AN IMPROVED SLIDE VALVE
Year: 1861

page_text: LETTERS PATENT to Michael Henry, of 84, Fleet Street, in the City of
London, Patent Agent, for the Invention of "AN IMPROVED SLIDE VALVE."
-A communication from abroad by Jean Baptiste Edouard Plaine-
maison, Engineer, of 33, Boulevard Saint Martin, Paris.
Sealed the 21st June 1861, and dated the 1st January 1861.
PROVISIONAL SPECIFICATION left by the said Michael Henry at the
Office of the Commissioners of Patents, with his Petition, on the
1st January 1861.
I, MICHAEL HENRY, of 84, Fleet Street, in the City of London, Patent
Agent, do hereby declare the nature of the said Invention for "AN IMPROVED
SLIDE VALVE," communicated to me from abroad by Jean Baptiste Edouard
Plainemaison, Engineer, of 33, Boulevard Saint Martin, Paris, to be as
follows:-
The principle on which my construction of valve is based is this, when the.
body of a weight is placed on an inclined plane, so that the tangent of
inclination equals the coefficient of friction, the body will remain in a state of
equilibrium; and my Invention consists in constructing a valve in such manner
as to apply the theory of the decomposition of forces acting on a body placed
on an inclined plane, in order to balance or place in equilibrium the pressure
exerted by the steam or other fluid on the valve. I propose to place on the

page_text: perfectly smooth or true top, or back part or parts of the valve, a plate or
piece which covers the same over (recouvre), and has its ends resting on
inclined planes or supports. When it leaves the latter it is kept from sliding
on the valve by springs, the angle which the inclined supports make with the
valve face (table) being such as above described, the covering piece, notwith-
standing the pressure it has to support, will have no tendency to come down
or rest upon the slide valve.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Michael Henry in the Great Seal Patent Office on the
1st July 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MICHAEL
HENRY, of 84, Fleet Street, in the City of London, Patent Agent, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the First day of January, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Michael Henry, Her special-licence-that-I, the said Michael Henry, my
executors, administrators, and assigns, or such others as I, the said Michael
Henry, 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 "AN IMPROVED SLIDE VALVE,"
communicated to me from abroad by Jean Baptiste Edouard Plainemaison,
Engineer, of 33, Boulevard Saint Martin, Paris, upon the condition (amongst)
others) that I, the said Michael Henry, my executors 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 Michael Henry, do hereby declare the
nature of the 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 thereof, as communicated to me, reference being had to the accom-

page_text: panying Drawings, and to the letters and figures marked thereon, that is to
say:-
In engines furnished with the ordinary slide valve arrangements the large
amount of pressure exerted by the steam against the valve considerably
increases the friction of the valve and seating, and occasions a quicker wearing
away of the surfaces in contact, in that and in other respects objectionably
interfering with the proper working of the engine and the durability of several
of its parts. Now, the object of this Invention is to provide means whereby
the pressure so injuriously exerted shall be taken off, and only sufficient
pressure left to keep the slide in due contact with its seating, and prevent its
rising therefrom too readily (that is to say when a small amount of lifting
effort is exerted against it).
T
tang
This Invention is founded on the following mathematical principles :-
Suppose a body or weight P placed on a plane inclined at an angle d to the
horizontal, the force with which the body would move down the plane
naturally would be represented by P sin: af, P cos: a=T, supposing ƒ to
stand for the coefficient of friction. Now, the body P may be of any desired
shape, and may only slide or move at its two ends on inclined planes, while its
central portion is horizontal and remains so if P descends, and is brought into
contact with a parallel plane C, D, and the pressure exerted by P on this
fixed plane will be represented by an a that is to say, that the angle can be
calculated in such manner that whatever be the value of P, the pressure of
C, D, may be as small as desired. Now, suppose that instead of any
imaginary plane C, D, I take the upper or back surface of an ordinary slide
valve or surface parallel to the plane of the valve face, and let P be a piece or
plate of metal, which I call the covering piece or covering plate. If this
plate be in contact with a slide valve, the real pressure that the steam would
exert on such valve would be reduced by a quantity equal to that which is
taken off from the portion of its surface concealed or covered over by the
covering plate, while the pressure of steam acting normally would be borne by
the covering plate, but would be resolved by the theory of the resolution of
forces into pressures acting against the inclined planes that support the
covering plate at the ends, as was stated in reference to the imaginary
weight P. Hence by suitably calculating the amount of surface to be given
to the ordinary valve or slide, the amount of pressure may be deduced. to any
required point. And the construction may proceed on such calculations that
the covering plate when rested on its supports and placed in contact with the
slide, may either be in equilibrium or may have a certain tendency to descend.
In the former case the pressure being in equilibrium will be wholly taken off.

page_text: the slide, while in the second case the pressure remaining will exert a very
small effect. As the valve face gets gradually worn away and consequently
becomes depressed, so to speak, in the steam chest, the covering plate shifts
its position, correspondingly sliding for that purpose on its inclined supports,
so as to accommodate or adjust itself to the altered position of the slide, but
this self-adjustment or change of position does not affect the equilibrium
previously acquired, which remains unaltered, for which purpose there must
always be component T not in equilibrium. To guard against the chances
of the covering plate being shaken out of place, and to neutralize the effects
of gravity when the valve is not horizontal, two springs are employed, the
power of which is properly calculated for this purpose.
The principle of construction on which the Invention is founded may be
said to consist, theoretically speaking, in calculating the angle in such manner
that the covering plate when acted on by the various forces exerted against it
may be in equilibrium, except only allowing for the difference of about T lbs.,
and the whole of the pressure is in equilibrium with or equipoised by the
friction, except so much as is represented by the force T necessary for securing
the change or rather adjustment of position of the plate, as above explained,
and which produces an amount of friction proportionate to
T
tang a
Practically speaking the principle on which the Invention is founded may
be carried into effect by planing or otherwise forming a portion of the upper
or back surface of an ordinary slide valve as perfectly smooth or true as may
be, and covering it over by a plate supported at its two ends on inclined
planes.
The accompanying Drawings represent this improved valve arrangement,
that is to say, a valve with the present improvements applied, shewing how the
Invention may be carried into effect.
Figure 1 is a transverse section of the valve arrangements through the
line M, N, of Figure 2; Figure 2, longitudinal section through the line a, b,
of Figures 1 and 3; Figure 3, plan through the line e, f, of Figures 1 and 2.
A is a slide or valve of ordinary construction, excepting that its upper or
back surface B is planed, polished, or otherwise formed quite smooth or true,
and upon this surface is placed a cast-iron plate D which covers it over, as
shewn, and rests at its two ends d, d, upon inclined planes c, c, cast in the
steam chest; the slide A travels to-and-fro between its seating m, n, and the
covering plate D working against the former in the usual manner when
actuated by ordinary valve gear o, p; the form of the part A, considered
separately is in no respect altered except in regard of being made smooth or
true. at the back or top as stated. The plate D is formed with strengthen-

page_text: ing ribs, and furnished with a lubricator g. E, E, are two springs for pre-
venting the plate D from sliding on the valve A when it moves from its
supports c..
By employing this arrangement, which does not involve any considerable
modification of the engine, the friction and consequent wearing of the valve,
valve gear, and seating are considerably reduced, and various portions of the
gear are far less exposed to risk of breakage; the steam ports may be con-
structed as large as desired, and the engine works in better order, and may be
reversed at any speed without having to shut the throttle valve.
Having now described the nature of the said Invention, and in what manner
the same may be performed, I declare that I claim,-
First, the practical application of the theory of the resolution of forces, as
herein described, to the purpose of bringing into equilibrium or balancing the
pressure exerted by steam upon the surface of slide valves.
Second, the combination of the slide or valve A formed true or smooth on
its upper or back surface, with the covering plate D resting at its ends upon
inclined planes cast or formed in the steam chest, in the manner herein-before
described and represented in the accompanying Drawings.
Third, the general arrangement and combination of parts forming the
improved slide valve arrangement, herein-before described and represented in
the accompanying Drawings.
In witness whereof, I, the said Michael Henry, have hereunto set my
hand and seal, this First day of July, in the year One thousand eight
hundred and sixty-one.
Witness,
S. E. A. NEWSOME,
Patent Office,
84, Fleet Street.
M. HENRY. (L.S.)