GB439485A - Improvements in or relating to typewriters - Google Patents

Abstract

439,485. Typewriters. HAAS, O., 15, Rheinstrasse, Wiesbaden, Germany. March 9, 1934, No. 7613. Convention date, March 9, 1933. [Class 100 (iv)] Type-lever machines.-In a typewriter having intermediate levers for transmitting motion from the key-levers to the type-levers, the latter being pivoted in a segment defining a plane inclined to the base-plane, the bearing points of the intermediate levers lie on a curve defining a plane which is at an angle to the base-plane and cuts the plane of the typelever segment above the base-plane. The arrangement provides a portable typewriter of low overall height, with a substantially even pressure overall the keys and without twists and friction at the pivots of the intermediate and type-levers. To attain the first object, the central type-lever is arranged to lie at the same angle (in the reverse direction) in its position of rest as in the striking position, and the intermediate levers are arranged to lie and move in planes closely parallel to the type-levers, so that in the striking position they can occupy the space formerly occupied by the type-levers. For simplicity in manufacture, the type and intermediate lever segments 2, 12 are arranged as circular combs in a bearing element which comprises also the key-lever bearing 14, which may be formed by spray-casting, and can be lifted bodily out of the machine. To attain an even touch, the line joining two corresponding bearing points 6, 8 should be of constant length and be horizontal from one end of the segments to the other. To avoid friction, a plane through the axis of the type-lever segment and through a given bearing must pass also through the corresponding intermediate-lever hearing. By mathematical analysis it is found that, for a given angle of inclination alpha of the typelever bearing, radius r of the typelever bearing, and radius d + r of the intermediate lever bearing, the intermediate-lever bearing must be tilted at angle x where sin x = DS. sin (90-alpha) / O2S and DS and O2S can be calculated from r and d. If this condition is fulfilled and the segments are arranged so that, if they were rotated about their intersections with the base-plane into the base-plane, they would be concentric, the desiderata will be approximately achieved for all the lever systems. If the intermediate-lever segment is made elliptical so as to obtain a lower construction one or other of the conditions referred to above must be abandoned and less efficient working will result.