Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Patent
1995-02-07
1996-04-23
Denion, Thomas E.
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
417273, F01B 100
Patent
active
055093477
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a radial piston pump of the type, in which an eccentric rotor is adapted to cause the pistons to perform a reciprocating movement within radial cylinders in the pump body, the radial inner ends of the pistons being each provided with a broadened foot, said broadened feet being kept in contact with the rotor also during the suction strokes of the respective pistons by means of a coupling ring of a substantially L-shaped cross-section, the axial ring portion of which engages the radial outer end faces of the broadened feet and the radial portion of which keeps said ring axially in place.
Discussion of the Prior Art
Such a pump is known from German Offenlengungsschrift 1.928.853.
With this well-known pump the broadened feet at the radial inner piston ends are formed by sliding shoes which are pivotally connected to the respective piston ends. The effective sliding surfaces of said sliding shoes are shaped to conform with the cylindrical surface of the rotor and the cylindrical inner circumferential surface of the axial ring portion of the coupling ring respectively. The coupling ring has its radial portion fixedly connected to the rotor. The sliding shoes, which are stationary as seen in the direction of rotation, are thus slidingly guided with an inner and an outer cylindrical sliding surface between two concentric cylindrical surface portions of the rotor and of the coupling ring respectively. This means, that a considerable frictional resistance has to be overcome, said frictional resistance being further increased by the friction in the pivot connection between the pistons and the sliding shoes.
SUMMARY OF THE INVENTION
The invention therefore aims at providing a pump of the above type, with which the frictional resistance to be overcome in operation, is substantially reduced.
According to the invention this aim is achieved in that the coupling ring has its radial portion bearing loosely against a radial sliding surface, while the broadened feet at the radial inner piston ends are in the shape of heads which are integrally formed with the respective pistons, the free end faces of said heads, as well as the end faces adjoining the respective pistons being spherically shaped, the axial portion of the coupling having an inner circumferential surface of a slightly conically widening shape.
Due to the measures according to the invention the areas of contact between the mutual sliding surfaces of the pistons, the coupling ring and the rotor are substantially reduced to point and line contacts, whereas the movements of the coupling ring will in practise be limited to a translational movement of a small amplitude relative to the stationary radial sliding surface. Moreover, the end faces of the piston heads adjoining the pistons may rock on the inner circumferential surface of the axial portion of the coupling ring.
The omission of a pivot connection between the pistons and the heads of the same not only avoids the friction involved with such pivot connection but also leads to a simpler construction.
It is to be noted, that German Offenlegungsschrift 1.653.643 discloses a radial piston pump, wherein the radial inner piston ends are also provided with an intergrally formed widened head, the free end face of which is of a spherical shape. With this embodiment, however, the annular end faces adjoining the respective pistons are flat in shape, while the coupling ring has at its inner circumference an arcuate portion (turned with its convex side towards the axis of the pump) at the location of each piston head, said arcuate portions engaging the flat annular end faces of the respective piston heads.
A disadvantage of this well-known construction is that the coupling ring may, in addition to the required translational movement, easily make an undesired rotational movement relative to the pistons, as a result of which the widened heads may get jammed between rotor and coupling ring.
The invention will be hereinafter further described by way of example with reference to
REFERENCES:
patent: 3968736 (1976-07-01), Pecorari
patent: 5295797 (1994-03-01), Kahrs et al.
de Jong Leendert W. C.
Masseling Willem H.
van Heiningen Arjan P.
Applied Power Inc.
Denion Thomas E.
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