| 摘要 |
A housing is formed with a cylinder and with an inlet opening communicating with said cylinder. A stationary wall extends across the cross-section of said cylinder and is spaced from said inlet opening in the axial direction of said cylinder. The housing and wall are formed with an inlet opening which communicates with said cylinder and is spaced from said inlet opening in the axial direction of said cylinder on the same side of said inlet opening as said wall. A discharge piston is slidably mounted in said cylinder for movement between first and second limiting positions and arranged to define with said stationary wall a metering chamber which communicates with said inlet and outlet openings when said piston is in said first limiting position and to engage said stationary wall and close said inlet opening when said piston is in said second limiting position. A valve is arranged to control said outlet opening, closing it when the piston is withdrawn to unblock the inlet opening.
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