| 摘要 |
A valve sleeve is made from a tube having smooth inner and outer diametrical surfaces by forming a shallow channel on the tube so that a channelled region of the tube is thinner than other regions of the tube. The tube is confined in a sleeve whose inner peripheral surface conforms with the tube's outer diametrical surface, but the sleeve's inner peripheral surface also defines a gap with the channelled region of the tube. Next, the tube is pressurized to deform the channelled region outward into the gap. As a result, there are both a concavity on the inner diametrical surface of the tube and a smoothly surfaced transition between the concavity and the other regions. Finally, the tube is removed from the sleeve and a port aperture is drilled in the radially outer part of the concavity. As an alternate method, a tube of constant tube wall thickness may be placed in an internally channelled confinement and then pressurized so as to distend regions of the tube wall outward. The tube is removed from the sleeve and holes are drilled in the distended regions.
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