Pushbutton structure of keyboard

A pushbutton of a keyboard includes a cap supported on a base board by a linkage comprising first and second links pivoted together whereby the cap is movable from a released to a depressed positions when depressed. Each link has upper and lower pivots respectively connected to the cap and the base board. The links have two side bars connected between the upper and lower pivots thereof. Two spring arms extend from the base board having free ends forming L-shaped offset sections receivingly engaging L-shaped recesses defined in corresponding side bars for biasing the cap toward the released position. The spring arms deform when the cap is depressed. When the spring arms are deformed to an extent, the offset sections are abruptly driven toward and impact a contact surface of the recesses, generating a sound of impact and a pulse-like reaction caused by the impact. The deformation of the spring arms helps returning the cap back to the released position when the depression is released.

What is claimed is:

1. A pushbutton comprising:

a cap having an underside with first and second pivot retaining means formed thereon;

a base board forming two spaced tabs defining aligned holes and two spring arms each having an end forming an offset section with a connection formed between the offset section and the spring arm whereby an L-shaped configuration is formed, a slot being defined in the base board;

a U-shaped first link having a first pivot pin with two first side bars extending from opposite ends of the first pivot pin, the first pivot pin being rotatably received in and retained by the first pivot retaining means of the cap, free ends of the first side bars forming second pivot pins rotatably received in and retained by the holes of the tabs of the base board, the first side bars defining aligned holes, each first side bar having a recess formed therein, the recess having a contact surface formed thereon;

a second link in the form of a rectangular frame having third and fourth pivot pins connected to each other by two second side bars, the third pivot pin being rotatably received in and retained by the second pivot retaining means of the cap and the fourth pivot pin being rotatably received in and the retained by the slot of the base board, transverse pins extending from the second side bars and rotatably receive in the holes of the first side bars to form a cross configuration;

the offset section of each spring arm being adapted to engage a portion of the recess of the corresponding first side bar to support the linkage in an un-depressed position and the spring arm being deformed responsive to the cap being depressed, the offset section being abruptly displaced to impact the contact surface of the recess responsive to the spring arm being deformed to a predetermined extent to generate a sound of impact and a pulse-like reaction, the deformed spring arm biasing the first and second links to return the cap back to un-depressed position.