1. Field of the Invention
The present invention relates to a radial piston device operable as a compressor, pump, engine, etc. and more particularly to such a device wherein the pistons are mounted on a rotating eccentric that rotates eccentrically of a crankshaft.
2. Description of the Prior Art
A four cylinder, four cycle engine operating with a free eccentric mounted on a crankpin eccentrically of the axis of a crankshaft was disclosed in "The Proceedings of the Institution of Mechanical Engineers", 1974, Vol. 188 38/174, pages 505-517. In that article the engine was described as having a cylinder block constructed of several discrete elements bolted together in a sealed arrangement. The need for the cylinder block to have been constructed of several parts was necessitated by the need to install the free eccentric assembly, the piston yokes and the pistons as a single unit. The segmented cylinder block was then assembled and joined around the dynamic elements. In addition, this article described the crankshaft as being comprised of several elements joined at positioning recesses and secured by an axially extending tension bolt, which, upon being drawn up with a nut, joined the several components rigidly together. The device described was intended for use as an internal combustion engine and included a novel rotary valve that allowed a single port in the cylinder wall to carry the combustible mixture to the cylinders and the exhaust gas from the cylinders.
An obvious difficulty associated with the engine block formed from several pieces is the need to provide a gas tight seal. This is a particularly difficult problem given the extremely high gas pressure that is developed within the cylinder. Although this problem was recognized when the article was published, the technical difficulty associated with overcoming the problem was apparently resolved by providing a sufficiently tight mechanical seal at the parting line being between the engine block segments. It would be preferable, instead, for the device to have a one-piece engine block so that the difficulties associated with having several long mechanical seals between the engine block segments can be avoided.