Patent Application
20090026648
For many years, composite building products such as roofing shingles, decking boards, and the like, have been fabricated with color variance across visible surfaces of the products. Such a color variance enables these building products to mimic visual characteristics of building products formed from naturally-occurring materials, such as wood planks, slate shingles, etc. However, many processes for forming composite building products with color variation require excessively complex machinery or specialized building material feedstock that ultimately add to the complexity of the respective process. For instance, some compression molding techniques require the use of multiple types of building material feedstock having a large variance in melt flow characteristics (e.g., polymer melting temperature) in order to form a building product with any appreciable variance in color across the molded surface.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
A solution is provided for forming a variegated building product. Although not limited to a single application, the solution is well suited for forming composite roofing shingles through injection molding. In one aspect, the variegated building product forming process involves the introduction of a set of color infused pellets into the stream of feed material pellets at preselected intervals. The feed material pellets includes color of a first hue, and the set of color infused pellets possess at least a second hue at variance from the first hue, such that the combined pellets form an aggregate, non-uniformly mixed pellet mixture. According to the process, the aggregate pellet mixture is moved into a molding chamber for molding of the aggregate pellet mixture into a variegated building product. The set of color infused pellets may be introduced into the stream of feed material pellets close to the molding chamber, to aid in the non-uniformity of the pellet mixture and thus the desired variegated effect of the finished product.
In another aspect, a system is provided for forming variegated building product. Accordingly, the system includes a mixer for randomly combining a first type of feed material pellet and a second type of feed material pellet into a stream of feed material pellets, a molding chamber, an enclosed pathway extending between the mixer and the molding chamber, as well as one or more concentrate feeders. The pathway extends from a mixer outlet to a molding chamber feed throat inlet and the concentrate feeders are configured to introduce color infused pellets at preselected intervals into the stream of feed material pellets within the enclosed pathway to form an aggregate, non-uniformly mixed pellet mixture for introduction into the feed throat of the molding chamber.
Additional advantages and features of the invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
The present invention is described in detail below with reference to the attached drawing figures, wherein:
Embodiments of the present invention relate to a solution for forming variegated building products. In particular, the solution involves the introduction of color infused pellets at a desired point in the flow of feed material pellets moving towards a molding chamber, at certain intervals, to form a non-uniformly mixed aggregate pellet mixture for molding into a variegated building product. The solution significantly reduces or eliminates the need to procure color pellets of significantly varying melt flow characteristics (e.g., polymer melting temperature) as feedstock in order to form a building product with any appreciable variance in color across the molded surface.
Turning now to
With specific reference to
As depicted in
The outputs of the pellet feeding machine 118a and 118b may be at the same level in the stream of falling base material pellets, or adjacent to one another, such that one of the outputs is more downstream in the flow through the second duct portion 116. Preferably, the outputs of the pellet feeding machines 118a and 118b place the color infused pellets into the flow of base material pellets near a feed throat 122 of the molding machine 106, which also lessens the degree of mixing of the color infused pellets with the base material pellets. This is desirable because more non-uniform mixing of the aggregate pellet mixture entering a molding chamber of the molding machine 106 provides a finished molded building product with a more variegated look. At or near the feed throat 122, the pellets of the aggregate pellet mixture become melted for injection into the molding chamber; however, uniform color mixing does not occur because of the proximity of the outputs of the pellet feeding machines 118a and 118b to the injection point. Although other methods may be employed, the aggregate pellet mixture is preferably injected into the molding chamber from the feed throat 122, within a cycle of injection molding to form the finished variegated building product.
The pellet feeding machines 118a and 118b may each handle a color infused pellets of a single hue, or multiple hues, depending on the desired variegated effect in the finished molded product. Additionally, the color infused pellets are preferably fed into the base material pellet flow at preselected, random intervals, for increase non-uniformity and variegation in the molded product. For instance, a computer program may be utilized to control the output of the pellet feeding machines 118a and 118b. The program may take into account, for example, the following factors: the quantity of color infused pellets added to the raw material flow in a given molding cycle of the molding machine 106, as well as the rate at which the pellets are added; the temporal point in the injection cycle when the color infused pellets are fed into the material flow; whether to skip feeding color infused pellets for one or more injection cycles; and coordination of pellet introduction patters between the pellet feeding machines 118a and 118b when two or more hues of color infused pellets are being utilized. Certain of these factors, in bringing about the variegated effect, may be emphasized over other factors, and this emphasis may change over time.
Turning to
It should be appreciated by those skilled in the art that above described solution for forming a variegated building product is not limited to what has been particularly shown and described above. Rather, all matter shown in the accompanying drawings or described above is to be interpreted as illustrative and not limiting. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description.
