A Graduating Valve for Railway Brakes Worked by Compressed Air.
Year: 1889

page_text: Date of Application, 29th Nov., 1889
Complete Specification Left, 25th Aug., 1390-Accepted, 27th Sept., 1890
PROVISIONAL SPECIFICATION.
A Graduating Valve for Railway Brakes Worked by Compressed Air.
1, ALLAN JOHN CHEW, Assistant Engineer, P.W.D. India, do hereby declare the
nature of this invention to be as follows:-
When railway brakes are worked by compressed air, each brake vehicle is provided
with an auxiliary or storage reservoir, and with a brake cylinder, and there is
necessarily a valve governing the communications of those with each other, with the
train pipe by which the compressed air is conducted along the train, and with an
outlet to the open air.
My invention relates to the construction and arrangement of a valve for this
purpose, whereby the pressure of the brake on the wheels of the vehicle can be
graduated or relieved at will, as I shall explain referring to the accompanying
drawings.
Fig. 1 is a longitudinal section of the valve and casing according to my invention.
Fig. 2 is a side view of the piston valve shewn separately.
Between the auxiliary reservoir situated at R and the brake cylinder situated at C
I interpose the cylindrical valve casing A which is bored to receive the piston slide
valve V Fig. 2 and has ports and passages leading to the cylinder C, o' from the
cylinder to the open air, F communicating with the train pipe, and a relief port p
opening to the air. The piston valve V has an enlarged collar g a groove o a central
hole 6 opening laterally into a groove 62 and passages f opening laterally at one end
to the space behind the collar g, and at the other end to a groove f². The
casing A is for about half its length bored out to fit the collar g and is closed by a
cover B through which there are lateral ports f¹ leading to the reservoir R.
On the end of V is screwed a collar forming a stop against the cover B. The
operation of the valve is as follows:-
When the train pipe is charged with compressed air, the pressure in. the space d
acting on the annular area of the collar g forces V to the right bringing the groove o
to face the ports o' and the groove f to face the ports f' and withdrawing the
groove from 61. Compressed air from F then passes by ff and f¹ into the
reservoir R charging it, while air, if it is under pressure in the cylinder C, can escape
thence by o and of relieving the brake piston from pressure and taking off the
brakes. On reducing the pressure in the train pipe F, the pressure in R pushes the
piston valve V back to the position shewn in Fig. 1, closing f¹ and o' and opening b¹
to b, so that compressed air from the reservoir R flows by b, 62 and 61 into the brake
cylinder C, moving its piston and so putting on the brakes. When the brake cylinder
is thus charged or partly charged the pressure on the one end of V next nearly
balances that on the other end next R so that a variation of the pressure in the train
pipe F acting on the annular area of the collar g can effect a shift of the valve
towards the right, more or less closing 6' and thus varying the pressure in the brake
cylinder C, and consequently the force with which the brakes are applied by the
pressure acting on the brake piston.
Dated thin 90th day of Novembow 1000
ABEL & IMRAY,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
A Graduating Valve for Railway Brakes Worked by Compressed Air.
I, ALLAN JOHN CHEW, Assistant Engineer P.W.D. India, do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
When railway brakes are worked by compressed air, each brake vehicle is provided
with an auxiliary or storage reservoir, and with a brake cylinder, and there is
necessarily a valve governing the communications of those with each other, with the
train pipe by which the compressed air is conducted along the train, and with an
outlet to the open air. My invention relates to the construction and arrangement of
a valve for this purpose whereby the pressure of the brake on the wheels of the
vehicle can be graduated or relieved at will, as I shall explain referring to the drawings
accompanying my Provisional Specification.
Fig. 1 is a longitudinal section of the valve and casing according to my invention.
Fig. 2 is a side view of the piston valve shewn separately.
Between the auxiliary reservoir situated at R and the brake cylinder situated at C
I interpose the cylindrical valve casing A which is bored to receive the piston slide
valve V Fig. 2 and has ports and passages leading to the cylinder C, o¹ from the
cylinder C to the open air, F communicating with the train pipe, and a relief port p
opening to the air. The piston valve V has an enlarged collar ga groove o a central
hole 6 opening laterally into a groove 62 and passages opening laterally at one end
to the space a behind the collar g, and at the other end to a groove f2. The casing A
is for about half its length bored out to fit the collar g and is closed by a cover B
through which there are lateral ports f¹ leading to the reservoir R.
On the end of V is screwed a collar v forming a stop against the cover B. The
operation of the valve is as follows:-
When the train pipe is charged with compressed air, the pressure in the space d
acting on the annular area of the collar g forces V to the right bringing the groove 0
to face the ports o¹ and the groove to face the ports f' and withdrawing the
groove 62 from 61. Compressed air from F then passes by ff2 and f¹ into the
reservoir R charging it, while air, if it is under pressure in the cylinder C can escape
thence by o and o¹ relieving the brake piston from pressure and taking off the brakes.
On reducing the pressure in the train pipe F, the pressure in R pushes the piston
valve V back to the position shewn in Fig. 1, closing f1 and o¹ and opening to b,
so that compressed air from the reservoir R flows by b, 62 and 1 into the brake
cylinder C, moving its piston and so putting on the brakes. When the brake cylinder
is thus charged or partly charged the pressure on the one end of V next C nearly
balances that on the other end next R so that a variation of the pressure in the
train pipe F acting on the annular area of the collar can effect a shift of the valve
towards the right, more or less closing 6' and thus varying the pressure in the brake
cylinder C, and consequently the force with which the brakes are applied by the
pressure acting on the brake piston.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is.
A graduating valve for railway brakes consisting of the combination with the
casing A having passages and spaces, b, d, o¹, f and p, and air pressure inlet F, of
a piston slide yalve V having collar g and passages and spaces b, f, b³, ƒ³, o, so
arranged and operated in connection with the reservoir at R and the brake cylinder
at C, that on the discharge of pressure from the brake pipe F the valve is moved so
as to establish the communication between the reservoir and the brake cylinder,
while on admitting air pressure through the brake pipe, the valve is moved so as to
cut off the communication between the reservoir and brake cylinder, and establish the
communication between the former and the brake pipe, the position of the valve for

page_text: graduating the pressure in the brake cylinder being determined by the combined
pressures upon the end of the valve next the brake cylinder and upon the collar.g
operating against the pressure in the reservoir substantially as herein described.
Dated this 25th day of August 1890.
ABEL & IMRAY,
Agents for the Applicant.