Improvements in the Manufacture of Air Tubes for Pneumatic Tyres
Year: 1897

page_text: Date of Application, 13th July, 1897-Accepted, 21st Aug., 1897
COMPLETE SPECIFICATION.
[Communicated from abroad by THE NEWTON RUBBER WORKS, a corporation
organized and existing under and by virtue of the laws of the State of West
Virginia, and having its principal place of business at Newton, Upper Falls,
in the County of Middlesex, and State of Massachusetts Post Office address
Newton Upper Falls, Massachusetts United States of America.]
Improvements in the Manufacture of Air Tubes for Pneumatic Tyres
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, 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: -
The invention which forms the subject of the present application, is an improve-
ment in the inner inflatable or air tubes for pneumatic tires and in methods of
manufacturing the same. Heretofore these tubes when designed for use with
pneumatic tires have been made with closed ends which overlap when the tube
is inserted in the casing or sheath of the tire. In some instances the ends of the
tubes have been formed with faces squared so that they simply abutted when the
tube was in its sheath. In others, the ends have been bevelled or inclined so as to
form a scarf-joint when overlapped. In still another form, the ends of the tube
have been flattened and closed so as to leave solid extensions or end-portions which,
when the tube is in its sheath, overlap so that the solid portion of one end overlaps
an inflated portion of the other.
Theoretically, the scarf-joint made by a tube with overlapping bevelled ends is
the most desirable, as it contains no solid part which produces any noticeable
unevenness on the tread portion of the tyre when the latter is fully inflated, but
such tubes have not, so far as is known, come into any extended use, mainly for the
reasons that they were difficult and expensive to manufacture, and liable to rupture
at the end or edge of the bevelled portion.
The object of this invention is to produce an inner or air tube with bevelled or
wedge-shaped ends which shall not be open to the objections found to exist in such
forms of tube as heretofore made, and to this end there is made a tube of thin
rubber with bevelled or wedge-shaped ends reinforced interiorly at the points or
extreme ends by strips of fabric. Such tubes are manufactured by a novel, simple
and economical process, which will now be described by reference to the accom-
panying drawings:
Fig. 1 is a mandrel which is employed for making the end portions of the tube.
Fig 2 is a perspective view of such end.
Fig 3 is a sectional view showing the tube mandrel enveloped by the tube.
Fig. 4 is a view illustrating the method of removing the tube from the mandrel.
Fig. 5 is a sectional view of a tire sheath containing the tube.
As a matter of convenience, two forms of mandrel are used in the process of

page_text: making the tubes. One form, A, as shown in Fig. 1, is of a circumference pro
portioned to the size of tube desired, and has a bevelled or tapered end, but is com
paratively short. Another form, B, shown in Fig. 3, is of the same circumfer
ence as the first, but is of the length required for the finished tube, and has both
ends tapered or bevelled. It will be understood of course that the use of two man
drels is purely arbitrary, and that any other number may be employed is desired.
The short mandrel A is first wrapped with a thin covering of crude rubber, and
over the tapered ends of the same are folded strips of fabric D, which adhere to
the crude rubber. The crude rubber on the short mandrel is then partially
vulcanized and stripped off in the form of caps C, Fig. 2.
These caps are then drawn over and fitted to the ends of the long mandrel B
and a sheet or strip of crude rubber is wrapped around, or in any of the usual ways
applied to the central part of the mandrel and over so much of the end portions
already covered as will form a good lapped joint with the semi-vulcanized caps
thereon. The overlapped portions are then pressed or rolled to make a smooth
and perfect joint.
The mandrel is then placed in the vulcanizing oven and cured.
As is customary
in such cases, the mandrel with the unvulcanized tube thereon is wrapped with a
suitable fabric before putting it in the oven, which operation may be readily
accomplished by revolving the whole in a lathe and winding a strip of sheeting or
other suitable material around it.
After vulcanization, a small hole is cut in the tube at the point indicated by the
index finger, and the end of the tube pulled along the mandrel until the hole is
brought to the adjacent end of the same, which is then passed out through the hole,
and the tube then merely stripped from the mandrel and at the same time turned
inside out. The portion of the tube which is thus withdrawn from the mandrel
without inversion is turned inside out by drawing its end through the hole.
The reinforcing strips D will now be inside of the tube, and the latter is com-
pleted by the application of the valve tube to the hole through which the mandrel
was withdrawn.
The additional vulcanization to which the ends of the tube are subjected renders
them slightly firmer and stronger, but the joints between the ends and main
section of the tube are scarcely perceptible and, for all practical purposes, there is
formed a tube with closed wedge-shaped and reinforced ends, the rubber walls of
which are of uniform thickness and homogeneous in character.
This tube is used with any outer sheath into which it may be introduced, by
simply drawing or placing it within such sheath and permitting its ends to overlap.
The extent of overlap is largely immaterial. It may be reinforced wherever
necessary on its exterior surface by strips of fabric applied thereto in the usual
manner.
Having now particlarly described and ascertained the nature of this invention,
and in what manner the same is to be performed, as communicated to me by my
foreign correspondent, I declare that what I claim is :-
1. An inflatable inner tube for pneumatic tires, composed of vulcanized india
rubber having closed bevelled or wedge-shaped ends reinforced by a strip of
adherent fabric applied to the interior surface of the bevelled or wedge-shaped
ends only, as set forth.
2. The improvement in the art of manufacturing inner air tubes for pneumatic
tires, which consists in forming a tube of india rubber with closed bevelled or
wedge-shaped ends, reinforcing the ends only by applying and causing to adhere to
the same strips of fabric, forming a slit or opening in the tube, and inserting the
tube by drawing its ends through such opening, as set forth.
3. The improvement in the art of manufacturing inner air tubes for pneumatic
tires, which consists in forming a tube of india rubber with closed bevelled or
sections of tube with closed bevelled or wedge-shaped ends, reinforcing the said
ends exteriorly with fabric, uniting the sections to the open ends of an unvulcan-

page_text: ized tube, vulcanizing the whole, then forming a slit or opening for the valve in
the tube and inverting the tube by drawing its ends through said opening, as set
forth.
4. The process herein described, which consists in forming caps of crude rubber
on short mandrel sections having bevelled or wedge-shaped ends, and partially
vulcanizing the rubber, then stripping the rubber from the short mandrels and
drawing the caps onto the ends of a long mandrel, then wrapping or applying
crude rubber to the long mandrel and overlapping the partially cured caps, then
subjecting the whole to vulcanization and withdrawing the mandrel through a
hole or slit in the tube, as set forth.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.