Improvements in the Construction of Impulse Turbines.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Construction of Impulse 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 have reference to impulse turbines, and especially to the
construction of the wheels of those of the axial, or combined inward and axial
flow type, wherein the energy of the motive fluid employed to drive the turbine
is transferred to torque at the circumference of the wheel by the impulsive
action of a jet of said fluid on a succession of vanes or buckets (hereinafter
referred to as the buckets) arranged equidistant around its circumference.
In the construction of these wheels, it is important that the weight of the
wheel, and more particularly its rim, should be as light as possible, consistent
with the maintenance of the requisite strength and width of face on the rim
for mounting the buckets thereon, as the enormously high peripheral veloci-
ties at which turbines of this type revolve, when driven by water at very high
pressures or by steam, develop such a high centrifugal force that it is essential
to keep the weight of the wheel as low as practicable, to minimise the outward
pressure due to said centrifugal force, while at same time maintaining suilcient
strength of construction to transmit the torque communicated to the buckets
through the rim and spokes to the shaft or spindle of the turbine; and the
principal objects of the present invention are to construct the wheels so as to
combine lightness in weight, with ample strength of construction, while retain-
ing sufficient width of face on the rim for securely mounting the base, of each
bucket thereon.
a
In the construction of my improved turbine wheels, I employ light wire or
other spokes between the hub and the rim, which are applied thereon in sub-
stantially the same way as in bicycle wheels, that is to say the rim is held to
the hub by the spokes acting in tensile strain between the rim and
as
is connected
each end of the hub, which
fixture to the shaft,
but with the rim made as a hollow metal tube (hereinafter referred to as the
tubular rim) with the outer face either flat or bevelled from a central projecting
apex around the same to its edges, so as to fit evenly against the inner face of
the base of the buckets, which are mounted as saddles thereon. Or I may
alternatively make the tubular rim in two parts, the inner one being convex on
its inner face and concave on its outer face, similar to the rim of an ordinary
bicycle wheel in which the outer face is constructed to hold the tyre, and the
method of attachment of this part of the rim to the spokes being likewise
similar and I make the other and outer part of the tubular rim to evenly fit
against the base or inner faces of the buckets, and accurately fit upon and bridge
over from side to side the outer and concave face of the inner part, and I attach
the buckets thereto before or after applying it upon the inner part. When the
outer part has to be expanded so as to get it over the inner part, I preferably
sever the circle of the outer part, which enables it to be sprung into whatever
position is necessary upon the inner part, and then braize, solder, or otherwise

page_text: securely attach the several ends, and also the edges of the outer and inner
parts together.
When I make the tubular rim in one part as a tube throughout, the outer
ends of the spokes from the hub pass through holes in the inner face thereof,
and are adjusted and secured by suitable nuts on the inner face of the tube
through holes in its exterior face, and the buckets are brazed and soldered over
these holes, whereby the base of the buckets closes them, so that in this modifi-
cation, as well as in that in which the rim is constructed in two parts, neither
water nor condensed steam can penetrate the interior of the tubular rim. This
is important as the additional weight of this water would increase the outward
pressure due to centrifugal force, and counteract the advantages gained by the
structural lightness of the rim itself, the tubular formation of which gives it
great strength and stiffness.
Turbine wheels when constructed in accordance with my invention, can be
made of very large diameter, so that when driven by jets of water at very high
pressure, or with steam, a low speed of revolution of the shaft can be directly
obtained without any intermediate or gearing down appliances; whereas in tur-
bines of this type as hitherto constructed, it has been found in practice that a
wheel of G ft. diameter was about the maximum size that could be safely
employed, even when the water pressure on the jets employed did not exceed
about 150 lbs. to the square inch. But in turbines constructed in accordance
with my invention, the wheels can be made of much greater diameter when
desirable, and can be safely worked with water pressures up to as much as
500 lbs. per square inch, while small size wheels of this construction can owing
to their lightness be efficiently driven with very small jets and very low
pressures of water, such as are ordinarily obtainable from the house water
supply mains in towns, which frequently do not exceed a pressure of more than
20 or 30 lbs. to the square inch. My improved turbines of small size are
thus useful as domestic motors for light drives such as sewing machines &c. or
for ventilating fans.
Dat thin fil
1
1
1000
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.
Improvements in the Construction of Impulse 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 improvements have reference to impulse turbines, and especially to the
construction of the wheels of those of the axial, or combined inward and axial
flow type, wherein the energy of the motive fluid employed to drive the turbine
is transferred to torque at the circumference of the wheel by the impulsive
action of a jet of said fluid on a succession of vanes or buckets (hereinafter
referred to as the buckets) arranged equidistant around its circumference.
In the construction of these wheels, it is important that the weight of the
wheel, and more particularly its rim, should be as light as possible, consistent
with the maintenance of the requisite strength and width of face on the rim
for mounting the buckets thereon, as the enormously high peripheral veloci-

page_text: ties at which turbines of this type revolve, when driven by water at very high
pressures or by steam, develop such a high centrifugal force that it is essential
to keep the weight of the wheel as low as practicable, to minimise the outward
pressure due to said centrifugal force, while at same time maintaining sufficient
strength of construction to transmit the torque communicated to the buckets
through the rim and spokes to the shaft or spindle of the turbine; and the
principal objects of the present invention are to construct the wheels so as to
combine lightness in weight, with ample strength of construction, while retain-
ing sufficient width of face on the rim for securely mounting the base of each
bucket thereon.
In the construction of my improved turbine wheels, I employ light wire or
other spokes between the hub and the rim, which are applied thereon in sub-
stantially the same way as in bicycle wheels, that is to say the rim is held to
the hub by the spokes acting in tensile strain between the rim and
each end of the hub, which is connected as a fixture to the shaft,
but with the rim made as a hollow metal tube (hereinafter referred to as the
tubular rim) with the outer face either flat or bevelled from a central projecting
apex around the same to its edges, so as to fit evenly against the inner face of
the base of the buckets, which are mounted as saddles thereon. Or I may
alternatively make the tubular rim in two parts, the inner one being convex on
its inner face and concave on its outer face, similar to the rim of an ordinary
bicycle wheel in which the outer face is constructed to hold the tyre, and the
method of attachment of this part of the rim to the spokes being likewise
similar and I make the other and outer part of the tubular rim to evenly fit
against the base or inner faces of the buckets, and accurately fit upon and bridge
over from side to side the outer and concave face of the inner part, and I attach
the buckets thereto before or after applying it upon the inner part. When the
outer part has to be expanded so as to get it over the inner part, I preferably
sever the circle of the outer part, which enables it to be sprung into whatever
position is necessary upon the inner part, and then braize, solder, or otherwise
securely attach the several ends, and also the edges of the outer and inner
parts together.
When I make the tubular rim in one part as a tube throughout, the outer
ends of the spokes from the hub pass through holes in the inner face thereof,
and are adjusted and secured by suitable nuts on the inner face of the tube
through holes in its exterior face, and the buckets are brazed and soldered over
these holes, whereby the base of the buckets closes them, so that in this modifi-
cation, as well as in that in which the rim is constructed in two parts, neither
water nor condensed steam can penetrate the interior of the tubular rim. This
is important as the additional weight of this water would increase the outward
pressure due to centrifugal force, and counteract the advantages gained by the
structural lightness of the rim itself, the tubular formation of which gives it
great strength and stiffness.
Turbine wheels when constructed in accordance with my invention, can be
made of very large diameter, so that when driven by jets of water at very high
pressure, or with steam, a low speed of revolution of the shaft can be directly
obtained without any intermediate or gearing down appliances; whereas in tur-
bines of this type as hitherto constructed, it has been found in practice that a
wheel of six ft. diameter was about the maximum size that could be safely
employed, even when the water pressure on the jets employed did not exceed
about 150 lbs. to the square inch. But in turbines constructed in accordance
with my invention, the wheels can be made of much greater diameter when
desirable and can be safely worked with water pressures up to as much as
500 lbs. per square inch, while small size wheels of this construction can owing
to their lightness be efficiently driven with very small jets and
very low
pressures of water, such as are ordinarily obtainable from the house water
supply mains in towns, which frequently do not exceed a pressure of more than

page_text: 20 or 30 lbs. to the square inch. My improved turbines of small size are
thus useful as domestic motors for light drives such as sewing machines &c. or
for ventilating fans.
Reference to the accompanying drawings will more fully illustrate how my
invention can be carried into effect.
Figure 1 is a front elevation of my improved turbine wheel.
Figure 2 is a section on line X-X of Figure 1.
Figure 3 is an elevation on a larger scale showing a portion of the rim when
made in two parts.
Figure 4 is a section on line Y-Y of Figure 3.
Figure 5 is an elevation on the same scale as Figure 3 showing a portion of
the rim when made in one part as a hollow metal tube.
Figure 6 is a section on line Z-Z of Figure 5.
Figure 7 is a plan showing part of the rim when made as a hollow metal tube
before the buckets are mounted thereon.
A is the spindle or shaft upon which the hub B is mounted, the rim C being
secured thereto by means of spokes D) acting in tensile strain between the rim C
and each end of the hub B. The rim may be made with the outer face flat,
but in the accompanying drawings it is shown bevelled from a central project-
ing apex around the same to its edges so as to fit the inner face of the base of
the buckets E. When the rim is made in two parts as shown in Figures
and 4, the outer ends of the spokes D) from the hub B pass through holes in
the inner face of the rim C and are adjusted and secured by nuts before the
outer portion of the rim (indicated by letter G) is put on.
The outer rim G
having to be expanded so as to get it over the inner rim C, I preferably sever
the outer rim G so as to spring it into its necessary position on the rim C then
braze, solder or otherwise securely attach the several ends and also the edges of
the outer rim G and the inner rim C together. When the rim is made in
one part throughout as shown in Figures 5, 6 and 7 the outer ends of the
spokes D from the hub B pass through holes in the inner face of the rim Cand
are adjusted and secured by nuts through the holes H in its exterior face.
The buckets E are then brazed and soldered over the holes H entirely closing
them so as to prevent any water or condensed steam getting into the interior of
the tubular iim C. For further securing the buckets on the wheel when it
is revolving at very high velocities the encircling rings or bands J J are
mounted and secured on the outer shoulders of the buckets E as shown.
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 impulse turbines a wheel having light wire or other spokes acting in
tensile strain between the hub and the rim, the said rim being tubular and
having its outer periphery so shaped as to fit against the base or inner face of
the buckets, substantially as and for the purpose herein before described.
2. The construction of the wheels of impulse turbines, substantially as here-
inbefore described with reference to Figures 1 to 4.
3. The construction of the wheels of impulse turbines, substantially as here-
in before described with reference to Figures 5, 6 and 7.
Dated thin 17th D 1900
T. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.