| 摘要 |
A hydraulic positioner 10 comprises a cylinder 12, a piston chamber 32 in said cylinder closed at one end by an axially displaceable gland 24, a piston 30 axially reciprocable in said first chamber, a rod 16 axially connected to said piston and slidable through said gland, said rod moveable with said piston between an extended and a compressed condition, hydraulic fluid in said piston chamber, valve means 40 in said piston actuatable for allowing flow of said fluid across said piston, said valve means being normally closed for locking said piston and said rod against movement in said cylinder, first spring means 18 urging said rod to said extended condition, and second spring means 74 urging said gland against said fluid to compensate for changes in fluid volume in said chamber. <IMAGE>
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