Patent GB-827940-A (GB)
Title: Improvements in or relating to program control of hydraulically operated endurance testing machines
IPC: G01N3/36
Filed: 1957-12-06
Abstract: 827,940. Testing physical qualities of materials. AMSLER, W. A. J., AMSLER, R. C., PEYER-AMSLER, H. E., SCHINDLERAMSLER, G. M., and LABHART-AMSLER, S. B., [trading as AMSLER & CO., A. J.]. Dec. 6, 1957 [Dec. 7, 1956], No. 37982/57. Class 106 (2). Programme control apparatus for an hydraulically operated endurance-testing machine 4 having a pulsator 1 with hydraulic stroke control means 2 comprises means 11, 26 furnishing two variable reference forces, means 9, 22 for comparing the reference forces with two instantaneous values corresponding to different phase positions of the periodically varying load produced by the pulsator 1, means for varying the instantaneous values to render them equal to the reference forces, counters 42 for counting the load changes and means 43 for adjusting the reference forces to predetermined values corresponding to a series of programme steps, i.e. sets of load changes. A pulsator 1 supplies pressure oil to the working cylinder 4 of the testing machine, the pressure changing in a sine wave manner. A distributer 5 transmits pressures corresponding to the mean load and peak load through conduits 8, 24 respectively, these pressures being indicated on manometers 6, 7. The means pressure is controlled in the following way. A pump 15 supplies pressure oil to a cylinder 13 and this moves a frame 14 up against a stop 18. This pump also supplies oil to a valve 9, the piston 10 of which is acted on by a tension spring 11, and, in the opposite direction, by the pressure of the oil in conduit 8. If the mean pressure is less than that desired, piston 10 rises, under the action of spring 11, and oil from pump 15 flows along conduit 8 through the distributer 5 and into the working cylinder 4. If the mean pressure is too high, piston 10 falls, under the action of the oil in conduit 8, and conduit 8 is connected to a discharge tube 20, thus lowering the pressure of the oil in cylinder 4. A slide valve 22 operates in a similar manner to adjust the stroke of the pulsator 1 and hence the amplitude of the pressure changes. In this case, oil in conduit 24 acts on piston 23 against the tension in spring 26 which is regulated by a frame 27 abutting a stop 32. The oil from pump 15 is then transmitted to one side of a piston 37, the position of which adjusts the stroke of the pulsator 1, and the other side of this piston is opened to a discharge tube 39 or 40. Each impulse of the pulsator 1 actuates one of a set of counters 42. When a predetermined number of impulses for one programme step has taken place, two control valves 16, 30 are operated by solenoids so that cylinders 13, 29 are connected to discharge tubes 47, 48, and frames 14, 27 are pulled downwardly by springs 11, 26. Motor 43 then rotates a pair of gears 19, 33, carrying the stops 18, 32, so that a different pair of stops can be used, so giving new mean and peak pressures. Operation of a second programme step then commences, valves 16, 30 being returned to their original positions and the impulses being switched to another counter 42. This sequence is then repeated for each of the counters. It is also possible to repeat the complete programme by switching back to the first step when a sequence of steps has been completed. The limit stops 18, 32 may be replaced by continuously moving cams. An alternative programme step is one in which stop 32 is set for zero load amplitude and control valve 16 is set to release the pressure in cylinder 13 when the frame 14 abuts stop 18 and to refill it when the frame abuts a further stop 44. In this way the load oscillates between predetermined maximum and minimum values.