IMPROVEMENTS IN BRAKE CYLINDERS
Year: 1880

page_text: LETTERS PATENT to John Audley Frederick Aspinall, of Inchicore, Dublin, in
the County of Dublin, Engineer, for an Invention of "IMPROVEMENTS IN
BRAKE CYLINDERS."
PROVISIONAL SPECIFICATION left by the said John Audley Frederick
Aspinall at the Office of the Commissioners of Patents on the 8th May 1880.
JOHN AUDLEY FREDERICK ASPINALL, of Inchicore, Dublin, in the County of
Dublin, Engineer. "IMPROVEMENTS IN BRAKE CYLINDERS."
These improvements relate especially to brake cylinders of a similar shape to
those described in my Specification of Patent dated 7th November 1878, No. 4521.
According to this present Invention I make the flexible part of the diaphragm
or piston in such a way that it is divided into two parts. One part is connected to
one side or part of the cylinder, and the other to the opposite side of the cylinder.
Both sides of the cylinders are connected rigidly together, but the atmosphere is
allowed free access to the space between (or what may be terined the outer surfaces
of) the double portion of its diaphragm.
I make one such side or part of the diaphragm of larger diameter than the other,
in such manner that when a vacuum is formed in its cylinder in the usual way the
pressure of the atmosphere acting upon the aforesaid outer surfaces of the flexible
part of the diaphragm tends to keep the side having the largest diameter pressed
against that side of the cylinder which is nearest to it. I thus ensure a tendency
on the part of the brake to keep off as long as a vacuum is maintained in the
pulling, usually the lower side, of the cylinder. When however the vacuum is
destroyed in the lower part of the cylinder in order to apply the brakes the
atmosphere presses equally on both sides of the lower flexible part of the diaphragm,
and this part being in equilibrium does not in any way tend to take the brake off
until a vacuum is once more formed in the lower half of the cylinder;
atmosphere acting with its full pressure on the larger or lower flexible part of the
diaphragm will then materially assist the action of the said vacuum, and cause the
brake to be taken off with greater force or rapidity.
the
The atmosphere may be made to enter the space between the double portion of
the diaphragm through holes in a ring placed between them at the place of
connection to the two parts of the cylinder.
This Invention is also applicable to other brake cylinders than those referred to
above.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Audley Frederick Aspinall in the Great Seal Patent Office
on the 8th November 1880.
JOHN AUDLEY FREDERICK ASPINALL, of Inchicore, Dublin, in the County of
Dublin, Engineer. "IMPROVEMENTS IN BRAKE CYLINDERS."
These improvements relate especially to brake cylinders of a similar shape to
those described in my Specification of Patent dated 7th November 1878, No. 4521.
According to this present Invention I make the flexible part of the diaphragm or
piston in such a way that it is divided into two parts. One part is connected to
one side or part of the cylinder, and the other to the opposite side of the cylinder.
Both sides of the cylinders are connected rigidly together, but the atmosphere is
allowed free access to the space between (or what may be termed the outer surfaces
of) the double portion of its diaphragm.
I make one such side or part of the diaphragm of larger diameter than the other,
in such manner that when a vacuum is forined in its cylinder in the usual way the
pressure of the atmosphere acting upon the aforesaid outer surfaces of the flexible
part of the diaphragm tends to keep the side having the largest diameter pressed
against that side of the cylinder which is nearest to it. I thus ensure a tendency
on the part of the brake to keep off as long as a vacuum is maintained in the
pulling, usually the lower side, of the cylinder. When however the vacuum is
destroyed in the lower part of the cylinder in order to apply the brakes the
atmosphere presses equally on both sides of the lower flexible part of the diaphragm,
and this part being in equilibrium does not in any way tend to take the brake off
until a vacuum is once more formed in the lower half or part of the cylinder; the
atmosphere acting with its full pressure on the larger or lower flexible part of the
diaphragm will then materially assist the action of the said vacuum, and cause the
brake to be taken off with greater force or rapidity.
The atmosphere may be made to enter the space between the double portion of
the diaphragm through holes in a ring placed between them at the place of
connection to the two parts of the cylinder.
This Invention is also applicable to other brake cylinders than those referred to
above.
Figure 1 of the accompanying Drawings is a vertical contral section through a
brake "cylinder" similar to those described in my aforesaid Patent Specification, but
with my present improvements applied thereto; Figure 2 is a part plan showing
the flange which unites the two halves of the "cylinder."
The flexible part of the diaphragın or sack or piston is made in two parts A
and A', the former A having a larger acting area, and being connected to the
Hange 6 of the lower part or side B of the cylinder, and the latter A¹ having a
relatively smaller diameter, and being connected to the flange b' of the upper part
or side B' of the cylinder.
The outer air is by means of holes & through the ring D constantly admitted to
the intermediate space a between the two parts A and A¹ of the sack, but owing
to the aforesaid difference in their diameter the total air pressure is greater on tho
part A than on the part A'. This excess pressure thus ensures a tendency on the
part of the brake to keep off while a vacuum is maintained in the pulling side, in
this case the bower side or part B, of the cylinder. When the vacuum is destroyed
in the part B the piston C will be raised, and the brakes will be applied. While
the brakes are thus on there is atmospheric pressure in the lower part B, as well
as in the space a, hence the flexible part A is in equilibrium and has no tendency
to take the brakes off, but as soon as a vacuum is once more formed in the lower
part B the air pressure in a acting on the larger area of the flexible part A will

page_text: materially assist the action of the said vacuum, and cause the brakes to be taken
off with greater force or rapidity.
The double formation of the sack possesses a collateral advantage in that it
about doubles the "life" or wear of the sack; these sacks have heretofore some-
times given way at the point a¹, but owing to the inequality of the areas of A
and A, the leather A is exposed to greater occasional strains than the leather A¹,
and in case of the leather A giving way the leather A¹ will act as a reserve and
prevent a failing of the brake. In case one of the parts A or A' should fail the
holes & through the ring D can be plugged up, or the ring D removed altogether,
when the apparatus will work like an ordinary sack, as described in my said
Specification, No. 4521, of 1878.
And having thus described and ascertained the nature of this Invention and
how the same is or may be carried into effect, I declare that I claim,-
Forming the flexible portion of the sack or piston in two parts of unequal area
for the atmospheric air to act on the larger area, so as to ensure a tendency of the
brakes to keep off as long as a vacuum is maintained in the pulling side or portion
of the brake cylinder, and so as also to assist in taking the brakes off, when a
vacuum is reformed in the said pulling side of the brake cylinder, and also generally
to increase the "life" or wear of the sack.
In witness whereof, I, the said John Audley Frederick Aspinall, have hereunto
set my hand and seal, this Sixth day of November, in the year of our Lord
One thousand eight hundred and eighty.
•
JOHN A. F. ASPINALL. (L.S.)