Drawing apparatus for perspective views

Claim 2

A drawing apparatus for perspective drawing comprising: a straight edge support assembly means for supporting a straight edge and for allowing said straight edge to be moved in first and second orthogonal directions; a head shaft rotatably mounted in said straight edge support assembly means; a head arm mounted on the lower end of said head shaft; an elongated arm holder mounted on said head shaft; an elongated angle arm rotatably mounted on said elongated arm holder at a pivot pin spaced from said head shaft along said elongated arm holder; a linking mechanism for interconnecting said head arm and said angle arm so as to rotate these members together and maintain them in a parallel relationship; a straight edge base pivotally mounted on said head arm and said angle arm, said base also being longitudinally movable to various positions along said angle arm; a horizontal straight edge fixedly mounted on said straight edge base along which straight perspective lines may be drawn.

Claim 3

A drawing apparatus as claimed in claim 1 wherein said straight edge support assembly means includes first and second orthogonally situated bar means, said straight edge being movable along said first bar in a first orthogonal direction and said first bar being movable along said second bar in a second orthogonal direction.

Claim 4

A drawing apparatus for perspective drawings as claimed in claim 1 wherein: a head grip is attached at the upper end of said head shaft for allowing said shaft to be manually rotated; said elongated arm holder is rotatably mounted on said head shaft; is further included an arm-holder locking means for selectively locking and unlocking said arm holder against and for rotation relative to said head support; is further included a head-arm locking means for selectively locking and unlocking said head arm and said arm holder against and for relative rotation.

Claim 5

A drawing apparatus as claimed in claim 1 wherein: said horizontal straight edge is provided with longitudinally oriented graduation indicia for displacement which has thereon a series of marks M and a single standard mark B; said angle arm is provided with longitudinally spaced graduation indicia which has thereon a series of angle marks theta , said angle marks theta displaying the position of said base along said angle arm, and each of said marks M on said horizontal straight edge corresponds to an angle mark theta on said angle arm; a vertical straight edge mounted on said base perpendicular to said horizontal straight edge, and defining a vertical line which intersects said horizontal straight edge at said standard mark B; wherein, when said drawing apparatus is set to draw a first range of perspective lines about a first base line, which is a straight line passing through the axes of said head shaft and said pivot pin, perspective lines, defined by said horizontal straight edge, intersect said base line at a vanishing point V, a particular angle mark theta is indicated along said angle arm, corresponding to a particular mark M along said horizontal straight edge, and a point A is the intersection of said vertical line and said perspective line when said head arm and said angle arm are in a position at which the base line coincides with the horizontal straight edge, it is desired to move the elongated arm holder to a second base line position at which a second range of perspective lines can be drawn having the same vanishing point V as said first range of perspective lines, said elongated arm holder is rotated so that said new base line corresponds to said particular perspective line and said point M on said horizontal straight edge corresponds to said point A on said perspective line.

Claim 6

A drawing apparatus as claimed in claim 4 wherein the marks M are set with respect to the standard mark B on the horizontal straight edge so that a relation ''''VA VM'''' and ''''BM VA'''' (1 -cos theta ) may be established where VA is a distance between the vanishing point V and the point A, and VM is a distance between the vanishing point V and the point M, and BM is a distance between the point B and the point M, and theta in the angle of the straight edge with respect to the first base line when the head arm and the angle arm are at 90* to the elongated arm holder.