AN IMPROVED CONTINUOUS RAILWAY BRAKE
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Daniel Biddle at the Office of the
Commissioners of Patents on the 23rd October 1878.
DANIEL BIDDLE, of Kingston-on-Thames, in the County of Surrey, Surgeon.
"AN IMPROVED CONTINUOUS RAILWAY BRAKE."
This brake is actuated by compressed air stored up in a reservoir under each
carriage, and is negative in character, the arrangement being such that the brake
remains applied and the train cannot leave the station if there be any serious flaw
in the apparatus.
Every portion of the apparatus which is subjected to any shock or strain is
separated from the body of the carriage equally with the carrying wheels by
the springs on which the carriage rests. To effect this a double-arched girder
extends between the bearings of the wheels fore and aft on both sides of the
carriage. The two arches of which each girder is composed are in opposition, the
one ascending towards the middle of the carriage, the other descending. They are
bound rigidly together by light connecting rods. Upon the summit of the two
girders rests a transverse platform extending the whole width of the carriage.
There is also a transverse arch extended between the middle points of the two
descending arches. At the extremities of the two girders are vertical plates which
are attached to the bearings of the carriage and the axle boxes in such a way by
horizontal bolts with nuts, that by removing some of the bolts the girders will be
left connected with the carriage only, and that by leaving these and removing the
others the girders will remain connected with the wheels. This arrangement is
intended to facilitate inspection of the wheels and of the carriage respectively.
Upon the transverse platform rests the reservoir which occupies nearly its whole
length, being about ten times longer than broad. It is furnished at one extremity
with a stop-cock which allows of speedy escape of the imprisoned air in case of
necessity. The reservoir at its middle communicates with a hollow cylinder.
This cylinder is fixed underneath the platform, and occupies a central position.
It is vertical, but its length does not exceed its breadth. It contains a piston which
accurately fits it with a piston rod which pierces its lower cover and whose distal
extremity is in connection with the levers by which the brake is applied and with-
drawn. The air as it is condensed (by means herein-after described) enters the

page_text: cylinder at a point low down so as to force the piston up, and in this way the brakes
are withdrawn. When the piston has been elevated to a sufficient height, any further
air which is pumped in passes to the other side of the piston by a special channel
formed by openings in the side of the cylinder near its upper end, and by a grooved
plate screwed on and properly adjusted-to-them-Only_in_this_way_can_fresh air
enter the reservoir placed above. When the pumping ceases the piston descends a
little below the lower of the two openings in the side of the cylinder by force of
gravity, but resting on a cushion of condensed air is maintained at its height until
the air on which it rests is allowed to escape, when it descends-with-a-force-equal-
-to-its-own weight (together with that of so much of the apparatus as hangs on it)
plus the pressure of the air above which can be any amount that is thought desirable.
The escape of the air is regulated by means of stop-cocks on the engine and in the
guards' vans, and-if-considered-advisable there might_be_a_stop-cock in connection
with the apparatus in every compartment, throughout the train. But as the brake
is applied automatically, whenever a serious escape of air takes place the brake is
instantly applied when carriages break away.
The tubes of communication between the carriages are made of pliable material,
and are single, the couplings to each half being of precisely the same size and shape.
These couplings are of peculiar construction, and bring the condensed air itself into
requisition to prevent its own escape. The notched metallic tube on which the
pliable tube is securely fastened gradually enlarges into a hollow cylinder of about
twice the internal diameter and about two inches in length. Within this hollow
cylinder works a cup-shaped piston having the bottom of it external and pierced by
a central opening equal in diameter to the calibre of the pliable tube. Between
this piston and the hollow cylinder is placed a middle sheath of caoutchouc which
is secured to the brim of the outer cylinder and to the brim of the cup-shaped
piston by bands of inetal, one of which consequently will move with the piston
upon the inner surface of the hollow cylinder, whilst the other will be fixed to the
brim of the cylinder and afford a suitable surface within which the piston can move
a short distance in and out of the cylinder. It will be observed that no air can
escape except through the central opening of the piston. The piston projects from
the hollow cylinder when at rest about a quarter of an inch, but the elasticity of
the caoutchouc will allow it to be pressed in and then will exercise a corresponding
pressure in the opposite direction. The projecting part of the piston presents a
smooth flat surface around the central opening, and this is brought into apposition
with the corresponding surface on the other half of the coupling, and the two are
thus held by hooked connectors which by semi-rotation upon circular inclined
planes (running round the rims of the couplings) gradually drive both pistons in.
In this way an escape of air at ordinary pressure is prevented by mere force of the
elastic caoutchouc, and as the air becomes condensed its tendency is to drive the
whole pistons out of the cylinders, but as this is impossible owing to the rigid con-
nectors, the two surfaces of the pistons which are in apposition are pressed together
with an ever increasing force, although there is no hindrance to the passage of air
through the tube, the opening in the pistons being of equal size with the calibre of
the tube.
.
To avoid an undue escape of air when carriages are slipped at a station, and yet to
insure its escape when they break away, there is a joint with stop-cock action at
the extremities of the rigid pipe underneath each carriage, and this joint can easily
be bent by the porter who is entrusted with the operation of slipping before the
connection is severed.
It will be observed that although the description hitherto has included air reser-
voirs, cylinders, and tubes of communication, no mention has been made of any
valves or valve boxes, and the absence of these forms one peculiarity of my air
brake. And in order to make the whole work independently of separable valves,
which afford so many loop holes for escape of the air, and render the apparatus
doubly liable to get out of order, it is intended to construct the condenser and the
steam cylinder adapted to it also on a peculiar plan, valve action being performed

page_text: by the several pistons and piston rods without the intervention of any but the
surfaces into contact with which they themselves are brought.
The condenser is constructed to act both forwards and backwards, the air entering
the cylinder at its middle by a properly protected opening. The piston occupies
nearly half its length, so that the amount of air condensed at each stroke is only
half what the cylinder would contain. The piston rod runs right through both
steam and air cylinders, transfixing both pistous and passing through four or more
stuffing boxes in its course; it is moreover hollow, except where it is packed for a
given purpose. On either side of the piston in the condenser the piston rod has
two openings into its hollow centre which communicate with each other, and with
each other only, having stopping beyond. At each end of the cylinder properly
protected by stuffing boxes is a branch of the exit pipe leading to the carriage
cylinders, and the openings into the hollow centre of the piston rod above referred
to are placed at such a distance from each other that the one farthest from the
piston shall come opposite the exit pipe when the air in the cylinder is condensed
to the limit intended. At this point the communication between the two openings
allows the air to rush out of the cylinder into the exit pipe; and as the piston takes
the reverse course the piston rod moves with it and stops all regress of the air so
soon as the brief period of communication is ended. The same occurs at the other
end of the condenser, and each half is alternately filled with a fresh supply of air
and emptied of it. Of course the residual air left in the cylinder after the commu-
nication with the exit pipe is closed becomes gradually rarefied until the piston
moves past the central opening which allows of an inrush from the outer air.
the force required to move the condensing piston become less and not greater with
cach succeeding stroke. Jets of fully condensed air are forced through the exit
pipe until the pressure is equalised. The condenser will fill any number of
reservoirs with condensed air, but is so constructed that the pressure can never riso
beyond a certain point so as to damage the apparatus.
But
The steam cylinder which is in connection with the condenser is very similarly
constructed but is longer; the steam enters at the middle by an opening which is
in communication with the space separating the two heads of the double piston;
this communication is momentarily stopped by a portion of the piston head at the
close of cach stroke, but when it is open the steam finds its way into the hollow
piston rod, by which it is conducted to one or other end of the cylinder so as to act
upon the piston. The piston is moveable to some extent upon the piston rod which,
however, is furnished with a projecting shoulder upon which each piston head can
press so as to carry the piston rod with it. The shifting of the piston upon the
piston rod opens and closes the communication between the interior of the piston
and the two ends of the cylinder respectively, the piston head being arranged to
close over or uncover an opening into the interior of the hollow piston rod by
which the steam gains access. The steam's exit from the cylinder is provided for
by other openings into the hollow piston rod, which come into communication with
the interior of the cylinder at the end of the stroke only when the entrance pipe is
closed by the piston head as mentioned above. Through the openings referred to
the steam is conveyed along the hollow piston rod to its extremity or to other
openings by which it can communicate with the outer air or with the exhaust.
The due shifting of the piston upon the piston rod to which is assigned the respon-
sibility of effecting the change of stroke produced by the re-action of the fluid
compressed by the advancing piston, so soon as the steam on the other side of the
piston loses its force by gaining a vent. To insure a proper amount of re-action,
and yet to obviate too great a pressure within the dead end of the cylinder,
provision is made for egress of the steam during the whole stroke by means of a
very fine channel which is opened up and closed by the shifting of the piston as
aforesaid.
This completes the description, minute enough for present purposes, of the air
apparatus of the brake., It may easily be applied to the system of blocks at present
employed; but where great or long continued brake power is needed it is proposed

page_text: to apply rollers or small wheels to the carrying wheels and to the rails, by means of
levers arranged for parallel motion and moved by connection with the piston rod
belonging to the central cylinder herein-before described. By perfect adjustment
the rollers touch the rails and the wheels at the same instant. They are united in
pairs like the wheels-by-a rigid axle, and are half the diameter of the wheels.
They are made so as exactly to coincide with the tires by being themselves conical,
but in the reverse direction, and the friction between the rollers and the wheels
causes them to rotate in opposite directions, thus greatly increasing the bite upon the
rails. There is a partial flange-descending-from-the_bearings on which the rollers
rotate to prevent them from moving sideways or unduly straining the levers. On
application of this form of brake the carrying wheels are-instantly relieved of a
great portion of their burden, the two pairs of rollers together taking about two-
thirds-of-the-weight_of_the_empty_carriage. Owing to this arrangement the
pressure exerted upon the wheels need be little more than half-what-would
otherwise be required, and it is easy to see what an advantage this is as regards
wear and tear of tires and rails.
The levers for this form of brake worked by the vertical piston rod branch off
fore and aft by carefully adjusted hinge action; they consist of two pairs, the upper
passing directly from the piston rod to the axles of the rollers, the lower parallel
with the upper and starting from the extremities of the transverse arch, which are
in reality the only fixed points in the system of levers, being in rigid connection
with the platforın above. The lower levers join the upper by hinge action at points
between the piston rod and the roller axles somewhat nearer the latter than. the
former. By this arrangement as the piston ascends the rollers are both withdrawn
from the wheels and lifted from the rails. Of course the levers are forked and
strengthened by connecting rods, so as to render their action as nice as possible.