Method and system for evaluating local compactness of a granular material

Abstract

An evaluation method in which a capacitive sensor is placed in a region of a container, into which a granular material is fed so as to contact the sensor, and the variation in the impedance of the sensor caused by feeding in the material is evaluated. The method is particularly useful for evaluating the compactness of sand in a formwork for making metal castings. The evaluation system includes a sensor defined by plates sensitive to the variation in the dielectric; and a conditioning and control circuit for indicating the variation in the capacitance of the plates, or more generally the total impedance of the system, when the granular material is fed into the container. In one embodiment, the plates of the sensor are defined by two combs made of conducting material, having two numbers of interlacing segments, and located on a rigid or flexible support.

Description

[0001] This application is a continuation of U.S. patent application Ser. No. 10 / 357,060, filed Feb. 3, 2003.[0002] The present invention relates to a method and system for evaluating local compactness of a granular material. BACKGROUND OF THE INVENTION [0003] Sand casting is one of the methods most commonly used in foundry work, and has been developed over the years so that numerous widely differing ways now exist of obtaining molds for casting highly complex parts of good dimensional accuracy. One of the most advanced methods in this respect is what is known as “Lost Foam Casting”. [0004] The common denominator of all sand casting methods is the use of sand as a moldable material to support the metal, and which forms a “negative” of the required casting. In the case of complex molds in particular, however, it is difficult to ensure all the gaps in the pattern (eventually forming the underside recesses or cavities in the finished part) are filled with sand to an adequate degree of ...

Images