Thermal measuring and testing – Thermal testing of a nonthermal quantity – Expansion or contraction characteristics
Reexamination Certificate
2002-11-14
2004-07-27
Verbitsky, Gail (Department: 2859)
Thermal measuring and testing
Thermal testing of a nonthermal quantity
Expansion or contraction characteristics
C356S634000, C356S625000
Reexamination Certificate
active
06767127
ABSTRACT:
BACKGROUND OF THE INVENTION
The task of a dilatometer is to measure the linear dimensional variation of a sample upon a variation in the temperature to which the sample is exposed. The sample is placed inside a generally tubular oven, and the temperature in the oven is controlled and varied. The dimensional variations of the sample on temperature variation are read by instruments known as dilatometers, which can differ from each other in terms of the system used for heating the sample and also in terms of the system for measuring the dimensional variations. The dimensional measuring methods are mechanical, electronic or optical, while the heating systems are almost always electrical, by radiation.
In mechanical dilatometers the sample is materially in contact with a system of levers which amplify each tiny variation in size, and record the variation on a sheet of paper by means of a pen.
In electronic dilatometers the sample is in contact with a small rod made of refractory material which transfers the dimensional variations to an electrical device through a differential transformer. The electric signal is then amplified and transformed into a graph using a recording system.
The optical dilatometer measures the dimensional variations by means of a ray of light which is deflected from a small mirror connected by a lever to the sample being measured.
With a laser beam it is possible to carry out the measuring operation using the Abbe method (optical interferometry), which reaches a resolution which is equal to the wave length of the light used.
A recent innovation in the field of dilatometry is the chance to carry out the measurement of the dimensional variations without touching the sample, but simply by observing it with a high-definition camera. In this way measures can be made of samples in a semi-liquid or even liquid state.
In the majority of cases the sample inside the oven is in contact with a measuring system that is inevitably subject to deformations which influence the accuracy of the measurement and, in all cases, is in contact with a support which, as it is prone to substantial dimensional variations during the measuring operation, must have an effect on the results of the operation.
It is therefore always necessary to carry out a calibration of the instrument which is done by performing a measuring operation of a sample which has a known dilatation in order that the deviations from the zero line produced by the dilation of the instrument itself can be calculated.
In the case of mechanical or electronic dilatometers, where the sample is located in a sample-holder made of refractory material and the dimensional variations are read by a rod made of refractory material, the situation created is rather complex, in that all of the elements of the measuring system are subject to thermal dilations. The result of this complex sum of different dilations can be that the dilation of the measuring system is of the same order as the dilation of the sample under examination. Naturally the dilation of the measuring system must be subtracted from the dilation of the sample, an operation that can be done manually or automatically. These system calibrating operations must be frequently repeated since as the materials age their thermomechanical properties change; a standard control procedure is necessary, at predetermined intervals.
Often a same material gives different dilation data if measured using different instruments, due to the fact that the calibration procedure has not been carried out in the same way as before.
Even for optical dilatometers where there is no contact, the instrument calibration problem persists, in that even though the sample is not touched by the measuring system it still has to be supported in order to guarantee a perfect positioning thereof inside the oven chamber. This support too is subject to thermal dilations which have to be measure and subtracted from the dilations of the sample during the course of the examination.
All of the above leads to considerable doubt over the exactness of the measurements, and extreme caution when taking the measurements.
A recent optical dilatometer, described by the same applicant, solves the problems connected with the dilation of the measuring system and/or the sample support method, virtually eliminating the tedious task of calculating a calibration curve; it further enables dynamic dilatometric measurements to be made, i.e. measurements in which the sample under examination is subjected to continuously-variable temperatures.
The above-mentioned recent dilatometer, which was described in a patent belonging to the present applicant, comprises a rest base for the sample and two optical systems which identify two optical paths, parallel to and aligned with the rest base, the paths being located at a predetermined distance from each other and being able to focus the images of the ends of the sample being measured. The dilatometer further comprises a visualising and measuring device which can gather the images focussed-upon by the optical systems. This dilatometer is very precise and impervious to the measuring system dilations, but can carry out measurements through only a rather limited interval of variation, in that the optical paths cannot follow and focus on large dilations; this makes the dilatometer unsuitable for measuring materials which have a high coefficient of dilation, or for measuring samples subjected to large-range thermal gradients.
The main aim of the present invention is to obviate the limitations and lacks in the prior art.
An advantage of the invention is that it maintains a high measuring precision, is not influenced by the dilations of the measuring system, and is able to operate in an extremely wide dilation interval—much wider than any range measurable by existing dilatometers of the same type.
These aims and more besides are all attained by the invention as it is characterised in the claims that follow.
SUMMARY OF THE INVENTION
The invention comprises: a rest base for a sample to be examined, at least a first and a second optical systems, identifying two optical paths located at a predetermined distance one from another. The at least a first and a second optical systems are commandable and are able to focus, with a predetermined enlargement, on two ends of the sample. The at least a first and a second optical systems are arranged and maintained on parallel planes which are also parallel to the rest base. The invention also comprises at least a monitoring and measuring device able to gather images sent by the at least a first and a second optical systems. The apparatus is structured to carry out measurements of dimensions of a sample while completely eliminating any influence on the measurements by the measuring system and the rest base for the sample.
REFERENCES:
patent: 3788746 (1974-01-01), Baldwin et al.
patent: 4636969 (1987-01-01), Kyoden et al.
patent: 4762424 (1988-08-01), Baricevac et al.
patent: 4924477 (1990-05-01), Gilmore et al.
patent: 4930894 (1990-06-01), Baldwin
patent: 5231285 (1993-07-01), Berg
patent: 5479261 (1995-12-01), Hansen
patent: 6400449 (2002-06-01), Maris et al.
patent: 6476922 (2002-11-01), Paganelli
patent: 3514000 (1986-10-01), None
Browdy and Neimark , P.L.L.C.
Brown V
Expert System Solutions S.R.L.
Verbitsky Gail
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