Patent GB-655492-A (GB)
Title: Improvements in or relating to a case shift mechanism for typewriting machines
IPC: B41J23/12
Filed: 1948-06-21
Abstract: 655,492. Typewriters &c. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 21, 1948, No. 16606. Convention date, June 25, 1947. [Class 100 (iv)] A case-shift mechanism comprises an accelerating power shift - mechanism initially moving a plate 20 positionable into either of two case-shift positions and operative means, e.g. a spring 38, for continuing movement of the plate with a controlled decelerating restraining motion by means of a buffer mechanism. The type-levers 13 are pivoted on a basket 10 movable upwardly into a lowercase position and downwardly into an upper-case position between adjustable non-metallic stops secured on the framework 14. Movement is imparted to the basket 10 by a linkage connected to a pair of brackets 18 secured to the basket 10 by two screws 18a spaced on either side of rounded lugs 18b so that adjustment between the basket and the positionable plate 20 may be effected. The bracket 18 is connected by a link 19 to the plate 20 which moves about a pivot 21 when engaged by either of lugs 33a or 33b of an actuator member 33 according to whether the basket is being moved into upper or lower-case position. Actuator 33 is pivoted at 30a to an arm 30 which is drawn forwardly when either of two case-shift keys are depressed or released. This is effected by a link 26 pivoted on key-lever 27R, Fig. 1, and which moves anti-clockwise a lever 24e, to release a pin 24c on a cam 24a allowing the cam to receive a small rotation from a downwardly-sprung arm 24h engaging a left-hand pin 20g on the cam 24a. The cam thus engages the power roller 23 and the camcarrying lever 24 is moved with an accelerating motion anticlockwise about pivot 25a, drawing link 29 leftwardly and swinging the arm 30 clockwise. The amount of movement of lever 24 is controlled by an adjustment 25b. At the same time an extension 27a of the shift-key elevates the actuator 33 by means of a link 35 to position the lug 33a behind a pin 20b on the rocking-plate 20, so that the resulting action of the two movements turns the plate. 20 anticlockwise. A toggle-spring 38 continues rotation of plate 20 to shift the type basket into upper-case position under the control of a buffer member 34 so that it slides into position with a decelerating restraining motion. The buffer 34 is pivoted at 30a coaxially with the actuator 33 and has projecting limbs 34b, 34c, a " peardrop " opening 34e, and a rectangular opening 34d; a toggle-spring 36 isconnected from a pivot 34a on the buffer to a pin 37 secured on the framework. The buffer 34 remains in the position shown in Fig. 1 until a pin 20c on the plate 20 engages the limb 34c at about the point where the highest part of the cam 24a engages the roller 23. At this point the toggle spring 38, assisted by the weight of the basket 10, tends to continue movement of the plate and cause pin 20c to move the buffer 34 upwardly and to the right and tends to rock lever 30 in an anti-clockwise direction. As, however, the lever 30 is connected by link 29 to the cam 24a the movement of the lever 30, buffer 34 and consequently plate 20 and basket 10 is controlled in its deceleration by the shape of the cam 24a. Further rotation of the cam is prevented by the trip-lever 24e engaging a pin 24d on the cam 24a, whereupon a second pin 24g is positioned below the sprung arm 24h so that a similar action takes place when the shift-key is next operated, Fig. 7, releasing it to normal position. In addition to moving the buffer 34 backwardly the plate 20 has a further pin 20d which engages inside the top surface of the pear opening 34e and together with a snapspring 36 moves the buffer clockwise so that the limb 34b is in position to engage the pin 20b and so effect a similar buffer action when the shift-key is released. Upon the release of a shift-key, lever 24e moves clockwise into the position shown on Fig. 1, this time disengaging pin 24d and starting a similar cam action to that started when the key was depressed. The key-lever also lowers link 35, causing actuator branch 33b to engage pin 20c on plate 20, moved clockwise by the leftward impulse of the actuator. A similar snap-over of the plate 20 by the toggle-spring 38 occurs and the typebasket returns to lower-case position under control of limb 34b of the buffer 34 and the cam mechanism. Shift-lock.-A shift-lock key 42 pivoted about a point in line with the shift-key axis 28 is pivotally connected at 43a with a latch 44 pivoted at 27c to the shift-key, and when depressed moves a hooked end 43b of the latch into an opening in a plate 44. A slight downward movement of either of the shift-keys, which are interconnected by a bail 39, turns the latch clockwise to release the hook 43b from the opening and the shift-key is restored by a spring 45.