| 摘要 |
A stator has a cylindrical bore. A cylindrical rotor fits in the bore with a clearance. A circumferential groove varying in depth is formed around the circumference of the rotor. Ball bearings support the rotor for rotation in spaced relationship from the bore without a seal. Axially elongated inlet and outlet slots are formed in the stator so as to communicate with the groove at circumferentially spaced points. Vent holes lead from the bore to the exterior of the stator between the inlet and outlet and the ball bearings. The valve is coupled by first and second legs of a tee connection to a patient. A third leg of the tee connection is connected by a needle valve to a vacuum source.
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