for Blast and Exhaust Purposes.
Year: 1887

page_text: Date of Application, 26th Feb., 1887.
Specification Accepted, 29th Mar., 1887.
for Blast and Exhaust Purposes.
1 RICHARD KENDALL EVANS of Clumber Lodge, The Park, Nottingham, in the
county of Nottinghamshire, 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 certain improvements in the construction of centrifugal
pumps and fans for blast and exhaust purposes, and has for its object to so construct
and arrange the vanes and parts composing the fan or pump as to force or draw a
greater quantity of fluid and impart thereto a greater velocity than heretofore.
I will now fully describe my invention in reference to the accompanying drawings
in which Figures 1 and 3 are end elevations with half the casing removed, and
Figures 2 and 4 are longitudinal sections on centre line of two slightly different
arrangements of machines constructed according to this invention. The fan or pump
is mounted on a shaft A, rotating in bearings formed in the frame B and provided
with the usual driving pulley. The fan is enclosed in a casing which may be of
either form shown in the figures and the whole is mounted on a foundation plate in
the usual manner. According to one arrangement if the vanes are arranged as shown
in Figures 1 and 2, the leading vanes D may be constructed either in two separate
pieces leaving a port or opening d of suitable area about midway, or they may be
constructed in one piece having the said mid port d cut out of the material
composing the vane. The leading vanes D are segmental arcs of circles the radius
of each being about equal to the distance from centre to centre of the midway
ports therein (that is to say from d to d figure 2) should six vanes be used, or
should other than six vanes be used the radius may be made about equal to three fifths
of the radius of the fan or pump.
Any desired number of such leading vanes D may be attached to side armis d' of
the same radii suitably fixed to the rotary shaft A. Side plates E are attached to
these arms, these plates extending all round the machine from its periphery towards
the centre and the inlet or entry openings c of suitable area are formed around the

page_text: central shaft A on either side for the admission of fluid: On the convex side of each
leading vane D at the outer side of the mid port d a supplementary segmental vano F
is affixed either rigidly or capable of adjustment its radius being preferably from
about a half to two thirds that of the leading vanes D. Its free end extends towards
the centre of the machine and terminates at a suitable distance below the inner edge
of the midport d of the next leading vane on the concave side thereof forming a port
The position of the lower extremity of F may be made adjustable so as to vary its
distance from the inner edge of the mid port of the next leading vane on the concave
side as required or to take a central or nearly central position (as shown in figure 2)
between the leading vanes according to the work to be done. These supplementary
vanes F when rigidly fixed may also be attached to side arms of same radii fixed
to or forming part of the side arms of the leading vanes. Or, according to another
arrangement illustrated by figures 3 and 4 I may introduce additional supplementary
vanes G G fixed in the same manner as described for the 'leading vanes DD the object
of which is hereinafter set forth.
By these arrangements in the rotation of the fan or pump (in the direction
indicated by the arrow) a continuous current of fluid is drawn through the central
inlet ports and midports d of the leading vanes into the outer or increasing space N
between the vanes and this current tends to form a vacuum and so induce a supple-
mentary current through the adjustable ports the position and shape of all the said
vanes imparting velocity to such fluid until it is discharged through the delivery
port P.
By the use of the additional vanes G, G, a higher efficiency is gained, their effect
being to contract, the area N and thereby in some measure throttling the entering
fluid, to diminish the back pressure and increase the velocity and pressure and
consequent tendency to vacuum in the circumferential space between the vane tips
and the casing, which in this case may advantageously be made of increasing area in
the well known manner illustrated in figures 3 and 4.
In either case the vanes may be made tapering towards their tips and also the
casing if desired as shown in figure 3.
Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed I declare that what I claim is:
1.).In the construction of centrifugal fans or pumps the hereinbefore described
arrairgement of vanes and ports consisting of leading vanes having midports d and
supplementary vanes forming ports adjustable or not as regards their area as
required all arranged substantially as and for the purposes described, and illustrated
in figures 1 and 2 of the 'accompanying drawings.
+
2.) In the construction of centrifugal pumps or fans,. the combination with the
arrangement of vanes hereinbefore described and illustrated in reference to figures
and 2, of the additional vanes GG described and illustrated in reference to figures 3
and 4 of the accompanying drawings.