GB1375946A - Actuating mechanisms for electrical circuit components - Google Patents

Abstract

1375946 Retractive switches; transformers HEWLITT-PACKARD CO 1 Feb 1972 [15 April 1971] 4728/72 Headings H1N and HIT An actuating mechanism comprises a key 12 with parallel shafts 14, 16 attached to it, a guide 22 for shafts 14, 16, means 26, 44 for coacting with shaft 14 to give a signal when key 12 is depressed and resilient means coacting with shaft 16 to give a sudden change in resilience in response to movement of shaft 16 providing tactile feedback to the user. As shown, when key 12 is depressed shaft 14 depresses plate 26 attached to plate 24 by retractive springs 28a, 28b, to bring plate 26 nearer to printed circuit transformer 44 formed by two spirals 46, 48 to alter the mutual inductance between spirals 46, 48, to provide a signal. A piece of ferrite may be attached to plate 26. Instead of having a transformer 44, there could be a capacitor or plate 26 could bridge contacts 45, 47, Fig. 1b, on printed circuit board 40. When key 12 is depressed arid shaft 14 depresses plate 26, shaft 16 engages superimposed cantilever strips 38 and 30 which are resilient and which deflect downwards and the user encounters increasingly greater resistance until the tip of shaft 16 moves past the contilevers 38, 30 and key 12 snaps down, cantilever 38 entering a recess in shaft 16, the user feeling the sudden change in resilience. When key 12 is released, springs 28a, 28b return key 12 upwards and shaft 16 encounters resistance only from the tip of cantilever 38 which is overcome by springs 28a, 28b. There may be a plurality of mechanisms on the same keyboard, and keys 12 may be retained in the keyboard by recesses 15 on shafts 14 engaging protrusions in holes 18. In a second embodiment, Figs. 3a, 3b, key 12 is replaced by a key 62 having a hollow shaft 64 to depress plate 26 towards transformer, etc., 44, and the resistance to movement is provided by a shaft 66 inside shaft 64, shaft 66 engaging deflector member 76 on buckled spring 70, spring 70 suddenly buckling in the opposite direction at the appropriate point of depression of key 12 to provide the tactile feedback. Once buckled in the opposite direction, spring 70 remains in that position since it is bi-stable until key 62 is again depressed when spring 70 returns to the position in Fig. 3a.