Improvements in Pueumatic Tyres for Cycle and other Wheels.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Pueumatic Tyres for Cycle and other Wheels.
I DOUGLAS ALLPORT of 108 Queen Victoria Street, London, Merchant, do hereby
declare the nature of this invention to be as follows:-
My invention consists in the use of a compressible chamber connected with or
contained in the hollow tyre, having one or more inlet valves for air on the outside
& one or more outlet valves into the hollow of the tyre. The compression of this
chamber, when the weight comes on or is put upon it, will force some of the contained
air into the tyre through the outlet valve. When by revolution of the wheel the
compression is removed, the chamber will spring back to its normal shape, causing &
partial vacuun, which will be filled by the outer air passing thro' the inlet valve.
This will be repeated with each revolution of the wheel until the pressure in the tyre
equals the pressure in the chamber.
I DOUGLAS ALLPORT of 6 Newton Grove, Bedford Park, Chiswick, Merchant
(lately of 108 Queen Victoria Street E.C.) do hereby declare the nature of this invention
and in what inunner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
My invention designs to provide automatic inflation for pneumatic tyres by utilizing
the pressure and consequent depression of the tread of the wheel when in use.
This I effect by means of a compressible chamber of india rubber contained in the
inner tube (or single tube as the case may be) of the tyre and forming part of it.
This chamber is connected both with the outer air and with the hollow of the tube,
and when compressed by contact with the ground, its contained air is partly expelled
into the tube, through a suitable outlet valve. On regaining its shape, which it
does by reason of the internal air pressure distending the tube to which it is
attached, atmospheric air flows through tho inlet and fills the chainber ready for the
next compression. For the purpose of deflation and to guard against possible over-
pumping, a safety valve is provided.
The drawings will explain the nature of the appliance. Fig. 1 shows a longitudinal
section of the part of the tube containing the pumping arrangement. Fig. 2 shows
n cross section of the same. a is the air chamber, the inlet tube, a the outlet
valve. d is a block of india rubber forming the upper side of the chamber, between
which and the tread of the tyre the pressure is brought to bear upon the chamber.

page_text: ee are cylindrical cavities in the block for regulating its elasticity. They may be
plugged if it is desired to increase its rigidity. The inlet tube 6 connects the
chamber a with the external air through an attachment f, which may have a filtering
substance, such as cotton wool, in its upper part to exclude dust. It is fitted with a
nipple for inflation in the ordinary way when necessary, (as before use or after
dellation). This nipple is covered by a removeable cap which can be loosened for
the admission of air when the machine is in use, and tightened to prevent the
possibility of leakage when out of use. is the outlet leading to the safety valve h.
These two parts and h are not shown in detail as they do not form integral parts
of my invention and are simple to construct. Thoy form attachments for the
block d to the rim, and their method of fixing is similar to that adopted in the case
of ordinary valves and well understood in the cycle trade. The outlet valve c is
shown as a short tube in continuation of the air chamber u. A smooth tapered plug k
of vulcanite or other material is inserted in this outlet and secured in its place by a
small pin passing through it and the sides of the valve tube. The compressed air
from the chamber is forced past this plug, the sides of the valve c being distended
as it passes, and closing again on the plug when it has passed, the pressure of the
air in the tyre keeping it tight. This form of valve is efficient but I do not confino
myself to its use. Two projecting ridges M M are shown on the inner surface of the
chamber at the inlet end. These ridges come under compression earlier than the
chamber, bear tightly upon each other, and assist in preventing the escape of air
from the chamber except in the forward direction, through the valve c. Any suitable
form of inlet valve may, however, be used in place of mm.
In my drawings I have shown the chamber a at the lower extremity of the block (.
I believe this to be the best position for it, but I do not confine my invention to this
arrangement, as it is obvious that a similar chamber in the middle or upper part of
the block would still be operated upon to some extent by pressure on the tread.
Nor do I limit the shape of the block d to that shown in the drawings, although I
believe it to be approximately the best. And the air chamber a may be varied in
shape and size, particularly as to its length.
I am aware that bags and pouches enclosed in pneumatic tyres for purposes of
inflation are not novel, but such as have beon projected hitherto could not succeed
because their projectors have not recognized that a pressure of at least 30 lbs. to the
square inch must be produced in the pump or chamber in order to overcome the
pressure on the outlet valve from the other side. This minimum pressure can only
be obtained by reducing the chamber when under pressure, to about one third of its
normal capacity, and eo far as I am aware, this has been impossible by any of the
methods suggested unless the tyre were deflated altogether and the rims brought to
the ground. In my invention the chamber is formed in such a way that a depression
of only a quarter of an inch in the tyre produces the power necessary. The chamber
is practically collapsed and emptied by the minimum depression usually produced in
riding a well-pumped tyre.
Another point which has been overlooked in former inventions for this purpose, is
the fact that an enclosed bag or chamber, surrounded by compressed air at 30 lbs. to
the inch, would not expand after compression, but would remain flattened and fail to
draw in any further supply of air. The form adopted in my invention provides for
the due expansion of the chamber by reason of its complete attachment to the tube
at the tread and also (through the intervention of the block d) to the opposite part.
Although the block and chamber are enveloped in air under pressure in the tube on
the two sides, the pressure is employed to pull the top and bottom of the chamber
apart in restoring the cylindrical shape of the tube of which it forms a part.
Having now particularly described and ascertained the nature of my said Invention,
and in what manner the same is to be performed, I declare that what I claim is:-
1. I claim an arrangement such as that shown in the drawings and above described,
whereby a small air chamber is introduced into the pneumatic tube of a cycle or

page_text: other wheel, in such a manner as to ensure its being completely flattened by the
ordinary pressure upon the tread of the wheel, even with a fully pumped tyre.
2. I claim the method of securing the full expansion of the chamber after
compression by attaching it to the top and bottom of the pneumatic tube,
substantially as described.
3. I claim the general arrangement of parts as described, for the automatic
inflation of pneumatic tyres.