GB662997A - Improvements in or relating to devices for drawing ellipses - Google Patents

Abstract

662,997. Ellipsographs. MOLLART ENGINEERING CO., Ltd., and HARRIS, S. E. Feb. 8, 1950 [May 30, 1949], No. 14471/49. Class 97 (iii). An ellipsograph comprises a plate-like guidemember having a pair of grooves which meet as a T and are engaged, respectively, by projections upon a drawing arm, the transverse groove being wider but shallower than the groove forming the stem of the T and the projections on the drawing arm being of corresponding shape and size to slide snugly, each within its particular groove. As shown in Fig. 1, the guide-member 10 consists of a plate of polished transparent plastic having tongue portions each provided with a pair of grooves such as 19, 20 in T-form, the tongues being of varying width to enable different-sized ellipses to be drawn. The groove 20 is of the full depth of the plate thus forming a slot, the groove 19 being less deep but wider. The groove 20 stops short of the further wall of the transverse groove 19. The plate is provided on the under-side with two needle-pointed pegs 25 whereby it is secured to the paper. The centre lines 21, 22 of the grooves 19, 20 are marked on the bottom of the member 10; alternatively when the member is non-transparent notches may be provided centrally at the ends of the grooves for alignment of the member with the axes of the required ellipse, Fig. 6 (not shown). The drawing arm comprises a strip 31 of transparent plastic having a slot 32 the lower edges of which are cut away to form rebates 33. Secured at adjustable positions along the slot 32 by nuts 41 are two projection members 34, 35, Fig. 3, each comprising a circular flange 36 fitting slidably in the rebate 33, the under-surface of the flange being substantially flush with the under-surface of the drawing-arm; the members have eccentric cylindrical projections 42, 43, respectively, these being of different diameter and depth to fit slidably in their respective grooves 19, 20. The end of the strip 31 carries the drawing or scribing device 12. The strip is preferably flexible transversely to the paper.