Improvements in Centrifugal Fans, and in Apparatus connected therewith.
Year: 1894

page_text: Date of Application, 17th Dec., 134
Complete Specification Left, 10th Sept., 1895-Accepted, 19th Oct., 1895
PROVISIONAL SPECIFICATION.
Improvements in Centrifugal Fans, and in Apparatus connected
therewith.
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 centrifugal fans of the class or type in which the
suction or exhaust is taken in at one or both sides and the delivery takes place at
the periphery and in which the vanes are rivetted at one edge to a disc and at the
other edge to an annulus or ring the said disc being securely fastened to a hub or
centre piece keyed on the fan shaft. Fans of this type are described in the
Specification of my Letters Patent of 12th January 1889 No. 612.
The object of my invention is to so construct and arrange the vanes of such fans
that they combine with their centrifugal delivery of air from the periphery of the
fan, a screw-like intake of the air at the eye of the fan, because of the sides of the
vanes being so exposed thereto that they cut into the air so efficiently like blades
of a screw, that any size of eye may be employed up to the full diameter of the
fan; while at same time the structural form and arrangement of these vanes give
such increased strength and stiffness to the fan, that it can be driven at exceedingly
high speeds without danger of flying to pieces from the power of the centrifugal
force thereby brought into operation.
My hereinafter described improvements consist in certain modifications of the
shape and constructive arrangements of the vanes of the fans, and of the annulus
which encloses and binds the outer edges of same together, while leaving a space
for delivery of the air between this annulus and the dise on which the vanes are
mounted, which disc I preferably make of sheet metal mounted on a cast metal hub,
fitted and keyed on the shaft by which the fan is revolved.
The vanes of my improved fans are flanged at right angles along the inner edge
and are rivetted to the disc by means of the flanges, so that the portion immediately
adjoining the flange stands at right angles to the disc; and the length of the
Hanged edge is approximately equal to about half the diameter of the disc; and
I mount the vanes upon the disc approximately as tangents to a circle preferably
about one-fifth to one-fourth the diameter of the disc, and concentric therewith the
vanes extending from the circle to the periphery of the disc.
I usually have 12 vanes on each disc, but their number may be either greater or
less, as desired, and each vane is formed into two planes, at a slight angle to one
another, by slightly bending the upper portion of the vane forward in the direction
that the fan revolves, along a line common to both planes. The plane which is
nearest the disc (and which I term the under plane) may be either quadrilateral or
triangular, but the bent-over plane which forms the upper continuation of the vane
(and which I term the upper plane) is usually of a triangular form, which varies in
shape according to whether the eye of the fau is to be the full diameter of the disc,
or less. The angle of the upper plane to the under plane is preferably about
20 degrees.
At the periphery of the disc I preferably make the height of the outermost edge
of the under planes such that the area of the open space left around the circum-
ference of the fan, between the disc and the edge of the annulus attached to, and

page_text: enclosing, the outer edges of the upper planes of the vanes, is equal to the area of
the intake or eye of the fan, and I preferably make the distance of the uppermost
angle of the upper planes, from the disc, about double the length of the outer edge
of the under planes. For low pressure blast the eye may be of any desired size up
to the full diameter of the fan, but for high pressure blast its diameter should be
decreased, though preferably not to less than half the diameter of the disc.
When for low pressure blast, the eye is made the full diameter of the fan, the
annulus encloses the outer edges of the upper planes of the vanes, as a band at
right angles to the disc, but when, for higher pressure of blast the diameter of the
eye is relatively decreased, the annulus is then equivalently sloped inwards from
the periphery, in the forin of a cross-section of a hollow-cone cut parallel with its
base, and the open centre of which forms the eye of the fan.
It will be at once seen that when the fan is revolving, the interior edge of the
bent-over upper plane of each vane will cut into the air in a screw-like manner,
and force it to the delivery space around the periphery between the annulus and
the disc without any appreciable slip of the air occuring over the intake edges of
the vanes.
My improved fans can have vanes constructed as hereinbefore described attached
on one or both sides of the disc, so that they may have either one or two eyes, or
spaces, for intake of air, as may be required.
My invention includes the combination with centrifugal fans of an apparatus for
heating the air before or after being passed through the fans. This apparatus
consists of an air heating chamber in which is a series of vertical metal pipes,
connecting a comparatively large top box or compartment with a basement one.
The top box receives steam or gaseous exhaust from the engine that drives the fan
or any other available exhaust (or alternatively, live steam from a boiler) and has
ample room for very considerable expansion in this box after which it descends in
an even current through all the tubes simultaneously into the basement com-
partment, which is fitted with a drain and exhaust pipe for the condensed water
and any steam or gaseous vapor that may still remain uncondensed. The air
passing through the said chamber on its way to or from the fan becomes heated by
contact with the hot surfaces of the expansion box and pipes through which the
steam or gascous vapor passes and also by contact with the inner sides of the said
chamber which are heated by radiation from the expansion box and pipes.
Dated this 17th day of December 1894.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Patent Agents.
Improvements in Centrifugal Fans, and in Apparatus connected
therewith.
1, 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 the following statement :-
My invention has reference to centrifugal fans of the class or type in which the
suction or exhaust is taken in at one or both sides and the delivery takes place at
the periphery and in which the vanes are rivetted at one edge to a disc and the
other edge to an annulus or ring the said disc being securely fastened to a hub or
centre piece keyed on the fan shaft. Fans of this type are described in the
Specification of my Letters Patent of 12th January 1889 No. 612.
The object of my invention is to so construct and arrange the vanes of such
fans that they combine with their centrifugal delivery of air from the periphery of

page_text: the fan, a screw-like intake of the air at the eye of the fan, because of the sides
of the vanes being so exposed thereto that they cut into the air so efficiently like
blades of a screw, that any size of eye may be employed up to the full diameter of
the fan; while at same time the structural forn and arrangement of these vanes
give such increased strength and stiffness to the fan, that it can be driven at
exceedingly high speeds without danger of flying to pieces from the power of the
centrifugal force thereby brought into operation.
The hereinafter described improvements consist in certain modifications of the
shape and constructive arrangements of the vanes of the fans, and of the annulus
which encloses and binds the outer edges of same together, while leaving a space
for delivery of the air between this annulus and the disc on which the vanes are
mounted, which disc I preferably make of sheet-metal mounted on a cast metal
hub, fitted and keyed on the shaft by which the fan is revolved.
The vanes of my improved fans are flanged at right angles along the inner edge
and are rivetted to the disc by means of the flanges, so that the portion immediately
adjoining the flange stands at right angles to the disc; and the length of the
flanged edge is approximately equal to about half the diameter of the disc; and I
mount the vanes upon the disc approximately as tangents to a circle preferably
about one-fifth to one-fourth the diameter of the disc, and concentric therewith the
vanes extending from the circle to the periphery of the disc.
I usually have 12 vanes on each disc, but their number may be either greater or
less, as desired, and each vane is formed into two planes, at a slight angle to one
another, by slightly bending the upper portion of the vane forward in the direction
that the fan revolves along a line common to both planes. The plane which is
nearest the disc (and which I term the under plane) may be either quadrilateral or
triangular, but the bent over plane which forms the upper continuation of the vane
(and which I term the upper plane) is usually of a triangular form, which varies in
shape according to whether the eye of the fan is to be the full diameter of the disc,
or less. The angle of the upper plane to the under plane is preferably about
20 degrees.
At the periphery of the disc I preferably make the height of the outermost edge
of the under planes such that the area of the open space left around the circum-
ference of the fan, between the disc and the edge of the annulus attached to, and
enclosing, the outer edges of the upper planes of the vanes, is equal to the area of
the intake or eye of the fan, and I preferably make the distance of the uppermost
angle of the upper planes, from the disc, about double the length of the outer edge
of the under planes. For low pressure blast the eye may be of any desired size
up to the full diameter of the fan, but for high pressure blast its diameter
should be decreased, though preferably not to less than half the diameter of
the disc.
When for low pressure blast, the eye is made the full diameter of the fan, the
annulus encloses the outer edges of the upper planes of the vanes, as a band at
right angles to the disc, but when, for higher pressure of blast the diameter of the
eye is relatively decreased, the annulus is then equivalently sloped inwards from
the periphery, in the form of a cross section of a hollow cone cut parallel with its
base, and the open centre of which forms the eye of the fan.
It will be at once seen that when the fan is revolving, the interior edge of the
bent-over upper plane of each vane will cut into the air in a screw-like manner,
and force it to the delivery space around the periphery between the annulus and
the disc, without any appreciable slip of the air occurring over the intake edges of
the vanes.
My improved fans can have vanes constructed as hereinbefore described attached
on one or both sides of the disc, so that they may have either one or two eyes or
spaces, for intake of air, as may be required.
My invention includes the combination with centrifugal fans of an apparatus for
heating the air before or after being passed through the fans. This apparatus
consists of an air heating chamber in which is a series of vertical metal pipes,

page_text: connecting a comparatively large top box or compartment with a basement one.
The top box receives steam or gaseous exhaust from the engine that drives the
fan or any other available exhaust (or, alternatively, live steam from a boiler) and
has ample room for very considerable expansion in this box after which it descends
in an even current through all the tubes simultaneously into the basement compart-
ment, which is fitted with a drain and exhaust pipe for the condensed water and
any steam or gaseous vapor that may still remain uncondensed. The air passing
through the said chamber on its way to or from the fan becomes heated by contact
with the hot surfaces of the expansion box and pipes through which the steam or
gaseous vapor passes and also by contact with the inner sides of the said chamber
which are heated by radiation from the expansion box and pipes.
The accompanying drawings more particularly illustrate the nature of my
improvements and how same are carried into effect:-
Figure 1 is a plan, Figure 1 a side elevation and Figure 1B an end elevation of
one of my improved vanes for a fan, in which the eye is two-thirds the diameter
of the disc.
Figures 2, 2 and 2 shew respectively a plan and side and end elevations of
one of my improved vanes for a fan in which the eye is the same diameter as
the disc.
Figures 3, 3 and 3B shew respectively a plan and side and end elevations of a
modification of the shape of vane shown in Figures 1, 14 and 1B in which the under
plane is quadrilateral instead of triangular.
Figure 4 is a vertical section; Figure 5 an end elevation, and Figure 6 a sectional
elevation of a fan in which the eye is two-thirds the diameter of the disc, and with
vanes on one side of the disc only; the figures also show my improved method of
driving centrifugal fans and my improved apparatus for heating the air that passes
through them; the fan and air heater are arranged for the fan to draw the air
supply through the heater.
Figure 7 is a vertical section; and Figure 8 a sectional elevation of a fan in
which the eye is the full diameter of the disc and in which the vanes are on
both sides of the disc; and there are air inlets on both sides of the fan casing.
The same letters of reference indicate corresponding parts in the various figures.
AA are the vanes, a' being the under planes and a the upper planes of same.
is the flange on the edge of the plane a' of each vane by which it is rivetted to
the disc B. c¹ is the flange on the edge of the plane a² of each vane by which it is
rivetted to the annulus or ring C. the fan represented in Figures 4, 5 and 6,
the eye of which is two-thirds the diameter of the disc B, the annulus C is sloped
inwards in the form of the cross section of a hollow cone as already hereinbefore
described, while in the fan represented in Figures 7 and 8 in which the eye is the
full diameter of the disc B the annulus C is at right angles to the disc B. The
disc B is rivetted to the hub or centre piece D which is keyed on the fan shaft E.
F F are the fan shaft bearings carried by the standard or bracket G G. H is the
fan casing, J the air inlet in the casing to the eye I of the fan and K the outlet
through which the pressure blast is delivered. L is a driving pulley keyed on the
fan shaft; it is driven by a direct belt or band W from a pulley of larger
diameter T on the crank shaft V which is driven by the engine M, this engine
being carried by the standard G. N is the exhaust pipe from the engine leading
to an expansion box Q which is connected by a series of pipes P in an air heating
chamber with a lower box S so that the steam or gascous exhaust from the
engine M expands in the box Q, then descends the pipes P to the box S which is
fitted with a drain and exhaust pipe not shown. R is a deflecting plate in the
box Q. Instead of arranging this air heating apparatus at the supply side of the
fan as shown, and which is preferred, it may be arranged on the discharge side in
which case the fan outlet K may lead into a chamber fitted with the air heating
apparatus, this chamber having a suitable blast outlet as will be readily
understood without further description or illustration. The exhaust admitted
to the box Q does not necessarily come from the engine that drives the fan as i
:

page_text: may come from any other available source, or instead of exhaust it may be live
steam from a boiler.
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 what I
claim is-
1. In the vanes of centrifugal fans, the combination of two planes at a slight
augle to one another as set forth, the one plane acting like the blade of a
screw propeller to draw the air into the eye of the fan, and the other plane to
discharge the air centrifugally through the space between a disc to which the
inner edge of every vane is attached, and an annulus binding together and enclosing
the outer edges of the screw-like planes of the vanes, all substantially as herein-
before described and represented in the accompanying drawings.
2. The constructive form of the vanes, and their general arrangement on the
disc, in combination with an annulus enclosing the outer edges of the screw-like
planes of the vanes, all substantially as herein before described and represented in
the accompanying drawings.
3. The combination, with a centrifugal fan, and a chainber connected therewith
and traversed by the air that passes through the fan, of an expansion box at the
upper part of the said chamber supplied with steam or gaseous exhaust or live
steam, and vertical pipes inserted into the under side of same and leading down the
said chamber from the expansion box into a receiving box below in which each of the
said pipes terminates, and an exhaust pipe therefrom to effect an even flow of the
steam or gaseous vapor from the expansion box through the pipes to the exhaust box
whereby the air passing through the chamber is heated by contact with the hot
surfaces of the expansion box and pipes all substantially as hereinbefore described
and represented in the accompanying drawings.
Dated this 10th day of September 1895
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.