GB2255593A

GB2255593A - Centrifugal pump for a dishwashing machine.

Info

Publication number: GB2255593A
Application number: GB9208522A
Authority: GB
Inventors: Ugo Favret
Original assignee: Zanussi Elettromeccanica SpA
Current assignee: ACC Compressors SpA
Priority date: 1991-04-23
Filing date: 1992-04-21
Publication date: 1992-11-11
Anticipated expiration: 2012-04-21
Also published as: FR2675852B3; FR2675852A1; DE9205330U1; ITPN910012U1; ES1020888Y; ITPN910012V0; IT225643Y1; ES1020888U; GB2255593B; GB9208522D0

Abstract

The pump has an intake 5 disposed centrally on a front wall 13 of a volute casing 12 which accommodates a rotor 10 and which is formed by at least two complementary portions 16, 17 which are coupled at a plane parallel to the axis 15 of the rotor. The volute casing is of a constant axial length which is greater than that of the rotor. The latter is provided with a peripheral collar 14 which projects towards said front wall and adjacent thereto, adapted to prevent a return flow of the water under pressure towards the intake. <IMAGE>

Description

CENTRIFUGAL PUMP IN PARTICULAR FOR A DISHWASHING MACHINE The present invention relates to a centrifugal pump which can be used in particular but not exclusively as a pump for circulating the water in a domestic dishwashing machine.

As described for example in GB-B-2049406, the circulating pump of a dishwashing machine is preferably installed with its axis horizontal and it is provided with a volute casing of plastics material which is formed by two coupled portions which meet at a substantially horizontal plane parallel to the axis of the rotor. That permits easy access to the interior of the pump, for example for cleaning and/or repair operations, by removal of the upper portion of the volute casing from the interior of the washing tub.

It is known that, unlike centrifugal pumps in which the volute casing is formed by two portions which meet at a plane which is transverse to the axis of the rotor, centrifugal pumps of the above-indicated kind suffer from constraints in respect of shape of the complementary portions of the casing, so as to permit simple and correct movement of the elements of the mould used for producing the casing itself. That is in conflict with some hydraulic requirements.

In actual fact, it is known that, in order to achieve a high static pressure (that is to say, a strong head) and low speed of the water (that is to say, a reduced pressure drop) at the delivery of a centrifugal pump of reduced size, it is necessary for the volute casing of the pump to be of a substantial cross-section in the internal peripheral region. For reasons of space, the radial dimensions of the volute casing must be limited so that it is possible to increase the above-mentioned cross-section only by increasing the axial dimensions thereof. On the other hand, the central portion of the volute casing (at which the rotor is disposed) is to be of limited axial dimensions in order to prevent part of the water under pressure in the interior of the casing undesirably flowing back towards the intake of the pump which is disposed at a central location.

As already stated, it is practically impossible by moulding to produce a volute casing which has a peripheral region which is axially longer than its central portion when the volute casing is formed by two complementary portions which can be coupled at a plane which is parallel to the axis of the pump.

The aim of the present invention is that of providing a centrifugal pump, in particular for a dishwashing machine, which provides satisfactory levels of hydraulic performance while being provided with a volute casing which can easily be produced by moulding and which is substantially formed by complementary portions which can be coupled at a plane which is parallel to the axis of the pump.

In accordance with the invention there is provided a centrifugal pump, having an intake section provided centrally on a front wall of a volute casing which accommodates a rotor and which is formed by at least two complementary portions coupled at a plane which is substantially parallel to the axis of the rotor, wherein said volute casing is of a substantially constant axial length which is substantially greater than the axial length of the rotor, the rotor being provided with at least one collar projecting towards said front wall and adjacent thereto.

The features and advantages of the invention will be clearly apparent from the following description set forth solely by way of non-limiting example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a dishwasher provided with the pump according to the invention, and Figure 2 is a diagrammatic view in longitudinal section on an enlarged scale of the pump shown in Figure 1, in accordance with a preferred embodiment.

With reference to the drawings, the centrifugal pump 6 according to the invention is particularly suitable for use as the circulating pump in a dishwashing machine comprising primarily a washing tub 3 (of which only part is shown in Figure 1) which in turn is provided in its lower part with a bowl 4 for collecting the washing and rinsing water. The bottom of the bowl 4 communicates with the intake section 5 of the centrifugal pump 6, which is disposed with its axis 15 substantially horizontal and which is driven by an electric motor 7.

The centrifugal pump 6 comprises a hydraulic rotor 10 which is connected to the drive shaft 11 of the motor 7 and accommodated in the interior of a pressure chamber or volute casing 12 which is in the shape of a spiral. In particular, as shown in the drawings, the cross-section of the casing 12 extends with a progressively increasing radius towards the delivery 8, describing what is referred to as an 'Archimedes spiral'. The intake 5 is disposed at a central position of a front wall 13 of the casing 12 while the delivery 8 of the pump is capable of feeding at least one rotary arm assembly 9 for spraying in known manner the crockery (not shown) to be washed which is disposed in the tub 3.

In per se known manner the casing 12 is preferably made of plastic material and is substantially formed by at least two complementary portions 16 and 17, being a lower portion and an upper portion respectively, which are coupled at a plane which is substantially parallel to axis 15 of the pump and which preferably passes therethrough. As already stated, a volute casing of that type is described for example in the above-mentioned GB-B-2049406 and makes it possible to have convenient access to the rotor 10 by removing the upper potion 17 of the casing 12 from the interior of the washing tub 3.

In order easily to produce the complementary portions 16 and 17 by simple moulding operations, the axial length LC of the parts of the complementary portions 16 and 17 which define the volume surrounding the rotor is substantially constant for both portions, i.e. does not substantially vary with radial and circumferential position relative to the pump axis, as shown in Figure 2. In addition, in order to achieve a high static pressure and a low speed for the water at the delivery 8, the abovementioned axial length is relatively high, being substantially greater than that, LR, of the rotor 10.

In accordance with a feature of the invention the rotor 10 of the centrifugal pump comprises at least one collar 14 which projects towards the front the front wall 13 of the casing 12 and adjacent thereto. Preferably the collar 14 is provided in cantilever relationship on the rotor 10 at a peripheral position.

In operation, it will be apparent that the collar 14 substantially prevents the water under pressure in the peripheral region of the casing 12 from flowing back towards the intake 5 through the gap defined between the rotor 10 and the front wall 13. In that way the centrifugal pump according to the invention, being of particularly simple structure, can advantageously maintain high levels of hydraulic performance.

It will be appreciated that the centrifugal pump described may be the subject of numerous modifications which fall within the scope of the invention and may be used in different applications.

Claims

1. A centrifugal pump, having an intake section provided centrally on a front wall of a volute casing which accommodates a rotor and which is formed by at least two complementary portions coupled at a plane which is substantially parallel to the axis of the rotor, wherein said volute casing is of a substantially constant axial length which is substantially greater than the axial length of the rotor, the rotor being provided with at least one collar projecting towards said front wall and adjacent thereto.

2. A centrifugal pump according to claim 1 wherein said collar is disposed in cantilever relationship on said rotor at a peripheral position.

3. A centrifugal pump constructed and arranged to operated substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

4. A dishwashing machine incorporating as a recirculation pump, a pump according to any one of the preceding claims.