Measuring and testing – Vibration – By mechanical waves
Patent
1984-12-07
1986-09-30
Birmiel, Howard A.
Measuring and testing
Vibration
By mechanical waves
73 32A, 73290V, 73589, 73629, 73644, G01N 2900
Patent
active
046141154
DESCRIPTION:
BRIEF SUMMARY
The object of the invention is an ultrasonic process and apparatus for monitoring and measuring the evolution with time of certain physical and/or chemical characteristics within a changing medium or between two media.
The invention is of utility in the cases cited below by way of non-limiting examples:
measuring the setting time of a hydraulic binder,
evaluating the time for a paint to dry or an adhesive to harden,
studying changes of state, from the solid state to the liquid state or vice versa,
physico-chemical modification of a contact (oxidation-work hardening),
crystallization of a substance in solution or sedimentation of a substance in suspension,
polymerization of a plastics material,
evaluation of blood coagulation and/or sedimentation time,
studying the curdling of milk.
It has already been proposed to use an ultrasonic apparatus to detect certain physical or chemical phenomena. In this respect, the state of the art is illustrated by British Pat. No. 2 060 883 which describes a frost detector. According to this patent voltage pulses at an ultrasonic frequency are applied to a winding which surrounds a bar connected to a rod laid in a trench dug into the surface of a road. The bar is of a material which exhibits a magnetostrictive effect under the influence of the magnetic field created in the winding. This results in vibrations at ultrasonic frequencies which are transmitted into the rod and which are reflected at its walls. The way in which they are reflected differs according to whether the rod is in contact with water or with ice. On the other hand, by virtue of magnetostriction the bar induces voltage pulses in the winding because of the reflected vibrations. These pulses are collected and from them it is possible to deduce whether the rod is surrounded with water or ice. The use of magnetostriction is essential in this patent.
In U.S. Pat. No. 4,320,659 there is described an apparatus for measuring the accoustic impedance of a medium or for detecting the level of a liquid. To this end, a vertically polarized transverse ultrasonic wave is fed into a bar with a particular angle of incidence from a lateral surface or an end surface which is inclined so that this wave is propagated in zig-zag fashion by successive reflections; the wave collected at a remote point is different by virtue of the coupling which is produced between the bar and the medium in which it is immersed. In a variation, the polarized transverse wave is fed into the bar through an end face but the ultrasonic beam is subject to reflections which are propagated parallel to the axis of the bar; moreover, the bar has a lateral surface featuring longitudinally spaced notches which serve as reflection surfaces. The reflections collected differ according to the nature or the level of the medium with which the bar is in contact. The use of polarized transverse waves is essential in this patent.
Also known is the use of ultrasound for measuring thicknesses or lengths of parts or for locating the evaluating defects (scale, cracks, splits). The reading is made immediately after the echo obtained as a result of reflection of the waves emitted in the longitudinal direction. The secondary echoes have something of a nuisance value in that the reading is taken only on the main echoes of the longitudinal waves emitted parallel to the axis.
In all these examples, ultrasound is utilized with a limited objective (detection of frost, detection of defects, measurement of distance, detection of level, etc) under specific operating conditions (detection of direct echoes only, deliberate creation of vertically or horizontally polarized waves, use of waves directed in zig-zag fashion, use of reflecting surfaces at predetermined locations, etc).
The invention is distinguished from these known uses limited to specific cases in the sense that it provides a general purpose process for monitoring and measuring the evolution in time of sundry phenomena within a medium or between two media, in accordance with which there is immersed in this medium or these m
REFERENCES:
patent: 4320659 (1982-03-01), Lynnworth et al.
patent: 4325255 (1982-04-01), Howard et al.
patent: 4414849 (1983-11-01), Brown et al.
Bocquet Michel
Moreau Michel
Pelletier Jean L.
Birmiel Howard A.
Bryan James E.
Ferguson Jr. Gerald J.
Hoffman Michael P.
Societe d'Etudes et de Recherches de l'Ecole Nationale Superieur
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