Improvements in Ventilating Fans.
Year: 1897

page_text: I, WILLIAM GEORGE WALKER, of 47, Victoria Street, in the City of Westminster,
Engineer, do hereby declare the nature of this invention to be as follows:- -
My invention relates to those ventilating fans or air propellers of the screw-
propeller type, which are employed in ventilating buildings factories or ships, or
in drying goods or fabrica by the propulsion or suction of air.
The object of my invention is to increase the efficiency of a fan when propelling
or drawing air through a contracted orifice, or when the outlet or inlet of the air
passage is baffled by some material which offers a resistance to the moving air,
such as propelling or drawing air through a tortuous flue or through a material
which has to be dryed; in other words to improve the power of a fan for producing
a pressure or velocity in the air.
My invention consists in placing a disc or plate in front of the fun, that is on the
delivery side and touching the fan, the diso or plate may be flat or of a shape to
suit the shape of the blades of the fan, and is of a smaller diameter than the fau.
The passage of the air is not thereby blocked for feeding the fan, for it can still
receive air at its centre at the back or non-propelling side of the fan.
Fans as generally made are unable to maintain a large static pressure of the air
on account of the air tending to rush back again through the contral parts of the
fan, caused by the speed of those central parts of the blades being smaller than the
parts nearer the tips of the blades.
Fig. 1 in the accompanying sheet of drawing, shows a fan propelling air through
a contracted tube. The disc which constitutes my invention is shown at 1).
Fig. 2 is an end view of the fan with disc. Fig. 3 shows a fan drawing air through
a contracted tube, the disc being shown at D in front of the fan. Fig. 4 shows an
ordinary fan without the disc propelling air.
Improvements in Ventilating Fans.
I, WILLIAM GEORGE WALKER, of 47, Victoria Street, in the City of Westminster,
Engineer, do hereby declare the nature of this invention and in what manner the
5 same is to be performed, to be particularly described and ascertained in and by
the following statement: -
My invention relates to those ventilating fans or air propellers of the screw-
propeller type, sometimes called helical or screw fans, which are employed in

page_text: ventilating buildings factories ships mines or in the drying of goods and fabrics
or causing draught for boilers by the propulsion or suction of air.
The object of my invention is to increase the efficiency of a fan when propelling
or drawing air through a contracted orifice or when the outlet or inlet of the air
passage is baffled by some material which offers a resistance to the moving air, such
as propelling or drawing air through contracted or tortuous flues or through
material to be dryed, in other words so that a higher vacuum or compression of the
air can be obtained.
My invention consists in fixing a disc or plate of suitable shape or a conical
shaped body in front on the delivery side and touching the fan being of a smaller
diameter than the fan so that the air can still feed into the fan from behind at the
central parts, in other words so that the area of feed into the fan is not reduced by
the central disc or plate.
Fans or air-propellers of the screw-propeller type draw in air from behind and
discharge it forward in the shape of a cylindrical column and generally at
atmospheric pressure they are unable to move air under compression or vacuum
to any great extent, which may be necessary when the air is to be forced or sucked
through some resistance such as contracted or tortuous flues or material to be
dryed, this is on account of the air tending to rush back again through the contral
parts of the fan caused by the speed of those parts of the blades being smaller than
the parts nearer the tips of the blades. The object of the central disc or plate is
to prevent the air leaking back again through the comparatively slow moving parts
near the centre and yet enable the air to be sucked in at the centre behind the disc.
Fig. 1 in the accompanying sheets of drawings shows a fan propelling air
through a contracted tube, the disc which constitutes my invention is shown at D.
Fig. 2 is an end view of the disc and fan.
Fig. 3 shows a fan with disc D drawing air through a contracted tube the arrows
showing the direction of the air currents.
Fig. 4 shows a fan without the disc, propelling air the arrows show the air leak-
ing back again through the centre, Figs. 5, and 6 show conical discs, Fig. 7, shows a
fan forcing air through a contracted tube T, the disc being now of conical shape
in order to better direct the motion of the air. The disc may be fixed separately
on to the fan after the fan is made or it may be made as part of the boss connect-
ing the blades to the spindle. Those portions of the blades which are in the same
concentric circle as the disc may if necessary be in same plane as the axis of the
fan or may only consist of connecting rods for in that central part the air takes a
radial direction to the outer circumference of the disc when it is propelled forward,
Fig. 8 show the central parts of the blades flat and in same plane as the axis of the
fan.
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:-
Constructing a ventilating fan of the screw-propeller type so that the central
part in front on the delivery side of the fan is blocked to the passage of air by a
disc, plate, or cone, touching the fan so that the air can still flow in to the fan
from behind on the sucking side, substantially as in this specification described,
and in reference to the drawings illnelmsted
Dated this 30th day of December 1897.
To the Comptroller, Patent Office,
W. G. WALKER,
25, Southampton Buildings,
Chancery Lane, London, W.C.