[0001] The present invention relates to an improved kind of centrifugal turbine pump, preferably
of the type generally used in connection with electrical home appliances, such as
clothes washing machines, dishwashers, and the like, and provided therefore with such
design and operating specifications as generally required in view of such applications.
In particular, the present invention relates to the pumping chamber and the rotating
vanes of the impeller of such pumps.
[0002] Since pumps of the above-cited kind are generally used in appliances and machines
that are required to be very competitive as far as both costs and energy efficiency
are concerned, a considerable, constant effort is most obviously being made in industry
by manufacturing and design engineers in an attempt to continuously improve the overall
operating and construction characteristics of such pumps.
[0003] The efforts of manufacturing and design engineers are in particular focussing on
the possibility of providing impellers and pumping chambers that are effective in
bringing in sensible improvements in the overall efficiency, so as to achieve a natural
reduction in the size and the power rating of the motor used to drive said impeller.
[0004] What is obtained in this way, actually, is therefore a twofold advantage in terms
of an improved water-handling, i.e. hydraulic efficiency and a resulting reduction
in the size - and therefore the costs - of the motor used to drive the pump.
[0006] In both such publications, there can be noticed that the gap between the body of
the pumping chamber - on the side of the intake conduit - and the corresponding edges
of the vanes has a rather considerable width, so that a vortex is able to form thereinside,
which does not take part in, i.e. contribute to the pumping action, but uses anyway
energy and, therefore, contributes to a deterioration of the overall efficiency of
the pump; in addition, the presence of the core part of the pump, which is provided
to act as a hub, and which is however situated exactly in front of the outflow port
of the intake conduit, turns out as acting almost as a "plug" that partially obstructs
the inflow of the liquor into the pumping chamber.
[0007] No practical solutions are currently known to effectively counter the second one
of the above-noted drawbacks, since the presence of vanes having as great a height
as possible obviously implies that even the core portion, i.e. the hub thereof cannot
but be situated in a position that at best comes close to be in front of the inflow
port of the intake conduit.
[0008] As far as the first one of the above-cited drawbacks is concerned, no possibility
is given for the width of said gap to be reduced beyond a certain limit, since the
construction and the assembly of the pumping chamber are done and carried out using
substantially industrial technologies and, therefore, under standard tolerances that
cannot be reduced beyond a certain extent, either, owing basically to the shrinkage
effect of moulded plastics, i.e. the material which both the impeller and the pumping
chamber are generally made of.
[0009] It would therefore be desirable, and it is the main object of the present invention,
actually, to provide a kind of centrifugal water turbine pump that is effective in
doing away with the two above-indicated drawbacks of prior-art pumps of the same kind,
so as to ensure a high water-handling, i.e. hydraulic efficiency jointly with a pumping
chamber having a reduced size.
[0010] Within this general object, it is a purpose of the present invention to provide a
pump of the above-indicated kind, which is capable of being manufactured using readily
available techniques and machinery at fully competitive costs.
[0011] According to the present invention, these aims are reached in a centrifugal turbine
pump incorporating the features as defined and recited in the appended claims.
[0012] Features and advantages of the present invention will anyway be more readily understood
from the description that is given below by way of non-limiting example with reference
to the accompanying drawings, in which:
- Figure 1 is a median cross-sectional view through the axis of rotation of the impeller,
the pumping chamber and the intake conduit of a pump according to the present invention
in a first embodiment thereof;
- Figure 2 is a planar view of the image of a rotating vane when figuratively lying
on a plane passing through the axis of rotation of the impeller;
- Figure 3 is a median cross-sectional view through the axis of rotation of the impeller,
the pumping chamber and the intake conduit of a pump according to the present invention
in a second embodiment thereof;
- Figure 4 is a median cross-sectional view through the axis of rotation of the impeller,
the pumping chamber and the intake conduit of a pump according to the present invention
in a third embodiment thereof;
- Figure 5 is a diagrammatical view of a graph plotting the trend, i.e. variation of
the hydraulic efficiency of an inventive pump, as compared with the hydraulic efficiency
of a similar prior-art pump, versus the flow rate thereof, when said pump is not provided
with the inventive contrivance (curve R), when the pump is on the contrary provided
with the inventive contrivance according to the first embodiment thereof illustrated
in Figure 1 (curve A), and when the pump is on the contrary provided with the inventive
contrivance according to the second embodiment thereof illustrated in Figure 3 (curve
B).
[0013] With reference to Figure 1, there is illustrated a first embodiment of the invention,
which comprises an intake conduit 1, a pumping chamber 3 and, housed thereinside,
an impeller with related vanes 5.
[0014] The end portion 6 of said intake conduit is not cylindrical, as it usually occurs,
but is slightly flaring upwards, i.e. narrowing conically towards the inflow end into
the pumping chamber, as indicated at 16 in Figure 1. It has in fact been found that
such slight reduction in the inflow section of the conduit into the pumping chamber,
far from producing a reduction in the flow rate, is rather effective in improving
the linearity of the flow lines of the liquor being let into the chamber, since a
contraction in the cross-section of a conduit, through which there flows a fluid,
generally tends to reduce the vorticity of the fluid flow and, as a result, also improves
- albeit slightly - the flow rate.
[0015] Any - albeit limited - flow-rate reduction should be avoided, actually, even in consideration
of further embodiments of the inventive pump that are based on taking advantage in
a particularly effective manner of the above-described reduction in the cross-section
area of the end portion 6 of the intake conduit.
[0016] With reference to Figure 2, which illustrates the contour of a vane 5 of the impeller
lying on a plane passing through the axis X of the same impeller, the edge 10 of such
vane that is disposed to face the zone where said intake conduit 1 couples to, i.e.
flows into the pumping chamber 3, comprises in fact a portion 7 which is shaped so
as to form a corner with an angle A that is substantially oriented in a direction
towards said intake conduit, or preferentially towards the transition region 8 between
said intake conduit and said pumping chamber.
[0017] If the latter is embodied as generally illustrated in Figure 3, i.e. with said transition
region 8 in the form of a continuous curve following a substantially constant curvature
radius, a combination of geometries, i.e. shapes and proportions among the various
parts involved may be provided so that - relative to said angle A - the outer portion
9 of said edge 10 is capable of coming sensibly closer, and for quite appreciable
a length, to the inner contour of said transition region 8.
[0018] It has been experimentally found that such contrivance is really effective in improving
both the hydraulic efficiency and the discharge head of the turbine pump, since any
vorticity that may possibly arise and come into existence between the vanes of said
impeller and said transition region 8 would be minimized, or even eliminated, owing
to the width of the gap existing between said two elements being very small, actually.
The resulting improvement is best emphasized by the graph illustrated in Figure 5,
which shall be discussed further on.
[0019] A further advantageous embodiment of the present invention is illustrated in Figure
4, wherein it can be noticed that the above-mentioned transition region - instead
of being embodied in the form of a continuous curve following a substantially constant
curvature radius - is given an "accordion-like" pleated contour with two opposite
angles, so that the section passing through the axis X of the impeller shows a sawtooth-like
profile, i.e. a profile resembling the teeth of a saw.
[0020] Such transition region has two opposite circular edges 30 and 31 extending concentrically
with said axis X, wherein the edge 30 lying closer to the axis X is also the innermost
edge relative to the pumping chamber and, as a result, the edge that lies also closer
to the body of the respective impeller.
[0021] Therefore, an annular recessing portion 32 is formed between said two edges 30 and
31, which is delimited towards said axis X by the side 33 joining said two edges 30
and 31 with each other.
[0022] Those skilled in the art will be fully capable of appreciating that, although the
present description refers to a three-dimensional construction, actually, use is however
made of terms which are usually employed in connection with planar constructions,
due practically to the sole reason that such is the construction appearing in Figure
4, which in fact refers to the corresponding planar section.
[0023] Going on with the description, now, said corner-shaped portion 7 featuring an angle
A is appropriately sized and proportioned so that, when the impeller is duly assembled,
such portion is able to fit into said annular recessing portion 32 and, preferably,
said angle A is capable of fitting in a wedge-like manner into the innermost region
of said annular recessing portion 32.
[0024] A still further improved embodiment of the present invention may be again be provided
as follows: referring again to Figures 2 and 4, the inner side 11 of said edges 10
of the respective vanes is disposed so as to be substantially oriented towards the
core portion of the impeller, i.e. in a direction inclining at an acute angle H relative
to said axis X; the actual purpose of this improvement lies in the fact that any form
whatsoever of resistance or hindrance to the movement of the inflow of fluid entering
the pumping chamber is thereby effectively prevented from occurring, and therefore,
if the core portion of the vanes is set back to some extent, the vanes themselves
are effectively prevented from simply and just centrifuging the inflowing fluid, i.e.
accelerating it by the sole centrifugal force, before delivering it to the outermost,
i.e. side portions of the vanes for it to be propelled by turbine effect towards the
delivery or discharge conduit.
[0025] It has in fact been found that - with the above-described improvement - the fluid
is immediately transferred to the outermost region of the vanes, thereby saving it
from being first "whirled" in the innermost, core region of the same vanes.
[0026] The improvements that are generally achieved with the present invention can most
readily be inferred from the graphical representation in Figure 5, where the trend,
i.e. variation of the hydraulic efficiency (i.e. energy efficiency) of an inventive
pump is plotted, as compared with the hydraulic efficiency of a similar prior-art
pump, versus the flow rate thereof, when said pump is not provided with the inventive
contrivance (curve R), when the pump is on the contrary provided with the inventive
contrivance according to the first embodiment thereof illustrated in Figure 1 (curve
A), and when the pump is provided with the inventive contrivance according to the
second embodiment thereof illustrated in Figure 3 (curve B).
[0027] In this connection, it should in particular be noticed that an appreciable improvement
in the efficiency of the pump is shown by the curve A to mainly take place - as compared
with the one shown by the curve R - when the pump is operated at rather low-to-medium
flow rates, from approx. 60 to 80 l/min, whereas a most marked efficiency improvement
is mainly obtained between the curve R and the curve B when the pump is operated at
higher flow rates in excess of 80 I/min.
1. Centrifugal turbine pump comprising:
- an intake conduit (1),
- a pumping chamber (3),
- an impeller (4) housed in said pumping chamber,
- a plurality of vanes (5) arranged on and attached to said impeller,
characterized in that said intake conduit joins to said pumping chamber (3) via a flared section (16) narrowing
with a slightly conical configuration along the end portion (6) of said intake conduit
flowing into said pumping chamber.
2. Centrifugal turbine pump according to claim 1, characterized in that the edge (10) of said vanes (5) facing said intake conduit comprises a corner-shaped
portion (7) forming an angle (A).
3. Centrifugal turbine pump according to claim 2, characterized in that the portion of said edge (10) situated outside said angle (A) is provided to tightly
conform to the contour of the transition region (8) from said intake conduit to said
pumping chamber.
4. Centrifugal turbine pump according to claim 1 or 2,
characterized in that:
- said transition region (8) from said intake conduit (1) to said pumping chamber
(3) is given an accordion-like pleated contour with two concentric circular edges
(30, 31) bending in a mutually opposite direction, wherein the innermost circular
edge (30) lies closer to the body of respective impeller than the outermost circular
edge (31).
- said accordion-like pleated transition region (8) forms an annular recess (32) that
is substantially situated between said innermost circular edge (30) and said outermost
circular edge (31).
5. Centrifugal turbine pump according to claim 4, characterized in that said portion (7) shaped into a corner-like configuration (A) of said edges (10) projects
into said annular recess (32).
6. Centrifugal turbine pump according to any of the claims 2 to 5, characterized in that the inward side (11) of said portion (7) shaped into a corner-like configuration
(A) of said vanes converges towards the core portion (20) of the impeller or, anyway,
forms an acute angle (H) relative to the axis (X) oriented towards said intake conduit.