GB636381A - Improvements in or relating to draughtsmen's trammels - Google Patents

Abstract

636,381. Curve- - drawing instruments. McCARTHY, A. April 28, 1948, No. 11651. [Class 97 (iii)] The holder 11, Fig. 1, for the marking element 14 of a trammel is of channel form slidably and non-rotatably mounted on the beam 10 and is provided with limbs 12, Fig. 2, having lateral projections to one side of the beam, in which are formed dove-tailed shape gaps 13 in register with each other to receive an ordinary wood pencil 14 passed endwise through the gaps. A wide W-shaped spring 15 fitted within the holder channel and having curved-back extremities 17 holds the pencil in place and also retains the holder in its set position. To enable a drawing pen or needle or lead to be used as the marking element a secondary holder may be provided consisting of a short metal bar of cross-sectional shape to provide surfaces for seating flat on the con. verging edges of the gap 13 and having a longitudinal bore at one end to receive the shank of a pen lead or needle as a push fit. The bar may be recessed to receive the central saddle portion of the blade-spring 15. The beam 10, Fig. 5, may be provided with a transverse bore 21 at one end into which the fixed needle 27 slidably passes, screw clamping means, preferably comprising a draw bolt 24 having a head 23 passing freely into a longitudinal bore 25 in the beam and having a transverse bore 22 in its head aligned with the bore 21 in the beam together with a clamping nut 26, being provided to hold the needle in the required position. The beam 10 may be socketed at its other end to receive extension pieces provided with spigots.