JPH0118155Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a reversal prevention device for sewing machines, and in particular, an upper feed device that feeds cloth in cooperation with a lower feed dog with an upper feed dog that performs four movements consisting of back-and-forth movement and up-and-down movement. This invention relates to a reverse rotation prevention device for an overlock sewing machine.

As an upper feed device for this kind of sewing machine, the present applicant previously filed Japanese Patent Application No. 57-216400 (Japanese Patent Publication No. 63-21513).
There is a type shown in FIG. 1, which was proposed in .

In this device, an upper feed dog 1 is provided at the free end of an upper feed table 4 that is rotatably pivoted in the vertical direction on a crank 3 fixed to a forward and backward feed shaft 2, and its back and forth movement is caused by the rocking of the crank 3. The vertical movement is performed by a bullet device 5 that pushes down the upper feed table 4, and a crank 7 that swings in the vertical direction in conjunction with the upper knife shaft 6 at the bottom of the upper feed table 4. When the crank 7 rotates upwards, it is lifted against the action of the ammunition device 5, and when the crank 7 rotates downwards, it is lifted up against the action of the ammunition device 5. However, as mentioned above, the ammunition device 5 always acts to push down the upper feed arm, so when the sewing machine is stopped, the main shaft is in a state where it can freely rotate, and the upper feed arm is lowered. When the base 4 is in a lifted state, the upper feed base 4 descends until the upper feed dog 1 reaches the cloth on the throat plate or the throat plate, which also pushes down the crank 7, reducing the rotational torque of the main shaft. Due to the action of inertia, it descends to the bottom dead center or near the bottom dead center, causing the main shaft to rotate in the opposite direction. Such reverse rotation of the main shaft becomes a problem when the upper feed dog is on its upward stroke. This is because stitch skipping will occur when the sewing machine is started again to start sewing. This will be explained in more detail based on FIGS. 2A to 2E.
Figures 2A to 2E show the stitch forming process of an overlock sewing machine using three threads, and the state shown in Figure 2E is that the upper feed dog 1 is lifted and the right looper 11 loops the left looper 12. 13, the sewing machine is stopped, and the main shaft rotates in the opposite direction due to the action of the spring as described above, the right looper 11 does not scoop the loop 13 and the right looper thread is shown in FIG. 2C before being scooped by the needle 14. Return to the state shown in . At this stage, unlike what is shown in the figure, the loop 13 is not attached to the right looper 11, so that when the sewing machine is driven again, skipped stitches occur. This phenomenon of skipped stitches due to reverse rotation of the main shaft occurs in other known types of upper feed devices in which the upper feed table is spring-loaded, as well as in overlock sewing machines using three threads as described above. This problem also occurs in double-thread overlock sewing machines that use left looper thread, and is particularly noticeable in sewing machines in which the upper feed dog acts rearward in the feed direction from the needle drop.

In order to eliminate the skipped stitch phenomenon mentioned above, it is possible to use a drive motor with a needle positioner so that the main shaft always stops at a fixed position, but using such a motor makes the sewing machine more expensive. I don't like it.

The purpose of this invention is to prevent reverse rotation of the main shaft immediately after the sewing machine is stopped in the upper feed device of a sewing machine where the upper feed table is spring-loaded as described above, and to prevent the above-mentioned skipped stitch phenomenon from occurring. It's about doing.

To explain this using drawings, the first embodiment shown in FIG. 3 has a known one-way clutch 22 fitted to a main shaft 21 protruding from the inside of the sewing machine to the outside, and a ratchet wheel 23 further fixed to the outside thereof. Claw wheel 23
In contrast, the main shaft 21 can only be rotated in one direction. A bell crank-shaped lever 26 having arms 24 and 25 extending in two directions is pivotally attached to the sewing machine body with a pin 27, and one arm 2
A spring 29 is hung between the arm 4 and a screw 28 attached to the sewing machine body, which urges the bell crank-shaped lever 26 in the clockwise direction in the figure.
A claw 30 formed at the end is engaged with the ratchet wheel 23.

In this state, the main shaft 21 can freely rotate counterclockwise, but the one-way clutch 22 works to rotate the main shaft 21 clockwise. Since this is prevented, clockwise rotation of the main shaft 21 does not occur.

According to this embodiment, the reverse rotation of the main shaft can be prevented as described above, and by rotating the bell crank-shaped lever 26 counterclockwise against the spring 29, the pawl 30 can be moved from the ratchet wheel 23. It can be detached and the main shaft can be rotated in either the forward or reverse direction as needed, such as when adjusting the sewing machine.

In this embodiment, an operating portion 31 is provided at the end of one arm 24 in order to rotate the bell crank-shaped lever 26 as described above. As mentioned above, if you want to rotate the main shaft in either the forward or reverse direction, and to maintain this for the necessary period of time, it is necessary to keep the operating part 31 depressed, and to do so, you must continue to hold it down manually. A lock means is provided for locking the bell crank-shaped lever 26 and restraining the lever.
It is desirable to maintain the pawl 30 in a state separated from the ratchet wheel 23. In the device shown as an example of the locking means, a stopper 33 is attached to the main body of the sewing machine with a screw 32 and has a stepped portion that engages with the upper end surface of the arm 24. In the illustrated example, the stopper 33 is formed with a step consisting of a high portion 34 and a low portion 35, and when the upper end surface of the arm is locked to the high portion 34, the pawl 30 is locked to the ratchet wheel 23, and the pawl 30 is locked to the low portion 35. The claws are designed to separate from the ratchet wheel when locked, but the steps on the high side can be omitted and only the steps on the bottom side are allowed.

The second embodiment shown in FIG. 4 has a gear 4 on a main shaft 41.
On the other hand, a shaft 46 is provided protruding from the end of one arm 45 of the bell crank-shaped lever 44, and a one-way clutch 47 is fitted onto the shaft so as to be rotatable in only one direction. The one shown in the figure is further provided with a stopper 49 similar to the first embodiment for the same reason as described above, and has a bell crank shape biased clockwise by a spring 50. Lever 4
When the upper end surface of the other arm 43 of the stopper 49 is engaged with the high part 51 of the stopper 49, it is detached.

In this embodiment as well, when the gears 42 and 48 are in mesh, the main shaft 41 can freely rotate in one direction, but the one-way clutch 47 works to rotate the main shaft 46 in the other direction. However, since the shaft 46 is fixed to the arm 45, the latter does not rotate.

In this embodiment as well, if the gear 48 is separated from the gear 42, the main shaft can be rotated in either the forward or reverse direction.

In this embodiment, the one-way clutch 47 is connected to the shaft 46.
However, even if it is provided on the main shaft side, the same effect as above will be produced.

In the above embodiment, the reverse rotation prevention device is provided on the main shaft that protrudes outside the sewing machine, but it may also be provided on the main shaft inside the sewing machine. In this case, a link mechanism is connected or a solenoid or air cylinder is used to move the lever to the outside. It is desirable to be able to operate it.

According to the present invention, it is possible to prevent the main shaft from rotating in the opposite direction due to the action of the elastic device immediately after the sewing machine is stopped, thereby preventing skipped stitches caused by the reverse rotation of the main shaft at the start of the next sewing. be able to. Moreover, since the one-way clutch prevents the main shaft from rotating in the opposite direction, during normal sewing when the main shaft rotates in one direction, it does not have any effect on other mechanisms of the sewing machine, which prevents their functions from being impaired or adversely affected. Nor.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the upper feed device of the overlock sewing machine, Figs. 2A to 2F are explanatory diagrams showing the seam formation process for edge stitching, Fig. 3 is a front view of the first embodiment, and Fig. 4 The figure is a front view of the second embodiment. 21...Main shaft, 22...One-way clutch,
23... ratchet wheel, 24, 25... arm, 26...
Bell crank-shaped lever, 29... Spring, 30...
Claw, 33...stopper, 41...main shaft, 42...
...Gear, 43, 45...Arm, 44...Bell crank lever, 47...One-way clutch,
48...gear, 49...stopper.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An upper feed arm that is pivotably supported in a vertically swingable manner by a member that reciprocates in the feed direction, and has an upper feed dog at its free end that faces the lower feed dog. , a vertical movement mechanism that includes a bullet device that presses down the upper feed arm, and a crank that swings vertically in conjunction with a main shaft on the underside of the upper feed arm and engages with the upper feed arm to move the arm up and down. In a sewing machine equipped with an upper feed device having a mechanism, the main shaft 2 is composed of one-way clutches 22 and 47 that rotate the main shaft in only one direction, and the main shaft 2 is rotated by the action of the elastic device when the sewing machine is stopped.
A reverse rotation prevention device for sewing machines that prevents reverse rotation of 1,41. (2) The one-way clutch 22 is configured to be able to rotate in only one direction by means of rotation prevention means consisting of a ratchet wheel 23 attached to the main shaft 21 and fixed to the one-way clutch 22, and a pawl 30 that meshes with the ratchet wheel 23. A reverse rotation prevention device for a sewing machine according to claim 1. (3) The one-way clutch 47 has a first gear 42 provided on the main shaft 41 side and a second gear 48 meshing with the gear, and one of the two gears is attached to a shaft that supports the gear. The reverse rotation prevention device for a sewing machine according to claim 1, which is fixed to a gear rotatably supported by a shaft, of a gear mechanism in which the other end is rotatably fixed to a shaft supporting the gear. . (4) The pawl 30 or the second gear 48 is rotatably supported by the sewing machine body, and is normally supported by springs 29, 5.
levers 26, 4 biased in one direction by
4, the ratchet wheel 23 or the first gear 42
A reverse rotation prevention device for a sewing machine according to claim 2 or 3, which is capable of being engaged and detached from the device. (5) Connect the pawl 30 or the second gear 48 to the pawl 23
Alternatively, the reverse rotation prevention device for a sewing machine as set forth in claim 4 is provided with a locking means for holding the first gear in a state separated from the first gear 42. (6) A reverse rotation prevention device for a sewing machine according to claim 5, wherein the locking means are stoppers 33, 49 that engage the levers 26, 44. (7) The reverse rotation prevention device for a sewing machine according to claim 6, wherein the stoppers 33, 49 are formed with steps consisting of high portions 34, 51 and low portions 35, 52.