GB566379A - Improvements in or connected with testing machines - Google Patents

Abstract

566,379. Testing physical qualities of materials. AVERY, Ltd., W. & T., and BOWEN, E. Jan. 7, 1943, No. 294. [Class 106 (ii)] In a testing machine primarily intended for fabrics, the load is applied to the specimen automatically by fluid-pressure means at a constant rate irrespective of the rate of extension of the specimen. The specimen c is stretched between a lower cross-head e and an upper cross-head d connected to a known load-resisting mechanism (e.g. a pendulum or springs) and to a load indicator a. The lower cross-head is joined to a piston g in a hydraulic cylinder h connected to a manually-controlled reversing valve fed with fluid from a pump m driven by a constant-speed motor n, Fig. 4, through a change-speed gear o. A relief valve l on the outlet side of the pump m controls the constant rate of loading and to this end the pressure on the valve l is applied by springs q connected to a yoke r moved on rods s by a screw t driven by gearing u from the changespeed gear o. Each revolution of the shaft t occurs in a constant time determined by the setting of the speed-gear o and increases the relieving pressure of the valve l, and hence the load on the specimen, by a given amount. The gearing u can be disconnected by a hand lever v and the yoke r then returns by gravity, assisted by a coiled spring t<2>, to relieve pressure on the valve l. In a modification, Fig. 5, the rate of increase of loading may be finely varied within the major variations produced by the settings of the change-speed gear. The relief valve l is controlled by an additional spring 6 acting on a lever l<1> and stressed by a lever 7 pivoted at 7a and rocked by the yoke r which is operated as described with reference to Fig. 4. The position of the fulcrum 2b of the lever l<1>, and thus the effect of the spring 6 and consequently the rate of increase of the fluid pressure, is determined by the position of a lever 2 set by a screw 3.