VENTILATING AND EXHAUST FANS
Year: 1883

page_text: LETTERS PATENT to Edwin Powley Alexander of 36 Southampton Buildings
"
in the County of Middlesex, Fellow of the Institute of Patent Agents, for
an Invention of "IMPROVEMENTS IN
communicated to him from abroad by Lucius George Fisher the Younger
VENTILATING AND EXHAUST FANS
PROVISIONAL SPECIFICATION left by the said Edwin Powley Alexander
at the Office of the Commissioners of Patents on the 19th March 1883.
EDWIN POWLEY ALEXANDER of 36 Southampton Buildings in the County
of Middlesex Fellow of the Institute of Patent Agents "IMPROVEMENTS IN
VENTILATING AND EXHAUST FANS," a communication to me from abroad by Lucius
George Fisher the Younger of Chicago, Cooke County, Illinois in the United States
of America
This invention consists first in a ventilating fan so constructed as to rapidly
transmit motion to large volumes of air carrying the same in solid columns without
radial or back currents and in such application of the said fan as will ensure the
speedy drying of malt and other substances.
In the improved fan the blades carry, or revolve within, a peripheral ring frame
or section and this prevents the radial flow of the air thus compelling the large
volumes ordinarily dissipated in this direction to move directly forward.
It is necessary to so construct each blade of the wheel as to draw or deflect
outward the air from the advancing edge of every portion of the blade and to set
every portion or face of the blade at such an angle that the advancing edge at
every point will "cut under" the air rather than move it laterally or carry it withi
the wheel.
It is also advisable to vary the angle and curve of the blade at different points,
although such angles and curves will be different according to the sizes of the
wheels and number of blades.
From the hub of the fan extend ribs meeting an annular rim which ribs con-
stitute the straight outer and inner edges of the blades the rim and ribs being all
in the same vertical plane.
The diameter of the hub and the depth of the wheel should to secure the best
results be about equal to one sixth of the diameter of the wheel and the outer ribs
or edges instead of being radial should be set to coincide with a line somewhat
tangential to the hub so as to dip or pitch forward to prevent radial dispersion of
the air.
The blades are set to join the hub upon lines crossing the axial line at an angle
at the centre and the inner but advancing edge of each blade corresponds to a

page_text: curve which is gradually increased toward the outer end these edges of all the
blades being upon a plane parallel to the vertical plane of the rim and ribs
above mentioned.
The body of the blade between the edges or outer and inner ribs is gradually
bent at an angle which becomes more and more obtuse to the axis of the shaft as
it approaches the periphery and is also gradually more and more curved from its
junction with the outer edge rib, toward the inner edge rib
At the periphery the blade is bent to form a peripheral section that extends
from the blade to the rim and has a forward edge parallel to the axis of the shaft.
This peripheral section may form part of the blade or may be a separate piece,
rivetted or otherwise secured thereto and may be carried by the blades or may be
separate therefrom.
By setting the blade at an angle to the axis by maintaining the portion near the
hub comparatively flat by bending the body beyond the centre and by giving a
sharper curve thereto near the periphery where it meets the peripheral section as
described back flow is prevented and with comparatively little power movement
may be imparted to large volumes of air in one direction and in nearly solid
columns.
This effect is increased by setting the blade somewhat tangential to the axis,
instead of radially the outward end thus being pitched forward so as to draw in
the air instead of dispersing it radially.
It will be evident that the outer and inner ribs may be flanges formed by
bending the edges of the blades or they may be dispensed.
It is common to set ventilating fans in openings in walls or frames which
completely surround the peripheries of the fans and prevent any radial inflow of
air. By setting the fan in a case and back from such opening a fan larger than
the opening may be employed and a better result secured.
Where it is not advisable to have the peripheral section carried by the blades
the said section may be made part of a stationary frame having cross rods sup-
porting bearings in which turn the journals of the fan shaft. The structure is
thus self contained and may be supplied as a whole to be set without adjustment
of parts in any required position.
This peculiar exhausting fan can be applied generally for purposes of ventilation,
drying and the like and is especially adapted for use in drying large porous masses
of material such as grain and wool. For drying malt the fan is arranged in the
upper part of the malt house adjacent to one of the windows or in a vertical or
horizontal position in the cupola.
In such houses it has been customary to blow the hot air through the malt on
perforated floors and to stir the grain with mechanical stirrers. Instead of this
an exhaust fan arranged as described will draw the air from above the upper floor
so that the air is rarefied and carried in a rarefied condition from the furnace
through the perforations of the successive floors and finally expelled through the
opening above the fan.
The lifting of the grain which results from the upflowing currents of air renders
unnecessary the employment of mechanical stirrers.
The use of an exhaust apparatus for lifting the grain is important, for it has
been found that an exhaust has a much better effect than a blower, as when the
air is propelled from below it will seek the easiest passage out and loses force
from leakage whereas when an exhaust is arranged above the floors the air is
drawn through every portion of the floors and slight leaks have no detrimental
effect.
I do not however claim broadly the use of an exhaust in a malt-house this part
of my invention being distinguished by the fact that I dispense with mechanical
stirrers and secure the desired rapid drying effect by lifting and stirring the grain
by an upward current produced by an exhaust apparatus.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edwin Powley Alexander in the Great Seal Patent Office on
the 11th September 1883.
EDWIN POWLEY ALEXANDER of 36 Southampton Buildings in the County
of Middlesex Fellow of the Institute of Patent Agents. "IMPROVEMENTS IN
VENTILATING AND EXHAUST FANS" A communication to me from abroad by
Lucius George Fisher the Younger of Chicago Cooke County Illinois in the United
States of America.
A ventilating or exhaust fan according to this invention is constructed as shown
by the accompanying drawings, Figure 1 being a back view and figure 2 a sectional
plan in line 1-2 of figure 1. Diagrams figures 3 to 7 inclusive illustrate the
formation of the blades and figure 8 is a perspective view of one blade detached.
The boss or nave A may be solid or it may consist of discs a a¹ fixed on the
shaft B. From the nave extend straight front ribs b to an annular rim c in the
same plane with them. From the nave also extend the back ribs e which curve
forwards gently at first but more rapidly as they approach the circumference.
Between the straight front ribs b which constitute the leaving edges of the blades
and the curved back ribs e which constitute the entering edges extends the blade D
which partakes of the curvature of the back ribs as indicated by the dotted lines
in figure 1 representing successive sections in planes of revolution. The blade is
set at an angle to the axis as shown in figure 3 where yy indicates the root of the
blade as it springs from the nave A and the other oblique lines show sections at
various radial distances from the axis. The width of the wheel from front to back
should be about one sixth of its diameter and each blade instead of being radial
as indicated in figure 6 should have its root at the nave behind the radial line
drawn from its periphery as indicated in figure 7 so that it has a forward pitch
in the direction of revolution. It is to be understood that the construction
described is not that of a blade curved throughout as indicated in figure 4 which
has the effect of gathering the air towards the middle and so producing back
currents nor is it that of a blade such as is shown in figure 5 which being nearly
parallel to the axis would have little propelling effect; The true form is shown by
the perspective view figure 8 shewing the back of the blade D, with a triangular
segment plate d covering the part of the periphery bounded by the ends of the
front and back ribs b and e and the ring c. Instead of forming the segments & as
parts of the wheel itself the wheel may be mounted within an annular casing as
shown in figures 9 and 10 this casing having attached to it an open back and front
framing with bearings a for the shaft B on which the driving pulley A may be
fixed within the framing. Thus the wheel and its frame constitute a self contained
structure which may be conveniently fixed in an opening through which a current
of air has to be sent. Figure 11 is a vertical section of a building such as a malt
house with the fan D arranged in the roof so as to draw air or heated air through
the grain or material spread on the perforated floors.
Having thus described the nature of this invention and in what manner it
is to be performed as communicated to me by my foreign correspondent I claim :-
First. The construction of ventilating or exhaust fan having blades each of
which is set at an angle to the shaft extending between a straight front rib or
leaving edge and a forwardly curved back rib or entering edge and terminates with
a segment plate at the periphery substantially as herein described.
Second. Setting the blades such as are referred to in the preceding claim with a
forward pitch radially as described with reference to figure 7.

page_text: Third. The combination of a ventilating or exhaust fan such as is referred to in
the preceding claims with a casing and open framing having bearings for the shaft
as herein described with reference to Figures 9 and 10.
In witness whereof I the said Edwin Powley Alexander have hereunto set my
hand and seal this tenth day of September in the year of our Lord one thousand
eight hundred and eighty three.
EDWIN P. ALEXANDER (L.S.)