Geometrical instruments – Gauge – Circular size
Reexamination Certificate
1999-03-23
2001-07-10
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
Circular size
C033S551000, C033SDIG001
Reexamination Certificate
active
06256898
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a workpiece-measuring apparatus, in particular for grinding machines and high-accuracy measurements.
DESCRIPTION OF THE PRIOR ART
It is known that workpieces on machine-tools, in particular grinding machines, can be advantageously measured and checked while machining is going on. This for the purpose of obtaining workpieces that do not require further dimensional checks and that are machined until achievement, as much as possible, of the intended optimal conditions. In this manner many machine shop rejections are avoided, as well as and above all further re-machining that in some cases is required for bringing workpieces machined in an inadequate manner or with insufficient accuracy to a precise size.
For measuring workpieces while they are being machined, typically workpieces having circular sections ground with abrasive grinding wheels, apparatuses are used that have as the active elements two arms emerging from a box-shaped casing generally sealingly closed, in which various members for control and operation of the arms and transducer elements responsive to the angular position of the arms are arranged.
Such arms are capable of oscillating around positions of substantial mutual parallelism and surround the workpieces from diametrically opposite regions, and feeler pins adjustable in position relative to the arms and put directly in contact with the workpieces are interposed therebetween.
Two fundamental positions are imposed to the arms through apparatuses disposed inside the casing. In the first position, the arms keep the feeler pins in contact with the workpieces: it is the work position and for accomplishment of same a set and steady “contact force” is required to be applied to the arms. The contact force is typically obtained by calibrated springs active on the arms from the inside of the casing.
In the second position the arms keep the feeler pins separated from the workpieces: it is the open or “reloading” position and for accomplishment of same a release force is required to be applied to the arms for moving them away from the workpiece, so as to promote positioning of the feeler pins before measurements.
The opening or “reloading” force is typically obtained by pneumatic or electromagnetic members placed within the casing, which act on the arms upon command, so as to move the feeler pins away from the workpieces.
The above described apparatuses have several drawbacks when high-accuracy measurements are to be carried out, i.e. capable of detecting even one-micron tenths in an exactly repeatable manner, and when the initial configuration of the apparatuses is varied.
In fact, springs generating the contact force make high-accuracy measurements of little reliability: actually, it is difficult to calibrate and adjust these springs with accuracy so that they may maintain a light and continuous action and that this action may be the same for all measurements to be carried out.
In addition, the action of the members applying the opening or “reloading” force creates small mechanical shocks reducing the exact-measurement repeatability.
In general all contacts between said arms and the different control and operation members are sources of inaccuracies due to variations in the contact conditions as a result of wear, heat, lubrication, deposit of dust or others.
It is also to point out that when the arms and/or feeler pins are partly changed for adapting them to the workpieces to be measured, the overall weight of the arms is varied, which results in a requirement of new adjustment of the springs generating the contact forces.
Each new adjustment involves opening of said casing, execution of precise operations, restoration of a sealed closure.
The work position of the measuring apparatus must then remain the same as the position set during the adjustment step: each mounting with a different lying relative to the provided one makes it necessary for the springs exerting the contact force to be calibrated again.
SUMMARY OF THE INVENTION
Under this situation, the technical task underlying the present invention is to devise a workpiece-measuring apparatus, in particular for grinding machines, capable of substantially obviating the above mentioned drawbacks.
Within the scope of this technical task, it is an important aim of the invention to devise an apparatus of great accuracy and reliability.
Another important aim of the invention is to devise an apparatus in which both the contact force and the opening force are applied in a rigorously repeatable manner and without generating extra stresses, contact regions varying in time or mechanical shocks.
It is a further aim of the invention to devise an apparatus enabling parts of the arms and/or feeler pins to be changed without operations for opening said casing in view of a new adjustment of the contact force being required.
It is a still further aim of the invention to devise an apparatus adapted to be positioned independently of the direction of action of the force of gravity.
The technical task mentioned and the aims specified are substantially achieved by a workpiece-measuring apparatus, in particular for grinding machines, comprising: two arms oscillatingly supported by fulcrums and having respective work portions, feelers on said work portions for contacting a workpiece, sensors for measuring oscillations of said arms about said fulcrums, and drive means for selectively exerting at least one contact force and at least one release force tending to rotate said work portions of said arms respectively towards and away from said workpiece, wherein said drive means comprise at least one magnet located adjacent to said arms and having opposite polarities, magnetic elements arranged on said arms and having active faces facing said at least one magnet, and means for selectively reversing said polarities of said at least one magnet facing said magnetic elements.
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patent: 3962792 (1976-06-01), Stepanek et al.
patent: 4231158 (1980-11-01), Possati
patent: 4669300 (1987-06-01), Hall et al.
patent: 5005297 (1991-04-01), Aehnelt et al.
patent: 5054205 (1991-10-01), Danielli
patent: 5099585 (1992-03-01), Liskow
patent: 5146690 (1992-09-01), Breitmeier
Balance Systems S.p.A.
Browdy & Neimark
Fulton Christopher W.
LandOfFree
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