Rollable chart

A rollable chart comprising

• a base
• a first rotatable support on said base,
• a second rotatable support on said base in spaced parallel relation to said first support,
• a web of flexible material wound on the first support and the second support and having an exposed portion between the supports
• a first pulley adjacent said first rotatable support,
• a second pulley adjacent said second rotatable support
• an endless flexible band extending around said pulleys, said band being exposed and comprising means for manually rotating said pulleys in response to manual manipulation of said band,
• first unidirectional driving means for connecting said first pulley to said first rotatable support to wind said web onto said support in response to manual movement of said band in a first direction, and second unidirectional driving means for connecting said second pulley to said second rotatable support in response to manual movement of said band in the opposite direction, each unidirectional driving means comprising
• an internally toothed surface near one end of a support,
• a disc fixed to a pulley for rotation therewith, said disc being axially adjacent said toothed surface, an inclined cam groove formed in said disc,
• a sliding pawl having a pin extending into said cam groove, and
• means for guiding the pawl radially toward and away from the internally toothed surface,
• said cam groove forcing said pawl into driving engagement with said internally toothed surface in response to rotation of its pulley in one direction, and maintaining said pawl spaced from the internally toothed surface in response to rotation of its pully in an opposite direction.