Patent GB-446321-A (GB)
Title: Improvements in line-spacing mechanism for typewriting machines
IPC: B41J19/84
Filed: 1935-08-10
Abstract: 446,321. Typewriters. FAIRWEATHER, W. C., 65, Chancery Lane, London.-(Underwood Elliott Fisher Co., 342, Madison Avenue, New York, U.S.A.) Aug. 10, 1935, No. 22610. [Class 100 (iv)] Line-spacing mechanism.-In. mechanism comprising a key for determining the line-space unit, and another, independently adjustable key for determining the number of units in the line-space movement, the line-space wheel is mounted on a counter-shaft parallel to the platen-axle, and is engaged by a pawl carried by an arm which is operated from the line-space lever by movement-multiplying gear including a rack, and the line-space wheel drives a small gear engaging with a large one secured to the platen-axle. The line-space lever 10, Figs. 6 and 8, is pivoted to the carriage at 12 and actuates a sliding rack 21 through a knuckle joint 20. The rack 21 engages a gearsegment 24 on a pawl-driving arm 31, carrying a pivoted pawl 29 and loosely mounted on a countershaft 28, to which is secured a finetoothed ratchet-wheel 25 and gear 26, which latter. meshes with a large gear 27 on the platen-axle 16. The pawl is drawn towards the wheel 25 by a spring 56. The line-space movement is thus magnified up to the ratchetwheel 25 and again reduced to the platen-axle, so that the small teeth of the ratchet-wheel can give only an insignificant inaccuracy to the final platen-movement. The parts are compactly arranged, the gear-wheels being closely spaced and the rack 21 overlying the arm 31. The pawl 29 is held from the ratchetwheel during part of its stroke by a rotatable cam 52, which is adjusted by an integral gearsegment 51 meshing with a slidable rack 50. The drive-stroke of the pawl is limited by a fixed overthrow-stop 33 which arrests the pawl and presses it into contact with the ratchetwheel 25. The rack 50 is guided by a pin 59 and adjusted by a finger-lever 43, pinned to the rack at 49 and provided with an adjustable fulcrum-pin 48. The upper end of the lever projects through a slot 45 in the casing 44 and has a spring-detent 47 engaging a series of notches 46 in the side of the slot. The fulcrumpin 48 slides in a slot 63a in the lever 43 and a slot 66 in the casing wall, and is carried by a finger-lever 72, pivoted to the casing at 63c and which may be set opposite scale-marks 71 on the casing. The effective length of the lever 43 can therefore be adjusted by the lever 72, thus altering the unit of line spacing. The number of units spaced is determined by the setting of the detent 47 in the notches 46. In the zero, or extreme left-hand position of the lever 43, the slots 63a, 66 are coincident, so that the setting of the lever 72 does not affect the position of the cam 52. In an alternative construction, the pawl 29 is carried by an arm 100, 102, Fig. 16, mounted loosely on the shaft 28 and provided with a bridge 103 to engage the gear-arm 24, 101. The pawl 29 is provided with a notch 105 in which engages a tooth 104 on the arm 101. Movement of the arm 100, 102 is retarded by spring-fingers 106 engaging a groove 107, so that when the arm 24, 101 is actuated by the rack 21, the tooth 104 swings the pawl into engagement with the wheel 25. During the return movement, the pawl is disengaged by the same means, and the pawl arm is carried along by engagement of the arm 101 and bridge 103.