| 摘要 |
A drawing instrument capable of drawing circles and ellipses on a working surface, said drawing instrument having a depending stationary arm and a depending revolving ami mounted on a shell, said shell having a mid point that is aligned with a longitudinal vertical axis of the drawing instrument, the revolving arm joined by a pin to the shell from the mid-point of the shell, the shell is rotate able, secured and centered over a thrust bearing wherein a top end of the stationary arm and a top end of the revolving arm scribe a circle or ellipse in an imaginary plane above and parallel to the working surface and which is transferred by the remote end of the revolving arm to the working plane to draw a circle or ellipse, said circle or ellipse drawn on the working surface is proportional to the circle or ellipse formed by movement of the top end of the stationary arm and top end of the revolving arm.
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