Improvements in or connected with the Lubrication of Slide Valves of Steam Engines.
Year: 1891

page_text: Date of Application, 29th Sept., 1891-Accepted, 7th Nov., 1891
COMPLETE SPECIFICATION.
Improvements in or connected with the Lubrication of Slide Valves
of Steam Engines.
I, ALFRED JAMES STEVENS, of Saint John's College, Cambridge, in the
County of Cambridgeshire, Clerk in Holy Orders, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
This invention has reference to the slide steam distribution valves of steam
engines; that is, the slide valves which control the ingress and egress of steam to
and from the cylinders of those steam engines in which slide valves are made use of
for the purpose of steam distribution.
The invention is also applicable to slide "expansion" valves, as well as to the
slide steam distribution valves at the back of which they work or slide.
The invention consists in making concave pits or depressions in the valve faces
or faces against which slide valves of steam engines work or slide; the said pits
or depressions to be made in any portions of the said faces to which stem has or
may have access when the engines are working; the said pits or depressions being
so shaped or formed that they are concave throughout the whole of their surface,
and that their depth increases gradually from all points in their edges.
The two characteristic features or qualities which, as aforesaid, appertain to the
shape or form of the concave pits or depressions, are clearly exhibited by means
of the accompanying drawing, which shows a section of a concave pit or
depression as above described, and of the adjacent portions of the valve face or
face against which the slide valve works, and in which the raid concave pit
or depression is made; the plane of section being a plane at right angles to the
valve face or face against which the slide valve works.
A B and C D are straight lines which are in line with each other, and are
portions of the intersection of the plane of section with the valve face or face
against which the slide valve works. The curved line B E C is the intersection of
the plane of section with the surface of the concave pit or depression. It is evident
from the drawing that the curve BEC is throughout its whole length concave
towards the valve face or face against which the slide valve works. It is also
evident from the drawing that the depth of the curve BEC below the level of A B
or CD, increases gradually from the points BC, that is, increases gradually from
the two points where the curve intersects the valve face or face against which the
slide valve works.
The concave pits or depressions are to be so shaped or formed that their sections
by any planes at right angles to the valve face or face against which the slide valve
works shall possess the same two properties which, as above described, are inherent
in the section BEC; namely, that any such section shall, throughout its whole
length, be concave towards the valve face or face against which the slide valve
works; and that the depth of such section shall increase gradually from the two
points where it meets or intersects the valve face or face against which the slide
valve works.
The usefulness of my invention depends on the fact that the lubrication of
slide valves of steam engines is usually or normally effected by causing the steam
in the steam chests in which the slide valves work to have or contain a certain
amount of oil or lubricant mixed with it. The steam being thus to a greater
or less degree charged with oil or lubricant, particles of the said oil or lubricant
tend to adhere to, or be deposited on, any metal surfaces with which the steam
comes in contact.
I proceed to explain my invention as applied to any particular slide valve; the

page_text: same explanation holding good for all slide valves to which the invention may be
applied.
The invention consists, as aforesaid, in making concave pits or depressions in the
valve face or face against which the slide valve works or slides; the pits or
depressions being made in any portions of the face to which steam has access, or
may have access, when the engine is working. As the valve slides to and fro its
working (or sliding) surface passes to and fro across the pits or depressions, made
as aforesaid, so that they are alternately covered by the working surface of the
valve and clear of the working surface of the valve. Whilst any one of them is
clear of the working surface of the valve, steam has access to it as well as to some
adjacent portion of the face. This being so, the particles of oil or lubricant con-
tained in, or mixed with, the steam tend to adhere more readily to the concave
surface of the pit or depression than to the plane surface of the face in which it is
made. This is owing to capillary action, (sometimes called capillary attraction).
Consequently a greater amount of oil or lubricant will in general be deposited by
the steam on the concave surface of the pit or depression than on the plane surface
of the adjacent parts of the face. When the working surface or the valve is
passing over any one of the pits or depressions, such pit or depression is, while the
said working surface is over it, covered up, or closed over, by the said working
surface. This being so, the portion of the surface of the pit or depression situated
near to the edge of the pit or depression forms an angular groove, or grooved
space, with the working surface of the valve. (This takes place in the same way
as when a cup, shaped like a segment of a sphere, is covered by a flat plate, an
angular groove, or grooved space, is formed inside the cup, near its rim, by the
meeting of the flat surface of the plate with the concave surface of the cup.) The
oil or lubricant that has been previously deposited by the steam, as above described,
in the concave pit or depression, will now be drawn into the aforesaid angular
groove or grooved space by capillary action; and thus will be brought in contact
with the working surface of the valve, and a portion of this oil or lubricant
will, owing to the movement of the valve, be drawn between the working surface of
the valve and the face against which the valve works; and thus the lubrication
of the valve will be improved.
In consequence of this improvement taking place in the lubrication of slide
valves, the said slide valves, as well as the faces against which they work, will last
longer than would otherwise be the case. Moreover, the friction to be overcome
in driving the valves being diminished, there will be less work expended in driving
the valves, and consequently a greater amount of useful work will be obtained from
the steam engines to which the valves belong.
The concave pits or depressions hereinbefore described, provided always that
they be so shaped or formed as herein before described, need not be shaped or
formed alike in all other respects. Preferably, but not necessarily, they should
be shaped or formed as segments of spheres, or approximately as segments of
spheres.
The said concave pits or depressions need not be all of the same size or
dimensions. As regards their size or dimensions: their depth should preferably not
exceed one fiftieth of an inch; and, if the width of any one of them be taken to
mean the greatest distance between any two points in its edge, their width should
preferably not exceed one tenth of an inch. Or they may be made of any suitable
size or dimensions.
As regards their arrangement, or the plan of their distribution over the face in
which they are made: they may be made in parallel rows, the pits or depressions
in each of the said rows being equidistant from each other; and the said rows
being themselves equidistant from each other. The direction of the said rows may
be at right angles to the direction of motion of the valve; or they may have any
suitable direction. Or the concave pits or depressions may be distributed over the
face according to any suitable arrangement.
As regards the number of the said concave pits or depressions to be made in any

page_text: particular face. In any particular face, their number should preferably be such,
that the aggregate area of those portions of the face which are not occupied by
them should be not less than one half of the whole area of the face. Or any
suitable number may be made in any particular face.
They may be ground out in the face by means of emery wheels of suitable size
and shape, or by means of boring tools, or instruments, of suitable size and shape,
or by any suitable process. Or they may be made by any suitable process.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
The herein described improvement in or connected with the lubrication of slide
valves of steam engines, which consists in making concave pits or depressions in
the valve faces or faces against which slide valves of steam engines work or
slide; the said pits or depressions to be made in any portions of the said faces
to which steam has or may have access when the engines are working; the said
pits or depressions being so shaped or formed that they are concave throughout
the whole of their surface, and that their depth increases gradually from all points
in their edges.
Dated this Twenty-ninth da of Cantombos 1001