JP3866260B2 - Ruler to draw a circle - Google Patents

Description

  The present invention relates to a ruler for drawing a circle.

  Conventional techniques for drawing a circle include a compass, a template, and a ruler. The compass can be drawn quickly and accurately by adjusting the compass to the length of the circle, shifting the center position when drawing the circle, or shifting the lines drawn as the paper floats up. was difficult. It was also dangerous because it was equipped with a needle. There were no templates with the size of the desired circle, or it was difficult to align the center of the circle. On the other hand, a ruler that draws a circle has a large number of small holes at different distances from the center of the disk that is rotatably held by the outer frame, and the core of a writing instrument such as a mechanical pencil is inserted into these small holes to rotate the disk While drawing a circle (see Patent Document 1, Patent Document 2, and Patent Document 4), there is a problem that the disk does not rotate smoothly. In particular, it does not rotate at all when drawing a very small circle compared to the size of the disk.

  There are already various technologies to solve this problem. For example, a combination of a ruler and a template such that one outer frame is provided with two large and small disks (see Patent Document 5), a large circle is drawn with a ruler, and a small circle is drawn with a template (Patent Document 3). , Patent Document 6 and Patent Document 7), and ball bearings provided to reduce contact resistance with the outer frame (see Patent Document 3 and Patent Document 7). However, these techniques cannot fundamentally solve the problem that the disk does not rotate smoothly.

Jito No. 3054958

An object of the present invention is to fundamentally solve the problem that a disk does not rotate smoothly in a conventional ruler for drawing a circle. In a conventional ruler for drawing a circle, the fundamental reason why the disk does not rotate smoothly is that a rotation axis is not provided at the center of the disk, and the center position of rotation is not fixed when the disk is rotated. If the center position of rotation is not fixed, the moment of force does not work, and the force applied to rotate the disk does not become rotational force. Even when the center position of rotation of the disk is not fixed as in a conventional ruler for drawing a circle, the disk rotates relatively smoothly if the size of the disk and the size of the circle to be drawn are substantially equal. This is because the vector direction of the force applied to rotate the disk and the vector direction of the force that rotates the disk, that is, the tangential direction of the outer periphery of the disk substantially coincide. However, if the size of the circle to be drawn is very small compared to the size of the disk, the direction of the force applied to rotate the disk and the tangential direction of the outer circumference of the disk will be significantly different. Power is not born and it will not rotate. That is, as the size of the circle to be drawn becomes smaller than the size of the disc, the vector direction of the force applied to rotate the disc and the vector direction of the rotational force gradually move away.

  Even when drawing a very small circle compared to the size of the disk, a rotation axis is provided at the center of the disk so that the disk rotates smoothly, and the position of the rotation axis is fixed when drawing a circle. So that the moment of force works. On top of that, a structure that reduces the contact resistance between the disk and the outer frame as much as possible was adopted.

By making the disk rotate smoothly, circles with various radii from large circles to very small circles can be drawn easily, quickly and accurately. This eliminates the need for a compass or template.

Hereinafter, embodiments of the present invention will be described based on examples with reference to FIGS. In FIG. 1, this ruler has a number of small holes at different distances from the center of the disk 1, inserts a core of a writing instrument such as a mechanical pencil into these small holes, and draws a circle on the paper while rotating the disk 1. is there. This disk 1 has a rotating shaft 2 at its center, and has the same shape as a top. The disk 1 is rotatably held at its outer periphery by an outer frame 3 and a paper presser 4. The outer frame 3 is cut out so that the peripheral side surface has a truncated cone shape, and is placed so as to cover the disk 1 from above. Therefore, in this ruler, when the circle is drawn on a paper surface and the outer frame 3 is pressed by hand from above, the tip of the rotary shaft 2 presses the paper surface with a pinpoint, and the center position of rotation is fixed. It has a structure.

Since the outer frame 3 is cut out so that the peripheral side surface has a truncated cone shape, the contact between the outer frame 3 and the disk 1 is a line contact, and the contact resistance when the disk 1 is rotated is more than the surface contact. It is running low.

In FIG. 2, when the outer frame 3 is held by hand from above, the tip of the rotary shaft 2 can securely press the paper surface with a pinpoint. It is necessary to set the length of a so that it cannot be drawn. Incidentally, the length of a is preferably about 0.5 mm.

In FIG. 2, if the gap between the disk 1 and the upper surface of the paper presser 4 is made too large, the disk 1 will be displaced from side to side or inclined with respect to the paper surface when the outer frame is pressed by hand from above. Not only is it difficult to fix the position, but the distance between the disk 1 and the paper surface increases, making it difficult to draw an accurate circle. Therefore, this gap is desirably about 0.1 mm to 0.5 mm.

  As shown in FIG. 3, by making the rotating body 5 polygonal, the contact between the outer frame 3 and the rotating body 5 can be a point contact, so that the contact resistance when rotating is compared to the line contact. It gets smaller and starts to rotate smoothly. Further, as shown in FIG. 4, although the strength is weakened, the contact between the outer frame 3 and the rotating body 6 can be made point contact by making the rotating body 6 into a star shape.

  The material of this ruler is preferably a transparent plastic or the like in order to make it easy to determine the center position of the circle to be drawn, or to make it easy to check whether or not the circle has been drawn accurately.

The top view which shows the Example of this invention, and AA sectional drawing Partial enlarged view of AA cross-sectional view of FIG. Plan view of another embodiment Plan view of another embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc 2 The rotating shaft provided in the center of the disk 1 3 Outer frame 4 Paper holder 5 Polygon rotating body 6 Star-shaped rotating body a The length which protrudes from the bottom face position of the paper holder 4 in the rotating shaft 2

Claims (3)

A rotating body such as a disk that is rotatably held by an outer frame is provided with a large number of small holes at different distances from the center of the rotating body, and the core of a writing instrument such as a mechanical pencil is inserted into these small holes. In a ruler that draws a circle on the paper surface while rotating the rotation axis, a rotation shaft is provided at the center of a rotating body such as a disk, and when this ruler is placed on the paper surface and pressed by hand from above, the tip of the rotation shaft will push the paper surface. A ruler that draws a circle characterized by the fact that the center of pressing rotation is fixed and a moment of force is applied when this rotating body is rotated. The plate cut out so that the peripheral side surface has the shape of a truncated cone is used as an outer frame, and the diameter of the cut-out truncated cone is intermediate between the diameter of the upper surface and the diameter of the bottom surface. The diameter of a rotating body such as a disk is determined, and the outer frame is placed on the rotating body such as a disk provided with the rotating shaft according to claim 1, the center of the shape of the truncated cone and the rotating body such as the disk The circle according to claim 1, wherein when the outer frame is placed so as to coincide with the center and the outer frame is pressed by hand from above, the tip of the rotation shaft presses the paper surface to fix the center position of rotation. ruler. A ruler for drawing a circle according to claim 1, wherein the rotating body is a polygon or a star, and the contact between the polygon or the star-shaped rotating body and the outer frame according to claim 2 is a point contact.

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