| 摘要 |
<p>A long-stroke push-button switch has contacts which close in the middle of the travel and remain closed through the last half of the travel. The switch has a keytop (12) and a lever (42) interconnected by a stiff spring (38). One end of the lever is pivotably mounted (at 92) in the switch housing. A downwardly projecting actuator (84) located on the underside of the lever rests upon the top of a normally-open snap-dome switch (78, 80). The axis of the snap-dome switch is located off-centre with respect to the centre line of the keytop. When the keytop (12) is depressed, the spring (38) is compressed during the first halt of the keytop travel. When the spring is partially compressed, further pressure on the keytop causes the lever (42) to pivot and close the snap-dome switch contacts (78, 80) in the middle of the travel. Continued pressure on the keytop (12) further compresses the spring and allows the keytop to move through the last half of the travel after the contacts have closed.</p> |
