Various-sized-cassette housing shelf

A cassette housing shelf for selectively accommodating relatively large-sized and small-sized cassettes which respectively have relatively large and small widths, comprising:

• a horizontal shelf-plate having a cassette-bearing surface with parallel opposite side margins;
• upstanding side walls extending from said side margins of the shelf plate and between which a cassette-receiving space is defined above said cassette-bearing surface with an inlet at one end of said shelf plate, said side walls being spaced apart by a distance approximately equal to said relatively large width of the large-sized cassette so that the latter is laterally guided by said side walls when inserted through said inlet into said cassette-receiving space;
• an elongated guiding element extending generally parallel to said side walls and being movable between a raised operative position above said cassette-bearing surface and a depressed inoperative position submerged relative to said cassette-bearing surface, said guiding element in said operative position being spaced from one of said side walls by a distance approximately equal to said relatively small width of the small-sized cassette so that the latter can be laterally guided between said guiding element and said one side wall when said small-sized cassette is inserted through said inlet into said cassette-receiving space;
• first and second sensing elements disposed adjacent said inlet at said one side wall and the other of said side walls, respectively, and being movable independently of each other between inner positions where said sensing elements project beyond said side walls at least partly into said cassette-receiving space and outer positions withdrawn from said space;
• means yieldably urging said sensing elements to said inner positions thereof;
• means responsive to movement of said second sensing element to said inner position thereof for urging said guiding element to said raised operative position and for permitting said guiding element to move to said depressed inoperative position when said second sensing element is moved to said outer position thereof;
• means engageable with said guiding element for blocking movement of the latter to said depressed inoperative position;
• and means responsive to movement of said first sensing element from said inner position to said outer position thereof for disengaging from said guiding element said means for blocking movement of the latter to said depressed inoperative position so that said guiding element is thereby permitted to move to said depressed inoperative position only when a large-sized cassette, in being inserted through said inlet into said cassette-receiving space, simultaneously displaces said first and second sensing elements to said outer positions thereof.