Patent GB-925011-A (GB)
Title: Wear compensating device for link mechanism
IPC: B41J1/60
Filed: 1961-04-26
Abstract: 925,011. Typewriters. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 26, 1961 [May 2, 1960], No. 15054/61. Class 100 (4). [Also in Group XXIV] In a typewriter, e.g. as described in Specification 873,920, wherein a printing head 4 with a part-spherical surface is rotated against spring action from an initial position by a band 3 to position a type to be printed, and the band is operated by a pulley 27 on a lever 1 connected by a link 2 to mechanism which controls the movement of the lever 1, the lever is constructed so that compensation is automatically effected for inaccuracy in the positioning of the type due to wear in the parts. The lever 1 includes arms 35 pivoted about a shaft 25 mounted on a bracket 54, and carrying the pulley 27 at their upper end by means of a bolt 47, Fig. 3. On the head of the bolt 47 is an eccentric pin 50 which, at the end of clockwise movement of the arms 35 first engages a leaf-spring 51, Fig. 4 (not shown), on the frame 52 and then abuts against the frame, such movement causing rotation of the head 4 to the fifth letter of a row thereon, i.e. a distance of five units. Mounted on the shaft 25 between the arms 35 is a member 56, Fig. 3, with arms 60, 63, 66 and an eccentric hub 57, a spring 64 connecting the arm 63 to a stud 38 on the arms 35 so that the arm 60 is held against an eccentrically-mounted stop 61 on the arms 35. The arm 66 engages the bracket 54 in certain positions of the mechanism as referred to later. Pivoted on the hub 57 is a two-part lever, one part 76 having a flanged hole 70 fitting on the hub and an arm 77 connected by a spring 78 to the stud 38, and the other part 72 having a slot 71 fitting over the flange 70 and being connected to the part 76 by a bolt 74 passing through a narrow lower part 73 of the slot 71 into a hole 75 in the part 76. The lever 72, 76, which is subject to the action of a spring 87, Fig. 1, is adjustable in length by means of the bolt-and-slot arrangement 73, 74, and is pivoted at its lower end to the link 2 connected to mechanism controlling the movement of the link 2 and lever 1 so as to position the type face required to be printed. A roller 82 rides freely in slots 80 in the arms 35 and, before any wear in the parts occurs, is held at the top of the slot by an inclined surface 86 on an arm 68 of the lever part 76. Initially the length of the lever 72, 76 and the position of the eccentric pin 50 so adjusted that the requisite movement of the type-head is attained. Just after four units of such movement of the typehead, the pin 50 engages the leaf-spring 51, Fig. 4 (not shown), and the arm 66 engages the bracket 54 so that the lever 72, 76 now rotates about the centre of eccentric hub 57, i.e. its lower arm is shortened and its upper arm lengthened. The fifth position of movement is always correctly determined by the engagement of the eccentric pin 50 with the frame 52, but if wear has occurred, this engagement takes place before the link 2 has completed its movement. Further movement of the link then causes the lever 72, 76 to move clockwise relatively to the arms 35 thus allowing the roller 82 to drop in the slot 80 a distance corresponding to such movement, and so setting the lever in relation to the arms to compensate for the wear. When sufficient wear to cause the roller to drop to the bottom of the slot has occurred, manual resetting has to be effected.