Flexible insulating sheet

Abstract

The present invention is a twin-wall rigid plastic sheet intended to provide protection and insulation in applications where a small bending radius for the twin-wall plastic sheet is desired. The twin-wall configuration includes a smooth or flat outer single sheet and a contoured inner single sheet separated by a series of similar plastic ribs to form a connected row of longitudinal cavities or “channels”. The inner wall is contoured in a concave manner to form a relief between each rib. When the twin-wall sheet is flexed, each relief distorts to minimize stress in the transverse direction while maintaining high rigidity in the longitudinal direction. In another embodiment of the present invention, multiple single sheets separated by ribs and contoured similarly to that of the inner wall are added between the contoured inner wall and smooth outer wall.

Description

TECHNICAL FIELD[0001]The present invention relates generally to insulating sheet for enclosures, and more specifically to applications in which it is desirable to allow a small bending radius in a thermoplastic twin-wall insulating sheet.BACKGROUND[0002]A type of commercially available insulating sheet is referred to as “twin-wall” plastic sheet. In this structure, two or more parallel single-sheet layers of thermoplastic material are spaced apart from each other by continuous “rib” structures of similar thermoplastic material that determine, along with the thickness of each single-sheet layer, the overall thickness dimension of the twin-wall sheet. The two outermost layers are referred to as the “walls” and are often distinguished from each other as an interior wall and an exterior wall, depending on the details of the twin-wall sheet structure and possible surface treatment of one or both walls. The known and commercially available structures of this type have perpendicular ribs, ...

AI Technical Summary

Benefits of technology

[0020]In another embodiment of the present invention, a plurality of single thermoplastic sheets contoured similarly to that of the inner wall are added in a generally parallel manner between the contoured inner and flat outer walls. A series of ribs of similar thermoplastic material are located between each adjacent single sheet to form an array of multiple attached rows of longitudinal channels. When this multiple layer form of the present invention is flexed, all of the arcs formed in the multiple layers simultaneously distort to minimize bending stress in the transverse direction while maintaining rigidity in the longitudinal direction.

Problems solved by technology

The relatively high rigidity of currently available translucent twin-wall sheet made of materials such as polycarbonate, acrylic or high-density PVC make it unsuitable for many applications requiring a curved or flexible panel such as small greenhouses with curved roofs, hoop houses, crop tunnels, cylindrical plant protectors, and curves in structural glazing where a bending radius of less than 300 mm may be desired.

Twin-wall sheet can be created using a more flexible material such as polypropylene or low-density polyethylene; however, doing so reduces the Shear Modulus of the twin-wall sheet in both the longitudinal and transverse directions, making it less desirable for applications where high rigidity is still advantageous in one direction, such as hoop houses, crop tunnels, and plant protectors.

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