GB779513A - Improvements in and relating to parallel guiding contrivances particularly for drafting devices - Google Patents

Abstract

779,513. Mathematical drawing appliances. KRISTIANSEN, S H. Sept. 6, 1955, No. 25533/55. Class 97(3) A device for ensuring parallel motion of a member, particularly a drafting machine, over a plane surface, comprising at least two freely rotatable balls mounted in the device so as to roll on the surface and two interconnected rotatable rollers engaging the balls to cause them to rotate with equal peripheral velocities. Thus, Fig. 9 is a plan view' of a drawing polygon 42 supported on three balls 122, 123, 124 the lower periphery of each of which projects through a hole in the polygon, while the upper part is supported in an inverted cup 50 containing ball-bearings 56. A shaft 132 in bearings 58 carries rollers 128, 130 in frictional engagement with the balls. A similar shaft 232 carries rollers 228, 230 the latter of which also engages the ball 124, the balls 123, 124 being further engaged by rollers 328, 330 on a shaft 332. Movement of the device may be limited to one direction by the application of a brake 74 or 76 which bears on a disc 70 or 72. Such movement is indicated on one of the graduated discs 66 co-operating with indices 68. In simpler embodiments two balls are used and are engaged either by a single roller between them at different axial positions thereof, or by a single, pair of separate rollers on a common shaft. In Fig. 15 the three balls are disposed at the vertices of an equilateral triangle and driving interconnection is provided by pairs of rollers 528, 530 on shafts 532. There may also be a further central ball in frictional engagement with the other three and disposed either with its centre at the same height as that of the others or, being larger than the others, above them as shown at 586. Thus it may be mounted on an inverted-cup 550, with ball bearings 556, vertically adjustable by a screw 594 carried by legs 592. The central ball then provides the vertical location for the other three. In a slightly different embodiment shown in section in Fig. 16 each ball 622 engages the ends of two rollers 632 in ball bearings 658 and is located vertically by a ball 614 carried by ball bearings 656 in a housing formed partly on a member 610 and partly in a member 650. An enclosing housing 620 is rotatable on a bearing 602. Movement of the device may be arrested by a brake 674 brought into engagement with the drawing surface by depressing a spring loaded plunger 675.