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Piston-connecting rod assembly Disclosure Number: IPCOM000005840D
Publication Date: 2001-Nov-12
Document File: 3 page(s) / 44K

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DE 4424672 A1: PATENT


A piston - connecting rod assembly for a reciprocating CO2 -compressor is disclosed. The assembly is realized by PEEK injection moulding of a ball bearing within a recess on the rear side of the piston.

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Piston - connecting rod assembly
 for a reciprocating CO2 compressor

Disclosed by Danfoss A/S

A piston - connecting rod assembly for a reciprocating CO2 compressor is hereby disclosed.

Compressors using CO2 as refrigerant have to deal with considerably higher working pressures as compared to systems with standard hydrocarbon based refrigerants, resulting in increased forces per area to be handled by the bearing between piston and connecting rod.

Further, the total length of the assembly has to be controlled to minimize re-expansion of compressed gas caused by the dead volume within the cylinder.

A piston - connecting rod assembly is disclosed realized by injection moulding of a ball bearing within a recess on the rear side of the piston.

Advantageously, piston and connecting rod are aligned in a moulding tool in a manner to determine the final total length of the assembly. A suitable temperature- and media compatible low-friction plastic material, such as e.g. PEEK, is then injected through an opening arranged in the front end surface of the piston and fills up the volume between the inside of the piston and the ball.

This method to produce a ball bearing is well known and widely used. For reference, see e.g. patent application publication DE 4424672A1.

The moulding process results in a large bearing area, able to deal with both high compressive and tensile forces. At least two oil feeding channels, connecting the ball bearing surface with an annular surface at the rear end of the piston, allow lubrication of the bearing. The annular surface is inclined relative to the axis of the piston. During suction stroke oil, which is supplied by a supply channel arranged in the cylinder block, is collected at the annular surface and pressed into the oil feeding channels.

An example of the disclosed piston - connecting rod assembly is shown in Figures 1 and 2.
























·  Connection rod 1 has a journal bearing 2 at the crankshaft side (known and approved technology for reciprocating compressors).

·  Connection rod has...