Rotary expansible chamber devices – Moving cylinder – Rotating
Patent
1995-01-24
1996-09-10
Vrablik, John J.
Rotary expansible chamber devices
Moving cylinder
Rotating
F04C 210
Patent
active
055540198
DESCRIPTION:
BRIEF SUMMARY
This invention relates to gerotor pumps which, as well known, comprise a male lobed rotor with n lobes, located in and meshed with a female lobed annulus having n+1 lobes. This rotor and annulus, called the gerotor set, rotate relative to one another about parallel axes so that a series of chambers each defined between a pair of parallel lines of contact between the two parts rotate about said axes, increase in size as they pass over an inlet port in a first half revolution, and decrease in size as they pass over an outlet port in the following half revolution. The ports are formed in a body having a cylindrical cavity for the gerotor set.
BACKGROUND OF THE INVENTION
Many different designs of gerotor pump are known: the objects of the present invention are to simplify manufacture and particularly to provide for axial compactness, without sacrificing efficiency or durability.
SUMMARY OF THE INVENTION
According to the invention, a gerotor pump is characterised by an externally at least part-cylindrical body, a drive gear journalled on said body part and angularly fast with a drive shaft concentric of the body, said shaft also being angularly fast with the rotor of the gerotor set.
Preferably the shaft is a clearance fit in the body of the pump, that is, it does not make contact with the body at any point. Hence the pump of the invention is distinguished from the prior art in that the shaft is neither fast with the body (as has previously been suggested in certain prior art patents) nor is it journalled in the body, which has been the norm in pumps of this kind. When the shaft is fast with the body, it is necessary to provide a certain body length which can support the shaft in cantilever fashion, and when the shaft is journalled in the body an even greater axial length has to be provided to support the shaft. By supporting the shaft from the drive gear, with which it is fast and journalling the gear, reduced axial dimensions are possible without any sacrifice of pump performance.
The axial length of the shaft is equal to the sum of the axial length of the rotor, the axial thickness of the drive gear and its hub, i.e. in the region of the shaft, and the dimension between the two parts, if any.
The pump body may be cup-shaped with the base of the cup apertured for the shaft to extend through, and the rim of the cup may sit on an associated part such as the face of an engine block or sump. Or the rim of the cup may be associated with a closure plate. The shaft may extend up to that block, sump or plate with a slight end clearance for the shaft.
The shaft may be an interference fit in both rotor and drive gear, or alternatively it may be splined to one or the other to allow for removal for maintenance purposes.
The engineer to whom this specification is addressed will understand that the shaft requires to run true, and its cantilever stiffness is dictated by the journalling of the gear together with the connection between the shaft and the gear.
THE DRAWINGS
In the accompanying drawings, two pumps are illustrated in FIGS. 1 and 2, respectively, which are generally similar, both being shown in sectional elevation.
DETAILED DESCRIPTION
Turning first to FIG. 1, the body 10 is generally cup-shaped having a generally cylindrical side wall 10a and a transverse, generally planar end wall 10b, and secured to a closure plate 12 by means of cap screws located in spaced apertures 14. In this instance the pump is accommodated in an aperture in an engine component 16.
A bearing bush 18 is supported on the cylindrical exposed portion of the body wall and this journals drive gear 20. The gear is unitary with the hub 22 and there are apertures 24 in the gear to reduce weight and provide access to the cap screws.
It will be noted that the end wall 10b of the body 10 has an enlarged central opening 10c and the hub 22 extends into than opening 10c with a clearance between it and the body, and as such is neither contacted nor supported by the wall of the opening.
The rotor 26 is located in the body and has the same axia
REFERENCES:
patent: 5261803 (1993-11-01), Freeman
Concentric Pumps Limited
Vrablik John J.
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