Patent GB-1026658-A (GB)
Title: Wear compensation apparatus for print mechanisms
IPC: B41J1/60
Filed: 1964-12-21
Abstract: 1,026,658. Typewriters. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 21, 1964 [Jan. 30, 1964], No. 51760/64. Addition to 1,026,659. Heading B6F. Machines with types upon spherical surfaces; type-selecting mechanisms, power-assisted type actions.-A type writer having provision for adjustment of wear in the character selection mechanism comprises a detachable truncated spherical type head 11, Fig. 3, a spindle 12 rotatable in both directions and on which the type head is mounted, a pulley 24 biased to rotate in one direction only relatively to the spindle and carrying a flexible tape 30 connected to a rotary character selection mechanism 45, Fig. 1, a spring clutch 19 interconnecting the pulley and spindle for joint rotation and a stop 60 adapted to be engaged by an arm 61 movable with the spindle whereby the clutch 19 is permitted to slip and the pulley 24 is able to rotate relatively to the type head under the action of a bias spring 62 to take up any slack in the tape due to wear. The rotary selection mechanism comprises selection links 46, 47 and 52 articulated to floating members 48, 50, respectively, with the latter connected through a link 51 to one end of a balance lever 44, the other end of which is pivotally connected to a link 53, which is normal by stationary, but may be moved vertically a predetermined distance. Intermediate its length the balance lever is articulated to a bell-crank lever 42, which when actuated displaces angularly a pivotal arm 32 through the intermediary of a link 41. Selective displacement of one or more of the selective links 46, 47, 52 causes hooked portions of the links to be engaged by a bail 54, whereby the bell-crank 42 rocks a distance equal to the sum of the distances obtained by the individual selecting links said sum varying between one to five units. With the link 53 in the position shown in Fig. 1, the bell-crank rocks counterclockwise to rotate the type head 11 in a counterclockwise direction by pivoting arm 32 and pulley 31 and pulling on the tape 30. Clockwise rotary selection is effected by raising the link 53 to a predetermined position by a cam (not shown) and the unit displacement determined by the links 46, 47, 52 is effected, on clockwise pivoting of the arm 32, by a spiral bias spring 27, which is attached at one end to a rocker 16 and at the other end to a spring arbor 17 fast with the spindle 12. The type head is tilted for selection of the row of character by a separate mechanism (not shown). The rotary type selection mechanism is actuated in response to depression of a keylever or by received signals controlling the operation of solenoids (not shown) in a manner known per se. Case-shift mechanism.-To select upper-case characters the typewriter is provided with a case-shift arm 34, Fig. 2, having a cam follower roller 56 which engages a case-shift cam 57. The cam is rotated in response to a case-shift signal and causes clockwise pivotal movement of the arm 34 about pivot point 58 causing the type head 11 to rotate in an anticlockwise direction through 180 degrees, the upper-case characters being formed on the other half of the type head. Wear compensating apparatus.-The wear compensating apparatus 10, Fig. 3, is designed to compensate for any wear in the rotary character selection mechanism 45, Fig. 1, e.g. dilation of tape 30, and becomes effective when the type head 11 is rotated clockwise by five units and the case shift mechanism has not been actuated. The apparatus comprises a clutch means including the clutch spring 19 so designed that with a spiral spring 27 exerting a clockwise biasing force on an arbor 17 and the tape 30 exerting an anticlockwise pulling force on the pulley 24 the convolutions of the clutch spring 19 tightly engage the arbor 17 and the pulley 24. When wear has taken place and the spiral spring 27 has moved the type head 11 five units in a clockwise direction, in response to the depression of a key, a tab 61 on the arbor 17 engages a stop plate 60 on the plate 16 removing one of the opposing forces on the clutch spring 19 which unwinds slightly to release the pulley 24. The pulley 24 is then rotated in a clockwise direction by a helper spring 62 relative to a spindle 12 carrying the type head 11 until all slack in the tape 30 is taken up. As the selection mechanism 45 is de-energized and the arbor 17 begins to rotate counterclockwise to its home position, the tab 61 moves from the stop plate 60 and the clutch spring 19 engages the pulley 24 in the adjusted position.