GB816322A - A device for producing perspective drawings - Google Patents

Abstract

816,322. Perspective drawing apparatus. JACKSON, W. H. Feb. 23, 1956 [Nov. 23, 1954], No. 33913/54. Class 97(3) Apparatus for producing on a sheet placed on a drawing board BB a perspective of a diagram placed on the board comprises three straight rods FCOR, TCOR, FR pivoted at 4, 5, 5a and having pivotal interconnection, at 1, 2, 3, provided by members which may slide on or be clamped to the rods, the joint 2 carrying a follower which is taken over the diagram, the joint 1 carrying a marker for drawing the perspective while the joint 3 is constrained to move along a straight line, as by sliding along a rod TR. The normally fixed points 4, 5, 5a are adjustable along a rod CR. In a modification, Fig. 1, the pivot 5a (Fig. 6) of the rod FR is, in effect, displaced to infinity the rod FR being coupled to a device, such as a drafting machine, which maintains the rod parallel to itself while it moves so that the pivot 3 always moves along a straight line. In the form of this modification shown the follower is not attached directly to the joint 2 but to a member FF coupled thereto by a distance rod DCR. A preliminary construction is made using a plan of the object, the line representing the picture plane being drawn thereon together with the plan of the station point and lines through the station point in the directions of elevation planes, which lines intersect the picture plane in the vanishing points. Each elevation plane is considered to be rotated about its vanishing point until it coincides with the picture plane, the position then occupied by the station point, which lies on the horizon line HH, is the "measuring point" Mb and is represented by the joint 4. The "trace" tb, represented by the path of the joint 3, is the intersection of the picture plane and the plane of the object represented by the diagram. The vanishing point Vb is represented by the joint 5 in the form shown in Fig. 1 while, in Fig. 6, it is represented by the intersection with the line HH of the line drawn from the point 5 through the foot To of the perpendicular from the point 5a on to the line tb.