Year: 1898

page_text: I, CHARLES ALDEN PRATT, of Clinton, in the County of Worcester, and State of
Massachusetts, United States of America, Gentleman, 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:-
This invention relates to air-cushioned or pneumatic tires, such as are used for
bicycle and other wheels. The invention has for its object to provide a tire of this
character, in which the air-confining tube or reservoir shall be protected by a cover
which does not unduly increase the weight of the tire, and which not only protects
the outer portion of the wall of the air-reservoir from liability to be punctured,
but also adds materially to the resilience and speed of the tire. The invention con-
sists in the improvements which I will now proceed to describe and claim.
Of the accompanying drawings, forming a part of this specification,-
Figure 1 represents a transverse section of my improved tire, and a portion of
the wheel-rim to which it is applied.
Figure 2 represents a partial side elevation and partial longitudinal section of
the parts shown in Figure 1.
Figure 3 represents an enlarged sectional fragmentary view.
The same letters of reference indicate the same parts in all the figures.
In the drawings,
a represents an air-receiver or reservoir, which is preferably in the form of a con-
tinuous tube, and is of flexible, and at the same time practically inelastic construc-
tion, so that when charged with air its diameter will not be increased by the
air-pressure beyond a predetermined diameter. The tube or reservoir a may be
advantageously constructed of layers of fabric and rubber suitably compounded to
form an air-tight and inelastic flexible tube, which is equipped with a suitable
valve b, through which it may be charged with air. c represents a cover which is
applied to the exterior of the air-reservoir a and has the following essential
characteristics, namely: first, it is elastic or resilient throughout its entire structure,
so that when interposed between the air-charged reservoir a and the ground, it will
materially add to the resilience of the tire: secondly, its thickness at the part inter-
posed between the reservoir a and the ground is such that the cover constitutes an
effectual protector, preventing access of tacks or other sharp-pointed objects to the
wall of the air-reservoir; and thirdly, its weight is reduced to the minimum, so

page_text: •
that it does not make the tire unduly heavy. The cover, to possess these character-
istics, is best made of sponge-rubber, that is to say, the entire cover is composed of
cellular or spongy rubber, excepting the outer portion, which is provided with
suitable tread surface, preferably of solid rubber of the same quality as that com-
posing the spongy part, and made integral therewith, so that the tread surface or
skin of the cover has substantially the same elasticity as the inner spongy portion.
In the enlarged sectional view shown in Figure 3, the spongy portion is shown at 2,
and the solid rubber skin or tread surface is shown at 3. The cover is preferably
crescent-shaped in cross-section, and is arranged so that its thicker portion is
interposed between the air-reservoir a and the ground. I find that by making a
pneumatic tire of an inelastic inner portion or air-reservoir and a cover which is
of entirely elastic construction, or inherently elastic, and is composed of sponge-
rubber having a suitable outer skin or tread surface, I combine lightness, resilience
and freedom from liability of the air-reservoir to be punctured, to a degree not
attained heretofore.
The inelastic inner portion or air-reservoir prevents the compression of the
resilient cover by the pressure of the charge of air; hence the inherent elasticity of
the cover remains uniform, and is not affected by changes of density of the charge
of air.
It will be seen that the cover is inherently elastic or resilient longitudinally of
the tire, as well as laterally, and therefore gives the tire that quality which is known
as speed. A tire having this quality enables a bicycle to which it is applied to be
more rapidly driven than one in which the material forming the tread surface is
not inherently elastic or resilient
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 :-
An air-cushioned tire comprising a practically non-elastic flexible tube or air-
receiver, and an inherently resilient cover therefor composed of a layer of sponge-
rubber having a suitable resilient or elastic tread surface, said cover having its
tread portion of a thickness to prevent access, to the inelastic tube, of any ordinary
puncturing means, the said inelastic tube or air-receiver serving to prevent changes
in the inherent elasticity of the cover.
1000
CHARLES ALDEN PRATT,
Haseltine, Lake & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.