Abstract: 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 the 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.

Abstract: An elongate tank for transport or for storage in bulk of semisolid and fluid materials, such as grease and oil. The tank has an outlet at one end thereof for discharging material contained therein, and has a generally cylindric interior surface. A generally cylindric piston is sized to slide in the tank and is movable in a direction toward the outlet thereby to place material in the tank through the outlet. The piston comprises a piston member and an elastic annular seal carried in a circumferential channel around the piston member. The seal has an annular base and an annular crown disposed radially outwardly of and joined to the base with a fluid chamber between the base and crown. The seal is expandable by introducing fluid into the fluid chamber.

Abstract: An elongate cylindric tank for transport or for storage in bulk of semisolid and fluid materials, such as grease and oil with an outlet at one end thereof and a generally cylindric piston sized to slide therein and be moved in a direction toward the outlet, thereby forcing the material in the tank through the outlet. The piston includes a piston member, with a circumferential channel adjacent one end thereof, a seal for sealing the piston member against the interior surface of the tank, and a mechanism for holding the piston against canting in the tank while permitting the piston to slide freely in the tank. The seal comprises an elastic annular packing disposed at least partly within and carried by the channel and a circumferential flexible sheath overlying the packing and protecting it.

Abstract: An elongate tank for transport or for storage in bulk of semisolid and fluid materials, such as grease and oil. This tank has an outlet for the material contained therein at one end thereof, and is of generally cylindric interal cross section. It has a generally cylindric piston sized to slide therein, which is adapted to be moved in a direction toward the outlet, thereby forcing the material in the tank through the outlet. An elastic annular seal is carried in a circumferential channel around the piston adjacent one end of the piston. The seal is hollow and expandable and has a pressurizing device for varying the pressure within the seal between atmospheric pressure and a pressure higher than atmospheric wherein the seal expands and presses against the internal surface of the tank with the pressure such that when the piston slides in the tank the seal is maintained in sliding engagement with the internal surface thereby to wipe the material therefrom and to seal the piston relative to the tank.