Patent GB-794280-A (GB)
Title: Proportional letter feed mechanism for typewriting machines
IPC: B41J19/32
Filed: 1955-11-23
Abstract: 794,280. Typewriters. UNDERWOOD CORPORATION. Nov. 23, 1955 [Nov. 29, 1954], No. 33549/55. Class 100(4) A typewriter has a letter feeding carriage 23, a rack 31 connected to the carriage and constantly urged in letter spacing direction, a single dog 40 movable into and out of engagement with the rack and in a direction counter to letter spacing direction, means 46 to urge the dog into engagement with the rack to prevent movement thereof and to bias it in the direction counter to letter spacing direction, and means, comprising a series of elements 62-65, selectively operable to move the dog free of the rack and guide it for variable extents of travel in the counter direction, to effect new engagements of the dog with the rack a variable number of rack teeth away in the counter direction. Actuation of a type bar 10 raises an appropriate slide 62-65 and then swings that slide rearwardly to disengage the dog 40, which is moved rightwardly until tongue 67 clears the actuated .slide, whereupon port 66 of the dog engages an associated stop 82-85 and spring 46 reengages the dog with the rack. At the time the dog is released the carriage is at rest and due to its inertia remains so for a small interval of time, sufficient for the dog to be re-engaged. The position of slides 62- 65 and stops 82-85 lengthwise of the carriage is such that when actuated they result in the dog moving two, three, four, and five increments along the rack respectively. The power typing mechanism is of known type, wherein each type bar is operated by a cyclic actuator 12 via mechanism as shown in Fig. 1, and the carriage is urged leftwardly along trackway 22 by a spring motor. The rack 31, which is resiliently mounted on the carriage comprises three co-extensive bars 33, with coarsely spaced teeth 32 connected together so as to form a composite rack with finely spaced teeth. When a type bar is operated its actuator 12 engages a projection 106 on the appropriate one of a series of bars 102, 103, .104, 105, and that bar is depressed bodily because of the arrangement of levers <SP>111</SP> and pins and slots 108, 110. Movement of a bar 102-105 operates on associated lever 132, 133, 134, 135 which in turn operates a related actuator 122, 123, 124, 125 so that on arm 129 actuates on associated lever 152, 153, 154, 155 and the latter via a wire 156 swings a related bell crank 52, 53, 54, 55. The inward arm of the bell crank 52-55 raises a slide 62-65 through opening 48, and the slide, via a fork and tongue connection 93 and arm 92 raises a stop 82-85. Stops 82-85, which are arranged at different positions lengthwise of the rack, move in slots 88 and when moved upwardly become latched in the raised position. The type bar in the last part of its movement acts via heel 68, universal bar 70, rockers 71, 74, and ledge 75 to move the displaced slide 62-65 rearwardly to disengage the dog. Stop 82-85 is unlatched by dog 40 at the end of its lengthwise movement, and returned, with slide 62-65, by a spring 61. Movement of the case shift body 163 acts via link 164, arm 180, shaft 181, and cam 179 to displace plate 107, with bars 102-105, rightwardly, Fig. 5, and so positiop different lugs 106 on the bars 102-105 beneath actuators 12. Expanded spacing may be obtained by replacing the rigid pivot 44 of the dog 40 with a pivot 165, Fig. 11, which may be moved one increment lengthwise of the rack by a hand-lever 168, so that feed movements of three, four, five, or six increments are imparted. In a modified construction the upper ends of stops 82-85 individually, and the upper ends of slides 62-65 collectively, are finely adjustable by means of abutment screws. In a modified dog 40, spring 46 is replaced by two springs, one acting parallel to the rack, and the other at right angles thereto. Specification 635,916 is referred to.