GB2186635A - Centrifugal pump - Google Patents

Abstract

The pump comprises a sealed stator body (1) which contains a permanent magnet rotor associated with a dampened coupling impeller completed by an impeller cover (2), provided with suction and delivery fittings for the pump itself. The stator core (8) embraces the stator body (1) externally, so that it is out of contact with the liquid being pumped. The impeller has a conformation which enables easy expulsion of foreign bodies conveyed with the liquid and which provides a sufficiently tight fit on the stator body (1) to prevent such foreign bodies suspended in the liquid from reaching the bushes or the rotor supporting and guiding points, which would result in a faster pump wear rate. <IMAGE>

Description

SPECIFICATION Centrifugal pump particularly for washing machines, dishwashers, and household appliances providing liquid discharge cycles This invention relates to a centrifugal pump particularly suitable for use with washing machines, dishwashers, or other household appliances providing liquid discharge cycles.

In such household appliances as washing machines or dishwashers, pumps are normally employed which comprise an asynchronous motor of traditional configuration combined with a centrifugal pump.

In practice, the axle of the electric motor enters the pump body with the interposition of an annular or toroidal liquid seal which prevents the liquid from flowing out.

This seal represents one of the most critical areas of the motor-to-pump coupling and liquid leakage past this seal is one of the most frequently occurring and damaging failures since it usually results in the electric motor being damaged.

It should be further considered that the pump, especially if installed on washing machines for domestic use, is adversely affected by discharged liquid carrying sand, dust and the like particles suspended therein which have a damaging abrasive effect especially on the seals of the moving parts, as well as fiberous matter such as lint which, by twisting around the impeller and the pump axle cause serious trouble, and may even jam the pump.

The problem of a jammed pump in a washing machine or a dishwasher is not a minor one because, additionally to blocking the machine, it requires for its re-activation, the intervention of highly skilled personnel and/or replacement of parts of the machine itself.

Also from a production standpoint, the making of asynchronous motors and their association with pumps of the centrifugal type having a separate structure is particularly expensive.

It is an object of this invention to provide a pump so constructed as to exhibit none of the drawbacks of pumps presently used in household appliances.

A consequent primary object of the invention is to provide a pump whereby the liquid cannot reach the electric parts of the motor.

A further object of the invention is to provide a pump which can be made up of readily mass produceable parts at reduced costs.

Still another object of the invention is to provide a pump construction to be only minimally affected by the presence of sand, dust, or lint in the liquid being pumped.

A not least object of the invention is to provide a pump of very moderate cost.

These and other objects to become apparent herein below, are achieved by a centrifugal pump particularly for washing machines, dishwashers, and generic household appliances, characterized in that it comprises two complementary elements, as stator body and an impeller cover, which when assembled form a sealed body containing a permanent magnet rotor and a chamber containing an impeller associated with said rotor, being both mounted on an axle preferably rigidly associated with said stator body, said impeller being provided with means of preventing granular matter from entering the stator body, and said rotor having dampened means of connection to the impeller, externally of said sealed stator body there being the electromagnetic portion of the motor.

Further features and advantages of the invention will be more clearly understood from a detailed description of a preferred embodiment thereof, given by way of illustration and not of limitation with reference to the accompanying drawing sheets, where: Figure 1 is a perspective view of the pump according to the invention; Figure 2 is a front view of the motor side of the inventive pump, with the magnetic circuit stripped of the electric windings; Figure 3 is a part-sectional view of the pump of this invention; Figure 4 is a sectional view taken on a plane containing the rotation axis, showing the impeller-to-rotor coupling area; Figure 5 is an exploded view of the rotor, damper, and impeller of the pump; Figure 6 is a front view of the upper portion of the rotor illustrating the means of damped connection to the impeller;; Figure 7 is a detail view of the impeller-torotor coupling; Figure 8 is a first variation of the impellerrotor assembly; Figure 9 shows a second embodiment of the stator body and of the means for supporting and guiding the rotor and impeller.

With reference to the cited drawing figures, the pump according to the invention comprises a complementary stator body 1 associable by means of screws with an impeller cover 2 which when assembled form a sealed body having an axial suction sleeve 3 and a radial delivery sleeve 4.

Both sleeves are formed in the impeller cover together with an annular impeller chamber 5 radiused to the delivery port.

The stator body 1 comprises substantially a plate-like element 6 perpendicular to a cylinrical body 7 containing the rotary portion of the motor, to be described, and which is embraced exteriorly by the stator laminations 8 on which the stator windings 9 are wound which terminate with two electric connectors 10.

To correctly hold the stator laminations or core 8 in position relatively to the cylindrical body 7, the latter is formed with two alignment fins 11 which serve as abutment ledges for the forward portion of the core 8 and to locate it.

Shown in Fig. 3 is a like solution for the pump, wherein the one difference from the illustrations of Figs. 1 and 2 is represented by the different location of the suction sleeve, here indicated at 3, which while being radiused axially to the chamber 5 of the impeller 12 is then bent to extend parallel to the platelike element 6.

These different conformations may be selected, however, to suit the installation requirements of the pump in the household appliance.

Inside the sealed body formed of the stator body 1 and the impeller cover 2, and more specifically inside the cylindrical body 7, there is contained a rotor 13 with permanent magnets 14 which has, in a first solution shown in Figs. 3, 4, 5, 6 and 7, an axial bore 15 through which a fixed supporting and guiding axle 16 is passed the bottom end of which is force fitted and retained in a groove formed on an axial lug 17 rigidly associated with the cylindrical body 7.

In this solution, therefore, the axle 16 is stationary and the rotor 13 is allowed to turn being supported and guided on the axle itself.

The rotor is formed by injecting plastics into a mould where the permanent magnets 14 are located as inserts.

To afford low friction and excellent alignment of the rotor 13, the bore 15 has, at its two extremities 18 and 19, a smaller diameter than the intermediate region 20, thereby providing in practice two narrow sliding regions indicated at 21 and 22.

With this solution it is unnecessary to interpose elements between the rotor 13 and axle 16.

In the upper portion, the rotor 13 has a deep annular groove 21 formed internally with a peripheral tooth formation 22 which enables a rubber or elastomer segment 23 to be positioned which is also expediently formed with a conforming tooth formation for retaining it in the groove 21 at the inserted position.

The top edge of said rotor 13 has a protruding toidal edge 24 which will serve for hooking on the impeller 12, as explained herein below.

The impeller 12, of the centrifugal type, has, in the instance considered, four radial vanes 25 set at 90" from each other and being associated with a central body 26 internally formed with an axial bore 27, adapted to accommodate a cylindrical extension 28 of the rotor 13.

Said central body 26 also has an annular groove 29 which is adapted to accommodate the upper region of the rotor 13, and in particular the toroidal edge 24 which is thus retained by an annular elevation 30, inside the annular groove 29.

From said central body 26 there also extends a lug 31 which fits into the annular groove 21, in the space left by the rubber segment 23.

In practice, the impeller 12 is formed from plastics and by utilising the deformability of this material, it can be associated with the rotor 13 by temporarily deforming the upper portion thereof and cooperating, expanding temporarily at the region 26 until the toroidal edge 24 and annular elevation 30 hook together.

This conformation of parts affords secure hooking of the impeller 12 to the rotor 13 while leaving the impeller 12 free to rotate relatively to the rotor 13.

Entrainment of the impeller 12 owing to the motion of the rotor 13 takes place on the lug 31 abutting on the elastic segment 23.

This conformation of parts has been studied for the reason that the electric motor with permanent magnet rotor is substantially of the synchronous type, and on starting, in order to set itself in synchronisation, should have the last pickup drag.

Having practically freed the impeller 12 from the rotor 13 over a smaller arc than 360 , starting, which may occur indifferently in the clockwise or counterclockwise direction, practically occurs with the impeller stationary, and it is only after the motor has picked up speed that this is entrained to move.

The segment 23, which forms the entrainment element for the impeller 12, on abutting with its lug 31, is elastic to dampen the impacts on the lug 31 and to suppress the noise from this connection.

In particular, the noisiness of the connection originates while the pump is not filled completely with water but has also air present therein with different and varying resistance over time.

In this case operation would occur very noisy objectionable.

It should be further noted that the bottom edge 32 of the central body 26 of the impeller 12 is extended to substantially touch the inside portion of the plate-like element 6 assuming the position shown in phantom lines at 33 in Fig. 7, when the impeller and rotor are inoperative.

Thus, dust or foreign bodies are prevented from entering the inerspace between the rotor 13 and the cylindrical body 7, which would result in deterioration of the sliding regions 21 and 22 between the rotor 13 and the axle 16.

After starting, owing to the suction vacuum effect, the impeller 12 moves up away from the inward portion of the plate-like element 6, as shown in Fig. 7, thus affording rotation without frictional contact.

It should be noted that the position of the rotor 13 inside the cylindrical body 7 is maintained by the magnetic action of the permanent magnets 14 with respect to the stator core 8.

Thus, there is the possibility of an elastic translation against the magnetic and electromagnetic forces generated by the stator core.

It should be a further noted that the pump is structured throughout in a fully symmetrical fashion, both in the impeller 12 and in the chamber of the impeller 5, since starting can occur indifferently either in a clockwise direction or a counterclockwise direction.

This is specially advantageous in that, should the impeller meet with an obstacle in one direction of rotation, and come to a stop, the motor can resume rotation in just the opposite direction to get rid of the obstacle and expel it.

This occurs particularly where the pump is employed in washing machines where the presence of lint or fiberous matter is likely to occur which may twist around the impeller and stop it.

At this point the motor, by restarting in the opposite direction, would unwind the lint that wound up, free itself of it, and expel it.

In the structure illustrated in this first embodiment it should be noted that the electric portion is left fully on the outside of the region affected by the liquid and that no bearing seals are provided in any way separating inner regions from outer regions and thus eliminating any problems of liquid leakage over time which could wet and ruin the electric winding beyond repair.

For this reason it is not even necessary to provide any more an earth tap because the parts under voltage are doubly isolated from the liquid circulating through the pump itself.

As for the hydraulic characteristics of the pump, being driven by a synchronous motor, it affords constant delivery rate as the supply voltage varies with considerable advantages in sizing it for the household appliances with which it is to be associated.

The choice of a permament magnet rotor affords a considerable reduction in power requirements over traditional pumps which may amount in practice to about one third that of a comparable pump of the usual asynchronous type.

Fig. 8 shows a first variation of what is illustrated in the preceding figures.

In this case the rotor 113 is again of the permanent magnet type practically identical of the one already illustrated also provided with an inside toothed groove 121 into which a damper 123 is inserted and associated with an impeller 112 quite identical to the one illustrated.

In this case the constructional diversity resides in that the ends of the axial bore 11 5 of the rotor 113 are enlarged and adapted to contain two metal bushes 133 preferably of a cylindrical or self-centering type which serve the function of affording perfect sliding over the axle, not shown, but which is perfectly identical function-wise and in arrangement of the already illustrated axle 16.

This solution may be convenient where the plastics from which the rotor is formed has insufficient mechanical characteristics such that it could be quickly deteriorated if allowed to rub on the fixed axle.

A further embodiment is illustrated in Fig. 9 where the parts have been studied with special attention to the need for preventing sand or foreign bodies from entering the region affected by the rotor and the sliding bushes.

In this case the axle now indicated at 216 is no longer fixed but is linked rigidly to the impeller 212 with which it rotates during the motion.

Said axle is supported downwardly by a first self-centering bush 234 secured to a groove 235 formed in the lower interior portion of the cylindrical body 207.

Upwardly during assembly there is inserted a sealing segment 236 which also has in the central region a second self-centering bush 237 which supports and guides the axle 216.

For improved safety a seal 238 may be provided which seals off foreign bodies in the region where the axle 216 moves out of the bush 237.

The rotor with permanent magnets 213 is mounted loosely on the axle 216 and has in its bottom region a lug 239 which interferes with a second radial lug 240 rigidly associated with the axle 216.

Also in this case, the rotor 213 may be started in either the clockwise or counterclockwise direction, and hooking to the impeller 212 rigid with the axle 216 will take place following an angle of free rotation.

Here too, the liquid will be prevented from reaching the electric parts esternal of the pump and damaging them.

The region affected by the rotor 213 may also be filled with the liquid since the function of the seal 238 and the segment 236 is more one of preventing the ingress of foreign bodies, sand, and dust than of liquid.

From all that has been described and illustrated in conjunction with the various versions proposed, it may be seen that all the objects set forth have been achieved and in particular that a pump has been provided which is especially suitable for use with such household appliances as washing machines, dishwashers, etc. with excellent electrical and mechanical characteristics.

In particular it should be noted that full separation of the liquid-affected portion from the electrical portion has been accomplished and that the moving parts have been protected against wear from sand, dust, etc.

The use of a permanent magnet rotor has afforded greatly reduced power requirements by the pump, the possibility of starting and turning indifferently in either directions brings about additional important advantages effective to avoid problems of jamming or clogging and the use of a synchronous type motor af fords hydraulic characteristics of flow rate advantageously unrelated to the supply voltage.

Of course, based on the same inventive concept the embodiment may assume different implementations all of which fall within the protection scope of this patent.

The materials and dimensions may be any ones depending on requirements.

Claims (14)

1. A centrifugal pump particularly for washing machines, dishwashers, and generic household appliances, characterised in that it comprises two complementary elements, a stator body and an impeller cover, which when assembled form a sealed body containing a permanent magnet rotor and a chamber containing an impeller associated with said rotor being both mounted on an axle preferably rigid with said stator body, said impeller being provided with means adapted to prevent foreign matter from entering the stator body and said rotor having dampened means of connection to the impeller, externally of said stator body thus sealed off there being provided the motor electromagnetic portion.

2. A centrifugal pump as in Claim 1, characterised in that said stator body comprises a cylindrical body associated with a plate-like element normal to its axis, the interior of said cylindrical body containing a permanent magnet rotor, with said plate-like element there being associated a cover forming the impeller chamber and being provided with an axial suction sleeve and a radial delivery sleeve.

3. A centrifugal pump as in Claim 1, characterised in that the stator core with the electric windings is placed outside said cylindrical body which is embraced by the pole pieces thereof, said stator core being held in place by alignment fins present on the outer surface of said cylindrical body and positioned at the forward edges of the stator core itself for which they form an abutment.

4. A centrifugal pump as in Claim 1, characterised in that in a first embodiment the rotor, formed by injecting platics with permanent magnets as inserts, has an axial bore adapted to contain the supporting and guiding axle which is stationary with respect to and rigidly associated with said cylindrical body, said bore having two end regions with a diameter substantially equal to the diameter of said axle and the intermediate region of a larger diameter, said end regions forming the rotor aligning elements.

5. A centrifugal pump as in Claim 1, characterised in that in the impeller side region said stator has an outer toroidal edge adapted to form the element for hooking on the impeller which has a middle body with which the vanes are associated, said body having an annular groove adapted to contain the upper portion of the rotor, it hooking thereon by means of an annular inner elevation cooperating with said toroidal body.

6. A centrifugal pump as in Claim 1, characterised in that said impeller after hooking on said rotor is allowed to rotate relatively thereto the hooking being no stable tie.

7. A centrifugal pump as in Claim 1, characterised in that in the upper portion on the impeller side said rotor has a deep inside toothed annular groove, into said groove there being inserted an elastic segment which occupies a reduced angle thereof.

8. A centrifugal pump as in Claim 1, characterised in that said impeller has a lug adapted to fit in said annular groove on said rotor, said lug being allowed to rotate through a smaller angle than 360" and interferring with said elastic segment which causes it to be entrained during the motion.

9. A centrifugal pump as in Claim 1, characterised in that the outer edge of said central body of said impeller, when assembled, practically flanks the inward portion of said platelike element, thus preventing foreign bodies from passing to the rotor's bearing region on the supporting axle from the impeller chamber.

10. A centrifugal pump as in Claim 1, characterised in that the rotor, impeller, and impeller chamber have symmetrical shapes allowing the combination to rotate either in a clockwise direction or counterclockwise direction without alteration of the electric and hydraulic characteristics of the combination.

11. A centrifugal pump as in Claim 1, characterised in that the rotor axial bore has its two ends of an increased diameter, said ends having two bushes inserted which are adapted to form the bearing elements on the fixed axle.

12. A centrifugal pump as in Claim 1, characterised in that in a further embodiment, the central axle is rigid with the impeller and mounted on a pair of self-centering bushes, while the rotor is mounted loose on said axle, said rotor having a lug on one of the two heads, said lug interfering with a second radial lug rigid with said axle, interference of the two lugs resulting in the impeller being entrained as the rotor turns.

13. A centrifugal pump as in Claim 1 and the preceding claim, characterised in that one of said bushes is mounted in the lower portion of said cylindrical body, whilst the second of said bushes is mounted on a cross segment interposed to the rotor and the impeller, said segment also having a seal on said impeller axle, said segment-seal combination preventing foreign bodies or sand from entering toward the bushes.

14. A centrifugal pump for washing machines, dishwashers, and generic household appliances, characterised in that it comprises one or more of the features illustrated and described.