Apparatus for and method of pressing plastic sheets
AssigneePPG Industries, Inc.
InventorRonald L. Ayres
Life of this patent
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Abstract
A peripheral edge-containing member is provided to reduce the length of the projectile path of fragmented particles expelled outwardly from the peripheral edge of a frangible pressing plate which is broken during the press-stretching or press-polishing of acrylic sheets. The acrylic sheets are fabricated for use in light weight transparencies.
Claims12
An apparatus for applying pressure to opposed major surfaces of a plastic sheet, comprising a pair of complementarily shaped pressing plates and means for biasing said pair of pressing plates toward one another with a selected pressing force to press said plastic sheet therebetween, wherein at least one of said pressing plates is formed of a fracturable material having at least a partially exposed peripheral edge during pressing such that when said at least one pressing plate is broken pressing particles thereof are expelled outward from said at least partially exposed peripheral edge along a projectile path having a measurable length, wherein the improvement comprises:
- means secured to at least portions of the exposed peripheral edge of said at least one pressing plate for containing said peripheral edge to reduce the length of said projectile path of said outwardly expelled particles.
In a method of applying pressure to opposing major surfaces of a plastic sheet, comprising the steps of positioning a plastic sheet between a pair of complementarily shaped pressing plates and biasing said pressing plates toward one another to press said plastic sheet therebetween, wherein at least one of said pressing plates is formed of a fracturable material and has at least a partially exposed peripheral edge during pressing such that if said fracturable pressing plate is broken during pressing particles thereof are expelled outward from said at least partially exposed peripheral edge along a projectile path having a measurable length, wherein the improvement comprises the steps of:
- securing a particle retaining layer on at least portions of the peripheral edge of said fracture pressing plate to reduce the length of said projectile path.
Dependencies are inferred from the claim text.