IMPROVEMENTS IN OR APPLICABLE TO RAILWAY BRAKE APPARATUS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Frank Herbert Hebblethwaite at
the Office of the Commissioners of Patents on the 24th May 1882.
FRANK HERBERT HEBBLETHWAITE of the City of Manchester, in the County
of Lancaster, Engineer, "IMPROVEMENTS IN OR APPLICABLE TO RAILWAY BRAKE
APPARATUS."
"
Firstly, My invention relates to automatic brakes actuated by a piston or
diaphragm, either by pressure or a vacuum, and my invention consists in applying
a valve (a ball valve by preference) to the diaphragm or piston to allow air to pass
to or from the cylinder on one side of the piston or diaphragmn to the cylinder on
the other side of the piston or diaphragm, but to close against its return, so that
when the apparatus is actuated by pressure, the air can enter from the cylinder
at the upper side of the piston and pass through the valve to the cylinder and
pressure chamber at or connected with the lower side of the piston and when the
pressure of the air is allowed to pass out of the train pipe the valve will shut
against the return of the air from the pressure chamber, and this air will then
expand and lift the piston or diaphragm to apply the brakes.
But when the apparatus is actuated by a partial vacuum the valve permits the
air to be withdrawn from the cylinder on both sides of the piston or diaphragm,
but it prevents the air from re-entering the vacuum chamber when the atmosphere
passes into the train pipe which thus acts to put on the brakes.
Secondly, My invention relates to brake apparatus so arranged as to be readily
changed to be operated either by pressure or vacuum, and my invention consists
in arranging a diaphragm or piston large enough for working by vacuum, and
in combining the cylinder for this piston or diaphragm with one chamber for
vacuum and one for pressure, or in forming two separate chambers of unequal
capacity in one vessel.
The pipe connections or passages between the piston or diaphragm cylinder, and
the chambers for pressure and vacuum pass through a five way or other cock or
valve, so that when the latter is in one position say for working by vacuum, the
train pipe communicates with the underside of the piston or diaphragm through
one passage in the cock and between the vacuum chamber and upper side of the
diaphragm, through another passage in the cock, the passage to the small pressure
chamber being shut by the cock.

page_text: But when the cock is turned or reversed to work the brakes by pressure, the
train pipe is then open through the passage and the cock to the upper side of the
diaphragm or piston and through the valve in the latter, and through the passage
in the cock to the pressure chamber, the passage to the vacuum chamber being
then closed.
Or there are or may be two chambers of unequal capacity, or the two chambers
are or may be in one vessel, and when the cock is in one position both chambers
are brought into communication through the cock and are used for vacuum, but
when the cock is in another position when the brakes are to be operated by
pressure only the small chamber is open through the cock to the brake cylinder.
By the use of the comparatively small chamber above referred to for pressure
combined with the large piston or diaphragm required for vacuum, the pressure in
the small chamber diminishes rapidly when the piston or diaphragm begins to
move, and thus excessive pressure on the brake mechanism is obviated when
working such brakes by pressure.
My invention also consists in accomplishing the object of this part of my
invention by employing one or more safety valves in the piston or diaphragm
loaded to the intended working pressure, which valve when the brakes are held
off, by pressure will be kept shut, as both sides of the piston or diaphragm will be
in equilibrium but when the pressure is let out of the train pipe the valve or valves
will open and allow all pressure above that at which the valve or valves is loaded
to pass out.