Geometrical instruments – Area integrators – Electrical
Patent
1986-07-07
1988-03-22
Haroian, Harry N.
Geometrical instruments
Area integrators
Electrical
33170, G01B 346
Patent
active
047319321
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a measuring system for preparing working gauges with a measurement precision of 1 .mu.m.
A working gauge, also called a master, is an e.g. block shaped body, which is machined to show a desired exact distance between two surface areas, whereby it is usable as a comparison gauge in connection with high precision working of various production parts. When the gauge has a correct measurement, it will be sufficient to carry out a comparative measuring of the production part, e.g. with the use of a stand having a sufficiently accurate dial gauge. Often it is necessary, e.g. during a day of production, to carry out several measurings of the gauge for a steady checking up of the other measuring equipment, and this implies a certain wear of the gauge, even if it is made of hard steel. Therefore, all according to the frequency of use and other conditions of use, the gauge block should be checked up from time to time by an exact and absolute measuring, which requires an expensive measuring apparatus. In large enterprises having such an apparatus, e.g. a three-coordinate measuring machine, there are often queues before the respective measuring departments, and the single measurings are time-consuming.
If or when the absolute measurement of a gauge has changed, the gauge may still be fully usable, at least by small deviations, when it is marked--preferably by engraving--with an indication of its deviation from its nominal measurement, e.g. "-4 .mu.m". In use it is hereby possible to effect the required corrections by an exact dial gauge or a similar device which, without being too costly, can accurately measure inside a narrow measuring range of e.g. 10 mm, while the total measuring range employed may be up to some 20-50 cm. It has been found, however, that the users nevertheless sometimes forget to carry out the required corrections, and as well known this may give rise to an expensive waste or to serious machinery break downs later on.
Instead of spending time on preparing a master gauge with associated absolute control measurings during the preparation thereof, it may be chosen to assemble a master gauge from standard calibrated gauge blocks, which should need no control measuring. However, these blocks are quite expensive, and it has been found that the blocks are not as accurate as commonly believed. In this connection, the heat from manual handling of a short duration may be sufficient to cause a change of several .mu.ms, and moreover even these blocks will be worn if they are used as practical measuring implements and not only as adjustment standards in protected surroundings in specialized laboratories, so-called measuring rooms. Worn blocks may well be calibrated, but only at very high costs and with a long waiting time, since the production and the calibration of gauge blocks is a specialty practiced by only very few manufacurers.
In this connection, it should be mentioned that accurate length measurement standards for industrial use are found almost exclusively as the gauge blocks, which may be placed together to form any measurement of addition under controlled circumstances, e.g. by a room temperature of 20.degree. C. Otherwise the users have to provide their own gauges or masters based on the use of accurate measuring instruments, which should of course also work under controlled conditions. The standard blocks are provided with entirely smooth and exactly plan parallel surfaces which by disposing the blocks together may cause the blocks to stick together already by the associated complete displacement of air.
From a measuring technical point of view, it is very important that the opposed surfaces are really completely plan parallel, as a measurement difference of e.g. one half of one thousandth of a millimeter between the opposite ends of the blocks might increase by the laying together of five-six blocks. Also, the possible high accuracy of inexpensive short distance measuring instruments such as dial gauges and micrometer screws normally is
REFERENCES:
patent: 495019 (1893-04-01), Carter et al.
patent: 2345591 (1944-04-01), Frederick
patent: 4219934 (1980-09-01), Davitt
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