Compasses

The utility model provides a compasses, belongs to the teaching aid. The set pattern body and the cross section that moves the rule body are the semi -circle, move rule body top and are equipped with and observe the hole, move the internal portion of rule and are equipped with the pivot, and the connecting axle of pivot bottom is equipped with driven gear, and driven gear meshes with the driving gear mutually, and the driving gear is connected with the motor output shaft, moves the internal pencil that is equipped with of rule, and the pencil top is equipped with presses the handle, presses the handle and is located the slide rail, and the outside cover of pivot has around the chi dish, is connected with flexible chi one end around the chi dish, and the flexible chi other end and the body coupling of establishing rules, it is equipped with fixed needle to establish rules internal, fixes the needle top and is connected with the link, and the link top is connected with the pressure handle. The utility model discloses when not using, will establish rules the body with move the rule bodies place be in the same place into one cylindrical, when need using, the motor is rotatory, can launch flexible chi around the chi dish, draws to the length of wanting, make fixed needle downstream will establish rules the body to fix according to pushing down the handle, then moving the rule body, to carry out the drawing round. Conveniently carry, bring a lot of convenience for the user.