Plastic spine construction for ring binders

Claim 1

IN A SPINE CONSTRUCTION FOR LOOSE-LEAF RING BINDERS, A CURVED OUTER SPINE MEMBER FROMED OF RESILIENT PLASTIC MATERIAL AND HAVING INTEGRAL CONNECTING POSTS, A CURVED INNER SPINE MEMBER FORMED OF SIMILAR PLASTIC MATERIAL AND HAVING PERFORATIONS THEREIN ADAPTED TO RECEIVE SAID POSTS, THE RADIUS OF CURVATURE OF SAID INNER SPINE BEING GREATER THAN THE RADIUS OF CURVATURE OF SAID OUTER SPINE, A PAIR OF PAGE COVERS, A FLEXIBLE BACK MEMBER CONNECTING SAID PAGE COVERS TOGETHER, SAID BACK MEMBER BEING INTERPOSED BETWEEN SAID SPINE MEMBERS AND BEING IN DIRECT CONTACT WITH BOTH OF THEM, A RING BINDER ASSEMBLY OVERLYING SAID INNER SPINE MEMBER, SAID POSTS ALSO EXTENDING THROUGH SAID BACK MEMBER AND SAID RING BINDER ASSEMBLY, AND MEANS ON THE INNER ENDS OF SAID POSTS TO LOCK SAID SPINE MEMBERS, AND SAID BACK MEMBER AND SAID RING BINDER ASSEMBLY TOGETHER, AND TO DRAW SAID SPINE MEMBERS TOWARD EACH OTHER SUFFICIENTLY TO ASSUME SUBSTANTIALLY THE SAME CURVATURE, AND THEREBY PROVIDE SQUEEZING PRESSURE ALONG THEIR MARGINAL EDGES AGAINST SAID BACK MEMBER.