GB754445A - Improvements relating to drawing apparatus - Google Patents

Abstract

754,445. Draughting-machines. ROFF, P. J. (Lehsten, S.). Jan. 26, 1955 [Jan. 26, 1954], No. 2261/54. Class 97 (3). Drawing apparatus comprises a supporting frame including an elongated frame member extending from top to bottom of a drawing board and having at one end a wheeled carriage which travels along a straight guide rail itself secured to an edge of the drawing board, a vertical guide rail secured to said carriage so as to be permanently at right-angles to the path of travel of the carriage and a scale-carrying member slidably mounted upon the vertical guide rail, the scale carrying member having mounted thereon a protractor head and means for attaching linear scales thereto. A hollow member 10, extending slightly obliquely across a drawing-board, is fixed at its end to a large bracket 11 and a smaller bracket 12. Bracket 11 carries grooved rollers 16 which engage a horizontal guide-rail 17 fixed at the top of the drawing board. The bracket 12 has an extension 13 carrying a roller 14 which slides along the bottom of the drawing board or an extension thereof. Brackets 11 and 12 are joined by a vertical guide-rail 18 of oval section which extends at right angles to the direction of movement of the bracket 11. A carriage 19 mounted on rail 18 has cylindrical rollers 20 engaging the underside of rail 17, and a friction brake 31 whereby the assembly can be locked in any position along the horizontal guide rail 17. A scale carrying member 32 has grooved rollers 33 engaging the vertical rail 18. A flat plate 37 is pivoted at 39 to plate 32, and is also pivoted at 41 to a link 40 which is connected to an eccentric 43 mounted on a plate 32, so that the plate 37 can be adjusted. A knob 51 is journalled in plate 37 and carries the arms 47, 48 carrying the scales, which can be set in positions differing by 15 per cent by means of a notch plate (not shown) engaged by a pawl. The scales may be held in intermediate position by a friction brake operating when the pawl is held out of engagement. Plate 32 is normally locked in position along the rail 18 by a friction brake which may be released by operation of lever 36. A cord 62 is connected to plate 32 through a spring 65, passes over pulleys 63 mounted in housings 64 on the bracket 11, and then passes to a counterweight 61 sliding in the tube 10.