| 摘要 |
A housing includes a switch chamber and a plunger chamber communicating with the switch chamber. A plunger is slidable within the plunger chamber. Cam surfaces on the plunger operate electrical switches in the switch chamber. There is an axial channel in the plunger, and a slot through the plunger wall communicates with the channel. A vacuum passageway passes from one side of the housing, into the channel, and a solid extension of the passageway passes through the slot, and into a hole in the opposite wall of the housing. As the plunger moves in and out, the slot slides on the extension to guide to stabilize the plunger. A vent hole in the vacuum passageway opens into the channel. A sealing member slides in the channel along the axis of the plunger, alternately sealing and unsealing the vent hole as the plunger moves. A spring seated between the plunger and the sealing member permits the plunger to continue moving when the sealing member is seated in the passageway vent hole. A maze causes air passing through the switch chamber to the vent hole to turn and slow, thereby causing dust particles to settle out of it.
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