CA1044515A - Electromagnetically driven pumps - Google Patents

Abstract

A B S T R A C T
The invention resides in a rotary machine in which an electromagnetic spherically shaped armature and a pump impeller being enclosed in a casing are borne, as a unit, by a frusto-spherical bearing of which the convex (or ball) part rotates, and in which frictional rotatable seal means are carried by an annular wall extending inwardly of the casing between armature and impeller supports the fixed bearing part and sealing-means which isolate the spaces in which run the armature and the impeller respectively.

Description

104~5~5 ~ac~round of the invention ~he invention is related to machines which are or ::
include electromag~etica~ly driven pumps or compressors .~ (hereinafter for brevity termed "pump") for~fluids, in which . an electric rotating armature forms in effeot a single rotatlng unit with the pu~p impeller or runner and~is borne by a frusto-spherlcal surface and wherein the armature is separated from the electric:motor stator by a magne.tically ~: permeable fluid-tight wall located in the space usually ` .
20: called the "air gap" (though we are not conce~rned here with :~
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air as such). .:
In some such machines the pump may be driven by a ~:: rotating concave pole ring (or"field") of permanent ma8netic ~:
material, arranged outside the wall and itseIf driYen by a 25~ separate source such as an electric motor or other mechanical -drive source: in such case, the two relatively rotatable , magnetic elements constitute a coupling rather than a : .motor; and in the following the terms"motor" and "coupling"
. are when contextually appropriate, regarded as including both~ .
~ 0 ~he rotary unit or assembly of such machines is subject 3 ~ to axial magnetic forces, i.e. to axial thrust in one sense , of direction.
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~04~S15 in such ~achine~
Putnps/are usually ~uch that the impeller i9 sub~ect to hydraulic force (the ter~ includes fluid force) which is opposed in sense to the magnetic force thrust above ~entioned.
At high delivery pressures the i~peller, and therefore the rotating unit of which it is a part, is subject to a hydraulic thrust towards the intake side or "eye" of the pump casing.
If this hydraulic thrust exceeds the magnetic thructt force , . .
I above mentioned, then the known bearing arrangement consist-t ing of comple~entary concave and convex frusto-spherical components is no longer effective. ~his results in a design ~;
limitation in such machines.
~he present invention seeks to avoid such limitation making it practicable to construct pumps particularly those intended for large output and maybe those wherein a high ~;luid pressure is generated. ~-A further drawback of previously proposed pumps is their sensitivity to contamination of the pumped fluid especially if such contamination lncludes magnetically ~ , . . . ~ . .
responsive particles. Contaminant particles are apt to be deposited in the "air gap".
In order to avoid these drawbacks, the invention providesthat :~ .
a second wall, which is stationarily mounted between the armature and the impeller, is provided with a seal; affording rotational freedom which seal includes part of the frusto-sphericalsurface of the bearing and is resiliently loaded by the wall itself or resilient means carried by the wall.
~, Summary of the invention AccordinO to this invention, in a combined motor and pump in which the rotor (i.e. the magnetic armature and the impeller) i8 borne by a single spherical bearing there is provided a wall which hermetically separates the impeller ~j . , , ' .. ~: --3--., .

:., , 10D~45~5 chamber from the armature chamber, which wall is sealed to the convex element (ball) of the bearing, sealing being maintained by resilience either of the wall itself, or an elastic extension thereof (such as a bellows structure) or by sealing means which is axially loaded by a resilient ring such as an elastomeric O-ring.
The invention further includes the provision of additional bearing elements such as to resist the axial com-ponent of the magnetic forces. In this way, the support of the armature/impeller unit is ensured both during running and when switching off when there is no magnetic thrust. As soon as the hydraulic forces exert a preponderant (over the magnetic) thrust on the impeller in the sense of direction towards the intake or upstream side of the pump casing excede the axial ;
magnetic force the invention provides ~or a support by the bearing .
such bearing being supported by the intermediate walI. This -"bearing" may comprise a shaft seal, the components of which have complementary axially opposed surfaces. ;
Preferably, according to a broad aspect, the present invention provides an electromagnetically driven pump comprising a casing adapted to house a rotatable unit comprised by an impeller and an armature and having a fluid-inlet opening to lead fluid into the casing to the impeller in a direction - ~-parallel to the impeller axis of rotation; a stator having a ~-frusto-spherical magnetically effective surface ~complementary to that of the armature and spaced therefrom to form an air gap;
frusto-spherical bearing means for said rotatable unit, said means having its convex part rotatable with t~e said unit and its concave part non-rotatably mounted; a fluid-tight wall of frusto-spherical formation and of magnetically permeable material fixedly located in the air gap between the armature and the stator, and ~ ;
an annular second wall extending generally radially between the ~, :

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10~45~5 impeller and the armature, said second wall comprising an outer annular portion and an inner rotary frictional seal means arranged to be operative between said second wall outer portion and said rotatable unit and to be resiliently urged in a direction parallel to the axis of rotation of the machine and to allow appreciable precessional freedom of motion of the axis of rotation of the rotatable unit about the geometric centre of the frusto_conical bearing means, said seal means comprising an annular resilient portion of which the inner margin bears frictionally upon and in sealing contact with the convex part of said bearing means upon which said margin additionally exerts thrust upon said convex part in a direction parallel to the axis of rotation thereof, the stato~, rotatable unit, bearing and seal means all being constructed ~ -: ;
and assembled so that in their spherical relationship they are i . . . .
concentric. -~

Description of examples of the invention -'~
Examples of the invention will be described with the help of the accompanying drawings in which:
Figure 1 shows an arrangement in which the armature/
impeller unit is borne by a ball supported by a bearing cup which ^-is carried in an intermediate wall and in which there is a non-rotary seal.
Figure 2 shows an embodiment in which a rotary shaft seal is carried by the intermediate wall.
Figure 3 shows a variant of Figure 2 in which the bearing ball is comprised both in a bearing and a bearing seal.
Figure 1 illustrates a motorised centrifugal pump in . .

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which the impeller 1 is part of a unit rigidly asse~bled with the armature 2. The surface of the armature 2 facing the - -magnetically permea~e separating first wall 3 i~ frusto-spherical. The wall 3 i8 lccated in the air gap between the armature 3 and the stator. The stator consists of magneti-cally conducting poles 4, coils 5, and magnetic loop closure - . -element 6. A ball 7 being the rotatable part of the frusto~
spherical bearing i8 rigidly attached to the armature/ ~
impeller rotating unit 1-2 and is therefore itself rotating. : ;
In operation; the impeller 1 generates a fluid force, i.e.
thrust in the sense of the arrow 11, whilst there is mag-netically generated a thrust force in the (opposite) sense of the arrow 12.
The impeller 1 i6 attached to the armature 2 by a bolt 20, the ball 7 being fast with the bolt 20. The ball 7 i8 3i nested between.two non-rotating concave bearing cups 8 and 28. The bearing CUp8 8, 28 are carried by a fixed annular ..
second wall 29. A resilient portion 21, axially urges the . . .
.~ cups 8 and 28 towards each other iand against the surface of ii 20 the ball 7. The thrust forces ir, the senses of direction of :.~ the arrows 11 and 12iæe both reslsted by the frusto-spherical ~ . -bearing formed by the ball 7 and the cups 8, 28. A non-~: rotating seal ring 24 is pressed by an elastomeric 0-ring 25 against a plane surface of the ring 24 which ring 24 is in : turn elastically pressed against the bearing cup 28. The angle of wobbling or precession motion which the ball 7 (anarotor unit as a whole) can perfor~ in relation to the ~xis 26 is limited by the elasticity and limits of the ring 25.
The wall 29 preferably hermetically contains the pumped fluid medium, which, as is known in practice may contain abrasive, precip1tating, or otherwise conta~inating substances which may . -5-~, s . .

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include magnetic particles.
Figure 2 shows another embodiment of a motorised pump ~achine in which the i~peller 1 forms a rotary unit with the armature 2. The surface of the armature 2 complementarily ' ';' facing the magnetically perme~le separating wall 3 i9 ' . ~- ;
spheroidal. A stator is ~ituated to one slde of the wall 3. , ;, ~ ~
~he stator consists of magnetically conductive poles 4, - - -coil 5 and magnetic loop olosure element 6. The bearing '' ball 7 i8 attached fixedly to the rotating unit 1, 2, The ,' 10 ' ball 7 is borne by a concave bearing cup 26. This cup 26 is ',,'~' '' supported by the walI 3 throu~ha tubular element 27. An ` ,~
elastic bellows-type body 30 is attached to;the secdnd annular wall 29. The body 30 carries a sealing rlng 28 which presses axially against the flat annular surface of a~co-operating ;''~
~15 ~seal rlng 31.
In operation,'the impeller 1 generates flu1d-pressure ,' thrust force in the sense of the arrow 11, whilst~the arma~
ture 2 generates magnetic thrust foroe in the sense of arrow , 12, these forces being in general, axial in'respect~of the '~
~120 ~ rotation. The latter,force is resisted by the bearing cup ' ~' -' 26. When the force~along~arrow 11 exceeds the force along ,~ ,' rrow 12, the seal 31,; 28 supported by the bellows 30 resists this excess force.;
Fi~ure 3 shows a further variant of the machine in which ' 25 the ball 7 is both the rotating convex member of a bearing comprising the cupped end surface 50 of the bearing column ', 31 and also constitutes the~rotating member of a rotary seal, of which the ~tatinnary part is constituted by an annular second wsll part 35 sgainst which bears (at 34~ an axially elastic portion 33 of which the inner margin sealedly contacts ~ he ball 7 (for which reason the margin i preferably ~achine~ ~
i ~ . I ' ,~ '- ' 6 , , - - . ' ' ' i . ' ` " ' ' 10~45~.5 a9 a frusto-spher~cal surface, but it may be left as an edge which will rapidly adapt it~elf to sealing contact ~ -with the ball 7). ~;
The ele~ent 33 i~ preferably made ~ery thin and of a , ~, hard though elastic ~aterial and is assembled normally in fluid-tight (but relief-valve like) manner, the element 33 acting as a wall partly defining a chamber, as the spring of a rotary seal, and as the spring of a one-way relief valve. , ~-The element 33 is therefore intended to be resiliently pre-lO , loaded in the axialsense, when assembled, against the edge 34 '' , of a relatively rigid intermediate annular second wall part 39.
' The armature 2 is shrunk on or otherwise rigidly,attached '' ,'~ , to the equator of the ball 7. A spindle 40 traverses the - ball 7. The spindle 40 carries on one side of the,ball 7 the ,', bladed impeller l and on the other side of the ball 7 is a , , ' ,' ~ ring 41 which holds the ball 7 in its axial position on the '',

3; spindle 40 by friction locking.
The stub 42 of the spindle 40 together with a bush 43 ~ , provide Iimitat1on of precessional wobbling of the armature/
~ , 20, impeller unit l, 2. The end of the spindle 40 is formed with ~' a square section at 44, which can fit into a square sectioned socket 45 s1tuated at the end of a rod 46.
By axial displace~ent of an externally àccessible hand-wheel 47, the rod 46, whioh is sealed by a rubber seal 48, ';
'~25 can be shifted axially far enough so that the armature/
impeller unit l, 2 oan be turned by hand should ocaasion arise, e.g. in case a foreign body has caused ~amming. , ,~ ~' ~ The rod 46 is~carried in a bush 49 in a manner such as '~ to allow rotary and axial motions. The bush 49 is fluid-tightly secured to the separating wall 3. 5'`' , The ele~ent 33 fuIfills four functions in this variant: , : , ,, ~ .

.','~;' .' ,' , , ' ' ' , ' , ~0~515 (a) it seal~ thè space 51 in which runs the armature 2 against possibly conta~inated fluid fro~ the space in which the bladed impeller 1 runs so as to prevent foreign ~atter fro~ reaching the air gap at 53.
/ (b) it prevents separation of the ball 7 from its com~
plemen~concave spherical bearing surface at 50.
(c) if an excess pressure forms in the space 51, for exa~ple because overheating causes the fluid in this space to evaporate, the ele~ent 37 acting like a relief valve lifts off the ball 7 and thus relieves excess pres~ure.
(d) if negative pressure ocours in the space ~51, for exa~ple ~. because previously for~ed vapour condenses - -after switching off the ~otor, the sealing dlsc 33 (acting as ~;~
a relief valve) suffers a s~all deflection so that its 5~ ~ periphery lifts off the edge 34 of the inter~ediate plate 39 ;
and allows passage of fluid.
In each variant the~casing 10 contains~the electric motor (for which of course all appropria~ provisiDn such as connectors will be made) and the i~peller. The nuid ~ -~
enters the casing lO through an axially-directed inlet eye lOA and the i~peller is, as shown, of centrifugal type.
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Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An electromagnetically driven pump comprising:
a casing adapted to house a rotatable unit comprised by an impeller and an armature and having a fluid-inlet opening to lead fluid into the casing to the impeller in a direction parallel to the impeller axis of rotation;
a stator having a frusto-spherical magnetically effective surface complementary to that of the armature and spaced therefrom to form an air gap;
frusto-spherical bearing means for said rotatable unit said means having its convex part rotatable with the said unit and its concave part non-rotatably mounted;
fluid-tight wall of frusto-spherical formation and of magnetically permeable material fixedly located in the air gap between the armature and the stator;
and an annular second wall extending generally radially between the impeller and the armature, said second wall comprising an outer annular portion and an inner rotary frictional seal means arranged to be operative between said second wall outer portion and said rotatable unit and to be resiliently urged in a direction parallel to the axis of rotation of the machine and to allow appreciable precessional freedom of motion of the axis of rotation of the rotatable unit about the geometric centre of the frusto-spherical bearing means, said seal means comprising an annular resilient portion of which the inner margin bears frictionally upon and in sealing contact with the convex part of said bearing means upon which said margin additionally exerts thrust upon said convex part in a direction parallel to the axis of rotation thereof;
the stator, rotatable unit, bearing and seal means all being constructed and assembled so that in their spherical relationship they are concentric.

2. A machine according to claim 1, in which additional bearing means are provided to restrict the rotatable unit from precession beyond a selected limit of angle.

3. A machine according to claim 1, in which there is further provided externally accessible means operable by movement axially in respect to the rotatable unit and so as to engage the rotatable unit and move it in relation to the stator whereby to release foreign matter which may lodge between rotor and stator element of the machine.

4. A machine according to claim 1 in which the said annular resilient portion is so adapted that it can operate as a relief valve should the pressure to which it is subjected so dictate.