AN IMPROVED VARIABLE CUT-OFF MOTION FOR STEAM ENGINES
Year: 1874

page_text: LETTERS PATENT to John Guy Wilson, of the City of Manchester,
Mechanical Engineer and Patent Agent, for the Invention of
"AN IMPROVED VARIABLE CUT-OFF MOTION FOR STEAM ENGINES."—A com-
munication from abroad by William Herbillon, Engineer, of
Curegham, near Brussels, in the Kingdom of Belgium.
PROVISIONAL SPECIFICATION left by the said John Guy Wilson
at the Office of the Commissioners of Patents, with his Petition,
on the 31st October 1874.
I, JOHN GUY WILSON, of the City of Manchester, Mechanical Engineer
and Patent Agent, do hereby declare the nature of the said Invention
for "AN IMPROVED VARIABLE CUT-OFF MOTION FOR STEAM ENGINES," a com-
munication to me from abroad by William Herbillon, Engineer, of
Curegham, near Brussels, in the Kingdom of Belgium, to be as
follows:-
The object of this Invention is the more perfect controlling of the
admission of steam to the cylinder of steam engines by means of the

page_text: centrifugal governor, and consists in actuating the slide valve, piston, or
disc which admits steam to each end of the cylinder by means of a pair
of cams, one of such cams (herein-after called the fixed cam). being
fixed upon and revolving with the governor shaft or spindle, and the
other cam (herein-after called the adjustable cam) being mounted loosely
upon an eccentric boss formed upon the fixed cam.
This moveable cam is furnished with a segmental slot, through which
the governor shaft or spindle passes, and which slot permits of the
adjustable cam turning to a certain distance independant of the fixed
cam. This moveable cam is also connected by means of a connecting
rod to a sliding sleeve piece mounted upon an arm branching from the
shaft or spindle of the governor, and this arm also carries a bracket in
which a double-armed lever is mounted, having one of its arms connected
to the sliding sleeve piece herein-before mentioned. The edges of these
cams are at opposite points in contact with friction bowls mounted in
slides attached at their respective ends to the valve, piston, or disc con-
trolling the admission of steam to the same end of the cylinder, and
which slides are ensured keeping in contact with the cams either by the
action of springs or pistons pressed forward by steam or air pressure.
The action of this cut-off motion is as follows:-The cams are so
adjusted upon the shaft or spindle of the governor as to allow the steam
to be cut off at the desired point in the stroke of the piston, but if
through any cause the speed of the engine is increased or decreased the
moveable cam alters its relative position with regard to the fixed cam,
and so permits the steam to be cut off sooner or later accordingly.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Guy Wilson in the Great Seal Patent
Office on the 30th April 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
GUY WILSON, of the City of Manchester, Mechanical Engineer and 30
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of October, in the year of our
Lord One thousand eight hundred and seventy-four, in the thirty-seventh

page_text: year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said John Guy Wilson, Her special licence that
I, the said John Guy Wilson, my executors, administrators, and
assigns, or such others as I, the said John Guy Wilson, my exe-
cutors, 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 Irivention for "AN IMPROVED
VARIABLE CUT-OFF MOTION FOR STEAM ENGINES," a communication to me from
abroad by William Herbillon, of Curegham, near Brussels, in the
Kingdom of Belgium, upon the condition (amongst others) that
I, the said John Guy Wilson, my exccutors or administrators,
by an instrument in writing under my, 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 six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said John Guy Wilson, 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:-
The object of this Invention is the more perfect controlling of the
admission of steam to the cylinder of steam engines by means of the
centrifugal governor, and consists in actuating the slide valve, piston, or
disc which admits steam to each end of the cylinder by means of a pair
of cams, one of such cams (herein-after called the fixed cam) being
fixed upon and revolving with the governor shaft or spindle, and the
other cam (herein-after called the adjustable cam) being mounted loosely
upon an eccentric boss formed upon the fixed cam.
This moveable cam is furnished with a segmental slot, through which
the governor shaft or spindle passes, and which slot permits of the
adjustable cam turning to a certain distance independant of the fixed
cam. This moveable cam is also connected by means of a connecting
rod to a sliding sleeve piece mounted upon an arm branching from the
shaft or spindle of the governor, and this arm also carries a bracket in
which a double-armed lever is mounted, having one of its arms con-

page_text: the arms of the lever J embraces the sliding sleeve piece C, whilst the
extreme end of the other arm embraces the sliding collar A' of the
governor, and which collar is raised and lowered in the ordinary manner
by the governor. Land L' are slides provided with friction bowls M
and M', which latter are constantly held in contact with the edges of
both the fixed and moveable cams by their respective spiral springs N
and N', or the necessary pressure may be exercised upon these slides by
pistons subjected to steam or air pressure. Each of these slides is con-
nected to a distinct and separate slide, piston, disc, or other valve
for controlling the admission of steam to its respective end of the
cylinder.
The Drawing in Fig. 1, illustrating how the slide L' may be connected
to a rocking shaft for working an engine fitted with disc valves, whilst
the other slide L is shewn connected direct to a rod O for working an
engine fitted with a slide or piston valve, and which valve rod may if
desired pass through the spiral spring N, as illustrated in dotted lines.
It will however be obvious that the same description of valves and
method of connecting them to the slides L and L' would be employed
for both ends of the cylinder.
The action of this cut-off motion is as follows:-The cams are so adjusted
upon the governor shaft or spindle A as to cut off the steam at the
desired point in the stroke of the piston, and this cut-off is effected by
the cams permitting the friction bowls to drop off their highest on to
their lowest point by the action of the springs in the slides attached to
the slide or other valves, the instant at which this cut-off is effected
being controlled by the relative position of the cams with regard to each
other.
In Fig. 2 the cams are shewn in their relative position when the cut-off
is most sudden or takes place at the earliest point in the stroke of the
piston, owing to the governor being at its highest or most distended
position, the blue lines on this Fig. representing the relative position of
the moveable cam with regard to the fixed cam when the engine is
working at its ordinary and desired speed, whilst the red lines represent
the position of the moveable cam with regard to the fixed cam when the
speed has decreased so as to render it necessary to have the steam valves
open for the longest possible period.
It will thus be apparent that the action of these cams is to vary the
cut-off of the steam in accordance with the speed of the engine by

page_text: extending or curtailing the time during which the steam valves are open,
this time being regulated to the greatest nicety by the position of the
governor and sliding collar A¹ connected therewith. It will also be
further obvious that the closing of the steam admission valves, whether
in the form of slide, piston, disc, or any other description of valve, is &
controlled directly by the governor shaft, and this without the inter-
vention of the usual eccentric.
Having thus particularly described and ascertained the nature of the
said Invention, together with the best methods with which I am
acquainted for carrying the same into practical effect, I wish it to be 1
understood that I claim, the use and application of a fixed and moveable
cam for controlling the admission of steam to the cylinders of steam
engines when operated by the centrifugal governor, substantially as
and for the purposes herein-before described and illustrated on the
annexed Drawing.
annexed Drawing.
.
In witness whereof, I, the said John Guy Wilson, have hereunto
set my hand and seal, this 29th day of April, in the year of our
Lord 1875.