Disc cassette with slidable cover

Claim 1

A disc cassette comprising a readable information disc having a central hub for receiving a drive spindle of a drive apparatus, an envelope in which the disc is encased, said envelope comprising a pair of opposed major walls paralleling the plane of the disc and interconnected by two pairs of opposed sidewalls, at least one of the major walls having a central opening aligned with the hub of the disc, for passage of the drive spindle, an access slot, for passage of the information recording and/or reproducing means, and a retention slot adjacent said central opening opposite said access slot, said retention slot being oriented substantially perpendicular to said access slot, said retention slot having an undercut edge, first closing means movable over the outside of the envelope substantially parallel to said retention slot between a closing position and an operational position, said closing means having an opening corresponding to the central opening and an access slot corresponding to the access slot in the envelope, said opening being aligned with the central opening and said access slots likewise being aligned when said closing means is in the operational position, said closing means covering the central opening and access slot in the envelope when in the closing position, said closing means being formed with a lap offset from the plane of the major portion of the closing means, said lap being overlapped by the undercut edge of the retention slot in said envelope, whereby said lap and said undercut edge locally retain said closing means against displacement away from the envelope, said lap and said undercut edge cooperating slidably with each other.