GB2273959A

GB2273959A - Centrifugal pumps

Info

Publication number: GB2273959A
Application number: GB9325725A
Authority: GB
Inventors: Stephen John Court
Original assignee: COLBEC ENGINEERING Ltd
Current assignee: COLBEC ENGINEERING Ltd
Priority date: 1992-12-30
Filing date: 1993-12-16
Publication date: 1994-07-06
Anticipated expiration: 2013-12-16
Also published as: GB9325725D0; GB9227113D0; GB2273959B

Abstract

A centrifugal pump 1 for pumping hot liquids in hot drinks dispensers comprises a pump casing 2 having an inlet 3 and an outlet 4, a pump impeller 18 rotatable within the casing 2 to effect pumping of liquid from the inlet 3 to the outlet 4, and a motor having a rotor 19 within the casing 2 coupled to the impeller 18 and incorporating a magnet 30 and a stator 31 disposed externally of the casing 2 and incorporating a coil 36 which may be supplied with alternating current to effect rotation of the impeller 18 by magnetic interaction with the magnet 30 of the rotor 19. Furthermore a clamping ring 11 is provided for securing the casing 2 to a support member 8 having an aperture 9 therein by clamping an annular portion 10 of the support member 8 surrounding the aperture 9 between the casing 2 and the clamping ring 11 such that the inlet 3 extends through the aperture 9. Such an arrangement enables the pump to be supported within an aperture in a wall of a supply tank such that liquid is supplied directly from the tank to the pump inlet without the necessity for any connecting pipe or fittings between the tank and the pump. <IMAGE>

Description

"Centrifuqal Pumps" This invention relates to centrifugal pumps, and is more particularly, but not exclusively, concerned with such pumps for pumping hot liquids for example in hot drinks dispensers.

A conventional centrifugal pump for use in the supply of hot drinks in hot drinks dispensers comprises an impeller within a sealed pump casing and a motor disposed externally of the pump casing and arranged to drive the impeller by means of a shaft extending through a shaft seal into the casing. Such shaft seals are prone to failure in use, and in addition increase the bulk and cost of the assembly. Furthermore the pump casing is generally coupled to the hot drinks supply tank by a connecting pipe, and there is a tendency for temperature losses to occur during supply of the hot liquid from the tank to the pump casing.

U.K. Specification No. 1398364 discloses a motor and pump combination for a domestic fish tank in which the impeller is rotated by a rotor incorporating magnets within the casing and a stator disposed externally of the casing and operable to effect rotation of the impeller by the rotor.

It is an object of the invention to provide a centrifugal pump which is particularly suitable for use in a hot drinks dispenser.

According to the present invention there is provided a centrifugal pump comprising a pump casing having an inlet and an outlet, a pump impeller rotatable within the casing to effect pumping of liquid from the inlet to the outlet, a motor having a rotor within the casing coupled to the impeller and incorporating magnet means and a stator disposed externally of the casing and operable to effect rotation of the impeller by the rotor, and a clamping ring for securing the casing to a support member having an aperture therein by clamping an annular portion of the support member surrounding the aperture between the casing and the clamping ring such that the inlet extends through the aperture.

Such an arrangement enables the pump to be supported within an aperture in a wall of a supply tank such that liquid is supplied directly from the tank to the pump inlet without the necessity for any connecting pipe or fittings between the tank and the pump. This renders the assembly particularly compact, and means that cost savings result from dispensing with a connecting pipe or fittings. Furthermore, where the liquid to be pumped is at a temperature above ambient temperature, this arrangement ensures minimum temperature losses within the system. However it should be appreciated that the pump is also suitable for mounting at a distance from the tank or other source of liquid to be pumped in which case the pump may be supported by a support member separate from the tank and the inlet may be connected to the tank by an inlet pipe.

Preferably the clamping ring is secured to the casing by fixing means, such as one or more screws, extending between parts of the casing and the clamping ring arranged opposite one another through the aperture in the support member.

Most preferably the fixing means comprises at least one screw extending through a bore in the casing into a blind bore in the clamping ring. Where the pump is mounted on a wall of the supply tank with the clamping ring on the inside of the tank, such an arrangement ensures that the or each screw is not contacted by the liquid to be pumped so that the screws are not subject to chemical attack by the liquid.

Conveniently the casing consists of a main portion defining the outlet and a cover portion defining the inlet, the cover portion being clamped between the main portion and the clamping ring. The provision of a separate cover portion simplifies assembly of the pump.

Furthermore it is preferred that the impeller and rotor are mounted on a common shaft, and that the shaft is supported at one end by a first mounting part provided in the vicinity of the inlet and at the other end by a second mounting part provided on the inside wall of the casing at a position remote from the inlet.

Conveniently the shaft is fixed at its ends, and the impeller and rotor are mounted on the shaft by means of bearings so as to be rotatable on the shaft.

The impeller and the rotor may be integrally formed with one another, the magnet means of the rotor being constituted by a cylindrical magnet having diametrically opposing poles. In this case the shaft may extend through a central bore passing through the impeller and the rotor, the magnet on the rotor itself having a bore concentric with said central bore.

The stator may comprise a generally U-shaped former having opposite poles arranged with the rotor within the casing therebetween, and a coil surrounding an intermediate part of the former.

The invention also provides a centrifugal pump or a combination of a centrifugal pump and a supply tank on which the pump is supported, the pump comprising a pump casing having an inlet and an outlet, and a pump impeller rotatable within the casing to effect pumping of liquid from the supply tank by way of the inlet to the outlet, and the casing being secured to a wall of the supply tank having an aperture therein by clamping an annular portion of the wall surrounding the aperture between the casing and a clamping ring such that the inlet extends through the aperture.

In this case the impeller of the pump may be driven by a motor by way of a shaft seal extending through the wall of the casing, if desired.

In order that the invention may be more fully understood, a preferred centrifugal pump in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is an axial section through the pump secured to a tank wall; and Figures 2 and 3 are opposite end views of the pump.

Referring to Figure 1 the pump 1 comprises a casing 2 having an inlet 3 and an outlet 4. The casing 2 consists of a main moulded portion 5 defining the outlet 4 and additionally having a generally cylindrical part 6, and a separate moulded cover portion 7 defining the inlet 3.

The pump is shown supported by a side wall 8 of a supply tank having an aperture 9 therein. More particularly an annular portion 10 of the wall 8 surrounding the aperture 9 is clamped between the casing 2 and a clamping ring 11 with the interposition of an annular gasket llA the clamping ring 11 being secured to the casing 2 by three screws 12 (see Figure 3). Each screw 12 extends through a bore 13 in the main casing portion 5 into a blind bore 14 extending into a nipple 15 on the clamping ring 11. Thus the screws 12 are not contacted by the liquid being pumped.

It will be appreciated that, when the casing 2 is secured to the tank wall 8 in this manner, the inlet 3 extends through the aperture 9 in the wall so as to enable supply of liquid from within the tank directly to the inlet 3. Furthermore the cover portion 7 defining the inlet 3 is clamped between the main portion 5 of the casing and the clamping ring 11 with the interposition of 0-ring seals 16 and 17, and no additional fixing means is required for connecting the cover portion 7 to the main portion 5. Thus all parts of the assembly which are to be wetted by the liquid to be pumped are capable of withstanding chemical attack from the pumped liquid which will be rendered particularly corrosive when the liquid is hot.

A moulded impeller 18 integrally formed with a rotor 19 is mounted on a common shaft 20 so as to be rotatable therewith, the shaft 20 extending through a bore 21 in the impeller 18 and rotor 19, and the impeller 18 and rotor 19 being mounted on the shaft 20 by means of bearings 22 and 23. Furthermore the ends of the shaft 20 are fixedly held within support bushes 24 and 25 supported by mounting parts 26 and 27. The mounting part 26 is fitted within a bore 28 in the cover portion 7 and is formed with three radial vanes 29 permitting flow therethrough of liquid entering the inlet 3.

The rotor 19 incorporates a cylindrical permanent magnet 30 in the form of a thick-walled tube having diametrically opposing poles, the material of the rotor being moulded about the magnet. Furthermore the motor of which the rotor 19 forms a part also includes a stator 31 disposed externally of the casing 2 and connected to the casing 2 by screws 32. The stator 31 comprises a generally U-shaped former 33 having opposite poles 34 and 35 arranged with the cylindrical casing part 6 containing the rotor 19 disposed therebetween, and a coil 36 surrounding one arm of the former 33 and having leads 37 for supply of alternating current thereto.The arrangement of the stator 31 will be better appreciated by referring to Figures 2 and 3 showing end views taken respectively from the left and from the right in Figure 1 (although it should be appreciated that in each case the wall 8 has been omitted to make the figures easier to read).

In operation of such a pump the supply of alternating current to the coil 36 results in an alternating magnetic field between the poles 34 and 35 which in turn results in rotation of the impeller 18 by interaction of the alternating magnetic field with the magnetic field associated with the magnet 30 on the rotor 19. Rotation of the impeller 18 causes liquid to be drawn in from the supply tank through the inlet 3 and forces the liquid outwardly through the outlet 4 by centrifugal action. Liquid at the same time flows around the impeller 18 and rotor 19 to lubricate the bearings 22 and 23. Because of the small number of wearing parts and the fact that all parts wetted by the liquid are resistant to attack by the liquid, such a pump is capable of prolonged use without failure.

Claims

1. A centrifugal pump comprising a pump casing having an inlet and an outlet, a pump impeller rotatable within the casing to effect pumping of liquid from the inlet to the outlet, a motor having a rotor within the casing coupled to the impeller and incorporating magnet means and a stator disposed externally of the casing and operable to effect rotation of the impeller by the rotor, and a clamping ring for securing the casing to a support member having an aperture therein by clamping an annular portion of the support member surrounding the aperture between the casing and the clamping ring such that the inlet extends through the aperture.

2. A pump according to claim 1, wherein the clamping ring is secured to the casing by fixing means extending between parts of the casing and the clamping ring arranged opposite one another through the aperture in the support member.

3. A pump according to claim 2, wherein the fixing means comprises at least one screw extending through a bore in the casing into a blind bore in the clamping ring.

4. A pump according to any preceding claim, wherein the casing consists of a main portion defining the outlet and a cover portion defining the inlet, the cover portion being clamped between the main portion and the clamping ring.

5. A pump according to any preceding claim, wherein the impeller and rotor are mounted on a common shaft.

6. A pump according to claim 5, wherein the shaft is supported at one end by a first mounting part provided in the vicinity of the inlet and at the other end by a second mounting part provided on the inside wall of the casing at a position remote from the inlet.

7. A pump according to claim 5 or 6, wherein the shaft is fixed at its ends, and the impeller and rotor are mounted on the shaft by means of bearings so as to be rotatable on the shaft.

8. A pump according to claim 5, 6 or 7, wherein the impeller and the rotor are integrally formed with one another, the magnet means of the rotor being constituted by a cylindrical magnet having diametrically opposing poles.

9. A pump according to claim 8, wherein the shaft extends through a central bore passing through the impeller and the rotor, the magnet on the rotor itself having a bore concentric with said central bore.

10. A pump according to any preceding claim, wherein the stator comprises a generally U-shaped former having opposite poles arranged with the rotor within the casing therebetween, and a coil surrounding an intermediate part of the former.

11. A centrifugal pump or a combination of a centrifugal pump and a supply tank on which the pump is supported, the pump comprising a pump casing having an inlet and an outlet, and a pump impeller rotatable within the casing to effect pumping of liquid from the supply tank by way of the inlet to the outlet, and the casing being secured to a wall of the supply tank having an aperture therein by clamping an annular portion of the wall surrounding the aperture between the casing and a clamping ring such that the inlet extends through the aperture.

12. A pump according to claim 11, wherein the impeller of the pump is driven by a motor by way of a shaft seal extending through the wall of the casing.

13. A centrifugal pump substantially as hereinbefore described with reference to the accompanying drawing.