Improvements in impact-wheels or Turbines.
Year: 1898

page_text: Improvements in impact-wheels or Turbines.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention to be as follows:-
My improvements relate to impact wheels or turbines, and more particularly
to the class or type known as l'elton wheels, and the objects, amongst others, of
my invention are to so construct the buckets and the periphery of the wheel
that together they shall combine simplicity and lightness of construction with
sufficient strength to resist the centrifugal force developed by the excessively
high velocities at which turbines of this class revolve when steam, or water at
very high pressures, is employed therewith as the motive fluid, without the
said buckets being distorted or twisted thereby; and at same time to so arrange
and combine the interior curvatures of the buckets that the inflow of the jet of
motive fluid thereto shall be subject to a minimum of shock at the time of entry.
into the buckets, and that as the motive fluid passes through the buckets it shall
have a gradually widening surface for its lateral expansion up to the discharging
edges of the buckets, and that the direction of its discharge therefrom shall be
such that a minimum of residual energy shall be left in the escaping fluid.
apex
In carrying out my invention I so construct the periphery of the wheel that its
outer surface gradually diminishes in diameter from the central circumferential
line of same to the two edges rsepectively, and this I preferably effect by making
the outer surface of the periphery of V-shape in axial cross section,
with the
of the V in the central
the
plane, and forming
of the wheel, or of
greatest diaineter
a curve equivalent thereto.
The buckets are of such shape that they mount or fit saddle-like on
the periphery. The inlet for the jet of motive fluid is in the central part of the
width of the buckets; the discharging edges of the buckets are on each side
thereof. The buckets are encircled by two bands or rings (hereinafter called tho
encircling bands) which connect the buckets to one another, while leaving
the central part of their exterior face between these bands uncovered thereby.
The interior face of each bucket is at such an angle to the inflow-
thereon is
ing jet of motive fluid that the impact of the fluid
stantially free from shock. The bucket is preferably shaped with a slight out-
ward curve between the encircling bands, to prevent, to a certain extent, the
motive fluid, on entering the buckets, spreading laterally, until it reaches the
back of the buckets, where it becomes further guided by the interior curvatures
thereof. These curvatures are so arranged that they deflect the current to right
and left towards the discharging edges of the buckets, and that the surface
over which the motive fluid flows when so deflected gradually widens towards the
said discharging edges, and that the eventual discharge of the motive fluid
sub-

page_text: therefrom is in a direction as nearly as practicable opposite to that of the inflow-
ing jet. The discharged fluid has consequently a minimum of residual energy
left in it.
Dated this 12th day of October 1898
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London,
Chartered Patent Agents.
Improvements in impact-wheels or Turbines.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering 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:-
My invention relates to impact wheels or turbines, and more particularly
to the class or type known as l'elton wheels, and the objects, amongst others, of
my invention are to so construct the buckets and the periphery of the wheel
that together they shall combine simplicity and lightness of construction with
sufficient strength to resist the centrifugal force developed by the excessively
high velocities at which turbines of this class revolve when steam, or water at
very high pressures, is employed therewith as the motive fluid, without the
said buckets being distorted or twisted thereby; and at same time to so arrange
and combine the interior curvatures of the buckets that the inflow of the jet of
motive fluid thereto shall be subject to a minimum of shock at the time of entry
into the buckets, and that as the motive fluid passes through the buckets it shall
have a gradually widening surface for its lateral expansion up to the discharging
edges of the buckets, and that the direction of its discharge therefrom shall be
such that a minimum of residual energy shall be left in the escaping fluid.
In carrying out my invention I so construct the periphery of the wheel that its
outer surface gradually diminishes in diameter from the central circumferential
line of same to the two edges respectively, and this I preferably effect by making
the outer surface of the periphery of V-shape in axial cross-section, with the apex
of the V in the central plane, and forming the greatest diameter of the wheel,
or of a curve equivalent thereto. The buckets are of such shape that they mount
or fit saddle-like on the periphery. The inlet for the jet of motive fluid is in
the central part of the width of the buckets; the discharging edges of the buckets
are on each side thereof. The buckets are encircled by two bands or rings
(hereinafter called the encircling bands) which connect the buckets to one another,
while leaving the central part of their exterior face between these bands
uncovered thereby. The interior face of each bucket is at such an angle to the
inflowing jet of motive fluid that the impact of the fluid thereon is substantially
free from shock.
The bucket is formed with what I term a guide duct for the inflowing fluid;
this duct projects outwards between the encircling bands, and is so curved for-
ward towards the inflowing jet of motive fluid, that the edge of the duct which
first meets said jet, is almost in parallel line therewith, and gradually curves
inwards therefrom into the central meeting edge of cup-like concavities on each
side of the bucket. The inflowing jet of motive fluid thus makes contact at its
entry with the inner surface of the bucket, as nearly as possible free from
shock, and thereafter is guided in upon the meeting edges of the two side cup-
like concavities, and is separated to right and left thereby, and flows evenly over 5

page_text: same to their discharging edges which finally throw it back in nearly the oppo-
site direction to that of the jet.
An important feature of the buckets, as compared with those in hitherto
ordinary use, is the said guide duct for the inflowing fluid, whereby the motive
fluid on entering same makes its contact with the bucket, without shock, and is
thereafter so controlled that it does not spread laterally until it reaches the meet-
ing edge of the two side cup-like concavities, whereas in Pelton wheels using
similar right and left concavities when the fluid strikes the inwardly facing
peripheral surface of the bucket, it has a tendency to spread to right and left,
and much of it to consequently pass to the lateral and backward returning
surface of the concavities, and strike same almost at right angles, and therefore
with shock, instead of gliding round same from the central meeting edges.
Owing to the difficulty there is of showing the combination of curvatures by
mechanical drawings I have in the accompanying illustrative drawings shown
the buckets in perspective, from a photograph of an actual working wheel.
In these drawings,
Figure 1 is a perspective elevation of an impact wheel or turbine constructed
according to this invention, the cover on one side of the casing enclosing same
being removed.
Figure 2 is a perspective end view of the wheel on a larger scale.
Figure 3 is a perspective view on a still larger scale of the back of one bucket,
mounted on an axial section of the V shaped periphery of the wheel.
a is the casing in which the turbine revolves; 6 is the spindle revolving in bear-
ing c, on one side of the casing a. On the spindle is mounted the wheel d,
having the outer surface of its periphery of V shape as shown in Figure 3, the
buckets e being mounted saddle-like thereon. For further securing the bucket
on the wheel when it is revolving at very high velocities, the encircling rings
or bands are mounted and secured upon the outer shoulders of the buckets,
as shown in Figure 2. The buckets are also so constructed as to project between
the encircling rings f f as to form the guide ducts g, the sides of which retain
the motive fluid from the nozzle h against lateral expansion, until it reaches the
central meeting edges of the cup-like concavities jj forming the right and left
sides of the bucket. These meeting edges then deflect the motive fluid without
shock around said concavities to the discharging edges thereof, from which it is
ejected in substantially the opposite direction to that of the inflowing jet, with
a minimum of residual energy left in it, when the wheel is revolving at about
half the velocity of the inflowing fluid. The discharged fluid escapes from the
casing through the outlet k.
The axial exterior side of the guide ducts g may be curved slightly outwards,
as shown in Figures 2 and 3, or may be parallel with the axis of the wheel; and
said side ducts may also be projected further forward than shown in the illus-
trations, in advance of the discharging edges of the right and left concavities of
the bucket, in order that the inwardly facing side thereof may be at as slight
an angle as practicable, with the line of the jet, in order, if necessary, that the
fluid may effect contact with the bucket, and be guided into the cup-like con-
cavities, with a minimum of shock.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. In impact wheels of the Pelton wheel type, the combination with a bucket
carrying wheel, of a plurality of buckets carried by said wheel and having each
two cup-like concavities forming respectively the right and left lateral sides of
the bucket, and a central guide-duct projecting outwardly between said con-
cavities, and between encircling bands connecting the buckets to one another on
each side of such duct and engaging the circumferential sides of the buckets
of said concavities, whereby motive fluid employed to drive the wheel may enter

page_text: the buckets through said guide duct, between said bands, and flow around said
concavities interiorly to, and be discharged within the circumference of said
bands.
2. In impact wheels of the Pelton wheel type, the combination with a bucket
carrying wheel, of a plurality of buckets carried thereby each having two cup-
like concavities forming respectively the right and left lateral sides of the bucket
and having the circumferential sides thereof approximately parallel with the
periphery of the carrying wheel and a central guide-duct projecting outwardly
between said concavities and communicating with both of them for receiving the
motive fluid employed to drive the wheel and direct it into said concavities, the
walls of said bucket at the sides of said duct and in the plane of the wheel being
of sufficient depth to control the inflowing motive fluid against lateral expension
until it reaches the central meeting edges of the cup-like concavities, whereby
the entering fluid is directed by the duct to these meeting edges and deflected
by the latter into the right and left sides of the bucket without shock.
3. In impact wheels of the Pelton wheel type, the combination with a bucket
carrying wheel, of a bucket having two cup-like concavities forming respectively
the right and left lateral sides of the bucket, and having central meeting edges
at the bottom thereof, said buckets having their circumferential sides approxi-
mately parallel with the periphery of the carrying wheel and having between said
concavities a central guide-duct leading to the meeting edges of said concavities,
and having outwardly projecting sides in the plane of the wheel and in approxi-
mately circumferential side in advance of the frontal edges of said concavities.
4. In impact wheels of the Pelton wheel type, the combination with a bucket
carrying wheel having a periphery which in axial cross-section is of approxi-
mately V-shape, in combination with buckets carried on the periphery of said
wheel and having inner sides of approximately the shape of such periphery, and
mounted saddle-like upon such periphery of the wheel, said buckets having two
cup-like concavities forming respectively the right and left lateral sides of the
bucket, a central guide-duct leading to said concavities, and outer sides for said
concavities having portions substantially parallel with the axis and also concentric
with the circumference of said carrying wheel, and outer sides for said duct pro-
jecting outwardly beyond the circumference of such portions, and an encircling
band on each side of said guide duct and engaging said portions of the outer
sides of said concavities.
101
1000
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London,
Chartered Patent Agents.