Rotatable disk teaching apparatus

A demonstrative teaching apparatus for disclosing relationships between variable pie-shaped segments on a first surface and indicia corresponding to same on a second surface opposite to said first surface, said apparatus comprising:

• apparatus housing means having a front side with front side viewing means through which said variable pie-shaped segments on said first surface may be viewed, together with a rear side with rear side viewing means through which said corresponding indicia on said second surface opposite to said first surface may be viewed;
• circular disk means operably positioned for rotation within said apparatus housing means and on which first and second surfaces are respectively positioned,
• said circular disk means including, on said first surface aligned with said front side viewing means, proximate to the front side of said apparatus housing means, helical disk means substantially concentric with said circular disk means and operably attached thereto, for portraying said variable pie-shaped segments,
• said circular disk means further including, on said second surface aligned with said rear side viewing means, proximate to the rear side of said apparatus housing means, a plurality of said indicia correspondingly displaying, through said rear viewing means, values associated with the amount and position of said variable pie-shaped segments disclosed through said front viewing means;
• slotted plate means operably positioned between said helical disk means on said first surface of said circular disk means and, said front side viewing means in said front side of said apparatus housing means, for operable disclosure of said variable pie-shaped segments,
• said slotted plate means including helical disk slot means through which the outermost free end of said helical disk means protrudes in juxtaposed fashion to disclose, as desired, said variable pie-shaped segments advanced by said helical disk means, while said slotted plate means masks the remainder of said juxtaposed helical disk means and said circular disk means from view through said front side viewing means,
• said disclosed variable pie-shaped segments of said helical disk means being extendably and retractably propelled through said helical disk slot means in said slotted plate means, through the forward and rearward rotation, respectively, of said circular disk means, and in turn, said helical disk means which are operably attached to said circular disk means within said apparatus housing means;
• circular disk rotation means for enabling said forward and rearward rotation of said circular disk means, as desired, by a user to, in turn, enable variations in the amount and position of said disclosed variable pie-shaped segments displayed through said front side viewing means of said apparatus housing means, simultaneous with the disclosure of said indicia corresponding thereto, as displayed through said rear side viewing means of said apparatus housing means;
• said invention further comprising reverse rotation stopping means for limiting the extent to which said circular disk means and, in turn, said helical disk means may be reversably rotated;
• said reverse rotation stopping means comprising stop tab means having a first end operably secured to said second side of said circular disk means and a second end emanating angularly outwardly therefrom, and
• radially positioned stop arm means having a first end operably juxtaposed to and emanating from the center of the second side of said circular disk means and a second end operably affixed to said slotted plate means,
• said stop arm means engaging said stop tab means to limit the reverse rotation of said circular disk means to preclude against the inadvertent unthreading of said helical disk means from within said helical disk slot means in said slotted disk means.