Note: Descriptions are shown in the official language in which they were submitted.
M. Erikson-l
1146~UD9 (Revision)
IMPROVED IMPELLER
BACKGROUND OF THE INVENTION
This invention is directed to an impeller for
centrifugal pumps particularly for use in pumping of
fluent media. More precisely, the invention is directed
to an impeller of the so called single vane type, which
means that the impeller is provided with one single vane
which goes helically around the impeller either partly
or entirely and perhaps more than once around the im-
peller. The channel which is formed by the vane in the
surrounding pump housing is axially limited by cover
discs which are parts of the impeller.
Pump impellers of the type referred to are primarily
; used for pumping liquids containing solid bodies, for
instance, sewerage water. The advantage of this config-
uration i8 that the risk of clogging decreases if only
one vane is used. In some instances, a certain minimum
thrulet in a pump impeller for sewerage pumps is pre-
scribed by Governmental regulation. Such thrulet can
only be fulfilled by a single vane impeller if reason-
able dimensions are to be maintained.
Previously known impellers of the single vane typehave the vane formed with constant thickness from the
leading edge near the pump inlet to the trailing edge
near the pump outlet. One such impeller of this type
is shown in the Swedish published patent application
number 7,806,198-3.
-2- M Erikson-l
Such impellers have certain disadvantages. As the
vane thickness is constant, the channel which is formed
by the vane has a constantly increasing cross-section
towards the direction of the pump outlet. This steady
increase is most pronounced near the inlet. This
rapid increase in cross-sectional area results in a
rapid decrease in fluid velocity and local pressure
which may cause an undesirable turbulence and possible
cavitation. Additionally, an increased risk of solid
body collection exists especially at the leading edge
of the vane which would result in a decreased cross-
sectional area at that location causing increased
probability of clogging and/or decreased pump efficiency.
Any clogging of the impeller results in an increased
load on the driving unit, which sometimes triggers the
overload protection devices resulting in work stoppage
and requiring servicing of the pump.
OBJECTS OF THE INVENTION
It is an object of this invention to obtain an
impeller of the single channel type where the speed
reduction of the fluid flow is avoided as much as possi-
ble.
Another object of the invention is to achieve
elimination of fluid diffusion in the area near the
impeller.
SUMMARY OF THE INVENTION
This i8 achieved according to the invention in
that an impeller for use in a centrifugal pump comprises
cover discs connected to each other by a single vane in
that the discs and the vane define a channel having an
inlet coaxial with the impeller axis of rotation and an
outlet eccentric to this axis, and in that the thickness
of the vane varies in the direction of flow such that
the cross section of the channel taken normal to the
axis of flow through the channel is at most only slightly
increasing.
- 11468~9 M. Erikson-l
3 (Revision)
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described more specifically here-
inafter with reference to the enclosed drawings wherein:
Fig. 1 shows an axial section through an impeller,
according to the invention.
Fig. 2 shows a radial section; and
Fig. 3 shows a perspective view of the impeller.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the drawings, 1 designates the impeller vane
having a leading edge (inlet) 2 and a trailing edge
(outlet) 3, 4 designates the channel formed by the vane 1
and the cover discs 5, and 6 designates a hole through
which the impeller shaft extends.
Unlike previously known impellers of the single
vane type, an impeller according to the present invention
has a vane 1 with varying thickness in the direction of
flow. Ihis means that, as previously mentioned, the
channel 4, which is formed by the vane 1 and the cover
discs 5, has a cross-section which is only slightly in-
creasing in the direction of the outlet, thus reducingthe aforementioned risks of clogging.
Known impellers of the single channel type often
get a layer of p~rticles accumulating near the leading
edge 2. This layer often gives the vane a new profile
which is undesirable because of the increased clogging
tendency, resulting in the risk of overload. In addi-
tion to the overload risk, such deposits often result in
unbalancing of the impeller resulting in increased strain
and wear on the bearings resulting in shorter life span.
According to the invention, 8 proper profile is formed
initially in the valve with the result that no deposits
form on the impeller resulting in potential c~ogging or
rapid deterioration of the pump.
In a preferred embodiment of the invention, the
vane is hollow in order to diminish its weight and thus
the need for careful balancing of the pump parts.
~ .!
` ~146809 M Erikson-l
--4--
The vane 1, may be formed differently according to
the optimal design conditions of the pump. Different
conditions may be required where the pump medium, impeller
speed, volume of flow and fluid head are varied. Depend-
ing on these criteria, the impeller is formed with a moreor less pronounced bulbform near the leading edge of
the vane 1 and with double or single bent sides. A
common feature for all embodiments are the different
thicknesses of various portions of the vane. In a pre-
ferred embodiment, the vane 1 has a bulb form having itsgreatest thickness located at a portion of the vane 1
between 20 to 40 displaced from the front edge 2 of
the vane 1.
According to this invention, an impeller may be
designed which has a radically diminished risk of clogging,
and increased liquid thruput, having better flow efficiency
and a better balancing of the impeller without abandoning
the minimum free thrulet.
