A key switch assembly for a computer keyboard, said key switch assembly comprising:
- a base board having a front part formed with a first slide retainer unit and a rear part formed with a first pivot retainer unit, said first slide retainer unit including a spaced pair of slide retainer plates which project upwardly from said base board, each of said slide retainer plates having a vertical portion and a wider lateral horizontal portion on a top end of said vertical portion and defining a slide recess with said base board, said first pivot retainer unit including a spaced pair of pivot retainer plates which project upwardly from said base board, each of said pivot retainer plates including an upright portion and a rearwardly projecting portion on a top end of said upright portion, said first pivot retainer unit further including a stop projection which projects upwardly from said base board and which is disposed between said pivot retainer plates, said stop projection being disposed posteriorly of said pivot retainer plates to define a clearance between said stop projection and rear sides of said upright portions of said pivot retainer plates, said rearwardly projecting portion of each of said pivot retainer plates forming a restricted entrance to said clearance;
- a membrane circuit layer superimposed on said base board and formed with a pair of first openings for extension of said slide retainer plates therethrough, and a set of second openings for extension of said pivot retainer plates and said stop projection therethrough, said membrane circuit layer having an electrical contact;
- an insulating layer formed from a first material and superimposed on said membrane circuit layer, said insulating layer being formed with a pair of third openings aligned respectively with said first openings to permit extension of said slide retainer plates therethrough, a set of fourth openings aligned respectively with said second openings for extension of said pivot retainer plates and said stop projection therethrough, and a through hole surrounded by said third and fourth openings;
- an upright hollow biasing member formed from a second material different from said first material, said first material being less resilient and being less susceptible to deformation than said second material, said biasing member being disposed on said insulating layer and having an open bottom end fixed to a periphery of said through hole in said insulating layer, and a top end;
- a scissors-type key cap support including first and second support levers with upper and lower portions, and intermediate portions that are coupled rotatably about a pivot axis, said first support lever having a U-shaped frame section with two parallel arms and a transverse connecting portion interconnecting said parallel arms, said lower portion of said first support lever being formed with an opposite pair of pivot shafts which project outwardly from said parallel arms and which are forced into said clearance via said restricted entrances for pivotal retention on said base board by said pivot retainer plates, said transverse connecting portion being formed with a rearwardly projecting tab which abuts turnably against said stop projection on said base board, said second support lever having a U-shaped frame with parallel rods, said lower portion of said second support lever being formed with an opposite pair of outward slide shafts which project outwardly from said parallel rods and which extend respectively into said slide recesses for slidable retention on said base board;
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- a key cap having a bottom side formed with a second slide retainer unit for retaining slidably said upper portion of said first support lever, and a second pivot retainer unit for retaining pivotally said upper portion of said second support lever, said key cap abutting against said top end of said biasing member so as to be biased upwardly by said biasing member, said key cap being depressible to compress said biasing member and permit said biasing member to contact said electrical contact and enable said membrane circuit layer to produce an electrical signal.