JPH01320086A - Thread tension guide for sewing machine - Google Patents

Abstract

PURPOSE:To eliminate the excess needle thread feed action largely exceeding the needle thread absorption quantity by adjusting the tension state of the needle thread fed from a pretensioner to a needle thread holder to increase or decrease the needle thread tension depending on the magnitude of the needle thread absorption quantity during the repeating period of the vertical movement of a needle. CONSTITUTION:When a shuttle hooks a needle thread 2 and it is rotated around the shuttle, the upper shaft rotation angle is synchronized with the 330 deg. position, the sway position of a needle thread adjusting arm 28 is moved to the lowermost section, the tension angle theta that the needle thread is put in contact with the contact section 28a of the needle thread adjusting arm 28 becomes maximum, the tension on the passing side is largely increased with respect to the tension on the proceeding side, the feed of the needle thread to a needle thread holder 10 is suppressed. When a thread take-up lever reaches the top dead point, the horizontal displacement 21 of a feed dog becomes nearly the minimum value, the needle thread adjusting arm 28 is moved to the uppermost section, thus the tension angle theta in contact with the contact section 28a becomes minimum, the feed tension of the needle thread 2 moved via a needle thread guide 31 is decreased, satisfactory seams can be obtained by sure cloth tightening.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an upper thread adjuster that appropriately changes and adjusts the tension of an upper thread in a needle feed sewing machine.

[Prior Art] FIG. 3 is a perspective view showing the configuration of the needle thread adjustment, device and surrounding parts in a conventional needle feed sewing machine.
(1) is the arm, (2) is the upper thread, and (3).

(4) and (5) respectively guide the upper thread (2), and (6) supply the upper thread (2) to a shuttle (not shown) or pull up the supplied upper thread (2). (8) is the needle that carries the needle thread (2) to the underside of the fabric (7); (9) is the needle that carries the needle thread (2) to the underside of the fabric (7); A pretensioner that adjusts the length, (10) a needle thread holder that applies the tension necessary for stitch formation and adjusts the amount of needle thread payout, and (11) a thread take-up that adjusts the amount of needle thread fed. The spring (12) is a support plate that supports the thread take-up spring (11), and (13) is the pretensioner (9) and the upper thread holder (10).
) and the support plate (12).
) is fixed. The above pretensioner (9), upper thread holder (lO), and support plate (12) are collectively referred to as an upper thread adjuster.

(14) is the needle bar that fixes the needle (8), (15) is the needle bar (
(14) is the needle bar swinging arm that swings, (16) is the upper shaft, (1
7) is a balance weight fixed to the upper shaft (16), (1
8) is a connecting rod rotatably attached to one end of the balance weight (17), and (19) is a connecting rod (18) and needle bar (1).
(20) is the needle bar swinging arm (1) that connects the
5) is the needle bar swing shaft that swings the needle bar.

Next, the operation will be explained based on the above configuration with reference to FIGS. 4 and 5.

The rotational movement of the upper shaft (16) is the balance weight (17),
The needle (
7) and bring the upper thread (2) to the underside of the fabric (A).

When the needle (8) passes the lowest point, a hook (not shown) moves the upper thread (2)
) and rotate around the outer circumference of the pot.

Figure 4 shows the balance (6) at each angular position of the upper shaft rotation angle.
Needle thread supply ffi (24), needle thread absorption ffi (25>) by the needle (8) and the above hook, needle thread supply ffi (
24) and needle thread absorption Q(25), that is, needle thread slack ffi <28). As is clear from the figure, the needle thread absorption ffi (25) reaches its maximum when the upper shaft rotation angle is around 330', and the needle thread slack ffi (
28) becomes a minimum at approximately this angular position. Fig. 5 is a diagram showing the vertical displacement of the needle bar (2I), horizontal displacement of the feed dog (23), and displacement of the thread take-up (22) at the angular position of the upper shaft rotation angle, and the horizontal horizontal displacement of the feed south (23) in the figure. It is recognized that the maximum value of is at a position approximately equal to the angular position of the maximum value of needle thread absorption Q (25) in FIG.

The needle thread absorption ffi (25) increases from the position where the above-mentioned needle thread (2) begins to rotate around the outer circumference of the hook, and the cloth tightening is performed near the top dead center of the balance (the position of the upper shaft rotation angle of 60° in Fig. 4). conduct,
The sewing operation is performed by repeating the operation of lowering the needle (7) again.

[Problems to be Solved by the Invention] In the conventional needle thread adjuster as described above, the amount of needle thread slack is determined at the angular position (of the upper shaft rotation angle) where the needle thread absorption ffi (25) by the hook is maximum. This is almost the minimum value, so if the sewing machine is operated at a high speed, the thread will be affected by loose threads, inertia, etc., and the needle thread will be excessively let out from the needle thread holder at the above angle position, resulting in insufficient fabric tightening. There have been problems such as problems such as smearing or not being able to obtain good seams.

This invention was made to solve the above-mentioned problems, and it is possible to stably feed the upper thread even when the sewing machine is operating at high speed, even near the maximum position of upper thread absorption. The purpose is to obtain an upper thread regulator.

[Means for Solving the Problems] The needle thread 13m device of the sewing machine according to the present invention feeds the needle thread from the pretensioner to the needle thread holder when a large amount of needle thread is absorbed during the repeating cycle of vertical movement of the needle. The tension state of the needle thread is adjusted to increase the needle thread tension, and conversely, when the amount of needle thread absorption is small, the needle thread tension is decreased from the above state.

[Function] In this invention, the needle thread tension to the needle thread holder is increased at a position where a large amount of needle thread is absorbed, so even if the sewing machine is operated at high speed, the needle thread can be fed at high speed. Excessive needle thread feeding operation that greatly exceeds the needle thread absorption amount, which is caused by the inertia of the needle thread, etc., as in the past, is eliminated.

[Embodiment] FIG. 1 is a perspective view showing the structure of an upper thread adjuster and its surroundings according to an embodiment of the present invention.
) to (20) are the same or corresponding parts to those with the same reference numerals in FIG. 3 showing the conventional example, and therefore, redundant explanation of the structure will be omitted.

(27) is an arm fixed to the needle bar swing shaft (20), and the needle thread (2) is stretched over the tip of the arm, and the needle thread has a contact part (28a) with a contact surface formed in an arc shape. The adjusting arm (28) is fixed, and the tip of the upper thread adjusting arm (28) is attached to the mounting plate (13).
) and swings up and down according to the movement of the needle bar swing shaft (20), so that the swing position moves to the lowest position when the upper shaft rotation angle is 330'. It has become.

(30) and (31) are a pair of needle thread guides arranged on the left and right sides of the hole (29) and fixed to the mounting plate (13).

As shown in FIG. 2, the upper thread (2) from the pretensioner (9) passes through the inner outer periphery of the upper thread guide (30) and reaches the circular cross-sectional contact portion (28a) surface of the weft thread adjustment arm (28). the needle thread holder (
10).

In the needle thread adjuster according to the present invention as described above, when the hook (not shown) hooks the needle thread (2) and rotates around the outer circumference of the hook, the upper shaft rotation angle changes as shown in FIG. is 330°
The needle thread absorption amount (25) becomes maximum near the vicinity, and the needle thread slack m
(2B) is almost at its minimum, so as the sewing machine operates at higher speeds, there is a tendency for the upper thread (2) to be fed excessively due to fraying of the upper thread (2), and to be let out from the upper thread holder (10). However, since the swinging position of the upper thread adjusting arm (28) moves to the lowest position in synchronization with the upper shaft rotation angle position of 330°, the upper thread (28) moves to the lowest position as shown in FIG. 2(a). ) is in contact with the contact portion (28a) of the upper thread adjusting arm (28), and the tension angle θ-θ1 is the maximum.

Here, the tension of the needle thread (2) between the contact portion (28a) and the needle thread guide (30) is T, and the tension of the needle thread (2) between the contact portion (28a) and the needle thread guide (30) is
Assuming the tension T2 between the Due to the fluctuation in the value of , the tension value of the tension T2 on the passing side increases significantly compared to the tension T1 on the advancing side. The tension T2 (needle thread holding force) on the passing side of the needle thread (2) fed through the needle thread guide (31) reaches the maximum at the position corresponding to the needle thread holder ( Since the feeding to 10) is suppressed, excessive feeding of the needle thread (2) caused by fraying of the needle thread (2), inertial force, etc. is prevented even when the operation shifts to high speed.

Next, when the balance reaches top dead center (upper shaft rotation angle 60°),
The feed dog horizontal displacement (21) (horizontal feed amount) shown in FIG.
) moves to the top, so the tension angle θ-θ2 in contact with the contact part (28) becomes the minimum, as shown in FIG. 2(b).
Since the tension of the upper thread (2) moving through the upper thread guide (31) is reduced, it is fed to the upper thread holder (lO). By being able to adjust the feeding tension of the thread (2) to be strong at positions where the amount of needle thread absorption is large and weak at positions where the amount of needle thread absorption is small, sewing can be performed to obtain good stitches with reliable fabric cotton. It will be done.

[Effects of the Invention] As explained above, according to the present invention, the feeding tension of the needle thread is maximized at the position where the needle thread absorption is maximum, and the holding force of the needle thread is increased. Also in the sewing operation, there is an effect that the needle thread can be stably fed without excessive thread being paid out from the needle thread holder.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of the upper thread adjuster according to the present invention and its peripheral parts, FIG. 2 is a schematic view of the main parts showing the vicinity of the upper thread adjusting arm in FIG. 1, and FIG. 3 is a conventional A perspective view showing an example of the configuration of the needle thread adjuster and its peripheral parts. Fig. 4 is a diagram showing the relationship between the needle thread supply amount, needle thread absorption amount, etc. and the upper shaft rotation angle. Fig. 5 is a diagram showing the relationship between the upper and lower needle bar rotation angles. FIG. 3 is a perspective view showing the relationship between displacement, feed dog horizontal displacement, balance displacement, and upper shaft rotation angle. In the figure, (2) is the upper thread, (8) is the needle, (9) is the pretensioner, (10) is the upper thread holder, (20) is the needle bar swing arm, and (28) is the upper thread adjustment arm. . Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] Consisting of a needle that reciprocates up and down the fabric with the upper thread sent from the thread take-up, a pretensioner that feeds the upper thread in accordance with the reciprocating movement of the needle, an upper thread holder, etc. In a sewing machine equipped with an upper thread adjuster, the upper thread to be fed from the pretensioner to the upper thread holder is tensioned on a circular arc portion connected to and displaced by a needle bar swing shaft that reciprocates in synchronization with the needle. An upper thread adjuster for a sewing machine, characterized in that an upper thread adjusting arm is provided for suppressing the feeding of the upper thread when the amount of the upper thread absorbed is maximum.