Note: Descriptions are shown in the official language in which they were submitted.
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TUBULAR REINFORCEMENT ELEMENT AND METHOD OF MAKING SAME
BACKGROUND OF THE INVENTION
The present invention relates to a tubular reinforcement
element between a hollow tubular member and another member,
and also to a method of making such tubular elements. The
invention is particularly applicable for reinforcing the
connection of two hollow tubular members, such as in constructing
the tubular frame of a bicycle, and is therefore described below
with respect to this application, but it will be appreciated that
the invention could advantageously be used in many other
applications as well.
A common technique for joining together two hollow tubular
members, such as in the construction of bicycle frames, is to use
an external lug which includes a sleeve enclosing and bonded to
the outer surface of one tubular member and formed with a peri-
pheral flange bonded to the outer of the other tubular member.
The bonding of the external lug may be effected by welding or by
brazing. While such a tubular joint construction provides
relatively high mechanical strength, it is visible and may therefore
detract from its external appearance. Moreover, it is expensive
to produce.
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German Patent 94,366 describes a method of connecting
two tubular sections of bicycle frames. The reinforcement
member is an investment casting which is expensive to
manufacture.
U. K. Patent 421,687 relates to seat lugs for cycles,
which are a standard common fully symmetrical draw cup with
a flat bottom with or without the optional tabs which are
obtained by cutting slots in the side wall of said lug.
OBJECTS AND BRIEF SUMMARY OF THE lN V~N-'l'lON
An object of the present inven~ion is to provide a
tubular reinforcement element between a hollow tubular
member and another tubular member, and also a method of
making such a reinforcement element, having advantages in
the above respects. Another object of the present
invention is to provide a reinforcement element, and method
of making same, particularly applicable in the construction
of bicycle frames.
It is a further object of the present invention to
provide a reinforcement element made of a stamped blank by
a single double action formed operation.
According to one aspect of the present invention,
there is provided a tubular reinforcement element made of
stamped blank between a hollow tubular member having an
open end and another tubular member, said tubular element
comprising an axially slotted cylindrical section exten~ing
from a concave end wall. Such a construction facilitates
producing the reinforcement element by a single stage,
double action deep-drawing like process.
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It also increases the lengths of the edges of the internal
lug, where ioined to the two members, for the formation of
fillets of the brazing material, thereby further enhancing
the mechanical strength of the tubular joint.
According to further features in the preferred embodiment
of the invention described below, the other member has a curved
external appearance, and the end wall of the internal reinforce-
ment member has an outer curved surface complementary to the
curved external surface of the other member. The
internal lug is jointed to the hollow tubular member and other
member by brazing.
According to further features in the described embodiment,
the hollow tubular member is joined at an oblique angle to the
other member, e.g., another hollow tubular member, as when
constructing a bicycle frame. In such a case, the open end of the
hollow tubular member receiving the reinforcement element is
initially cut at a bias corresponding to the obl;que angle, and
the end wall of the said reinforcement element is integrally formed
with its side wall at the same oblique angle.
Tubular reinforcement element constructed in accordance w;th
the above features exhibit a very high degree of mechanical
strength because the increased contact surface area provided by
the said element for joining the two members together. In addition,
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since the element is internal, it is hidden from view, and
therefore provides a neat, unbroken appearance.
According to another aspect of the invention, there
is provided a method of making a tubular reinforcement
element from a stamped flat blank being forced through a
drawing die to assume the required configuration.
In one described embodiment, the reinforcement element
is simultaneously joined to both the hollow tubular member
and the other member by brazing after the said element has
been inserted into the open end of the hollow tubular
member. In a second described embodiment, after said
element has been inserted into the open end of the hollow
tubular member, the side wall of said element is first
joined to the hollow tubular member by brazing. Then the
hollow tubular member is placed against the other member,
and the end wall of the reinforcement element is bonded to
the other member by brazing.
As embodied and broadly described herein, the
invention also provides a tubular joint internal
reinforcement element between two tubular members, said
element comprising,
an axially four-slotted cylindrical section integral
with and exten~ing outwardly from a coextensive concave end
wall,
said axially four-slotted cylindrical section defining
four axially extending tabs,
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a first end of each of said four axially extending
tabs integrally joined on a peripheral edge of said
coextensive concave end wall,
said peripheral edge of said coextensive concave end
wall being defined by said first end of each of said four
axially exten~;ng tabs,
wherein said element is formed from a flat stamped
sheet metal blank by a single stage double action drawing
process.
As embodied and broadly described herein, the
invention further provides an internal reinforcement
element for butt joining an end of a first tubular member
to an exterior surface of a second tubular member, said
internal reinforcement element being formed from a flat
sheet metal blank having a plurality of lobes extending
outwardly therefrom, said element having a longitudinal
axis and an end wall, said end wall defining a form-drawn
and generally radially extending cylindrical concavity, and
a form-drawn axially slotted cylindrical sidewall section
integral with said end wall, said cylindrical side wall
comprising a plurality of sections formed from said lobes,
a first end of each of said plurality of sections
integrally joined on a peripheral edge of said end wall,
wherein said peripheral edge of said end wall is
defined by said first end of each of said plurality of
sections.
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As embodied and broadly described herein, the
invention also provides a brazed butt joint between an end
of a first tubular member and an exterior surface of a
second tubular member, said brazed joint being internally
supported by an internal reinforcement element formed from
a flat sheet metal blank having a plurality of lobes
ex~enAing outwardly therefrom, said reinforcement element
having a longitllA;nAl axis and an end wall, said end wall
defining a form-drawn and generally radially extenA;ng
cylindrical concavity, and a form-drawn axially slotted
cylindrical sidewall section integral with said end wall,
said cylindrical side wall comprising a plurality of
sections formed from said lobes,
a first end of each of said plurality of sections
integrally joined on a peripheral edge of said end wall,
wherein said peripheral edge of said end wall is
defined by said first end of each of said plurality of
sections.
As embodied and broadly described herein, the
invention also provides a method of making a joint internal
reinforcement element comprising the steps of:
a) stamping a flat blank from a sheet metal plate in
a configuration including a central formation having a
concave end wall with a central locating tooling hole and
a cylindrical section having four axially extending tabs
with respective sectorial relieves therebetween, each of
said tabs having rounded tips with respective stress
distributing holes,
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b) placing said blank in a forming apparatus and
forcing said blank through a drawing die in a single stroke
double action process, a first action forming said concave
end wall while a second action being the drawing of the
cylindrical section having said four axially exten~;ng
tabs,
c) release of the joint reinforcement element for the
drawing die.
Further features and advantages of the invention will
be apparent from the description below.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, by way of example
only, with reference to the accompanying drawings, wherein:
Fig. 1 is a plan view illustrating the reinforcement
element used in the tubular joint of Figs 3 and 4 when in
its initial flat condition, showing the sectorial
relieving.
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Fig. 2 illustrates the reinforcement element of Fig. 1
in its drawn condition before insertion into the open end of one
of the tubular members.
Fig. 3 is a side elevational view, partly in section,
illustrating one form of tubular joint constructed in utilising
the reinforcement element according to the present invention.
Fig. 4 is a top elevational view illustrating the tubular
joint of Fig. 3.
DESCRIPTION OF A PREFERRED EMBODIMENT
The reinforcement element illustrated in the drawings is
particularly useful for joining together two tubular members, 2
and 4, for example, in the construction of a bicycle frame. As
illustrated in Fig. 3, tubular member 2 is joined at its open end
to the outer face of tubular member 4 at an oblique angle.
According to the present invention, tubular member 2 is joined
to tubular member 4 by the use of a further member, hereinafter
called reinforcement element and generally designated 10, to
distinguish from the external lug commonly used in constructing
bicycle frames and other similar devices.
In the tubular joint produced with the use of the reinforcement
element 10, which is located internally of the open end of tubular
member 2. It includes a side wall 12 of the same configuration as,
and bonded to the inner face of, the open end of tubular member 2,
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and an end wall 14 integrally formed with, and extending across,
side wall 12. End wall 14 is substantially flush with the open
end of tubular member 2 and is bonded to the outer face of tubular
member 4.
The construction of reinforcement element 10, and one method
of making it (by a deep-drawing like process) are more particularly
illustrated in Figs. 1 and 2. ~hen the reinforcement element 10
is made by a deep-drawing like process, a flat blank 10' of the
required configuration is first stamped from a flat sheet metal as
shown in Fig. 1. The flat blank 10' is then assuming formed-drawn
in a single operation double action drawing tool-d1e, assuming the
configuration illustrated in Fig~ 2.
The flat blank illustrated in Fig. 1, includes a central
formation 14' which, in the drawn form of the element as illustrated
in Fig. 2, defines the end wall 14 of the element. Blank 10' is
a properly angled concave surface integral with a four slotted
cylinder section, as illustrated in Fig. 2,
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Blank 10' is further formed with a central hole 18 through
format;on 14', and with a further optional hole 20 through each
of the tabs 12a'-12d'. Hole 18 thus appears in the centre of the
end wall 14 in the drawn condition of the internal element
illustrated in Fig. 2, while holes 20 appear through the tabs
12a-12d defining the element side wall. The centre hole 18 is
preferably of non-circular configuration, e.g., square configuration,
as it may be used for locating in the drawina tool ~hen the element
is formed by the drawing process. Opt~onal holes 20 through the tabs
12a-12d are shown as being of circular conflguration, but they too
may also be non-circular- These holes are a stress distributjon
in assembly feature.
During the drawing process, the tabs 12a'-12d' are bent out
of the p~ane of the,c~ntre formation 14', so as to produce the
four slotted cylindrical sectinn.
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After the reinforcement element 10 illustrated in Fig. 2
has been formed as described above, it is inserted into the
open end of tubular member 2, with the end wall 14 substantially
flush with, and extending across, the open end of the tubular
member. Tubular member 2 with its internal lug 10 is then placed
firmly against the outer face of tubular member 4, and the whole
assembly is then brazed by a conventional brazing process.
Alternatively, the brazing may be in a two-step procedure,
wherein element 10 is first brazed to tubular member 2, and then
is brazed to the outer face of tubular member 4.
The blank 10' is dimensioned so that, in its drawn form as
illustrated in Fig. 2, the outer faces of the tabs 12a-12d
defining the side wall 12 firmly engage the inner face of tubular
member 2 ~o as to retain the element in place until bonded by the
subsequent brazing operation.
It will thus be seen that the illustrated joint will exhibit
a high degree of mechanical strength because of the increased
contact surface provided by the reinforcement element 10 for joining
together the two tubular members 2, 4. Also, since the reinforcement
element 10 is hidden from view, the tubular joint presents a neat,
unbroken appearance.
Relieving by fo~r bend oriented slots
provides a further important advantage. It facilitates the drawing
of the blank into the form of the internal lug illustrated in
Fig. 2~ by a single stroke dual stage drawing operation.
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.
While the reinforcement element 10 is described above
as having been made by a deep-drawing like process, it will be
appreciated that it could be made by other processes, for
example an investment casting process or a conventional multi stage deep-
drawing process. The reinforcement element may also be used in
other applications than joining two tubular members together for
producing a bicycle frame.
Further variations, modifications and applications of the
invention will be apparent, such as reinforcement element provided
with more or less than four tabs.
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