Improvements in or relating to boards for educational purposes

摘要

934,561. Endless-band educational boards. WILSON & GARDEN Ltd. Oct. 16, 1961 [Oct. 12, 1960], No. 34915/60. Class 146 (2). In a blackboard of the type comprising an endless band entrained over top and bottom rollers carried by a frame formed by spaced uprights, the bottom roller has plate 16 rotatably mounted on the ends of the spindle 12 of the roller. Each plate 16 carries a pawl 18 which engages a ratchet 22 attached to the associated wooden upright 14, thereby preventing movement of the bottom roller towards the top roller and maintaining a tension in the band. A second pawl 17 is used to hold the spindle of the bottom roller at the top of slot 13 in which it slides, while the band is entrained around the two rollers. The plate 16 is biased so that the pawl 18 is urged into engagement with the ratchet 22, a peg 23 being provided for manually releasing both pawls 17, 18, when required. In a second embodiment, Fig. 3 (not shown), the uprights are of hollow metallic form. In a third embodiment, Figs. 5 and 6 (not shown), the plate 16 is replaced by a guide plate 24 clamped in the required position by a screw clamp 27.