Improvements in Tangential Impulse Turbines or Pelton Wheels."
Year: 1896

page_text: Date of Application, 13th July, 1896
Complete Specification Left, 12th Apr., 1897-Accepted, 10th July, 1897
PROVISIONAL SPECIFICATION.
Improvements in Tangential Impulse Turbines or Pelton Wheels."
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 have reference to the class or type of turbines known as
tangential impulse, or more commonly, as Pelton wheels, which, as hitherto
ordinarily constructed consist of a number of separately made buckets bolted or
otherwise secured upon or around the periphery of a wheel at equal distances apart,
and into which buckets jets of the motive fluid (usually water) employed for driving
same are directed from outside the periphery of the wheel. Turbine wheels of such
construction are not suitable for driving with steam as the motive fluid as their
separately attached buckets are liable to become bent out of proper position or
break away from the wheel, owing to the excessively powerful centrifugal force
developed by the enormously high velocities at which steam propelled turbines must
necessarily revolve when running at efficient working speed; further as there are
open spaces between the buckets, their advancing sides act like fan vanes on the
surrounding atmosphere, and cause a loss in their working efficiency equivalent to
the power absorbed thereby; and the amount of open space that exists between
the buckets also equivalently diminishes the number that can be mounted on the
wheel, again the efficiency of impulse turbines is enhanced by having as many
buckets as possible around the periphery, consistent with the pitch between their
dividing vanes being sufficient to avoid any undue friction in the passage of the
motive fluid through the buckets, and by having the dividing diaphragmns or vanes
as thin as practicable. The objects, (amongst others) of my invention are so to
construct tangential impulse turbines that they may be driven with one or more jets
of steam, vapor, air or gases or of water which may be used at extra high pressures
such as 1000 lbs. and upwards per square inch (hereinafter called the motive fluid)
without danger of the buckets breaking away from the wheel or twisting out of
position thereon; and without the divisional vanes between the buckets operating
with fan action on the surrounding atmosphere to any appreciable extent, while a
maximum number of buckets may be employed around the periphery of the wheel,
in which the dividing vanes are formed of very thin sheet metal.
In constructing my improved impulse turbines, I preferably make the central part
of the wheel (hereinafter called the turbine wheel) either as a disc annulus, mounted
on arms or spokes of a wheel or between a pair of disc diverging at the centre and
there rivetted to a central hub keyed on the turbine shaft; or as a solid disc
similarly mounted on the said shaft or spindle; with a flange or rim around the
periphery of the said dise annulus or solid disc as the case may be, in which rim the
buckets are formed by a combination of one or more circumferential and. suitably
shaped concave grooves (hereinafter called the rim grooves) formed preferably by
turning them in the central part of the outer face of said rim,. with thin sheet metal
vanes or diaphragms (hereinafter called the bucket vanes) inserted as a firm fit into
slits or cuts (hereinafter called cross cuts) incised across its outer face to the bottom

page_text: of said rim groove or grooves, whereby same is divided into a series of buckets; and
I preferably set the bucket vanes at such an angle with the rim of the wheel that
when they come opposite any of the jets of motive fluid driving the turbine, they
are approximately in parallel line therewith and the cross section of the concave
curve in the rim groove is such that the line of junction between it and the bucket
vanes inserted across the same forms axially directed semi-circular or semi-elliptical
curvatures which constitute the back of the buckets, and round which the path of the
motive fluid is directed in passing through the buckets. The diameter of this
curvature I preferably make equal to about four to six times the diameter of the jet
of motive fluid at the time of its entry thereto, in practice, however, commencing
with a minimum diameter of at least half an inch for the smallest sizes of jets used
therewith. The distance apart between the bucket vanes constitutes the pitch or
length of the bucket as measured round the rim, and this length I preferably adjust
so that the clear width of entrance for the jets of motive fluid between the bucket
vanes is equal to about one half the cross sectional diameter of the motive fluid jets
at the time of their entry into the buckets in practice, however, commencing with a
minimum space of at least one-eighth of an inch between the bucket vanes for the
smallest sizes of jets of motive fluid used therewith. I may also alternatively
construct my herein described improved impulse turbines with two of said rim
grooves so located side by side in the rim that when each is turned out to its proper
concave curvature in the outer face of the wheel rim, their curves meet or cut into
one another at their inner edges whereby a sharp wedge-like projection is formed
between them and which edge is preferably a little below the exposed edge of the
bucket vanes when inserted as hereinbefore described across the double groove thus
formed. The jets of motive fluid on being directed upon the said sharp wedge-like
dividing edge between the grooves are split thereby to right and left into the
axially directed curvatures forming the back of the buckets in each of the rim
grooves, so that a double acting bucket is formed by this combination of double rim
grooves with the bucket vanes; from which the return current of the motive fluid is
discharged outwardly in approximately equal parts from its opposite ends; and on
the marginal edges of the said rim grooves a sufficient width of the wheel rim is left
flat for a metal ring to be shrunk on over it, with or without the addition of a coil of
wire wound tightly into a groove round it, so as to bind the bucket vanes and the
divided parts of the rim between them, sufficiently firmly and strongly together to
withstand the centrifugal force developed by the enormously high velocities at which
these turbines necessarily revolve when working with steam or with high pressure
hydraulic jets of about 1000 lbs. and upwards as motive fluid.
According to an alternative modification in the construction of the buckets in my
improved impulse turbines, instead of turning out the rim groove or grooves forming
the axially directed back curvatures of the buckets as a continuous concave groove
around the outer face of the wheel rim, whereby the circumferential line of the same
is at an acute angle to the face-of-the-bucket vanes, and an obtuse angle to the
back thereof, I form the axially directed back curvature of the buckets substantially
at right angles to the back of each bucket vane, by substituting for the said
continuous rim grooves a series of equidistant (and preferably milled out) semi-
cylindrical faced steps round the central part of the exterior face of the rim, each of
which steps is of a depth equal to about one-half the diameter of the jet of motive
fluid employed with the same at the time of its entry into the buckets, but in
practice commencing with a minimum of at least one-eighth of an inch for the
smallest jets used therewith; in front of each step there is a flat plane the line of
which is at such an angle with the rim of the wheel that it is approximately parallel
with that of the jets of motive fluid when opposite the same, so that the said jets
may impinge direct into the upright concave curvature formed by the
semi-cylindrical face of each step, without any material deflection thereof by said
plane, upon the face of which a thin sheet metal vane is closely fitted by inserting
it into cross cuts incised across the face of the rim from edge to edge, in corresponding
line with said planes, and extended sufficiently back past the face of each step for

page_text: one inserted edge of the vane to be quite covered thereby. I preferably form the
back concave curvatures of each step in pairs located sufficiently closely together that
their inner curves meet in a sharp wedge-like projection, whereby double return
buckets are formed between each pair of vanes similar to those hereinbefore referred
5 to, and the outer ends of the vanes and the divided parts of the rim between.chem
are also similarly bound in firmly together by shrunk on metal rings with or without
the addition of a coil of wire wound tightly into a groove round it.
In either of the above described modifications in the construction of the buckets,
it will be evident that as there is no interior or side entrance for the surrounding
atmosphere to get into or between the buckets, there can consequently be no free
discharge of air therefrom, and the vanes being sloped backwards from the direction
in which the wheel is running, have a minimum fan action upon any air that may
be drawn in as an eddy over the edges of the wheel rim, and as only a very small
volume of air could get at the vanes by such eddies, this form of bucket has
practically no fan action to reduce its efficiency in work.
that as the path of the motive fluid through the buckets is deflected round a
It will also be obvious
semi-circular or semi-elliptical curvature it necessarily returns therefrom in a line
practically parallel with and in opposite direction to that of the initial flow of the jet
provided the turbine is held stationary, but when it is working at its most efficient
speed the bucket of course noves away from its position between the time that the
jet first enters it and its return therefrom, consequently the angle of the return
current must necessarily open outwards to some extent, so that its return is not
altogether parallel with that of its initial flow. But as the thin sheet metal bucket
vanes in either form of construction above described can with facility be efficiently
and securely inserted at very short distances apart, and as the semi-circular curvature
round which the motive fluid passes is also very short, its return out of the buckets
takes place so quickly that the buckets have not time to move so far forward that the
angle of the return
initial flow, to such an extent as to materially reduce its operative efficiency and as
flow can open outwardly from a parallel line with its
my herein described improved turbines may be driven by jets of steam or by extra
high pressure hydraulic jets, delivered from nozzles exterior to their periphery into
buckets formed on the exterior face of their rims by the combination of concave
grooves or curvatures therein with thin sheet metal dividing vanes or diaphragms
nserted across the same, and bound so rigidly therein that they are capable of
withstanding the enormous centrifugal force developed when they are revolving at
fficient working speed, they may appropriately be termed Extra Impulse
urbines.
It will be obvious that if more power be desired from a given diameter of
arbine wheel that can be obtained by multiplying the jets of motive fluid, two
eparate sets of rim grooves and buckets may be constructed on the one wheel.
It will also be obvious that when my improved extra impulse turbines are required
impart motion in reverse directions, as in the case of their employment for
iving locomotives or steamships, two wheels may be mounted on the one shaft, and
e vanes inserted therein at opposite angles to one another and the motive fluid
ts arranged to act thereon in opposite directions.
Dated this 13th day of July 1806
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.

page_text: ощение и дандон трио лигощен от генов wпесть.
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 improvements have reference to the class or type of turbines known as tangen-
tial impulse, or more commonly as pelton wheels, which, as hitherto ordinarily
constructed consist of a number of separately inade buckets bolted or otherwise secured
upon or around the periphery of a wheel at equal distances apart, and into which
bucket jets of the motive fluid (usually water) employed for driving same are directed
from outside the periphery of the wheel. Turbine wheels of such construction are
not suitable for driving with steam as the motive fluid as their separately attached
buckets are liable to bocome bent out of proper position or break away from the wheel
owing to the excessively powerful centrifugal force developed by the enormously high
velocities at which steam propelled turbines must necessarily revolve when running
at efficient working speed; further, as there are open spaces between the buckets, their
advancing sides act like fan vanes on the surrounding atmosphere, and cause a loss in
their working efficiency equivalent to the power absorbed thereby; and the amount
of open space that exists between the buckets also equivalently diminishes the number
that can be mounted on the wheel; again the efficiency of impulse turbines is
enhanced by having as many buckets as possible around the periphery consistent
with the pitch between their dividing vanes being sufficient to avoid any undue
friction in the passage of the motive fluid through the buckets, and by having the
dividing diaphragms or vanes as thin as practicable. The objects (among others) of
iny invention are to so construet tangential impulse turbines, that they may be
driven with one or more jets of steam, vapour, air or gases, or of water, which may be
used at extra high pressures such as 1,000 lbs. and upwards per square inch (herein-
after called the motive fluid) without danger of the buckets breaking away from the
wheel or twisting out of position thereon; and without the divisional vanes
between the buckets operating with fan action on the surrounding atmosphere to
any appreciable extent, while a maximum number of buckets may be employed
around the periphery of the wheel in which the dividing vanes are formed of very
thin sheet metal.
on arms
In constructing my improved impulse turbines, I preferably make the central part
of the wheel (hereinafter called the turbine wheel) either as a disc annulus, mounted
or spokes of a wheel or between a pair of discs diverging at the centre and
there rivetted to a central hub keyed on the turbine shaft; or as a solid disc
similarly mounted on the said shaft or spindle; with a flange or rim around the
periphery of the said disc-annulus or solid disc as the case may be, in which rim the
buckets are formed by a combination of one or more circumferential and suitably
shaped concave grooves (hereinafter called the rim grooves) formed preferably by
turning them in the central part of the outer face of said rim with thin sheet metal
vanes or diaphragms (hereinafter called the bucket vanes) inserted as a firm fit into
slits or cuts (hereinafter called cross cut incised across its outer face to the bottom of
said rim groove or grooves, whereby same is divided into a series of buckets; and I
preferably set the bucket vanes at such an angle with the rim of the wheel that when
they come opposite any of the jets of motive fluid driving the turbine they are approxi-
mately in parallel line therewith and the cross section of the concave curve in the
rim groove is such that the line of junction between it and the bucket vanes inserted

page_text: тапу
constitute the back of the buckets and round which the path of the motive fluid is
rected semi-circular or semi-elliptical curvatures which
directed in passing through the buckets. The diameter of this curvature I preferably
make equal to about four to six times the diameter of the jet of motive fluid at the
5 time of its entry thereto, in practice however commencing with a minimum diameter
of at least half an inch for the smallest sizes of jets used therewith. The distance
apart between the bucket vanes constitutes the pitch or length of the bucket as
measured round the rim, and this length I preferably adjust so that the clear width
of entrance for the jets of motive fluid between the bucket vanes is equal to about one-
0 half the cross sectional diameter of the motive fluid jets at the time of their entry
into the buckets, in practice, however, commencing with a minimum space of at
least one-eighth of an inch between the bucket vanes for the sin allest sizes of jets of
motive fluid used therewith. I may also alternatively construct my herein described
improved impulse turbines with two of said rim grooves so located side by side in
5 the rim that when each is turned out to its proper concave curvature in the outer face
of the wheel rim, their curves meet to cut into one another at their inner edges,
whereby a sharp wedge-like projection is formed between them and which edge is
preferably a little below the exposed edge of the bucket vanes when inserted as herein-
before described across the double groove thus formed. The jets of motive upon being
directed upon the said sharp wedge-like dividing edge between the grooves, are split
thereby to right and left into the axially directed curvatures forming the back of the
buckets in each of the rim grooves, so that a double acting bucket is formed by this
combination of double rim grooves with the bucket vanes, from which the return
current of the motive fluid is discharged outwardly in approximately equal parts from
its opposite ends; and on the marginal edges of the said rin grooves a sufficient width
of the wheel rim is left flat for a metal rim to be shrunk on over it, with or without
the addition of a coil of wire wound tightly into a groove round it, so as to bind the
bucket vanes and the divided parts of the rim between them, sufficiently firmly and
strongly together to withstand the centrifugal force developed by the enormously high
velocities at which these turbines necessarily revolve when working with steam
or high pressure hydraulic jets of about 1,000 lbs. and upwards as motive
fluid.
According to another alternative modification in the construction of the buckets in
my improved impulse turbines instead of turning out the rim groove or grooves
forming the axially directed back curvatures of the buckets as a continuous concave
groove round the outer face of the wheel rim, whereby the circumferential line of the
same is at an acute angle to the face of the bucket vanes and an obtuse angle to the
back thereof, I form the axially directed back curvature of the buckets substantially at
right angles to the back of each bucket vane, by substituting for the said continuous
rim grooves a series of equidistant (and preferably milled out) semi-cylindrical faced
steps round the central part of the exterior face of the rim, each of which steps is of a
depth equal to about.one-half the diameter of the jet of motive fluid employed with
the same at the time of its entry into the buckets, but in practice commencing with
minimum of at least one eighth of an inch for the smallest jets used therewith; in
front of each step there is a flat plane the line of which is at an angle with the rim of
he wheel that it is approximately parallel with that of the jets of motive fluid, when
pposite the same, so that the said jets may impinge direct into the upright concave
urvature formed by the semi-cylindrical face of each step without any material
leflection thereof, by said plane, upon the face of which a thin sheet metal vane is
losely fitted by inserting it into cross-cuts incised across the face of the rim from
dge to edge, in corresponding line with said planes, and extended sufficiently back
ast the face of each step for the inserted edge of the vane to be quite covered thereby.
may also alternatively form the back concave curvatures of each step in pairs located
afficiently closely together that their inner curves meet in a sharp wedge-like pro-
etion, whereby double return buckets are formed between each pair of vanes similar
those hereinbefore referred to, and the outer ends of the vanes and the divided parts
the rim between them are also similarly bound in firmly together by shrunk on

page_text: metal rings with or without the addition of a coil of wire wound tightly into a groove
round it..
In any of the above described inodifications in the construction of the buckets it
will be evident that as there is no interior or side entrance for the surrounding atmos
phere to get into or between the buckets, there can consequently be no free discharge
of air therefrom, and the vanes being sloped backwards from the direction in which
the wheel is running, have a minimum fan action upon any air that may be drawn
in as an eddy over the edges of the wheel rim, and as only a very small volume of air
could get at the vanes by such eddies, this form of bucket has practically no fan
action to reduce its efficiency in work. It will also be obvious that as the path of the
motive fluid through the buckets is deflected round a semi-circular or semi-elliptical
curvature, it necessarily returns therefrom in a line practically parallel with and in
opposite direction to that of the initial flow of the jet, provided the turbine is held
stationary, but when it is working at its most efficient speed the bucket of course
moves away from its position between the time that the jet first enters it and its
return therefrom; consequently the angle of the return current must necessarily open
outwards to some extent, so that its return is not altogether parallel with that of its
initial flow. But as the thin sheet metal bucket vanes in any of the forms. of con-
struction above described can with facility be efficiently and securely inserted at very
short distances apart, and as the semi-circular curvature round which the motive fluid
passes is also very short, its return out of the buckets takes place so quickly that the
buckets have not time to move so far forward that the angle of the return flow can
open outwardly from a parallel line with its initial flow to such an extent as to
materially reduce its operative efficiency, and as my hereindescribed improved turbines
may be driven by jets of steam or by extra high pressure hydraulic jets, delivered from
nozzles exterior to their periphery, into buckets formed on the exterior face of their
rims by the combination of concave grooves or curvatures therein with thin sheet
metal dividing vanes or diaphragins inserted neross the same, and bound so rigidly
therein that they are capable of withstanding the enormous centrifugal force developed
when they are revolving at efficient working speed, they may appropriately be
termed Extra-impulse Turbines.
It will be obvious that if more power be desired from a given diameter of
turbine wheel than can be obtained by multiplying the jets of motive fluid,
two separate sets of rim grooves and buckets may be constructed on the one
wheel.
It will also he obvious that when my improved extra impulse turbines are required
to impart motion in reverse directions, as in the case of their employment for driving
locomotives or steamships, two wheels may be mounted on the one shaft, and the
vanes inserted therein at opposite angles to one another, and the motive fluid jets
arranged to act thereon in opposite directions.
In the accompanying drawings :-
Figure 1 is a side elevation and
Figure 2 a cross section on the line-z-z-of Figure 1 of a turbine constructed
according to one modification of my invention in which two adjoining and intersecting
circumferential rim grooves form, in conjunction with vanes inserted therein, double-
acting buckets in circnit around the wheel.
Figure 3 is à longitudinal section on line y y of Figure 2.
Figure 4 is a plan;
Figure 5 is a sectional elevation on line x of Figure 6 and
Figure 6 a half cross-section and half elevation of a turbine constructed according
to another modification in which two intersecting concave curves are milled out
in the face of each of a successive series of steps around the outer face of the
rim annulus and form the buckets in conjunction with inserted vanes between each
-step.
Figure 7 is a half cross-section of another modification in which there is one
single circumferential rim groove forming the buckets; and a groove or channel

page_text: formed in the outer circumference of the two shrunk on metal rings, into which coils
of wire are wound to give the rings greater tensile strength.
Figure 8 is a half cross-section of another modification in which there are
two independent sets of single circumferential rim grooves and sets of buckets,
so that with double nozzles twice the power may be developed on the wheel.
Figure 9 is a half cross section of another modification in which there are two
independent sets of double circumferential rim grooves and sets of buckets for use
with double nozzles.
Referring first to Figures 1 to 4, A is the turbine wheel, B the disc annulus and
CC the circumferential grooves therein; D D are the vanes inserted across the
grooves C C thereby forming the buckets. E and E are the dished plates and F
the hub of the wheel which is keyed or otherwise secured to the spindle G.
shrunk on rings. I is the nozzle for the jet of motive fluid and K the supply pipe
for same. L is the casing for the turbine with inspection doors M fitted with plate
glass. N is the waste motive fluid outlet from the casing. O is the bedplate with
ball bearings P P mounted thereon. R is the driving pulley.
In Figures 5 and 6, A is the turbine wheel, B the dise annulus with milled-out
concave semi-circular faced steps C C; and D the vanes inserted across same.
E and E are the dished plates and F the hub of the wheel; H H the shrunk-on
rings.
In Figures 7, 8 and 9, A is the turbine wheel, B the dise annulus with circumferen-
tial rim grooves CC; D D the vanes across same forming the buckets. E and E¹ are
the dished plates and F the hub of the wheel the shrunk-on rings. In
Figure 7 G G are the coils of wire wound into the channel formed in the shrunk-on
rings H H.
It is also intended that in the modifications shown in Figures 7, 8 and 9 the back
curvatures may if desired be alternatively formed according to the way represented in
Figures 5 and 6.
In the accompanying drawings, as above described, only one jet nozzle is illustrated
for directing the motive fluid into the buckets of the turbine wheel, and from a point
in the outer casing which is in line with the plane of revolution of the turbine, but
more than one may be applied in a similar manner, or the jets may be led from a
motive fluid supply duct attached to or forming part of the side of the turbine casing,
as may be preferred, and which latter arrangement is shown and described in the
Specification filed in connection with my application for Letters Patent relating to
the governing of turbines, the said application being of equal date herewith and
numbered 15501.
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 tangential impulse turbines in which the initial flow of the motive fluid.
driving the same is directed into the buckets from one or more jet nozzles exterior to
the periphery of the turbine wheel, the combination with the body of the turbine
wheel of a flanged rim revolving therewith, an axially directed approximately semi-
circular circumferential groove in the outer periphery of said rim, thin sheet metal
vanes dividing said groove into buckets, said vanes being inserted into transversely
incised slits across the face of said rim to the full depth of said groove at such an
angle to the periphery of the wheel that when said vanes come opposite the jets of
motive fluid driving the turbine they are approximately in parallel line therewith,
and a band around said rim compressing and holding together the said vanes
and the divided portions of the said rim, substantially as and for the purpose
set forth.
2. In tangential impulse turbines in which the initial flow of the motive fluid
driving the same is directed into the buckets from one or more jet nozzles exterior to
the periphery of the turbine wheel and in which the turbine wheel has a flanged rim
with an axially directed circumferential concave groove of approximately semi-circular

page_text: cross section in its outer periphery as and for the purpose set forth, the combination
with said rim and its said circumferential groove of a second similar groove in said
rim parallel with the first described groove and in sufficiently close proximity to it
that their curves meet in a sharp edge and form a wedge-like projection between the
two grooves, and thin sheet metal vanes dividing both of said grooves into buckets,
said vanes being inserted across said grooves into slits cut transversely across said rim
to the full depth of said grooves and at an angle as described whereby when the jets.
of motive fluid are directed upon the edge between the two grooves, said edge divides
it between the two grooves and it is discharged from the opposite ends of the double
buckets thereby formed in a line approximately parallel with and in opposite direction
to that of its initial flow, and a band around said rin compressing and holding together
the said vanes and the divided portions of said rim, substantially as and for the
purpose set forth.
3. In tangential impulse turbines in which the initial flow of the motive fluid
driving the same is directed into the buckets from one or more jet nozzles exterior to
the periphery of the turbine wheel, the combination with the body of the turbine
wheel of a flanged rim revolving therewith, a successive series of semi-cylindrical
concave faced steps around the outer periphery of said rim, the concave face of each
step forming a back curvature thereof, and each of which steps is at right angles to
the line of motive fluid when opposite same, thin sheet metal vanes inserted into
transverse cuts across the face of said rim and dividing the concave faced steps
therewith constituting buckets, the said vanes coming into approximately parallel
line with the jets when opposite the same, whereby the motive fluid is deflected
around the concave face of each step in its traverse through the bucket, and is
discharged in a line approximately parallel with and in opposite direction to
that of its initial flow, and a band around said rim compressing and holding
together the divided portions of said rim, substantially as and for the purpose set
forth.
4. The several combinations of parts of tangential impulse turbines or pelton wheels
substantially as herein before described and shown in the drawings.
Dated this 12th day of April 1897
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.