Rotary expansible chamber devices – Weight balanced working member or partition
Patent
1999-02-08
2000-10-31
Nguyen, Hoang
Rotary expansible chamber devices
Weight balanced working member or partition
4182101, F01C 2100
Patent
active
061392979
DESCRIPTION:
BRIEF SUMMARY
The invention relates to measures for the balancing of a twin screw system in axis-parallel arrangement with outer-axis engagement in counter-rotation, and with angles of contact of at least 720.degree. in single-flight design. The distance between centre of gravity and centre, end face, and angle of contact determine in this context the values of the static and dynamic imbalances which occur with screws with single-flight profiles.
In the disclosure text Sho 62(1987)-291486 from the company Taiko, Japan, a method of screw balancing is described: First, static balance is achieved by determining the length of the screw in integer multiples of the pitch. By means of cut-outs in the screw on both sides, on the face side, which are hollow or filled with light material, dynamic balance is achieved.
This method of balancing cannot be implemented if special materials are demanded, which cannot be cast. With unusual profile geometries, too, this method has its limits, since on the one hand the wall thicknesses of the screws cannot, for reasons of stability, be reduced at will: on the other band, an excessively great extension in axial direction of the balancing hollows would incur big manufacturing problems because of the helical shape.
The invention is based on the objective of defining measures for the balancing of single-flight screws, the geometry of which is unusual or the use of which requires special materials, without incurring major investment in the manufacture and without prejudicing form stability.
This objective is achieved according to the invention by means of a twin screw system 1, 2 (FIG. 1) in axis-parallel arrangement with outside axis engagement with counter-running movement, and angles of contact of at least 720.degree. in single-flight design, in such a way that the lengths of the screws are not fixed at integer multiples of the pitch, and that the outer contours of the screw are changed in the medium intake area in order to achieve balancing 3 (FIG. 1).
Possible embodiments are provided by the application of additional masses 6 (FIG. 1) in the outer area, in particular at the pilot gear, as well as by face-side balancing hollows 4 (FIG. 2), the axial extension of which is varied for the purpose of optimisation.
The advantages achieved with the invention are: application of face-side balancing hollows, achieved by the optimum dimensioning of screw angles of contact, winding angles of balancing hollow, and balancing hollow cross-section. reducing temperature.
On the basis of the embodiments shown in the figures, the invention is now explained in greater detail:
The figures show:
FIG. 1: A twin screw system for a screw pump in single-flight design according to the invention, with angles of contact of 1598.degree. and balancing cut-outs at the screw outer contours in the medium intake area.
FIG. 2: An embodiment of a twin screw system from FIG. 1 with balancing hollows in a frontal view.
FIG. 3: The representation of the helical profile centre-of-gravity location curve of a screw profile from FIG. 2.
In one embodiment, the twin screws 1, 2 (FIG. 1) feature lengths of 4.439 times the pitch, which corresponds to an angle of contact of 1598.degree. (FIG. 3). The end profile S (FIG. 2) and the pitch 1 (FIG. 1) determine, together with the wall thickness d (FIG. 2), the greatest part of the contour of the axially-located balancing hollows 4 (FIG. 2); the core circle 7 (FIG. 2) delimits this towards the centre. With common angle positions of the centres of gravity of the full profile and balancing surfaces S.sub.0, S.sub.3 (FIG. 2), the straight termination is mandatorily derived in the balance surface.
By calculation, the problem is dealt with as follows:
In a rectangular co-ordinate system with a screw axis as w-axis and u-axis and v-axis in the plane of the middle screw face sections, the centre of gravity S.sub.0 (FIG. 3) is positioned on the u-axis. The extension of the screw in the w-direction extends symmetrically from -W.sub.2 . . . +W.sub.2 or in angle definition from -.alpha..sub.2 . . . +.a
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patent: 4490102 (1984-12-01), Carre et al.
patent: 5167496 (1992-12-01), Jacobsson et al.
patent: 5269667 (1993-12-01), Mauney
patent: 5273412 (1993-12-01), Zwaans
Ateliers Busch S.A.
Browning Clifford W.
Nguyen Hoang
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