GB737719A - Improvements in devices for testing the hardness of materials - Google Patents

Abstract

737,719. Testing hardness of materials. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 23, 1954 [June 8, 1953], No. 15740/53. Class 106 (2). A device for testing the hardness of timber &c. of the kind in which a penetrator is driven by blows of equal strength to a given depth in the material, the number of blows being a measure of the hardness, has means to prevent further blows being struck when the depth is reached. The penetrator, comprising a series of spikes 11, is placed against the material and the barrel 1 of the device pressed inwardly against a spring 8 contained between a hammer 4 and end closure 7. A plunger 6, moving with the barrel, passes down a bore 5 in the hammer to engage a transversely slidable locking element 17 to bring a bore 19 in it, into alignment with the bore 5. This permits the hammer 4 to slide along a shaft 9 integral with the penetrator, under the influence of the spring 8 and deliver a blow on a collar 13 to drive the penetrator into the material. The barrel is then returned to the position shown by a spring 14 and the element 17 is impelled by a spring 20 into the locking position. The penetrator carries an axially slidable stop 23 to which is secured a collar 26, and as the spikes penetrate deeper so the collar 26 approaches the barrel and restricts its forward travel. When the desired penetration has been achieved the barrel's travel is so restricted that the plunger 6 is unable to release the element 17 and the hammer remains ineffective. Adjustments are obtained by fitting members 23 of various lengths and arranging washers 27 behind the head 6b of the plunger 6.