Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Reexamination Certificate
1999-07-15
2001-09-25
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
C417S255000, C417SDIG001, C092S248000, C092S212000, C092S252000, C092S253000
Reexamination Certificate
active
06293764
ABSTRACT:
The invention relates to a reciprocating piston compressor.
BACKGROUND OF THE INVENTION
In a reciprocating piston compressor of the named type known from the Baumann U.S. Pat. No. 5,033,940 the piston and the cylinder are each executed with a running surface of an abrasion-resistant material, with the piston being supported via a roller body, e.g. a ball, on a connection part coupled to a drive device and movably guided in the cylinder transversely to the longitudinal axis. A dry running split-ring seal which permits a predetermined leakage flow of the compressed medium is achieved through the known embodiment in particular for short-stroke small compressors. For this the abrasion-resistant materials of the piston and of the cylinder must be chosen in such a manner that they have at least approximately the same coefficient of thermal expansion in order to keep the leakage loss substantially constant during operation.
SUMMARY OF THE INVENTION
The object of the invention is to provide a further developed reciprocating piston compressor of the initially named kind suitable for embodiments having dimensions selectable within a relatively large bandwidth in a simple, economical to manufacture design which permits the formation of a dry running split-ring seal with low constructional complication and expense even for relatively long-stroke embodiments and which ensures a constant leakage flow.
The thermal expansion of the piston can be influenced and matched to the coefficient of thermal expansion given by the cylinder material used for the cylinder part surrounding the piston, i.e. held within a predetermined expansion range in a particularly simple, economical manner. This is achieved through the combination, provided in accordance with the invention, of a piston having a metallic basic body and with a sleeve member of plastic encompassing the latter with a cylinder surrounding the piston with a ring gap in that the choice of material and the ratio of the partial cross-sections of the basic body and of the sleeve member are matched to one another in accordance with a predetermined resultant thermal expansion of the two piston parts. Accordingly, a dry running split ring seal with a substantially constant, minimum clearance between the piston and the cylinder can be achieved so that a contact-less guiding of the piston which is free from lateral forces can be ensured within a relatively large, operationally predetermined, temperature range. The material combination provided in accordance with the invention is also suitable for embodiments with relatively high piston speeds, with the sleeve member, which is made of plastic, in particular preventing a blocking of the piston even in the case of a failure of the split ring seal. A high operational security of the compressor is thus ensured. The plastic of the sleeve member can in addition be doped with a dry lubricant, e.g. polyphenylene sulphide (PPS), polytetrafluoroethylene (PTFE), polyethylene (PE) or the like. A particular advantage of the execution in accordance with the invention consists in the fact that the described, substantially contact-free guidance of the piston can be achieved with simple means, in particular without an additional complicated and expensive guide apparatus and using economical, relatively easy to work materials. Accordingly, economical embodiments can also be realised with relatively large piston/cylinder and/or stroke dimensions.
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Feistel, Norbert, “Round the world twice—without lubrication” in: Sulzer Technical Review, vol. 78, No. 4, Sep. 1996, pp. 42-45.
Freay Charles G.
Greenfield AG
Solak Timothy P.
Townsend and Townsend / and Crew LLP
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