JPS601038B2 - Sewing machine presser foot lifting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a presser foot lifting device for a sewing machine, and more particularly to its presser foot lifting mechanism and needle thread adjuster.

In general, the presser foot lifting mechanism of a sewing machine presses the workpiece against the throat plate with a predetermined pressure during sewing, and removes the presser foot pressure when the sewing machine is stopped or when the workpiece is attached to or removed from the throat plate.

The upper thread regulator is a device that reduces the tension on the upper thread when the presser foot pressure is removed by the operation of the presser foot lifting mechanism, and this makes it easier to pull out the upper thread when attaching or removing the sewing item. The configurations of the presser foot lifting mechanism and needle thread adjuster will be explained below with reference to the drawings.

1 and 2 are an end view and an exploded perspective view of a sewing machine head showing a conventional presser foot lifting mechanism and needle thread adjuster, and FIG. 3 is a structural diagram showing details of the presser foot lifting lever. It is.

First, the configuration of a conventional presser foot lifting mechanism and needle thread adjuster will be explained based on these figures. 1 is a presser bar 0, which is iron-coupled to a metal 4 fixed to an arm 2 with a screw 8.

A presser portion 5 is fixed to the lower end of the presser bar 1 with screws 6, and a presser bar holder 7 is fixed to the upper end of the presser bar 1 with screws 8. A picket 1 and 9 are seated on the upper end surface of the presser bar 7, and a guide rod 10 is inserted into these 5 pickles. At the tip of this guide rod 10, as shown in FIG.
A mushroom-shaped pedestal 11 is provided, and this pedestal 1 1
is locked to the upper end of the helical spring 9. The lower end of a thumbscrew 12 attached to the arm 2 is in contact with the tip of the pedestal 11. And the above guide 1
The lower end of the presser foot 1 is inserted into a cylindrical hole 13 made at the upper end of the presser foot 1, and by rotating the thumbscrew 12, the compression spring force of the helical spring 9 against the presser rod 11 is set and controlled. There is. An arm 16 of a presser foot lifting lever 15 is engaged with the lower side of the arm 14 of the presser foot lifter 7. As shown in FIG. 3, this presser foot lifting lever 15 has two arms 16, 17 and a pressing surface 18, and is provided with a fulcrum hole 19 and a connecting hole 20. The pressing surface 18 is formed into a flat surface with a stepped depth h, and the boundary portion 21 with other surfaces is finished into a curved surface. As shown in FIG. 2, the presser foot lifting lever 15 has a fulcrum hole 19 attached to the arm 2 with a stepped screw 22. Further, an end portion of a connecting rod 23 is connected to the connecting hole 20 by a stepped screw 24. The other end of this connecting rod is connected to the arm of a rotary lever 26 by a stepped screw 25. This rotating lever 26
is attached to the inner wall of the arm 2 by a stepped screw 27, and the upper end of the operating lever 28, which is bent into a copper shape, is inserted into a hole made in the other arm of the rotating lever 26, and is secured with a snap pin 29. It's stopped. The lower end of the operating lever 28 is supported by a knee-raising pin 3 fixed to an oil pan (not shown), and the other end of the pig-raising pin 30 is supported by a knee-raising arm 31. A knee-raising shaft 32 is fixed to this knee-raising arm 31, and a pig operation plate 35 is fixed to the other end of this pig-raising shaft 32 via a bar supporter 33 and an arm 34. The above mechanism constitutes a knee-operated presser foot lifting mechanism.
On the other hand, the upper thread adjuster is constructed as follows.

The tip of a pin 36 is opposed to the pressing surface 18 of the rotary lever 15, and the tip of the pin 36 is formed into a curved surface such as a hemispherical shape. As shown in FIG. 1, the central portion of the pin 36 is inserted into and supported by a support hole 38 of a support base 37 provided inside the arm 2. The other end of the pin 36 is passed through a bush 39 fixed to the side wall of the arm 2 and is exposed to the outside. As shown in Fig. 2, the stepped part 3 of this push 39 has a ring 4 for preventing oil leakage.
0 is tied together. Further, a tension rod 41 is inserted into the upper bush 39 and fixed to the bush 39 with a screw. A thread take-up spring 42 is fitted around the outer periphery of the tension rod 41 within the bush 39. Tune bar 4 above
The other end of 1 is formed into a tuning fork-shaped split screw 43.
The other end of the pin 36 inserted into the bush 39 is
It passes through a hole made in the chest core of the tension rod 41 and projects inside the split screw 43. Two adjustment discs 44, 44, a adjustment disc retainer 45, a conical spring 46, and a detent 47 are arranged in order on the outer periphery of the split screw 43.
It has been concluded. Therefore, the compression spring force of the conical spring 46 is applied to the other end of the pin 36 via the tension plate holder 45, and the upper thread supplied from the outside of the sewing machine is passed between the two tension plates 44, 44. As a result, appropriate tension is applied to the needle thread between the tension plate and the needle.
Next, the functions of this presser foot lifting mechanism and upper thread adjuster will be explained.

When the knee operating plate 35 is pressed by the pig operation and the knee raising shaft 32 is rotated, the knee raising pin 30 and the operating lever 28 are lifted.

When the operating rod 28 is lifted, the rotating lever 26 rotates and the connecting rod 23 is pulled in the direction of arrow A shown in FIG. When the connecting rod 23 is pulled and displaced, the presser foot lifting lever 15 rotates, and the presser foot 1 is lifted by the arm 16 of the presser foot lifting lever. Along with this, the compression spring force of the helical spring 9 that was pressing the sewing material on the throat plate (not shown) via the presser foot 5 is removed. On the other hand, as the presser foot lifting lever 15 rotates, the relative position of the pin 35 with respect to the presser foot lifting lever 15 moves from B to C shown in FIG. 3.

Therefore, the pin 36 is displaced in the axial direction (in the direction of the arrow ◯ in FIG. 1) by an amount equal to the stepped depth h' of the pressing surface 18. When the superposition pin 36 is displaced, the adjustment discs 44, 44
Since the compressive spring force of the conical spring 46 against is reduced,
Upper thread tension is reduced. In the conventional presser foot lifting mechanism and upper thread adjuster described above, the operating point of the upper thread adjuster with respect to the rise of the presser foot 5 caused by the pig operation is constant.

This is because when sewing with the presser foot 6 slightly lifted by the pig operation, the tension of the needle thread decreases and sewing becomes impossible. In some cases, the presser foot lifting mechanism may be activated briefly or instantaneously by a pig operation to perform sewing when pulling back the sewing material instantaneously. However, in the above-mentioned conventional device, the upper thread adjuster is only configured to operate immediately after the knee-operated presser foot lifting mechanism starts to operate, and therefore, under usage conditions such as sewing while raising the presser foot 5 slightly, In the case of It is conceivable to increase the length of the pressing surface 18 of the presser foot lifting lever 15 shown in the figure and always delay the activation point of the needle thread adjuster with respect to the activation point of the presser foot lifting mechanism. As can be seen from FIG. 1, the rotational fulcrum of the presser foot lifting lever 15 is very narrow in terms of space, and it is difficult to replace it with such a presser foot lifting lever if necessary. Since the connecting rod 23 is connected to the arm 17, it would be very time-consuming and unreasonable to replace it with a corresponding presser foot lifting lever under the above-mentioned conditions of use. This invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to enable the operating point of the upper thread regulator to be easily changed as required.

FIG. 4 is an exploded perspective view showing a presser foot lifting lever and a pressing plate, which are the main parts of this invention, FIG. 5 is a perspective view showing the pressing plate and positioning plate, and FIG. This is an explanatory diagram showing the adjustment status at the time of operation of the thread regulator, and the following explanation will be based on these diagrams, and the other parts will be omitted because they are the same as the conventional ones described above.

In FIG. 4, 49 is a presser foot lifting lever, and the shape of this presser foot lifting lever 49 is almost the same as that of the conventional one.
This presser foot lifting lever 49 is not provided with a pressing surface.

Instead, a feature is that a positioning protrusion 50 is provided in addition to the fulcrum hole 19 and the connection hole 20. Reference numeral 51 denotes a press plate, and a part of the press plate 51 has a press surface 52 formed of a stepped portion, and a fulcrum hole 53 is provided in the center.

Further, an arm 54 is provided on a part of the press plate 51 and protrudes outside the arm 2. Furthermore, as shown in FIG. 5, a positioning plate 55 having spring properties and having a plurality of sawtooth-shaped steps is fixed to the side surface of the pressing plate 51 facing the presser foot lifting lever 49 with screws or the like. The presser foot lifting lever 49 and the pressing plate 51 are overlapped in the direction shown in FIG.
The fulcrum hole 53 of the arm 2 is attached to the inner wall of the arm 2 by a stepped screw 22 via a washer 56 of an appropriate thickness.

At this time, the positioning protrusion 50 provided on the presser foot lifting lever 49 is aligned with the stepped portion of the positioning plate 55 provided on the pressing plate 51. To explain the adjustment of the press plate 51, first
arm 54 is rotated to set a predetermined rotational position of the press plate 51 with respect to the presser foot lifting lever 49.

For example, if we consider the case where the press plate 51 is rotated counterclockwise by an angle (8) with respect to its standard position, in this case, as shown in FIG. 6, the actuation point of the pin 36 is (da). will be delayed by an amount corresponding to the angle of . That is, when the press plate 51 is in the standard position, when the presser bar 1 is lifted by knee operation and the presser foot lifting lever 49 is rotated by an angle (8) in the direction of arrow E in FIG. 6, the pin 36 is displaced. When the press plate 51 is at the adjusted position indicated by the broken line, the pin 36 is rotated until the presser foot lifting lever 49 rotates at an angle of (a + do).
will not be displaced. As explained above, according to the present invention, the upper thread adjusting device allows the relative position of the pressing plate 51 with respect to the presser foot lifting lever 49 to be arbitrarily selected.
The operating point of the needle thread adjuster when the presser foot 5 is raised can be changed depending on the application, so even when sewing is performed with the presser foot 5 slightly raised, sewing can be performed in the same manner as under standard conditions. can do.

Particularly in this invention, the presser foot lifting lever 49 and the pressing plate 51 are rotatably connected through their mutual fulcrum holes 19 and 53, and the positioning plate 55 has a stepped portion centered around the fulcrum holes 19 and 53. Since this is done by engaging the protrusion 50 on the presser foot lifting lever 49, the change in the operating point of the upper thread adjuster with respect to the rise of the presser foot bar 1 is performed simply by the protrusion 50 of the presser foot lifting lever 49 and the stepped portion of the positioning plate 55 on the press plate 51. The engagement can be effected by simply moving the arm 54 against the spring force of the positioning plate 55, and it can be easily operated from outside the arm 2 without requiring a jig.

[Brief explanation of the drawing]

1 and 2 are an end view and a perspective view of a main part of a sewing machine head showing a conventional presser foot lifting mechanism and upper thread adjuster;
FIG. 3 is a structural diagram showing details of the presser foot lifting lever. FIG. 4 is an exploded perspective view showing the presser foot lifting lever and pressing plate which are the main parts of this invention, FIG. 5 is a perspective view showing the relationship between the pressing plate and the positioning plate, and FIG. 6 is an upper thread according to the invention. It is an explanatory view showing the adjustment situation at the time of operation of the regulator. In the figure, 1 is the presser bar, 7 is the presser bar, 15 and 49 are the presser foot lifting levers, 35 is the knee operation plate, 36 is the pin, 44 is the tension plate, 5 is the positioning protrusion, 51 is the press plate, and 54 is the arm. , 55 is a positioning plate. Figure 1 Figure 6 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. In a sewing machine that operates an upper thread adjuster to reduce the tension of the upper thread when the presser foot is released from the sewing material, a presser bar connected to the presser foot and slidably provided; a presser foot lifting lever that is engaged with the presser foot of the presser bar and rotates when the operating body is operated to raise the presser foot; a pressing surface that operates the pin of the needle thread adjuster by rotation of the presser foot lifter lever; a protrusion formed on the surface of the presser foot lifting lever facing the pressing plate; a positioning plate provided on the surface of the pressing plate facing the presser foot lifting lever and having a plurality of steps; A presser foot lifting device for a sewing machine, wherein the point at which the upper thread adjuster is activated by raising the presser bar can be adjusted by changing the rotational engagement position of the stepped portion with the protrusion. 2. The presser foot lifting device for a sewing machine according to claim 1, wherein the operating body is a knee operating plate.