Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
1996-07-05
2001-08-14
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
C073S818000
Reexamination Certificate
active
06272932
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of adjusting casting sand, and more particularly to a method and apparatus for determining the optimum compactibility (hereinafter referred to as CB) of the casting sand, and for adjusting the casting sand accordingly.
It is well-known that CB is controlled to adjust casting sand in kneading batches (see, for example, Japanese Patent Publication No. 3-76710). In this method, the CB of casting sand is controlled by adding water, while amounts of additives, such as bentonite, new sand, and fine powder, are kept constant in a batch so as to achieve a given target value of the CB. However, the CB of casting sand, as a target value for the control, has been only empirically set, and there has been no method of determining its optimum CB.
On the one hand, there is a method of adjusting the amounts of additives, such as bentonite, new sand, and fine powder, to adjust casting sand on a long-term basis. In this method, the amounts of additives, such as bentonite, are adjusted by measuring the degree of ventilation, the resisting force, the percentage of active clay, and the percentage of total clay, on an hourly or a daily basis. The purpose of this is to keep constant the properties of the casting sand, such as the particle size distribution and percentage of clay thereof. This is because the casting sand is differently affected by heat when being circulated, including during kneading, molding, casting, demolding, and recovery, depending on the weights, shapes, and ratios of sand to metal, of the cast products, and because the casting sand is carried away with the product or through a dust collector.
However, there has been almost no such long-term adjusting method, wherein the deformation property of a casting mold has been considered. In other words, the deformity of a casting mold results from transportation thereof, casting of molten metal thereinto, or loading of weights thereon. Further, this deformity of the mold affects high-precision or thin-walled cast products, which are now strongly demanded in the industry. However, in a conventional long-term adjusting method for casting sand, these relationships relative to the deformities of a casting mold have not been considered, not to mention that there has been no idea to connect the long-term adjustment of the casting sand to the CB. Thus, heretofore there has been no attempt to optimize the target -value of the CB on a batch basis or long-term basis. By considering such present circumstances this invention was devised to provide a method for determining the optimum CB of casting sand, which is connected to the deformation properties of the casting mold in adjusting the casting sand.
SUMMARY OF THE INVENTION
To achieve the above-mentioned purpose the method of this invention for determining the optimum compactibility of casting sand comprises measuring compactibility of the casting sand by compactibility measuring means, and measuring a value of compressive deformation of a sample mold corresponding to the compactibility by compressive deformation measuring means, repeating the measuring step at least three times, and operating the optimum compactibility, at which a value of compressive deformation of the sample mold is the minimum, by operation means.
This invention can determine the optimum CB of casting sand, wherein a value of compressive deformation of an actual casting mold is the minimum, by using the above-mentioned means of resolving these matters.
This invention was based on the following observations. The inventor found that the value of compressive deformation could be associated with CB by selecting the deformation value as a casting-mold characteristic. That is, a case is estimated wherein the value of deformation of an actual casting mold is the minimum, by forming a sample casting mold, and by measuring the value of compressive deformation thereof. The representative characteristics of casting sand are then replaced by those of the sample mold, whose value of compressive deformation is the minimum. Conversely, it was deemed that a casting mold, whose value of deformation is the minimum, can be made by controlling the representative characteristics of the casting sand. The representative characteristics of the casting sand include a particle-size index, a percentage of total clay, or an ignition loss of the cumulatively kneaded sand. However, it was difficult to grasp relationships in a kneading batch between a compressive-deformation value and a particle-size index, or a total-clay percentage, or an ignition loss. Therefore, I found a method wherein the compressive-deformation value of casting sand was indirectly controlled by assuming the CB to be a representative characteristic, since the control of the CB in a kneading batch is comparatively easy.
Although it has been unclear what the relationship is between the compressive-deformation value of casting sand and the CB, the inventor found the relationships as in
FIG. 1
after repeated experiments on this point.
FIG. 1
shows the relationships between the CB percentages and values of distortion when a constant compressive load is applied to sample casting molds. In kneading recovered sand A and B and new sand, they have their respective different relationships between the CB percentages and compressive-deformation values, and the CB percentage, where the compressive-deformation value is the minimum, becomes smaller in sequence from the recovered sand A to B to new sand. Further, even if the kinds of sand differ, as for A, B, and the new one, the curves are always convex downward within a range of the CB percentages usually in use. Thus, to minimize the compressive-deformation value the CB may be controlled so as to minimize its compressive-deformation value. As stated above, this invention aims to find the relationship between the CB and distortion values when a constant compressive load is applied thereto, and to adjust the optimum casting sand by applying this relationship to the control of the CB.
REFERENCES:
patent: 3638478 (1972-02-01), Dietert et al.
patent: 4550768 (1985-11-01), McMullen et al.
patent: 4616508 (1986-10-01), Jorn
patent: 4699011 (1987-10-01), Bradway et al.
patent: 63-34775 (1988-09-01), None
patent: 1-15825 (1989-03-01), None
patent: 5-71752 (1993-09-01), None
Gray Cary Ware & Ware & Freidenrich LLP
Noori Max
Sintokogio Ltd.
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