Rotary expansible chamber devices – Working chamber surface expressed mathematically
Patent
1997-08-06
1999-03-30
Vrablik, John J.
Rotary expansible chamber devices
Working chamber surface expressed mathematically
F01C 1344, F01C 2110
Patent
active
058880585
DESCRIPTION:
BRIEF SUMMARY
The subject of the invention is a displacement machine with moving sealing elements, comprising at least one encapsulation essentially including a capsule consisting of a cylindrical tubular part with non-circular directrix and two end flanges, a cylindrical piston whose directrix is a circle of centre O and of radius R.sub.p, provided with grooves which guide the sealing elements in the piston, this piston being in rotary connection with the capsule about its axis, as well as a system for distributing the fluid, allowing its inlet and its outlet. In this machine, the moving sealing elements are most often vanes, but may be rollers. The directrix of the tubular part of the capsule, called the capsule profile, is constituted successively and alternately by n circle arcs called conformity arcs, with optionally zero angular aperture, of centre O and of radius R.sub.p +J, J denoting the radial play between these arcs and the directrix of the piston, as well as n geometrical arcs, called arches, which limit the movement of the sealing elements in the grooves in the centrifugal direction. Each arch has, with the adjacent conformity arcs, two connection points M.sub.i and M.sub.f at which the radii of curvature are respectively equal to R.sub.ci and to R.sub.cf, and at which the angles .tau..sub.i and .tau..sub.f, respectively, of the tangents differ by .pi./2 from the corresponding polar angles .theta..sub.i and .theta..sub.f ; each arch also contains a point M.sub.e at which the polar radius is a maximum, equal to Rp+J+H, at which the angle .tau..sub.e of the tangent differs by .pi./2 from the corresponding polar angle .theta..sub.e and at which the radius of curvature R.sub.ce is less than R.sub.p.
Numerous displacement machines which correspond to this definition are known, and in particular the machines described successively in the following patents and patent applications: U.S. Pat. No. 2,791,185, JP 58-174102 and FR 2 547 622.
In each of these patents, an original capsule profile is claimed, in U.S. Pat. No. 2,791,185 in order to correspond to a particular organisation of the machine, in patent JP 58-174102 in order to accelerate the extension of the vanes and to slow their retraction, and in patent FR 2 547 622 in order to provide a better compromise between the various constraints imposed by the design of high-performance machines.
A tendency to progressive improvement of that geometrical element of the machine which is most critical for performance, and a virtually inevitable tendency to a substantial increase in the number of parameters required to specify a capsule profile, which makes it difficult to express the optimization constraints by using these parameters and, above all, to rank these constraints, can be observed through these three patents.
In the machines according to the invention, this tendency is departed from by providing a novel geometry of the capsule profile which directly satisfies the two major requirements to which high-performance machines are currently subject, namely compactness and smooth running, while needing to resort only to a minimal number of parameters in order to specify this geometry.
The invention assumes the following geometrical data to be a priori set: R.sub.p, n, H/R.sub.p, J, .theta..sub.i, .theta..sub.e, .theta..sub.f, to which at most the radii of curvature R.sub.ci, R.sub.ce and R.sub.cf may be added. the desired value of the volume capacity for a unitary width of the encapsulation; the overall size of the machine; this ratio is, however, limited by the possibility of producing the grooves in the piston, the difficulty of which increases as the value n decreases, and by the necessity of obtaining a profile which has a sufficient radius of curvature at each of its points, in particular in order to ensure contact between the sealing element and the capsule with a Hertz pressure which is as low as possible, and which has a sufficient curvature to prevent retraction of the sealing elements in the piston under the combined action of the fluid pressure and the iner
REFERENCES:
patent: 4480973 (1984-11-01), Ishizuka
patent: 4501537 (1985-02-01), Ishizuka
patent: 4507068 (1985-03-01), Hayase et al.
patent: 4712987 (1987-12-01), Inomata
patent: 4802830 (1989-02-01), Nakajima
Flamme Jean-Marie
Leroy Andre
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