Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common...
Reexamination Certificate
2000-08-22
2002-05-07
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
C425S258000, C425S260000, C425S448000
Reexamination Certificate
active
06382947
ABSTRACT:
TECHNICAL FIELD
The invention is directed to an apparatus and method for color blending differently colored batches of agglomerating flowable material together to fill a mold with a mottled heterogeneous charge including visible colored clumps of material from each colored batch.
BACKGROUND OF THE ART
A mottled, dappled or variegated random pattern is considered aesthetically pleasing in a number of applications providing a natural blended coloring. The irregular arrangement of blotches or patches of color in a multi-colored heterogeneous surface can be produced from flowable material which has been tumbled together or agglomerates naturally in a molding process.
In the specific example provided in the present description, a blended or mottled pattern is a desirable feature in the production of concrete paving stones and retaining wall blocks. In this art, using iron oxide pigments in the mix design of the concrete batch, the majority of paving stones and approximately one-half of retaining wall products are color blended.
In this art, the “blending” of colors as used in this description and in the trade does not relate to complete mixing that would produce a homogenous color composite of the two input colors. Rather the word “blending” relates to the mixing of two, three or sometimes four colored batches of concrete together such that the finished products contain distinct clumps or patches of each color consistently through the production of paving stones or retaining wall blocks.
An essential characteristic of such color blending is the consistency of distribution of each color used in the blending process throughout the production run. In the past, it has been extremely difficult to ensure consistency while retaining a random appearance to the finished product. Random mottling, with a consistent percentage of the surface area visible in each of the colors is the ideal. However, prior art systems are extremely dependent upon the skill of operators, result in wastage and unsatisfactory color blending in many cases. The capacity to produce a consistently blended product is advantageous in that wastage is reduced and the aesthetic appeal of the well blended product creates a significant market advantage.
Traditionally, because of the technical difficulties, most color blending has involved only two colors. The production of a consistently blended three color mottled pattern has involved extensive rework and generally unsatisfactory appearance in that the distribution of three colors is very sporadic and unpredictable. Mixing of four colors presents almost insurmountable difficulties for prior art systems. In many cases these difficulties can be addressed by manually mixing and laying the finished paving stones during installation with a trained eye to ensure even distribution of the different colors throughout the finished installation. A manual laying system increases labour costs and is generally inefficient in large areas where machined laying systems are preferred. In addition, the manual mixing of colored stones during installation relies heavily on the skill and perception of the installer.
In the past, color blending was carried out with a hopper having a separating bulkhead plate down the middle and filling the hopper with different colored materials on either side of the bulkhead dividing plate. A single gate at the bottom of the hopper was opened and blending of two colors occurred as both sides of the hopper were emptied simultaneously.
A refinement of this procedure included an upper hopper with a moveable plate gate serving as a funnel to feed a batch of colored material into either side of the lower divided hopper.
In the prior art, a concrete mixer was loaded with cement, pigment, sand and rock aggregate in the form of crushed stone chips or relatively small rocks, together with water and other admixtures to create a colored concrete batch. Once the raw materials are thoroughly mixed together, the mixer discharges the batch into the upper hopper and over the moveable plate to direct the flow of material into either side of the divided lower hopper. When the outlet for the lower hopper was opened, material from both sides of the hopper flowed out through the opening and tumbled together in a mottled blended charge into the mold.
There are several disadvantages to this prior art system. Firstly, when one side of the lower hopper is filled and other half of the lower hopper is empty, there is a significant amount of backflow from the filled side of the hopper to the unfilled side. As a result, the first portion of material which exits when the hopper is opened is a of single color. Generally, the first few fillings of the mold must be discarded since the aim is to produce a consistently colored mottled appearance using both colored batches.
In addition, since the extreme outward portions of the flow from the hopper are completely one color or the other, products produced in this manner generally have about 75% of the product blended in the central area of the mold, and the remaining outer 25% is evenly split between the two solid colors of the materials. Therefore, the degree of blending is satisfactory, but less than ideal, since a significant portion of the mold creates blocks that are a single solid color rather than dappled or mottled appearance as desired. These solid blocks can be distributed in the final installation, however with some skill on the part of the installer.
In prior art systems, the hopper does not drop material directly in to the mold, but rather the hopper deposits material into a filling tray. The material in the tray is agitated slightly to distribute material evenly and level the top surface, then the tray and material are transferred to a position above the mold. The filling tray has an open woven grate at the bottom and rests on a solid table during filling. An agitating grate distributes material and aids in the mixing of clumps of the different colored materials prior to depositing in the mold. When the filling tray is laterally shifted to above the mold, the relatively dry nature of the concrete mix and speed of lateral motion prevent the concrete from exuding through the bottom grating to any great extent. The mold and filling tray above it are then vibrated. Vibration agitates the thixotropic concrete mix in the filling tray to flow easily through the grating into the mold. The filling tray is removed, and a tamping head further vibrates and compacts the top surface of the material within the mold. Afterwards the mold and tamping head are withdrawn, and the finished blocks are conveyed away on a pallet.
This prior art system is generally accepted as the best that can be provided with existing equipment, however, the relatively large number of finished blocks of a single solid color with no blending of colors is a significant disadvantage. As well, the large amount of waste created when the first batch is dropped into one side of the hopper is disadvantageous, especially where a small production run or small number of batches is produced. With prior art systems, it is undesirable for a manufacturer to produce a short production run of blended product despite market demands since the wastage on starting up a production run becomes significant.
A further disadvantage of the split hopper prior art system is a slow cycle time and inefficient blending. Batches of colored material are gravity fed and ideally the amount of material stored in either side of the split hopper should be identical to result in the same quantity of flow when the clamshell gates are opened. However, since material is mixed in a single mixer, one color at a time, in general, the amount of material stored in one side of the split hopper will always be less than the amount of material stored in the other side. This results in uneven amounts of material flowing out when the hopper outlet is opened. For example, if one side of the hopper is full, the other side is almost empty awaiting refilling from the mixer, the volume of material flowing under gravity from the ful
Cohen Jerry
Davis Robert
Hengestone Holdings Inc.
Perkins, Smith&Cohen
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