Automatic sheet decurler

Claim 1

Apparatus for decurling a sheet of material curled downwardly at its trailing end about an axis extending transversely to the direction in which the material is traveling, comprising: P1 a pair of fixed, elongated support surfaces of arcuate convex shape positioned substantially parallel to each other in spaced apart relation and extending transversely with respect to the path of travel of the sheet to be decurled, and forming a decurling zone between said arcuate support surfaces recessed below the top extremities of said support surfaces, said support surfaces having a length at least as great as the width of said sheet; means for creating a pressure gradient in said zone between said elongated support surfaces throughout the length thereof sufficient to deform the sheet of material in a direction opposite to the curl in the sheet, said means for creating a pressure gradient comprising a vacuum chamber in fluid flow communication with said decurling zone on the reverse side of said support surfaces from that traversed by a sheet of material, means for evacuating said chamber, and means disposed on the side of the sheet of material opposite the support surfaces for directing a pressurized air stream between the support surfaces into the decurling zone against the sheet material; and pulling means for drawing the sheet of material over said support surfaces and through said zone, whereby the entire sheet will progressively pass through said zone and be decurled, said pulling means positively engaging the sheet and cooperating with said pressure gradient in said decurling zone to hold said sheet in tension therebetween to facilitate the decurling of said sheet.

Claim 6

A method for decurling a paper sheet curled at its trailing end about an axis extending transverse to the direction in which the sheet is being conveyed, comprising: positively engaging the forward end of the sheet by gripping means; pulling said sheet, by said gripping means, over a pair of closely spaced, substantially parallel, elongated support surfaces extending transversely to the direction of travel of the sheet across the entire width of the sheet; simultaneously creating a pressure differential across a zone between and offset from said support surfaces sufficient to continuously force said sheet against said support surfaces by directing pressurized air into said zone over substantially the entire length thereof on the side of the sheet opposite the support surfaces and simultaneously drawing a vacuum in said zone on the other side of said sheet to force said sheet into friction contact with said support surfaces and deform it in said zone in a direction opposite to that in which it is curled; and deforming said sheet material into said zone between said support surfaces by operation of said pressure differential in a direction opposite to that in wich the sheet material is curled, and thereby placing said sheet material in tension between said gripping means and said pressure differential zone between said support surfaces and decurling said sheet as it is deformed into said zone under tension.

Claim 7

A method for decurling a paper sheet curled at its trailing end about an axis extending transverse to the direction in which the sheet is being conveyed, comprising: positively engaging the forward end of the sheet by gripping means; pulling said sheet, by said gripping means, over a pair of closely spaced, substantially parallel, elongated support surfaces extending transversely to the direction of travel of the sheet across the entire width of the sheet; simultaneously creating a pressure differential across a zone between and offset from said support surfaces sufficient to continuously force said sheet against said support surfaces by directing pressurized air into said zone over substantially the entire length thereof on the side of the sheet opposite the support surfaces and simultaneously drawing a vacuum in said zone on the other side of said sheet to force said sheet into friction contact with said support surfaces and deform it in said zone in a direction opposite to that in which it is curled; and deforming said sheet material into said zone between said support surfaces by operation of said pressure differential in a direction opposite to that in wich the sheet material is curled, and thereby placing said sheet material in tension between said gripping means and said pressure differential zone between said support surfaces and decurling said sheet as it is deformed into said zone under tension.