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Bookbinding with plastic covers

  • US 3,953,056 A
  • Filed: 06/18/1974
  • Issued: 04/27/1976
  • Est. Priority Date: 06/09/1972
  • Status: Expired due to Term
First Claim
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1. The method of binding a book which comprises making successive book covers, each in one operation in a single station from a portion of a preformed sheet of homogeneous synthetic high polymer thermoplastic material of higher pick strength than paper, which method comprises supplying the synthetic high polymer as an elongated sheet of uniform thickness and in intermittent steps between confronting elements comprising a die and a base element having relative movement toward and from one another, the die having narrow rules projecting therefrom toward the base element, a first of said rules being a closed figure and being shaped to the outline of a cover that is to be severed from the elongated sheet, and other rules located within said figure and in position to form hinge lines for the cover, moving the first rule of the die into contact with the plastic sheet, continuing the movement of the first rule toward the base element and through a stroke that displaces the plastic for substantially the full thickness of the sheet around the outline of a cover, and also moving the other rules of the die into contact with the plastic to heat and displace the plastic of the sheet for a depth less than the depth of displacement of the first rule and for a depth dependent on the displacement of plastic by the first rule and at locations that provide hinge lines for the cover, intermittently moving the sheet material to advance it from under the die, and bringing a new portion of sheet material under the die, repeating the operation of the die through another cycle to make another cover after each movement of additional material into positions under the die, holding the successive covers in the sheet while advancing the covers and the plastic sheet together beyond the die and to a delivery station, separating each successive cover from the rest of the sheet along said outline of the cover at the delivery station, assembling and clamping leaves that make a book filler of a thickness substantially equal to the distance between the hinge lines of the cover, stabilizing the book filler by application of adhesive to the spine of the filler while the leaves are clamped in assembled relation, removing the clamps when the adhesive is set, trimming the stabilized filler to a height and width less than the height and width of the front and back cover panels so that the cover will overhang the edges of the leaves of the filler, then heating said adhesive for adhesively securing the high pick strength spine panel to the stabilized filler while the surface of the spine panel is at a temperature substantially lower than the deforming temperature and the spine panel remains in a solid, unfused state of the preformed plastic sheet from which the cover is made, and using an adhesive that is strong enough to bind the filler to the cover without end papers, said book covers being made from a sheet of material from the group of plastics that are heated by exposure to a high frequency electric field and that are of a composition that tears with a smooth tear along a tear line, exposing the sheet to a high frequency electric field by using said base element and the rules of the die as the electrodes of the high frequency field at said single station, and displaceing material in the sheet by pressure applied to the heated localized areas of the sheet between the electrodes of the high frequency electric field, reducing the thickness of the plastic along said localized areas to a thin section along which the cover can be torn from the sheet at the delivery station and similarly heating and displacing at said single station other material of the sheet along other localized areas where the front and back panels connect with the spine panel to form the hinge lines of the cover.

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