CERTAIN IMPROVEMENTS IN THE SLIDE VALVES OP STEAM ENGINES
Year: 1856

page_text: LETTERS PATENT to John Mills, of the firm of Mills and Whittaker, of
Oldham, in the County of Lancaster, Engineer, for the Invention of
"CERTAIN IMPROVEMENTS IN THE SLIDE VALVES OP STEAM ENGINES."
Sealed the 12th August 1856, and dated the 13th February 1856.
PROVISIONAL SPECIFICATION left by the said John Mills
at the Office
of the Commissioners of Patents, with his Petition, on the 13th
February 1856.
I, JOHN MILLS, of the firm of Mills and Whittaker, of Oldham, in the
County of Lancaster, Engineer, do hereby declare the nature of my said
Invention for CERTAIN IMPROVEMENTS IN THE SLIDE VALVES OF STEAM ENGINES,"
to be as follows:-
My Invention applies solely to the slide valves of steam engines, and
whether constructed of the ordinary D form or otherwise, and consists in the
novel application of a peculiarly formed valve thereto, for the purpose of
cutting off the steam at any given point when used expansively. This valve*
consists of two brass (or other suitable metal) plates, provided with openings
or passages for the admission of steam. The plates or discs are placed face to
face against each other, and have corresponding openings formed in each of
them; one of the plates being fixed, the other turning upon it in such a

page_text: manner as to bring the steam passages opposite, or to close them by means
of a spindle passing through the moveable one, and connected with any
suitable motion or part of the engine to effect the "cut off" of the steam as
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Mills in the Great Seal Patent Office on the
13th August 1856.
:
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN MILLS,
of the firm of Mills and Whitaker, of Oldham, in the County of Lancaster,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of February, in the year of our Lord
One thousand eight hundred and fifty-six, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Mills, Her especial license that I, the said John Mills, my executors,
administrators, and assigns, or such others as I, the said John Mills, 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 CERTAIN IMPROVEMENTS IN STEAM
ENGINES, upon the condition, amongst others that I, the said John Mills,
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 John Mills, do hereby declare the
nature of my said Invention, and 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) :-
..
My Invention applies solely to the slide valves of steam engines, and
whether constructed of the ordinary D shape or otherwise, and consists in the
novel application of a peculiar form of valve thereto, for the purpose of
cutting off the steam from the cylinder at any given point when used expan-
sively; this valve consisting of two brass (or other suitable metal) plates

page_text: provided with openings or passages for the admission of steam. The plates
or discs are placed face to face against each other, and have corresponding
openings formed in each of them; one of such plates being fixed, and the
other turning upon it in such a manner as to bring the steam passages
opposite, or to close them by means of a spindle passing through the moveable
one, and connected with any suitable motion or part of the engine to effect
the "cut off" of the steam as required.
.
In order that my Invention may be more readily understood and explained
in detail, I have attached to these Presents a Sheet of Drawing; Figs. 1 and 2
being made upon a scale of about one inch to a foot, and Figs. 3 and 4 being
enlarged detail views; each Figure having similar letters of reference marked
upon corresponding parts of the apparatus.
Fig. 1 is a transverse section, taken through one of the steam passages or
'ports" of a steam cylinder, and shewing the application of the valve for
cutting off the steam in connection with the cam for working the same.
Fig. 2 is a longitudinal section of one-half of a steam cylinder, taken through
the steam chest and cylinder, illustrating more clearly the position of the cut
off valves, and also the connection of the same through the medium of the
coupling crank, which is actuated by the cam. Fig. 3 is a front elevation of
the disc, having bevilled apertures forming the valve for "cutting off" the
steam; and Fig. 4 is a sectional elevation, taken through the discs and slide
valve.
In Fig. 1, a is the steam cylinder; and b, the port or passage for the admis-
sion of steam; c, c, are the discs, placed face to face against other stationary or
non-rotating plates d, d, which have apertures e, e, corresponding with the
apertures f. f, in the discs e, e, through which the steam passes before entering
the cylinder; a double arrangement of these plates or discs e, e, is provided,
one at each end of the slide valve g, and which are connected together by
means of the axle or central rod h, the extremities of which are squared, and
slide in the bearings of the connecting crank i, which receives a reciprocating
motion from the cam k through the rod 1, by which it is connected. It will
be evident, that when a reciprocating motion is imparted to the crank 1, by
means of the cam k, a similar motion will be given to the rod 1, and thence to
the outer discs e, e; thus the discs will partake of a reciprocating motion in a
direction partly round its central axle or rod, by which motion the apertures
in the disc c will first be brought over or opposite to those in the place d
(at which time the valve will be open), and then the said part of the disc will
cover the apertures on the plate d (when the valve will be shut). By this
arrangement I am enabled to cut off the steam from the cylinder (when

page_text: required to work expansively) at, any given point. of the stroke, which. will be
regulated by the different, form of cam employed. The working of this
improved, valve will be more easily understood on. reference to. Fig. 2 in the
Drawings attached; and to the following description thereof:-Steam being
admitted, into the steam chest, and the slider valve being open to the, ingress
steam "port," the cam will move the crank., which will turn the disc c
upon the plate d, and allow the steam: to pass. directly down through the
straight passage or "port" into the cylinder,, then before the slidé, valve closes
the inlet, "port," the cam, being suitably formed; will, cut off the steam at a
given point, and allow that which. is already in the: upper portion. of the
cylinder to expand and force the piston a:down; to the full extent of the stroke,
then the slide valve will slide back, taking, with, it the cut off valve,, and close
the aperture at the upper end of the: cylinder and open the one; at the lower
end, when the other set of discs will be brought into action to perform a
similar operation to the one before explained. By this arrangement.: of "cut
off valve I am enabled to form the passages or "ports" for the admission
of steam to the cylinder in a straight line, and parallel to the top and bottom
of the cylinder, in lieu of the. S-shaped "ports" at present in use, and by
which more steam is wasted at every stroke of the piston than when the
straight "port" (as shewn in the Drawing) is used.
Having now described the nature and object of my said: Invention;, together
with the manner of carrying the same into practical effect, I wish it to be
distinctly understood that I claim as my Invention for certain improvements
in steam engines, first, the novel application of the particular arrangement of
disc valves at each end of the cylinder for the purpose of "cutting off-" or
admitting the steam to the cylinder at any part of the stroke when working
expansively. by the employment of which valves I am enabled to have a direct
communication or "straight port." from the steam chest to the cylinder in
lien of the S-shaped passage at present in use, and by the use of which
straight "port" a great saving of steam is effected.
In witness wliereof, I, the said John Mills, have liereunto set my hand
and seal, this Twelfth day of August; in the year of our Lord One
thousand eight hundred and fifty-six:
JOHN MILLS. (L.S.)