| 摘要 |
<p>A two-stage actuator comprises a pair of axially aligned bellows molded from a thermoplastic material and connected at their adjacent ends by a molded link section integal with the bellows . The other end of one of the bellows is designed to be connected to a stationary machine part while the other end of the other bellows is designed to be connected to a movable machine part. Each bellows has an accordiontype convolution section pneumatically connected through a conduit and a valve to a vacuum source so that the convolution section is axially collapsed by vacuum when applied. A link member axially extends over the convolution section of the other bellows and has an end fixed relative to the one bellows. The other end of the other bellows is in the form of an axially elongated protrusion slidably extending through an opening formed in the other end of the link member. The protrusion and the opening cooperate to form a one-way connection which allows the protrusion to be moved relative to the opening toward the one bellows but prevents the protrusion from being moved relative to the opening toward the movable machine part whereby, when the one bellows is axially collapsed, the link member and the other bellows are moved a distance toward the stationary machine part to pull the movable machine part the same distance and, when the other bellows is axially collapsed with the one bellows kept collapsed, the movable machine part is further pulled an additional distance toward the stationary machine part.</p> |
