IMPROVEMENTS IN STEAM ENGINES
Year: 1853

page_text: LETTERS PATENT to William Todd, of Rochdale, in the County
of Lancaster, Engineer, for the Invention of "IMPROVEMENTS IN
STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said William Todd at
the Office of the Commissioners of Patents, with his Petition, on
the 5th March 1853.
14.1
I, WILLIAM TODD, of Rochdale, in the County of Lancaster,
Engineer,, do hereby declare the nature of the said Invention for "IM-
PROVEMENTS IN STEAM ENGINES" to be as follows:-
My improvements relate, firstly, to a method of communicating the
motion of the governor" to the throttle valve, or other apparatus used
for regulating the flow. of steam into the cylinder of the engine, and
consist in the employment of a toothed wheel or wheels, or other rotatory
surface or surfaces, as the connecting part or parts. Thus, for instance,
I cause the expansion and contraction of the governor balls to impart
rotatory motion to a shaft, upon the axle of which there is a worm pinion,
taking into the teeth of a worm wheel or are: upon the axis of this
I attach the throttle valve, which is thereby caused to turn upon its

page_text: centre, so as to open or contract the steam way. Instead of the worm
and wheel or sector, other toothed gearing or friction surfaces may be
substituted, and valves of any ordinary construction may be employed.
Instead also of employing two rotatory surfaces one only may be used;
thus, for instance, in place of the worm wheel or sector above men-
tioned, I adapt a rack connected to the valve used for regulating the
flow of steam: Secondly, in a method of causing the action of the
governor to operate upon a valve, so as to admit air to the vacuum side
of low-pressure engines, for the purpose of arresting the motion of the
same when an excessive velocity has been attained. To accomplish this
I employ the rotatory surface or surfaces before mentioned; and, sup-
posing the arrangement thereof to be that above described, I connect
the worm wheel to the throttle or other valve by means of a friction
clutch upon the said valve; therefore, being perfectly closed, the pinion
will still cause the wheel to revolve, slipping, however, upon its friction
clutch. This further revolution causes a projection to arrive in contact
with suitable apparatus for opening the valve connected with the
vacuum side of the piston.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Todd, in the Great Seal Patent Office,
on the Sd September 1858.
I,
TO ALL TO WHOM THESE PRESENTS SHALL COME, I.
WILLIAM TODD, of Rochdale, in the County of Lancaster, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of March, in the year of our
Lord One thousand eight hundred and fifty-three, in the sixteenth year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said William Todd, Her especial licence that I, the
said William Todd, my axocutors, administrators, and assigns, should
at any time agree with; and no others, from time to time and at all
tinues thereafter during the term therein expressed, should' and law-

page_text: fully might make, use, exercise, and vend, within the United Kingdom
of Great Britain and Ireland, the Channel Islands, and Isle of Man,
an Invention for "IMPROVEMENTS IN STEAM ENGINES," upon the condition
(amongst others) that I, the said William Todd, by an instrument in
writing under my hand and seal, should particularly describe and ascer-
tain the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said William Todd, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement and accompanying drawing (that is to say):
My improvements relate, firstly, to a method of communicating the
motion of the governor to the throttle valve or other apparatus used
for regulating the flow of steam into the cylinder of the engine, and
consist in the employment of a wheel or wheels or other rotatory surface
or surfaces, as the connecting part or parts, instead of the system of
levers usually adopted. Secondly, in a method of causing the action of
the governor to operate upon a valve, so as to admit air to the vacuum
side of low-pressure engines, for the purpose of arresting the motion of
the same when an excessive velocity has been attained; to accomplish
which I employ the rotatory surface or surfaces before mentioned.
The construction and arrangement of parts necessary for carrying out
my invention may be varied to a considerable extent by different appli-
cations of worms or wheels: I have, however, in the accompanying draw-
ing, shewn the apparatus which I prefer, and which I will now proceed
to describe. The governor a, is connected to a shaft b, by means of two
bevil wheels or friction surfaces, as ordinarily practised. At the end of
the shaft b; is mounted a conical surface c, upon which a spiral channel
is cut, the thread thus formed being quicker at the outward end thereof.
The centre of motion of the throttle valve is at d, to which is affixed a
lever e, the outward end thereof being provided with a tooth, which
takes into the thread of the worm c: upon the governor balls therefore ex-
panding or contracting, the shaft b, being caused to revolve the one way

page_text: or the other, will traverse the lever e, backward or forward within the
thread of the conical rotatory surface c, thus turning the throttle valve
upon its centre, and contracting or enlarging the steam way. My object
in varying the pitch of the spiral thread of the worm is, to obtain con-
stantly an area for the passage of steam proportionate to the work which
the engine has to perform. In order to explain this, I will suppose
that an ordinary butterfly throttle valve is in the position shown by the
dotted line: the contracting action of the governor, by moving the tooth
of the lever c, along the spiral c, will turn the valve in the direction of
the arrow; but as the motion thereof in that direction through a given
arc would open an area greater than a second are of a similar number
of degrees would produce, the slowest part of the worm is first brought
into action, gradually increasing as it becomes necessary to move the
valve through a greater space, in order to maintain the correct area;
and as the governor at the same time causes the worm to revolve more
slowly or quickly, the speed of the engine will be regulated according
to the work it has to perform. The necessary variation of speed in the
worm thread will of course depend upon the shape of the throttle valve,
and must be suited thereto, for a disc constituting the valve will open
different areas for a given rotation upon its axis, according to the angle
at which it is made to correspond to a section of the steam pipe. To
the ordinary blowing through valve f, I apply a valve g, connected to
a lever h, and from thence through rods and levers i, to a rocking lever
j, situate, during the ordinary working of the engine, just clear of a
worm, mounted upon the shaft b. The lever j, has a slot in its upper
part, the lower edge thereof being bevilled, so as readily to take into the
worm, when pushed forward against its surface. Suppose the lever e
to be situate at any part of the worm c, and that a considerable load
should suddenly be taken from the engine, the lever e, will, as before
mentioned, be drawn towards the position shewn in the drawing, and the
steam will be shut off'; but as the momentum of the engine in extreme
cases may not be immediately arrested, the lever e, will be carried suffi-
ciently forward to cause a spring 1, with which it is provided, to arrive
in contact with the lever j, by the medium of which spring the said
lever will be pushed forward, so as to place the edge of its slot into

page_text: gear with the worm k, which, being driven by the engine, will cause the
lever j, to be drawn forward and turned upon its centre, and, through
the intervention of the rods and levers i, open the valve g, and admit air
to the interior of the condenser.
I have described above the particular apparatus which I prefer for
carrying out my Invention. I do not, however, confine myself thereto,
for instead of employing the conical worm c, the expansion and con
traction of the governor balls may impart rotatory motion to a shaft,
upon the axis of which there is an ordinary worm, taking into the
teeth of a worm wheel or arc, upon the axis of which the throttle valve
is attached or other toothed gearing; or friction surfaces may be sub-
stituted, and valves of any ordinary construction employed. That which
I claim as secured to be being, firstly, the employment of rotatory
apparatus between that usually employed in connection with the
governor and the throttle valve, for the purpose of opening or closing
the said valve. Secondly, the combination of such rotatory apparatus
with a valve opening to the condensor, for the purpose above set forth.
In witness whereof, I, the said William Todd, have hereunto set my
hand and seal, this Second day of September, One thousand eight
hundred and fifty-three.
WILLIAM TODD. (L.S.)