Geometrical instruments – Distance measuring – Opposed contacts
Patent
1987-05-14
1989-04-18
Martin, Jr., William D.
Geometrical instruments
Distance measuring
Opposed contacts
33813, 33784, G01B 512
Patent
active
048214213
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a micrometer with digital readout including a body containing measuring components and carrying means for displaying the results of the measurements, this body being equipped with a head arranged to receive a measuring piece adapted for the measurement of either the outer dimensions of a surface, or of the inner dimensions of a cavity or a bore, or of depths.
Known micrometers of this type generally include a series of measuring pieces each corresponding to a determined range of dimensions and each associated with a reference ring. These devices are usually without a device for mechanical zero setting and for that reason do not in general allow a direct measurement of parts to be effected, but only allow an indirect measurement with reference to the corresponding reference rings. The real dimension of the parts is only accessible by display of the reference value. A calculation, in general an addition, consisting in adding the dimension of the reference ring to the value displayed on the display device of the micrometer allows the measurement to be determined. This operation complicates the measurement or at least renders it less easy and may, in certain cases, constitute a source of errors.
SUMMARY OF THE INVENTION
It is proposed in the present invention to meet these drawbacks by making a micrometer with numerical display as previously mentioned which permits to directly obtain, by numerical display, the real value of the dimensions of an object to be measured. A certain number of concepts, which constitute the principal features of the present invention, have been adopted to permit effecting extremely precise measurements, of the order of a micron and rendering these measurements particularly easy and indefinitely repeatable.
To this end, the micrometer according to the invention is characterized in that it includes means allowing the measurements to be effected in natural size and to display a value corresponding to the real dimension of the measured object.
According to a preferred embodiment, said means comprise a surface plate serving as a reference surface designed to constitute a fixed support for a measuring piece adapted to a fixing head solid with the body of the apparatus, this surface plate comprising two series of serrations respectively parallel to two mutually perpendicular diameters.
According to a particularly advantageous embodiment, said means comprise a fastening device of the bayonet type for fastening a measuring piece to the fixing head. This mode of fastening necessitates a rotary displacement of the measuring piece on the surface plate, which allows the elimination of dust susceptible to vitiate the measurements.
To allow zero setting of the device before each measurement, said means preferably comprise a calibrating stop solid with a mobile piston, this piston being adapted to push back a drive rod of the measuring feelers of a measuring piece, and a reference stop, these two stops being positioned in such a manner that they determine with great precision the origin of any displacement of the piston.
According to a particularly advantageous embodiment, the distance between the surface plate and the reference stop is defined with a precision of the order of 1 micron.
In order to permit a direct reading of the measured values, each measuring piece includes a drive rod having an end which is adapted to come into contact with a bearing stop solid with the free end of the piston and is positioned at a determined distance from the calibrating stop, when the measuring piece is in place on the surface plate, this distance being defined for each measuring piece in such a manner that the displacement effected by the piston from its initial position defined by its calibrating stop to its final position corresponds exactly to the dimension to be measured.
The reference stop is preferably mobile and consists of a pin sliding in a fixed sleeve carrying a control button adapted to bring this pin into a depressed position in which
REFERENCES:
patent: 2561534 (1951-07-01), Parker et al.
patent: 3222790 (1965-12-01), Meyer
patent: 3226833 (1966-01-01), Lemelson
patent: 4335516 (1982-06-01), Edelstein
patent: 4385446 (1983-05-01), Roch et al.
patent: 4536963 (1985-08-01), Yamamoto et al.
Girardier Jean-Pierre
Girardier Raymond
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