IMPROVEMENTS IN STEAM ENGINES
Year: 1874

page_text: LETTERS PATENT to Edward Earnshaw and Thomas Holt, both of
Rochdale, in the County of Lancaster, Engineers and Boiler Makers,
for the Invention of "IMPROVEMENTS IN STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said Edward Earnshaw and
Thomas Holt at the Office of the Commissioners of Patents, with
their Petition, on the 7th November 1874.
We, EDWARD EARNSHAW and THOMAS HOLT, both of Rochdale, in
the County of Lancaster, Engineers and Boiler Makers, do hereby declare
the nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINES,”
to be as follows:-
Our Invention relates to apparatus employed to govern the admission
of steam to the cylinders of steam engines, and has for its object to
obtain by comparatively simple means an efficient "variable cut-off,"
controlled by the governor. Upon the slide valve we mount a
** cut-off

page_text: valve," which is moved to and fro by means of a rocking shaft passing
through to the outside of the valve chest, and actuated by means of a
tappet which is formed or fixed upon a revolving shaft. We prefer to
We so
form the said tappet in one piece with the last-named shaft.
form the said tappet as that the inner part which is nearest to the axis
of revolution shall be within the diameter of the said shaft and near to
the said axis, the distance of the outer part of the tappet from the said
axis, and as a consequence the size of the tappet, being greatly reduced
as compared with ordinary tappets, whereby the surface speed of the
tappet is reduced and its action on the part to be actuated is less violent.
We cause the said tappet to act alternately upon two bowls which are
mounted on a lever or part which gives motion to a lever fixed or formed
on the outer end of the aforesaid rocking shaft, or the said bowls may
be mounted on the last-named lever.
"
To control the action of the said tappet we impart a revolving motion
to the tappet shaft by means of a worm or scrow spur wheel," which is
attached to the sleeve of the governor and gears with a second screw
spur wheel which is fixed or mounted on the said tappet shaft or on a
shaft connected therewith, the arrangement being such as that as the
speed of the governor varies the first-named screw wheel is caused to
slide in the direction of its axis, the effect of this movement being to
accelerate or retard the speed of revolution of the said tappet shaft,
according as the said screw wheel is caused to slide in one direction or
the other, the said tappet being caused to act earlier or later upon the
parts which actuate the cut-off valve, whereby the speed of the engine
is regulated.
We may cause the driven screw wheel to slide in its axial line
instead of the driver. This may be effected by means of a screw which
is revolved in one direction or the other by means of reversed catches
which are thrown into or out of action by means of the governor, or the
sleeve of the governor may be connected by a bell-crank lever, or an
arrangement of levers with the said driven screw wheel.
The aforesaid tappet may be employed in connection with other
arrangements for accelerating or retarding its revolution than those
herein indicated.

page_text: SPECIFICATION filed in pursuance of the conditions of the Letters
Patent, and of an Order of the Lord Chancellor, by the said
Edward Earnshaw and Thomas Holt in the Great Seal Patent Office
on the 5th June 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, EDWARD
EARNSHAW and THOMAS HOLT, both of Rochdale, in the County of
Lancaster, Engineers and Boiler Makers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of November, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
ninth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said Edward Earnshaw and Thomas Holt,
Her special license, that we, the said Edward Earnshaw and Thomas
Holt, our executors, administrators, and assigns, or such others as we, the
said Edward Earnshaw and Thomas Holt, our executors, administrators,
and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein
expressed, should and lawfully 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 we, the said Edward
Earnshaw and Thomas Holt, our exccutors or administrators, by an
instrument in writing under our, or their, or one of their hands and
seals, should particularly describe and ascertain 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 seven
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that we, the said Edward Earnshaw and Thomas
Holt, do hereby declare the nature of the 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
Drawings, that is to say :—
Our Intention relates to annatus amploved to govern the admission

page_text: obtain by comparatively simple means an efficient "variable cut-off"
controlled by the governor. Upon the slide valve we mount a ** cut-off
valve," which is moved to and fro by means of a rocking shaft passing
through the front of the valve chest cover, and actuated by means of a
tappet which is formed or fixed upon a revolving shaft. We prefer to
form the said tappet in one piece with the last-named shaft. We so
form the said tappet as that the inner part which is nearest to the axis
of revolution shall be within the diameter of the said shaft and near to
the said axis, the distance of the outer part of the tappet from the said
axis, and as a consequence the size of the tappet, being greatly reduced
as compared with ordinary tappets, whereby the surface speed of the
tappet is reduced and its action on the part to be actuated is less voilent.
We cause the said tappet to act alternately upon two bowls which are
mounted on a lever or part which gives motion to a lever fixed or formed
on the outer end of the aforesaid rocking shaft, or the said bowls may
be mounted on the last-named lever.
To control the action of the said tappet we impart a revolving motion
to the tappet shaft by means of a worm or screw spur wheel which gears
with a second screw spur wheel which is fixed or mounted on the said
tappet shaft or on a shaft connected therewith, the arrangement being
such as that as the speed of the governor varies one of the said screw
wheels is caused to slide in the direction of its axis, the effect of this
movement being to accelerate or retard the speed of revolution of the
said tappet shaft, according as the said screw wheel is caused to slide in
one direction or the other, the said tappet being caused to act carlier or
later upon the parts which actuate the cut-off valve, whereby the speed
of the engine is regulated.
The sliding of the screw wheel may be effected by means of a screw
which is revolved in one direction or the other by means of reversed
1.1

page_text: In the said Drawings Figs. 1 and 2 are elevations taken on planes at
right angles the one to the other; and Fig. 3 is a plan representing a
portion of the governor of a steam engine having our improvements
applied thereto.
Fig. 4 represents a portion of the steam chest in which the slide and
cut-off valves are mounted; and Fig. 5 is a section on the line A in
Fig. 4, and taken at right angles therewith.
In Figs. 4 and 5 q, q, is a slide valve which serves to govern the
admission and emission of steam to and from the steam ports 8, 8, leading
to each end of the steam cylinder and into the exhaust port t, t; the
back of the said slide valve is formed with eight ports u, u, or with any
other suitable number, as may be preferred in any case. A cut-off valve
p, p, is fitted to slide on the back of the valve q, q, a rib on the one valve,
sliding in a groove in the other valve in order to maintain the parallelism
of the said cut-off valve. The said cut-off valve is formed with six
ports v, v, the relative positions of the said ports and of the ports u, U,
being such as that when the ports at one end of the slide valve are
closed the ports at the other end are open. Two ribs o, o, are formed on
the back of the valve p, p, and a block n, n, is fitted to slide between
the said ribs. A stud or pin m, m, on a crank 1, 1, which is fixed or
formed on the shaft k, k, fits in a bored orifice in the said block, so that
when the said shaft is rotated to some extent the valve p, p, is caused to
slide upon the other valve and to open one set of ports and close the
other set. It will be seen that as the two valves p, p, and q, q, slide in
directions at right angles the one with the other the movements of the
valve q, q, do not interfere with those of the other valve, so that the
last-named valve does not slide upon the other valve until the shaft k, k,
is acted upon.
The form and arrangement of valves are such as we now prefer to
employ, but we do not confine ourselves thereto.
In Figs. 1, 2, and 3 a is the governor spindle and b is the sleeve of
the governor, the parts not represented being of any ordinary or suitable
form and construction. The said sleeve is embraced by the fork of a
lever e, which is fixed on the shaft d, which is fitted to rock in bearings
formed in the pillars w. On the outer end of the said shaft is fixed a

page_text: "
lever e which is connected by the link g with the lever i which is loosely
inounted on the end of the screw shaft which is fitted to revolve in the
standards x. The upper side of the lever i is formed as a segment of a
disc, having a central recess j. On the governor spindle is fixed a screw spur
whèel v, which gears with a second screw spur wheel which is mounted
on the shaft p so as to turn with the shaft and at the same time to slide
thereon. The last-named shaft is fitted to revolve in the standards x,
and is provided at one end with a crank pin o which works in a slot in a
lever m which is loosely mounted on the end of the screw shaft r, the
effect being that the shaft p receives a rotary motion from the governor
spindle and imparts a rocking movement to the last-named lever. On
studs n, n, fixed to the lever are mounted two reversed pawls 1, 2, which
are formed to engage with the teeth of a notched or spur wheel q which
is fixed on the said screw shaft. Each pawl is provided with a pro-
jecting stud k upon which the lever i acts to raise the pawls out of
action. When the engine is running at the proper designed speed both
pawls are kept out of action, but when the governor sleeve rises one
of the pawls is lowered into action by the movement of the recess j
towards the stud k, and on the contrary if the said sleeve falls the
other pawl is lowered into action. The consequence of this action is
that the screw shaft r is rotated in one direction or the other according
as the speed of the engine is accelerated or retarded. A forked carrier t
embraces the screw wheel v, and in or on the said carrier is fixed or
formed a nut to suit the screw r, the effect being that the said screw
wheel is slid upon the shaft p in one direction or the other, according as
one pawl or the other is lowered into action. Upon the other end of the
shaft p is formed a cam c, c, represented in cross section in Fig. 8, and
in dotted lines in Fig. 4. It will be seen that this cam is formed with
two inclined acting faces combined with two curves, which are concentric
with the axis of the shaft p which is on the dotted line B in Fig. 8, and
that the inner of the two curves is described from the said axis with an
exceedingly short radius. If preferred for any reason the said inner
curve may pass through the said axis, as indicated by the dotted lines in
the last-named Figure. The said cam acts alternately upon two "bowls”
d, d, which are mounted upon studs e, e, fixed to the lever ff, whereby
an intermittent vibrating movement is imparted to the said lever. The said
lever is connected by the link h, h, with a crank arm j, j, which is fixed
on the aforesaid shaft k, k, whereby the ports u, u, are opened and closed

page_text: or regulating the speed of engines, substantially as set forth and
indicated herein-before and in the accompanying Drawings.
In witness whereof, we, the said Edward Earnshaw and Thomas
Holt, have hereunto set our hands and seals, this Fifth day of May,
in the year of our Lord One thousand eight hundred and seventy-
fiszo
EDWARD EARNSHAW. (L.S.)
THOMAS HOLT.
Signed and sealed by the said Edward
Earnshaw and Thomas Holt, in the
presence of
HUGH G. GRANT,
Clerk to Edward K. Dutton,
Agent to the Patentees,
3, Princess Street,
Manchester.
(L.S.)