Plastic article or earthenware shaping or treating: apparatus – Female mold and means to feed measured charge of fluent... – Means to move feed means to female mold
Reexamination Certificate
2000-03-31
2002-12-17
Silbaugh, Jan H. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and means to feed measured charge of fluent...
Means to move feed means to female mold
C425S403100, C425S812000, C425S408000, C425S412000, C425S447000
Reexamination Certificate
active
06494704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to mold presses. More particularly, the present invention relates to mold systems whereby corresponding mold halves are reliably maintained in a desired X-Y orientation during the molding of articles, particularly starch-bound articles.
2. The Relevant Technology
There exists a large interest in the development of articles of manufacture that are more environmentally friendly than materials such as paper, paperboard, thermoplastics, polystyrene, glass, wood, and even metals. Environmentally friendly materials of recent interest include starch-based compositions that are foamed or expanded. Such compositions are beginning to make inroads into industries such as paper, plastic, polystyrene, etc, particularly in the field of disposable containers and other packaging materials.
The last several decades has seen the proliferation of disposable articles throughout industrialized nations. The convenience of single-use articles, the need for single-use sterile articles, and the need for disposable light weight and insulative materials have caused the increased use of polystyrene as a preferred container material. Polystyrene is now being manufactured and fabricated into single-use articles, and thereafter abandoned to the environment on a significant scale. Polystyrene has the qualities of sturdiness, light weight, thermal insulation, and containment of liquids among others. Unfortunately, polystyrene is entirely non biodegradable and, although it may be substantially inert to the environment, it along with other materials such as paper, wood, and metals constitute a significant fraction of municipal landfills. Additionally, polystyrene, if incinerated, can release significantly harmful toxins into the environment. In addition to being non biodegradable, polystyrene represents the consumption of the non-renewable resource of petroleum. Additionally, time between planting a tree and harvesting can amount to several years or decades.
A substitute for polystyrene foam has been found in a foamed cellular matrix made from starch that may contain fibers and fillers. One application of containers made of a starch-bound cellular matrix was seen at the Lillihammer Winter Olympic Games where biodegradable containers made by Biopac Corporation were introduced to the public. This technology is now assigned to E. Khashoggi Industries, LLC, of Santa Barbara, Calif. One drawback to these containers was that processing and materials costs were made too high for such containers to be uneconomical viable.
Researchers at EKI have developed improved compositions for manufacturing starch-bound containers that are far less expensive than those made by Biopac. Displacement of a portion of the starch with inexpensive inorganic mineral fillers together with fibers for reinforcement have greatly reduced both materials, as well as production, costs. The result is that such articles are less expensive and more economical to produce. In addition, such articles have far better strength and other mechanical properties, which allows for the manufacture and use of articles that have substantially smaller wall thicknesses.
Another drawback to the molding process as developed by Biopac was that the molding equipment consisted of modified baking molds used to manufacture food items such as waffles, cookies, edible containers and the like. Whereas such molding systems were adequate for molding relatively thick-walled food items and containers, such as those made by Biopac, such systems have proven to be problematic when used in the manufacture of articles having smaller wall thicknesses and stricter product tolerances. An exemplary mold apparatus known in the art for manufacturing bowls is illustrated in FIG.
1
.
As seen in
FIG. 1
, a conventional mold apparatus includes paired male and female molds joined together by a hinge mechanism. The hinge allows the male mold half to be raised up relative to the female mold in order to allow the insertion of mold material therein. Thereafter, the male mold is lowered into the female mold to yield a mated male-female mold pair having a mold cavity defined therebetween. However, hinged male and female mold pairs are prone to excessive variations in mold cavity dimensions such that maintaining a consistent mold cavity throughout an iterative molding process has proven to be quite difficult.
One problem involves the hinge. In order to provide the function of allowing the male mold to open and close relative to the female mold the hinge necessarily allows some degree of motion between the two mold halves. The problem arises where there is significant lateral movement. Even slight deviations from the ideal mating arrangement can yield an uneven mold cavity. For example, where the desired wall thickness of a given article is 2 mm, movement of the male mold by an amount of even 0.5 mm can yield an actual mold cavity having a thickness of 2.5 mm on one side and only 1.5 mm on the other. Such uneven mating not only yields a product that is substantially deformed due to the uneven wall thickness, it may also prevent proper formation of the article in the first instance.
The molding of starch-based articles having a foamed cellular matrix involves rapid expansion of the mold material as a result of formation of internal water vapor as well as removal of the water by evaporation to yield a solidified product. Because the rate of heat transfer is relatively constant between the mold and the mold material, deviations in wall thickness can greatly affect the rate at which a particular portion of the article solidifies or cures. More specifically, areas where the mold cavity is thicker than intended can yield an area of under cured material such that portion of the article upon demolding may be too soft or inadequately formed. On the other hand, overheating the article such as by leaving the article within the mold for longer than is optimal can scorch or burn the article. Thus, areas where the mold cavity is too thin compared to what is optimal may cause burning or scorching of that portion of the molded article. In view of this, the importance of properly mating the female and male molds to yield a substantially uniform mold cavity becomes readily apparent.
In addition to unwanted lateral movement between the male and female mold halves due to the hinge mechanism, which is only exacerbated as the hinge undergoes wear and tear, the mold halves can become misaligned due to fluctuations in mold temperature. It is well known that metals such as aluminum or steel used in many mold systems undergo significant expansion or contraction in response to fluctuations in temperature. Thus, heating the hinged mold apparatus depicted in
FIG. 1
can cause mold misalignment due to uneven thermal expansion of the molds, particularly where the molds have varying thickness. Of course it is possible to make adjustments to the molds in order to offset the effects of thermal expansion. However, such adjustments are only feasible while the mold apparatus are not in use and the molds are sufficiently cool so as to avoid injury. Thus, such adjustments are often difficult to make and can cause significant downtime and cost in the overall manufacturing process.
It would therefore be an improvement in the art to provide mold apparatus and systems for maintaining accurate X-Y orientation between the mold halves and which overcame other problems associated with prior art mold apparatus.
It would also be an improvement in the art to provide mold apparatus and systems for molding starch-bound compositions that maintained a sufficient dimension variation tolerance and which avoided the problems associated with molding starch-bound articles having disparate wall thicknesses.
It would be a great improvement in the art to provide mold apparatus and systems that could repetitively and reliably form foamed starch-bound articles while avoiding both under curing and over curing of the starch-based compositions used to manufacture such articles.
Andersen Per Just
Hodson Simon K.
Kumar Amitabha
Kumar Sandeep
Miller Denise S.
E. Khashoggi Industries, LLC
Nguyen Thu Khanh T.
Silbaugh Jan H.
Workman & Nydegger & Seeley
LandOfFree
Mold apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mold apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mold apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2929587