JPH0424082A - Basting sewing machine thread tension device - Google Patents

Abstract

PURPOSE:To expand a cloth feeding period, while ensuring good stitch balance of basting by providing a resistance changeover mechanism in a thread tension guide such that the rotational resistance of a thread guide rotary body is changed over synchronously with an upper shaft through a cam mounted on said shaft and a rod in sliding contact with said cam. CONSTITUTION:In a thread tension guide of a basting sewing machine M, when an upper shaft 7 rotates during the sewing, a cam 29 of a resistance changeover mechanism 20 rotates, the rotational resistance of a thread guide rotary body 23 of a rotary type thread tension guide 14 is changed over synchronously with the shaft 7 through a rod 31. Within a period of time from a predetermined timing between the highest position of a needlebar 5 and that of a balance 11 to the timing when a sewing needle 6 is sticked into a fabric, the rotational resistance of the guide 14 becomes small enough to allow the feeding of the fabric and hence the fabric can be fed during this period. Furthermore, since a small resistance is imparted to a needle thread 12 in this surface, a small tension by the balance 11 is surely and property effected, wherein loosening of the needle thread does not practically occur, so that the thread does not slip out of a thread path.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thread tension device for a basting sewing machine, and in particular, a rotary thread adjustment device is provided and interlocked with a cam on the upper shaft to control the cloth feeding period. Concerning enlarged things.

[Prior Art] In a basting sewing machine for applying basting stitches to workpiece cloth, a presser foot supporting the presser foot is connected to the upper shaft via a link mechanism, and when the sewing needle descends, it descends, and the sewing needle touches the workpiece cloth. The sewing needle is used to hold down the workpiece cloth while it is inserted into the workpiece, and when the sewing needle rises above the workpiece cloth, the presser foot also rises, and due to the characteristics of basting kimono, the tightening force of the upper thread is very weak. Since the feed stroke of the work cloth is large, the feed of the work cloth is carried out manually.

In conventional basting sewing machines, a thread tension device having a pair of tension discs is provided in the middle of the thread path from the upper thread supply source to the sewing needle, and the thread tension device is connected to a cam attached to the upper shaft via a rod. The upper shaft was connected to the upper shaft to open and close the adjustment plate. Regarding the characteristics of this thread tension device,
During the period from the time when the thread take-up reaches the highest position (upper shaft phase angle approximately 60°) and tightening of the upper thread is completed to the time when the sewing needle inserts into the workpiece cloth (upper shaft phase angle approximately 100°), the workpiece cloth For manual feeding, the tension disc is opened to reduce the resistance applied to the upper thread to zero, and during other periods, the tension disc is closed to apply a predetermined resistance to the upper thread.

Heretofore, zigzag stitch sewing machines for performing zigzag stitches on thin fabrics using a thin needle thread have been equipped with a rotary thread tension device that can precisely adjust the small tension of the needle thread.

[Problems to be Solved by the Invention] In conventional basting sewing machines, the tension plate is opened after the thread take-up reaches the highest position and tightening of the upper thread is completed, and the period in which workpiece cloth can be fed is limited to the phase angle. Approximately 60° to approximately 100
The problem was that it required considerable skill to get used to feeding the cloth because it was limited to a short period of 100°.

In addition, a tension plate-type thread tension device was installed, and the tension plate was opened during cloth feeding so as not to apply any resistance to the upper thread. Therefore, in order to extend the fabric feeding period, the opening timing of the tension plate was changed to, for example, phase 0. If the speed is increased to around °, the needle thread will be pulled out from the thread supply source with almost no resistance when the needle thread is tightened by the thread take-up. There is a problem that basting stitches with good thread tension cannot be obtained.

Furthermore, since the needle thread is released in the thread tension device when feeding the work cloth, the needle thread becomes slack when feeding the work cloth in large strokes, and the needle thread is loosened from the thread tension device or thread hook in the thread path. There were problems such as the upper thread coming off frequently.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thread tension device for a basting sewing machine that can extend the cloth feeding period while ensuring good thread tension for basting, and can prevent loosening of the needle thread.

[Means for Solving the Problems] A thread tension device for a basting sewing machine according to the present invention is a basting sewing machine used for basting, in which a rotary thread tension device is installed in the middle of a thread path from an upper thread supply source to a sewing needle. and the thread tension device is provided with a resistance switching mechanism that timely switches the rotational resistance of the thread guide rotating body of the thread tension device to the upper shaft via a cam provided on the upper shaft and a rod that slides on the cam. , during the period from the predetermined timing between the highest position of the needle bar and the highest position of the thread take-up to the timing when the sewing needle inserts into the workpiece cloth, the rotational resistance becomes a small resistance suitable for feeding the workpiece cloth, and during other periods, The shape of the cam is set so that the rotational resistance is greater than the small resistance.

[Function] In the thread tension device of the basting sewing machine according to the present invention, when the special sewing shaft rotates, the cam of the resistance switching mechanism rotates, and the rotational resistance of the thread guide rotor of the rotary thread tension device is changed via the rod. is switched according to the upper axis. During the period from the predetermined timing between the highest position of the needle bar and the highest position of the thread take-up to the timing when the sewing needle inserts into the workpiece cloth, the rotational resistance of the thread tension regulator becomes a small resistance suitable for feeding the workpiece cloth. It is possible to feed the work cloth during the period.

Moreover, since a small resistance is applied to the upper thread even during this period, the loose tightening of the upper thread by the thread take-up is performed reliably and appropriately, and there is almost no loosening of the upper thread, and the upper thread is not pulled up from the thread path. The thread never comes off.

[Effects of the Invention] According to the thread tension device of the basting sewing machine according to the present invention,
As explained in the [Function] section above, the fabric can be fed over an extended period from the predetermined timing between the needle bar top position and the thread take-up top position to the timing when the sewing needle inserts into the workpiece fabric. This allows even inexperienced operators to feed the cloth reliably, and even during this period, a small amount of rotational resistance is added, so the loose tightening of the upper thread can be done reliably and appropriately, and good thread tension for basting stitches can be obtained. Also, the upper thread is hardly loosened and the upper thread does not come off the thread path.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is an example in which the present invention is applied to a thread tension device of a basting sewing machine (hereinafter referred to as a sewing machine) exclusively for basting.

As shown in Figures 1 to 3, the basting sewing machine M is
bed part 1, pillar part 2, arm part 3, arm part 3
The needle bar 5 and the sewing needle 6 at its lower end are reciprocated up and down via a crank mechanism by an upper shaft 7 which is rotationally driven by a sewing machine motor, A presser foot 9 is provided at the lower end of the presser bar 8 provided on the rear side, and the presser bar 8 is connected to the upper shaft 7 via a link mechanism.
The presser foot 8 is reciprocated up and down in synchronization with the needle bar 5, and the presser foot 8 is lowered in conjunction with the lowering of the needle bar 5, and when the sewing needle 6 is inserted into the work cloth W, the presser foot 9 is moved. The presser foot holds the workpiece cloth W while the sewing needle 6 is inserted into the workpiece cloth W, and is held in a state holding the workpiece cloth W, and as the sewing needle 6 moves upwards above the workpiece cloth W, the presser foot Tribute 8 is now rising. In basting, the amount of feed of the work cloth W per stitch is very large, so the feed of the work cloth W is performed manually when the presser foot 9 is not pressing the work cloth W.

A horizontal hook 10 is provided in the head portion 1 below the sewing needle 6, and the horizontal hook 10 is interlocked and connected to the upper shaft 7 and is driven to rotate in synchronization with the upper shaft 7.

A balance 11 is provided on the head 4, and the balance 11 is reciprocated up and down by the upper shaft 7 via a crank mechanism and a link mechanism.

Note that the mechanisms for driving the needle bar 5, presser bar 8, horizontal hook 10, and thread take-up 11 are the same as existing mechanisms, and detailed explanations thereof will be omitted.

The thread path of the needle thread 12 from the needle thread supply source (not shown) to the sewing needle 6 includes a first guide tool 13 provided near the front end of the upper end of the center portion in the left-right direction of the arm portion 3, and a first guide tool 13 provided on the left side of the first guide tool 13. A rotary thread tension device 1 is provided at the center of the front end of the arm portion 3.
4, a thread guide 16 provided at the front end of the head 4 on the left side and below this and having a thread take-up spring 15, and a thread take-up 11.
The thread holding part 11a, the second guide tool 17, and the third guide tool 1
8, the fourth guide tool 19, and the guide portion 5a at the lower end of the needle bar 5.
and is provided.

Next, based on FIGS. 4 to 6, the rotary thread tension device 14 is
A resistance switching mechanism 20 that operatively connects the rotational resistance to the upper shaft 7 and switches the rotational resistance in accordance with the timing of the upper shaft 7 will be explained.

The arm portion 3 is provided with a horizontal sleeve shaft 21 spaced in the front-rear direction, the front end of the sleeve shaft 21 protrudes outside the front surface of the arm portion 3, and the front end of the sleeve shaft 21 is provided with a first disk in order from the rear side. A plate 22 and a groove-shaped thread guide portion 23 on the outer periphery.
A thread guide rotating body 23 having a diameter of 1.a, a second disk plate 24, a spring receiver 25, a compression coil spring 26, an operating knob 27 for receiving the outer end of the spring 26, and a screw 28 are attached, The first disk plate 22, the thread guide rotating body 23, the second disk plate 24, and the spring receiver 25 are connected to the sleeve shaft 21.
At least the thread guide rotor 23 is rotatably mounted on the sleeve shaft 21 , a stepped portion 21 a is formed on the sleeve shaft 21 behind the first disk plate 22 , and an operating knob 27 is mounted on the sleeve shaft 21 so as to be movable in the axial direction. is screwed onto the tip of the sleeve shaft 2 so that its position can be adjusted in the axial direction.

When the first disc plate 22 is received by a rod 31 (described later), the second disc plate 24 is pressed rearward by the elastic force of the spring 26, and the thread guide rotor 23 is moved between the first disc plate 22 and the second disc plate. 24, and rotational resistance is added according to the spring force. By adjusting the spring force via the operating knob 27, the rotational resistance can be finely adjusted.

As shown in FIGS. 6 and 7, the locking portion 2 of the sleeve shaft 21
1a, a dividing gap 21b extending in the axial direction and having a thickness of approximately 173 mm in diameter is formed in the sleeve shaft 21, and dividing shaft portions 21c are formed on both sides of the dividing gap 21b, and the first disk plate 22 is formed with a pair of divided shaft holes into which the divided shaft portions 21c are inserted, and a bridge-like input portion 22a that projects rearward is formed between both divided shaft holes.

On the other hand, at a position corresponding to the rear of the sleeve shaft 21,
The upper shaft 7 has a cam 2 shaped as shown in Figs. 4 and 5.
9 is fitted onto the outside and fixed with two screws 30, and the sleeve shaft 2
1 has a shaft hole 21 connected from the rear end to the dividing gap 21b.
d is formed, and a rod 31 is attached to the shaft hole 21d so as to be slidable in the axial direction.The rear end of the rod 31 contacts the cam surface on the outer periphery of the cam 29, and the front end of the rod 31 contacts the first disc. It is in contact with the rear end surface of the input section 22a of the plate 22.

The characteristics of the cam 29 will be explained based on FIGS. 4 and 8.

Points A, B, C, D in Figure 4 and points a, b, C, d in Figure 8
The more the cam 29 pushes the rod 31 forward, the more the first disk plate 22 is pushed forward, the more the elastic deformation of the spring 26 increases, and the more the spring force increases. The rotational resistance applied to the yarn guide rotating body 23 increases.

From point B (corresponding to phase angle θ=0°) of cam 29 to point C (!
! For example, when the tip of the needle 6 reaches the work cloth W, the phase angle is θ-98.
°), the radius of the cam surface is set small,
The radius of the cam surface rapidly increases from point C to point A and from point B to point A, and from point C to point A, the radius of the cam surface becomes a constant large value.

As a result, as shown in Fig. 8, during the period from θ-0'' timing (point b) to θ-98° timing (point C), the rotational resistance is small enough to be suitable for feeding the work cloth W. In other periods, the rotational resistance is set to be larger than the small rotational resistance.

The operation of the thread tension device of the basting sewing machine described above will be explained.

A rotary thread tension device 14 and a resistance switching mechanism 20 are provided,
Since the characteristics of the cam 29 of the resistance switching mechanism 20 are set as described above, it is possible to manually operate the cam 29 over an extended period from the early timing of the phase angle θ-〇° to the timing when the sewing needle 6 is inserted into the workpiece cloth W. It becomes possible to feed the work cloth W. Since the period during which the cloth can be fed is extended in this way, even an unskilled person can feed the cloth smoothly.

Moreover, even during the cloth feeding period, the thread guiding rotary body 2
Since a small rotational resistance is added to the needle thread 12 by the thread take-up thread 11, a thread tension suitable for basting can be obtained, and even when the work cloth W is fed with a large stroke, the thread does not tighten. The needle thread 12 does not become loose in the thread path, and the needle thread 12 does not come off the thread path.

Since rotational resistance increases during periods other than the cloth feeding period, the upper thread 12 does not loosen. And upper thread 12
An intertwining point between the thread and the bobbin thread is reliably formed on the lower surface of the work cloth W.

If the rotational resistance is reduced from a timing earlier than the phase angle θ=0°, the thread separation from the rotary hook 10 will be poor, and the intertwining point of the upper thread 12 and the lower thread will be at a lower position away from the work cloth W. This is undesirable because it may cause the tension to be formed by the thread take-up lever 11 to become ineffective, resulting in a significant decrease in thread tension.

Note that the characteristics of the cam 29 have been changed so that the cam 29 is slower than the needle bar uppermost position and is slower than the needle bar uppermost position (for example, the phase angle θ
-60°) to the timing at which the sewing needle 6 inserts into the workpiece cloth W, the rotational resistance may be set to be small to enable cloth feeding.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is a front view of the main parts of the basting sewing machine, Fig. 2 is a plan view of the arm and head, and Fig. 3 is a side view in the direction of Fig. 1. , Figures 4 and 5 are explanatory diagrams of the operation of the thread tension regulator and resistance switching mechanism in each state, Figure 6 is a sectional view of the main parts of the thread tension regulator and resistance switching mechanism, and Figure 7
The figures are a sectional view taken along line 6 in Figure 6, and a diagram for explaining rotational resistance characteristics, etc. in Figure 8. M... Basting sewing machine, 7... Upper shaft, 12...
Upper thread, 14... Rokuri type thread tension device, 20... Resistance switching mechanism, 23... Thread guide rotor, 29... Cam,
31...Rod.

Claims (1)

[Claims] (1) In a basting sewing machine used for basting, a rotary thread tension device is installed in the middle of the thread path from the upper thread supply source to the sewing needle, and the thread tension device has a cam and a cam provided on the upper shaft. A resistance switching mechanism is provided that changes the rotational resistance of the thread guide rotating body of the thread tension regulator in a timed manner to the upper shaft through the sliding rod, and the sewing needle is machined at a predetermined timing between the top position of the needle bar and the top position of the thread take-up lever. The shape of the cam is set so that the rotational resistance becomes a small resistance suitable for feeding the work cloth during the period up to the timing of piercing the cloth, and the rotational resistance becomes larger than the small resistance during the other period. A thread tension device for a basting sewing machine characterized by the following settings.