JPH0625272Y2 - Sewing machine crack prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a device for preventing a crack of a sewing failure occurring during sewing by a sewing machine.

(Problems to be solved by the prior art and device) During sewing with a sewing machine, as shown in FIG. 12, a phenomenon in which the upper thread in the seam causes thread threading, that is, a sewing failure called warai occurs. As shown in FIG. 11a, this wari is a hook 28 which is needle thread catching means for the needle thread loop formed when the needle 17 that moves up and down and left and right moves up from the lowest position.
11b, the hook 28 pulls in and expands the needle thread loop as shown in FIG. 11b, and as shown in FIG. 11c, absorption of the upper thread by the balance starts immediately after the maximum expansion phase by the hook 28 has passed. The basic cause is that the upper thread 5a on the seam side is pulled up onto the cloth by the action as shown in FIGS. 11c to 11d, and the upper thread tightening phase (balance is as shown in FIG. 11e). It occurs when the stitch side needle thread pulled up in the phase slightly before the top dead center to the balance top dead center phase) is not pulled back by the needle thread tightening for some reason.

In order to prevent this cracking, the conventional technique is to dispose an elastic member that gives a weak resistance pressure on the stitch side upper thread path of the upper thread loop that is caught in the shuttle and bring the upper thread into contact with this elastic member. A device by a method of applying resistance has been proposed, but it is difficult for the upper thread to enter the contact portion of this elastic member,
Since this contact resistance is added when the upper thread is absorbed by the lifting of the balance, it is necessary to add thread tension by the upper thread tension device for pulling up, and as a result, a good sewing tension can be obtained with a weak upper thread tension. I could not do it.

An object of the present invention is to provide a device for preventing cracks while maintaining a weak needle thread tension.

(Means for Solving the Problem) In the present invention, the upper thread is pressed by pushing the upper thread to a position on the stitch side upper thread path where the upper thread loop is not always in contact with the upper thread while being caught by the hook. An upper thread presser for giving a pulling resistance to the thread is provided, and an upper thread presser that always acts on the upper thread and presses the elastic body is arranged facing the upper thread presser, and the upper thread presser is A wedge-shaped guide portion is provided on the entry side of the stitch side upper thread caught between the elastic body and the elastic body, and the opening means releases the upper thread to a specific phase.

(Operation) When the upper thread is pulled up by the balance of the upper thread loop that captures the upper thread loop generated by the vertical movement of the needle with the tip of the hook, the stitch side upper thread is moved from the wedge-shaped guide portion to the upper thread retainer. During the phase where it is held between the upper thread presser and pulled up on the cloth,
The upper thread presser presses the upper thread against the elastic upper thread presser body, and in the phase in which the needle side upper thread is pulled up, the upper thread presser is moved upward to tighten the pulling thread of the upper thread loop. Does not add resistance.

(Example) Next, the Example of this invention is described in detail with reference to drawings.

FIG. 7 is an external view of a computer sewing machine incorporating the crack prevention device of the present invention, and will be described with reference to FIG. 8 which is a mechanism explanatory view. A needle 17 is fixed to the tip of a needle bar 3 which is supported on the sewing machine frame 1 so as to be movable up and down, and a needle plate 18 is provided on the sewing machine frame 1 below the needle so as to face the needle 17.
Is fixed, and the needle hole 1 for allowing the needle 17 to project and retract
8a is provided. Below the needle plate, needle thread catching means driven in synchronization with the vertical movement of the needle 17 is arranged.

The needle plate 18 is provided with a feed dog groove 18b in which a feed dog 19 for gripping and feeding the cloth in cooperation with the cloth presser 20 comes in and out. Reference numeral 4 denotes a sewing pattern display portion, in which the sewing pattern and the selection number are displayed. Reference numeral 5 denotes a selection panel, which is provided with a ten-key 6 for selecting a sewing pattern represented by a number, and a display section 72 for displaying the number which is selected and operated. .

According to FIG. 8 of the configuration diagram, a needle bar 3 that is connected to a drive unit (not shown) and is connected to an upper shaft 2 to which rotation is transmitted is supported by the sewing machine frame 1 so as to be vertically movable. The needle bar 3 is a crank rod 9 rotatably connected to a shaft portion of a needle bar crank 8 fixed to one end of a crank 7 provided at the shaft end of an upper shaft 2 rotatably supported by the sewing machine frame 1. It is fixedly inserted through a needle bar holder 10 having a rotatable shaft portion at the other end, and is inserted through a needle bar support 11 at the upper and lower portions of the needle bar holder and supported so as to be vertically movable. The needle bar support is fitted on a shaft 12 fixed to the sewing machine frame 1, is restricted in vertical movement, and is supported rotatably only.

The other end of the needle bar support 11 is connected to an end of a connecting rod 13, and the other end of the connecting rod is an output shaft 14 of a stepping motor 14 for a needle bar swing fixed to the sewing machine frame 1.
It is connected to a through a fixed arm 15 and a link 16.

The feed dog 19 is fixed to a horizontal feed arm 21 driven by the drive shaft 2, and the amount of movement of the horizontal feed arm is adjusted by adjusting the swing angle of the horizontal feed arm. 22 is fixed to the shaft end of the adjusting shaft 23, and adjusts the amount of transmission to the horizontal feed arm 21 by the rotation of the feed adjuster. The arm 24 is fixed to the other end of the adjusting shaft 23.
And a crank 26 fixed to the output shaft of the feed adjusting stepping motor 25 fixed to the sewing machine frame 1 are linked 27.
Are connected via.

Reference numeral 28 denotes a hook serving as a needle thread catching means, which is rotatably supported by the sewing machine frame 1 below the needle plate 18 and is provided with the upper shaft 2
Lower shaft 29 that is rotated in synchronization with the needle bar 3 by
A fixed lower shaft gear 30 and a fixed hook gear 31 are integrally meshed with the lower portion of the shuttle 28.

32 is a known balance and is connected to the crank 7,
It is configured to move vertically.

In FIG. 9, an inner hook 36 is rotatably supported in the hook 28. The inner hook abuts against rotation stoppers 60 and 61 fixed to the sewing machine frame 1 to prevent rotation.

A bobbin thread drawing frame 62 is fixed to the outer circumference of the bobbin storage chamber 36a provided in the inner hook 36 and has a bobbin thread drawing port 62a. Reference numeral 63 denotes a lower thread tension spring, which is formed of a thin plate spring and has one end fixed to the lower thread drawing frame 62 with a screw 67.

The tip 63a of the bobbin thread tension spring 63 is located on the slit of the bobbin thread withdrawal opening 62a, and an opening is provided in the middle of the bobbin thread tension spring 63 so that the shaft portion of the headed screw 64 that can be adjusted from the outside can be inserted therethrough. There is.

The headed screw 64 is inserted into the opening of the lower thread tension spring 63 and screwed into the threaded hole of the lower thread drawing frame 62, and the head presses the lower thread tension spring 63 so that the tip 63a and the tip 63a. The pressing force between the lower thread withdrawal port 62a can be adjusted,
The tension of the lower thread pulled out from the lower thread outlet is adjusted. The bobbin is a bobbin wound with a lower thread 66, and is rotatably housed in the bobbin housing chamber 36a of the inner hook 36.

As shown in FIG. 2, the hook 28 has a shape in which the end of the hook 28 is brought into contact with a hook seat (neither is shown) fixed to the hook mounting plate fixed to the sewing machine frame 1. A hook shaft 34 having a step portion is inserted through a shaft hole provided at the center of rotation, and the hook shaft is fixed to the hook seat by bringing the step portion into contact with the hook seat.

A support plate 37 is fixed to the inner hook 36 supported by the hook 28 in parallel with the wall 36b, and the thread engaging portion 38a of the feeding lever 38, which is vertically driven, is connected to the lower surface of the needle plate 18 during this time. The clearance S with the wall 36a and the clearance S ₁ with the support plate 37 are set and positioned between the upper surface of the inner pot 36 and the upper surface.

As shown in FIG. 1, the feeding lever 38 has the thread engaging portion 38.
Both ends of a are bent and holes are provided at the tip. A pair of pins 4 fixed to the rising portion of the hook chamber cover 45 fixed to the hook mounting plate.
0 and 41 are fitted, and the feeding lever 38 is rotatably supported with the pair of pins 40 and 41 as the center of rotation.

Regarding the bobbin thread delivering action by the operation of the delivering lever 38, Japanese Patent Application No. 62-92987 filed by the applicant of the present invention has been applied.
The details are omitted because they are the same as.

The delivery lever 38 is connected to a delivery link 43 that is driven by a delivery cam 42 that is fitted and fixed to the lower shaft 29 that rotates in synchronization with the upper shaft 2, and a stepping motor 44 that adjusts the swing amount of the delivery link. The feeding lever 38 is moved up and down by the rotation of the feeding cam 42, and the lower thread 66 is pulled out from the inner hook 36.

The stepping motor 44 is configured to adjust the swing amount of the feeding link 43 to adjust the operating amount and operating phase of the feeding lever 38.

Next, details of the crack prevention device will be described. In FIG. 3, reference numeral 45 denotes a shuttle chamber cover fixed to a shuttle mounting plate fixed to the sewing machine frame 1, and the shuttle chamber cover 45 is provided with a hole 45a penetrating in the vertical direction. An operating pin 47 is inserted through the hole so as to be movable in the axial direction.

An open arm support 48 is provided on the side surface of the shuttle chamber cover 45 with a screw 4
It is fixed integrally by 9. A pin 50 is integrally formed on the lower portion of the open arm support, and a hole formed at one end of the open arm 51 is fitted on the pin. The open arms 5
The other end of 1 is a flat surface portion 51 that extends and is parallel to the lower shaft 29.
a is formed, is located on the open cam 52 fitted and fixed to the lower shaft 29, and is abutted and driven by spring means (not shown).

The operating pin 47 is in contact with the open arm 51 by its own weight. Alternatively, the operating pin 47 may be pressed downward by spring means so that the opening arm 51 is brought into contact with and driven by the opening cam 52.

1 and 3, reference numeral 53 denotes an upper thread presser, which is formed by bending an elastic material into a U-shape, and the lower base end thereof is fixed to the sewing machine frame 1 with a screw 54. ing. An adjusting screw 55 is screwed into a screw hole portion 53b provided on the upper side of the needle thread presser, and a nut 56 is attached to the adjusting screw 55 above the upper thread presser 53, so that the adjusting screw 55 It constitutes a Yurumi stop after adjustment.

The lower part of the adjusting screw 55 is arranged at a position facing the upper end of the operating pin 47.

The upper free end 53a of the upper thread presser 53 to which the adjusting screw is attached is an upper thread presser made of an elastic member that is fixed to the mounting portion 37a of the support plate 37 formed below the upper surface of the inner hook 36. The operating pin 4 is extended from the left on the body 57.
In a state where the upper end 47a of 7 does not contact the tip of the adjusting screw 55, the upper thread pressing body 57 and the upper thread pressing 53
Are located so as to abut.

The upper surface of the upper thread presser 57 is located above the upper end of the shuttle 28 as shown in FIG.
a is formed below the upper end of the hook.

Next, the operation of the crack prevention device of the present invention will be described with reference to FIG.

In FIG. 10, a indicates that the needle 17 is ascending from the needle bottom dead center, and the needle thread loop held by the needle 17 is connected to the blade tip 2 of the hook 28.
8a is the phase to be captured. In this phase, as shown in FIGS. 3 and 4, the flat portion 51b of the open arm 51 is in contact with the small diameter portion 52a of the open cam 52, and the open arm 51 is in the position rotated counterclockwise. Therefore, the operating pin 47 is located below, and a clearance a is set between the tip 47a of the operating pin and the adjusting screw 55.

Therefore, the tip 53a of the upper thread presser 53 is in contact with the upper thread presser 57.

In FIG. 10, b is the phase in which the needle 17 moves up and the sword tip 28a of the shuttle 28 expands the needle thread loop. The upper thread is pulled out by the rotation of the sword tip 28a, and the expanded upper thread loop The stitch side upper thread is drawn out to the upper side of the inner hook 36 as shown in the drawing, and the needle side upper thread is drawn to the lower side of the inner hook 36. The stitch side needle thread drawn to the upper side of the inner hook 36 is The upper thread presser 53 comes into contact with the lower side of the upper thread presser 53, and the upper thread presser 57 and the upper thread presser 53 are rotated by rotating the blade tip 28a of the hook.
Will be guided between.

As shown in FIG. 4, the inlet 57a of the upper thread presser 57 is provided with a guide portion 57b which is inclined on the inlet side, and the upper thread presser 53 is attached to the upper thread presser 57 as in FIG. 10a. In the abutted state, the inlet has a wedge-shaped space, and guides the stitch side upper thread.

Next, in FIG. 10 (c), the hook 28 further rotates and the upper thread loop is in a phase after the maximum withdrawal, and the upper thread loop causes a talmi, whereby the upper thread pulling action by the balance 32 is performed. It is a phase.

By pulling up the upper thread, the needle side upper thread passing through the lower side of the inner hook 36 shown by the dotted line in the figure is pulled up to absorb the talmi of the upper thread loop, and further tension is given to the stitch side upper thread. Due to the tension of the tension, the stitch side needle thread enters between the upper thread presser 53 and the upper thread presser 57 in the contact state shown in FIG. 4 and the resistance due to the elasticity of the upper thread presser 53. Is given.

Therefore, the stitch side upper thread is held against the rise of the needle side upper thread due to the rise of the balance 32 until the release phase of d in FIG. 10, and the stitch is increased as the needle side upper thread rises. The needle side upper thread is absorbed without pulling up the side upper thread.

In FIG. 10, d is a phase slightly before the top dead center of the balance, and is a phase in which the needle-side upper thread is absorbed from the lower side of the inner hook 36 by the absorption action of the balance 32 and remains above. In this phase, as shown in FIG. 5, the flat portion 51b of the open arm 51 is in contact with the large diameter portion 52b of the open cam 52, and the open arm 51 is rotated clockwise about the pin 50. The operating pin 4 that abuts on the flat portion 51b of the open arm.
7 is pushed upward in the axial direction, and the upper end 47a of the operating pin is pushed.
Comes into contact with the adjusting screw 55 fixed to the upper thread presser 53 and pushes up the upper thread presser 53.

As a result, as shown in FIGS. 5 and 6, a gap b is generated between the upper thread pressing body 57 and the tip 53a of the upper thread pressing 53.

Since this phase is a little before the top dead center phase of the balance 32, at the top dead center phase of the balance as shown in Fig. 10e, the upper thread talmi remaining under the needle plate 18 is further pulled up and absorbed. To do.

Further, as shown in FIG. 10f, the stitch is tightened by the lowering of the needle 17 to form the stitch.

(Effect) As described above, according to the present invention, the wari which is generated during sewing by the sewing machine is prevented, and the upper thread of the seam side is formed into a wedge shape by the withdrawing action of the hook when the upper thread of the hook is the needle thread catching means. To the resistance applying section, and the upper thread is pulled up by the balance to be held in the resistance applying section.The resistance applying section is opened in a phase where the needle thread on the needle side is almost pulled up, and the upper thread pull-up seam is tightened by the balance. By doing so, it is possible to prevent the occurrence of cracks only by automatically holding the thread on the seam side by the pulling action of the shuttle and opening it in the open phase.

[Brief description of drawings]

1 to 10 relate to an embodiment of the present invention, FIG. 1 is an explanatory view of a crack prevention device, and FIG. 2 is a partial sectional view thereof.
FIGS. 6 to 6 are explanatory views of the operation of the crack prevention device, FIG. 7 is an external view of the sewing machine, FIG. 8 is an explanatory view of the sewing machine mechanism, FIG. 9 is an explanatory view of the lower thread adjusting portion, and FIG. FIG. 11 is an explanatory view of seam formation when the device is operated, FIG. 11 is an explanatory view of a conventional seam formation, and FIG. 12 is an explanatory view of seam of warai, 17 is a needle, 18 is a needle plate, and 28 is a needle thread catcher. Means as a hook, 36 as an inner hook, 52 as an opening cam, 53 as a needle thread presser, 5
7 is a needle thread pressing body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-151088 (JP, A) Actually open 1-14380 (JP, U) Actually open 56-168067 (JP, U) Actually open 61- 10630 (JP, Y2)

Claims (2)

[Scope of utility model registration request] 1. A stitch forming means comprising a needle fixed to the tip of a needle bar movably supported on a sewing machine frame and a needle thread catching means cooperating with the needle, and held by the needle thread catching means. A bobbin thread tension adjusting device mounted on the inner hook, a needle plate fixed to the sewing machine frame and provided with a needle hole through which the needle appears and disappears, and an opening that rotates in synchronization with the vertical movement of the needle bar. A cam, an operating pin that reciprocates by the rotation of the opening cam, an upper thread pressing member provided on the upper surface of the inner hook and above the upper end of the needle thread catching unit, and one end of which is supported by the sewing machine frame. And the upper end of the operating pin moves up and down to move the upper end of the upper end of the upper and lower ends of the upper and lower ends of the upper pin and the upper end of the sewing pin to hold the upper thread at the time of joining. Crack prevention device. 2. The upper thread lay of a sewing machine according to claim 1, wherein one of the upper thread retainer and the upper thread retainer is formed of an elastic member. Prevention device.