Improvements in Centrifugal Fans.
Year: 1890

page_text: Complete Specification Left. 21st Feb., 1891-Accepted, 21st Mar, 1897
PROVISIONAL SPECIFICATION.
Improvements in Centrifugal Fans.
1, CARL WENNER, of Zurich, Switzerland, Engineer, do hereby declare the
nature of this invention to be as follows:-
This invention relates to a compound high pressure or centrifugal fan, having
concentric rings or annular rows of blades or vanes, all the rings or rows being
mounted on a common shaft in such a manner as to be capable of being revolved
independently of one another in the same direction.
Such a fan is self contained and is designed to produce considerably higher blast
pressures, than it is possible to obtain with ordinary or non-compound fans.
A fan according to this invention is illustrated, by way of example, in the annexed
drawings,
Fig. 1 being a vertical section through the axis, and
Fig. 2 a vertical section at right angles to the axis.
His a casing formed with a foot or base piece, and with side bearings LL
to support a shaft S: A B C are centrifugal fans or annular rings arranged con-
centrically and all mounted on the common shaft S; these fans or rings are of
different diameters and are furnished with rings or annular rows of blades or
vaness, s² 2, 3, (Fig. 2), of suitable form and bounded laterally by walls.
The arrangement illustrated is a three-stage fan i.e. one having three rings of
vanes.
Fans according to my invention can however be constructed as two-stage fans,
that is to say with only two rings of vanes.
The several fans, A B C, are driven independently of one another, each being
The smallest of these
driven from a separate belt pulley P1, P2 or P³ Fig. 1.
fans, A, is fixed on the shaft S and is driven from the belt pulley P'; it is open
at both sides, to allow of the entrance of the air, as indicated by arrows.
The next largest or second stage fan B projects with its ring of vanes ³, s, over
the ring of vanes ss, of the fan A, and is constructed with a nave which is
situated to the right of the nave of the fan A, and is mounted on the shaft S in
such a manner as to be capable of rotation about that shaft. The nave of the
fan B carries the driving pulley P. The spokes or arms that carry the ring of
vaness, are so far as they cover the lateral circular opening at one side of the
fan A, formed as screw surfaces (Fig. 2) so that they act as a screw fan during
the rotation of the fan, and allow the air to pass without hindrance into the fan A
from that side at which they are located. The third stage fan C is, as shewn at
the left in Fig. 1, mounted loosely on the shaft S and projects with its vanes &³, s³,
over the second stage fan B. It carries on an extension of its nave the driving
pulley p³, and is, similarly to the fan B, provided with spokes cc which are formed
as screw surfaces to allow the air to enter without hindrance into the fan A. from
that side at which the spokes c are located. In a two-stage compound fan this third
stage fan is of course dispensed with the mutual action of the other two fans
remaining the same.

page_text: The operation of the apparatus is as follows:-
:-
The fans A, B, C, all rotate in the same direction as indicated by the arrows
in Fig. 2; but are driven at different speeds, that is to say at different numbers of
revolutions in a given time and in such a manner that the largest stage fan shall
make a less number of revolutions in a given time than the next smallest and so
that the peripheral speeds of the several fans are approximately equal to one
another. But since the air, which moves radially from the centre towards the
outside, through the fan, is brought by stages in each stage fan to a higher
pressure, it can be compressed in this manner to approximately twice, thrice or
more times the pressure which could be obtained with a one stage fan only, with
the same number of revolutions. On leaving the last stage fan, C, the air passes
into the annular casing H, which encloses the fan C at its periphery, and leaves the
casing H by the opening O.
Dated this 2nd day of Navambion 1200
COMPLETE SPECIFICATION.
Improvements in Centrifugal Fans.
I, CARL WENNER, of Zurich, Switzerland, Engineer, 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 relates to a compound high pressure or centrifugal fan composed
of two or more single fans provided with annular rows of blades or vanes all the
said fans being mounted on a common shaft in such a manner as to be capable of
being revolved independently of one another in the same direction.
Such a compound fan is self contained and is designed to produce a considerably
higher blast pressure than it is possible to obtain with ordinary or non-compound
fans.
A compound fan according to this invention is illustrated, by way of example, in
the drawings filed with my Provisional Specification,
Fig. 1 being a vertical section through the axis; and
Fig. 2 a vertical section at right angles to the axis of a triple compound fan.
H is a casing formed with a foot or base piece, and with side bearings L L to
support a shaft S; A, B, C are simple centrifugal fans or annular rings of blades
arranged concentrically, and all mounted on the common shaft S; these fans are of
different diameters and are furnished with annular rows of blades or vanes s¹ s₁₂
§² s², s³ 5³, (Fig. 2), of suitable forms, being mounted on radial arms or on a
central disc and ²², son lateral discs.
The arrangement illustrated is a triple fan i.e. one having three single fans or
independent rings of vanes.
Fans according to my invention can however be constructed as double fans,
that is to say with only two independent rings of vanes. The axis S in this case
may be stationary instead of being arranged to turn, the two fans B and C revolving
freely upon it.
The several fans A, B C are actuated independently of one another, each being
driven by a separate belt pulley P¹, P² or P³ Fig. 1. The smallest of these fans A,
is fixed on the shaft S and is driven from the belt pulley P; it is open at both
sides, to allow of the entrance of the air, as indicated by arrows.
The next larger or second fan B projects with its ring of vanes 82, 82, over the
ring of vaness, of the fan A, and turns with its long boss freely upon the shaft S
at the right hand side of the fan A Fig. 1. The prolonged boss of this fan B
carries the driving pulley P. The spokes or arms that carry the ring with
vanes &², are, as far as they cover the lateral circular opening at one side of the
fan A, formed as screw blades Fig. 2, so as to allow air to pass freely into the
fan A during rotation. The third fan C, analogous to 'fan B, as shown at

page_text: the left in Fig. 1, turns freely upon the shaft S and projects with its vanes 8³, 8³,
over the vanes of the second fan B. It carries on its prolonged boss the
driving pulley P³, and is, like the fan B provided with spokes or arms c c formed as
screw blades or surfaces to allow air to freely enter the fan A from this side. In
a double compound fan, a third fan is of course dispensed with, the reciprocal action
of the other two fans remaining the same as already mentioned.
The action of the apparatus is as follows:
The fans A, B, C, all rotate in the same direction as indicated by the arrows
in Fig. 2; but are driven at different speeds, that is to say at different numbers. of
revolutions in a given time, and in such a manner that the larger fan makes a less
number of revolutions in a given time than the next smaller one, so that the
peripheral speeds of the different fans are approximately equal to one another.
By these means the air is brought to a certain pressure in the first fan A, corre-
sponding to the circumferential speed of this fan, and enters the second fan B, under
such pressure. This second fan B in its turn imparts to the wind an additional
pressure corresponding to its circumferential speed, and the wind enters the third
fan C under a still higher pressure, which, through the action of this last fan C is
again augmented. Thus the air can be brought to a pressure approximately double
or triple (according to the number of fans) of that pressure which would correspond
to the circumferential speed of only one of the fans. On leaving the last fan, C,
the air passes into the annular casing H, and leaves it by the opening O.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1
1. A. compound centrifugal fan, composed of two or more single fans, arranged
concentrically upon a common shaft or axis and driven independently of one
another, in the same direction, but with different numbers of revolutions, by means
of separate belt pulleys.
2. In centrifugal fans of the kind referred to in the preceding claim, forming the
spokes or arms b b and c c carrying the second and third fans B and C, respectively,
as screw blades for the purpose of allowing air to enter the fan freely from both
sides during rotation.
Dated this 21st day of February 1891
C. WENNER
By L. W., per F. B.