movement of the thread take-up and when tightening the thread. As a result, the needle thread that forms a loop below the workpiece is unstuck, resulting in the inconvenience that the tip of the rotary hook cannot properly capture the needle thread.

In particular, in a two-needle sewing machine, when the needle thread is fed in conjunction with the cloth feeding action, this phenomenon is noticeable because the needle hole of the needle is pressed against the thread on the left side.

In other words, when the warp of the needle thread returns, a large number of fiber threads are exposed on the needle thread, and the tip of the rotary hook captures only a portion of these fiber threads to form a seam. This may cause inconveniences such as half-stitching or part of the fiber thread being cut by the rotary hook.

Furthermore, since each of these anti-swing mechanisms is constantly rubbed against the upper thread, the upper thread is subject to significant wear and has to be replaced frequently, reducing work efficiency.

[Means for Solving the Problems] Therefore, the present invention provides a clamping means that includes a clamping section disposed between the thread take-up and the sewing needle, and a drive section that clamps or releases the upper thread by the clamping section. For each stitch, at least when the needle thread loop is captured by the rotary shuttle, the needle thread is held by the clamping means, and the needle thread is threaded. When the rotary hook captures the loop of upper thread that is being held, the engagement hole provided in the outer sleeve of the needle bar is in a position corresponding to the protruding body, and the protruding body is pulled out from this engagement hole by the biasing body. By protruding and being pressed by the protruding body, the clamping body clamps the needle thread so as to prevent the needle thread from swinging, thereby ensuring proper capture of the needle thread by the rotary hook.

[Embodiments of the invention] Examples of the invention will be described based on the drawings. Figures 1 and 2 are diagrams showing an embodiment of the present invention. FIG. 1 is a partially cutaway side view showing the needle thread swing prevention mechanism. In the figure, reference numeral 6 denotes a fixed shaft within the needle bar, which is fixed to the sewing machine head M.

Reference numeral 7 denotes an outer tube of the needle bar, which has a fixed shaft 6 therein, and has a sewing needle at its lower end, which moves up and down in conjunction with the upper shaft of the sewing machine.

Ma is a metal ring fixed to the sewing machine head M to stabilize the vertical movement of the outer tube shaft 7. Reference numeral 8 denotes a ball body as a protruding body, which is installed inside a hole 10 provided on the side surface of the fixed shaft 6, and is biased outward by a spring 9 as a biasing body.

On the other hand, 7a is an engagement hole provided in the outer tube 7, and this engagement hole 7a allows the needle thread loop to be inserted in a series of sewing operations.
When the rotary hook captures the ball body 8, it is provided at a position that is at the same height as the ball body 8.

(The outer tube is shown in the rising state in the figure.) The opening length of the engagement hole 7a in the vertical direction is longer than the outer diameter of the ball body 8.

Reference numeral 11 denotes a clamping body, which is composed of two plates whose upper ends are each fixed to a metal ring Ma so as to face the ball body 8.

FIG. 1(b) is an external perspective view showing this holding body 11, and in the figure, lla is an inner plate made of an elastic material, and lla is an inner plate.
lb is an outer plate having a through hole 11c in the upper part.

The needle thread 1 may be passed through the through hole 11c of the outer plate 1lb and suspended between the outer plate 1lb and the inner plate 11a, as shown in the figure.

Next, the function of this needle thread swing prevention mechanism will be explained with reference to Fig. 2. Figure (a) shows a state in which the outer tube 7 is at the top dead center, that is, the sewing needle is at the top dead center, the rotary shuttle crosses the upper thread and the lower thread, and the thread take-up is tightening the upper thread. In this state, the ball body 8 is stored within the fixed shaft 6 by the outer tube 7.

Furthermore, the clamping body 11 cannot prevent the needle thread 1 from moving. In the same figure (b), the needle thread forms a loop below the material to be sewn,
This is a diagram illustrating a needle thread swing prevention mechanism when the rotary hook captures the needle thread. In this state, the ball body 8 protrudes from the engagement hole 7a of the outer tube 7 by the urging force of the spring 9.

Then, the ball body 8 pushes the inner plate 11a of the clamping body 11 toward the outer plate 1lb, and the needle thread 1 is held so as to be sandwiched between the inner plate 11a and the outer plate 1lb of the clamping body 11.

The holding of the upper thread 1 by the clamping body 11 is carried out while the outer tube shaft 7 moves by the length L of the vertical opening of the engagement hole 7a, and this occurs when the rotary hook captures a loop of the upper thread and before and after the upper and lower threads. It is designed to hold 1.

This prevents the upper thread 1 from swinging due to the vertical movement of the sewing needle, etc., and prevents the upper thread 1 from being pressed all the time.
Since there is no need to handle the needle thread 1 up and down, inconveniences such as unwarping of the needle thread 1 can be prevented, and the rotary shuttle can properly capture the loop of the needle thread formed below the workpiece.

The clamping body 11, which comes into sliding contact with the upper thread intermittently, can be used for a long period of time. Next, another embodiment of the needle thread swing prevention mechanism will be described.

The needle thread swing prevention mechanism according to the present invention includes an angle detector consisting of a synchronizer or the like that detects the rotation angle of the upper shaft of the sewing machine, and a mechanism that operates based on a signal from the angle detector to detect the rotation angle between the thread take-up and the sewing needle. It consists of a clamping means that clamps the upper thread and is driven by the forward and backward movement of a solenoid or the amplitude motion of a piezoelectric element.

In other words, this upper thread swing prevention mechanism uses an angle detector to output a signal between the front and back of the angle of the upper shaft when the rotary hook captures a loop of the upper thread, and prevents the upper thread from swinging using the clamping means. do. According to this upper thread swing prevention mechanism, it is possible to freely set the timing for pressing the upper thread and the holding time, thereby making it possible to more appropriately capture the upper thread loop in the rotary hook. [Effects of the Invention] As explained above, the needle thread swing prevention mechanism according to the present invention prevents the needle thread from swinging when the rotary hook captures the loop of the needle thread. The untwisting allows proper seam formation and improves sewing quality.

Further, the needle thread swinging mechanism that makes sliding contact with the needle thread intermittently enables long-term use and can also improve work efficiency.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the upper thread swing prevention mechanism according to the present invention, and FIG. b) is an external perspective view showing the configuration of the clamping body, FIG. 2 is a diagram showing the action of the upper thread swing prevention mechanism shown in FIG. 1, and FIG. Partially cutaway side view showing the needle thread swing prevention mechanism; FIG. The side view and FIGS. 3(a) and 3(b) are external perspective views showing a conventional rocking prevention mechanism. In the figure, 1...Needle thread 6...Fixed shaft 7...Outer tube 7a...Engaging hole 8...Protruding body 9...Biasing body 10...Hole 11... holding body

Claims (1)

[Scope of Claims] A clamping means consisting of a clamping part disposed between the thread take-up and the sewing needle, and a driving part that clamps or releases the upper thread by the clamping part; An upper thread swing prevention mechanism characterized by comprising a control means for clamping the upper thread by a clamping means when capturing a thread loop, and releasing the upper thread when supplying the upper thread and tightening the thread.