Note: Descriptions are shown in the official language in which they were submitted.
1079040
In the art of joining the ends of metal tubes together~
particularly if one or both of the tubesare of an aluminum
base alloy, it has been known to provide a solid coating of
fluxless solder on a surface of at least one of two tubular
elements to be joined together and, after heating the solder
to its melting point, to slide the tubular elements against
each otherto disturb the oxide coating normally present on
aluminum and thereby facilitate the bonding of the solder to
metallic aluminum beneath the oxide layer. However, the
necessary sliding fit complicates the operation and requires
the expense of manufacturing to close tolerances.
It has also been known to connect tube ends by
enlarging one to fit over the other, or by soldering each to a
connecting sleeve fitting over both.
In accordance with the present invention, a method of
forming a tight soldered joint between a first hollow,
cylindrical member and a second cylindrical member, the
first cylindrical member having an inner cylindrical surface
loosely overlapping and coaxial with an outer cylindrical
surface of the second cylindrical member, comprising the steps
of precoating at least one of the said surfaces with solder,
heating the soldered surface to the melting temperature of
the solder, and, while maintaining the melting temperature,
swaging down the first cylindrical member to reduce the
diameter thereof and bring its inner surface into an
interference fit with the outer surface of the second
cylindrical member, and while performing the swaging operation,
simultaneously also moving one of the cylindrical members
relative to the other to cause the said surface to slide
against each other, thereby tending to penetrate the surfaces
to expose bare metal to the molten solder.
The invention also provides a method of connecting
two aluminum pipe ends comprising the steps of precoating
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1079040
solder on the interior surface of a sleeve memberr at least
adjacent its two opposite ends~ or on the exterior surfaces
of the pipe ends, the sleeye being a loose fit over the pipe
ends, maintaining the temperature of the sleeve and pipe ends
high enough to melt the solder~ and while the solder is melted~
swaging down at least the opposite ends of the sleeve until
the sleeve ends grip the pipe ends in an interference fit,
and during the swaging operation simultaneously moving the
sleeve relative to the pipe ends~ thereby tending to rub
through the naturally occurring oxide on the aluminum surfaces
adjacent the solder to expose bare metal to the molten solder, ~-
The accompanying drawings show, for purpose of
illustration only, present preferred embodiments of the
invention, in which:
Fig. 1 is a diagrammatic cross-sectional view taken
along the axis of a pair of tube ends with a sleeve positioned
over the gap between them, the sleeve being precoated with
solder in accordance with the invention;
Fig. 2 shows a diagrammatic cross-sectional view
corresponding to Fig. 1, except that a pair of swage blocks of
the invention are also shown after swaging down and soldering
the sleeve to the tube ends in accordance with the invention;
Fig. 3 shows diagrammatically the swaging tool of which
the swage blocks are shown in Fig. 2, viewed endwise relative
to Fig. 2 but omitting the tube ends and sleeve assembly and -
showing the swage blocks spaced slightly apart; and
Fig. 4 corresponds in larger scale to Fig. 3 but shows
details of a present preferred tool of the invention.
DESCRIPTION
Referring now more particularly to the drawing, and
initially to Fig. 1, there is illustrated a pair of tubes
10 and 12 in aligned end-to-end relation, with their
respective ends 14 and 16 facing each other. Although the
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ends 14 and 16 are illustrated as belng spaced, they could
be abutting.
A sleeve 18 extends loosely around the ends 14 and 16
and across the ~oint between them~ to ~oin the two tubes
10 and 12. At least the outer ends 22 and 24 of the inner
surface of sleeve 18 are precoated with solder 20, suitable
for rluxless soldering of aluminum-base alloys. When ~oin-
lng parts of aluminum-base alloys or copper-base alloy.s,
whether aluminum to aluminum or aluminum to copper, the
present preferred solder is 95% zinc and 5% aluminum. Another
solder example is a zinc base solder comprising about 2 to
5 percent aluminum, up to about 5 percent copper, and up to
about 1 percent magnesium by wei~ht, such as the solder sold
~nder the trade name of Ney 380 manufactured by Ney Metals,
Inc., of Brooklyn, New York, comprising 90% zinc, 5% aluminum,
4.~% copper and 0.1% magnesium, balance aluminum.
~he sleeve 18 is placed over one Or the tubes 10 or 12
before the tubes are moved to the position shown in the
drawing, and then the sleeve 18 is moved lengthwise until
its ends 22 and 24 overlap both of the tube ends 14 and 16.
The sleeYe is preferably made to fit loosely over the tube
ehds 14 and 16, thus facilitat^ng the operation and avoiding
the cost of producing the sleeve and tube ends to fine
~olerances.
When the parts are thus assembled 9 at least the ends
22 and 24 of sleeve 18 are swaged down to reduce their
diameter. Heat is applied to the sleeve ends so that the
~older coating 20 is molten during swaging. The tube ends
14 and 16 are preferably preheated to assist in melting the
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107gO40 '
solder. Such meltin~ temperature is maintalned as the
swaging action brings the inner solder-bearing surfaces
of the sleeve ends 22 and 24 against the outside of ~he
~ubular ends 14 and 16, and simultaneously sleeve 18 ls
5. moved relative to the tube ends 14 and 16, preferably
rotationally, but possibly longitudinally, to disturb
~he.naturally-occurring oxide coating around the outside
o~ the tube ends 14 and 16. This ensures that the solder
will bond to the metalIic aluminum beneath th~ oxide
coating. The result is a tight soldered ~oint bet~een
the tube ends 14 and 16.
The above-described swagin~ action is preferably
accomplished by means of the swaging tool 26 illustrated
in Figs. 2 and 3. Tool 26 comprises a pair of blocks 28
and 30 respectively mounted on the ends o~ a pair of
elongated elements pivoted on a pin 36 operated by handles
38 and 40 in the manncr of a pair of p~iers. Although
this simple form of actuation is illustrated for conven-
ience, it is preferable to use an adjustable toggle to
20 give better leverage for gripping, such as exemplified in
the well-known form.of lockin~ pliers sold under the
(~ig. ~)
trademark "Vise Grip" / Opposed semi-cylindrical die faces
42 and 44 respectively formed in the blocks 28 and 30 are
. pressed toward each other when the handles 38 and 40 are
pressed toward each other. The die faces 42 and 44 are
cham~ered at their side edges, as sho~n at 46 in Fig. 3,
and respectively have longitudinal grooves 48 and 50 .
midway around each die ~ace, in order to provide small
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~079040
spaces ror flo~l o~ metal from the outside Or sleeve 18
when the blocks 28 and 30 are pressed together. The
metal Or sleeve 18 ln these spaces helps to prevent
rotary slippage Or the blocks 28 and 30 relative to
sleeve 18, especially if the outside as well as the
inside Or sleeve 18 is precoated with solder. The die
~aces 42 and 44 could extend straight across between the
opposite ends Or blocks 28 and 30, which would result in
~waging down the whole length Or sleeve 18, as might be
pre~erred when ~oining abutting tube ends. However,
swaging ef~ort is reduced by relieving the middle por-
tions 52 and 54 Or the respective die races 42 and 44
when ~oining spaced tube ends, so that only the ends 22
and 24 of the sleeve 18 are swaged down, as sho~n in the
drawing. Electrical heater elements (not shown) can be
mounted in the blocks 28 and 30 ~or internally heating
the blocks 28 and 30 and thus also the sleeve ends 22
and 24.
The blocks 28 and 30 are prererably bored out to
~orm the die ~aces 42 and 44 while they are clamped
against each other, to provide a bore having a diameter
ælightly smaller than the sum Or the outside diameter o~
~he tube ends 14 and 16 plus twice the thickness Or the
respective tube ends, and to make contact between the
blocks act as a limit to control the degree of swaging
action. Thus, when the blocks 28 and 30 are pressed
~ogether by the handles 38 ~nd 40, a slight inter~erence
~it will be created between the inside o~ the sleeve
ends 22 and 24 with the tube ends 14 and 16. The
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iO790~0
thickness o~ solder precoatlng 20 (includlng any solderwhich may be precoated around the outside Or the sleeve
18) is considered ne~ligible for determining the dimen-
sions necessary to achieve the said lnterference fit,
slnce the solder when molten is squeezed out until it
has very little thickness between the parts being
swaged down.
In a specific example of the practice of the invèn-
tion, a coaxial cable was connected by first silver
soldering together the two abutting copper tube ends
constituting the inside element of the coaxial cable.
The outside element of the cable to be ~oined ~ere a
pair Or aluminum-base alloy tubes concentrically surround-
ing and radially spaced from the copper inner tube. In
order to provide access to the abutting inside copper
ends for such solderin~, the outside tube ends had to be
posit~oned about an inch (2.5 cm) apart. The outside
~ubes had an outside diameter Or .410 inch (1.69 cm) and
a wall thickness Or .022 inch (.559 mm) and were not
precoated with solder or flux. An aluminum-base alloy
æleeve was earlier precoated with 95% zinc - 5% aluminum
~older by complete submersion in a bath of molten solder
whlle sub~ected to ultrasinic vibration to improve the
bond. The sleeve precoated wlth solid solder was ini-
tially positioned around one o~ the outer tube ends awayrrom the ~oint between them. After silver soldering the
copper inner tube ends, a gas torch was used to preheat
the spaced outer tube ends, the sleeve was slid over the
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1079040
~oint between the aluminum cnds to a pOSitiOIl li~e that shown
ln ~ig. 1, an~ ~he ~as torch was applied to preheat the sleeve
to the melting temperature Or the solder. The swaging tool
blocks, which had a die face bore of .423 inch (1.075 cm),
were in the meanwhile preheated by the gas torch, and were
clamped around the sleeve and pressure was exerted until the
blocks came against the sleeve long enough to heat the tube
- ends to solder melting temperature and hard enough to tighten
the sleeve around the tube ends. The swaging t~ol was then
~0 rotated several times back and ~orth through an arc of about
30, carrying the sleeve with it, while the tube ends remained
~tationary. Then the blocks were pressed together until abut-
~ing each other, as shown diagran~atically in Fig. 2, thereby
~waging down the sleeve until it had an interference fit with
the spaced aluminum ~ube ends. The grip of the blocks was
then released and the ~oint was ready for use. The swaging
operation take~ about ~ half a minute or less for tubes of
this size.
Another example Or the practice of the invention con-
sists of ~oining two tube ends for use in a refrigeration
8ystem, one being of an aluminum base alloy and the other
being of rerrigerant g-ade copFer, while in abutting rela-
- tlonship. The aluminum tube erd had an outside diameter of
.500 inch (1.27 cm), and a wall thickness of .037 inch
(.855 mm), while the copper tube had the same outside
diameter and a wall thickness of .030 inch (.693 mm). The
tube ends were not precoated with solder or flux. The
81eeve to form the ~oint was of aluminum base alloy and was
about 7/8 inch long (2.22 cm), with a wall thickness Or
.050 inch (.127 mm) and a die face bore of .525 inch (1.335 cm).
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iO79040
The .sleeve was entirely precoated with solder as ln the
previous example. The s~ragin~ and soldeIing operations
were as described above, except that the joint di~fered
rrom that diagra~atically illustrated in Fig. 2 in
`that the tube ends were abutting and the swaging blocks
were not relieved in the middle, so that the sleeve was
uniformally swaged down from one end to the other.
The swage blocks used in the above-stated examples
were of mild steel. However, stainless steel or other
material less subject to reaction with the solder, ~rould
be pre~erable.
The temperatures o~ the blocks and joint assembly
were determined by observing melting of the solder. When
the solder is molten it is slippery between the sleeve
and tube ends, and this is ~elt when the blocks and
slee`ve are rotated relative to the tube ends. In general,
the temperature range Or the region to be Joined is pre-
~erably between the m~lting point o~ the solder (about
720F) up to about 800F).
Aluminum base alloys suitable ~or the purpose o~ the
lnventlon are electrical grade, 1200, 3003, and 6061, to
name just a few examples. In general, any fluxless
æolderable aluminum base alloy can be ~oined in accordance
with the invention. While th~ invention is not advantage-
ous ~or ~oining copper tubes to copper tubes, because
copper can more readily be soldered by other methods, it
is advantageous ~or ~oining aluminum tubes to copper tubes,
as ln the above-stated example. Attentlon is also drawn
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1079040
to the fact that the invention is applicàble to Joining
s~lid wires or bars, instead Or tubes,
While present preferred embodiments of the inven-
tion and method of practicing the same have been illus-
trated and described, it will be understood that the
~.nvention is not l~mited thereto but may be otherwise
variously embodied and practiced within the scope of
the following claims.
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