Improvements in and connected with Slide Valves.
Year: 1891

page_text: Date of Application, 14th July, 1891
Complete Specification Left, 14th Apr., 1892-Accepted, 14th May, 1892
PROVISIONAL SPECIFICATION.
Improvements in and connected with Slide Valves.
I, JULES THÉODORE ANATOLE MALLET of 30, Avenue Trudaine, Paris,
France, Engineer, do hereby declare the nature of this invention to be as
follows:-
In variable expansion valve gears which operate by varying the travel of a
single slide valve, the compression of the steam in the cylinder is liable, when
the admission is very much reduced, to exceed the boiler pressure at the end of
the stroke and to avoid this it has been proposed to arrange the relief valves on the
cylinder heads so as to allow the steam to return to the valve chest when the
compression becomes excessive. All the arrangements hitherto employed have
been either inconvenient or complicated and necessitate considerable alteration of
the cylinders or the use of additional fittings for the relief valves.
The object of the present invention is to obviate the above disadvantages, and it
consists in mounting the relief valve upon the slide valve itself, in connection with
passages leading through the valve face.
Reference is to be had to the accompanying drawing, forming part of this
Specification, which represents a longitudinal section of a slide valve having a
relief valve c mounted at the back of the slide valve and communicating with a
channel similar to that in a Trick or Allen slide valve for giving an additional
admission orifice, the two advantages of a double admission and the prevention of
excessive compression being thus combined. When the slide valve closes the port a,
the cylinder is in communication with the channel and valve c; if therefore the
pressure in the cylinder becomes greater than that in the valve chest m n, the
relief valve c will rise and allow part of the steam to return to the valve chest.
It may also be desirable to prevent the formation of a partial vacuum or
excessively low pressure in the cylinder by too much expansion, or when the engine
is reversed whilst running and for this purpose I employ a similar relief valve
applied to control the connection of the channel with the exhaust cavity of the
slide valve so as to permit the exhaust steam to return to the cylinder.
The two valves may be applied either conjointly or separately, and in the former
case they would be disposed side by side in the direction of the length of the slide
valve. The relief valve c may be of any form or arrangement best suited for
application to the slide valve the invention residing broadly in the application to
all kinds of slide valves whether of flat, cylindrical, or other form, of a relief valve
or valves, as hereinbefore specified.
VI
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J. T. A. MALLET,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
Improvements in and connected with Slide Valves.
I, JULES THEODORE ANATOLE MALLET of 30, Avenue Trudaine, Paris,
France, 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 :—
In variable expansion valve gears which operate by varying the travel of a single
alide valve the compression of the steam, especially in the high pressure cylinder of

page_text: compound engines, is liable, when the admission is very much reduced, to exceed
the boiler pressure at the end of the stroke and to avoid this it has been proposed
to arrange the relief valves on the cylinder heads so as to allow the steam to return
to the valve chest when the compression becomes excessive! All the arrangements
hitherto employed have been either inconvenient or complicated and necessitate
considerable alteration of the cylinders or the use of additional fittings for the
relief valves.
The object of the present invention is to obviate the above disadvantages, and it
consists in mounting the relief valve upon the slide valve itself, in connection with
passages leading through the valve face.
Reference is to be had to the drawing left with my Provisional Specification and
forming part of this Specification, which represents a longitudinal section of a slide
valve having a relief valve c mounted at the back of the slide, valve and com-
municating with a channel similar to that in a Trick or Allen slide valve for
giving an additional admission orifice, the two advantages of a double admission
and the prevention of excessive compression being thus combined. When the slide
valve closes the port a the cylinder is in communication with the channel b and
valve; if, therefore, the pressure in the cylinder becomes greater than that in
the valve chest m m the relief valve c will rise and allow part of the steam to return
to the valve chest.
It may also bo desirable to prevent the formation of a partial vacuum or
excessively low pressure in the cylinder by too much expansion or when the engine is
reversed whilst running, and for this purpose I employ a similar slide valve applied
to control the connection of the channel 6 with the exhaust cavity of the slide valve
so as to permit the exhaust steam to return to the cylinder. The two valves may
be applied either conjointly or separately, and in the former case they would be
disposed side by side in the direction of the length of the slide valve. The relief
valve o may be of any form or arrangement best suited for application to the slide
valve, the invention residing broadly in the application to all kinds of slide valves,
whether of flat, cylindrical or other form, of a relief valve or valves, as herein before
specified.
Having now particularly described and ascertained the nature of the said inven-
tion, and in wliat manner the same is to be performed, I declare that what !
claim is :-
1st. The combination, with a steam engine slide valve, of a relief valve mounted
on the slide valve and applied to control the communication of a passage leading
through the valve face, with the valve chest, in the manner and for the purpose
specified.
2nd. The combination, with a steam engine slide valve, of a relief valve mounted
on the slide valve and applied to control the communication of a passage-leading
through the valve face, with the exhaust cavity of the valve, in the manner and for
the purpose specified.
3rd. The combination, with a steam engine slide valve, of two relief valves
applied to control the communication of a passage opening through the valve face,
respectively with the valve chest and with the exhaust cavity of the valve, as and
for the purposes specified.
Dated this 14th day of April 1892.
J. T. A. MALLET,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.