JPH0452159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a needle thread supplying device for a sewing machine that uses needle thread automatic correction technology for pitch errors in a sewing machine.

[Conventional technology] Industrial sewing machines in particular perform sewing in a wide range of rotational speeds, from very low speeds to high speeds, but when sewing with a sewing machine, the amount of fabric fed is greater at high speeds than at low speeds. , a phenomenon called "pitch error" occurs. However, the needle thread supply mechanism of conventional sewing machines is structured to supply the same amount of needle thread at low and high speeds, so the feed amount increases at high speeds (see b), as shown in Figure 5. The knot point N of the seam moves to the upper side of the cloth by the amount δ, which actually has the disadvantage of causing uneven tightness at high and low speeds.

Therefore, as a mechanism for managing the amount of upper thread let out in response to this pitch error, the thread is let out with an auxiliary thread take-up consisting of a thread let-out lever with a constant operating stroke, and the amount of let-out is controlled by an encoder and a solenoid. One controlled by ON/OFF timing, or one controlled by the ON/OFF timing of an encoder and solenoid that pays out the yarn using a seam processor roller instead of the above-mentioned auxiliary balance and detects the rotation amount of the motor. etc. are used.

[Problems to be Solved by the Invention] In other words, the conventional mechanism for solving the uneven tightness caused by the pitch error is a mechanism that electrically corrects and controls the amount of needle thread payout using an encoder or the like in accordance with the sewing speed of the sewing machine. and
This has the problem that the structure of the needle thread supply section becomes complicated.

The present invention has been made in view of the above problems, and has a simple structure, and has a structure in which the amount of needle thread supplied automatically corresponds to changes in the amount of cloth fed.
It is an object of the present invention to provide a needle thread supply device for a sewing machine that produces beautiful stitches without uneven tightness due to high and low speeds.

[Means for Solving the Problems] A needle thread supply device for a sewing machine according to the present invention has a needle bar to which a sewing machine needle is attached pivoted to a needle bar swing shaft, and tilts the needle bar in response to cloth feeding. In the needle feed sewing machine, a first thread holding means for restraining or releasing the upper thread along the thread path between the front stage of the thread take-up and the bobbin winder according to a control signal corresponding to the rotation angle of the needle bar swing shaft. and a second thread holding means, and an auxiliary thread take-up having a thread take-up lever that advances and retreats across the thread path in the thread path between the two thread holding means and creates a slack in the upper thread, and the auxiliary thread take-up includes the thread take-up lever as described above. It is driven by the rotation of the needle bar swing shaft, and when the rotation angle of the needle bar swing shaft is within the range of the thread pay-out angle, the thread pay-out lever is advanced or retreated, and the amount of the forward/backward movement is set as the cloth feed amount. The gist is that the upper thread is let out from the bobbin winder by forming a corresponding slack in the upper thread.

[Function] Therefore, when setting the supply amount of the upper thread, the auxiliary thread take-up is oscillated with the second thread holding means in the thread path closed, and the slack in the upper thread formed by the thread pay-out lever is removed. times, and the second thread holding means is opened with the first thread holding means closed to supply the upper thread. As a result, the amount of movement of the thread pay-out lever becomes proportional to the inclination angle of the needle bar, and the amount of needle thread supplied automatically changes in accordance with the amount of cloth fed. Therefore, even when a pitch error occurs due to a difference in sewing speed, the supply amount of the upper thread is automatically changed in accordance with the cloth feed amount, so that uneven tightness of the seams does not occur.

[Embodiment] Hereinafter, an embodiment of the needle thread supply device for a sewing machine according to the present invention will be described with reference to the drawings.

1 and 2 are principle diagrams of the main parts of a needle feed sewing machine.

The sewing machine 1 includes a sewing machine needle 4 attached to the lower end of a needle bar 3 which is pivoted on a needle bar swing shaft 2 that swings back and forth in conjunction with a driving source, and a thread take-up 5 that moves in conjunction with the vertical movement of the needle bar 3. Thread spool 6 of sewing machine upper thread supply source
An upper thread control mechanism is constructed in the thread path of the upper thread T between the thread take-up lever 5 and the thread take-up lever 5.

The reference numeral 7 designates an auxiliary lever protruding from the needle bar swing shaft 2 so that the thread letting-out lever 10 moves up and down between the thread guides 8 and 9 arranged in the thread path. Arrow A) indicates that the auxiliary take-up lever 7 is interlocked with the tilting of the needle bar 3 as the fabric is fed (arrow B), and moves up and down in proportion to the rotation angle of the needle bar swing shaft 2.

A first yarn holding means 1 for restraining or releasing the upper thread T is provided in the front yarn path and the rear yarn path of the auxiliary thread take-up 7, respectively.
1 and a second yarn holding means 12. Both yarn holding means 11 and 12 are configured to energize or de-energize solenoid coils 13 and 14, respectively, to hold the clamping board 1.
5 and 16 are magnetically driven, and the passing upper thread T is restrained or released at the solenoid operation timing shown in FIG.

In addition, the reference numeral 17 in the figure is a thread guide arranged as appropriate.
It constitutes a thread path for upper thread T passing through the needle hole of sewing machine needle 4.

In the fabric feeding device of the sewing machine having the above configuration, the sewing machine needle 4 that pierces the fabric is displaced by the fabric feeding operation, and the needle bar 3 is tilted (arrow B) corresponding to the amount of displacement. However, since the auxiliary thread take-up 7 of the needle thread supply device is integrated with the needle bar 3 via the needle bar swing shaft 2, the thread pay-out lever 10 of the auxiliary thread take-up 7, which protrudes into the thread path, is not connected to the needle. The vertical movement (arrow A) has an amplitude proportional to the rotation angle of the rod swing shaft 2.

As a result, when the feed amount of the cloth is changed, the amplitude of this auxiliary take-up lever 7 is also automatically changed, and a predetermined amount of upper thread T
In addition, the amplitude of the auxiliary thread take-up 7 is determined in accordance with the amount of feed even in the case of a pitch error caused by fluctuations in the sewing speed described above, so that uneven tightening does not occur.

Next, the needle thread supplying operation of the needle thread supplying device having the above structure will be explained with reference to the solenoid coil operation diagram in FIG. 4 while referring to the diagram for explaining the operation timing of the solenoid coil in FIG. 3.

(a) Set the top dead center of needle bar 3 to 0°.

At a timing near 0°, both solenoid coils 13 and 14 are in the ON state, and the first and second thread holding means 11 and 12 close the thread path and clamp the upper thread T, so that the auxiliary thread take-up 7 The needle thread T that has been let out is in a slack state as it is being let out between the thread guides 8 and 9.

(b) At the 40° position, when the solenoid coil 14 of the second thread holding means 12 is turned off, the slack in the upper thread T between the thread guides 8 and 9 is released so that it can be supplied to the thread take-up lever 5 side.

(c) In the vicinity of 60°, the needle thread T between the thread guides 8 and 9 is supplied to the thread take-up 5 side by the action of the thread take-up 5.

(d) The above-mentioned supply of the upper thread T ends at the top dead center of the thread take-up 5 at the 70° position.

(e) When the solenoid coil 14 of the second thread holding means 12 is turned on at the 80° position, the upper thread T is held on the thread take-up side 5.

(f) At the 180° position, when the solenoid coil 13 of the first thread holding means 11 is turned off, the upper thread T can be fed out.

(g) Near 220°, the thread pay-out lever 10 of the auxiliary thread take-up 7 descends and pulls down the needle thread T between the thread guides 8 and 9, whereby the needle thread T is paid out.

(h) At the 270° position, the auxiliary thread take-up 7 reaches the lowest point (this lowest point is displaced in proportion to the inclination angle of the needle bar 3), and finishes feeding out the upper thread T. While the thread T is still being let out, the solenoid coil 13 of the first thread holding means 11 is turned on.
Turn on and pinch the upper thread T.

After this, the operation returns to the above (a) and repeats the cyclic operation.

The amount of upper thread T that is paid out by the operations (a) to (h) above is determined by the positional relationship between the thread guides 8 and 9 and the lowest point of the thread payout lever 10 of the auxiliary thread take-up lever 7. As mentioned above, this positional relationship is determined by the swing axis of the thread letting-out lever 10.
It changes depending on the amount of cloth feed and the amount of pitch error. Furthermore, since this amount of let-out can also be changed by changing the relative positions of the thread guides 8 and 9, an upper thread tension adjustment mechanism is constructed in which the positions of the thread guides 8 and 9 are variable. You can also.

[Effects of the Invention] As described above, in the needle thread supply device of the sewing machine according to the present invention, since the drive source of the auxiliary take-up lever is taken from the needle bar swing shaft, the supply amount of the needle thread is equal to the feed amount of the cloth. In addition to automatically changing in response to pitch errors caused by differences in high and low speeds, the system has a very simple structure that eliminates mechanisms such as encoders. It is possible to form beautiful seams without uneven tightness at high and low speeds, and the effects of implementing the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a sewing machine head showing an embodiment of the needle thread supply device of a sewing machine according to the present invention;
The figure is a side sectional view of the main part, Figure 3 is an explanatory diagram showing the operation timing of the solenoid coil, Figure 4 a to h is an explanatory diagram showing the solenoid coil operation, and Figure 5 is a low speed time a and a high speed time b FIG. 3 is an explanatory diagram of a pitch error phenomenon showing stitches in the seam. 1-Sewing machine, 2-Needle bar swing axis, 3-Needle bar, 4-
Sewing machine needle, 5 - balance, 6 - thread winder, 7 - auxiliary balance,
8, 9 ~ Thread guide, 10 ~ Thread payout lever, 11
~First yarn holding means, 12~Second yarn holding means, 1
3,14~Solenoid coil, T~Upper thread.

Claims (1)

[Scope of Claims] 1. In a needle-feed sewing machine in which a needle bar to which a sewing machine needle is attached is pivoted to a needle-bar swing shaft, and the needle bar is tilted in response to fabric feed, A first thread holding means and a second thread holding means which restrain or release the upper thread along the thread path according to a control signal corresponding to the rotation angle of the needle bar swing shaft, and a space between the two thread holding means. an auxiliary take-up lever having a thread take-up lever that moves forward and backward across the thread path to create slack in the upper thread; the auxiliary take-up is driven by the rotation of the needle bar swing shaft; When the rotation angle of the needle bar swing shaft is within the range of the thread pay-out angle, the thread pay-out lever is moved forward and backward, and further, the amount of the forward-backward movement corresponds to the amount of cloth feed by creating slack in the upper thread. An upper thread supply device for a sewing machine, characterized in that the upper thread is fed out from the bobbin winder.