| 摘要 |
A measuring cup including a transparent open-ended cylinder and a metering piston mounted in the cylinder for longitudinal movement and rotational movement with respect to the cylinder. The piston includes an upper completely cylindrical measuring disc of diameter to contact the inner cylindrical surface of the cylinder. The piston also includes a lower interrupted guide disc in sufficient contacting relation to the inner surface of the cylinder to maintain the upper face of the upper disc at right angles to the axis of the cylinder. The piston includes an hourglass-shape spacer integral with both the upper and lower discs to fixedly space the discs from each other. The cylinder has a number of vertically spaced-apart metering piston positioning lugs extending inwardly from its inner cylindrical surface, and the lower guide disc is provided with slots in its outer periphery of size and shape to allow passage of the lower disc past the positioning lugs when the piston and cylinder are positioned to vertically align the lugs with the slots. By rotating the piston with respect to the cylinder, the lugs can be moved out of vertical alignment with the slots, and every lug, when it is in adjacent relationship to the lower disc, will prevent movement of the piston longitudinally of the cylinder when the disc comes to rest on the positioning lug.
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