Improvements in Centrifugal Fans or Pumps.
Year: 1899

page_text: Improvements in Centrifugal Fans or Pumps.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ire-
land, Merchant, do hereby declare the nature of this invention to be as follows:-
This invention has reference to the type of centrifugal fans or pumps (herein-
after referred to as fans) in which air, gases, vapour or liquid (such for instance
as air or water, and which are hereinafter referred to as the fluid) is drawn in
axially and discharged circumferentially, and wherein the intake opening through
which the fluid enters the fan (hereinafter called the eye) is of not less diameter
than ths of that of the outer tips of the blades, but preferably of equal
diameter thereto.
My improvements relate more particularly to the form and construction of the
blades employed therein, and one of the chief objects thereof is to increase the
operative efficiency of the fan more especially in regard to its capability to
either exhaust or propel the fluid dealt with against resistances or back pressures
(which are usually indicated by the extent to which a column of water or other
liquid is raised by the operation of the fan, and which are hereinafter referred
to as the water gauge indications), so that a larger volume of the fluid operated on
shall be drawn into the fan and discharged therefrom, and without return
eddies or back flow currents taking place from the tips of the blades inwards,
or eddies within the fluid passages between the blades, and at higher water
gauge indications relatively to the diameter of the fan and its speed of revolution
than in fans as hitherto constructed.
My invention is hereinafter described as applied to the construction of fans
described and represented in the Specification of previous Letters Patent granted
to me No. 4609 of 1898 (hereinafter referred to as my previous specification) in
which the combination is employed of an eye of equal or not less diameter than.
ths of that of the fan, with blades of considerably greater axial length than
radial depth, which depth is preferably as narrow as practicable consistent with
strength of construction of the fan itself, and with the intermediate space or
passage-way for the fluid between the blades of a not greater circumferential
width than the radial depth of the blades, which are mounted on the fan at right
angles to its plane of revolution, by attachment at one end to a disc mounted on
a central boss on the fan spindle, and at the other end to an encircling ring or
annulus; and in my hereinafter described improved fan I additionally connect
said encircling ring to the axially projecting end of the central boss of the
fan disc by centrally projecting stay rods acting under tensile strain
whereby not only are said encircling ring and the ends of the blades to
which it is connected, held securely against the bursting strain due to centri-
fugal force thereon when the fan is revolving at high velocities, but by suitable
adjustment of the degree of tension to which each stay rod is screwed up, said
encircling ring can be drawn into a truly revolving circle.

page_text: .
Tans of the construction described in my previous specification, have hitherto
been fitted with blades, formed either as planes approximately radial and axia
to the fan, or so curved or angled through an axially radial plane that one face
thereof is concave and the other convex, and as I have found in practice by a long
series of experiments anu trials with said fans, and more particularly the large
sizes thereof, that it not only improves their working efficiency to have the oper
spaces which constitute the exterior and discharge ports of the intermediate
passage ways for the fluid between the blades, of considerably smaller width
(preferably about one-half) measured circumferentially around the fan (and
which measurement is hereinafter defined as the width) than that of the intake
or interior ports thereof, while at same time radial lines drawn from the
centre of the fan to either side of said exterior port are unobstructed by any
part of the blades forming the sides of the passage way from said interior to said
exterior ports, and also that it is frequently of much practical advantage and
utility that the fan can optionally be driven so as to revolve either with or
against the motion of the hands of a clock, and at same time work with maxi-
mum efficiency in either direction of revolution.
Now in carrying my invention into effect, I construct said blades, according
to one modification, and that which I preferably adopt, so that on both faces
they are concavely curved or angled relatively to an axially radial plane passing
through the inner axial edge of each blade, so that said curves or angles begin
to diverge from said axially radial plane, either at the interior edge of each
blade or at any preferred distance outward therefrom, and that the outer edges
of each pair of contiguous blades converge towards one another, whereby the
width of the exterior or discharge ports of the intermediate space or passage-way
for the fluid between them is made narrower to any suitable extent than the
interior or intake ports thereto, and that at same time the centres of said ex-
terior and interior ports are approximately radial to one another, so that if radial
lines be drawn from the centre of the fan to the two sides of said exterior port,
said radial lines will be to an equal extent clear of the inner edges of the blades
on each side of the interior port and in which case the fan will work with an
equally high efficiency whether it be revolved with or against the motion of the
hands of a clock.
According to another modification, I construct the blades so that one face
thereof is curved or angled as in the modification above described, and the
other approximately radial, in which case the exterior ends of each pair of con-
tiguous blades still converge towards one another, so as to make the width of the
exterior port considerably smaller (preferably one-half) than that of the in-
terior port, in which case the fan is not, however, equally efficient if revolved
in either direction. Or according to another modification the blades are made
radial on both faces from their inner edges to, or nearly to, the outer circum-
ference of the fan, where they are bent over to both sides, in the form of the
letter T, or to one side only. in approximately the form of the letter so that
the bent over edges of the T shaped blades approach those of the next nearest
blades and therefore narrow down the width of the exterior port between them
to any required smaller size than that of the interior port, and which construc-
tion allows of the fan being driven optionally in either direction of revolution:
while if made in the form of the letter L, the width of the exterior port can be
narrowed relatively to that of the interior port as much as may be required, but
the efficiency of the fan is less if revolved in one direction than in the other.
I do not limit myself to the exact formation of the blades hereinbefore des-
cribed, as I may also employ other modifications thereof to carry out the char-
acteristic feature of my invention, in regard to the formation or configuration of
the passage-way for the fluid between the blades which consists in having the
exterior or discharge port therefrom considerably smaller in its width. (and pre-
ferably about one-half) than that of the interior or intake port thereto, and so
located relatively to one another that two radial lines drawn from the centre

page_text: of the fan one to each side of said exterior port shall both pass through said
interior port and not cut through or be obstructed by any part of the blades
forming the sides of said passage ways. This feature of their arrangement, in
conjunction with the employment of an eye to the fan of equal or not less
diameter that ths that of the fan itself, produces increased pressure of dis-
charge from said ports, whereby an increased water gauge indication is also
obtainable when the fluid is drawn into the fan against resistances which cause a
partial vacuum therein, so that the fan thus operates with improved technical
effects the results of which are higher efficiency in working as compared with
fans as hitherto made.
T
1011
1
ր
1000
Improvements in Centrifugal Fans or Pumps.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ire-
land, 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 the following statement:
This invention has reference to the type of centrifugal fans or pumps (herein-
after referred to as fans) in which air, gases, vapour or liquid (such for instance
as air or water, and which are hereinafter referred to as the fluid) is drawn in
axially and discharged circumferentially, and more particularly to fans wherein
the intake opening through which the fluid enters the fan (hereinafter called
the eye) is of equal diameter to that of the outer tips of the blades or of not less
than ths of such diameter.
My improvements relate to the form and construction of the blades employed
therein, and one of the chief objects thereof is to increase the operative efficiency
of the fan, more especially in regard to its capability to either exhaust or propel
the fluid dealt with against resistances or back pressures (which are usually in-
dicated by the extent to which a column of water or other liquid is raised by
the operation of the fan), so that a larger volume of the fluid operated on shall
be drawn into the fan and discharged therefrom, and without return eddies or
back flow currents taking place from the tips of the blades inwards, or eddies
within the fluid passages between the blades, and at higher water gauge indica-
tions relatively to the diameter of the fan and its speed of revolution than in
fans as hitherto constructed.
My invention is hereinafter described and shown as applied to fans con-
structed as described in the Specification of previous Letters Patent granted to
me No. 4609 of 1898 and which have an eye of equal diameter to that of the fan
and narrow blades of considerably greater axial length than radial depth, with
the intermediate spaces or passage-ways for the fluid between the blades of a
not greater circumferential width than twice the radial depth of the blades, these
being mounted on the fan at right angles to its plane of revolution, by attach-
ment at one end to, a disc mounted on a central boss on the fan spindle, and at
the other end to an encircling ring or annulus.
Fans of the construction above referred to, have hitherto been fitted with
blades formed either as planes approximately radial and axial to the fan, or so
curved or angled through an axially radial plane that one face thereof is con-
cave and the other convex.

page_text: In the improved fans which are the subject of the present invention the open
spaces which constitute the discharge or exterior ports of the intermediate pass-
age ways for the fluid between the blades are of considerably smaller width
(preferably about this to ths) measured circumferentially around the fan
(and which measurement is hereinafter defined as the width) than that of the
intake or interior ports thereof, and the exterior and interior ports are so located
relatively to each other that two radial lines drawn from the centre of the fan
to the two edges respectively of said exterior port are unobstructed by any part
of the blades forming the sides of the passage way from said interior to said
exterior ports. This construction and arrangement much improve the working
efficiency of the fans, more particularly of the larger sizes, and further in most
modifications of the invention allow of the fan being driven with maximum
efficiency in either direction as required.
In the accompanying drawings:-
Figure 1 is a fractional end elevation as seen from the left hand end of
Figure 2 of a fan or pump with the blades constructed and arranged in accord-
ance with my invention in its preferred form..
Figure 2 is a sectional elevation on the line 2-2 of Figure 1.
Figures to 8 are fractional end elevations respectively illustrating modifi-
cations.
Referring first to Figures 1 and 2, A A are the blades; they are attached at
one end to a disc B which is carried by a boss or centre piece C keyed on the
shaft D and at the other end to an encircling ring or annulus E. The blades A
have both faces curved relatively to an axially radial plane so that the outer
edges of each pair of contiguous blades converge towards 'one another whereby
the width of the exterior or discharge ports F is narrower say about one-fourth
less than the width of the interior or inlet ports G. It will be seen that two
radial lines shown in dots at H H drawn from the centre of the fan to the two
edges respectively of an exterior port F are unobstructed by any part of the
blades A.
The modification shown in Figure 3 shows the same construction and arrange-
ment of the blades A as in Figure 1 except that the width of the exterior ports F
is only about one half that of the interior ports G.
In the modification shown in Figure 4 both faces of the blades A are concavely
curved as in Figure 1 and their outer edges are bent over as shown at J to meet
one another and thereby enclose the inactive space between them.
In the modification shown in Figure 5 both faces of the blades are flat from
their point of divergence from one another to their outer edges and, as in
Figure 4, their outer edges are bent back at J to meet one another and thereby
enclose the inactive space between them.
In the modification shown in Figure 6 the blades A are shown with one face
curved and the other radial.
In the modification shown in Figure 7 the blades A are radial and both their
edges are bent over as shown producing a form which is approximately that of
the letter T whereby the width of the exterior ports F is made much less than the
interior port G.
In the modification shown in Figure 8 the blades are radial and one edge is
bent over producing a form which is approximately that of the letter L thereby
reducing the width of the exterior ports F.
In all the modifications the two radial lines H H drawn from the centre of the
fan to the two edges respectively of any of the exterior ports F are unobstructed
by any part of the blades.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is—
1. In a centrifugal fan or pump in which the fluid is drawn in axially and dis-

page_text: charged circumferentially, a series of blades the spaces between which are the
passage ways for the fluid from the fan, the exterior ports of said passage ways
being less measured circumferentially than the interior ports thereof and said
exterior and interior ports being so located relatively to each other that two
radial lines drawn from the centre of the fan to the two edges respectively of
an exterior port are unobstructed by any part of the blades forming the sides
of the corresponding passage-way, substantially as and for the purpose set forth.
2. The several arrangements of the blades of centrifugal fans or pumps respect-
ively as shown in Figures 1 and 2, Figure 3, Figure 4, Figure 5, Figure 6,
Figure 7, and Figure 8 and herein before described.
Dated this 11th day of December 1899.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.