Sewing machine presser foot

Abstract

In a sewing machine presser foot device that uses air pressure from an air cylinder to press the presser foot, the aim is to improve the appearance of the sewing machine. [Solution] The presser foot device 5 of a sewing machine comprises an arm 2 forming the upper part of the sewing machine frame 1, a head 3 positioned on the left side of the arm 2, a side cover 4 positioned on the left side of the head 3, a presser bar 6 pivotally supported by the side cover 4 so as to be vertically movable, a presser base 7 positioned below the head 3 with its upper part in contact with the presser bar 6, and a presser foot 8 attached to the tip of the presser base 7. The presser foot device 5 further comprises a presser crank 9 positioned above the presser bar 6 and having an L-shape with one end in contact with the upper end of the presser bar 6, an air cylinder 11 positioned at the rear of the head 3 with a cylinder rod 11a in contact with the other end of the presser crank 9, and a regulator connected to the air cylinder 11.

Description

Technical Field

[0001] The present invention relates to a presser device for a sewing machine, and more particularly to a presser device for a sewing machine that presses a fabric by the air pressure of an air cylinder. In the present invention, "front and rear" refers to the front and rear directions in the fabric feeding direction, "left and right" refers to the left and right directions when the sewing machine is viewed from the front, and "up and down" refers to the up and down directions of the sewing machine.

Background Art

[0002] As a conventional presser device for a sewing machine, a configuration in which an electro-pneumatic regulator is connected to an air cylinder is known (see, for example, Patent Document 1). A presser foot is fixed to the lower end of a presser bar, and a telescopic rod of an air cylinder is connected to the upper end. The upper part of the presser bar is arranged inside a head (sewing machine head). The air cylinder is connected to a compressed air source, and an electro-pneumatic regulator as a pressure regulating means is interposed midway. When the presser foot rises, the telescopic rod of the air cylinder is contracted and the air pressure inside the air cylinder tends to rise, but the air pressure is kept constant by the action of the electro-pneumatic regulator. As a result, the force with which the presser foot presses the fabric becomes constant, and the fabric can be smoothly fed even when, for example, a stepped portion of the fabric passes under the presser foot.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, the air cylinder is directly connected to the presser bar. However, when applying the conventional technology to an overlock sewing machine, the air cylinder will be arranged protruding above the head, which deteriorates the appearance.

[0005] The present invention aims to provide a sewing machine presser foot device that is aesthetically pleasing even when using an air cylinder. [Means for solving the problem]

[0006] To achieve the above objective, the invention described in claim 1 is a presser foot device for a sewing machine comprising: an arm forming the upper part of a sewing machine frame; a head disposed on the left side of the arm; a side cover disposed on the left side of the head; a presser bar pivotally supported on the side cover so as to be vertically movable; a presser base disposed below the head, the upper part of which abuts against the presser bar; and a presser foot attached to the tip of the presser base, wherein the device further comprises: a presser crank located above the presser bar and having an L-shape, with one end abutting against the upper end of the presser bar; an air cylinder located at the rear of the head, the cylinder rod of which abuts against the other end of the presser crank; and a regulator connected to the air cylinder.

[0007] The invention described in claim 2 is characterized in that the retaining crank comprises a corner portion, a retaining rod connecting portion including one end, and an air cylinder connecting portion including the other end, the corner portion is supported by a crankshaft so as to be rotatable around an axis, and the air cylinder connecting portion is longer than the retaining rod connecting portion.

[0008] The invention described in claim 3 is characterized in that the presser foot device of the sewing machine has an air cylinder attached to the rear of the side cover via a bracket. [Effects of the Invention]

[0009] According to the present invention, since the air cylinder and the retaining rod are connected via an L-shaped retaining crank, the air cylinder can be positioned at the rear or back of the head, resulting in an improved appearance. [Brief explanation of the drawing]

[0010] [Figure 1] Perspective view of a sewing machine equipped with the presser foot device according to the present invention, viewed from the front left. [Figure 2] Perspective view of a sewing machine equipped with the presser foot device according to the present invention, viewed from the left rear. [Figure 3] Left side view of a sewing machine equipped with a presser foot device according to the present invention [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to Figures 1 to 3. Figure 1 is a perspective view of a sewing machine equipped with the presser foot device according to the present invention, viewed from the front left; Figure 2 is a perspective view of a sewing machine equipped with the presser foot device according to the present invention, viewed from the rear left; and Figure 3 is a left side view of a sewing machine equipped with the presser foot device according to the present invention.

[0012] The sewing machine shown in Figure 1 is an overlock sewing machine, with an arm 2 and a head 3 formed on the upper part of the sewing machine frame 1. The head 3 is located on the left side of the arm 2. A side cover 4 is attached to the left side of the head 3. The presser foot device 5 comprises a presser bar 6, a presser foot base 7, a presser foot 8, a presser crank 9, an air cylinder 11, a cylinder rod 11a, and an electro-pneumatic regulator (not shown). The presser bar 6 is pivotally supported on the left side of the side cover 4 so as to be able to move up and down in the axial direction. The upper end of the presser bar 6 is exposed to the outside at the middle of the side cover 4. The presser foot base 7 is located below the head 3 and is rotatably connected around a presser foot base shaft 12 located behind the arm 2. The presser foot 8 is attached to the tip of the presser foot base 7 and is located above the needle plate 14.

[0013] The retaining crank 9 is located above the retaining rod 6. The retaining crank 9 has an L-shape and is formed by a retaining rod connecting portion 9a including one end, the corner portion 9c, and an air cylinder connecting portion 9b including the other end. The retaining crank 9 is supported axially by the crankshaft 10 at the corner portion 9c. One end of the retaining crank 9 abuts against the upper end of the retaining rod 6. The upper end of the retaining rod 6 has an arc shape when viewed from the left. The cylinder rod 11a of the air cylinder 11 abuts against the other end of the retaining crank 9.

[0014] The air cylinder 11 is located at the rear of the head 3 and is attached to the rear of the side cover 4 via a bracket 13. The air cylinder 11 is connected to a compressed air source (not shown) and also to an electro-pneumatic regulator (not shown). This ensures that the air pressure inside the air cylinder 11 is kept constant at a value set by the electro-pneumatic regulator.

[0015] When sewing fabric, the fabric is placed between the presser foot 8 and the needle plate 14, and the fabric is transported in the fabric feeding direction F by the feed dogs 15 that extend and retract from the grooves of the needle plate 14 while sewing. At this time, the air pressure from the air cylinder 11 is transmitted to the presser foot 8 via the cylinder rod 11a, presser foot crank 9, and presser bar 6, causing the presser foot 8 to bias the fabric downwards.

[0016] With the presser foot device 5 configured as described above, when the feed dog 15 protrudes from the upper surface of the needle plate 14, the presser foot 8 is lifted upward, which compresses the cylinder rod 11a and attempts to increase the air pressure inside the air cylinder 11. However, as mentioned above, the air pressure is kept constant by the electro-pneumatic regulator, so the presser foot 8 is biased downward, and the force pressing the fabric, i.e., the presser pressure, is kept constant. Similarly, even when the thickness of the fabric changes during sewing, such as when sewing over a stepped section, the presser pressure is kept constant, so the fabric is fed smoothly even over stepped sections, leading to improved sewing quality.

[0017] Furthermore, as shown in Figure 3, the length of the air cylinder connecting portion 9b of the retaining crank 9 is greater than the length of the retaining rod connecting portion 9a, so that the retaining rod 6 can be pressed by the air pressure in the relatively small air cylinder 11. This allows for the use of a relatively small air cylinder, resulting in a more compact and aesthetically pleasing design. In addition, the main components of the retaining device 5 are located on the left side of the side cover 4, i.e., outside the head 3, so they are not affected by the lubricating oil filling the head 3. This prevents malfunctions caused by the adhesion of lubricating oil.

[0018] According to the presser device of the sewing machine described above, since the air cylinder and the presser bar are connected via an L-shaped presser crank and the air cylinder is arranged at the rear or the back of the head, the appearance looks better.

[0019] The present invention is not limited to the embodiments described above. Those skilled in the art can make various modifications to the above embodiments without departing from the spirit of the present invention and implement them. The present invention also includes those modified forms. In addition, although an overlock sewing machine is used in this embodiment, it is not limited thereto. For example, it can also be implemented on a sewing machine equipped with a presser mechanism similar to an overlock sewing machine.

Explanation of Reference Numerals

[0020] 1 Sewing machine frame 2 Arm 3 Head 4 Side cover 5 Presser device 6 Presser bar 7 Presser base 8 Presser weight 9 Presser crank 9a Presser bar connecting portion 9b Air cylinder connecting portion 9c Corner portion 10 Crank shaft 11 Air cylinder 11a Cylinder rod 12 Presser base shaft 13 Bracket 14 Needle plate 15 Feed teeth F Fabric feed direction

Claims

1. A presser foot device for a sewing machine comprising: an arm forming the upper part of a sewing machine frame; a head positioned on the left side of the arm; a side cover positioned on the left side of the head; a presser bar pivotally supported by the side cover so as to be vertically movable; a presser base positioned below the head, the upper part of which abuts against the presser bar; and a presser foot attached to the tip of the presser base, wherein the presser foot device further comprises: a presser crank positioned above the presser bar and having an L-shape, with one end abutting against the upper end of the presser bar; an air cylinder positioned at the rear of the head, with its cylinder rod abutting against the other end of the presser crank; and a regulator connected to the air cylinder.

2. The presser foot device for a sewing machine according to claim 1, characterized in that the presser foot crank comprises a corner portion, a presser foot rod connecting portion including one end, and an air cylinder connecting portion including the other end, the corner portion is supported by a crankshaft so as to be rotatable around an axis, and the air cylinder connecting portion is longer than the presser foot rod connecting portion.

3. The presser foot device for a sewing machine according to claim 1, characterized in that an air cylinder is attached to the rear of the side cover via a bracket.

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