| 摘要 |
A regulator for maintaining a constant partial vacuum in a region includes a path, through which fluid passes from the region to a vacuum source, and a piston (2) movably mounted at a constriction point (30). The piston has a frontal face (15), exposed to fluid in the path upstream of the constriction point (30). A piston distal face (16), exposed to a reference pressure, such as the pressure of region and piston weight tends to widen the path at the constriction point (30). A force is exerted on the piston by a spring (21) under compression, in a direction that tends to narrow the path at the constriction point. A buffering gas, introduced to the area between the piston's skirt (29) and the piston mounting structure (65), may be used to keep fumes from backing up into the region and/or to provide a bearing. |
