Measuring and testing – Vibration – Resonance – frequency – or amplitude study
Patent
1996-03-20
1998-09-22
Williams, Hezron E.
Measuring and testing
Vibration
Resonance, frequency, or amplitude study
73584, 73 1201, G01N 2912
Patent
active
058116800
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to methods and apparatus for testing the quality of fruit.
BACKGROUND OF THE INVENTION
High-value fresh agricultural products, particularly those intended for export, must be carefully handled and sorted in order to meet high quality standards. Many methods are available for detecting quality and for sorting according to external fruit properties, such as size, shape, color and external appearance. Internal properties, such as ripeness, taste, flavour, and internal damage, are generally determined indirectly, by linking the property to one or more external fruit properties, or are measured directly through destructive tests.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel non-destructive method and apparatus for testing the quality of a fruit.
According to the present invention, there is provided a method of testing the quality of a fruit, comprising: applying a dynamic force to the fruit; detecting the mechanical response of the fruit to said dynamic force via a piezoelectric film transducer supported on a displaceable supporting member such that the film transducer is bent, to induce a strain therein, by said dynamic force and outputs an electrical signal corresponding to the rate of change of the induced strain in the film transducer caused by said dynamic force; and analyzing said electrical signal to indicate the quality of the fruit.
A piezoelectric film transducer is a relatively new type of transducer which has begun to find extensive use in acoustical applications, both in acoustical emitters and in acoustical receivers. One construction now commercially available includes a piezoelectric polymeric film of polyvinylidene fluoride having an electrically-conductive film coated on its opposite sides. The present invention utilizes such piezoelectric film transducers by supporting them on a displaceable supporting member so that the film transducer is bent by the dynamic force (as distinguished from a static force) to induce a strain in the film transducer. Since the induced strain varies with the rate of change of the applied dynamic force, the output of the film transducer will be a measurement of the rate of change of the applied dynamic force. It is this output which is analyzed to indicate the quality of the fruit.
According to further features of the invention as included in the preferred embodiments described below, the dynamic force applied to the fruit, to produce the mechanical response detected by the piezoelectric film transducer, may be an impact force applied mechanically, electro-magnetically or pneumatically. The dynamic force may also be an impulse force or a vibrational force, such as applied mechanically by another piezoelectric film transducer, a conventional piezoelectric crystal transducer or a mechanical vibrator, or as applied acoustically by a loudspeaker, etc. The dynamic force may also be an inertial force applied by accelerating or decelerating the fruit.
According to further features included in many of the described preferred embodiments, the displaceable supporting member may be a resilient base, a flexible beam, or a pivotal arm.
According to still further features in the described preferred embodiments, the mechanical response of the fruit which is detected and analyzed may be the resonance frequencies of sonic waves produced in the fruit as a result of the dynamic force applied thereto, or may be the attenuation rate of sonic waves produced in the fruit as a result of the dynamic force applied thereto.
The invention also provides novel apparatus for testing the quality of a fruit in accordance with the above methods.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, somewhat diagrammatically and by way of example only, with reference to the accompanying drawings, wherein:
FIG. 1 illustrates one form of apparatus for testing the quality of a fruit in accordance with the present invention;
FIG. 2 illustrates a second form of apparatus for testing the quali
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Galili Naftali
Rosenfeld David
Shmulevich Itzhak
Fayyaz Nashmiya
Technion Research & Development Foundation Ltd.
Williams Hezron E.
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