Patent GB-998500-A (GB)
Title: Improved key operated electrical switching device
IPC: H01H1/24
Filed: 1963-06-27
Abstract: 998,500. Typewriters. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 27, 1963 [June 29, 1962], No. 25514/63. Heading B6F. [Also in Divisions G4, H2 and H4] A typewriter key 10, Fig. 1, operates an electrical switching device, which generates binary coded signals for a character associated with the key and the device includes a longitudinal electrically conductive corrugated spring 13, Fig. 2, disposed between a first insulating plate 24 and a second insulating plate 14 having a plurality of separate electrical conductors 14a . . . 14g embedded therein so that a conductor corresponds to a respective peak in the corrugated spring, the arrangement being such that the peaks of the corrugations contact the conductors on the depression of the key, whereby the spring is flexed and the height of the corrugations is increased to establish an electrical connection between the conductors embedded in the second plate 14 and the spring 13. Keyboards: key actions: spacing-key actions. The keyboard, which is intended to generate six-bit coded electrical signals is capable of accommodating sixty-three different controls, includes a plurality of keys 10, Fig. 1, and a letter space-bar 11 each associated with a slide 12, which on depression of a key moves into a slot 10b, Figs. 2, to cause a corrugated contactor spring 13, associated therewith by an insulating block 23, to flex and engage selected conductors embedded in a circuit board 14 (Fig. 3, not shown), which overlies all the contactor springs 13 and provides different circuit outputs for each key. All the springs are hooked over a common electrical bus 25 and the peaks of the corrugated springs establish seven parallel circuits on making contact with the seven conductors 14a. . . 14g, the first conductor 14a projecting through the circuit board 14 and extending the length of the keyboard to coact with the springs 13 to provide a synchronizing or a start pulse, conventional in telegraph type codes. In another embodiment of the switching device (Fig. 7, not shown), the corrugated spring 13 is replaced by a conductive, straight ribbon 41, which is guided in a sinuous path over fixed guide pins 40a . . . 40n so as to provide the peaks and troughs of the preformed contactor spring. A compression spring 42 is provided to force the ribbon into its sinuous pattern to effect the circuit connections. Key construction.-Each key 10, Fig. 2, includes a key shank 10a of rectangular crosssection journalled for sliding movement in a main frame 20 and spaced sub-frame 22 and a compression spring 21, pocketed in a counterbore 50b, biasing the key upwardly. A slot 10b in the shank receives the slide 12 when the key is depressed, the shank being straddled by an interposer spring 27 attached to a tab 10c at one end, the other end being necked down so that its width is slightly less than that of the width of the rectangular opening in the slide 12. The spring acts as an interposer to prevent the slide 12 from being tripped twice upon continued depression of the same key. Key interlocks: special key action.-The interlock for preventing simultaneous depression of a number of keys comprises a series of laminated bands, or ribbons 18a. . . 18d, Fig. 1, threaded through openings in the key shanks 10a and guides 30, the motion of each band being transmitted to the next row by bell-cranks 20a. . . 20c, and anchors 19a, 19b fixing the total effective length of the bands. To accommodate one depressed key 10, the band is permitted one bight 32 (Fig. 5, not shown), which when all keys are in the raised position is absorbed by a downwardly-biased dummy key 31, Fig. 6. If anyone of the keys is depressed the ribbon 18c will be tensioned to straighten the bight 32, thus moving the dummy key 31 upwardly and permitting a new bight to be formed by the depression of the key 10, which will be latched in the depressed position by its associated slide 12, until the slide is restored by the common bail 15. Upon restoration of the slide 12 the spring 27 will enter the rectangular opening in the slide 12 and prevent the slide from being tripped repeatedly with the key in the depressed position. When the key is released the spring is withdrawn from the opening on the slide 12, which then bears directly on the shank. In order to straighten the bight in the ribbon as the key 10 restores a push-rod 17a, Fig. 6, on the solenoid 16a is provided with a shouldered portion 33, which when the solenoid 16a resets to the left trips over a bell-crank 34 without moving it due to the broken lever action of the associated dog 34a pivoted to one arm of the bell-crank. On return action of the solenoid under the action of spring 35a the portion 33 picks up the dog 34a which pivots the bellcrank 34 clockwise and the bell-crank then translates a downward bias to the dummy key 31 by engaging the pinned connection 37.