Patent GB-712701-A (GB)
Title: Improved compression plastometer
IPC: G01N3/14
Filed: 1951-10-03
Abstract: 712,701. Testing physical qualities of materials. WALLACE & CO.. Ltd., H. W., and MORE, A. R. Oct. 3, 1952 [Oct. 3, 1951 No. 23012/51. Class 106 (2) An apparatus for applying compression tests to material such as rubber, comprises two opposed and heated platens 27 and 5, arranged to initially compress the sample of rubber to the required thickness for testing by moving the first platen 27 in relation to the second platen 5 while the latter is fixed in relation to the frame 10 of the apparatus, and to then test the sample by the movement of the second platen 5 in relation to the first platen 27 while the latter is fixed in relation to the frame of the apparatus. As shown, the upper platen is carried by a beam 26 that can be raised against the action of springs 33 to admit a test sample between the platens. The beam 26 is raised through the medium of two rods 31 actuated by a handle 36. The lower platen 5 is supported by a vertically displaceable table 6 subjected to an upward thrust equal to the required compressive test thrust by a spring 8. During the periods that this upward thrust is not required it is cancelled out by a second spring 16 acting downwardly on an armature 17 connected to the lower platen 5 by a rod 14. Above the armature 17 is an electromagnet 18 which, when energized, attracts the armature 17 in a manner cancelling out the effect of the spring 16 on the lower plates 5 which is then subjected to the full upward thrust of the spring 8. The platens 27 and 5 may be heated by steam passing through the tubes 69 and 70 or by any other means. Operation.-By suitably actuating the handle 36 the beam 26 is raised so that a test sample may be inserted between the platens 27 and 5. The beam 26 is then lowered through the medium of the handle 36 until the upper platen 27 has been moved sufficiently to cause the sample to be compressed to the required thickness for testing purposes. As soon as the beam 26 is lowered a dial-gauge 58 is set to zero and a clock--like controlling mechanism is started automatically. This clock-like mechanism may allow 10 seconds to elapse before it automatically energizes the electromagnet 18 to remove the opposing load of the spring 16 from the main spring 8, thereby allowing the lower platen 5 to rise under the full pressure of the spring 8 against the sample being tested. The maximum deformation of the sample under the loading of the spring 8 is registered on the dial-gauge 58 after the clocklike controlling mechanism has de-energized the electromagnet 18 to conclude the test. Dial gauge.-The dial gauge 58 is of the maximum reading type having a number of balls 61 which are situated within a conical hollow member 59 concentric with the needle 60 and engaging a conical projection on the latter whereby when the needle 60 is moved upwards with the lower platen 5 during a test, the needle 60 is retained in its most elevated position by the wedging action of the balls 61. A reset device 62 is fitted which frees the needle 60 by lifting the balls 61 when the beam 26 is lifted to insert a fresh test specimen between the platens 27 and 5.