Improvements in Centrifugal Fans and Pumps
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
"Improvements in Centrifugal Fans and Pumps".
I, Samuel ClelaND DAVIDSON of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention to be as follows:-
My invention has reference to the class or type of rotary fans and pumps in
which the fluid operated on is drawn in centrally and discharged centrifugally.
The object of my improvements is to increase the efficiency of the above-referred
to class or type of rotary fans and pumps in regard to both volume and pressure of
the fluid drawn into and discharged therefrom.
In the Specification of previous Letters Patent granted to me, and dated 12th.
December 1894 No. 24,510 (hereinafter referred to as my previous Specification),
and more particularly to the modification shown in Figure 7 thereof, I described
and showed blades constructed so as to combine a screw-like intake of the air with
radial or centrifugal discharge therefrom mounted upon a disc, with a short
cylindrical tube or ring attached to and enclosing the outer edges of their opposite
ends froin said disc, and which are employed in conjunction with an intake opening
or eye to the fan of approximately equal diameter with that of the periphery of
the fan itself.
In the practical working of said fan, I have however since ascertained that in
regard to both volume and pressure of fluid drawn into and discharged therefrom
the results, although greater than had been obtained with centrifugal fans of
previously ordinary construction, of equal diameter and revolving at same speed,
were nevertheless considerably short of what could be obtained by an improved
construction and arrangement of the blades therein, and accordingly my herein-
after described invention has reference more particularly to the construction and
arrangement of the blades therein, conjointly with the employment of an intake
opening or eye thereto of approximately equal diameter to that of the circumference
of the discharge edges of the blades, or as near to this diameter as can be obtained
in practice, having regard to the strength of the blades and necessary parts and
thickness of material employed; and when my improved rotary fans or pumps
are constructed as hereinafter described, the fluid acted on is drawn in thereto in
inuch greater volume and discharged therefrom with a much improved velocity
or pressure, relatively to the diameter and peripheral speed of revolution, than
when constructed as described in my previous Specification, and still more so
than in centrifugal fans or pumps as hitherto ordinarily made.
In my improved fans or pumps, the diameter of the intake opening or eye
thereto is equal or nearly equal to that of the periphery of the fan or pump. The
width of the vanes which I employ, measured from the periphery of the fan or
1

page_text: pump inwards, that is to say, the radial dimension is as narrow as practicable
consistent with strength of construction and preferably not greater than about one-
eighth of the diameter of the fan or pump, and the number of these blades is
inuch larger than has hitherto been usual, as the width of the space which I
preferably adopt between the blades is equal to about one half to two-thirds of
their radial width which arrangement in combination with narrow blades con-
structed as a plane gives an area of passage way for the fluid through the ports
between saine which is only very slightly greater at the discharge end than at the
intake end, while with curved or angled blades the discharge end can be so con-
structed as to be less, to any required extent, than the intake end.
Hereinafter the word "disc" is understood to mean that portion of my improved
fans or pumps which is mounted on the revolving shaft, and to which the vanes
are attached, and whether said disc be flat, conical, or concavely conical towards
the entering fluid; or it may consist of radial arms suitably, mounted on the
revolving shaft, with a flat annulus mounted on their outer ends. The word
"blades is employed to indicate the vanes or blades which impel the fluid, and
which are attached to the disc. The length of the blade is the distance from the
face of the disc to the point of the blades furthest away therefrom; the width of
the blades is their measurement taken radially; the intake end of the blades,
that which is furthest away from the disc and towards the approaching fluid;
and the "ports" the intervening spaces between the blades.
My improved fan is constructed with the disc mounted on a spindle revolving
in suitable bearings, and to said disc the blades are so attached that they
overhang therefrom at right angles thereto, and at their opposite ends from the
disc, they are connected by a short cylindrical tube or ring (hereinafter referred
to as the ring) to the inner face of which their outer edges are firmly attached,
and consequently the internal diameter of said ring is the same or approximately
the same as that of the peripheral circumference of the outer edges or tips of the
blades, said ring being only extended inward over the face of the intake ends
of the blades, so far as may be necessary to give them any requisite strength
and rigidity.
The blades may each be formed either as a plane or as two or more planes
at an angle to one another or as a curved section through a plane at right
angles to the axis of the fan or pump.
I usually space the blades apart so that the width of the ports between the
blades is about one-half to two-thirds of their own width and I make the
length of the ports, measured from the front of the disc to the nearest edge
of the ring such that the aggregate open area of said ports around the periphery
of the fan shall be equal or about equal to the area of the eye. When angles
or curved blades are employed I preferably arrange them so that the angular
width of the ports between the blades at their intake or inner ends is greater
than the angular width of the ports at their outer or delivery ends. I mount
the blades between the disc and the ring so that they are at right angles to
the plane of revolution. The blades may be mounted either radially or at a
slight angle to radial lines, and when angles or curved blades are employed
the inside of the angle or the concave face of each angle or curve should be
in the direction of revolution.
My improved fans or pumps when constructed as above described, may be
employed with any fluids, whether gaseous or liquid, as for instance with air or
water.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London.
Chartered Patent Agents.

page_text: Improvements in Centrifugal Fans and Pumps".
I, SAMUEL CLELAND DAVIDSON of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by tho
following statement:-
My invention has reference to that class of centrifugal fans and pumps in which
the fluid operated on is taken in axially and discharged circumferentially.
It has hitherto been usual to construct fans and pumps acting as above (herein-
after referred to as fans) in such a manner that the supply or intake opening to the
blades thereof (hereinafter referred to as the eye) is of considerably less diameter
than that of the periphery of the fan, and to so limit the axial length of the dis-
charging edges of the blades that the area of discharge from the ports or passages
between same shall not be greater around the periphery of the fan than the area
of the relatively smaller eye employed therewith, whereby for a given discharge of
fluid at a given velocity the diameter of said fans must necessarily be equivalently
greater than if their construction were such as to operate efficiently with an eye of
equal or nearly equal diameter to that of the periphery of the fan itself, and accord-
ingly the objects, amongst others, of my invention are to so construct fans of the
aforesaid type, and more especially the blades employed. therein that they will work
efficiently in conjunction with an eye of equal diameter to or only slightly less diameter
than that of the periphery of the fan and whereby the voluine of fluid which they
will propel through them for a given diameter and speed of revolution is equiva-
lently increased without loss of velocity in the flow of the fluid, as compared with
said type of fans as hitherto constructed, while in certain constructions of my im-
proved fan the velocity of flow is also increased.
In fans of the aforesaid type as hitherto constructed, the centre of the blades
(which for the purpose of this Specification, I assume to be half way between their
inner and outer edges or tips) rotates in a circle of greater diameter than that of the
eye, except in fans constructed as described in the Specification of iny British
Patent No. 24,510 of 1894 (hereinafter referred to as my previous Specification)
one part of which Specification describes a fan as shown in Figure 7 of the drawings
accompanying same, wherein the centre of the blades rotates in a circle of less
diameter than that of the eye, which is in effect the full diameter of the revolving
portion of the fan, and in which the tips of the blades are enclosed and connected
by a ring or annulus from which they extend inwards to near the centre of the
revolving disc.
I have however since found by practical experience in the working of said fans
with the eye of approximately equal diameter to that of the fan periphery, that
improved results are obtained by the employment of blades which only extend from
the periphery of the fan inwards to a radial depth of preferably not inore than of
the diameter of the fan, (the construction, mounting and arrangement of said blades
in the fan being hereinafter more particularly described), as the relative velocity
of rotation of the centre of said blades, and consequently also the velocity at which
the fluid is discharged therefrom, is greater for a given speed of revolution of
the fans than is the case in fans employing blades of greater radial measurement;
and I have further found that if the eye of the fan be reduced to less than 4/5ths
of the diameter of the outer periphery of the fan, the conditions under which said
blades operate become so altered that the efficiency of the fan is reduced. In
short, the more nearly the diameter of the eye approximates to the full diameter
of the fan, and the narrower the radial measurement of the blades consistent with
strength and facility of construction, and provided that the width of the ports between
said blades be not greater than their radial measurement, the better are the results
obtained.

page_text: In fans as hitherto ordinarily constructed the diamet of the eye is usually about
or very slightly more than, one half the diameter of the fan, and the intermediate
spaces or ports between the blades are usually made greater in area opposite the
circumference of said eye than at the outer edges or tips of the blades, and which
construction has hitherto been effected mainly by making the axial measurement
of the inner edges of the blades greater than that of their outer edges or tips and by.
enclosing or encasing the sides of the blades from their inner to their outer edges in
order to confine the fluid in the ports between them.
Now in my herein described improved fans the axial measurement of the inner
and outer edges of the blades are substantially equal, and when I construct said fans
with curved or angled blades as hereinafter described and require the area of the
outer or discharge openings of the ports between the blades to be less than that
of their inner or intake openings. I so far tilt the outer edges of said blades forward
relatively to their inner edges in the direction of rotation as to reduce the area
of the discharge openings from the ports to any required proportion and leave the
intake ends of the ports between the blades and towards the entering fluid, either
open thereto or only so far closed that the diameter of the eye is not thereby
reduced to less than 4/5ths of that of the circumference of the outer edges of the
blades.
For the purpose of this specification, the word "disc" is understood to mean a
disc, or its equivalent, mounted upon the fan shaft and to which the blades are
attached. The word "blades" is employed to indicate the vanes or blades which
impart motion to the fluid; the "intake end" of the blades that which is furthest
away from the disc and towards the approaching fluid; the "length" of the blades
their measurement from the disc to their intake ends, the "depth" of the blades
their measurement from inner to outer edge, taken radially, and the "ports" the
intervening spaces between the blades.
My improved fan or pump is constructed as follows:-The disc is mounted upon
a spindle revolving in any suitable bearings and the blades are so attached to one
or both sides of the disc that they project therefrom substantially parallel to the
axis, with their intake ends preferably open towards the inflowing fluid, and their
outer edges connected together by projecting lips or flanges from each blade to
the next adjoining, or by an encircling ring or annulus to which they are attached,
and which may be extended inwards over the faces of the intake ends so far as
may be necessary for strength and rigidity of construction consistent with the eye
not being reduced thereby to less diameter than 4/5ths of that of the periphery of the
fan, as any further reduction of its diameter increases the resistance of the inflow
cf a given volume of the fluid and materially diminishes the efficiency of this
construction of fan.
The blades are preferably of sheet metal, and are of considerably greater axial
length than radial depth, and said depth being preferably as shallow as
practicable consistent with strength of construction, and not greater than about
one-eighth of the diameter of the fan, and their inner and outer edges are substan-
tially parallel to each other and to the axis, except when, for increased strength
the inner edges may be sloped inwards towards the disc, to provide a broader flange
for their attachment thereto. Said blades may be formed with a plane surface, or
with two or more planes at an angle to each other, or with a curved section through
a plane at right angles to the axis of the fan mounted with the concave of said
curve in the same direction as that of rotation; and the intake ends of the curved
or angled blades are preferably shaped like the end of a spoon, with the concavity
of said spoon shaped end in the direction of rotation, and in blades with plane
surface the intake ends are preferably tilted slightly forward from the axial line of
the main body of the blade in the direction of rotation.
I usually so space the blades apart from one another, that the width of the ports
between the blades is about two-thirds or it may be as much as the full depth of
said blades and I make the length of the ports measured parellel to the axis such
that the aggregate open area of said ports around the periphery of the fan shall be

page_text: about equal to the area of the eye, when the maximum volume of intake and
discharge is required, but the length of the blades may be made shorter to suit any
special requirements.
When I employ angled or curved blades, I preferably mount them so that
while their concave faces are in the direction of rotation, their outer edges are so
far tilted forward that they have a lead relatively to their inner edges, in the direction
of rotation, and that the clear width of the ports between the blades at their outer
edges, is narrower, and consequently less in area, than at their inner edges, so that
notwithstanding the slower speed at which the inner edges of the blades revolve,
relatively to their outer edges, the volume of fluid drawn into the ports at their
inner openings is sufficiently greater than that being discharged from their outer
openings, that the fluid within the ports is under a pressure from within outwards,
against the contracted width of the outer opening, whereby the effective operation
of the fan is improved.
My improved fans or pumps when constructed as herein-before described may
be employed with any fluids, either gaseous or liquid, as for instance with air or
water.
:-
In the accompanying drawings :-
Figure 1 is a sectional elevation on the line 1-1 of Figure 2 of a fan or pump
constructed in accordance with the present invention with curved blades, the
radial depth of the blades being 1/12th of the diameter of the fan or pump, the
intake opening or eye thereto being of equal diameter to that of the circumference
of the outer edges of the blade.
Figure 2 is a cross sectional elevation of the fan or pump, shown in Figure 1.
Figure 3 is a detail view on a larger scale showing a inethod of attaching the
curved blades of Figures 1 and 2 to the disc.
Figure 4 is a detail view showing a method of attaching the outer edges of the
intake ends of the blades to the connecting ring.
Figure 5 is a detail view showing a method of attaching the outer edges of the
intake ends of the blades to each other by means of projecting lips or flanges
which extend from each blade to that next adjoining.
Figure 6 is a view on a still larger scale of a curved blade the intake end of
which is spoon shaped and which has also a projecting lip or flange for attaching
it to the blade next adjoining.
Figures 7, 8, 9, 10 and 11 are detail views illustrating a curved blade with spoon
shaped intake end with a projecting lip or flange for attaching it to the ring which
spoon end construction materially increases the strength of the blade and of the
fan.
Figure 12 is a sectional elevation of the lower half of my improved fan or pump
with blades formed as two planes at an angle to each other.
Figure 12 is a sectional elevation of the upper half of my improved fan or
pump with blades formed as three planes at an angle to each other.
Figure 13 is a sectional elevation of my improved fan or pump with blades
formed as one plane surface.
Figure 14 is a sectional elevation of my improved fan or pump with curved
blades, the radial depth of the blades being one-eighth of the diameter of the fan
or pump.
Figures 15, 16 and 17 are detail views on a larger scale of a blade formed as
two planes as in Figure 12.
Figures 18, 19 and 20 are similar views of a blade formed as three planes as in
Figure 12.
Figures 21, 22 and 23 are similar views of a curved blade as in Figure 14 with
spoon shaped ends.
Figures 24, 25 and 26 are similar views of a blade formed as one plane surface
as in Figure 13 with the intake end tilted forward in the direction of rotation for
the same reason as above described in respect of Figures 7 to 11.

page_text: Figures 27, 28, 29 and 30 illustrate portions of a fan or pump in which the
intake ends of the blades are enclosed by the encircling ring or annulus d for
strength of construction when the fan or pump has to be driven at a very high
velocity or when the fluid dealt with is of a specific gravity such as that of water,
while still leaving the diameter of the inlet opening or eye thereto not less than
4/5ths of that of the circumference of the outer edges of the blades. In the
modification shown in Figures 27 and 28 the intake ends of the blades are closed
by projecting the flange of the connecting ring inwards. In the modification
shown in Figures 29 and 30 the intake ends of the blades are closed by a flat
connecting ring to which they are attached in the same manner as they are
attached to the disc b at their opposite ends.
Referring to the drawings
a is the casing in which the revolving portion of the fan or pump is enclosed.
b is the disc to which the blades are attached. cc are the blades which are
attached at one end to said disc b. is the ring which connects the intake ends
of the blades cc together. ee are the ports or intervening spaces between the
blades. is the revolving shaft or spindle on which the disc 6 carrying the
blades c c is mounted. is the discharging mouth piece. is the eye through
which the supply of fluid is drawn. c c are flanges of the blades c c by which
they are rivetted or attached to the disc b and ji are holes in said flanges c¹ c¹ to
give passage to the rivets or attaching devices. c2 c² are flanges at the intake ends
of the blades by which they are rivetted or attached to the disc d in the modifica-
tion shown in Figure 4, or rivetted or attached to each other as in the modification
shown in Figure 5, and are holes in said flanges c² c² to give passage to said
rivets or attaching devices. is the tilted forward or spoon shaped portion of
the intake ends of the blades c c. On reference to Figure 3 it will be noticed that
the width of the ports e c at a near the outer edges of the blades is somewhat less
than that at y their inner edges owing to said outer edges of the blades being
tilted slightly forward relatively to the radial line (Figure 3) and to their inner
edges.
It is obvious that in the fan or pump shown in Figures 1 and 2 and also in those
shown respectively in Figures 12, 12, 13 and 14 the casing may project inwards
over the edges of the blades c c but the inlet opening or eye to the fan must not be
thereby reduced to less than 4/5ths of the diameter of the fan for the reasons
already hereinbefore stated.
In all the inodifications shown in the accompanying drawings the fan is
within a casing. It will however be readily understood that a casing is not
necessary in all instances; as for example when the inflowing fluid is led to
the eye of the fan by a pipe, or when the fan projects through an orifice in a
wall so as to revolve say outside a house with the eye of the fan communi-
cating through said orifice with the inside of the house and facing the bearings
in which the spindle revolves; in which case the fan would then draw the air
through that orifice and discharge it freely all round into the open air.
I do not limit myself to constructing the blades of sheet metal as in the case of
said fans being employed as water pumps, wherein extra strength of construction
is essential I may cast the blades, disc and ring all as one integral part or in
sections.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that I make
no claim to any arrangement in which the length of the blades arially is not
considerably greater than their depth radially, and that my claims are to be read
subject to this note, but what I claim is :-
1. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades of a
length from the disc to their intake ends of at least twice their depth having their

page_text: inner and outer edges substantially parallel with the axis of the, fan or pump, said
blades being mounted on a disc and projecting therefrom, the ends of the inter-
mediate spaces or ports between said blades and towards the entering fluid being
open to admit said inflowing fluid from the intake opening or eye to said blades,
said intake opening or eye being of equal diameter to or not less diameter
than 4/5ths of that of the circumference of their outer edges, all substantially as
set forth.
2. In centrifugal fans and pumps wherein the fluid. operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed and arranged as referred to in Claim I in combination with means
connecting their intake ends together, and an inlet opening or eye to said blades
of equal diameter to, or not less dia.neter than 4/5ths of that of the circum-
ference of their outer edges, all substantially as set forth.
3. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed, arranged and mounted as referred to in Claim 1 or in Claim 2, and of
a depth not greater than about one-eighth of the diameter of said fan or pump,
and-of-a-length-from-the-dise-to-their-intake-ends-of-at-least-twice-their-depth, and
mounted at a pitch or distance apart at their inner edges of not greater than the
measurement of their depth radially, in combination with an intake opening or eye
to said blades of equal diameter to or not less diameter than 4/5ths of that of the
circumference of their outer edges, all substantially as set forth.
4. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed, arranged and mounted as referred to in Claim 1, or Claim 2, or
Claim 3, and formed approximately as a curve through a plane at right angles
to the axis in combination with an intake opening or oye to said blades of
equal diameter to or not less diameter than 4/5ths of that of the circumference
of their outer edges, all substantially as set forth (Figures 1, 2, 14).
5. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed, arranged and mounted as referred to in Claim 1 or Claim 2 or
Claim 3, and formed as a plane surface, in combination with an intake opening or
eye to said blades of equal diameter to or not less diameter than 4/5ths of that of
the circumference of their outer edges, all substantially as set forth (Figures 13, 24,
25, 26).
6. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed, arranged and mounted as referred to in Claim 1 or 2 or 3, and formed
as two plane surfaces at an angle to each other (Figures 12, 15, 16, 17) or as three
plane surfaces at an angle to each other (Figures 12, 18, 19, 20), in combination
with an intake opening or eye to said blades of equal diameter to or not less
diameter than 4/5ths of that of the circumference of their outer edges, substantially
as set forth.
7. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
as referred to in Clain 4 and with the intake ends of said blades shaped like
the end of a spoon with its concave in the direction of rotation, in combination
with an intake opening or eye to said blades of equal diameter to or not less
diameter than 4/5ths of that of the circumference of their outer edges, all
substantially as set forth (Figures 6 to 11 and Figures 21, 22, 23).
8. In centrifugal fans and pumps wherein the fluid operated on is admitted
axially and discharged circumferentially, the employment of a series of blades
constructed, arranged and mounted as referred to in Claims 1 or 2 or 3 or 4 or 6
or 7 and with the said blades placed in said fans or pumps with their outer edges
relative to their inner edges having a forward angle or lead thereto in the direction
of rotation, whereby the outer or discharging area of the ports is less than their

page_text: interior or inlet area, in combination with an intake opening or eye to said blades
of equal diameter to or not less diameter than 4/5ths of that of the circuinference
of their outer edges, all substantially as set forth (Figure 3).
9. The several general arrangements and combinations of parts constituting
improved centrifugal fans or pumps, substantially as hereinbefore described and
represented in the accompanying drawings.