| 摘要 |
In an elongate tank for transport or for storage in bulk of semisolid and fluid material such as grease and oil. The tank has an outlet at one end thereof for discharging material contained therein and is of generally cylindric internal cross section. It has a generally cylindric piston sized to slide in the tank and adapted to be moved in a direction toward said outlet thereby to force the material in the tank through the outlet. The piston comprises a piston member which carries an annular elastic seal.The seal has an annular crown projecting radially outwardly from the piston member and engageable with the interior surface of the tank.The seal has a pair of spaced apart legs supporting the crown, and an arrangement for squeezing the legs together to move the crown outwardly and cause it to be pressed aginst the interior surface of the tank with a pressure such that when the piston member slides in the tank a portion of the crown is maintained in sliding engagement with the interior surface thereby to wipe the material therefrom and to seal the piston member relative to the tank. The piston member is held against canting by at least one anti-canting member extending radially outwardly beyond the periphery of the piston member and spaced axially from the seal for engagement with the interior surface of the tank which permits the piston member to slide freely in said tank.
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