IMPROVEMENTS IN APPARATUS FOR OPERATING THE BRAKES OF RAILWAY TRAINS BY COMPRESSED AIR, PART OR PARTS OF WHICH ARE APPLICABLE TO DIRECT ACTING ENGINES OR COMBINED ENGINES AND PUMPS
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by James Steel, John McInnes, William
Robertson, and James Guthrie Orchar at the Office of the Commissioners of
Patents on the 29th January 1879.
JAMES STEEL and JOHN MINNES, both of Glasgow, in the County of Lanark,
and WILLIAM ROBERTSON and JAMES GUTHRIE ORCHAR, both of Dundee, in the .
County of Forfar, North Britain. "IMPROVEMENTS IN APPARATUS FOR OPERATING
THE BRAKES OF RAILWAY TRAINS BY COMPRESSED AIR, PART OR PARTS OF WHICH
ARE APPLICABLE TO DIRECT ACTING ENGINES OR COMBINED ENGINES AND PUMPS."
This Invention, which relates to improvements in apparatus for operating the
brakes of railway trains by compressed air, consists firstly of an arrangement of
valves for permitting the escape of air from the cylinders of such apparatus either
gradually or instantaneously, accordingly as it is required to apply the brakes for
a gradual stoppage of the train or suddenly, as in the case of an emergency "
stoppage.
"
The class of compressed air brake apparatus to which this first part of the
Invention more especially applies is that wherein the pistons hold the brakes out
of action by being maintained in equilibrio at the requisite position in their
respective cylinders through the pressure of air acting upon both sides of the
pistons, and wherein also the brakes are applied by the destruction of that equili-
brium upon the withdrawal of the compressed air from one side thereof.
An essential feature of a valvular arrangement for fulfilling the conditions before
mentioned is sensitiveness of action, so that a slight diminution of the pressure in
the main pipe by which the cylinders are charged will cause the valves to act and
discharge the air from one side of the pistons.
This valvular apparatus consists of a cylindrical casing, the upper part of which
is in communication with the main pipe leading to the charging and discharging
cock on the locomotive engine, and the lower part of which is connected to that
side of the cylinders from which the air is discharged when the brakes are to be
applied. Within this cylindrical casing is a hollow piston, in the upper and lower
parts of which respectively are valve seats with valves fitting them, and operating
as hereinafter described. The piston is so packed either with rolling spring or other
suitable packing as to be capable of moving easily and air tight within the cylinder.
At the bottom of the cylindrical apparatus is a third valve, this being the valve by
which the air is discharged from the cylinders. This last mentioned valve is con-
nected to the central valve of the apparatus, that is to say, the lowest or bottom
valve within the hollow piston. A spring is also contained within the hollow

page_text: piston for the purpose of closing the upper valve against its seat. Both the upper
valve, as well as the discharge-valve, are by preference made conical for the purpose
of affording a more graduated opening and closing thereof.
The action of this valvular apparatus is as follows:-When it is desired to apply
the brakes the cock on the locomotive engine is opened to an extent sufficient to
reduce the pressure of air in the main-pipe-either-gradually or instantly, according
to the conditions of the stoppage required. This pressure being so reduced causes
the preponderance of pressure in the brake cylinders-to-lift-the-piston-of-each
valvular apparatus, whereby the lower valve in the hollow piston is closed, and
caused to move upwards with the piston, this upward movement of the piston and
valve next lifting the discharge valve below, whereby the air is emptied from one
side of the pistons in the brake cylinders, so that the equilibrium of these pistons is
destroyed, and the compressed air on the opposite sides moves them, so as to apply
the brakes.
When it is desired to withdraw the brakes the cock on the locomotive engine is
turned into that position which admits the compressed air into the main pipes,
and thence to the upper side of the pistons of the valvular apparatus.
The effect of this is to force the pistons of the valvular apparatus down against
stops, thereby opening the lower valve in the said piston at the same time the
compressed air depresses the upper valve in the said piston, so that this air passes
around the lower valve therein, and through ports in the lower part of the piston
into the brake cylinders until the pistons therein are again brought into equilibrium,
and the brakes thereby withdrawn. So soon as this position of equilibrium is
reached the upper valve in the hollow piston is closed by a spring acting against
its underside.
It is to be understood that a valvular apparatus constituting the herein before
described first head of this Invention is applied to cach compressed air brake
cylinder and piston in a train.
The improvements relate secondly to the combined engine and pump, by means
of which the air for actuating the brakes is compressed.
This part of the improvements consists in applying a small cylinder with a
piston fitted therein, and against which the pressure of steam in the boiler con-
stantly acts. The position of this cylinder and piston is such that when the pistons
in the steam cylinder and air pump respectively and alternately move the tappets
and slide valve into those positions at which the steam is cut off the pressure of
steam from the boiler against the small cylinder completes the motion of the tappets,
and therewith the stroke of the slide valve, whereby the action of the engine is
reversed at each end of the stroke.
It is to be understood that this second part of the improvements is not limited
to engines which are to be employed for compressing air, but it is adapted for
direct acting engines, or combined-engines-and-pumps-which have not.a.crank shaft
or its equivalent.