CN2848590Y - Three leg compass - Google Patents

Abstract

The utility model relates to a three legs compass, including a supporting bar and a large rotary bar, and the external edge of the large rotary bar is provided with a retractable small rotary bar. In use, when the user wants to draw a circle, he/she makes the pencil head part of the small rotary bar separate from the picture surface, and only makes the pencil head of the large rotary bar contact with the picture surface; when the user wants to draw a ring form, he/she makes the pencil heads of the small rotary bar and the large rotary bar contact with the picture surface, and thus when drawing, the large rotary bar and small rotary bar can draw a circle simultaneously, and as a result, the user can draw a ring form once. The utility model is provided with time saving and labour saving, and it can not generate error, and it is propitious to teachers teaching and students learning.

Description

Three point compass

Technical field the utility model relates to a kind of realia, especially a kind of Three point compass.

The mathematics class that technical background is present; teachers and students use compasses through regular meeting; but when the drawing circular pattern; common compasses will be drawn twice; so just lose time; if and round dot is looked for the inaccurate quality that will influence drawing, the so just compasses appearance of a kind of circular pattern that can once can draw of needs.

The summary of the invention the purpose of this utility model provides a kind of Three point compass, is used to solve the problem that common compasses can't be drawn two circles simultaneously.

For achieving the above object, the utility model Three point compass comprises support bar and big swingle, establishes a telescopic little swingle in the outside of big swingle.

After adopting said structure, when using compasses to draw annular,, two swingles are all contacted with paper, so just do not need picture twice telescopic little swingle elongation, time saving and energy saving, and also very accurate.

The utility model has the advantages that: simple in structure, easy to use, time saving and energy saving, and accurately, can not cause error.

Description of drawings Fig. 1 is the overall structure schematic diagram of the utility model Three point compass.

The specific embodiment as shown in Figure 1, the utility model Triangle compasses comprises support bar (1) and big swingle (2), establishes a telescopic little swingle (3) in the outside of big swingle (2).Wherein support bar (1) and big swingle (2), little swingle (3) are on same plane, and the pen head part of little swingle (3) so just can have telescopicing performance for being threaded.In use, when the user thinks that picture is circular, can inwardly tighten the threaded connection place of little swingle (3), its nib is not contacted with drawing, only allow the nib of big swingle (2) contact with drawing; When the user thinks the picture annular, can be outwards loosening the threaded connection place of little swingle (3), with till drawing contacts, and big swingle (2) remains unchanged up to nib, like this in picture, big swingle (2) and little swingle (3) rotate simultaneously, two the different circles of drawing, user's annular of just can once drawing not only saves time but also laborsaving like this, and can not produce error, help teachers ' teaching and student study.

Claims (1)

1, a kind of Three point compass comprises support bar (1) and big swingle (2), and it is characterized in that: a telescopic little swingle (3) is established in the outside at big swingle (2).