IMPROVEMENTS IN SLIDE VALVES POR STEAM ENGINES
Year: 1862

page_text: LETTERS PATENT to James Petrie, of Rochdale, in the County of Lan-
caster, Engineer, for the Invention of "IMPROVEMENTS IN SLIDE VALVES
POR STEAM ENGINES."
Şealed the 23rd June 1868, and dated: the 27th December 1862.
PROVISIONAL SPECIFICATION left by the said James Petrie at the
Office of the Commissioners of Patents, with his Petition, on the
27th December 1862.
I, JAMES PETRIE, of Rochdale, in the County of Lancaster, Engineer, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN SLIDE
VALVES FOR STEAM ENGINES," to be as follows:-
My Invention consists, firstly, in forming slide valves. of steam engines with
circular faces, and in imparting thereto an axial motion from any moving part
of the engine, as well as the usual sliding motion, whereby the steam may be
cut off at any part of the stroke by either of these motions. The valves may
form a portion of a circle or an entire circle.
Secondly, my Invention relates to a method of removing steam pressure
from valves of the above descriptions, or from slide valves of other construc-
tions, and consists in opening a portion of the back surfaces thereof to the
atmosphere, or in placing such back surface in vacuum by communication with
the condenser of the engine or similar apparatus.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Petrie in the Great Seal Patent Office on the 27th
June 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
PETRIE, of Rochdale, in the County of Lancaster, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of December, in the year of our
Lord One thousand eight hundred and sixty-two, in the twenty-sixth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said James Petrie, Her special license, that I, the said James Petrie, my
executors, administrators, and assigns, or such others as I, the said James
Petrie, my 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 SLIDE
VALVES FOR STEAM ENGINES," upon the condition, amongst others, that I, the
said James Petrie, by an instrument in writing under my hand and seal,
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 James Petrie, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement and accompanying Drawings, that is to say :-
My Invention consists, firstly, in a method of removing steam pressure from
slide valves, for which purpose I open a portion of their back surfaces to the
atmosphere, or upon the same principle I place such back surfaces in com-
munication with the condenser or similar apparatus. In the accompanying
Drawing this part of my Invention is shewn in two views at Figs. 1 and 2.
A portion of the cylinder is at a, the ports at b, and the exhaust passage at c.
The slide valve of ordinary construction is shewn at d, worked by means of
the rod e in the usual manner. At the front of the valve box f there is a cross
bar g mounted upon screw studs h, and carrying loosely a pin i, which abuts
at its inward end against a cross piece k, carried by a hollow piston l. This
piston passes through the face of the valve box and through a stuffing box m

page_text: formed thereon.
Between the cross bar g and a shoulder upon the pin i is a
spring n, which therefore tends to force the said pin forward and with it the
piston l, until its inward end presses against a plate o, attached to and moving
with the slide valve d. The plate o in the direction of the slide valve's motion
is of such a length that during the opening and closing of the ports the inside
aperture of the piston 7 will always be closed, and an escape of steam from the
valve box thus prevented. It will be seen that as the piston is open to the
atmosphere it represents a given surface upon the slide valve from which the
steam pressure is removed, and that this removal may be increased or diminished
as desired by varying the area of the said piston. In order to secure at all times
a sufficient pressure to keep the slide valve to its seat, the spring n before
mentioned is adapted, and the elastic force thereof may be regulated by
tightening or loosening the nuts of the cross bar g.
The next part of my Invention is shewn at Figs. 3 and 4, in which a
portion of the cylinder is at a, and the ports at b, c. The valve seat
is at d, and instead of being flat as for ordinary slide valves, it is a por-
tion of a cylinder formed in the valve box e. The slide valve is at f
cylindrical in form, so as to fit the seat d, and it receives the usual sliding
motion by means of the rod g. Each of the ports b, c, consists of several (in
this instance, four) separate passages, and there is a corresponding number of
passages h formed in the cylinder, constituting the slide valve. Supposing the
passages h (Fig. 3) to be situate opposite to those shewn at 6 (and which con-
stitute a port) be coincident, then the upward and downward motion will
alternately open and close the ports as in ordinary flat slide valves; but if
during this reciprocating motion a turning of the rod g be effected, then the
passages h will be brought opposite to the solid parts of the seat, as seen in
Fig. 3, and the steam will be shut off. This turning of the shaft may be
effected by any ordinary mechanism connected to a moving part of the engine
and adapted to suit different constructions of engines or situations thereof, or
it may be caused to take place sooner or later through the medium of the
governor, as is well understood in applying cut-off motions. The apertures h
in the slide valve for the port c are situate between those which belong to the
port b, so as to obtain the necessary alternate action.
In the Drawing I have shewn the first part of my Invention combined with
that just described, and a description thereof would merely be a repetition of
that given in reference to Figs. 1 and 2, excepting that in this instance the
piston is formed at its inward part so as to correspond to the curve of the
cylindrical slide valve.

page_text: I have shewn also both parts of my Invention as applied to valves which
are situate at the middle of the cylinder, but it will be obvious that two pistons
may be employed to relieve the pressure when slide valves at each end of the
cylinder are used, and that the cylindrical slide valve niay be divided to suit
such arrangements.
I would remark in conclusion, that I am aware that rotatory motion as well
as a sliding motion has been imparted to valves used for regulating the flow of
steam into cylinders of engines, but in that case the said valves were pistons, and
not as in the case of my improvements what are commonly called slide valves.
Having thus described and ascertained the nature of my said Invention,
and the manner of carrying the same into effect, I desire it to be understood
that I claim as secured to me under the above in part recited Letters
Patent,―
Firstly, opening a portion of the back surfaces of slide valves to the atmo-
sphere, or placing them in communication with the condenser.
Secondly, forming slide valves as cylinders or portions of cylinders, and
imparting an axial motion thereto.
In witness whereof, I, the said James Petrie, have hereunto set my
hand and seal, this Twenty-sixth day of June, in the year of our Lord
One thousand eight hundred and sixty-three.
JAMES PETRIE, (L.S.)