Importance

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Abstract

A ring binder cover (4) is composed of a pair of themoplastic sheets (20, 22) superimposed in edge-to-edge relation with a stiffener insert panel (23) disposed therebetween. The insert panel bears two parallel grooves (25, 27) which divide the insert into a spine zone (30) and two cover zones (24, 26). The material of the insert lying at the bottom of the grooves forms a pair of flexible strips (32, 34) which, combined with the adjacent portions of the cover sheets, form hinges between the spine and each cover. The peripheral edge portions (40) of the two thermoplastic sheets are sealed together and provide a sealed envelope for the stiffener insert which defines semi-rigid back and front cover panels of the binder, hingedly connected to a rigid spine. The insert can be provided with insert notches (370, 470, 570) at each end of each flexible strip to reduce outward protuberance of the peripheral edge at the hinge ends. At the mouth of each insert notch, the peripheral edge can carry straight across, or can follow inward toward the insert notch to form a seam notch, or can have a seam area which extends inward toward each insert notch. Another feature which can be incorporated into the ring binder concept of this invention is the idea of a curvable spine. The curvable spine idea involves providing one or more hinge-like spine grooves (641, 642, 643, 644) on the inside surface of the spine portion of the insert between the two hinge grooves. This allows the spine to flatten when the covers are open, but to curve about the longitudinal axis of the spine (concave on the inside and convex on the outside) when the covers are closed.

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First Claim