Compass for use at large-area blackboard, has three-armed base supporting magnets, which hold base at blackboard with magnetic force, where one of magnets on surface supports thin layer made of flexible elastic material

摘要

The compass has a three-armed base that is supported at one of its two legs, where the compass is set on a large-area blackboard with the base. The base supports magnets, which hold the base at the blackboard with the magnetic force. One of the magnets on a surface supports a thin layer (8) made of a flexible elastic material. The thin layer consists of a cup-like elastic body that includes a bulge at an edge of the elastic body. The magnets have a nut at side surfaces of the magnets, where the bulge is engaged in the nut.