| 摘要 |
<p>The buttons (3) of a printed circuit keyboard are housed in an insulating, e.g. plastics, enclosure (1). The rigidity of a helical spring (8) is used to define the contact force and to provide the button return pressure. The square-section button has an internal stop shoulder (14) and a convex protrusion (4) at its lower end. The spring is set in abutment recesses (7a,7b) to rest in a convex-upward curved shape which is a monostable position. When the button is depressed, the rounded protrusion, using the space in a rectangular recess (18), forces the spring to flip downwards, bridging the switch contacts (13a,13b) on the printed circuit board. The keyboard matrix of buttons is fixed and located on the printed circuit board by lugs at the corners of the block in which the button units are fixed. The keys can be used equally well with hard and flexible circuit boards.</p> |
