IMPROVEMENTS IN Ex- PANSION GEAR FOR MOTIVE POWER ENGINES
Year: 1875

page_text: LETTERS PATENT to William Edward Garforth, of Dukinfield, in the.
County of Chester, and William Walker, of Manchester, in the
County of Lancaster, for the Invention of "IMPROVEMENTS IN Ex-
PANSION GEAR FOR MOTIVE POWER ENGINES."
Scaled the 7th September 1875, and dated the 10th March 1875.
PROVISIONAL SPECIFICATION left by the said William Edward
Garforth and William Walker at the Office of the Commissioners
of Patents, with their Petition, on the 10th March 1875.
We, WILLIAM EDWARD GARFORTH, of Dukinfield, in the County of
Chester, and WILLIAM WALKER, of Manchester, in the County of
Lancaster, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN EXPANSION GEAR FOR MOTIVE POWER ENGINES," to be as
follows:-
Our Invention relates to the variable cut-off apparatus or expansion
gear employed to "cut off" the steam, that is to say, to close the
passage or passages for the inlet of steam into the cylinders of steam

page_text: engines at earlier or later periods in the strokes of the pistons, according
as the duty required to be performed by the engine in each case may be
lessened or increased. To this end we employ a double gridiron valve
which is fitted to slide upon the back of the slide valve in a direction at
right angles to the direction of motion of the said slide valve, and wo
impart the necessary intermittent sliding motion to the said gridiron
valve by means of a tappet cam or wiper which is mounted upon a screw
shaft that is connected with the governor. The said tappet is fitted to
work in a slot, in a framing, or between checks which prevent sideways
movement, so that when the said screw shaft is moved in the direction
of its length the said tappet is caused to revolve. The said screw shaft
is caused to revolve in unison with the crank shaft of the engine, and
imparts the necessary revolving movement to the said tappet, and is
connected with the governor in such a manner as that a variation in the
speed of the engine will cause the said screw shaft to move endwise in
one direction or the other, as the case may be, and the tappit will thereby
be caused to act earlier or later upon the said gridiron valve. In an
arrangement which we now consider to be suitable the said screw shaft
is fitted to slide within a hollow shaft which receives motion from the
governor spindle. A key passing through the said screw shaft slides in
slots in the said hollow shaft. The said screw shaft is connected with a
sleeve which is fitted to slide upon the said hollow shaft, and is connected
with the sleeve of the governor by means of a bell-crank lever or of an
arrangement of levers. The spindle which imparts motion to the
aforesaid gridiron valve is provided at its inner end with an antifriction
bowl or wheel, or is attached to a block which is fitted to slide between
checks on the said valve.
In some cases. or if preferred, we may employ any ordinary or suitable
SPECIFICATION in pursuance of the conditions of the Letters Patent, 30
filed by the said William Edward Garforth and William Walker
in the Great Seal Patent Office on the 10th September 1875.

page_text: WILLIAM WALKER, of Manchester, in the County of Lancaster, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Tenth day of March, in the year
of our Lord One thousand eight hundred and seventy-five, in the
thirty-ninth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto us, the said William Edward Garforth and
William Walker, Her special license that we, the said William Edward
Garforth and William Walker, 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, usc, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN EXPANSION GEAR FOR
MOTIVE POWER ENGINES," upon the condition (amongst others) that we,
the said William Edward Garforth and William Walker, our executors,
administrators, and assigns, by an instrument in writing under our, or
their, or one of our or 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 Scal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that wc, the said William Edward Garforth and
William Walker, 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 Invention relates to the variable cut-off apparatus or expansion
gear employed to "cut off" the steam, that is to say, to close the
passage or passages for the inlet of steam into the cylinders of steam
engines at earlier or later periods in the strokes of the pistons, according
as the duty required to be performed by the engine in each case may be
lessened or increased. To this end we employ a double gridiron valve
which is fitted to slide upon the back of the slide valve in a direction at
right angles to the direction of motion of the said slide valve, and we
impart the necessary intermittent sliding motion to the said gridiron

page_text: valve by means of a tappit cam or wiper which is mounted upon a screw
shaft that is connected with the governor. The said tappit is fitted to
work in a slot in a framing or between checks which prevent sideways
movement, so that when the said screw shaft is moved in the direction
of its length the said tappit is caused to revolve. The said screw shaft
is caused to revolve in unison with the crank shaft of the engine, and
imparts the necessary revolving movement to the said tappit, and is
connected with the governor in such a manner as that a variation in the
speed of the engine will cause the said screw shaft to move endwise in
onc direction or the other, as the case may be, and the tappit will thereby
bo caused to act carlier or later upon the said gridiron valve.

page_text: contrary, when the ports d are covered by sliding the gridiron valve the
ports e are open, the effect being to admit the steam to the two ends of
the steam cylinder in alternation. On the back of the valve ƒ aro
formed two projecting ribs i, which are suitably planed and finished to
form two parallel faces upon which the collar or head of a spindle k
may act to effect the sliding of the said valve. The said spindle is fitted
to revolve in an orifice bored in a block 2, and the head of the said
spindle is turned so as to act as an antifriction bowl or roller. The
block is fitted to slide in a recess formed in the steam chest cover or
bonnet, and is attached to a spindle m, which is fitted to slido in a
stuffing box formed on the said cover. The spindle m is formed with a
"tee head," which is connected by means of the pillars n with a similar
spindle, which is fitted to slide in a bearing formed in the upper end of
the hollow standard o, which is secured to the steam chest cover, tho
two "tee heads" forming tables upon which a camp may act alternately
to effect the sliding to and fro of the said spindle, and as a consequence,
of the block and the gridiron valve. The camp is mounted upon a
screw shaft q, which is fitted to slide within a hollow shaft r, and is
caused to revolve therewith by means of a cottar 8, which slides in slots
in the hollow shaft and is fixed in a slot in the said screw shaft.
said hollow shaft is fitted to revolve in a bearing formed in a boss pro-
jecting from the standard o, and also in a bearing formed in the standard
of the governor O, which in the example is constructed on the principal
of the well-known "Porter's governor." The said hollow shaft receives
a revolving motion from the governor spindle by means of the bevil
gearing t. The sleeve of the governor is connected by a bell-crank lever
u with a sleeve v, which is mounted upon the hollow shaft and is fitted
to slide thereon as the sleeve of the governor rises or falls. The sleeve
is connected by means of a pin or cottar which passes through slots in
the hollow shaft with the head of a rod w, which is connected with one
end of the screw shaft q, the arrangement being such as that the said
screw shaft is caused to slide to and fro by the rising and falling of the
sleeve of the governor. The cam p is fitted to revolve between two
checks formed within the standard o, and is tapped to suit the threads
on the said screw shaft which are cut to a long pitch, as indicated, or is
fitted with keys which enter the threads in the said shaft, so that,
supposing the hollow shaft to be at rest and the said screw shaft to be
slid in one direction or the other, the said cam would be caused to revolve
Tho

page_text: arranged and acting substantially as and for the purpose herein-before
set forthi and indicated.
In witness whereof, we, the said William Edward Garforth and
William Walker, have hereunto set our hands and seals, this
Ninth day of September, in the year of our Lord One thousand
eight hundred and seventy-five.
Signed and sealed by the said
William Edward Garforth
and William Walker in the
presence of
EDWARD K. DUTTON,
WILLIAM E. GARFORTH. (L.S.)
WILLIAM WALKER.
Agent to the Patentees,
3, Princess Street,
Manchester.
(L.S.)