Abstract: An apparatus for vertically moving a ram in a compression molding machine having a ram slidably fitted within an outer cylinder. The ram has a hollow portion which includes an oil reservoir. A piston is slidably fitted within this hollow portion. A source of air pressure is connected to a space between the piston and the top of the hollow portion. As air pressure is applied, the piston will move so as to displace oil from the hollow portion. A pilot check valve is positioned in the ram so as to pass oil into an area between the ram and the outer cylinder.

Abstract: A double-cylinder construction which can be used not only in large-sized compression molding machines but also in small-sized or medium-sized compression molding machines. In the double-cylinder construction of the present invention, a ram slidably fitted within an outer cylinder is provided in the center thereof with a hollow part. A rod slidably fitted in said hollow part is fixed to the bottom of said outer cylinder without penetrating said bottom thereof, and said rod does not contain an oil passage within. The double-cylinder construction always contains a certain amount of oil within and this self-contained oil is moved back and forth within the double-cylinder construction when the ram is being moved up and down. Therefore, the amount of oil supplied to the double-cylinder construction from outside is very small.