Note: Descriptions are shown in the official language in which they were submitted.
CA 02700760 2010-03-24
Specification: Hose Assembly
The invention relates to a hose assembly for an arc welding or cutting torch
having a
plurality of current conducting leads, wherein the leads comprise an aluminum
wire, the
current conducting leads are accommodated in a channel, and wherein the hose
assembly has a channel for guiding a welding wire.
Prior Art
Arc welding and cutting torches have long been known in the prior art. Welding
and
cutting torches of this type can be embodied for manual or automated welding.
Most arc
welding and cutting torches for manual use comprise a base and a hand piece,
which are
connected to one another via a hose assembly. With manual arc welding and
cutting
torches, it is essential for the hand piece to be as freely movable as
possible. The
material must therefore have especially good reverse fatigue strength under
bending and
twisting stress.
Arc welding and cutting torches for automated welding are frequently
siructured as robots
comprising a movable robotic arm which moves up to areas to be welded. In such
cases,
a hose assembly is provided between a base and an actuator. With automated
welding,
the robotic arm frequently operates at high acceleration, which increases the
speed of
welding. The hoses swing freely within certain limits, and are thus exposed to
high
mechanical stresses.
Welding requires high levels of electrical power, which must be transported
via power
cables from the base to the hand piece. In the prior art, only copper is used
for power
cables for arc welding and cutting torches due to its high electrical
conductivity. Another
property of copper is its high thermal conductivity, which allows it to
rapidly transport
away heat that is generated as a result of resistance. Copper also fulfills
the necessary
requirements with regard to mechanical properties. In the prior art, the power
cables are
customarily configured as stranded wires.
It is also known In the art that eiectricai conductors can be produced from
all types of
metals.
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A hose assembiy having the characterizing features initially described is also
known from
DE 15 15 145 A. For guiding the welding wire, the welding cable contains a
sheath made
of flexible synthetic materiai and having a completely smooth interior wall.
This sheath is
surrounded by a helically wound bundle of copper wires or aluminum wires for
conducting
current. The wire bundle is encased on the outside by a layer of rubber. To
reinforce the
cable against tensile stress, the conductor can be encased In steel braiding.
DE 85 09 258 U1 discloses a welding cable in which a portion of the current
conducting
leads are made of aluminum and another portion of the electrical leads are
made of
copper. In this case, an inner conductor is made of aluminum, with an outer
conductor
made of copper coiled onto it.
The copper electrical conductors that are currently being used for hose
assemblies have
the disadvantage that the electrical conductors make up to 2/3 the total
weight of the
hose assembly, which can make handling them over long periods of time
fatiguing.
Stresses on hose assemblies used for automated welding also increase with the
inertial
mass of the hose assembly.
DE 20 52 462 B2, DE 211, 24 52 A, US 2006/0102368 A1, US 6 178 623 B1, and US
3
926 573 describe conductors having an aluminum core onto which a copper layer
is
applied directly or indirectly as an outer sheath.
DE 85 09 258 U1 concerns a welding cable comprised of two different conductor
materials, such as aluminum and copper, wherein a single conductor having a
higher
conductivity value, density and breaking load, such as copper, is twisted onto
a conductor
having a lower conductivity value, density and breaking load, such as
aluminum.
DE 24 09 322 Al discloses a tubular piece made of rubber-like, flexible and
optionalty
fire-resistant material configured to acoommodate separate elements and leads
that are
customarily used in inert gas welding technology, wherein the tubular piece
has a plurality
of separate channels.
EP 0 076 390 Al also describes a device for use in inert gas welding using
fusible wire
electrodes. in this case a coaxially structured hose assembly is provided,
comprising a
welding current lead, control leads and an annular gap which conducts an inert
gas. The
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wire electrode is arranged centered in the hose assembly, inside a gas
Impermeable,
flexible sheath.
DE 88 06 360 U1 discloses a device for connecting a torch for use in inert gas
arc
welding, with a hose assembly comprised of power cable, Inert gas line,
cooling water
intake line, cooling water return line, and switch cable, wherein the end of
the hose
assembly that faces the torch opens into a housing which contains couplings
for the
power cable and a cooling water line with a current/water cable for the torch,
and
couplings for the inert gas line and the other cooling water line with
allocated leads for the
torch, wherein a coupling for the switch cable is also accommodated in the
housing.
DIN EN 60228, September 2005, relates to conductors for cable and Insulated
leads, and
defines the nominal cross sections for conductors of cables and insulated
conductors for
electrical power systems. It also contains requirements for the number and
dimensions of
wires and for resistance values. The conductors comprise single- and multiple-
wire
conductors made of copper, aluminum and aluminum alloys for permanent
installation
and flexible copper conductors.
The object of the invention is to propose a hose assembly for an arc welding
and cutting
torch, which is substantially lighter than hose assemblies containing copper
cables known
in the prior art, but which has comparatively favorable mechanical properties,
especially
with regard to torsional or bending stresses.
Presentation of the Invention
The object is attained with a hose assembly according to claim 1. Advantageous
embodiments are specified in the dependent claims.
The use of copper-coated aluminum wire as the current conducting lead in the
hose
assembly has the benefit of decreasing the weight of the assembly while at the
same time
eliminating the occurrence of high temperatures at the transition points
between the
conductors and the connections. This is presumably attributabie to the fact
that the
inherently higher transition resistance between aluminum and the respectlve
connection
is reduced substantially due to the use of the copper on the aluminum wire,
thus although 35 a weight reduction is achieved, the electrical and mechanical
properties of the eiectricai
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conductor are largely retained, as compared with the use of conventional
copper
conductors. In this case, multiple current conducting leads are arranged
coaxially around
a central channel. This enables muitiple functions that the hose assembly will
perform to
be combined, with a smaller number of individual hoses. This also allows
synergistic
effects to be achieved, for example if the central channel is used to convey a
cooling
medium. The current conducting lead, which gives off heat, can then be
simultaneousiy
actively cooled by the cooling medium. Also provided is a channel for guiding
a welding
wire. This allows a comparatively large amount of welding wire to be stored in
a base
station of the welding unit, and for the welding wire to be guided through the
hose
assembly to the hand piece as needed. A channel for the current conducting
lead is also
provided. Especially with a coaxial assembly, It can be necessary to spatially
separate
the individual functions to be performed by the hose, for example because the
potential of
the current conducting lead is different from that of a welding wire that may
be
transported in the hose assembly. Moreover, all the channels are arranged
coaxially.
This enables the most efficient use of the existing space and produces hose
assemblies
of smaller diameters, resulting in easier handling. The channel containing the
current
conducting leads encompasses the channel for conducting the medium, and the
channel
for conducting the medium encompasses the channel for guiding the welding
wire. The
medium channel can thus be used for cooling the welding wire channel and the
channel
containing the current conducting lead at the same time.
Of course, according to one preferred embodiment of the invention, all the
current
conducting leads of each current conductor are embodied as copper-coated
aluminum
wires. In this case, the individual conductors can be embodied in the form of
individual
wires, stranded wires, or the like.
It has also been found that the use of copper-coated aluminum wires in the
hose
assemblies of the invention is much more cost effective. This is due to the
fact that
processing is substantially simpiified in a simpiiFied drawing process.
The connectors of the hose assembly can be connected to the current conducting
lead or
leads via a crimped connection.
However, one preferred variant calls for the current conducting leads with the
copper-
.35 coated aluminum wires to be connected to the hose assembly connectors by
means of
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ultrasound welding. In that case, the outer stranded wires of the current
conducting lead
of the hose assembly can be directly closed with a copper sleeve. This
connection
method has the advantage of lower transition resistances and thus also lower
temperature increases at the transition points. This ultrasound welding
process can be
used both with aluminum wires and with aluminum wires having a layer of copper
on their
outer sheath. It has also been found that the ultrasound welding process
increases the
strength of the connections or the sleeves substantially over the strength of
a crimped
connection. Both copper sleeves and steel sleeves can be used as connectors.
The copper coating on the aluminum wire is advantageously 1 to 100 pm thick.
This
measure ensures an optimization of the copper-coated aluminum wire in terms of
minimizing its weight with the lowest possible transition resistance.
It has also been determined that with hose assemblies, current conducting
leads
configured as stranded wires, with the individual wires of these containing
aluminum,
meet the requirements for use in arc welding and cutting torches.
Hose assemblies according to the invention have the advantage of being
substantially
lighter than hose assemblies with copper leads, and therefore easier to
handle. Despite
the required increased volume of aluminum necessary for transmission, the
total weight
of hose assemblies produced using aluminum stranded wires is substantially
lower than
the total weight of conventional hose assemblies.
The hose assembly of the invention overcomes a long-standing prejudice held by
those in
the industry that aluminum cables should not be used in hose assemblies due to
their
less favorable conductivity properties and due to their flexural and breaking
properties.
By configuring the aluminum lead as a stranded wire with relatively fine
individual wires,
the bending and torsional stresses exerted on each individual wire are lower
than with a
wire having a larger cross section.
For the individual wires, pure aluminum having a degree of purity of A199 to
A199.9 has
proven particularly well suited. However, aluminum alloys may also be used.
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At least one composite lead is advantageously provided, which contains
individual wires
made of copper-coated aluminum or an aluminum containing alloy and individual
wires
made of copper or a copper containing alloy. Surprisingly, it has been found
that
composite leads of this type substantially improve the removal of heat from
the leads,
making the overall cost of the hose assembly even more favorable as compared
with
pure copper leads.
Advantageously, the lead has at least four individual stranded wires, which
are laid
around a core strand. A lead having this type of structure is highly flexible,
even with
large lead cross sections.
Advantageously, each individual stranded wire andlor the core strand are made
up of 20
individual wires. This further increases its flexibility and reduces the risk
of cable break.
In one advantageous embodiment of the invention, the individual wires have a
diameter
of 0.05 mm to 0.5 mm. A diameter of 0.15 mm is especially preferable.
Individual wire
diameters such as these allow the necessary conduction parameters to be
achieved.
Particularly advantageously, the current conducting leads, especially the
current
conducting stranded wires, are wrapped helically or spirally around a central
channel.
Because the current conducting leads or stranded wires extend spirally or
helically
around the central channel, preferably on fts exterior, in the hose assembly,
the flexural
stress exerted on the current conducting leads when the hose assembly Is bent,
stretched, compressed or twisted is distributed. In particular, twisting the
leads or
stranded wires around the central channel relieves the stress on the hose
assembly in the
range of the smallest radius of curvature of the current conducting leads or
stranded
wires.
The length of lay of the stranded wires Is advantageously 15 mm to 200 mm,
with 40 mm
to 60 mm being especially preferred. Such lengths of lay improve the
mechanical
properties of the hose assembly.
Advantageously, at least one additional control current lead is provided. This
allows the
functions of the welding device to be easily controlled using the hand piece.
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Particularly advantageously, at least two channels are provided for conducting
a medium,
along with at least two current conducting leads. As in the case described
above, the
combination of medium conducting lead and current conducting lead produces
positive
effects in terms of the efficiency of current conduction. Providing at least
two channels
with current conducting leads, wherein the current conducting leads can also
be arranged
centrally with the medium flowing directly around them, increases the surface
of the leads
and thus the amount of heat they emit. Moreover, the cross section of the
leads can be
increased while their flexibility is maintained. This makes it possible to
increase the total
power that can be transmitted via the hose assembly.
A polymer has proven to be a suitable medium for the channels. Polymers can
fulfill the
widest range of requirements and have proven effective for long-term use.
The medium is preferably comprised of a gas or a liquid. It can be the process
gas, such
as the inert gas used in inert gas welding, or a liquid, for example for
cooling the hand
piece.
The current conducting lead advantageously has a connector at one end which is
connected to the current conducting lead via a crimped connection.
Surprisingly, it has
been found that crimped connections of this type produce a secure connection
between
current conducting lead and connector which remains reliable over the long
term.
Atternatively or additionally, it is possible for the current conducting lead
to be welded to a
connector or to a wire end sleeve via ultrasound. It has been found that the
copper-
coated aluminum wires can be securely connected to connectors not only via
crimped
connections, but also via ultrasound welding. The latter case results in quasi
similar
materials at the connecting surfaces, which can be better joined.
Brief Description of the Drawings
Additional goals, advantages, characterizing features and potential
applications of the
present invention are contained In the following description of several
exemplary
embodiments, in reference to the set of drawings. All described andlor
illustrated
features, alone or in any logical combination, constitute the subject of the
present
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invention, regardless of how they are combined In the claims or in the
references to
previous claims.
Figure 1 a cross section of a hose assembly according to the invention;
Figure 2 a cross section of an aftemative embodiment of a hose assembly
according to the invention;
Figure 3 an embodiment of a so-called current/water cable according to the
invention;
Figure 4 a longitudinal section of a current cable according to the invention;
Figure 5 a cross section of the cable of Figure 4 along the line A-A;
Figure 6 a perspective view of a stranded wire.
Figure 1 showed a schematic representation of a hose assembly 1 according to
the
invention, such as are used in arc welding or cutting torches, for example. In
the
exemplary embodiment chosen here, the hose assembly I combines several
individual
hoses together inside an outer hose 2, and guides these from a base (not shown
here) to
a hand piece (also not shown here) of the welding device, or from a base of an
automated welding device to an actuator.
The hose assembly 1 has a cooling medium intake hose 3, in the interior of
which a
cooling medium is conveyed from the base to the hand piece or actuator. Also
provided
is a process gas hose 4, inside which the prooess gas flows to generate an
inert gas
atmosphere. A wire guiding hose 5 is also provided, which transports a welding
wire 6
inside a spiral wire guide 7 provided In the wire guiding hose 5. Also
provided is a control
lead 8, via which control signals are transmitted from the hand piece or
actuator to the
base.
A so-called current/water cable 9 is also provided. inside a hose 10 of the
current/water
cable 9 a current conducting lead 11 is provided, which will be described in
greater detail
further below. Between the hose 10 and the current conducting lead 11, a
channel 12 for
cooling medium return is provided. This offers the advantage that the cooling
medium in
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the cooling medium return can also cool the current conducting lead 11, which
becomes
very hot due to the high power required for welding.
Additional leads can be provided inside the hose assembly 1.
Figure 2 shows an additional embodiment of a hose assembly 20 according to the
invention. The hose assembly 20 represented in Figure 2 has an essentially
coaxial
arrangement of the individuai elements. In the interior of the hose assembly
20, a
welding wire 21 is guided inside a spiral wire guide 22. Encompassing the
spiral wire
guide 22, an intermediate space 23 is provided, which serves to convey the
process gas.
A hose 24 is provided to create a gas-tight seal. The hose 24 is made of an
elastic
polymer. Current conducting leads 25 and control leads 26, shown here as
black, are
positioned on the hose 24. The current conducting leads 25 have the stranded
wire
configuration according to the invention, which will be specified in greater
detail in
reference to Figure 5. The hose assembly 20 is held together by an outer hose
27 that
encompasses all the hoses. An annular channel is formed between outer hose 27
and
hose 24 and holds the current conducting leads 25 and the other leads. The
hose
assembly 20 can be a part of a larger hose assembly in which additional hoses
for
various purposes are provided, for example cooling medium hoses and the like.
The
current conducting leads 25 and 44 (Figure 5) are wound helically around the
central
channel 23 or 41 (Figure 5). The current conducting leads and stranded wires
25, 44,
respectively, are thus arranged in the outer area of the cross section of the
hose
assembly. This measure allows the flexural stress on the current conducting
leads 25,
44, especially in the areas of the smallest radius of curvature of the hose
assembly, to be
distributed and thus reduced.
Figure 3 shows an enlarged representation of the current/water cable 9 of
Figure 1.
The current/water cable 9 comprises an outer hose 30, which is embodied as
water-tight,
allowing it to conduct the cooling medium. in place of water, any other fluid
known in the
prior art can be used as the cooling medium. In a concentric arrangement, the
current
conducting lead 11 is located at the center of the current/water cable 9.
The current conducting lead 11 is embodied as a stranded wire comprised of
individuai
wires 32. The individuai wires 32 of the stranded wire 11 are made of aluminum
or an
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aluminum alloy. Pure aluminum having a degree of purity of A199 to A199.9 has
proven
particularly suitable for this purpose. These wires 32 are covered or coated
with a layer
of copper, thereby substantially reducing transition resistance. The thickness
of the
coating is between 1 and 100 pm.
The individual wires 32 have an Individual wire diameter of 0.1 to 0.3 mm.
Approximately
thirty individual wires are bundled into a single stranded wire, wherein
stranded wires
containing up to 100 individual wires have proven suitable in terms of their
elastic
properties. The cross section of such a stranded wire is approximately 10 mm2,
whereas
the copper stranded wires known from the prior art have a cross section of 6
mm2, for
example. With aluminum, cross sections of up to approximateiy 30 mmZ are
easily
possible. The length of lay of the stranded wires themselves is approximately
60 mm, but
can range from 15 mm to 200 mm, depending upon the stranded wire cross
section.
For so-called composite leads, copper-coated individual wires made of aluminum
or an
aluminum alloy and individual wires made of copper or a copper alloy can also
be used in
a stranded wire.
In a further embodiment which is not shown here, the current conducting lead
11 can
have a plurality of stranded wires, wherein a core stranded wire is provided,
around which
the other stranded wires 31 are laid.
It is possible to provide a plurality of the current/water cables shown in
Figure 3 inside a
single hose assembly. Two current/water cables have proven particularly
preferable, one
being used for supplying cooling medium and one for returning cooling medium.
In this
way it is possible to divide the current conducting leads, thereby increasing
the flexibility
of the hose assembly while improving the cooling power of the cooling medium
on the
current conducting leads. Assemblies of this type are known in the prior art.
Figure 4 shows a longitudinal section of a power cable 40 with a connection 35
to a base
of the welding device. The connection 35 comprises a hexagon nut 36 for
connecting the
power cable 40 to the base in the proper alignment. A wire end sleeve 37 and a
ferrule
38 are also provided, which accommodate the end of the lead 40.
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Also shown are control leads 43, which are connected to the base via separate
plug
connectors 39. The control leads 43 extend out of an outer sheath 46 of the
power cable
40 in front of the end area of the power cable 40. In the interior of the hose
40, the
crimped connection creates a hollow area 41 extending from the connection 35
to the
opposite end of the lead 40, which is tightly sealed. The area 41 can be gas-
tight and/or
fluid-tight.
Figure 5 shows a cross section of the power cable along the section line A-A
of Figure 4
of the power cable 40, in the inside of which is the area 41, which can be
used to conduct
either a cooling medium or a process gas.
The inside area 41 is sealed off by a hose 42. On the outside of the hose 42 a
plurality of
leads having different functions are arranged. Control leads 43 for
controlling the
functions of the welding device are indicated by closely hatched lines.
Current
conducting leads 44, which are also embodied as stranded wires, are indicated
by lightly
hatched lines. The areas 45 are assigned no specific function. The areas 45
can be
filled with a filler material or with plastic cords, for example. The leads
43, 44 and the
areas 45 are encompassed by a hose 46.
Figure 6 shows a perspective view of the current conducting lead 11 of Figures
1 and 4.
The individual wires 32 are laid around a core wire 47. One-half lay is shown
here. The
length of lay d, i.e., the length extending in the direction of conduction
over which an
individual wire 32 is wrapped once completely around the core lead 47, is 60
mm.
However, the length of lay can vary from 20 mm to 120 mm, depending upon the
thickness of the lead 11 and the thickness of the individual wires 32. A lead
embodied in
this manner has the advantage that it can withstand many types of stress. The
lead 11
can be twisted in both directions, bent and stretched or compressed. Moreover,
the
elasticity of a lead embodied in this manner is significantly greater than
with a lead made
of solid material having the same lead cross section.
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List of Reference Symbols
1 - Hose assembly
2 - Outer hose
3- Cooling medium intake hose
4 - Process gas hose
5 - Spiral wire guide
6 - Welding wire
7 - Spiral wire guide
8 - Control lead
9 - Current/water cable
10 - Hose
11 - Current conducting lead
12 - Channel
20 - Hose assembly
21 - Welding wire
22 - Spiral wire guide
23 - Channel
24 - Hose
25 - Stranded wire
26 - Control lead
27 - Outer hose
- Outer hose
32 - Individual wires
25 35 - Connection
36 - Hexagon nut
37 - Wire end sleeve
38 - Ferrule
39 - Plug connector
30 40 - Power cable
41 -Area
42-Hose
43 - Control leads
44 - Current conducting leads
45 - Area
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46 - Hose
47 - Core wire
d - Length of lay
13
