Rotary expansible chamber devices – Interengaging rotating members – Helical or herringbone
Patent
1998-08-24
2000-10-10
Nguyen, Hoang
Rotary expansible chamber devices
Interengaging rotating members
Helical or herringbone
F01C 116
Patent
active
061295353
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the profile geometries of double conveying worms for a parallel-axis outer-axis operation in pumps with pilot gear systems, for counter-flight guidance of the worms. Profile geometry, angle of contact, pitch, gap width, medium control, and rotation speed determine in this situation the pump characteristics such as conveying volume, degree of efficiency, final pressure, leakage rate, temperature, noise, and investment in manufacture.
The geometries known as the SRM profile from the company SRM, Sweden, are well-suited for the construction of fast-rotating double conveying worms with irregular profiles in multi-flight design and small angles of contact for pumps with final pressure in the middle range. Gaps incurred by the design between the engagement line and the inner edge of the housing, generally known as the "blow-hole", prevent higher final pressures or good volumetric degrees of efficiency at lower and medium speeds of rotation.
In the present case, however, interest is focused on pumps of higher final pressures in medium peed ranges, for which single-flight double worms with axial sequence of the operating cells and angles of contact >720.degree. are better suited. By designing one flank in each case of the single-flight profiles as an extended cycloid, alternating symmetrical lines of engagement are formed, which run along the outer contours of the worm from the inner edges of the housing to the core circles. These lines of engagement subdivide the interior of the pump into axially-migrating operating cells with twice the pitch length in an overlapping arrangement.
In known embodiments, such as are available, for example, from the company Taiko, Japan, the worms are manufactured with angles of contact of 1080.degree., 1440.degree., 1800.degree., etc., which feature identical end profiles. The outlet is controlled on the end side by one of the worms, with an aperture along the second profile flank, which at that point is involute-shaped.
While maintaining the operational principle of the axially-migrating operating cells with double the length of pitch, the intention is to redesign and redefine the profile geometry in the sense of modern series manufacture, and it is also intended to improve the volumetric degree of efficiency, the dynamic behaviour, and the control of the medium.
This objective is achieved according to the invention with double conveyor worms with profile contours with core circles, cycloid-shaped hollow flanks, outer arcs, and a second flank, in that, as a departure from the prior art, the second flank 6, referred to as the cover flank, is also connected at the foot point without a fold to the core circle 4, and that the cover flank 6 contains at least one middle area which does not rise in pitch, containing the saddle support 7, which connects the part cover flanks formed in this manner, the inner flank 8 and the outer flank 9, free of folds.
On the basis of the embodiments shown in the drawings and characterised in Sub-Claims 2, 3, the invention is described in greater detail.
The drawings show:
FIG. 1: A double worm system in single-flight design with pilot gears and with angles of contact of approx. 1600.degree. according to the invention, with a middle saddle support range in the cover flank, in a reduced scale.
FIG. 2: An embodiment of the profile geometry and the engagement proportions with the counter-profile of a double worm system from FIG. 1.
FIG. 3: An embodiment of the double worm system shown in section, according to the line A--A in FIG. 1, installed in a housing, in the same scale as FIG. 1.
FIG. 4: An embodiment of the conveying worms in an axial section, in sections.
In the embodiment chosen, the conveying worms 1, 2 (FIGS. 1 and 3) have angles of contact of approx. 1600.degree. and the same end profiles with a cover flank composed of several part flank curves: The saddle support 7 (FIGS. 1 and 2) is arc-shaped, with a radius of the size of a half distance between axes, and corresponds in the installation with the saddle support of the
REFERENCES:
patent: 5697772 (1997-12-01), Kawamura et al.
Ateliers Busch S.A.
Browning Clifford W.
Nguyen Hoang
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