Patent attributes
A rod sealing system for use with a hydraulic cylinder is disclosed. The hydraulic cylinder has a cylinder tube and a cylinder head defining a working chamber. A piston is disposed for linear reciprocable movement within the working chamber and is connected to a piston rod projecting outwardly through the cylinder head. The rod sealing system includes a primary seal acting between the cylinder head and the piston rod and a secondary seal acting between the cylinder head and the piston rod. The rod sealing system also includes a back-up seal acting between the cylinder head and the piston rod and the cylinder head has a bypass channel fluidically connecting the working chamber with a chamber in the cylinder head between the back-up seal and the primary seal. Flow of hydraulic fluid through the bypass channel is selectively allowed or prevented with a bypass valve to selectively equalize the pressure across said back-up seal when the back-up seal is not in service.
