Patent ID: 7303386

Claim:
An apparatus for clamping individual preheated rectangular plastic sheets prior to clamping said sheets in a rectangular clamping frame having a central rectangular opening, comprising: a lift table able to be elevated to a raised position from a lowered position whereat said lift table may receive a preheated sheet conveyed out from an oven, said table sized so that each edge sheet deposited thereon overhangs a side of said lift table, said clamping frame positioned above and aligned with said table so that a sheet deposited on said lifting table is positioned within said clamping frame opening upon elevation of said lift table to said raised position; said clamping frame opening having a series of clamps arranged about each of four sides of said clamping frame opening, said clamps each having clamping fingers extending into said frame opening and held open preparatory to receiving a sheet on said lifting table and closed to grippingly engage an edge on a sheet positioned within said clamping frame opening; a squaring mechanism including a rectangular array of paddles mounted arranged along each side of a rectangular array of elongated supports aligned with said clamping frame; opposite pairs of said elongated supports driven by a horizontal actuator to be moved horizontally towards each other from a retracted fully separated position to an advanced position spaced apart a distance corresponding to a dimension of said sheet, said elongated supports positioning a vertical portion of said paddles within but above said clamping frame opening and outside a respective sheet side when said elongated supports are in said fully retracted position; said paddles each having a horizontal portion above said vertical portion and positioned above said lift table and over an overhanging edge of said sheet; and said paddles and elongated supports collectively driven vertically by a vertical actuator to bring said paddle vertical portions within said clamping frame opening and to engage and flatten curled up edges with said horizontal portions as said paddles are lowered by said vertical actuator to bring said vertical portions within said clamping frame opening and to square said sheet within said clamping frame upon subsequent operation of said horizontal actuator moving said vertical portions together and thereby insuring that said clamping fingers are engagable with said sheet upon operation of said clamps.