IM- PROVEMENTS IN DIRECT-ACTING PUMPS AND IN VALVES FOR AUTOMATIC RAILWAY BRAKES, PART OR PARTS OF WHICH IMPROVEMENTS IS OR ARE APPLICABLE FOR OTHER PURPOSES."
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John McInnes at the Office of the
Commissioners of Patents on the 17th November 1877.
JOHN MINNES, of Glasgow, in the County of Lanark, North Britain.
" IM-
PROVEMENTS IN DIRECT-ACTING PUMPS AND IN VALVES FOR AUTOMATIC RAILWAY
BRAKES, PART OR PARTS OF WHICH IMPROVEMENTS IS OR ARE APPLICABLE FOR
OTHER PURPOSES."
This Invention relates in the first place to an improved construction of direct-
acting pumps for the supply of compressed air to the cylinders and receivers of
automatic air brakes.
The pump constructed in accordance with the said Invention is of the ordinary
direct-acting type, and the Invention consists in means for moving the slide valve
of the steam cylinder instantaneously at the end of each stroke into such a position
as will give free access of steam to one side of the piston as soon as it is cut off
from the other side, so as to prevent the possibility of the pump stopping "dead"
at the end of a stroke when working at a slow speed. This is effected by the
employment of a coiled or other spring, in conjunction with levers and tappets
actuated preferably from the piston of the steam cylinder and plunger of the pump.
The piston or plunger at or about the end of its stroke comes in contact with
a tappet projecting into the steam cylinder or pump barrel, and thereby moves a
lever into an angular position relative to the coiled spring which presses against its
lower extremity, or the extremity opposite to that which it is centred upon. The
spring being held in compression by the lever when they lie in the same plane
with one another, becomes partially freed by the inclination of the lever, and by
virtue of its resilience exerts a sidelong pressure on the lever, and pushes it still
further round, so that the valve, which is connected to the aforesaid lever by a
cross shaft and links, is caused to complete its stroke and admit full steam at once
to the exhausted side of the piston, so as to bring about the return stroke. The
complete stroke of the valve is thus obtained by two agencies, first, the direct action
.

page_text: of the tappet on the valve lever and connections, and, second, the concluding move-
ment imparted by the spring, both however forming one continuous motion. The
steam is thus shut off from the one port and directed into the other, without the
possibility of the valve "dwelling "so long over both ports as to cause the pump
to cease working.
Instead of the tappets projecting the one into the steam cylinder and the other
into the pump barrel, both may be actuated from the steam cylinder or pump
barrel alone, or the piston rod may be carried through the back of the cylinder,
and employed to strike the lever both ways into such a position as will enable the
spring to come into play; and the said spring, instead of being placed in compression,
may be employed so as to act by virtue of its tension.
Besides being employed for the purposes herein-before referred to, the pump
constituting this Invention may be employed for other purposes to which such
pumps are applicable.
The Invention relates, secondly, to valves, whereby compressed air is admitted
to and allowed to escape from the cylinders of automatic air brakes. The
construction and application of this part of the Invention is as follows:-On the
upper end of the air brake cylinder a valve casing is bolted, communication between
which and the part of the cylinder above the piston is maintained through a series
of perforations made in a metallic plate which is situated between the joint of the
casing with the cylinder. The said valve casing is bored out, and a piston valve is
placed therein so as as to move upwards or downwards accordingly, as the pressure
of air preponderates on its upper or under side.
The perforated plate or diaphragm herein-before referred to limits the downward
movement of the piston valve, its upward stroke being limited by the cover of the
valve casing. The piston valve is packed air-tight by cup leathers facing in
opposite directions, and held in position by metallic rings or washers, and by a cap
screwed upon the upper end of the valve. The leathers are held against the
interior of the valve case by a series of metallic rings, wire coils or their equivalent,
and the pressure of the leathers against the case is further increased by admitting
compressed air to annular spaces or channels behind the leathers and rings.
The interior of the piston valve is bored to receive two poppet valves, which fit
seats at the upper and lower parts of the piston valve, and are held apart by a
coiled spring placed between them; communication is established between the
interior of the valve casing and the interior of the piston valve by a lateral
opening or openings made under the seat of the lower poppet valve. At a distance
from the lower end of the valve casing a series of perforations or passages is inade,
which communicate with an annular port formed in the thickness of the casing, and
provided with a branch or exit.
The operating of the valve herein-before described is as follows:-When the
brakes are off, the piston valve rests at the bottom of the casing on the perforated
plate before referred to, which latter at the same time upholds the lower poppet
valve from its seat.
When it is desired to apply the brakes, the pressure of air above the piston valve
is released, and the pressure in the upper part of the brake cylinder then acting on
the under side of the piston valve raises it in the casing until the perforations or
passages communicating with the annular exit port are uncovered. As the piston
valve is thus raised, the lower poppet valve closes, and communication is established
between the upper part of the cylinder and the atmosphere, whereby the air
pressure in the cylinder is released, and the brake piston allowed to ascend and
apply the brakes.
°
The brakes are released by restoring the pressure above the piston valve, which
then descends on to the perforated plate, thereby closing the exit port from the
upper end of the cylinder, and at the same time opening the lower poppet valve,
thus allowing compressed air to pass from the upper side of the piston valve
through the upper poppet valve, and thence by the lateral openings under the seat

page_text: of the lower poppet valve into the upper end of the brake cylinder, where, acting
on the piston, the latter is caused to descend and release the brakes.
The piston valve may if desired be constructed with a greater area on its upper
than on its under side, in order to assist in overcoming the inertia thereof, when
releasing the brakes, and instead of being placed at the upper part of the brake
cylinder, as herein-before described, the said valve may be situated at any other
convenient part of the brake apparatus.