Improvements in Appliances for Drawing, Setting Out, Testing and Measuring Circular and other Arcs.

摘要

27,884. Cruse, G. H. I. Dec. 18. Arc - describing instruments; ellipsographs and other instruments for drawing curves; determining radii of curves; curve gauges.-Relates to appliances of the kind in which a flexible strip of elastic material is bent to a circular or other arc for use as a templet, or as a gauge. The flexible strip A, Fig. 1, of uniform width and thickness, for drawing circular arcs, is provided with four studs a1, a2, a3, a' connected by pin-joints to two pairs of equal links B, C, which are similarly connected at their other ends to collars D, E, respectively. The collar E has an internal screw-thread and is engaged by a screw F, and the collar Dismounted loosely on a cylindrical shank G at the end of the screw F and is retained in position by a collar H. By turning a milled head J, the collar E is moved away from the collar D, and the part a2, a3 of the strip is bent into a circular arc. A scale of radii may be fixed to the stationary collar, and may be read off against the other collar, or against a pointer attached to the centre of the strip. In order to obtain non - circular curves, strips of uniform thickness but of varying width are employed. The rod F may be screw-threaded for a part of its length only and may engage with an internally-threaded sleeve, to which the collar E may be clamped at any desired point. In the modification shown in Figs. 9 and 10, the screw F is of quick pitch, and is fixed to the collar E so that it cannot revolve. The collar D fits into a recess in a bush 0, which is internally threaded to receive the screw F, and is provided with a milled head J for setting the instrument to the required curve. On the bush 0 is fitted an adjustable sleeve P having a helical line Q engraved thereon corresponding to the pitch line of the screw F. The line Q is graduated, and forms a scale to be read in conjunction with a pointer L fixed to the collar E. The ends of the strip A may be set back as shown in Fig. 9, so as not to interfere with the use of the instrument as a gauge for measuring the inside curvature of concave bodies. The strip A may be detachable, so that it may be replaced by strips of different shapes.