Power plants – Motor operated by expansion and/or contraction of a unit of... – Unit of mass is a gas which is heated or cooled in one of a...
Patent
1992-10-16
1994-05-10
Look, Edward K.
Power plants
Motor operated by expansion and/or contraction of a unit of...
Unit of mass is a gas which is heated or cooled in one of a...
277 961, 277100, F01B 2910, F02G 104
Patent
active
053097157
DESCRIPTION:
BRIEF SUMMARY
The invention relates to Stirling engines. In referring to a Stirling engine we include those engines which operate on a cycle resembling the Stirling cycle but with some overlap and merging of the individual phases of the classical Stirling cycle.
The invention is applicable particularly but not exclusively to Stirling engines of the multi-cylinder double-acting type. Typical engines of this type have a hot working chamber at one end, normally the upper end and a cold working chamber at the other end of each cylinder separated by the piston, each of these hot and cold working chambers being connected respectively to a cold or hot working chamber of another cylinder. In this way, four closed working volumes are established in each of which the required working fluid is permanently entrapped. Conventional lubricants can not normally be used within the working volume because the lubricant carbonises and carbonised deposits interfere with heat transfer capability.
This kind of design often incorporates an axial piston rod extending through a sliding seal in the cylinder, running in a cross head bearing and then connected to a shaft, typically through a normal crank drive. Sliding seals of this nature tend to suffer from high friction and wear problems and wear compensation is difficult to achieve with such a seal. The reduced effective piston area caused by the piston rod can also be a disadvantage.
Alternatives to sliding seals such as rolling diaphragm seals or use of pressurised crankcases with simple crank mechanisms introduce other problems such as unreliability for the sliding seal and excess weight in reducing crankcase volume.
In our co-pending PCT patent application filed simultaneously herewith and claiming priority from our UK application 9008522.6 we describe a reciprocatory Stirling engine in which a connection between the piston and a main shaft comprises a lever arm pivotable intermediate its ends and extending through the cylinder wall, connected at one end thereof to the piston and at the other end thereof to the main shaft.
An object of the present invention is to provide an effective seal arrangement for such a lever arm.
According to the present invention there is provided a Stirling engine comprising a drive member, a cylinder, a piston reciprocable in the cylinder, a connection between the piston and the drive member comprising a lever arm pivotable about a pivot bearing intermediate its ends and extending through the cylinder wall and a gas seal arranged to prevent escape of pressure from the cylinder in the region of the lever arm, the seal comprising a part spherical seat on the lever arm with its centre coincident with the pivot axis, an annular seal member with a part spherical sealing surface in sealing contact with the part spherical seat and means for urging the seal member into sealing engagement with the seat.
Preferably the pivot bearing comprises a pivot pin passing through the lever arm and mounted at both ends in a pivot housing.
Preferably the connection between the piston and the drive member defines a limit of pivotal movement for the lever arm and the width of the sealing surface is greater than the movement of a corresponding part of the part spherical seat when the lever arm moves between its limits of pivotal movement such that there is a specific annular area on the surface of the seat which is and always remains in engagement with the sealing surface.
Preferably the seal member is carried in a movable seal holder which is supported in a fixed carrier and is urged by gas pressure in the engine, which may be supplemented by a spring, into engagement with the seal seat The annular seal member may be arranged to rotate about its own axis to distribute wear evenly around the sealing surface. This rotation may be derived from movement of the lever arm through a pawl which engages a ratchet wheel which in turn drives the seal member through a reduction gear.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawin
REFERENCES:
patent: 2616247 (1952-11-01), Liebe
patent: 3185489 (1965-05-01), Lohr
patent: 4392350 (1983-07-01), Marks
patent: 4553392 (1985-11-01), Chagnot et al.
patent: 4645212 (1987-02-01), Lundholm
patent: 5085054 (1992-02-01), Katsuda et al.
ESD Engines Limited
Look Edward K.
Nguyen Hoang
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