Pumps – Expansible chamber type – Having pumping chamber pressure responsive distributor
Patent
1999-06-18
2000-12-26
Walberg, Teresa
Pumps
Expansible chamber type
Having pumping chamber pressure responsive distributor
417269, F04B 3910, F04B 5310
Patent
active
061649376
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention refers to a particular embodiment of an alternating-motion piston reciprocating in a respective cylinder.
To more effectively exemplify and more clearly illustrate the invention, said piston is assumed to work in close association with a compressor for refrigerators, in particular household-type appliances, without this however limiting the scope of the invention solely to such an application or connection.
It is a largely known fact that, in view of improving the thermodynamic efficiency of compressors, it is absolutely necessary for the volume of the discharge port, which is not affected by the displacement of the piston, to be as small as possible. The reasons behind such a requirement are well known to those skilled in the art, so that they shall not be dealt with any longer here.
In view of artificially reducing such a volume, the practice is known in the art, for instance from the disclosure in U.S. Pat. No. 5,149,254, of providing, on the head of the related piston, a protrusion (post 54) that is so arranged and sized as to enable said protrusion to almost fully penetrate into the discharge port when the piston reaches its top dead center, without this of course giving rise to any interference with other parts nearby.
This expedient enables the volume of the discharge port that can be occupied by the gas to be temporarily reduced in an artful manner, but to a quite considerable extent, so that the overall compressor efficiency can actually be boosted sensibly, as already mentioned above.
The above solution is certainly simple, reliable, economic and safe; however, in the course of the highly automated production of this kind of pistons a number of practical drawbacks tend to emerge, as described below in greater detail.
The grinding operation on the outer cylinder of said compressor pistons is carried out by means of a grinding technique without a fixed and secured center of rotation; the same process is generally used for producing millions of cylindrical parts such as the cylindrical rollers of roller bearings.
The grinding process essentially consists in a continuous sequence of said pistons carried by conveying means through a plurality of grinding wheels or similar means being abraded by the action of said plurality of grinding wheels or similar means.
The size, orientation and number of said grinding means are such as to enable the pistons conveyed into such a processing step to be sent there in sequence with their axes coinciding with and parallel to the direction of the motion thereof through said plurality of grinding means.
However, if the pistons happen to be arranged in contact with each other, in the sense that the head of one such piston is in contact with the rear edge of the neighbouring piston, then a serious drawback arises in that, owing to the afore mentioned protrusion, said pistons tend to assume a position which is slightly inclined with respect to the direction of motion. The result is that they would come up obliquely in front of or with respect to said grinding means and, therefore, would practically prevent the grinding process from being carried out.
In view of eliminating such a drawback, said pistons are therefore spaced from each other so that the protrusion thereof is prevented from touching any other piston. Such a very simple and effective measure of spacing the pistons from each other, however, has the effect of slowing down and, therefore, decreasing the productivity of the grinding operation, since the pistons must be cadenced into the process at a much lower rate, owing to the need for their forward speed to be maintained unaltered, while the "virtual" length thereof, ie. the length including both the actual length of the piston and the intermediate space that separates it from the subsequent piston in the sequence, is on the contrary increased, as this is best illustrated in the accompanying FIG. 1.
It therefore would be desirable, and is actually a main purpose of the present invention, to provide a technical solution that, w
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Fastovsky Leonid
Walberg Teresa
Zanussi Elettromeccanica S.p.A.
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