Pump with deformable thrust plate

Details Pump with deformable thrust plate Pump with deformable thrust plate

1999-01-25

2001-05-22

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

With mechanical sealing

Axially movable end wall or end wall portion

C418S133000, C418S072000, C418S078000

Reexamination Certificate

active

06234775

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a pump comprising a housing and a pump unit arranged therein, the pump unit comprising a first and a second thrust plate and a ring arranged therebetween and having a through opening, at least at an outer peripheral region of the ring resting on the two thrust plates, a pressure chamber being formed between the second thrust plate and the housing.
Pumps of the type described above are known. The pump is provided with a housing which receives a pump unit. The pump unit comprises a first and a second thrust plate, between which a ring is arranged. A pump chamber is thus formed in which a pump insert is arranged which comprises movable parts for drawing in and compressing a medium. During operation of the pump the movable parts of the pump insert are moved along the inside of the ring and/or the thrust plates. It has been found that the compressed medium deforms the thrust plates. In particular, the thrust plates bulge outwards. A gap is thus formed between the movable parts of the pump insert and the thrust plates. As a result, a shortcircuit is effectively produced between the pressure region and the suction region of the pump, so that the medium conveyed can flow out of the pressure region into the suction region. This has an adverse effect upon the volumetric efficiency of the pump.
In order to improve the efficiency of such a pump, the side of one thrust plate remote from the pump chamber is acted upon with the fluid pressure from the pressure region. The other thrust plate is supported on a face of the housing. That face of the housing has to be made particularly flat so that the thrust plate rests uniformly thereon. In this case the housing is formed by a cup-shaped housing half and by a plane housing lid which is provided with the flat face. A disadvantage of this is that the flat face of the lid can be produced only at a substantial cost. In addition, the entire housing, and in particular the lid, has to be constructed with a particularly high degree of rigidity, so that it can act as an abutment for the thrust plate.
In other known pumps, in order to improve efficiency, the side of the two thrust plates remote from the pump chamber is acted upon with the fluid pressure from the pressure region. This has the disadvantage that an additional cost for sealing is required in order to be able to supply the thrust plates from outside with the medium acted upon with pressure.
SUMMARY OF THE INVENTION
An object of the invention is therefore to provide a pump as described above which does not have the known disadvantages.
The invention provides a pump comprising a housing and a pump unit arranged therein. The pump unit comprises a first and a second thrust plate and a ring arranged therebetween and having a through opening. The ring rests on the two thrust plates at least at an outer peripheral region thereof. A pressure chamber is formed between the second thrust plate and the housing. Spacer means are provided to support the first thrust plate at a distance from the housing. The spacer means are associated at least in part with a radially inner surface area of the first thrust plate opposite the through opening.
During operation of the pump the second thrust plate acted upon with fluid pressure from the pressure chamber is displaced towards the ring. The ring presses against the facing side of the first thrust plate which is thereby deformed in the manner of a cup spring, since it is supported at its other side on the spacer means. In particular, the thrust plate is deformed in such a way that the inner surface area facing the pump chamber is displaced towards the pump insert, so as substantially to prevent the formation of a gap between the first thrust plate and the pump insert. As a result, the volumetric efficiency of the pump is improved. In addition, it is advantageous that because of the spacer means, a particularly precise machining of the housing is no longer necessary in that region in which the first thrust plate is supported by the spacer means. In known pumps a particularly flat design of this region was required so that the first thrust plate should rest or should be pressed uniformly against the ring and the pump insert.
In addition, in the pump according to the invention, it is advantageous that it is no longer necessary for the two thrust plates to be acted upon with the fluid pressure from the pressure region. As a result, the pump can be produced in a simple and inexpensive manner, since an outlay with respect to sealing need not be made for both of the thrust plates, as is required in the case of known pumps.
In a preferred embodiment the spacer means is made flat. This means that the face of the spacer means, on which the first thrust plate rests, is situated in one plane. As a result, the first thrust plate is deformed uniformly during operation of the pump. Alternatively, it is also possible, however, for the height of the spacer means to be varied in part. As a result, the deformation of the first thrust plate can be adapted to the suction regions and pressure regions of the pump. This means that the spacer means can have a lower height in the suction region than in the pressure region. As a result, the compensation of the gap can be adapted as a function of the pressure prevailing in the pump chamber or in the suction regions and pressure regions respectively. In addition, in a spacer means of differing height the lower portion of the spacer means is associated with the outer surface area of the first thrust plate. The lower portion acts as a stop for the first thrust plate when the maximum desired bending of the first thrust plate has been achieved. It is also possible, of course, to alter the position of the spacer means. This means that a position of the spacer means can be varied with respect to its distance from a drive shaft of the pump. As a result, it is possible to vary the effective lever arm of the thrust plate between the abutment region of the ring and the spacer means. In this way, the degree of deformation of the thrust plate can be altered.
In a further preferred embodiment the housing is provided with a cup-shaped recess which receives the first thrust plate at least in part. Since the housing can comprise two parts, the depth of the cup-shaped recess which receives the pump unit can be varied and so the separation plane between the housing parts can be shifted. A specially flat area on the base of the cup for forming an abutment for the first thrust plate is not necessary in the pump according to the invention. It is also advantageous that the housing of the pump according to the invention need not be constructed with a particularly high degree of rigidity, since deformation of the housing does not result in an increased formation of a gap between the movable parts of the pump insert and the thrust plates. This means that, since the second thrust plate acts upon the ring which in turn exerts a force upon the first thrust plate, the pump unit can be displaced inside the housing, so that yielding of the housing as a result of deformation is compensated by the pump unit following after.
In a preferred embodiment the spacer means is made continuous, and in particular as a closed curve.
In this way, a particularly uniform abutment face can be produced, so that the first thrust plate is deformed uniformly during the operation of the pump. In particular, the spacer means may have an annular or oval curve shape. As a result, adaptation to different cross-sections or profiles of the ring or the through opening is possible. The radius of the continuous spacer means can of course be varied, so that in this case too it is made possible to alter the effective lever arm.
In a preferred embodiment, the first thrust plate and the housing together with the spacer means bound a space in the radial direction which is connected to the pressure region by a fluid connection. As a result, the deformation of the first thrust plate during operation can be deformed in addition to the application of f

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