IMPROVEMENTS, IN. THE METHOD OF EFFECTING AN INSTANTaneous Cut-OFF IN STEAM ENGINES BY. THE ACTION OF THE GOVERNOR
Year: 1873

page_text: LETTERS PATENT to Arthur Thomas Allcock, of Gainsboro', in the
County of Lincoln, for the Invention of "IMPROVEMENTS, IN. THE
METHOD OF EFFECTING AN INSTANTaneous Cut-OFF IN STEAM ENGINES BY. THE
ACTION OF THE GOVERNOR."
Sealed the 2nd December 1873, and dated the 3rd October 1873.
PROVISIONAL SPECIFICATION left by the said Arthur Thomas Allcock
at the Office of the Commissioners of Patents, with his Petition,
on the 3rd October 1873.
I, ARTHUR THOMAS ALLCOCK, of Gainsboro', in the County of Lincoln,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE METHOD OF EFFECTING AN INSTANTANEOUS CUT-OFF IN STEAM ENGINES BY
THE ACTION OF THE GOVERNOR," to be as follows :—
This Invention relates to that class of expansion gear in which a
sudden closing of the cut-off valve is obtained by releasing it from the
gear that opened it, and more particularly to the method of connection
between the regulating governor and the releasing catch or detent, by
which means a greater range of expansion can be obtained, and the
sensibility of the governor is not affected by its having to release the
cut-off, that being done by the valve gear, the time and position only of

page_text: the release and cut-off being determined by the governor. This I do by
the following means:-The main valve for the admission and eduction
of the steam is of the ordinary gridiron D form, and worked by any of
the ordinary methods. On the back of this valve works the cut-off
valve, which when disconnected from its excentric always comes back.
to one place on the main valve, travelling with it and covering the
admission ports, but not effecting the eduction.
.The position of the cut-off valve on the main valve is ensured either
with-springs, or by preference with a small double compression cylinder
attached either to the main valve in the steam chest or to its valve rod
outside. A piston works in this cylinder, and has its rod passing air-
tight through the covers attached to the cut-off valve. Two small
openings are made in the middle of this cylinder, the width of the piston
apart, to provide a free passage for the steam or air to follow up the
piston on the non-compression sido and ensure its regular return to its
..normal position on the main valve..
"
:
:
When the cut-off valve is connected by the detent to its excentric it
receives.a.motion corresponding_in_time_and_direction-to-that-of-the-
engine piston. The connection between the cut-off valve and-its
excentric, is made..with a singlo..detent .or: releasing catch, which is
opened by a pawl having a variable motion, the amount and direction of
this motion being regulated from the governor by the following means:
-An oscilatory motion of the same time and velocity as the travel of
the main valve, or nearly so, is given to a curved and slotted link about a
_central pivot; to be exact the oscilations should be those obtained from
an excentric at right angles to the crank, but for practical purposes the
slight difference due to the lead of the main valve excentric may be
neglected. A slide block can be traversed in this link by the action of
the governor, and is connected by a radius bar to the pawl which releases
the detent, so that the variable motion of the link is communicated to
the pawl with a greater or less travel and in either direction, according
to the rising or falling of the governor, thus altering the point of cut-off.
The motion thus given to the pawl is such that it can only come in
contact with the detent once in cach stroke of the valve.
Any adjustment of the grade of expansion may be mado-by-altering
the length of the rod between the governor and the slide block."

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Arthur Thomas Allcock in the Great Seal Patent
Office on the 2nd April 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ARTHUR
THOMAS ALLCOCK, of Gainsboro', in the County of Lincoln, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date, the Third day of October, in the year of
our Lord One thousand eight hundred and seventy-three, in the
thirty-soventh year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Arthur Thomas Allcock, Her
special licence that I, the said Arthur Thomas Allcock, my executors,
administrators, and assigns, or such others as I, the said Arthur Thomas
Allcock, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times there-
after 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 In-
vention for "IMPROVEMENTS IN THE METHOD OF EFFECTING AN INSTANTANEOUS
) CUT-OFF IN STEAM ENGINES BY THE ACTION OF THE GOVERNOR," upon the
condition (amongst others) that I, the said Arthur Thomas Allcock, my
executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, should particularly describė
and ascertain the nature of the said Invention, and in what manner
5 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 Arthur Thomas Allcock, 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 in writing, reference being had to tlic accom
panying two Sheets of Drawings, that is to say :-
1
In Sheet No. 1, Figs. 1 and 2 represent in elevation and plan one
modification of my Invention. A is the main slide valve of ordinary
› construction and worked in the usual manner by its valve rod a and
excentric a* ; B is an expansion valve working on the back of the
main valve, and connected through its valve rod 6 by the catch or detent

page_text: i
O to its own excentric c. This excentric is so fixed on the engine shaft
that when the catch or detent C is in gear with the valve rod bit gives
a motion to the valve B corresponding in time and direction to the
stroke of the engine piston. The expansion valve B has a small piston a
attaclied to it working in a cylinder y, which is connected to the main i
valvo A, so that as the valvo B is moved by its excentric over the back
of the main valve A the steam is compressed at one end of the cylinder y,
which upon tho catch or detent O being opened instantaneously moves
the piston and expansion valve B back to mid position, covering the
steam ports in the main valve A and cutting off any further supply of 1
steam to the engine cylinder: Two small ports or openings are mado.
in the cylinder y midway of its length for a free entrance and exit of
the steam on the non-compression side of the piston x. After tho
valve B is released from its excentric and is returned to a mid position
over the main valve A the two valves move together until the rod 6 of 1
the expansion valve B falls into gear, again with the catch C, when the
excentric c commences to move its valve B and open the steam ports in
the main valve A in readiness for the next stroke of the engine. The
-lap-on-the-valves is made-sufficient-to-prevent any-readmission of steam
whilst tho expansion valve B is thus opening the steam. ports. The
catch or detent C is opened and the valve B released from its excentric
rod c at any portion of the stroke of the engine as determined from the
governor by the following means:-The curved and slotted link D is
caused to oscillate about a fixed centre by the rod d, connecting one end
of the link to the joint of the main valvo rod a, thus causing it to move
in the same time and with the same velocity as the main valve, or nearly
80. The dio block E is raised or lowered in the link D by the action of
the governor, thereby giving more or less travel in citlier direction to
the pawl or striker F, to which it is connected by the radius rod f, and
thus causing the striker or pawl F to come in contact with and open the
catch or detent C, releasing the valve B from its excentric c sooner or
later during the stroke of the engine. It will thus be seen that the
actual work of opening the catch or detent C is performed by the engine
itself by means of the link D, the governor merely determining the
point at which such opening shall take place, and thereby being relieved
from all strains which would affect its accuracy.
.
The dotted lines and small figures from 0 to 8 represent the positions
of the releasing apparatus during eight equal portions of the stroke of

page_text: Fig. 3 represents another modification of my Invention, to which the
same explanation and letters of reference apply as in Figs. 1 and 2, the
difference being that the valves are worked through the medium of
weigh shafts and levers, as the valves are placed on the top of the engine
cylinder, thereby making the path of the catch or detent an arc of a
circle instead of a right line.
In Sheet 2, Figs. 4 and 5 represent an elevation and plan of another
modification of my Invention. In this case there is not room in the
valve chest of the engine to admit of the cylinder y being placed directly
on the back of the main valve, and also the eccentric rod a* cannot bo
brought in a straight line with the valve A. The cylinder y is therefore
placed outside the valve chest and bolted between the valve rod a and
an auxiliary valve rod a* *, which is connected to the excentric rod a*,
so that the valve A, the valve rods a and a* *, and the cylinder y are
moved simultaneously by the excentric. The valve B has its piston
working in the cylinder y, as before described, so that the return of the
valve B to a mid position on the valve A is effected by the action of
compressed air in lieu of steam, as shewn in Sheet 1, Figs. 1, 2, 3.
Figs. 6 and 7 represent an elevation and plan of another modification
of my Invention, the return of the valve B to a mid position over the
valve A being ensured by the springs 8 and 8* in place of the cylinder y
and piston .
Having now particularly described my Invention and in what manner
the same is to be performed, I do not confine myself to the precise detail
set forth in the accompanying Drawings, as in adapting my Invention
to existing engines the same may require to be slightly modified, but
what I claim and wish to be understood as my Invention is,―
Firstly. The methods of making an elastic communication between
the main and expansion valves A and B, as shown in the Drawings, or
any mere modification thereof, so that the latter may be moved over the
back of the former by its excentric, but upon being released shall
instantaneously return to a mid position, close the steam ports in the
main valve, and the two valves travel together until such time as the
expansion valve comes into gear again with its excentric to open in
readiness for the next stroke of the engine.
Secondly. Opening and releasing the catch or detent O by a pawl or
striker F, which receives a motion from a link D driven from the main

page_text: valve or its equivalent, so that a great range of expansion is ensured with
the use of only one catch or detent, substantially as shown Sheet 1,
Figs. 1 and 3.
Thirdly. Connecting the governor to the link D so that more or less
motion in either direction is communicated to the pawl or striker F for 5
the purpose of opening the catch or detent C sooner or later during the
stroke of the engine, thereby putting the range of expansion under tho
immediate control of the governor and relieving it from all strain which
would affect its accuracy, substantially as shewn in Sheet 1, Figs. 1
and 3.
In witness whereof I, the said Arthur Thomas Allcock, havo herc-.
unto set my hand and seal, this Twonty-eighth day of February,
in the year of our Lord Ono thousand cight hundred and seventy-
four.
ARTHUR THOMAS ALLCOCK. (L.S.)