| 摘要 |
1,169,457. Typewriters &c. WIRTH, GALLO & CO. 13 Jan., 1967 [31 Jan., 1966], No. 1847/67. Heading B6F. In a calculating machine the banks of key levers 4, Fig. 1, are provided with transparent key buttons 8 which constitute lenses whose focal lengths correspond to the distance between the lower surfaces of the lenses and a guide plate 9 so that in the undepressed state of the keys the characters associated with the keys and, which are provided on the guide plate below the key buttons, are rendered indistinct due to excessive magnification, Fig. 3, and in the depressed state of the keys are rendered visible on account of the fact that the flat lower surfaces of the lenses are in contact with the guide plate. In another embodiment the key button is made from two components, an upper concavoconvex lens 11, Fig. 8, and a lower plano-convex lens 12 whose lower planar surface 10, is provided with parallel ribs to enhance the effect of rendering the character indistinct in the undepressed state of the key. The ribs may be replaced by a matt undersurface. |
