Improvements in Joints for Tubular Articles.
Year: 1898

page_text: Date of Application, 19th Mar., 1898--Accepted, 9th July, 1898
COMPLETE SPECIFICATION.
Improvements in Joints for Tubular Articles.
I, JOSEPH NATHANIEL HALIFAX, of 6130, La Salle Street, Chicago, United
States of America, Mechanical Engineer, 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:-
This invention relates to improved features of construction in joints for tubular
articles such as the frames of bicycles described in prior Patent dated October 1,
1895, No. 18362, and to an improved process or method of making such joints.
The joint illustrated in said prior patent consists of an external tubular part
or socket and an inner tubular part the end of which is inserted in the socket and
distended into close contact with the inner surface of the socket; the inner surface
of the socket being roughened by knurling or like process so as to form interlock-
ing recesses and projections on the interfitting parts after the inner part has
been distended or expanded within the outer one. My improvement in joints
constructed as above stated contemplates the employment, in connection with the
other parts described, of a separate short metal tube or thimble which is inserted
within the internal tubular part at the end thereof which enters the socket and
which is distended equally with the inner tubular part so as to afford an internal
support and re-enforcement for the parts at the joint.
The employment of such internal thimble has several important advantages,
some of which may be understood from the following: It is a well known fact
that sheet metal, when compressed by rolling, swaging or like means becomes
more rigid and unyielding and, therefore, stiffer and capable of standing greater
compressive strains than metal which has not been so treated. A thimble inserted
within the end of the frame tube prior to the distension of said frame tube by
internal rollers or other expanding means, is compressed or squeezed between the
surface of the tube and the rollers at the same time that it is stretched or increased
in circumference by the action of the expanding devices. Such squeezing or
compression of said thimble, therefore, serves to harden and stiffen the same and
thereby gives it a high degree of strength to resist compressive strains such as
are brought upon the inner tube when tension is applied thereto in a manner to
loosen its end which is within the socket; it being obvious that such loosening
cannot occur except by inward yielding, compression or flattening of the part of
the tube within the socket. Obviously such compression of the thimble, while
making it harder, will also make it somewhat more brittle but this is not objec
tionable, by reason of the fact that the strain coming upon it is mainly a com-
pressive strain only, or one tending to reduce its diameter.
It is also to be noted that, in the absence of any such internal thimble, the
lirect action of the rollers or expanding devices upon the frame tube will neces-
arily result in the compression of the metal of the tube and the making of the
same more brittle in its part within the socket. Such compression of the tube,
herefore, is objectionable because rendering it more liable to fracture at a point
vithin the socket or near the outer end thereof. When the thimble is present

page_text: and the expanding device therefore acts immediately upon said thimble, and not
at all on the tube itself, the latter is merely expanded or stretched and its outer
face forced into the irregularities of the roughened socket, while compression of
the tube takes place to a relatively slight degree; it being well known that in
the compression of sheet metal by the action of rollers or similar means the metal
is made more dense and hard mainly at the surface of the sheet which is directly
subjected to the action of the compressing means. The presence of the said
thimble, therefore, affords a joint which is not weakened by undue compression,
and consequent brittleness, of the metal forming the tube and which at the same
time is so stiff or rigid as to insure a necessary degree of stability, strength and
firmness in the joints between the interfitting parts. As compared with a joint
in which the inner tube is thickened at its end, one having such re-enforcing
thimble is greatly. superior because, as before stated, a separate thimble is made
stiffer and more rigid by compression between the tube and the expanding means
while the direct action of the rollers upon the thickened tube would tend to make
the same more brittle than if the expanding were done without contact of the
expanding means with the tube.
A further advantage gained by the use of a separate thimble arises from the
well known fact that the two relatively thin thicknesses of metal may be more
easily stretched or expanded by rolling than a single piece of metal equal in
thickness to both of such layers. It follows, therefore, that the inner parts of
the joint may be more easily and quickly distended when an additional thimble is
used than when a single inner tube of equal cross sectional area is employed.
In carrying out my invention, I have found that better results are produced
by extending the inner tube or thimble referred to, to a point outside of the
external part or socket, this construction giving greater stiffness to the tube at
the point where it emerges from the socket, and lessening the liability of the
bending or breaking of the tube at the point where it joins said socket.
The invention may be better understood by reference to the accompanying
drawings in which:
Figure 1 is a view in central vertical section, with parts in side elevation, of
a joint between the top frame bar, and the upper head fitting of a bicycle frame.
Figure 2 represents the head fitting in readiness for the insertion of the frame
tube.
Figure 3 shows the end of the frame tube with the thimble inserted therein.
Figure 4 is a side view of the thimble before insertion.
Figures 5 and 6 are sectional views taken respectively on the lines 5-5
and 6-G.
As shown in said drawing, A indicates as a whole the fitting which connects
the head of a bicycle with the front end of the upper frame bar, said fitting con-
sisting of a main tubular part A¹ and a neck or integral thimble or socket A³
which latter is roughened on its inner surface, preferably in such manner as to
form intersecting grooves with intervening elevations, such as are produced by
the action of a knurling tool. B indicates the end of the frame tube, which is
adapted for insertion in the socket A3 and within which is placed a closely fitting
thimble C. The joint when completed is constructed as shown in Figure 1;
both the thimble C and the end of the tube B being distended or expanded in
their parts which are inserted in the socket, so that the outer surface of said tube
is brought into intimate contact with and made to fit the irregularities of the
roughened or serrated socket. The said thimble is arranged to project consider-
ably beyond the outer end of the socket so as to give greater stiffness to the tube
in the part of the same adjacent to the socket or where it enters the same.
thimble being expanded with the tube and to the same extent as the same serves
as an internal support tending to prevent any contraction or collapse of the
tube when strain or pressure is brought upon the outer part of the end of the
tube. The joint is, therefore, greatly strengthened by said thimble for the reason
that no loosening of the inner tube within the socket can occur without the
The

page_text: collapsing, contraction or flattening of the end of the tube which is within the
socket. Moreover, as before stated, the part of the thimble C which is subject to
compression in the act of distending or expanding, is rendered more dense and
rigid and, therefore, better capable of withstanding compression than the tube
itself. Said tube is, therefore, in the finished joint, confined or held between
the inner rigid thimble and the external surrounding socket and being compressed
into intimate contact with the roughened or irregular surface of the socket affords
a permanent joint of great strength and durability. Moreover, the said inner
tube when distended or expanded into contact with the external socket by
pressure acting against the inner thimble only, will be so extended or expanded
and at the same time forced into intimate contact with the socket, without being
itself appreciably hardened or made more brittle by the expanding device
employed.
While in practice I prefer to use the familiar expedient of expanding rollers
for distending the inner tube and its thimble, yet other well known or preferred
means may be employed for the same purpose.
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:-
1. A joint for tubular articles, comprising an outer part or socket, which is
roughened on its inner surface, an inner tubular part inserted within the said
socket and a thimble within the inner tubular part, said thimble and the inner
tubular part being stretched or distended to bring the outer surface of the tubular
part into intimate contact with said socket.
2. A joint for tubular articles, comprising an outer part or socket which is
roughened on its inner surface, an inner tubular part inserted within the said
socket and a thimble within the inner tubular part, said thimble and the inner
tubular part being stretched or distended to bring the outer surface of the inner
part into intimate contact with said socket and said thimble being made of
sufficient length to project outside of said socket to stiffen the inner tube in its
part adjacent to the socket.
3. The method for making joints for tubular articles, consisting of an outer
socket, an inner tube and a re-enforcing thimble within the inner tube, which
consists in applying outward pressure to the inner surface of said thimble in such
manner as to distend or expand both the said inner tube and the thimble and
at the same time to compress the metal of the said thimble by pressure of the
same between the said inner tube and the rollers or other means used for
expanding.
1 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.