Drawing instrument

DETAILED DESCRIPTION This invention is directed toward a manually operable drawing instrument which can be used to draw arches and ellipses quickly, easily and with great accuracy.
To this end, two bottom disposed pins extend vertically downward from a block supporting the bottom end of a vertical post.
These pins can engage a horizontal sheet of paper supported on a suitable horizontal surface.
The post passes through the center of the central opening in an annular circular disc.
Manually adjustable means removably secures the disc to the post and enables the angle between the plane of the disc and the axis of the post to be set at any value between -X and X, where X as expressed in degrees can range between 0 and somewhat less than 180.
A first elongated vertical member has a central section in the form of a semicircle with horizontally elongated upper and lower hollow tracks at corresponding upper and lower ends of this section which extend in the same direction and are coplanar with this section.
The post passes through the ends and tracks with clearance whereby the member can be rotated around the post and moved vertically up and down along the post.
A second vertically elongated member has a straight vertical central section provided with a guide mechanism engagable with and disengagable from the periphery of the disc.
The second member has parallel horizontal upper and lower rails at corresponding upper and lower ends of the straight section, each of the rails slidably engaging a corresponding one of the tracks and being horizontally movable in the corresponding tracks.
Marker means slidably engages the lower rail is securably thereto.
When the disc is in place, the post is held in position and the two members are squeezed together and rotated about the post, the guide mechanism engaging the disc periphery.
If the disc is horizontal, a circle is drawn on the paper.
If the disc is inclined, an ellipse is drawn.
Since the members can move together up or down, radially and horizontally with respect to the post, irregularities in the paper surface cannot adversely influence the accuracy of the drawing