Improvements in Relief Valves for Automatic Steam or Air Brakes for Railway Cars.
Year: 1888

page_text: Date of Application, 17th Sept., 1888
Specification Accepted, 26th Oct., 1888
Improvements in Relief Valves for Automatic Steam or Air Brakes
for Railway Cars.
I, CHARLES TURNER BROWN, residing at Indianapolis, in the county of Marion,
State of Indiana, United States of America, Engineer, do hereby declare the nature
of my invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
In order to render the invention clear I will first briefly describe the present air
brake apparatus, or one of them, most largely in use.
The air compressing pump is located upon the engine and is under the immediate
control of the engineer. Air is compressed into a main accumulator or receiver and
from that is distributed through suitable train or air pipes c to an auxiliary receiver A
under each car of the train. The triple valve B is placed in said air pipe. Its office
is to permit the air under pressure to enter slowly into said auxiliary reservoir until
the pressure therein equals the pressure in the main reservoir, upon any diminution
of pressure in the conducting pipe c. The then superior back pressure in the
auxiliary A will cause the triple valve to open and admit air to flow from said
auxiliary into the air brake cylinder to operate the brake.
To produce this effect a valve is placed in said air pipe convenient to the hand of
the engineer whereby the communication with the main reservoir is cut off at the
same moment that it opens an escape for air within said pipe between the triple valve
and the engineer's valve. Escape of air from the air pipe relieves pressure therein,
and sets up back pressure in said auxiliary reservoir, and the triple valve is thereby
actuated as set forth. The engineer usually moves his valve slowly so as not to
permit sudden movement of the triple valve, but sometimes he fails to be sufficiently
skilful or sufficiently cautious, and sometimes the escape of air from the pipe is the
result of accident. Sometimes also by reason of improper working of the pump
governor, or other cause the engineer suffers the air to be forced into the reservoir
with a pressure too high, so that, when the brake is operated it will be with too much
pressure of the brake shoes, and arrest of the revolution of the wheels. This is highly
objectionable because the tread of the wheel is flattened by sliding on the rail, and
the wheel rapidly spoils after that.
Also when the brakes have all been set, and it is desired to let them off, air is let

page_text: into the air pipe c under reservoir pressure, but it frequently happens from the length
of the train and other causes that the triple valves do not act with desirable promptness
in releasing and discharging the brake cylinders. My invention has for its object to
prevent the objectionable results arising from overpressure or tardy release by
providing a simple device which, if desired, can be applied as an attachment
conveniently and at small cost to brake cylinders now in use, and which will be very
sensitive, prompt and efficient in action.
Figure 1 is a perspective view of an auxiliary reservoir and the brake cylinder with
the triple valve and the connecting pipes, having my invention applied.
Figure 2 is a longitudinal section of my automatic relief valve.
Figures 3 and 4 represent modifications. D is the brake cylinder, having within it
a piston e, and retracting spring f, which tends to force said piston toward one end
of the cylinder and thereby retract the brakes. When air under pressure is admitted
behind said piston the spring is overcome and the brakes are forced against the
wheels.
My relief valve E opens inward as to the cylinder and is applied to the brake
cylinder by boring through the head of the same and by screwing the end of the
valve case in there. The outer end of the valve case connects with the air pipe and
is subjected to air pipe pressure.
Pressure within the cylinder tends to close the valve, and pressure within the air
pipe tends to open it, but said valve may he adjusted to balance between these two
forces at any desired pressure. and will then stand open when the preponderance of
pressure is in the air pipe, and will stand closed when the preponderance of pressure
is in the cylinder. When open, it provides free escape for air which enters the
cylinder from the auxiliary reservoir under too great pressure, and said escape
continues until the pressure has run down to the desired standard, and therefore
renders it impossible to apply to the brake pressure sufficient to lock the wheels and
make them slide.
The valve E fits a proper seat p in the valve case, and is provided with wing guides
to keep it straight and allow free passage for air past it when open. The valve
stem is rigidly attached at one end to said valve and at the other end it is provided
with a piston which may be sliding or diaphragm, and it is subjected to air pipe
pressure and tends to keep the valve off its seat, while cylinder pressure, if there is
any, tends to close it upon its seat. In order to make these forces balance at
different pressures, as desired, the valve is made with smaller area than the piston
and a spring is applied to resist the movement of the piston, so that supposing the
valve and piston to be subjected to the same pressure, the smaller effect, on the valve,
may be made up by the tension of the spring so as to balance the larger effect on the
piston. For instance, supposing the valve and piston areas to be as 4 to 5 and the
tension of the spring to be 1, the valve and piston will balance when the tension of
the spring is one-fifth the air pressure, and by varying the tension of the spring the
valve and piston may be made to balance at a high or low pressure as desired. The
valve case is provided with holes 1 for the escape of air which passes the valve.
k
It will be understood that the structure shown and particularly alluded to may he
greatly varied without changing its principle of operation or the effects produced.
The spring may be constructed and the valve case and piston rod may be designed
so that said spring will, when in place be subjected to a certain standard pressure,
adapted to the standard air pressure preferred, but no change can then be made in said
standard without removing the springs and putting others in place. I therefore prefer a
structure which will permit a change of spring tension whenever desired. This may
be accomplished in a variety of ways well known to mechanics, but in my experiments
I have found it convenient to make the change in tension without taking the apparatus
apart and have therefore made the case in two parts screwed together as at m, and
therefore easy to shorten or lengthen. One part has the spring shoulder n, and the
other part has the valve seat. As the valve stem is not extensible it follows that to
increase the distance between the spring shoulder and valve seat will increase the
tension of the spring.

page_text: A jam nut serves to prevent unintentional change in the relative position of the
two parts of the valve case.
The operation is as follows:-
Supposing the desirable pressure in the auxiliary reservoir to be 80 pounds per inch
but that the actual pressure in air pipe and auxiliary has accumulated to 100 pounds
per inch. There would then be an excess of 20 pounds over the piston i and the
valve would remain open if air at 100 pounds were admitted to the brake cylinder
until the air pipe and auxiliary pressure has run down to 80 pounds at which point
the valve and piston will balance, and the valve will close the instant the air pipe
pressure falls below 80 pounds.
When it is desired to let off the brakes it is frequently found that the "triple"
valve by reason of its delicacy and liability to obstruction by slight causes, does not
work promptly, and the brakes are not quickly released. This difficulty is overcome
by my valve which is forced open immediately when the air pipe is filled again at
maximum pressure, and the cylinder exhausts independent of the triple valve.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In combination with the automatic brake operating devices the construction of
relief valve substantially as herein set forth.
2. In an automatic air brake apparatus the combination with the brake cylinder,
the auxiliary reservoir, the triple valve, and the main air supply pipe, of a valve case
having a valve seat and applied to and communicating with said cylinder, a valve in
said casing and opening inwardly into the brake cylinder, a piston of larger area
than the valve and connected positively and moving with the same in said case, a
spring for moving the cylinder and valve to close the latter, and a pipe or air duct
connecting the said air supply pipe with the valve case on the outer side of the piston,
substantially as described.
3. In an automatic air brake apparatus for railway cars and in connection with
the brake cylinder thereof the auxiliary reservoir, and the triple valve, a valve E
arranged to open inwardly as to said cylinder, a spring arranged to close said valve
upon its seat, and a piston in line with and secured rigidly to said valve, and a
connection with the air or train pipe communicating with the latter between the triple
valve and the engineers valve whereby when the air pressure in said train pipe
exceeds the standard maximum pressure for the brake cylinder, said valve will be
kept open, for the purpose set forth.
Dated this 3rd day of September 1000.
CHARLES TURNER BROWN.
Herbert & Co.,
18, Buckingham Street, Strand, London, W.C.,
Agents to Applicant.