Improvements in Cut-off Valves for Steam Engines.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Cut-off Valves for Steam Engines.
THOMAS WILLIAM SCOTT 1 Hollydale Cottages Addison Road Bromley Kent
Engineer do hereby declare the nature of this invention to be as follows:-
The invention consists of a cylinder fitted with a semi-web or cylindrical lines, the
said cylinder to be fitted with ports suitable to the proposed shape, and the valve to
be in accordance with said ports, so as to admit and exhaust steam alternatly from
either side of main piston in working cylinder.
I THOMAS WILLIAM SCOTT of 1 Hollydale Cottages, Addison Road, Bromley, Kent,
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:-
The object of this invention is to provide a simple, efficient and almost perfectly
balanced cut-off valve for steam engines whereby the difficulties experienced with D
and other slide valves will be overcome, and the invention consists in a novel
construction of rotary or rocking valve.
In carrying out this invention I employ two discs placed at any suitable distance
apart, and connected together by a web having a width equal to the diameter of the
discs. The discs, as well as the edges of the web, are fitted with packing in any
convenient manner to make a steam tight joint.
The steam is preferably inade to enter through a central opening in one disc, and
the web is formed with a suitable recess or chamber, of an area equal to the disc
opening, and arranged to direct the steam to one side of the web but the steam may
enter in the reverse direction if desired.
The valve works in a cylinder having suitable ports and passages in connection
with opposite ends of the piston cylinder and it is provided with a stem by which it
can be oscillated in any convenient manner from the crank axle or other part of the
engine.
In the accompanying drawings
Fig. 1 is a front view of the improved valve.
Fig. 2 is a longitudinal section.
Fig. 3 is a sectional view shewing the valve in position with the steam inlet and
outlet, and the passages to the piston cylinder, and

page_text: Fig. 4 is a view, of the nature of a diagram, showing a method of operating the
valve from an excentric on the crank shaft of the engine.
A and B are the two discs connected together by the web C and having a stem D.
All these parts are preferably cast in one piece.
In the disc A is a central opening A¹ which connects with a recess or chamber C
formed in the web as shown.
E, Fig. 3 is a pipe which may be used as the steam pipe and fits into the end of
the valve case opposite the hole or opening A'.
G is another pipe which may be used as the exhaust or vice versa as may be
desired. In the arrangement shown steam will enter at A¹ pass into the chamber C¹,
and thence to one side of the web C, exhausting at the back of the web, as indicated
by the arrows Fig. 3.
The valve is operated by a well known link motion connected with an excentric on
the crank shaft H (see Fig. 4). This link motion also provides for reversing which
can be effected while the engine is running and without shutting off steam.
By the use of this novel construction of valve I may increase the port area without
increasing the work on the excentric and the whole weight of the valve is taken off
the eccentric. It is possible to reverse the engine with one excentric and the
reversing can be effected under full head of steam without the aid of steam reversing
gear no matter how large the main engine may be.
The whole of the back pressure on the back of valve of the old D type so
detrimental to power of engine is overcome and the valve is almost balanced.
It will keep itself steam tight without producing any unnecessary amount of
friction and the ports of cylinder can be made any size compatible with size of
cylinder without any detriment to the valve, thereby increasing the efficiency of the
steam in a low pressure cylinder (on a triple engine) and it can be worked at any
grade of expansion. The valve can be examined at sea in about one quarter the time
of an ordinary D valve as there are no doors to sling in order to get at it.
For locomotive work where the cylinders are between the side framing, the bore
can be increased to the full area taken up by the present valves and boxes.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be perforined, I declare that what I
claim is:-
1. A cut off valve for steam engines constructed, arranged and operating as herein
shown and described.
2. A cut off valve for steam engines consisting of two discs one perforated and
connected by a web of a width equal to the diameter of the discs such web containing
a recess or chamber of an area equal to the opening of the disc as and for the purpose
set forth.
1007
NEWTON & SON,
Agents for the Applicant.