GB970309A - Improvements in or relating to an apparatus for measuring hardness - Google Patents

Abstract

970,309. Hardness impact testing. A. ERNST. Nov. 9, 1961 [Nov. 9, 1960; Oct. 11, 1961], No. 40203/61. Heading G1S. In hardness-testing apparatus giving pre-load and main load of a penetrating member 1 in a single operating movement, the holder 2 for the tip 1 has a resilient portion 29<SP>1</SP> at its widened upper end for frictional engagement with a slider 3 integral with washers 17, 18 (to limit movement of the slider in co-operation with locking rings 19, 20) and a feeler 4 The latter bears against a disc 5 on a diaphragm 6 closing a fluid chamber communicating with a capillary indicating tube 9. The diaphragm-fluid chamber assembly (5-15) rests on a cylindrical body 23 narrowed at 24 and terminating in hood 44. Initially, the whole apparatus is held in the fully-raised position by spring 31, resting on a ring 25 engaged with the base 26, and acting on the casing 30. A pin 49 secured to a part 48 carried by pillars 56 extending (through suitable apertures) from ring 25, bears against the part 29 of the holder 2 to cause the tip 1 to protrude beyond hood 44 by a predetermined amount. As casing 30 (and thereby -the whole apparatus) is lowered using handles 46, the tip 1 engages the surface of the work-piece under a driving pressure due solely, in the first instance, to the frictional force on the part 29<SP>1</SP> as the slider 3 moves downwards. During this initial movement, the feeler 4 (and slider 3) rests on a cross-piece 16 supported on a sleeve 35. When hood 44 makes contact with the surface, the cylindrical body 23 is arrested and with it the diaphragm-fluid chamber assembly. Deflection of the diaphragm 6 is then maintained only by the frictional force between the part 29<SP>1</SP> and slider 3 since cross-piece 16 now falls with further lowering of the casing 30 and sleeve 35. Screws 36 in the latter constrain upwardly a second cylindrical body 37 having a cross-piece 40 against spring 38. After casing 30 has been lowered sufficiently, the cross-piece 40 will engage pin 41, which is rigid with the holder 2, to subject tip 1 to the full pressure of spring 38 as the screws 36 break engagement with the upper edges of the apertures in the cylindrical body 37. As holder 2 descends with further penetration of the tip 1 under' the increased load, the part 29<SP>1</SP> will take with it, by friction, the slider 3 to give a decreased deflection of the diaphragm observable in the capillary tube 9. In a modification of the apparatus, the feeler 4 is in the form of a ball, slider 3 is elongated to give a large bearing surface, and friction is provided by a clip the pressure of which is adjustable.