Patent GB-855127-A (GB)
Title: Improvements in typewriters
IPC: B41J19/36
Filed: 1957-08-26
Abstract: 855,127. Typewriters. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 26, 1957 [Aug. 28, 1956], No. 26821/57. Class 100(4) Machines with types upon spherical surfaces; type-actions using auxiliary power. In a typewriter of the type having a single-element printing head 80 which moves across the paper and is moved to effect imprinting, the printing head 80 is set in position by a type-action which includes a key-actuated interposer 11 which is engaged by a power drive and which operates cam bars 32, 33 that transmit selective movement to the printing head 80. Upon depression of a key, a crank 14 engages a lip of its associated interposer 11 and this depresses a bail 18, rocks a bell-crank 19, causes electrical contacts to close, a solenoid 25 to be energised, and through linkage 27-30, a bail 31 forming the power drive for the interposers 11 to engage the depending end part of the depressed interposer 11. forward movement of the interposer engages the two cam bars 32, 33, which by a series of tapes and pulleys, and a letter-space compensating arrangement 58, selectively tilt and rotate the printing head 80. Towards the end of the travel of the bail 31 it closes contacts 90 to cause operation of a solenoid 92. This pivots a power bar 99 and operates a bracket 100 to effect a printing impression stroke of the printing head 80. At the end of the travel of the bail 31 arm 22 is engaged and contacts 23 release bail 31 which returns by spring action. A homing mechanism, Fig. 5 (not shown) returns the printing head to initial position when printing cycle is complete. Key interlocks. Should a second key 10 be depressed before completion of the printing cycle begun by a first key, the operation of the first printing cycle is not interrupted. The second interposer 11, Fig. 4, is prevented from being depressed by the power bail 31, the loosely pivoted end of the second interposer 11 is free to move downwards to relieve stress caused by the operation. Type-carriage; type wheel construction. The printing head 80 is a truncated sphere slidably fitted on to a sleeve 86, Fig. 3, which is tilted and rotated by gearing as described in Specifications 842,327 and 842,328. It is mounted on the bracket 100 pivoted in a frame 102 slidably fitted on transverse rods 105, 106. Letter-spacing. The frame 102 is urged in letter-space direction by a spring 129 inside a recess in a gear 128 and is wound up during a manual carriage return movement. Attached to the gear 128 is a pulley 126 around which a tape 111 is wound so that rotation of the gear 128 causes letterspacing movement of the frame 102 since the tape 111 is connected to it, via the pulleys 112, 114, 116, 118. The letter-space compensating arrangement 58, necessary to adjust the character selection tape control system, is moved by a tape 170 upon each letter-space. Rotation of the gear 128 is controlled by connecting gearing 130, 132 and a ratchet wheel 133 with which coacts a pawl 135 and an L shaped pawl 139 pivotal and slidable on a pivot 141. At the end of a type-action, the power bar 99 moves an arm 150 to close contacts 152. This causes solenoid 154 to energise which, via linkage 156, 158, 160, 162, pivots the L pawl 139 which engages the ratchet 133 and pivots the pawl 135 away from ratchet: ratchet 133 thus moves clockwise moving pawl 139 to the right by an amount limited by a pin 136 in a slot. When contacts 152 open, pawl 139 is restored and pawl 135 is reseated in the next tooth of the ratchet 133 which is urged to the right until the pawl 135 is stopped by the pin 136. Pawl 139 moves to its lefthand rest position by a spring 140. Specification 755,978 also is referred to.