GB476399A - Improvements in or relating to mechanical testing machines - Google Patents

Abstract

476,399. Testing physical qualities of materials. LEAN, R. J., and QUINNEY, H. Aug. 8, 1936, No. 21892. Addition to 448,130. [Class 106 (ii)] The parent invention in which a spring stressed to an extent more than necessary to fracture a specimen is connected to one end of the latter, the other end being relatively fixed, and the spring released by the amplitude of vibration of the spring after fracture of the specimen being recorded, is provided with a modified construction of recording- mechanism. A spring 24 carries a movable holder 41. A second holder 42 is secured to a resilient member 200 rigidly attached to a frame member 22. The spring 24 is deflected upwards by means as in the parent Specification and a test piece 69 is inserted into the holders. Trip means are operated to release the spring and the specimen is subjected to a sudden stress which is transmitted through the specimen to the resilient member 200. The strain in the member 200 and the corresponding movement of spring 24 are recorded. Holders. The ball 64 is clamped to one end of the test piece 69 by a plug 73 and washer 210 being located axially by a conical point 68. It is then introduced into a cup 60 through an opening 211 and a reinforcing ring 212 brought down and screwed home. A milled head 214 and rubber washer 216 prevent rebound when the specimen breaks. The lower holder which.is similar and screws into a support 47 may be adjusted to accommodate different length specimens. Side walls 48 and ledges 49 on the support 47, together with screw pillars 219, 220, serve to clamp the holder of the spring 24. The C-shaped member 200 is secured by bolts 222 and a conical spindle 224 to the frame 22. The upper holder 42 is screwed into the member 200. Recording. The upper ends of pillars 219, 220 are pressed against rollers 227 carried on the spring 200 by rollers 228 supported from the frame 22 by resilient arms 229. A drum 231 to which a sheet of celluloid is clamped is mounted as roller bearings on the lower end of spindle 224. Each side of the lower part of spring 220 has secured to it a plate spring 236 carrying a diamond point bearing on the celluloid strip and when spring is deflected a line is traced proportional to stress. At the same time when the spring 24 is deflected a roller 240 carried by pillars 219 and engaged by a spring-pressed cam plate 238 on the drum rotates it an amount proportional to the sum of the deflection of spring 200, and the extension of the specimen. Since the strain in spring 220 is marked on the strip for each degree of movement of spring 24, the actual extension can be calculated. In a modification, the drum is mounted on the lower limb of spring 220 and the diamond point carried by the fixed part. This gives the extension of the test piece directly.