Patent ID: 7946625

Claim:
A binding structure for binding a stack of sheets to form a book, comprising: a pair of hard covers each having an inner surfaces adapted to be attached to one of the sheets, an outer surface opposite to said inner surface, and an edge interconnecting said inner and outer surfaces, said hard covers being movable relative to each other between an opening position to open the book and a closing position to close the book, at least one of said hard covers having a slide groove formed between said inner and outer surfaces, and an opening communicated with said slide groove and formed in said edge; and a middle sheet member connected between said hard covers and having a lateral slide portion extending slidably into said slide groove through said opening, said middle sheet member further having a spine portion that is connected to said lateral slide portion and that is exposed between said hard covers when said hard covers are in said closing position, said spine portion sliding into said slide groove through said opening when said hard covers are in said opening position and out of said slide groove when said hard covers are in said closing position, wherein said opening is large enough to permit said spine portion to slide into said slide groove.