Heating – Work chamber having heating means – Combustion products heat work by contact
Reexamination Certificate
1999-07-09
2001-12-11
Lu, Jiping (Department: 3749)
Heating
Work chamber having heating means
Combustion products heat work by contact
C432S209000, C425S174400, C126S09200C
Reexamination Certificate
active
06328559
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is related to the field of custom forming and installation of acrylic counter tops. In particular, the invention is directed to a method and apparatus for molding preformed acrylic sheets into selected shapes.
Acrylic material and acrylic composites in the form of thick boards have long been used successfully as countertops and the like in kitchens and bathrooms. These “solid surface” materials have an attractive finish which can withstand exposure to a wide range of temperatures and materials without being damaged. Acrylic, however, is very difficult to mold after it has been formed. Consequently, it has been required that the counter tops and the like be formed in a shop. Further, any irregular surfaces, such as curves, rounded edges and backsplashes, must be separately formed and then glued into position on the acrylic boards. To employ acrylic materials at all, the space may needed to be built out to match the material, rather than forming the material to match the space. This need for labor and special forming, as well as the cost of the acrylic itself, has made the cost of using acrylic materials prohibitive.
Recently, acrylic materials have become available in thinner sheets, ranging from ⅛inch to ¾inch. The sheets are intended to be mounted onto wooden counters as a laminate layer, thereby forming a counter top which has the appearance and some of the increased durability of the solid surface counter tops but at a reduced cost. These sheets are not intended to be molded into curved shapes, like certain plastic laminates. Consequently, curved portions and backsplashes must still be separately formed and then glued together, as with traditional acrylic boards.
Attempts have been made to post-form these sheets using techniques employed for laminate sheets of other materials, such as plastic sheeting. Typically such efforts include taking the portion of the sheet intended to be formed and placing it in a closed-walled, convection oven. The convection oven is operated at a temperature of about 400° F. and the portion of the sheet is left in there for several minutes until the laminate sheet becomes flexible. This flexible portion is then molded to a selected shape which it retains after cooling.
Although the thin acrylic sheets are rendered flexible such that they can be molded when employing such techniques, these attempts have ultimately proved unsuccessful. Unlike the traditional laminate materials, the acrylic sheets tend to discolor (turning cloudy or whitish) when they are molded and cooled in this manner. Further, after a portion of the acrylic sheet has been heated and cooled, it becomes brittle where it joins the portion which has not been heated such that the acrylic sheet cannot be cut without splintering or shattering.
The instant invention includes methods and apparatus which overcome these difficulties, allowing for the post-forming of acrylic sheets without discoloration. The formed sheets can be cut to fit the installation space without splintering the edges. Consequently, the space itself does not necessarily need to be built out or modified to the acrylic sheet.
SUMMARY OF INVENTION
It is an object of an aspect of the present invention to provide a method of treating acrylic sheets to allow them to be post-formed without discoloration.
It is another object of an aspect of the invention to provide a heater for delivering heat to an acrylic sheet in a controlled manner such that the sheet can be molded without discoloring the sheet.
It is another object of an aspect of the invention to provide a heater and a method capable of putting an acrylic sheet into a moldable state without rendering the molded sheet uncuttable.
One aspect of the invention is directed to a method of post-forming an acrylic sheet. A radiant heating element is provided in a heating plane. A support platform has a support surface that extends substantially parallel to the heating plane. The support surface is disposed a fixed distance away from the heating plane. A heating area is defined by the space between the heating plane and the support surface. A substantial portion of the lateral sides of the heating area are left open, exposed to the atmosphere. The heating element is heated to a predetermined temperature. The entire acrylic sheet is placed in the heating area, with the finished face of the sheet on the support surface and the unfinished face of the sheet facing the heating element. The acrylic sheet is left in the heating area for a selected period of time until the sheet is moldable. Once removed from the heating area, the acrylic sheet is placed on a mold for a selected period of time until formed and then removed.
In accord with another aspect of the invention, an apparatus is provided for preparing an acrylic sheet for molding in a post-form mold. The apparatus includes a frame. A radiant heating element is mounted to the top of the frame and disposed in a heating plane. A support platform is mounted at the bottom of the frame. The support platform has a support surface which is in a plane substantially parallel to the heating plane. A heating area is located between the heating plane and the support surface and is open to the atmosphere. The support surface is adapted to maintain the acrylic sheet in the heating area at a predetermined distance between 6 and 10 inches from the radiant heating element.
In accord with another aspect of the invention, a method is provided for forming an acrylic sheet having a thickness, a top finished surface and a bottom unfinished surface. A radiant heating element is provided substantially in a heating plane. A support platform is provided having a flat support surface that extends substantially parallel to the heating plane. The support surface is disposed a fixed distance away from the heating plane. A heating area is defined by the space between the heating plane and the support surface. The heating area has lateral sides. A substantial portion of the lateral sides of the heating area are left exposed to the atmosphere. The radiant heating element is heated to a predetermined temperature. The entire acrylic sheet is placed in the heating area such that the top finished surface is on the support surface and the bottom unfinished surface is exposed to the radiant heating element. The entire acrylic sheet is left in the heating area for a selected period of time until the acrylic sheet is moldable. The acrylic sheet is removed from the heating area and the moldable acrylic sheet is then positioned on a mold. The acrylic sheet is left on the mold until it becomes substantially rigid. The acrylic sheet is then removed from the mold.
Certain implementations of the invention provide that the radiant heating element is a metal tube with hot gas passing through it. The exhaust from the metal tube is directed to pass within or proximate to the support platform. A valve may be provided to control the amount of exhaust gas directed back to the support platform.
A means, such as an electric or pneumatic motor, may be provided to elevate or lower the support platform toward or away from the radiant heater. Further, removable side baffles may be provided to isolate a portion of the heating area from the atmosphere, thereby containing the heat and increasing the temperature in the heating area.
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McEwen David
Sellers Thomas
Lennox Thomas A.
Lu Jiping
Murtha James J.
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