GB1309272A - Electrical switches and to coding keyboards using such switches - Google Patents

Abstract

1309272 Keyboards; coding MECHANICAL ENTERPRISES Inc 6 Oct 1970 [15 Oct 1969] 47512/70 Heading G4H [Also in Divisions B6 and H1] A deformable, resilient tube 46 contains a conducting liquid (mercury) and when edge 58 on actuator 42 crimps portion 50 of tube 46 the conducting liquid is parted to break the circuit between the ends of tube 46. Actuator 42 has a push-button 64 on its upper end and in the normal position it is urged upwards by spring 66 so that in the normal position there is an open circuit between the ends of tube 46, the circuit being closed when push-button 64 is depressed. Tube 46 has on its ends sleeves 56 having contacts 52, 54 which fit into holes 118, 120 in a block 74, a spring clip 94 fitting over block 74 such that contact 52 engages the lower limb 98 of clip 94, contact 54 engaging a strip conductor 88a, Fig. 4, on a flexible tape 84 below block 74 carrying an array of parallel conductors 88, also in Fig. 6 (not shown). Spring clip 94 has extensions 104 which overlie holes 80 in block 74, a number of conductive elements 76, 78 fitting in prearranged pattern in some or all of holes 80, being engaged at their upper ends by extensions 104 and contacting at their lower ends some of conductors 88 on strip 84. Some of elements 76, 78 may consist of resistors such as 78a and diodes such as 78b. The electrical circuit, when tube 46 is conducting, is from element 88a, through contact 54, tube 46, contact 52, clip 94, extensions 104 and elements 76, 78 to conductors 88. Ten of these switches are clipped into a keyboard providing an input to a computer &c. and the arrangement and composition of elements 76, 78 gives a coded input to the computer when push-buttons 64 are depressed. There may be bowed strip springs 140, Figs. 9, 10 (not shown), snapping overcentre when push-buttons 64 are depressed to give a positive feel. Instead of knife edge 58 on actuator 42, tube 46 may be crimped by a coil spring 156, Fig. 11 (not shown), suspended from actuator 42. The keyboard comprises a frame 22 in which the switches are mounted by projections 72 clipping into grooves 136, 138 on walls 132, 134, 135 on frame 22 and flexible tape 84 carrying conductors 88 is secured to frame 22 by adhesive, tape 84 extending along one step in the frame and bent through two forty-five degree bends at its end and back along the next step &c., the bends being covered by insulating tape 133. Push-buttons 64 bear indicia.