Improvements in Rotary Fans.
Year: 1889

page_text: Improvements in Rotary Fans.
I. SAMUEL CLELAND DAVIDSON, of Sirocco 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:
The invention relates to rotary fans of that class in which the suction or exhaust is
taken in at one side only and the delivery takes place at the periphery. Fans of this
class as hitherto constructed have had their vanes connected to the fan spindle by arms
which are necessarily a considerable distance apart, the effect of which is that as the
number of vanes is small the air that is drawn in is apt to circulate back into the fan
unless there is a casing to enclose the air in upon the vanes until in circulating round
between the vanes and the casing it attains the velocity of the vanes and acquires
sufficient centrifugal force to carry it through the comparatively small delivery
opening with sufficient speed to indicate a pretty good vacuum into the fan. But by
the improved constructionhereinafter describedwhich constitutes the present invention
the vanes can be placed very closely together no connecting arms to the fan spindle or
axle being required, and the spaces between the vanes are sufficiently contracted to
prevent any tendency of the air to circulate back into the fan. The narrow spaces or
pockets between the vanes compel the air to take the speed of the fan at once.
The improved fan is composed of vanes formed of rectangular pieces of sheet metal
(in length preferably equal to a sixth of the diameter of the fan) with small flanges
on two opposite sides and the outer edge turned over in line with the circle of the fan
to reduce the exterior opening between the vanes and of a sheet metal disc and a sheet
metal ring or annulus to which the two sides of the vanes are respectively rivetted by
means of their flanges. The vanes are set at an angle of 30° to 40° to radial lines
from the centre of the fan and at about three inches apart around its periphery. The
sheet metal disc which forms one side of the fan is fastened securely to the true face
of a cast metal centre piece or hub having a spigot that exactly fits a concentric hole
077

page_text: in the disc. The hub is keyed on a spindle carried in self adjusting bearings which
are fitted into arms or other suitable supports secured to the frame or casing of
the fan.
The whole forms a strong, efficient, well balanced, easy and almost silent running
fan, and the vanes have no other support from the spindle than that given by the
sheet metal disc, so that a free and unobstructed passage for the air from the centre of
the fan to the vanes is thus provided.
The fan may have the delivery either open all round, or partially closed in such a
way as to pass the air current parallel to the axis or spindle, or conducted by a suit-
able casing into a pipe or air flue; and in all cases it can be used either as a pressure
blower or as an exhauster.
The accompanying drawings illustrate the construction of the fan in the three
modifications above referred to. Figure 1 is a front elevation and Figure 2 a vertical
cross section of the modification in which the fan is open all round its circumference
for the free escape of air. Figure 3 is a front elevation and Figure 4 a vertical cross
section of the modification in which the fan is partly enclosed, the form of the
enclosing casing being such as to throw the air almost parallel to the axis of the
spindle. Figure 5 is a front elevation, Figure 6 a cross section. Figure 7 a back
elevation and Figure 8 a plan of the modification in which the fan is provided with a
complete casing. The same letters of reference indicate corresponding parts in all the
figures.
A A are the sheet metal vanes, B is the sheet metal disc and C the sheet metal
ring or annulus to which the two sides of the vanes are respectively rivetted by means
of their flanges. D is the cast metal centre piece or hub to which the disc B is
rivetted. E is the fan spindle or shaft to which the hub D and driving pulley N are
keyed. F F are the self-adjusting bearings. F2 is a cap on the inside bearing F to
make it dust proof. G G are arms for supporting the bearings F F. H is a flange
supporting the outside bearing in the modification shown in Figures 5 to 8. J is a
ring or frame to which the arms G G in Figures 1 and 2 are bolted. K-Figures 3
to 8 is the fan casing. KK-Figures 6 and 7 are segmental pieces fastened to the
casing K for enclosing the inner rim of the fan in the casing. K-Figure 8 is a
block or stopper in the inside of the casing to prevent the air circling round with the
fan. L is a flange on the ring J of Figures 1 and 2 and on the casing K of Figures 3
to 8 for bolting the same to the air duct or the partition. M Figures 5 to 8 is the
flange for blast pipe. N N are the fast and loose pulleys and O the belt fork sliding
on the bracket P.
It will be seen that in the modifications shown in Figures 1 to 4 the bearings are
both supported with arms, the front arms in Figures 3 and 4 being sunk flush with
the flange L. In the modification shown in Figures 5 to 8 the bearings on one side
are supported by the flange H in the casing K. Instead of the casing being split in
the ordinary way to allow of the fan being placed inside it it has an opening on one
side of slightly larger diameter than the fan, through which the fan is put into place
inside the casing, after which the opening is closed in round the edge by the narrow
segmental pieces K2 K butting at each end against the arms G G (see Figure 7) to
prevent any passage of air between the exhaust and discharge ports.
Figure 9 is a side elevation of a portion of the fan showing the vanes A with their
outer edge turned over as seen at a in line with the circle of the fan to reduce the
exterior opening between the vanes to somewhat less than the space between their
interior edges. It will generally be found better to turn over the edges of the
vanes in this way because it improves the efficiency of centrifugal fans to have the
exit opening between the vanes at the periphery equal to or slightly less than
the inlet opening. The turning over of the edge has the further advantage of
increasing the strength of the vanes.
Although the improved fan above described is applicable to a variety of purposes
as will be well understood, it has been specially designed for use in connection
with what is known as the Sirocco tea drying apparatus for which reason it may
appropriately be designated the Sirocco Fan.

page_text: 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 a rotary fan of the class herein referred to the combination of rectangular
sheet metal vanes, a sheet metal disc, and a sheet metal ring or annulus, said vanes
being rivetted on the one side to said disc and on the other side to said ring or
annulus and said disc being securely fastened to a centre piece or hub keyed on the
fan spindle, the vanes having no other support from the spindle than that given by
the disc, so that a free and unobstructed passage for the air from the centre of the
fan to the vanes is provided while the vanes can be placed very closely together,
substantially as hereinbefore described.
2. The several arrangements or combinations of parts of rotary fans hereinbefore
described and represented in the annexed drawings.
Dated this 12th day of January 1000
J. C. MEWBURN,
55 & 56, Chancery Lane, London,
Patent Agent.