Improvements in the Construction of Pneumatic Tyres.
Year: 1891

page_text: Date of Application, 22nd Aug., 1891
Complete Specification Left, 10th May, 1892-Accepted, 25th June, 1892
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Pneumatic Tyres.
I THOMAS DUNN of 83 Tierney Road Brixton Hill in the County of Surrey
Member of the Stock Exchange do hereby declare the nature of this invention to
be as follows:
-
The primary object of my invention is, to render pneumatic tyres capable of
withstanding puncture by nails or other sharp or pointed obsticles met with on the
roads; and the special merit I claim for it is, that it does this in such a way that,
instead of the ease of running of the tyres being impaired thereby, as it is by all
the processes for the purpose yet tried that I know of, the tyres by my invention
are at the same time improved in ease of running & resiliency.
One method that has been devised to protect the air-tubes of pneumatic tyres
from puncture is, to insert in the layer of indiarubber with which they are usually
covered, a strip of some hard material such as steel or parchment. But, however
flexible a steel ribbon may be when free, when buried in the rubber coating of the
tyre, & thereby prevented from bending outwards at any point, it must, on the well
understood principle of the suspension wheel, offer very considerable resistance to
compression at the point of contact with the ground, whereby the resiliency of the
tyre must be seriously impaired. If such a band is at all curved in its breadth, it
is obvious that its stifness to resist compression at the point of contact with the
ground, & the extent to which it would consequently impair the resiliency of the
tyre, would be greatly increased. The stifness of such a band is largely removed
if, instead of steel, it is made of a less hard substance such as parchment, which has
the capacity, under slight pressure, to undergo slight contraction in its length.
The lesser hardness necessarily belonging to such a material however, prevents it
from being absolutely impuncturable, and, although the use of such a material
would not be inconsistent with the principle of my invention, I prefer instead to
render the hard band easily compressible when buried in the substance of the
tyres, by making it of a number of short pieces, instead of one continuous band,
& I make these pieces overlap one another slightly, lest puncture should take place
between them, the overlapping being in that way that, in the front of the wheel,
the upper edge of each short piece overlaps the lower edge of the one next above:
then, since the revolution of the wheel is practically constant in a forward direction,
no sharp or pointed obsticle met with on the road can ever by forced under the
upper edge of the plates which is thus exposed, but would rather slide over it on to
the next plate; consequently the airtubes are thus perfectly protected from
puncture. Though the flexibility of such a band made up of short pieces, would
not be perceptibly impaired by curving it in its breadth, it is obvious, if it were so
curved, that a serious amount of friction would take place, on flexion of the tyre,
between the sides of the band & the surfaces of the materials of the tyre in contact
with it, and that, only by having a layer of any hard substance inserted in a tyre
perfectly flat, and as thin as possible, can it be kept as flexible as possible in itself,
and can friction with the surfaces of the materials of the tyres in contact with it be
kept at a minimum. This then is the fundamental principle of my invention :-to
protect the air-tubes of pneumatic tyres, by covering them, over a sufficient breadth,
with a thin layer of hard material, such as sheet or ribbon steel, which shall be flat
as seen in the cross section of the tyre; and its secondary principle is, to make this
layer or band of short pieces, overlapping each other as described; & I make each
piece extend across the whole breadth of the band, so that no flexion should take
place in its breadth, as this would impair its inflexibility & involve friction as
described. Such a flat band however is of a very unsuitable shape to constitute a

page_text: running surface for the tyre, even if covered with indiarubber or any other material,
if the covering was of the same thickness throughout, so that its exterior was also
flat. I therefore cover the band with a strip of indiarubber or other flexible
material, flat on the side next the band, but convex on the other side; the convexity
corresponding with the form of the tyre, whereby I retain the circular form of its
exteriors. In making up the tyres according to this plan, I press the hard band,
with the plano-convex strip on the outside of it, on the partially inflated airtubes,
till they are flattened out over the whole of the under surface of the flat-band.
The band and rubber strip are then kept in this position, by the covering with
which the airtubes are enclosed, to restrain the expansion of the compressed air in
them and prevent their bursting, being passed over them; and thus, when the tyres
are fully inflated for use, the rubber band is constantly subject to the pressure of
the compressed air in the air-tubes, & no further compression of it takes place at
the point of contact with the ground, whereby all the loss of power, which would be
involved in such compression, is avoided. This loss of power necessarily occurs
when tyres are covered with a layer of elastic rubber outside the canvas tube
usually employed to strengthen them, and not under pressure, and constitutes, in
my opinion, one of the greatest objections to the present construction of pneumatic
tyres. By thus covering the flat band by a plano-convex strip, the tyre is given a
running surface of practically constant breadth, and always narrow, whereby road
friction is reduced to a minimum.
Finally, the hard band enables a lower air pressure in the air-tubes, to be equally
efficient, as a much higher pressure otherwise would be, in supporting the weight of
the rider & machine, since compression of the air-tubes, on contact of the tyre with
the ground, instead of being confined to the narrow point of contact, is extended
over the whole breadth of the flat band. So great do I believe the advantages of
this plan to be, not only in rendering puncture impossible, which is its primary
purpose, but in reducing road friction, & increasing the resiliency of the tyre, in
proportion to the degree of the air pressure in the air-tube, that I believe it will be
found advantageous to employ it, even in the tyres of machines intended exclusively
for use on racing tracks, though these tyres do not require to be protected from the
risk of puncture, & notwithstanding the additional weight involved by its introduc-
tion into these tyres, which it is desirable to keep as light as possible. By the use
of this plan, I believe too, that it will become practicable to make pneumatic tyres
of such strength & durability (probably by using leather as a binding material, &
perhaps also as an exterior covering to bear the wear of road friction) that they
may with advantage be employed on the wheels of all light fast running vehicles,
instead of their use, as hitherto, being confined to bicycles & tricycles; and I
believe that such pneumatic tyres could be made cheaper than the solid rubber
tyres now used on carriage and cab wheels, owing to the great weight of rubber
contained in these tyres, and its high cost.
Dated this Twenty-second day of August 1891
THOMAS DUNN.
COMPLETE SPECIFICATION.
Improvements in the Construction of Pneumatic Tyres.
I, THOMAS DUNN of 83 Tierney Road, Brixton Hill, in the County of Surrey,
Member of the Stock Exchange, 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 has for its object to prevent the air tubes of pneumatic tyres being
punctured by nails or other sharp or pointed obstacles met with on roads, and at
the same time to improve the resiliency and ease of running of such tyres,
instead of impairing these qualities as in the constructions heretofore adopted for
this purpose.

page_text: It has heretofore been proposed to protect the air tubes of pneumatic tyres from
puncture by inserting a plain strip or band of some hard material such as steel or
parchment in the layer of india rubber with which they are usually covered. But
however flexible a band of steel may be when free, when embedded in the india
rubber covering of the air tube and thereby prevented from bending outwards at
any point, it must on the well understood principle of the suspension wheel, offer
very considerable resistance to compression at the point of contact with the ground,
thereby seriously impairing the resiliency of the tyre. If such a strip or band is
at all curved in its breadth, it is obvious that its stiffness to resist compression at
the point of contact with the ground, and the extent to which it would consequently
impair the resiliency of the tyre, would be greatly increased. The stiffness of a
plain band is largely removed if, instead of steel, it be made of some less hard
substance such as parchment, which is capable under sliglit pressure, of undergoing
slight contraction and expansion in its length. Owing however to the lesser
hardness necessarily belonging to such a material, it is not a perfect protection
against puncture of the air tube by articles such as mentioned, although the use of
such a material suitably employed as hereinafter described, would not be inconsistent
with the principle of my invention.
According to my invention I render the hard band capable when enclosed in the
substance of the tyre, and while the tyre is rolling and supporting a load, of readily
undergoing slight compression or contraction and expansion or increase of length
by making it of a number of short pieces of hard material such for example as
steel, instead of in one continuous plain band. These pieces, hereinafter called
plates, may advantageously be arranged to overlap one another slightly to prevent
puncture taking place between them, the overlapping being effected in such a
manner that at the front of the wheel the upper edge of each plate overlaps the
lower edge of the plate next above. By this construction since the revolution of
the wheel is practically always in a forward direction, no sharp or pointed obstacle
met with on the road can ever be forced under the upper edge of any of the plates,
but would rather slide over such edge on to the next plate, consequently the air
tube will thus be effectually protected from puncture. Though the flexibility of
such a band (hereinafter called the protecting band) made up of short pieces would
not be perceptibly impaired by curving it in its breadth, it is obvious that if it were
so curved, a serious amount of friction would take place, on flexion of the tyre,
between the sides of the protecting band and the surfaces of the materials of the tyre
in contact with it, and that only by having a layer of any hard substance inserted in
a tyre, perfectly flat and as thin as possible, can it be kept as flexible as possible
in itself, and can friction with the surfaces of the materials of the tyres in contact
with it be kept at a minimum. I therefore make each of the plates of hard
material, straight or flat as seen in a cross section of the tyre and of the full width
of the protecting band. To provide a good running surface for the tyre I cover
the protecting band with a strip of flexible material, for example india rubber,
that is flat on the inner side next the band, and convex on the other or outer
side, the convexity corresponding, or approximately so, with the curvature of the
sectional form of the tyre in order to retain the normal circular external form
of such tyre. When making up a tyre according to this invention, the protecting
band surrounded by the plano-convex strip of india rubber is pressed upon the
partially inflated air tube so as to flatten the surface of this tube over the whole
breadth of the protecting band. The protecting band and flexible strip are then
kept in this position by the tough covering with which the air tube is usually
enclosed to restrain the expansion of the compressed air within it and prevent
its bursting. The tyre is then completed with a covering of suitable material
such as india rubber according to any approved method.
. In the accompanying drawings,
Fig. 1 is a cross section of a pneumatic tyre constructed according to this
invention.

page_text: rigs. 3 and 4 are developed views shewing the protecting band in elevation and
longitudinal section respectively.
Fig. 5 is a cross section illustrating a modified construction.
Referring to Figs. 1 to 4 inclusive, 1, 1 are pieces of metal as for example steel,
that are practically straight or flat in cross section. These plates are rivetted to
an endless strip 2 of flexible material such as canvas to form a continuous band and
are arranged to overlap each other as shewn in order to form a hard but flexible
protecting band for the air tube 3 upon which it is so placed as to flatten this tube
on the outer periphery as shewn at 4. The plates when of steel may advantageously
have a thickness of about No. 1 Birmingham metal gauge. 5 is a strip of india
rubber surrounding the flat protecting band, and of plano-convex form in cross
section. 6 is an outer covering of tough flexible material as for examples prepared
canvas such as is ordinarily used to prevent undue expansion of the air tube.
This covering is arranged to surround the strip 5 and protecting band 1 as shewn.
The tyre is finally covered with a layer of suitable material such as india rubber or
is coated with such material as to render it waterproof and protect it from wear in
any of the usual approved ways. The complete tyre may be secured on the wheel
rim 7 in any known or suitable manner as well understood.
In Fig. 5, the outer covering 6 of prepared canvas forms in conjunction with a
strip of canvas 3ª, the edge portions of which are cemented thereto, the wall of the
air tube or chamber 3, the inner side of the covering being coated or lined with a
thin layer of india rubber to render it air tight. In making up such a tyre, the
strip 3ª, protecting band, and flexible strip 5 are placed in the order mentioned
upon a mandril forming part of a circular ring having the same diameter as the
tyre to be produced and a cross section corresponding to that of the air tube
when inflated, and around the whole the outer covering 6 of prepared canvas in
the form of a strip of rubber is wound spirally. When a portion of the tyre has
thus been made, it is drawn off the mandril and a fresh length of the strip 3ª,
protecting band, and flexible strip 5 drawn onto the mandril and similarly wound,
these operations being repeated until nearly the whole length of the flexible strip
has been covered. The ends of the compound tube thus formed are then jointed
together in any suitable way as for example by a short length of thin india rubber
tubing cemented within the ends; the air tube thus formed is partly inflated, and
the remainder of the covering wound over the joint. Such a tyre can also be made
on a straight mandril of the same section as the one above described, using canvas
cut on the cross in the usual way, bending the tyre into a circle, and joining its two
ends. On inflation the crinkles formed on the inner side of the tyre will disappear,
and when the tyre has once been thoroughly stretched by inflation and kept so
for a day or two, the tube will set into a true circle and the crinkles do not
reappear on the tyre being deflated. As will be obvious tyres thus constructed
will be very light.
As will be obvious the plates 1 may be connected together in various other ways
to form a flexible protecting band of the kind referred to; also that a protecting
band and flexible strip of plano-convex form may be introduced between the air
tube and flexible covering of existing pneumatic tyres.
By the construction described, many important practical advantages are obtained.
Thus when the air tube is fully inflated for use, the india rubber strip will be
constantly subject to the pressure of the compressed air in the air tube and little
further compression of it will take place at the point of contact with the ground,
consequently the loss of power due to such compression which usually obtains
when a tyre is covered with a layer of india rubber placed outside the canvas tube
or its equivalent ordinarily employed to strengthen the air tube and not under
pressure, will be considerably reduced; also by covering the protecting band with
a plano-convex strip, the tyre will have a narrow running surface of practically
constant breadth whereby road friction will be reduced to a minimum. Further-
more by the use of the hard protecting band described, a lower air pressure than
would otherwise be necessary in the air tube, may be advantageously employed,

page_text: particularly in road riding. Hitherto the breadth of the running surface being
dependent on the degree of the air pressure in the air tube, to make it narrow and
reduce the loss of power involved in flection of the tyre for the purpose of
attaining the highest practical speed in riding, it has been necessary to make the
tyre as hard as possible; this has impaired its capacity to diminish vibration in
riding on rough surfaces, and has frequently led to its bursting. By the
construction hereinbefore described, the breadth of the running surface being
constant and independent of the degree of the air pressure, the motive for using
an exceptionally high air pressure is removed, and greater comfort in riding over
rough surfaces can be secured without impairing the ease of running of the tyre.
The change which takes place in the cross sectional form of an ordinary
pneumatic tyre on contact with the ground consists of a flattening of the portion
next the ground to a surface of such breadth that if the air pressure in the air tube
is such as in practice it is found it ought to be, it supports the weight of the rider
and machine with very slight lateral expansion of the tyre, and further of a slight
compression of the rubber with which the tyre is covered, over the portion which
is thus flattened on the ground. Until the tyre thus to some extent Hattens on the
ground, it has, even with the highest air pressure it is practicable to employ, very
little power to support the weight of the rider and machine, but when so flattened
out the breadth of the tread which the form of the tyre produces, renders it very
hard so that it requires great force to compress the tyre any further. This change
of form involves the maximum of friction in proportion to its amount; because the
portion of the tyre thus chiefly subject to flexion and compression, having to bear
the wear of the road friction and to withstand as far as possible cutting and
puncture, must necessarily be made of considerable thickness, while the rest of the
tyre may be made materially thinner, and because the flexion of this portion of the
tyre from an arched to a flat shape is of high angular amount. By my improved
construction of tyre no material change takes place in the cross sectional form of
the running surface of the tyre on contact with the ground, that portion being
merely slightly depressed bodily into the air tube and thus almost the whole of the
friction usually involved in the flattening of the running surface of ordinary tyres
is saved. The compression of the running surface of the tyre on contact with the
ground, causes, as in other tyres the sides of the tyre to expand in proportion, but
the sides as they never come in contact with the ground may be made very thin, for
example about a tenth of the thickness of the portion next the road, so that flexion
at the sides will involve the least possible amount of friction. Also the angular
amount of the flexion will be small as it takes place half on one side and half on
the other of the tyre and consists merely of a change from the normal curved form
of the tyre to a form slightly more curved, and consequently, to secure greater
reduction of vibration and comfort in riding, such tyres may, as I have said, with
advantage be ridden with more spring in them than others, without any material
loss of power in friction due to the flexion of the tyre and without increasing the
running surface to an objectionable degree.
The change which takes place in the form of the longitudinal section of a tyre
on contact with the ground, being of very small angular amount, is of trifling
consequence and does not materially differ in these tyres as compared with others.
In a tyre constructed according to my invention I find it unnecessary to employ
an exterior coating of rubber thicker than is merely necessary to water-proof it
except on the narrow running surface. I thereby effect great saving in cost and
in weight, and great increase in the flexibility of the tyre. The necessary
covering on the narrow portion of the tyre which comes in contact with the road
as indicated in dotted lines at F in Fig. 1, need only be of slight thickness and
may be cemented in place so as to be easily renewable when necessary. This is
the only part which will usually require to be repaired.
Pneumatic tyres constructed as described may in consequence of their narrow
running surface, great resiliency, and ease of running be advantageously used for
machines intended exclusively for use on racing paths. Also owing to the

page_text: practicability of making them of the requisite strength and durability they may
be employed with advantage on the wheels of light fast running vehicles other
than cycles.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
.
1. In a pneumatic tyre the combination with an outer covering or tube forming
or enclosing the air tube or chamber, of a protecting band straight or flat and rigid
in cross section and constructed to be capable when the tyre is rolling whilst
supporting a load of readily undergoing slight contraction and expansion or
reduction and increase of length, and an elastic strip of plano-convex cross
section arranged between the protecting band and the outer covering or tube for
the purpose specified.
2. My improved pneumatic tyres constructed as described and shewn.
Dated this 10th day of May 1899
Dated this 10th day of May 1892
THOMAS DUNN.
W. Lloyd Wisc.
46, Lincoln's Inn Fields, Applicant's Agent.