| 摘要 |
An expansion device for a refrigeration system, piston therefor and methods of making the same are provided, the expansion device comprising a housing having opposed ports for coupling the device in the system and being separated from each other by an internal valve seat of the housing, and a movable piston disposed in the housing and having a first end surface adapted to engage against the valve seat to tend to close the same when the piston is disposed in a first position thereof in the housing, the housing having an annular shoulder, the piston having a second end surface for engaging against the shoulder when the piston is disposed in a second position thereof in the housing, the piston having a passage passing therethrough and through the end surfaces thereof for interconnecting the opposed ports together in a restricted manner when the piston is in the first position thereof, the piston having an outer peripheral surface interconnecting the end surfaces together and being provided with a plurality of grooves therein for interconnecting the opposed ports together in a substantially nonrestricted manner when the piston is in the second position thereof, the piston comprising a one-piece member of polymeric material, the first end surface of the piston comprising a substantially hemispherical section that is the part thereof that is adapted to engage against the valve seat when the piston is in the first position thereof.
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