Improvements in Automatic Vacuum Brakes
Year: 1893

page_text: Date of Application, 1st Sept., 1893-Accepted, 7th Oct., 1893
COMPLETE SPECIFICATION.
Improvements in Automatic Vacuum Brakes,
I, HENRY ARTHUR LIVOCK, of 116 Palace Chambers, Bridge Street,
Westminster, in the County of Middlesex, Civil Engineer, 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 :-
My invention relates to improvements in the well known vacuum automatic brake
as applied to railways.
In certain forms of vacuum brakes as used in this and other countries, in a
vertical cylinder having a piston and rod attached for the purposes of actuating
the brake rigging, the piston rod passes through a stuffing box provided with a
suitable rubber gland ring, which, owing to the continual movement of the piston,
is liable to excessive wear and consequent leakage. When the brakes are in their
normal position, that is to say, off. the piston rests at the bottom of the cylinder,
and the action of the ejector, which is used for the purpose of exhausting air out of
the cylinder, pipes, &c., is rendered less effective by the leakage of air past the
aforesaid gland, thereby causing an excessive consumption of steam and difficulty
in maintaining the vacuum.
My invention consists in the provision of a rubber ring placed round the piston
rod and close up against the piston, and of an annular iron or other metal ring with an
annular raised surface of V section secured to the bottom of the cylinder as shown.
The rubber ring may be cemented to the piston to make a better joint. The effect
of this is that when the piston is at its lower position the rubber ring is in contact
with the iron ring and forms an air tight joint, consequently when in this position
no leakage of air can take place past the piston rod gland and the vacuum is more
easily maintained.
In order that my invention may be better understood and more readily carried
into effect I will proceed to describe the drawing hereunto annexed.
The same letters refer to the same parts or substitutes therefor in the several
figures of the drawing.
Figure 1 is a sectional elevation through the brake cylinder.
Figure 2 is an enlarged section of a portion of the piston rod and bottom of the
cylinder.
Figure 3 is an enlarged section of a portion of the piston rod and bottom of the
cylinder, showing an alternative method of making the joint.
a is the outer cover or vacuum chamber, b is the cylinder, c is the piston, d is the
bottom of the cylinder, e is the piston rod, f is the gland ring, is the annular ring
of indiarubber, is the annular ring of metal, and is the V shaped projection.
The end k is connected to the train brake pipe and to the ejector on the engine.
is the usual valve provided for working the brake.
The action consists that the air is exhausted from the chamber a and cylinder b
and at the same time through the passage m from the under side of the piston c.
The piston being thus in equilibrium falls by its own weight to the bottom of the
cylinder.
It will be seen that if the gland f is not air tight a considerable leakage of
air will take place past it and the space between the piston rod and the bush n,
thereby causing a difficulty in maintaining the vacuum.
The interposition of the rubber ring g with or without the addition of the metal
ring makes an air-tight joint between the piston and the cylinder cover, and
thereby prevents the leakage described above.
It is obvious that although I have described in this Specification a rubber
ing as being more convenient yet a soft metal ring may be used if desired.

page_text: It is possible of course to vary the arrangement by varying the positions of the
rubber and metal rings respectively, that is to say, that the rubber ring may be
placed below and the metal ring above, instead of as illustrated. A further
alternative would be to construct the upper portion of the cylinder bottom d or the
brass bush n with a V shaped projection, in lieu of adding it separately in the form
of a ring, or the metal ring may be left out altogether and the joint made direct
with the rubber ring as shown in Figure 3.
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 cylinders for automatic vacuum brakes, the provision of an indiarubber
ring for preventing the ingress of air into the cylinder and pipes during the
working of the brake, substantially as described and as illustrated in the drawing
annexed.
2. In cylinders for automatic vacuum brakes, the combination of the rubber ring
and the metal ring, for the purpose of preventing the ingress of air into the cylinder
and pipes during the working of the brake, substantially as described and as
illustrated in the drawing annexed.
Dated this First day of September 1893.
JOHN P. O'DONNELL,
70 & 71, Palace Chambers, Bridge Street, Westminster, London, S.W.,
Agent for said Applicant.