Patent ID: 7665925

Claim:
A binder comprising: a spine portion; and a plurality of rings arranged at intervals in a longitudinal direction of the spine portion, wherein the rings respectively comprise two or more split ring parts, two split ring parts of the two or more split ring parts are connected to the spine portion on respective sides of the spine portion by thin hinges, and engaging portions are formed on respective ends, opposite to the spine portion, of one or more split ring parts connected to the spine portion, for binding sheets of paper by engaging the engaging portions; wherein the spine portion is formed so that, when two or more of the binders are stacked, a front face of the spine portion of one of stacked binders is brought into contact with a back face of the spine portion of another of the stacked binders; a depression formed on one of a front and a back of the spine portion; and a projection formed on the other of the front and the back of the spine portion, the depression is engaged by the projection so that a plurality of binders are connected in a stacked condition.