Abstract: A valve spring mechanism is provided which is suitable for use with the inlet or exhaust valves of an internal combustion engine, and includes a valve head and a valve stem. The mechanism includes a piston/cylinder arrangement in which the cylinder surrounds a portion of the valve stem to define a chamber. The piston is slidable and sealingly mounted on the valve stem. The mechanism also has force transmitting means for transmitting the force produced on the piston by gas pressure within the chamber to the valve stem, and a spring operating on the piston and the stem of the valve for applying a force to the stem tending to close the valve in the event of failure of chamber gas pressure. The spring is positioned to maintain it in a compressed condition during normal operation of the mechanism as a result of gas pressure within the chamber.

Abstract: The present invention relates to a valve spring mechanism suitable for use with the inlet or exhaust valves of an internal combustion engine. More specifically, the invention provides a valve spring mechanism for a poppet valve (101) which comprises a valve head (102) and a valve stem (104). The mechanism comprises a piston (109) and cylinder (108) arrangement in which the cylinder (108) surrounds a portion of the valve stem (104). The piston (109) is slidingly and sealingly mounted on the valve stem (104), and the piston (109) and cylinder (108) define a chamber (110). The mechanism also comprises force transmitting means for transmitting the force produced on the piston (109) by gas pressure within the chamber (110) to the valve stem (104); and a spring (113) operating on the piston (109) and the stem of the valve for applying a force to the stem of the valve tending to close the valve in the event of failure of gas pressure within the chamber (110).