GB752154A - A drafting device - Google Patents

Abstract

752,154. Draughting machines. ZUC. CHINI, C. June 16, 1954 [June 16, 1953], No. 17635/54. Class 97 (3). In a draughting machine a protractor carrying member capable of movement in two mutually perpendicular directions is adjustable on and along a support bar attached to a carriage slidably mounted on a guide bar fixed parallel to the upper edge of a draughting table, the support bar being perpendicular to the guide bar so that it can sweep over the draughting table as the carriage is adjusted along the fixed bar and the protractor may be placed in any position on the table. As shown, a draughting machine includes a fixed horizontal guide bar 1, Fig. 1, fitted by means of brackets 2 at the top edge of a draughting table T slightly behind the plane of the table, a carriage 4 running on spring-loaded rollers on bar 1 and carrying a C-shaped arm, extending slightly in front of the plane of the table, which arm supports a vertical guide-bar 5 for a protractor mounting carriage 6 slidable on spring-loaded rollers and an oblique slide bar 7 for a counter-weight 11 connected to the carriage 6 by a cable system, and a bracket 8 connecting bars 5, 7 at their lower ends and having at least one wheel running along the bottom margin of the table. Either or both carriages may have releasable means for clamping them to their respective guide bars. The carriage 6 has an extension 6<SP>1</SP> to which is secured a plate 28 on which is mounted a protractor base-plate 30 with arms 30<SP>1</SP>, 30<SP>11</SP> carrying scales 31<SP>1</SP>, 31<SP>11</SP>. The base-plate 30 is rotatable on plate 28 by means of a knob 29, Fig. 8, housing a sliding pin 36. When a knob 35 on the pin is pressed, the pin slides against spring action and, through a pivoted lever, rocks a pawl 33 out of engagement with a notch 32 on the plate 28. The protractor is then turned and, as knob 35 is released pawl 33 engages another of the notches 32, which are disposed at fixed angles round the periphery of plate 28. A pin 46 may be pressed against spring action to engage a hole 48 in pin 36 which is then retained in position to hold pawl 33 out of engagement with the notches, so that the protractor can turn freely.