IMPROVEMENTS RELATING TO MEANS FOR CUSHIONINg the PISTONS OF STEAM OR OTHER ENGINES
Year: 1884

page_text: †, HENRY HARRIS LAKE, of the firm of Haseltine, Lake, & Co, Patent Agents,
Southampton Buildings, in the County of Middlesex do hereby declare the nature
of my invention for "IMPROVEMENTS RELATING TO MEANS FOR CUSHIONINg the
PISTONS OF STEAM OR OTHER ENGINES" and in what manner the same is to bè
performed, to be particularly described and ascertained in and by the following
statement?
In steam and other engines, and especially in condensing engines working with
a small admission of high-pressure steam, the change of direction at the dead
points in the alternate motions of the piston produces in the working parts which
transmit the power of the steam, injurious strains or shocks which are in a great
measure due to the inertia of these parts and to the vis viva acquired by them,
and this vis viva must be overcome at each change of stroke, to the detriment of
the material, of which the said parts are formed, the molecular state of which is
rapidly changed, thereby frequently causing dangerous ruptures.
In order to avoid the strains above referred to, while the valve is closed against
the escape of steam, that is to say during the period of compression, a small
quantity of steam is admitted behind the piston so as to augment the pressure
produced by the compression. This pressure can, if necessary, attain the initial
pressure of the steam in the boiler.
In this manner the vis viva of the piston is gradually overcome and from the
moment of the opening of the valve for the admission of steam, the steam from
the boiler enters a space the pressure in which is but slightly different from, or
even equal to, its own; and consequently no shock can be produced.
In order to produce this effect in a practical manner, the arrangements herein-
after described and illustrated in the accompanying drawing, the figures of which
are herein after referred to, have been adopted.
A A' indicate a portion of the cylinder, and m m³ the ports of the said cylinder.
B B represent the slide-valve in two parts but rigidly connected; and having

page_text: inlet ports a a' for the steam; and small holes c c¹ formed in the lap of the slide
and permitting the introduction of a certain quantity of steam during the
compression.
It will be understood on reference to the drawing that when the part of the
slide covers the port m¹ the period of compression commences and this period
continues until the edges of the slide has uncovered the port of the cylinder.
What has been stated above happens in the engines heretofore made, and
especially in those in which the compressed steam never attains a pressure of more
than from 1 to 2 kilogrammes. When the opening of the admission port takes
place the steam enters, at a pressure of say 6 kilogrammes, into a space under a
low pressure and produces those very dangerous strains referred to.
By means of the openings c and c¹ formed in the lap of the valve-face, as soon as
the compression has commenced, a small quantity of steam enters the cylinder so
as to augment the pressure of the compressed steam therein.
The number and the area of these orifices, which may have a cylindrical or any
other form, are so calculated that the final pressure of the compression is sufficient
to prevent the strains.
Instead of forming holes c c¹ as described small notches may be formed at the
edges of the distributing slide, or small auxiliary slides or lift valves or clacks or
cocks or other similar devices which permit a certain quantity of steam to enter
into the cylinder during the period of compression may be employed.
This invention may be applied to engines driven by steam or by other elastic
fluid.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is :-
First. Injecting steam or other fluid into the cylinder of an engine from the
commencement, and during the period of compression in order to increase this
compression as, and for the purpose, specified.
Second. The improvement comprising the holes in the face of the slide for
introducing steam or other fluid into the cylinder.
Dated this 27th day of December 1884.
HASELTINE, LAKE & Co.,
For the Applicant.