Patent GB-793409-A (GB)
Title: Improvements in or relating to the checking of the dimensions of articles
IPC: B64D45/00
Filed: 1956-06-27
Abstract: 793,409. Linear-dimension air gauges. OPEL AKT.-GES., A. June 27, 1956 [July 26, 1955], No. 19883/56. Class 106 (2). An apparatus for checking the dimensions of an article 26, comprises a conduit 15 having an inlet 14 for the admission of air at a constant pressure and an outlet 27, 28 in a mandrel 24 from which the air can be directed against the article; a liquid column pressure indicator 38 connected to the conduit 15 between its inlet and outlet; and a device 33, which upon a fall in pressure in the conduit 15 to a predetermined value, operates to restrict the flow of air therethrough. An airline 12 is connected to a supply of compressed air to admit air under constant pressure through an exchangeable restrictor 14 forming the inlet of the conduit 15. This constant pressure corresponds to the head of water in a container 10 above the open end 13 of a vertical air tube 11. The outlet of the conduit 15 is formed by two jets 27, 28 of the detachable gauge mandrel 24, which has guide portions 29 to facilitate insertion into the article 26. On the indicator 38 are a pair of pointers 42, 43, which can be adjusted so that they correspond to the limits of the dimension to be checked. Sections 17, 18 of the conduit are in parallel and contain respectively a valve 19 operated by a relay 30 and a shutter 20 with a small hole in it. A tube 35 connects the conduit 15 to a pressure responsive switch 33 having a diaphragm 34 which acts to open or close contacts 36, 37 in a circuit 31 including the relay 30. The distance between the contacts 36, 37 is adjusted before use, so that they close when the pressure in conduit 15 rises above a value somewhat less than that corresponding to the maximum permissible value of the dimension and are opened when pressure falls below that value. This value corresponds to the level Y of the liquid column in the tube 39 of the indicator 38. In operation. The mandrel 24 is inserted into the article 26 and air flows through the conduit 15 and the open valve 19 contacts 36, 37 being closed. The meniscus then assumes a position corresponding to the dimension being measured and the article can be accepted or rejected according to this value. When the article is disengaged from the mandrel, air escapes freely and so the pressure in conduit 15 begins to fall, the diaphragm 34 rises, and the contacts 36, 37 open, thus closing the valve 19. Air can then only flow through the small hole in the shutter 20, so the pressure in conduit 15 falls no further and the meniscus stays at level Y. When next measuring an article, the escape from the jets 27, 28 becomes impeded and so the pressure in conduit 15 rises and moves the diaphragm 34 downwards to close the switch 33, thus opening the valve 19. The meniscus then takes up the position which corresponds to the article now under test and does so quickly since it has only a shoft distance to traverse. Since only a small part of the tube 39 is wetted, the errors arising from the retention of water on the surface above the meniscus will be very small. In a modification the valve 19 can be of a type which is operated by the relay 30 not for complete closure but to leave a small hole, thus dispensing with section 18.