Centrifugal Leakproof Fluid Pump

Abstract

The invention relates to centrifugal leakproof fluid pumps. The pump has a device for balancing the axial forces acting on the rotor, said device being made in the form of two partitions installed on the inner face walls of the pump casing in the spaced between these walls and the impeller discs; the sealing projection of each disc has a circular groove located on the outer surface of the projection and creating, when the rotor is shifted, an additional flow of fluid which brakes the fluid flow between the impeller disc and the partition.

Description

The present invention relates to centrifugal leakproof fluid pumps. The invention can be utilized in handling various chemically active liquids, such as liquefied gases, condensates, petroleum products, etc., whose leaks are strongly objectionable. Most efficiently, this invention can be used when it is embodied as a single-stage pump.

The centrifugal leakproof pump known in the art comprises a device for balancing the axial forces acting on the rotor, whose shaft carries an impeller consisting of two discs with blades in between, each disc having a circular projection, sealing a gap between the casing and the disc. In this pump, projections are made on the impeller for balancing the axial forces, acting on the rotor, the projections being made in such a manner, that relatively small gaps are made between them and the casing. When the rotor is moved by the axial forces one of said gaps is reduced, and simultaneously the liquid being handled creates increased pressure in the space adjacent to said gap. Under the action of this pressure the rotor together with the impeller is moved to the opposite direction (see, for example, the pump produced by KSB, type CM, Federal Republic of Germany). However, the axial clearances in the bearing pivot of the known pump are small, therefore its parts have to be manufactured and assembled with a high degree of precision. Moreover, the bearing pivot operates in contact with the fluid handled, this fluid not possessing, as a rule, lubricating properties; therefore, in view of small axial clearances, friction is occasioned between the bearing surfaces which leads to their rapid wear.

An object of the present invention resides in eliminating the aforesaid disadvantages.

The main object of the invention consists in providing a centrifugal leakproof pump with such a device for balancing the axial forces acting on the rotor in which there would be no friction between the bearing surfaces which would extend considerably the life of the pump.

This object is achieved by providing a centrifugal leakproof fluid pump, preferably of a single stage design, comprising a device for balancing the axial forces acting on the rotor whose shaft carries an impeller having two discs with blades in between, each disc provided with a circular sealing projection; according to the invention, the device for balancing the axial forces acting on the rotor is made in the form of two partitions installed in the spaces between the inner face walls of the pump casing and the impeller discs; each sealing projection has a circular groove on its outer surface, preferably at the base of the disc and creating, while the rotor is moved by the axial forces, an additional flow of fluid, which brakes the flow of fluid between the impeller disc and the partition, caused by the rotation of the impeller.

It is desirable, that the width of the circular grooves on the sealing projections of the impeller discs would be not smaller than the width of the passage between the partition and the inner face wall of the pump casing.

The centrifugal leakproof fluid pump according to the invention has a device for balancing the axial forces acting on the rotor which is simple in design, does not require high precision in manufacture and assembly, extends the service life of the pump owing to the elimination of friction in this device, and takes the axial loads acting on the rotor within the entire range of pump capacities. The pump according to the invention renders reliable service both in horizontal and vertical positions.

Now the invention will be described in detail by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a cross section of the centrifugal leakproof single-stage fluid pump, according to the invention;

FIG. 2 is a cross section of a part of the centrifugal leakproof single-stage pump with a device for balancing the axial forces acting on the rotor (enlarged).

The casing 1 (FIG. 1) of the pump mounts an electric motor 2 with a rotor 3 and a stator 4. The shaft 5 of the rotor 3 carries an impeller 6 consisting of two discs 7 and 8 with blades 9 installed between them. Inside the casing 1 there is a device for balancing the axial forces acting on the rotor 3, said device made in the form of partitions 10 and 11 installed on the inner face walls 12 and 13 of the casing 1 in the spaces between these walls and the discs 7 and 8 of the impeller 6. There are passages 14 and 15 between the partitions 10 and 11 and the face walls 12 and 13, whereas there are passages 16 and 17 between the discs 7, 8 and the same partitions.

The discs 7, 8 have circular sealing projections 18 and 19 whose outer surfaces at the base of the discs have circular grooves 20 and 21 of identical width, width b.sub.1 (FIG. 2) of each groove 20 and 21 being not smaller than width b.sub.2 of each of the passages 14 and 15. While the rotor 3 (FIG. 1) is being moved by the axial forces, these grooves create additional flows of fluid in the casing 1.

The casing 1 has a suction pipe 22 and a discharge pipe 23.

The shaft 5 is installed in bearings 24 and 25 accommodated in a sleeve 26 which protects the pack 27 of the stator 4 with the winding 28 against the effect of the handled fluid which is used for the lubrication of said bearings. The pack 30 of the rotor 3 accommodated in the sleeve 26 closed with the cover 29 is protected against the effect of the handled fluid by the sleeve 31 and rings 32 and 33. Both sleeves 26 and 31 are made of a nonmagnetic material, and installed with a gap through which the handled fluid is delivered to the bearing 25. The shaft 5 at the side of the bearing 25 is mounted with a disc 34 intended to limit the axial movement of the rotor 3.

The pump operates as follows:

As the winding 28 of a stator 4 is energized, the rotor 3 starts rotating with the impeller 6. The fluid entering the suction pipe 22 is delivered by the impeller 6 into the discharge pipe 23 from which part of the fluid is taken off through the pipe 35 for cooling the electric motor 2 and lubricating the bearings 24 and 25.

The fluid in the passages 16 and 17, is caught by the impeller discs 7 and 8 and begins rotating so that the pressure in these passages becomes nonuniform, diminishing from the periphery of the impeller 6 towards its center. The fluid in the passages 14 and 15 is not put in rotation so that pressure in these passages is actually constant between the periphery of the impeller 6 and its center.

The rotation of the impeller 6 creates an axial force which shifts the rotor 3 along its axis of rotation, for instance to the left, as shown in FIG. 2.

The passage 15 will then be put in communication with the passage 17 through the circular groove 21. Due to a difference of pressures in these passages, the fluid flows from the passage 15 downwards around the partition 10 and through the circular groove 21 into the passage 17 and, meeting a flow of fluid in it, brakes this flow. Merging of these two flows increases the pressure applied to the disc 8 of the impeller 6, and the rotor 3 with the impeller 6 is returned to the initial position. A similar process takes place when the rotor 3 with the impeller 6 is displaced to the right.

Claims

We claim:

1. A centrifugal leakproof, fluid single-stage pump comprising a casing, a rotor and an impeller including two axially spaced discs with blades therebetween, and installed on the shaft of said rotor, and means for balancing the axial forces acting on said rotor, said means including two fixed annular partitions installed in the spaces between the inner face walls of the pump casing and said discs of said impeller with the sides thereof communicating with the discharge of the pump, and, two circular sealing projections on said discs of said impeller provided, each, with one circular groove on the outer surface, said grooves being located respectively at the inner portions of said discs and creating, when said rotor is shifted by the axial forces, a passage of varying restriction so that an additional flow of fluid passes in the passage between one of said discs of said impeller and one of said partitions, said axial forces being caused by rotation of the impeller.

2. A pump according to claim 1 wherein the width of the circular grooves on the sealing projections of the impeller discs is at least equal to the width of the passage between said partition and the inner wall of the pump casing.