Double-acting hydraulic cylinder with integrated gas spring action and method for making the same

Method for constructing a gas-filled double-acting hydraulic drive cylinder with integrated gas spring action, which drive cylinder comprises:

• a cylinder sleeve with a cylinder bottom and cylinder head arranged set axially apart from each other;
• a piston/piston rod assembly which can move axially back and forth, with a piston rod which protrudes outwards through an associated bore in the cylinder head and with a piston which is securely attached to the piston rod between, and set apart from, both ends of the piston rod and which is displaceable over an axial stroke between the cylinder bottom and the cylinder head;
• a hydraulic fluid seal on the piston for providing a seal with an inner surface of the cylinder sleeve, so that the piston delimits in the drive cylinder between the piston and the cylinder head a variable head-side chamber and further delimits between the piston and the cylinder bottom a variable bottom-side chamber;
• a connection for the head-side chamber to a hydraulic line;
• a connection for the bottom-side chamber to a hydraulic line;
• a gland with a bore, the gland being attached between the cylinder bottom and the piston, so that the gland forms a separation between the bottom-side chamber and a gas space located between the gland and the cylinder bottom, and the piston rod extending over the entire axial stroke of the piston rod through the bore,
• characterized in that the gland comprises on a head-side edge two hydraulic fluid seals, one for providing a seal with the cylinder sleeve and one for providing a seal with the piston rod, and in that the gland comprises on a bottom-side edge a first and second gas seal, the first gas seal for providing a seal with the cylinder sleeve and the second gas seal for providing a seal with the piston rod, the cylinder sleeve having a filling opening which is formed, viewed in the axial direction, between the first and second gas seal, on the one hand, and the two hydraulic fluid seals, on the other hand, and is connected to the bore in the gland, and the piston rod comprising an entrainment mechanism on a bottom-side end, the method including the following steps:
• a mounting the gland and the cylinder head on the piston/piston rod assembly in such a way that the second gas seal is attached separately from an associated seat on the gland,
• b mounting the cylinder sleeve with the cylinder bottom,
• c introducing the mounted assembly of the piston/piston rod assembly, gland and cylinder head into the cylinder sleeve in such a way that the gland and the cylinder head are positioned in a desired axial position and the piston rod is retracted,
• d mechanically securing the gland and the cylinder head to the cylinder sleeve,
• e mechanically blocking the piston/piston rod assembly in the axial direction,
• f filling the gas chamber with gas by supplying gas in pressurized form via the filling opening,
• g unblocking the piston/piston rod assembly,
• h moving the piston/piston rod assembly in the direction of the cylinder head until the second gas seal is brought by the entrainment mechanism on the piston rod into the associated seat in the gland.