Improvements in or connected with the Operation and Balancing of Slide and Piston Valves of Steam Engines.
Year: 1889

page_text: Date of Application, 29th Oct., 1889
Complete Specification Left, 29th July, 1890-Accepted, 30th Aug., 1890
PROVISIONAL SPECIFICATION. ·
Improvements in or connected with the Operation and Balancing of
Slide and Piston Valves of Steam Engines.
I, JOHN THOM, of Inverkip, in the County of Renfrew, North Britain, Engineer,
do hereby declare the nature of my said invention to be as follows:-
This invention has reference, chiefly, to the slide and piston valves of steam
engines, (particularly large ones), that is, the valves which control the ingress and
egress of steam to and from the cylinders of the engines; and it is more especially
applicable to valves of vertical or diagonal or other inclined type of steam engines,
the weight of whose valves are * balanced."
In setting forth the nature of my invention, I will take the case of, say, a vertical
inverted cylinder marine steam engine the slide or piston valves of which are provided
with":
balancing cylinders," and describe such cylinders with improvements accord-
ing to my invention applied thereto, that is, constructed and adapted to operate,
in accordance with it it consists as follows:-The balancing cylinder is provided
with a piston, and steam is admitted to the cylinder, and, normally, presses upon
the under side of the piston during the main portion of its up and down strokes.
At or near the end of each stroke of the piston, that is, before it reaches the end
of each stroke, communication, between the end of the cylinder which the piston is
approaching, and the steam supply, is cut off, and the steam in the space thus closed
is compressed by the latter end of the stroke of the piston; a cushion is in this wise
formed between the piston and the top or bottom of the cylinder, as the case may
be, and the inertia of the valve (together with that of its rod and/balancing piston)
is thereby gradually overcomo and the stopping and reversal of direction of motion
is effected without the valve gear being subjected to jar or severe stresses.
An arrangement by which the above operations may be conveniently effected
consists in providing the steam inlet passage at one end, and a by-pass passage at the
other end of the balancing cylinder, and arranging them in such a position relatively
to the space (longitudinal) traversed by the piston in its stroke, that such steam
passages or ports are covered by the piston at the desired points of its up and down
strokes, and steam thereby inclosed or imprisoned in the respective ends of the
cylinder, and compressed: Hence the reaction of the steam against the piston, while
being compressed, overcomes the inertia due to the momentum of the slide or piston
valve (and parts connected with it), and then, when the reversal of direction of
motion commences, its reaction upon the piston overcomes the inertia due to the state
of rest to which the valve and its parts have been brought, with the result herein
above mentioned.
The by-pass passage conducts the steam from beneath the piston to the space
above it, and it need only be of such a length and size that steam has sufficient time
to travel round the piston during its stroke, and fill the said space above it. This
by-pass passage may be provided in the metal of the cylinder after the manner of a
cylinder port, or by forming a recess in the metal, with a part of the bearing surface
removed, or in any suitable way.
It is to be understood that the improvements herein described are as a whole, or in
part, applicable to various kinds and arrangements of a valve and valve gears, and it
is not, therefore, intended to confine them to the particular application herein more
particularly specified.
Dated this 28th day of October 19800
CHEESBROUGH & ROYSTON,
Applicant's Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in or connected with the Operation and Balancing of
Slide and Piston Valves of Steam Engines.
I JOHN THOм, of Inverkip, in the County of Renfrew, North Britain, Engineer, 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, chiefly, to the slide and piston steam distribution
valves of steam engines, (particularly large ones); that is, the valves which control
the ingress and egress of steam to and from the cylinders of the engines; and it is
more particularly applicable to valves of vertical or diagonal, or other inclined type of
steam engine, the weight of whose valves are
: balanced."
In setting forth the nature of my invention, I will take the case of, say, a vertical
inverted cylinder marine steam engine, the slide or piston valves of which are
provided with "balancing cylinders," and describe such cylinders with improvements
according to my invention applied thereto, that is, constructed and adapted to
operate, in accordance with it; it consists as follows:-The balancing cylinder is
provided with a piston, and steam is admitted to the cylinder, and, normally, presses
upon the under side of the piston during the main portion of its up and down strokes.
At or near the end of each stroke of the piston, that is, before it reaches the end of
cach stroke, communication, between the end of the cylinder which the piston is
approaching, and the steam supply is cut off, and the steam in the space this closed
is compressed by the latter end of the stroke of the piston; a cushion is in this wise
formed between the piston and the top or hottom of the cylinder, as the case may be,
and the inertia of the valve (together with that of its rod and balancing piston) is
thereby gradually overcome, and the stopping and reversal of direction of motion. is
effected without the valve gear being subjected to jar or severe stresses.
An arrangement by which the above operations may be conveniently effected,
consists in providing a steam inlet passage at one end, and a by-pass passage at the
other end of the balancing cylinder, and arranging them in such a position relatively
to the space (longitudinal) traversed by the piston in its stroke, that such steam
passages or ports are covered by the piston at the desired point of its up and down
strokes, and steam thereby inclosed or imprisoned in the respective ends of the cylinder,
and compressed. Hence the reaction of the steam against the piston, while being
compressed, overcomes the inertia due to the momentum of the slide or piston valve
(and parts connected with it), and then, when the reversal of direction of motion
commences, its reaction upon the piston overcomes the inertia due to the state of rest
to which the valve and its parts have been brought, with the result herein above
mentioned.
The by-pass passage conducts the steam from beneath the piston to the space above
it, and it need only be of such a length and size that steam has sufficient time to
travel round the piston during its stroke, and fill the said space above it. This by-pass
passage may be provided in the metal of the cylinder after the manner of a cylinder
port, or by forming a recess in the metal, with a part of the bearing surface removed,
or in any suitable way.
It is to be understood that the improvements herein described are as a whole, or in
part, applicable to various kinds and arrangements of a valve and valve gears and it
is not therefore, intended to confine them to the particular application herein more
particularly specified.
Having thus specified generally the nature of my invention, its description will now
be proceeded with in reference to the annexed drawing (which forms a part of this
Specification) by way of explaining more fully the nature of the invention. The drawing
and the description thereof set forth together the improvements in and connected with
the operation and balancing of slide and piston valves of steam engines, the nature of
which has been above explained.

page_text: With reference to the drawing which shews my invention applied to a slide valve of
an inverted cylinder steam engine, a designates the cylinder of the engine; b, the
slide valve; c, the slide valve casing; and d, the balancing cylinder. The balancing
cylinder d is provided with a piston e, and steam is admitted to the cylinder d, and,
normally presses upon the under side of the piston e during the main portion of its up
and down strokes, in such a way, that a cushion is formed between the piston e and the
top or bottom of the cylinder d, as the case may be, and the inertia of the valve b is
thereby gradually overcome.
The arrangement in the example shewn in the drawings by which the above cushioning
is effected, consists in providing the steam inlet passage at one end, and by-pass
passages at the other end of the balancing cylinder d. These passages hand i are so
arranged as to be closed by the piston e at the desired point of its up and down
strokes, and steam is thereby alternately inclosed in the space k at the bottom of the
cylinder d in the down stroke of the piston, and in the space m at the top of the
cylinder in the up stroke of the piston. The dotted lines shew the position of
the piston e when passing the by-pass i, and the full lines shew the piston e at half
stroke and at the point at which steam is shut in the space k by the shank e¹ of the
pistón e entering the neck h, with which it (the shank) makes a joint.
By the above arrangement, the reaction of the steam against the piston e, while
being compressed, overcomes the inertia due to the momentum of the valve b and
parts connected with it, and then when the reversal of direction of motion commences,
its reaction upon the piston e overcomes the inertia due to the state of rest to
which the valve and its parts have been brought, with the results above mentioned.
The by-pass passages i are of such length and size that the steam has (during the
passage of the piston e) time to pass round the piston and fill the portion m at the
top of the cylinder.
•
The by-pass passages i serve to keep the pressure at the top end of the cylinder e
constant or normal, even if the balance piston e is leaky, and no escape pipe or cock
is required; whilst the neck serves as a drain passage for water from the cylinder,
as well as the passage for steam to the cylinder.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. In combination with a steam distribution valve, of a steam engine, a balancing
cylinder constructed to effect a cushioning of steam at the ends of the up and down
or in and out strokes of the piston thereof, whereby the inertia of the valve and its
parts, is overcome; substantially as and for the purposes set forth.
2. The herein described improvement connected with the operation of the steam
distribution valves of steam engines, consisting in causing steam to be confined in a
cylinder or cylinders and compressed at or near the end of the strokes of the valve
and by the movement of said valves; for the purposes specified.
3. The balancing cylinder and piston, arranged, constructed, and adapted to operate,
substantially as set forth with reference to the drawing.
Dated this 28th day of July 1890.
CHEESBROUGH & ROYSTON,
15, Water Street, Liverpool, Applicant's Patent Agents.