GB846035A - Fluid-pressure operated materials testing machine - Google Patents

Abstract

846,035. Fluid-pressure servomotor control systems. MASCHINENFABRIK AUSBURGNURNBERG A.G. Dec. 6, 1957 [Dec. 11, 1956], No. 38042/57. Class 135. The ram cylinder 2, of a materials-testing machine, is supplied with pressure air or liquid by a variable-delivery pump 8; the cylinder pressure is transmitted to a gauge 30 having a pointer 32 which indicates pressure, the latter being a measure of the load applied to a testpiece 4; the gauge is also provided with an arm 34 adjustably coupled to the pointer 32 so that it may be disposed at any desired angle with respect thereto. Movement of the arm 34 is transmitted to a pivoted jet 16 by a slipcoupling comprising magnets 35, 36 and a lever 37; the jet 16, which is supplied with air or liquid by a pump 14, has its deflection limited by stops 19, 20 whilst the jet nozzle 16a terminates adjacent channels 26, 27 separated by a deflector 29 and leading to opposite sides of a piston 10 which controls the delivery of the pump 8. To maintain a given pressure in cylinder 2 the pointer 32, arm 34 and lever 37 are relatively adjusted so that pointer 32 indicates the desired pressure, magnets 35, 36 are in alignment and jet 16 is symmetrically located with respect to the ends of channels 26, 27. Any deviation from the set pressure will cause a deflection of members 32, 34 and 16 to cause the piston 10 to appropriately adjust the output of pump 8 to restore the given pressure. When a given pressure is exceeded in the cylinder 2 the movement of the arm 34 is not transmitted by magnets 35, 36 to lever 37. In order to vary the pressure in cylinder 2 at a given rate of change the angle between the pointer 32 and arm 34 is varied at the corresponding rate by a motor, not shown. In a modification, the gauge 30 is rotated by a motor at any given speed; the pointer 32 is connected to a pressure-responsive capsule. If it is desired to control the machine in dependence upon the deformation of the testpiece 4 then arm 34 is mounted upon the testpiece. The machine may also be controlled in dependence upon the force to which the testpiece 4 is subjected in which case the arm 34 is disposed on a ring-member 3 located between the test-piece 4 and ram piston 1. Where testpiece deformation and the force in member 3 are controlling characteristics, means, not shown, is provided for converting linear movement into rotary motion of the pointer. In these circumstances the machine is disposed in a stand with the test-piece bearing on one cross-head and the ring 3 on the other. The gauge casing is preferably made of aluminium which separates the two magnets 35, 36 so that arm 34 does not project from the casing. The gauge is constructed as a plug-in instrument so that it may be used in quick succession to detect any of the above-mentioned signals.