Patent GB-878625-A (GB)
Title: Improvements in or relating to apparatus for making orthographic projection drawings
IPC: B43L13/00
Filed: 1958-12-15
Abstract: 878,625. Surface and outline gauges. SPALEK, A. T. Dec. 15, 1958 [Jan. 27, 1958], No. 40440/58. Class 106 (2). [Also in Groups XV and XX] An apparatus for making orthographic projection drawings from a solid object 110, Fig. 1, and which may be used to check the dimensions of the object against drawings, comprises a drawing surface 38, a marking device 40 mounted for two-dimensional travel over the surface, a feeler 108 adapted to contact the object 110 and movable in three dimensions, and coupling means for moving the marking device in one of its dimensions of travel on the drawing surface 38 in response to movement of the feeler in a direction perpendicular to the drawing surface. The feeler 108 and pen 40 are carried by a horizontal T-frame, with a longitudinal member 30 and a transverse member 32, travelling on rails 34, 36 on opposite sides of the drawing table 38 and carrying a rigid superstructure 58 supporting an overhead horizontal rail 62 above the table 38 and which projects forwardly beyond the frame member 30. A carriage 64 on the rail 62 supports a vertical rod 54 counterweighted at 70 and passing freely through a housing 53 fixed to a slide 50 movable in the transverse direction on the frame member 32. The rod 54 carries at its lower end the feeler 108, and the pen 40 is adapted to be operated intermittently by an electromagnet to produce a series of spaced dots which are afterwards joined up to give the projection drawing. To make a plan view of the object 110, the point 108 of the feeler is traversed over the desired horizontal contour of the object and the pen 40 is fixedly mounted on the slide 50 so as to move longitudinally with the frame 30, 32 and transversely with the slide 50, but be unaffected by any vertical travel of the feeler, the apparatus acting as an ordinary pantograph. To draw a side elevation or a longitudinal section of the object, the pen is removed from the slide 50, so as to be unaffected by any transverse movement of the feeler, and fixed to a slide carriage 122, Fig. 10, movable on a rail 122 fixed parallel to the transverse frame member 32 of the horizontal T-frame 30, 32. A rack 124 fixed to the carriage 122 is driven by gearing 123 from a shaft 99 having a gear-wheel 100, Fig. 7, within the housing 53 meshing with a rack 102 on the vertical rod 54 carrying the feeler. Vertical movement of the feeler is thus turned through 90 degrees and results in hori-, zontal transverse movement of the pen. Longitudinal motion of the feeler is also transmitted to the pen since it is carried on the frame member 32. To draw an end elevation or a cross-sectional view, the frame member 30 is clamped to the rail 34 to prevent any longitudinal movement and the pen 40 is fixed to a rack..140, Fig. 15, slidable through a bracket 114 fixed to the slide 50 and movable in a direction at right angles to the frame member 32. The rack 140 is driven by a gear-wheel 142 on the shaft 99, so that vertical movements of the feeler result in horizontal longitudinal movements of the pen, which also follows the transverse movements of the feeler through the slide 50. Feelers of goose-neck shape may be used to reach reversely curved portions of the object. In a modification, instead of removing the pen and replacing it on a different member of the apparatus to obtain the various views the pen is permanently mounted on a member which can be selectively driven through racks and pinions by the members 30, 32, 50 as required. Datum lines may be drawn by suitably setting the apparatus and keeping the pen continuously operated. Marking device.-A ball-point pen 150, Fig. 10, is mounted on a solenoid plunger 152 which normally holds the pen in its retracted position away from the paper. The plunger is rounded at its upper end and has a loose eccentric weight 154 so that it tilts when the solenoid is deenergized and the ball end slides down an inclined annular bore 162 of a base member 156 with a small central hole just above the paper. The bore is roughened so that the ball of the pen rolls during its downward travel and exposes a freshly inked surface which immediately afterwards strikes the paper.