Note: Descriptions are shown in the official language in which they were submitted.
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WO 99!10655 . PCT/GB98/02500
t IMPROVEMENTS TO ROTARY PUMPS
This invention relates to improvements to rotary pumps, and in
particular coolant pumps for combustion engines.
In a rotary pump it is common practice to provide a rotating
mechanical seal at the point where the drive shaft enters the body of
the pump.
In the internal combustion engine field where a rotary pump is
employed as the engine coolant pump, mechanical seals are by no
means wholly reliable. The sealing faces may film over with deposits
from chemicals held in solution - a situation familiar to the industry
known as filming which subsequently leads to sealing breakdown
and coolant leakage. The faces may fail prematurely and leak due to
excessive shaft run-out. The faces may also fail due to vibration
transmitted from ailing bearings which have been overloaded by over
zealous tightening of the drive belt. Additionally the faces may wear
out prematurely due to scoring caused by hard particles in the
pumped medium.
Quite apart from the reliability question, it is well known that
leakage past a mechanical seal cannot be eliminated entirely even
when the seal is in an as new condition. A mechanical seal consists
of two polished radial surfaces running adjacent to each other. Since
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the pressure of the pumped medium at the seal is different from the
pressure of the air outside the seal a pressure gradient is set up across
the seal faces between which slow leaking or weeping is apt to occur.
It is therefore evident that a slightly weeping mechanical seal is not
always indicative of a failed seal. However, a common misconception
is that any signs of weeping indicates a failed seal. A perfectly
serviceable coolant pump assembly is thus often needlessly replaced.
However, it is also known to provide a sealless pump which
employs a magnetic coupling comprising a driving and a driven
magnetic member which couple with one another through a static,
hermetically sealed container or containment shroud. Accordingly, the
static container prevents leakage since it is a non-moving part. The
disadvantage with conventional magnetic couplings is that they are
bulky. Because of an ever-increasing need to reduce the space
occupied by the internal combustion engine in its engine
compartment, is has not been feasible to accommodate a known
magnetic coupling between the pulley or the gear drive system and
the coolant pump.
Accordingly, the invention seeks to avoid or at least mitigate
the problems in the known art. An object of the invention is to
provide a sealless coolant pump of the type described comprising a
magnetic coupling suitable for use with an internal combustion
engine. r
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One aspect of the invention provides a sealless coolant pump
comprising a pulley assembly having a pulley for co-operation with a
~ drive belt and a driving magnetic member, a pump body housing a
driven pump member attached to a driven magnetic member, which
co-operates with the driving magnetic member through a static
container attached to the pump body, wherein the pulley assembly
and driven pump member are rotatable about a common axis, and the
pulley. driving magnetic member. and driven magnetic member are
substantially radially aligned or superpositioned with respect to said
common axis. Beneficially, a sealless coolant pump having a
reduced axial length is thereby provided compared to known pumps.
The driving magnetic member can be radially outward of the
driven magnetic member. In another form, the driving magnetic
member can be radially inward of the driven magnetic member. In
this form, the pulley assembly can comprise an annulus for carrying
the driving magnetic member. The annulus can carry part of a
bearing for co-operating with part of the bearing,carried by the static
container. Preferably the static container comprises a centrally
protruding portion which operably carries a bearing for co-operating
with the pulley assembly. Also, the driven pump member can
comprise a shaft which is rotatable about the common axis which
shaft protrudes axially in to said centrally protruding portion of the
static container.
A second aspect of the invention provides a sealless coolant
pump comprising a pulley assembly having a pulley for co-operating
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with a drive belt and a driving magnetic member, a pump body
housing a driven pump member attached to a driven magnetic
member which co-operates with the driving magnetic member
through a static container attached to the pump body, wherein the
driving magnetic member and driven magnetic member are
substantially radialIy aligned and the driving magnetic member is
radially inward with respect to the driven magnetic member.
Beneficially, this configuration enables the pulley assembly to
comprise a bearing which co-operates with the static container and a
pump shaft assembly attached to the driven pump member.
Another aspect of the invention provides a sealless coolant
pump comprising a pump body housing a driven pump member
attached to a driven magnetic member and a shaft assembly rotatable
about a rotation axis, a pulley assembly comprising a pulley and
driving magnetic member which co-operates with the driven
magnetic member through a static container attached to the pump
body, wherein the driving magnetic member and driven magnetic
member are substantially radially aligned with respect to the rotation
axis but the pulley is axially displaced therefrom, the pulley assembly
comprising a bearing which co-operates with the pump shaft
assembly and wherein the static container encloses the whole of the
shaft assembly and the driven magnetic member. Beneficially the
pulley can be axially outermost from the pump.
A further aspect of the invention relates to sealless coolant
pump comprising a pump impeller such as the pump disclosed in
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WO 99/10655 PCT/GB98I02500
European Patent specification EP-A-0331288 to Concentric Pumps
Limited. The sealless coolant pump comprising a pump body
housing a driven impeller pump member attached to a shaft assembly
' and a driven magnetic member, and a pulley assembly comprising a
driving magnetic member for co-operating with the driven magnetic
member through a static container attached to the pump body, the
pump further comprising a radially inward fluid inlet region and
radially outward fluid outlet, an axial or thrust, bearing for
cu-operatin; with the shaft assembly, and a duct for communicating
fluid rrom the outlet region to a position proximal the thrust bearing.
Embodiments of the invention will now be described, by way ,
of example only, with reference to the accompanying drawings, in
which:-
FIGURE 1 is a schematic sectional side elevation view of a
pump according to the invention:
FIGURE 2 is a schematic sectional side elevation'view of a
second embodiment of a pump according to the invention;
FIGURE 3 is a schematic sectional side elevation view of a
third embodiment of a pump according to the invention; and
FIGURE 4 is a sectional side elevation view of a fourth
embodiment of a pump according to the invention.
..
Referring to Figure 1 there is shown a pump 10 according to
the invention comprising a pump body 12 and pulley assembly 14.
The pulley assembly and pump body are separated by a static
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container 16 which hermetically seals the pump body to prevent loss
or leakage of fluid in this region. The container 16 is attached to
body 12 by bolts which clamp an annular ring against the container
16 and body 12.
Pulley assembly 14 comprises a pulley or pulley ring 18 which
in use is engaged by a belt B which drives the pulley. The assembly
further comprises an annular flange 20 which provides an annular
bore radially inward of the pulley 18. Flange 20 carries a driving
magnetic member 22 which can consist of an annular series of spaced
bar magnets. The pulley bore engages a bearing 24 for example of
the double row angular contact ball bearing type. A spacer 25 can be
used to position pulley assembly 14 with respect to container 16 and
pump body 12.
The pump body 12 houses a driven member 26 comprising
impeller blades 28. The driven member carries a driven magnetic
member 30 which also can comprise an annular series of spaced bar
magnets. Preferably, there is a 50% overlap between the bar magnets
of the driven and driving magnetic members. The driven magnetic
member 30 is carried on an axial extension 32 which can comprise a
series of radial apertures to enable fluid communication around the
pump body for lubrication purposes. The driven member 26 is
attached to a shaft assembly 34 which comprises a hollow shaft 35
having first and second journal ends 36 and 38. First journal end 36 ,
is journalled in a bearing 40 which abuts an axial spacer 42. Second
journal end 38 is journalled in a bearing 44 which together with
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journal end 38 abuts an axial bearing 46 which acts as a thrust
bearing for hollow shaft 35. The pump body I2 also defines a fluid
inlet region 38 and fluid outlet region 50.
In use, belt B drives pulley assembly 14 about rotational axis
A which causes the driving magnetic member 22 also to rotate and
transfer kinetic energy to driven pump member 26 due to magnetic
coupling with driven magnetic member 30. This causes rotation of
blades 28 which drive fluid from inlet region 48 to outlet region 50
thereby providing a pressure differential between these regions.
Fluid passes from the pump 10 through an outlet (not shown) for
example for communication with an internal combustion engine.
Fluid can be supplied to an inlet (not shown) from a radiator within a
vehicle having such an internal combustion engine.
Beneficially, pump 10 has a reduced axial extent compared to
known sealless coolant pumps, due to the positioning of the pulley
substantially radially in line with magnetic members 2~2 and 30.
Beneficially also, bearing 24 provides a dynamically stable system
since it compresses container 16 on to bearing 40. Preferably bearing
40 can comprise a ceramic material such as silicon carbide which is
strong in compression.
In another form, driven magnetic member 30 can comprise an
induced magnetic drive coupling comprising a ring of axially placed
copper rods suitably embedded in an appropriate matrix.
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Referring to Figure 2 there is shown a pump 110 according to
the invention wherein components which are in common with those
shown in Figure 1 are given the same two digits reference number
prefixed with the number 1. In this embodiment, a static hermetic
seal is provided by container 116 which can for example be made of
a non-magnetic stainless steel. The container comprises a series of
folded regions as shown in Figure i . However, in this embodiment
the driving magnetic member 122 is radially outside the driven
magnetic member 130 with respect to the rotation axis A. Bearing
I24 is carried on the outside radial face of angular flange 120 for
co-operating with housing I 16 and extension 132.
Referring to Figure 3 there is shown a third embodiment of a
pump 210 according to the invention. In this embodiment
components in common with the earlier two embodiments are given
the same two digit reference number prefixed with the number 2. In
this embodiment pulley 218 comprises an annular flange 220 at
approximately the same radial position with respect to axis A and
therefore axially displaced with respect to pulley 218. Radially
inward of pulley 218 is bearing 224 which co-operates with housing
216 and bearings proximal a first journal end 236 of shaft assembly
234. Axially displaced from pulley 218 is magnetic driving member
222 which co-operates with driven magnetic member 230 carried on
extension 232 attached to shaft assembly 234.
Beneficially housing 216 encloses the moving driven parts of
the pump and in this embodiment shaft 234 protrudes beyond the
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co-operating magnetic members to enable pulley 218 to engage
housing 216 and effectively shaft 235 via a series of bearings thereby
providing a dynamically stable pump in which significant radial
' forces are applied to pulley 218 by belt B. Also, a diametrically
compact pump is provided which can use a smaller pulley than other
embodiments.
In a further embodiment of the invention, a pump 310
comprises many features in common with those shown in Figure 1 in
relation to pump 10. Components in common with pump 10 are
Qiven the same two digit reference numbers prefixed with the number
3.
In this embodiment pump 310 further comprises a duct 352
which passes through pump body 312 between the outlet region 350
and a position proximal the thrust bearing 346. Body 312 also
comprises an end plate 354 which locates thrust bearing 346 at the
end of shaft 335. The duct 352 can comprise a bore in body 312 as
well as a tube passing away from and back to plate 354.' Also, shaft
335 can comprise a central bore 356 which only passes from end 336
to a point beyond driven -mernb~er 326 where a cross bore 358
communicates the lubricating medium with region 348. Beneficially,
the lubricant supplied to the thrust bearing 346 is therefore derived
from duct 352. Beneficially therefore fluid is drawn from the
' relatively high pressure region of outlet region 350 to a relatively low
. pressure region proximal the assembly shaft 334 thereby to lubricate
the contact between journal end 238 and thrust bearing 346.
