Apparatus and method for checking mechanical parts

Details Apparatus and method for checking mechanical parts Apparatus and method for checking mechanical parts

1990-07-24

1992-02-18

Cuchlinski, Jr., William A.

Geometrical instruments

Gauge

With support for gauged article

335551, 33557, 33520, G01B 525, G01B 728, G01B 731

Patent

active

050882066

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to an apparatus for checking geometrical features of mechanical parts with symmetry of rotation and having two centre seats, with first supporting means for supporting the part to be checked, by cooperating with it at positions different from said seats; second supporting means; gauging means fixed to the second supporting means and adapted to cooperate with the part; and processing means connected with the gauging means for determining said geometrical features.
The invention also relates to a method, for checking the concentricity of cross-sections of a part having symmetry of rotation and featuring at its ends centre seats, according to which centres of said cross-sections are automatically determined by electronically processing the signals of gauging heads for measuring linear dimensions, a reference geometrical axis is electronically defined and the distances of said centres from the reference geometrical axis are determined.


BACKGROUND ART

It is known to check, statically or dynamically (i.e. with the part being stationary or in rotation), the concentricity of different cross-sections of mechanical parts with symmetry of rotation, in particular shafts, with reference to a geometrical axis defined by a totally mechanical manner.
The geometrical axis is normally defined by two precision centres (with relevant support devices) that cooperate with the corresponding seats obtained at the ends of the shaft for permitting support and rotation of the latter during the subsequent machining phases (turning, grinding, etc.). One of the centres can be motorized, for performing dynamical checkings.
In several cases, from a theoretical point of view it is more correct to take as a reference the geometrical axis defined by the centre seats, but it is difficult and expensive to make high precision centres and relevant support devices, for preventing displacements of said geometrical axis with respect to the gauging devices or heads that perform dimensional measurements in correspondence with the different cross-sections of the shaft.
Therefore, in other cases the checking is performed by taking as a reference a geometrical axis defined as the axis passing through the centres of two cross-sections of the part. For example, for a crankshaft, the reference axis can be determined by processing the signals of two gauging heads each of which has two feelers in contact with a respective journal for determining two radial dimensions of the journal along the same diametral direction.
The signals of these gauging heads are combined with those of further gauging heads that check other radial dimensions of the part. The part can be supported by Vee supporting devices or also by low precision centres, since possible spatial displacements of the axis of instantaneous rotation of the part are electronically compensated.
However, as already mentioned, sometimes the measurement problems require to take as a reference the axis defined by the seats for the supporting centres, in particular for inter-operational checkings of the machining process.


DISCLOSURE OF INVENTION

Object of the invention is to permit checking of geometrical features, such as concentricity, of parts with symmetry of rotation, e.g. shafts, with reference to a geometrical axis defined by the relevant centre seats, while guaranteeing high repeatability and accuracy, without any need of supporting the part by high precision centres and relevant supports.
The invention as characterized in the claims solves the problem of determining in an electronic way the position of the geometrical axis of a part with symmetry of rotation as defined by the relevant centre seats, while the part is supported by supporting devices different from the centres.
Since the position of the axis defined by the centre seats is readily and continuously determined, possible displacements of the same axis can be compensated. Therefore the part can be supported and rotated by low precision devices. It is possible to detect displacements of said axis a

REFERENCES:
patent: 3795055 (1974-03-01), Zucco
patent: 3869800 (1975-03-01), Bartlett et al.
patent: 4594757 (1986-06-01), Johnson, Jr.
patent: 4601109 (1986-07-01), Klingler et al.
patent: 4674193 (1987-06-01), Wertepny et al.
patent: 4914827 (1990-04-01), Cook
A. Taniguchi, Patent Abstracts of Japan, vol. 7, No. 35 (P-175) [1180], 2/10/83.
Y. Koyama, Patent Abstracts of Japan, vol. 10, No. 300 (P-506) [2356], 10/14/86.

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