GB482373A - Improvements in or relating to compression testing apparatus - Google Patents

Abstract

482,373. Testing physical qualities of materials. DUNLOP RUBBER CO., Ltd., SIMPSON, E., STUBBS, A. J., and NORCROSS, T. Aug. 28, 1936, No. 23600. [Class 106 (ii)] Apparatus for testing more especially cushions and cushioning materials such as sponge rubber under compression comprises means for submitting a test piece to a predetermined load, means for further compressing the test piece a predetermined proportion of its thickness under that load, and means for measuring the load at that degree of compression which is effected automatically irrespective of the different thickness or compressibility of different test pieces. The testing unit is carried by a sprocket chain 5 operated from a motor 7 and comprises a universally-mounted platen 9 above which is a weight 11. A dynamometer 12 from which the unit hangs is so calibrated that it reads zero when the whole weight of the unit is hanging freely from the chain 5. A test cushion 8 is placed on the platform 1 and the switch 3 moved down. This starts the motor and the unit is lowered the platen 9 engaging and compressing the cushion 8. When the dynamometer registers the initial load, two kilograms, a mercury contact is tilted by a cam on the spindle of the dynamometer. This contact controls a differential 13 comprising two pulleys 17, 18 the diameters of which are in the proportion of 4 to 6 both of which are carried by a spindle 19 mounted on a carriage 20 which rises and falls with the unit. The driver pulley 17 is encircled by a tape 21 one end of which is attached to the fixed framework and the other to the periphery of the pulley. As the unit moves up and down the driver 17 is caused to rotate. Encircling the selector pulley 18 is a tape 23 one end of which is fixed to the periphery of the selector and the other to a weight 24. When the switch actuated by the cam on the dynamometer spindle is tilted, an electromagnet within the differential is energized to clutch the selector 18 to driver 17. Thus as the unit lowers, the pulley 18 is rotated by the pulley 17 and pays out the tape 23 until the weight 24 carried by the latter engages a contact switch 25. This causes the displacement of a switch panel carrying a pair of mercury switches one of which makes a circuit of an electromagnet to stop the dynamometer pointer and hold the reading and also causes declutching of the pulleys. The other switch stops the motor. The switch handle 3 is then lifted to reverse the motor 7 and raise the unit for a fresh test. The spacing is effected by the contact weight always starting its independent or proportionally different movement from a position spaced away from the contact a distance equal to the thickness of the cushion under its initial compression.