EP0231610A2

EP0231610A2 - A centrifugal pump

Info

Publication number: EP0231610A2
Application number: EP86309320A
Authority: EP
Inventors: Jose Pages Pages
Original assignee: Bombas Electricas SA BOELSA
Current assignee: Bombas Electricas SA BOELSA
Priority date: 1985-11-29
Filing date: 1986-11-28
Publication date: 1987-08-12
Also published as: PT83805B; PT83805A; EP0231610A3

Abstract

A centrifugal pump comprises a pump body (24) defining a pump chamber (3), an electric motor (4) having a housing and a drive shaft (5), an impeller (6) which is mounted on the shaft (5) inside the chamber (3), a first plate (14) which is joined to the pump body (24) and the motor housing, and a second plate (15) which separates the chamber (3) from the motor (4).

To prevent the radially inner periphery of the second plate (15) being displaced by pressure inside the chamber (3), the first plate (14) has a portion (20) supporting the second plate (15).

Description

This invention concerns a centrifugal pump comprising a pump body defining a pump chamber, an electric motor having a housing and a drive shaft, an impeller which is mounted on the shaft inside the chamber, a first plate which is joined to the pump body and the motor housing, and a second plate which separates the chamber from the motor.
Such a pump may be a water recirculation pump for a swimming pool with a pre-filter.
Pumps of this type suffer from drawbacks amongst which maybe singled out the following:

- The water passing through the chamber exerts a force on the second plate which may even cause this plate to become detached from the conventional mechanical ceramic seal of the impeller.
- The mechanical seal becomes exposed when for any reason the amount of water in the pump is less than half the volume of the pump body, which means that this seal may become overheated and lose its sealing capacity.

The invention is characterised in that the first plate supports the radial inner periphery of the second plate against movement caused by pressure inside the chamber.
With this construction, the second plate is prevented from becoming detached from the impeller seal.
Preferably the second plate provides a curved radially extending baffle plate in the pump chamber .
With this feature, in use of the pump, water is directed bv the baffle plate up to the seal preventing it from becoming overheated.
Embodiments of the invention will now be described by way of example, reference being made to the accompanying drawings of which:

Figure 1 is a longitudinal section of a centrifugal pump;
Figure 2 is a longitudinal section of another pump without the shaft, the impeller or the mechanical seal;
Figure 3 is a sectional view of the separating plate shown in Figure 2, taken on III-III and to a slightly enlarged scale; and
Figure 4 illustrates a perspective view of a part of this separating plate.

The centrifugal water recirculation pump illustrated in Figure 1 comprises a pump 1 and a pre-filter 2, with a pressure chamber 3 provided between the two.
The pump 1 is equipped with an electric motor 4 with a shaft 5 on which is mounted a multi-vane impeller 6 for rotation inside a diffusion chamber 7, partly sealed by a diffuser 8.
The liquid enters coaxially to the impeller 6 and is delivered under centrifugal force to the pressure chamber 3, provided between the electric motor 4 and the pre-filter 2.
The pre-filter 2 comprises a vertical filter bowl 9, placed inside an outer bowl 10 hermetically sealed by an externally screw-threaded cap 11 and provided with an external intake mouth 12 and an outlet pipe 13 connected to the axial inlet of the impeller 6.
The liquid sucked in has to pass through the walls of the filter bowl 9 before reaching the pump 1.
The pump has a body 24, which is connected with the pre-filter 2 and is linked to the housing of the electric motor 4 by means of a truncated cone-shaped coupling first plate 14. The pressure chamber 3 and the electric motor 4 are hermetically separated by means of a separating second plate 15.
The second plate 15 comprises radially inner and outer truncated generally conical portions with an annular portion joining them. The inner portion widens towards the impeller 6 and the outer portion widens in the opposite direction.
The plate 15 is also provided with a centre hole and is so arranged that its outside edge 16 is held, with a seal 17 inserted, between the respective adjacent edges of the coupling plate 14 and the pump body piece 24. The edges of this centre hole receive a conventional mechanical ceramic seal 18 for the impeller 6.
The shaft of the impeller 6 is fitted with a hollow cvlindrical extension 19 which fits on the motor shaft 5. The length of the extension 19 is such that its inner end lies between the mechanical seal 18 and the electric motor 4.
The truncated cone-shaped coupling plate 14 is provided with a centre portion 20 in the form of a horizontal cylindrical neck whose outer free edge 21 rests against the wall of the plate 15, in the radially inner peripheral portion 22 around its centre hole. The horizontal cylindrical neck extends around part of the hollow cylindrical extension 19 of the impeller shaft, which is thereby inserted in the neck 20.
This arrangement prevents the pressure of the water passing through the pressure chamber 3, which is exerted mainly on the portion 23 of the plate 15 in the direction of the arrow F, from eventually detaching the spacer from the seal 18.
The pre-filter 2 and the pump body 24 are linked together by means of a short horizontal tubular portion 25, which forms a single integral body with the pre-filter 2 and the pump body 24.
Figures 2, 3 and 4, show a centrifugal pump which comprises an electric motor 4 with a shaft on which is mounted a multi-vane impeller (not shown) for rotation inside a diffusion chamber partly sealed by a diffuser 8.
The pump also comprises a pump body linked to the housing of the electric motor 4 by means of a preferably aluminium, truncated cone-shaped coupling plate 14.
The pressure chamber and the electric motor 4 are separated by means of a plate 15, provided with a centre hole 26 and arranged so that its outer edge 16 is held, with a seal 17 inserted, between the respective continuous edges 27 and 28 of the coupling plate 14 and the pump body.
The edges of the centre hole 26 hold a conventional mechanical ceramic seal (not shown) for the impeller.
The plate 15 is provided, in its concave part facing the diffusor 8, with a curvoconcave radially extending baffle plate 29, which extends from the annular joining portion 30, between the two conical parts of the plate 15, to the centre of the plate, near the mechanical seal.
A shallow recess 31 is provided in this annular portion 30, adjacent to the radially outer end of the baffle plate 29.
The radially extending free edge 32 of this baffle plate 29 lies in a plane somewhat further from the mechanical seal than the plane containing the annular portion 30 between the two conical parts of the plate 15.
The seal 17 is provided with a U-shaped cross-section and receives the outer peripheral edge 16 of the plate 15 in a tight fit inside the ring groove determined by this U configuration.
The radially inner first limb of the seal 17 is adjacent to and applied against the pump chamber inside face 33 of the plate 15, whilst the radially outer second limb 34 of the seal 17 fits tightly into a ring groove machined in the edge 28 of the pump body.
The outside faces of the centre portion and the first limb of the seal 17 are applied against a peripheral angle edge of the coupling plate 14.
The arrangement of the baffle plate 29 on the plate 15 prevents the mechanical seal from becoming overheated through being left exposed and not cooled when the pump has, for any reason, an amount of water less than half the volume of the pump body, since the water circulating by the impeller is sent to the diffuser and part of this water is directed by the baffle 29 up to the mechanical seal, which is thereby cooled sufficiently.

Claims

1. A centrifugal pump comprising a pump body (24) defining a pump chamber (3), an electric motor (4) having a housing and a drive shaft (5), an impeller (6) which is mounted on the shaft (5) inside the chamber (3), a first plate (14) which is joined to the pump body (24) and the motor housing, and a second plate (15) which separates the chamber (3) from the motor (4), characterised in that the first plate (14) supports the radial inner periphery of the second plate (15) against movement caused by pressure inside the chamber (3).

2. A pump as claimed in Claim 1 and including a pre-filter (2), characterised in that the pump body (24) and the pre-filter body (10) are a single integral body.

3. A pump as claimed in either preceding claim, characterised in that the second plate (15) provides a curved radially extending baffle plate (29) in the pump chamber (3).

4. A pump as claimed in Claim 3, characterised in that the second plate (15) comprises radially inner and outer truncated generally conical portions with an annular portion (30) ioining them, the inner periphery of the second plate (15) receives a seal (18) for the impeller (6), and the radially extending free edge (32) of the baffle plate (29) lies closer to the annular portion (30) of the second plate (15) than_to the seal (18).

5. A pump as claimed in any preceding claim, characterised in that a seal (17) is located at the ioint of the pump body (24) and the first plate (14), which seal (17) is generally U-shaped in section with radially inner and outer axially extending limbs and a central connecting portion, the outer periphery (16) of the second plate (15) lies between the limbs, the radially inner limb lies between the pump chamber face (33) of the second plate (15) and a part of the first plate (14), the radially outer limb (34) extends into a groove in the pump body (24) and the central portion lies between confronting faces of the first plate (14) and the pump body (24).