The invention relates to a method for fashioning a detail of
an evaporator of the roll bond type for use in a refrigerating
appliance, particularly of the domestic type, and to a refrigerating
appliance equipped with an evaporator fashioned by employing this
method.
The invention is in particular applicable to a
refrigerator of the static function type or the forced circulation type,
with a single capillary or twin capillaries. For the sake of
simplicity, the following description will refer to the single-capillary
type, it being understood, however, that the invention is similarly
applicable to refrigerating appliances having more than one evaporator
and a corresponding number of capillaries.
In refrigerant circuits
for domestic refrigerating appliances of a known type, the capillary
and the return pipe are connected to the evaporator by means of a
"union" using a length of pipe, preferably aluminum pipe, to be inserted
into a suitable cavity formed between the two aluminum sheets of which
the well-known "roll bond" evaporator is composed.
As generally
known, the employ of the roll bond technique permits the manufacture of
the refrigerant circuit to be greatly simplified, although there are
certain shortcomings known to those skilled in the art and relating to
the method employed for making and connecting the evaporator.
As a
matter of fact, in known refrigerating appliances equipped with a roll
bond evaporator, the return pipe is compression-fitted thereto by
exclusively mechanical means. This fitting technique is unable, however,
to guarantee hermetic sealing at pressures of more than about 5
kp/cm<2>, so that under certain circumstances the high-pressure
fluid tends to leak from the mechanic connection and to thereby escape
from the refrigerant circuit.
The gravest inconvenience resulting
from this technique is the possibility of the escape of gaseous
refrigerant into the ambient atmosphere. This is because the connection
of the return pipe to the return passage of the roll bond evaporator as
well as the connection of the capillary to the are generally
accomplished by the employ of well known procedures consisting in the
compression from the outside of determined portions of the roll bond
structure about the return pipe and the capillary at the locations of
the return passage and the inlet pasage, respectively, of the roll bond
evaporator.
This compression-fitting process may be accompanied by
soldering the return pipe to the roll bond structure at the point of
entrance, or by the application of an adhesive having suitable
characteristics to the surface of the capillary and that of the return
pipe at the respective compression-fitting locations.
The
discussed shortcomings derive from the fact that the soldering operation
is always a critical process with sometimes uncertain results, and in
any case rather costly. For this reason the soldering method is
whereever possible replaced by the application of adhesive at the
compression-fitting locations.
On the other hand, however, the
application of an adhesive to the surface of the return pipe to be
inserted into the roll bond structure is not without problems caused for
instance by the formation of bubbles in the thin adhesive coating or by
the presence of adhesive-free areas resulting from the viscosity of the
adhesive or from the adhesive being scraped off by mutual contact
between complementary surfaces during the fitting process, which is
usually a manual operation. Finally, the manual application of the
adhesive may result in the presence of insufficient or excessive amount
of adhesive on different surface areas, giving rise to faulty sealing.
The
escape of the gaseous refrigerant cannot always be detected in the
course of controls during the manufacturing process, particularly in the
case of extremely small leaks. The full impact of the defect is thus
noticed only after the refrigerating appliance has been put into use,
requiring the manufacturer to carry out extremely onerous and laborious
service operations, as well known by those skilled in the trade, without
any remedy in sight.
The construction and maintenance of
refrigerating appliances of this type are thus rendered rather
complicated by the described operations which do not, moreover, lend
themselves to being readily automatized.
It would therefore be
desirable, and is in fact an object of the present invention, to provide
a domestic refrigerating appliance in which the above discussed
shortcomings are avoided without incurring construction complications or
the necessity of novel technologies, so as to maintain low production
costs.
These and other objects are attained in a refrigerating appliance as defined in the appended claims.
The
invention will be more fully understood from the following description,
given by way of example with reference to the accompanying drawings,
wherein: fig. 1 is a diagrammatic illustration of a first step in the
method according to the invention for sealingly connecting a return pipe
to a roll bond evaporator, fig. 2 shows a second step of said method,
and fig. 3 shows a third step of said method.
The method according
to the invention is carried out in four distinct steps, the first one
of which comprises the insertion of a return pipe 1, with a capillary 2
enclosed therein, into a passage 3 formed between the two sheet layers
of a roll bond evaporator 4. The insertion of return pipe 1 into passage
3 has to be carried out in a manner ensuring that the two cylindrical
elements are maintained substantially coaxial with one another, or at
least with their respective surfaces out of contact with one another.
To
this purpose the diameter of return pipe 1 is selected to be slightly
smaller than that of passage 3, so that a space 12 of preferably about
o.2 to o.5 is defined between the two respective surfaces.
As
generally known, return pipe 1 is inserted to a predetermined position 5
of its inner end, while a certain length of capillary 2 projecting from
the end of return pipe 1 extends through a restriction 6 formed in a
linear extension 7 of return pipe receiving passage 3.
This
positioning has to be maintained throughout the three subsequent steps
of the operation, but then the operations of inserting the components
and fixing them in position can be readily and fully automatised by one
skilled in the art.
The second step comprises the compression of
passage 3 about an end portion 8 of return pipe 1, and of restriction 6
about capillary 2, and is performed in the conventional manner.
The
third step of the process comprises the injection of a semi-fluid
substance having sealing and adhesive properties into a further passage 9
obtained by suitably shaping the two sheet layers of the roll bond
structure. As clearly shown in the drawings, possage 9 has an outwards
opening port 10 at one end, and at the other, a port 11 opening into the
narrow space 12 defined between passage 3 of the roll bond structure
and the length of return pipe 1 inserted thereinto.
It is important that port 11 opens into the bottom portion of space 12 as shown in the drawings.
The
pressure applied for the injection of the semi-fluid substance is
effective to ensure that the substance progressively and completely
fills space 12 so as to fully replace the air originally contained
therein, the length of space 12 having been selected with a view to
achieving a reliable sealing effect.
It has thus been found that a
length of space 12 of at least 30 mm is sufficient to ensure such
reliable sealing effect to guard against gas losses, even when space 12
is not completely filled by the injected substance. Even when the air
has not been completely displaced from space 12, leaving a small air
pocket adjacent the closed end thereof, the desired sealing of the
connection will not be impaired.
As a matter of fact, the hermetic
sealing of the connection is substanti
ally brought about by the
injected adhesive substance forming an annular diaphragm between, and
bonded to, the outer wall surface of return pipe 1 and the inner wall
surface of passage 3, this diaphragm being impermeable to the passage of
gas from one side thereof to the other.
The formation of an
annular diaphragm having the above described sealing properties is
ensured by the injection of the sealing substance through the port 11
located, as has been pointed out, closely adjacent the bottom of space
12.
It is preferable to employ a substance of the anaerobic
polimerization type and of very low viscosity, and thus capable of
penetrating even the smallest gaps of space 12 by capillary action.
Preferred
in any case is the employ of a monocomponent anaerobic polymerization
substance, for instance TOPFIX NA 84 supplied by CECA company, which
requires a certain time for setting at least to a degree permitting the
evaporator to be subsequently handled as for mounting it in a
refrigerating appliance, without thereby endangering the previously
obtained seal.
Since this time interval is usually not available
in an automatized manufacturing process with high production rates, it
is advisable to provide a fourth step which consists in performing a
heat treatment of the area previously supplied with the sealing
substance, preferably by subjecting the respective area to induction
heating for a very short time, for instance 10 to 20 seconds, by the
employ of a technique generally known to those skilled in the art.
At
the end of this short period, the return pipe is perfectly sealed to
the roll bond structure, so that the evaporator is ready for further
processing.
The preceding description has been given on the
assumption that the capillary 2 is contained within the return pipe 1.
The teaching of the invention still holds valid, however, when the
capillary 2 is to be connected to the evaporator independently of the
return pipe.
The described method is thus conducive to obtaining
the following advantages: a) Rapid establishment of the connection
between the return pipe and the evaporator without the need for sealing
gaskets or other auxiliary parts, and without the necessity of a
soldering step, b) Simplified processing of the roll bond structure, c)
Simplification and flexibility of the manufacturing process (to be
carried out in separate steps capable of automatization), d) Overall
economy of the manufacturing process. e) Above all, the quality of the
connection is greatly improved as regards the obtention of a reliable
seal, particularly with a view to not readily detectable slow leaks.
It
is of course possible to design refrigerating appliances with
modifications of what has been described above within the purvieew of
the present invention.
REX (ZANUSSI) RI230/2T DEVICE FOR DRAINING WATER FROM A REFRIGERATING APPARATUS ON DEFROSTING THEREOF:
The invention relates to a device for draining water from a
refrigerating apparatus flowing from the evaporator thereof during the
defrosting phase. A device of this type essentially comprises a passage
extending through a wall of the apparatus and communicating with a
collecting receptacle for evaporating of the collected water. In known
devices of this type, the passage tends to become obstructed by food
particles, dust and the like carried in the drained water, necessitating
the passage to be regularly manually cleaned by the user. According to
the invention the passage has the approximate configuration of a venturi
nozzle, resulting in an air flow passing therethrough in opposite
directions as the door of the refrigerating apparatus is opened and
closed, whereby the passage is reliably kept free of obstructions.
1. Device for Draining Water from a Refrig erating
Apparatus on Defrosting Thereof Patent Claim A device for draining water
from the evaporator of a refrigerting apparatus on defrosting thereof,
said device comprising a water collecting receptacle located below said
.vporator and dimensioned in conformity to said evaporator, a duct
portion connected to said receptacle and paasng at least partially
through a respective thermo-insulated wall of said apparatus, and
optionally a drain conduit communicating with said duct portion and
extending along the outer surface of said wall, said conduit terminating
adjacent a further water collecting receptacle located in the lower
portion of said apparatus, characterlged in that said duct portion (10)
is of conical. configuration converging towards said wall (11) so as to
define a passage (12) of reduced cross-sectional area, and in that there
is provided at least one profile element (114) adapted to be secured
through said wall (11) together with said duct portion (10), said
profile element (114) being formed with a first conical portion (15)
adapted to receive said duct portion (10) therein, and a second conical
portion (16) converging towards said first conical portion (15) and
formed with a projecting lip (17) at a position above said conduit (21).
Description:
Device for Draining Water from a Refrig erating Apparatus
on Defrosting Thereof Description The present invention relates to a
simple device for collecting the water set free by defrosting the
evaporator of a refrigerating apparatus and for draining such water to
the exterior of the apparatus.
As generally known the defrosting
of the evaporator of a refrigerating apparatus is normally carried out
by utilizing the heat produced by suitable electric heater elements
disposed in heat-conducting contact with the evaporator, such heater
elements being periodically energized and deenergized by thermostatic
control means ip response to the terperature sensed thereby.
The
water set free by the defrosting operation is usually collected in at
least one receptacle disposed below the evaporator and dimensioned in
conformity therewith. The collected water is then drained to the
exterior of the apparatus through a cylindrical passage having a small
cross-sectional area connected to the receptacle and extending through
the rear wall of the apparatus.
The passage itself is connected to
a further conduit having a larger cross-sectional area and extending
vertically along 'the outer surface of the rear wall to terminate
adjacent a further collecting receptacle provided in a lower part of the
apparatus.
The water contained in the further receptacle is then
progressively evaporated by the heat produced by the condenser of the
apparatus, the latter being disposed along the outer surface of the rear
wall of the apparatus and extending partially into the further
receptacle.
In another embodiment the further receptacle is shaped
to conform to a top portion of the compressor and disposed in
heat-translttlng contact therewith, so that the water contained therein
is progressively evaporated by the heat transmitted from the compressor
to the receptacle, If in an apparatus of the type described the water
collected in the receptacle contained within the refrigerating cell
below the evaporator contains any food particles, dust or the like, the
described passage and conduit tend to become clogged after some time, so
that the water can no longer be drained from the interior of the
refrigerating apparatus.
As a result, the water will overflow into the interior of the refrigerating cell, with the resultant annoyance to the user.
To
avoid this troublesome occurrence, known refrigerating appliances are
supplied with a small hand tool which may be inserted into the bores of
the passage and/or conduit for cleaning them of obstructions of the type
described above.
In practical use it has been found, however,
that satisfactory results are only to be obtained if the user cleans the
passage and/or conduit at regular intervals in accordance with the
instructions by the manufacturer of the appliance.
On the other
hand, however, the cleaning operation is often carried out in an erratic
fashion or not at all, resulting in the passage and/or conduit becoming
permanently obstructed, necessitating their replacement or repair by
skilled service personnel.
The present invention aims at avoiding
the occurrence of this trouble yb providing a device for draining the
water from a refrigerating apparatus set free by defrosting there of,
the main object of the invention being the provision of such a device of
simple construction and simple and reliable operation, which is
effective to prevent the formation of obstructions of the above
described type without requiring any intervention on the user's part as
in known appliances of this type.
These and other objects are
attained according to the invention in a device for draining water from a
refrigerating apparatus on defrosting the evaporator thereof,
comprising a water collecting receptacle located below the evaporator
and dimensioned in conformity thereto, a duct portion connected to said
receptacle and passing at least partially through a respective
thermo-insulated wall of the apparatus, and optionally a drain conduit
communicating with said duct portion and extending along the outer
surface of said wall to terminate adjacent a further water collecting
receptacle disposed in a lower portion of the apparatus In accordance
with the invention, a device of the type defined above is characterized
in that said duct portion is of conical configuration converging towards
said wall so as to define a passage of diminishing cross-sectional
area,
and in that there is provided at least one profile element
adapted to be secured through said wall together with said duct portion,
said profile element being formed with a first conical portion adapted
to receive said duct portion therein, and a second conical portion
converging towards said first conical portion and formed with a
projecting lip at a position above said drain conduit.
The
specific construction of the device according to the invention ensures
that the passages thereof are effectively cleaned of any food particles,
dust and the like, without manual intervention by the user, on each
opening and closing operation of the door of the refrigerating apparatus
by the air flowing through the passage on each such opening and closing
operation.
The characteristics and advantages of the invention
will become more clearly evident from the following description, given
by way of example with reference to the accompanying drawings, wherein:
fig. 1 shows a diagrammtical cross-sectional view of a refrigerating
apparatus equipped with a draining device according to the invention,
and fig. 2 shows an enlarged detail of fig. 1.
A refrigeratign
apparatus shown in the drawings is in the form of a domestic
refrigerator 3 having a body 4 enclosing a refrigerating cell 5, and a
door 6 hinged to the forward portion of body 4 for opening and closing
cell 5 from in front of the apparatus.
Disposed in cell 5 is at
least one evaporator 7 secured i a conventional manner to a rear wall 8
thereof. Below evaporator 7 rear wall 8 is integrally forked with a
water collecting receptacle 9 dimensioned in conformity to evaporator 7.
Receptacle
9 serves the purpose of collecting the water leaking down from
evaporator 7 when the latter is defrosted by means of conventional
heater elements (not shown), and to direct the collected water to the
exterior of the apparatus in a manner to be described.
The lower
part of receptacle 9 is integrally formed with a duct portion 10 of
conical configuration converging towards the thermo-insulated rear wall
11 of the apparatus (fig. 2).
Duct portion 10 is of a length
permitting it to extend partially through rear wall 11, and is formed
with a passage 12 of diminishing cross-sectional area.
Inserted
between the inner panel 8 and an outer panel 13 of rear wall 11 is a
profile element 14 cooperating with duct portion 10.
Profile
element 14 has a first conical portion 15 dimensioned for receiving at
least part of duct portion 10 therein, and a second conical portion 16
converging towards first conical portion 15 and formed with a projecting
lip 17. Planar wall portions 18, 19 and 20 of profile element 14 permit
the latter to be positioned in and secured to rear wall 11 of the
refrigerating apparatus.
Profile element 14 is mounted in rear
wall 11 by first pushing first conical portion 15 onto duct portion 10,
followed by engaging wall portions 18 and 19 with outer rear wall panel
13, and wall portion 20 with inner rear wall panel 8 A further conduit
21 is secured in a con ventional manner tc the outer surface of outer
rear wall panel 13 at a position below projecting lip 17 of profile
element 124.
As shown in fig. 1, conduit 21 terminates at its
lower end adjacent a further collecting receptacle 22 mounted on a cover
23 of the compressor 24 of the refrigerating appar-atus and shaped to
closely conform to said cover.
Receptacle 22 is thus in
heat-transmitting contact with compressor 24, so that the heat emitted
by the latter is used for evaporating the water collected in receptacle
22.
Receptacle 22 is preferably provided with a partition 25 for preventing the water from splashing over the rim of the receptacle.
If
there is only a very small vertical distance between lip 17 of profile
element 14 and receptacle 22, conduit 21 may be eliminated, so that the
water flows directly into the receptacle.
On the other hand,
receptacle 22 may of course be of different design and located at other
positions as in known refrigerating appliances, as long as proper
evaporation of the collected water is ensured.
The formation of
the restricted passage 12 at the point of convergence of conical
portions 15 and 16 of profile element 14 results in the drain passage
being effectively cleaned of food particles, dust and the like carried
in the water set free by the defrosting operation, so that such water is
alway reliably drained into collecting receptacle 22.
This
cleaning operation takes place in an automatic manner on each opening
and closing operation of door 6 as a result of air flowing through
passage 12 in the directions of arrows A and B. respectively.
The
water draining device according to the invention is of simple
construction and reliable operation, and does not require manual
intervention on the user's part for cleaning passage 12, so that the
disadvantages and shortcomings of prior art draining devices are
effectively eliminated.
ZANUSSI MEL
ZEM E44601 R12, HERMETIC COMPRESSOR INTERNAL VIEW.
Note: Picture showing a bigger model but equivalent construction taken as example.
REX (ZANUSSI) RI230/2T ZANUSSI MEL ZEM E44601 R12. HERMETIC COMPRESSOR Lubrication of sealed compressor:
Improved lubrication of sealed compressors having a crankshaft provided
with a longitudinal interior duct and a tubular member coupled to a
lower end of the interior duct and having a substantially cylindrical
upper section and a substantially conical lower section adapted to be
submerged in oil. An upper end of the internal lubrication duct ends in a
first substantially conical section and a second substantially
cylindrical section of variable contour depending upon the profile of
the upper end of the crankshaft. A spring may also be situated inside of
the tubular member.
1. In a sealed
compressor including a sealed casing in which an alternating
motor-driven compressor assembly is housed, the assembly including a
vertical-axis crankshaft provided with a longitudinal interior
lubrication duct communicating with points on an exterior surface of the
crankshaft and with an upper end of the same eccentrically to the axis
of rotation thereof, said assembly also including a tubular member
coupled to a lower end of said interior duct of the crankshaft and
comprising a substantially cylindrical upper section and a substantially
conical lower section adapted to be submerged in oil,
the improvement comprising
an upper end of said interior lubrication duct ending in a first
substantially conical section and a second substantially cylindric
al
section of variable contour depending upon a profile of the upper end of
the crankshaft, and
the profile of the upper end of the
crankshaft cutting the duct at a transition point between the second
substantially cylindrical section of variable contour and the first
substantially conical section.
2. In a sealed compressor including a sealed casing in
which an alternating motor-driven compressor assembly is housed, the
assembly including a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on an
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof, said assembly also
including a tubular member coupled to a lower end of said interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
an upper
end of said interior lubrication duct ending in a first substantially
conical section and a second substantially cylindrical section of a
variable contour depending upon a profile of the upper end of the
crankshaft,
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
formed as a closed loop ending with a lower leg extending towards the
lower substantially conical portion of the tubular member.
3. In a sealed compres
sor including a sealed casing in
which an alternating motor-driven compressor assembly is housed, the
assembly including a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on a
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof, said assembly also
including a tubular member coupled to a lower end of said interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
an upper
end of said interior lubrication duct ending in a first substantially
conical section and a second substantially cylindrical section of
variable contour depending upon a profile of the upper end of the
crankshaft,
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
shaped as a substantially inverted U with two arms and bent according to
a profile of the lower conical section of the tubular member.
4. In a sealed compressor including a sealed casing in
w
hich an alternating motor-driven compressor assembly is housed, the
assembly including a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on an
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof, said assembly also
including a tubular member coupled to a lower end of said interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
an upper
end of said interior lubrication duct ending in a first substantially
conical section and a second substantially cylindrical section of
variable contour depending upon a profile of the upper end of the
crankshaft, and
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
shaped substantially as a U with upper free ends joined together and a
lower end shaped according to a profile of the lower conical section of
the tubular member.
5. In a sealed compressor including a sealed casing in
which an alternating motor-driven compressor assembly is housed, the
assembly inc
luding a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on an
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof, the assembly also
including a tubular member coupled to a lower end of the interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
formed as a closed loop ending with a lower leg extending towards the
lower substantially conical portion of the tubular member.
6. In a sealed compressor including a sealed casing in
which an alternating motor-drive compressor assembly is housed, the
assembly including a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on an
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof, the assembly also
including a tubular member coupled to a lower end of the interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
shaped as a substantially inverted U with two arms bent according to a
profile of the lower conical section of the tubular member.
7. In a sealed compressor including a sealed casing in
which an alternating motor-driven compressor assembly is housed, the
assembly including a vertical-axis crankshaft provided with a
longitudinal interior lubrication duct communicating with points on an
exterior surface of the crankshaft and with an upper end of the same
eccentrically to the axis of rotation thereof. the assembly also
including a tubular member coupled to a lower end of the interior duct
of the crankshaft and comprising a substantially cylindrical upper
section and a substantially conical lower section adapted to be
submerged in oil,
the improvement comprising
a spring situated inside said tubular member,
wherein said spring is constituted by an elastic and resistant wire
shaped substantially as a U with upper free ends joined together and a
lower end shaped according to a profile of the lower conical section of
the tubular member.
Description:
BACKGROUND OF THE INVENTION
The present invent
ion relates to improvements in the lubrication system of sealed compressors for cooling fluids.
Sealed
compressors for cooling fluids are known which include a sealed casing
with an alternating motor-driven compressor assembly housed in the
interior thereof, the assembly including a vertical-axis crankshaft
provided with a longitudinal interior lubrication duct communicating
with various points on the exterior surface of the crankshaft and with
an upper end of the same, eccentrically to the axis of rotation thereof.
The assembly also includes a tubular device coupled to a lower end of
the interior duct of the crankshaft, such tubular device having a first
upper section substantially cylindrical and a second substantially
conical section with an end having an orifice for the introduction of
oil.
In such compressors, the oiling of the parts that are in
friction is accomplished by means of the oil fluid supplied by the
tubular device, which, when rotating and immersed in an oil mass,
produces by centrifugal force the raising of the oil through the
interior duct of the crankshaft towards the oiling points of the
mechanism. Part of the oil exits out of the eccentric orifice at the
upper end of the crankshaft, propelled against the interior surface of
the sealed casing of the compressor.
There are various patents
that disclose particular details of this oiling or lubricating system.
U.S. Pat. No. 3,410,478 discloses a cylindrical tubular device joined by
a conical section, as well as a wall placed in the interior of the
tubular device acting as a gate, such a wall being costly to construct.
U.S. Pat. No. 3,451,615 discloses a lateral outflow passage from an
eccentric upper section of the interior duct of the crankshaft.
Lastly,
Spanish Patent No. 504,039 discloses a channel in the extreme upper
face of the crankshaft, arguing the lower cost of constructing such a
channel in relation to the lateral outflow passage disclosed in the
aforementioned U.S. Pat. No. 3,451,615.
It has been possible to
confirm that the current solutions of tubular pumping devices lose part
of their effectiveness as the compressor's operating temperature rises.
Under these conditions, the fluidity of the oil mass deposited in the
housing of the compressor reaches a point such that the oil mass loses
velocity of rotation in relation to the velocity of rotation of the
tubular device. Such device loses effectiveness as a centrifugal pump
due to sliding between the interior wall of the tubular device and the
layer of oil in contact with the wall.
The aforementioned
interior wall that acts as a gate may, in part, solve the problem
described, but it has the drawback of having a high cost of
construction. Moreover, the orifice at the upper end of the crankshaft
should have a certain form, so that the oil that exits therefrom has
sufficient force to be propelled against the interior wall of the sealed
casing of the compressor. This certain form, in the compressors that
are known, entails significant difficulties in construction.
SUMMARY OF THE INVENTION
With the improvements of the invention, the noted drawbacks can be eliminated.
Accordingly, it is an object of the present invention to elim
inate the drawbacks noted above with respect to the prior art.
It is also an object of the present invention to simplify the lubrication of compressors.
It is another object of the present invention to lower manufacturing cost of a lubrication system for compressors.
It
is a further object of the present invention to compensate for the
decrease in oil viscosity caused by a rise in temperature in the
lubrication system of a compressor.
These and other objects are
attained by the present invention which is directed to improvements in
the lubrication system of compressors for cooling fluids. According to
the present invention, the upper end of the interior lubrication duct in
a crankshaft of the compressor ends in a first substantially conical
section and a second substantially cylindrical section of variable
contour depending upon the profile of the upper end of the crankshaft.
This distinct configuration of the upper end of the lubrication duct
offers the advantage of greater simplicity in construction and
consequently a lower manufacturing cost, while at the same time
maintaining the same efficiency as other current forms of more
complicated configuration.
Advantageously, the tubular device,
which is coupled to the lower end of the interior duct of the
crankshaft, is provided in its interior with a spring formed by an
elastic and resistant wire affixed by means of pressure and by insertion
of a part of the spring in a substantially conical section of the
tubular device or member submerged in oil (the tubular devic
e comprises a
first substantially cylindrical upper section and a second
substantially conical lower section adapted to be inserted into oil).
The part of the spring submerged in the oil acts as a paddle propelling
the oil, and thereby compensating for decrease in oil viscosity caused
by the temperature.
The aforementioned spring may have various
forms or structures in accordance with the present invention. In one
embodiment, the spring forms a closed loop which ends with a lower leg
thereof extending towards the lower substantially conical portion of the
tubular device or member. In a second embodiment, the spring takes the
form of two arms making a substantially inverted U, and bent according
to the conical profile of the tubular device. In another embodiment, the
spring takes the form of two arms shaped in a U and bent according to
the conical profile of the tubular device and with the free ends thereof
joined at the upper portion thereof.
All the noted spring shapes
may be constructed with wire having a circular or a square
cross-section so as to improve the attachment thereof within the
interior of the tubular device or member.
BRIEF DESCRIPTION OF THE DRAWINGS
For
a fuller understanding thereof, the present invention will be described
in greater detail below with reference to the accompanying drawings in
which certain embodiments of the present invention are schematically
illustrated and to which the present invention is not intended to be
exclusively restricted.
In the drawings,
FIG. 1
illustrates a longitudinal sectional view of a sealed compressor of
cooling fluids, in which the improvements according to the present
invention are applied;
FIG. 2 is a partially sectional side view
of a crank shaft and of a tubular device having the improvements
according to the present invention; and
FIGS. 3 and 4 each illustrate springs for the tubular device illustrated in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring
to FIG. 1, a compressor 1 includes a sealed casing 2 with an
alternating motor-driven compressor assembly housed in the interior
thereof, the assembly including a vertical-axis crankshaft 3 provided
with a longitudinal interior lubrication duct 4 (FIG. 2) communicating
with various points 5,6 on the exterior surface of the crankshaft 3, and
with the upper end 7 of the same, eccentrically to the axis of rotation
thereof. The assembly also includes a tubular device 8 coupled to a
lower end of the interior duct 4 of the crankshaft 3, the tubular device
8 comprising a first upper section 9 that is substantially cylindrical
and a second lower substantially conical section 10 to be submerged in
oil.
As can be seen in FIG. 2, the upper end 7 of the lubrication
duct 4 terminates in a first substantially conical section 11 and a
second substantially cylindrical section 12 of variable contour
depending upon the profile 13 of the upper end 7 of the crankshaft 3.
As
also illustrated in FIG. 2, the tubular device 8 is provided in the
interior with a spring 14 formed by an elastic and resistant wire, e.g.
of tempered steel, and affixed by means of pressure and by insertion of
part of the spring in the conical section 10 of the tubular device or
member 8 which is adapted to be submerged in the oil. As shown in FIG.
2, the spring 14 takes the form of two arms 15 and 16 shaped into an
inverted U and bent at points 17 and 18 according to the conical profile
of the tubular device or member 8.
In FIG. 3, the spring 14
forms a closed loop 19 ending with a lower leg 20 thereof extending
towards the lower conical part 10 of the tubular device 8.
The
spring illustrated in FIG. 4 takes the form of two arms 21 and 22 in the
shape of a U bent at points 23 and 24 according to the conical profile
of the tubular device 8 (i.e. the lower substantially conical section 10
thereof) and with the free ends 25 and 26 thereof joined at the upper
portion as illustrated.
As described above, the springs are
introduced into the tubular device 8 with the lower portion thereof
situated in the conical section 10 to be submerged in oil. When the
crankshaft 3 rotates, driven by the rotor of the electrical motor, the
tubular device 8 rotates along with spring 14, with the lower part of
the spring submerged in oil acting as a paddle.
The
characteristic form 11 of the outflow orifice in the upper end 7 of the
lubrication duct 4 permits the oil that flows through the eccentric duct
4 to be propelled in a continuous jet against the interior wall of the
casing 2.
It follows from the description above that the
improvements according to the present invention allow for enhancement in
the lubrication of the crankshaft and in the propulsion of oil against
the interior wall of the casing 2 due to the springs 14 acting as
paddles, and allows for a reduction in the cost of manufacture of the
crankshaft 3 by simplifying the orifice at the upper end 7 of the
crankshaft 3 without diminishing the effectiveness thereof. Similarly,
the cost of construction of the spring 14 is much lower than the
previously described interior wall with respect to the prior art.
The
preceding description of the present invention is merely exemplary, and
is not intended to limit the scope thereof in any way.
REX (ZANUSSI) RI230/2T Method of and apparatus for sealing tubes constructed of metals of high thermal and electrical conductivity:
1. A method of welding
together pieces constructed of metals of high thermal and electrical
conductivity, wherein a piece to be welded is placed in contact with at
least one electrode of negative temperature coefficient, so as to
receive the heat energy which is developed therein when it is connected
to a source of electricity.
2. A method as claimed in Claim 1, wherein the piece
or pieces to be welded together are placed in contact with a pair of
electrodes ol' negative temperature coeffici so as to establisll
electrical continuity between said electrodes and receive the energy
which is developed in these latter as a consequence of the establishment
of the electrical continuity.
3. A method as claimed in the preceding Claims,
wherein the electrodes are resiliently pressed on to the piece or
pieces.
4. A method as claimed in the preceding Claims, wherein the welding is brazing.
5. A method as claimed in the preceding Claims,
wherein the welding takes place as a result of plasticising.
6. A method as claimed In Claim 4, which is used for
joining together elements of a refrigeration circuit, in particular a
capillary tube and a tube of greater diameter.
7. A method as claimed in Claim 6, wherein the tiie
tulle oi' greater diameter is previously deformed mechanically to
provide a seati ii# i'c,r the capillary tube, and to form a socket
region for receiving the brazing material
8. A method as claimed in Claim 4 and in one of the
remaining Claims, wherein, at least llnti ] the moment in which the
brazing material begins to melt, the intensity of the current
circulating through the electrodes is kept at a higher value than during
the time in which the electrodes are still maintained in contact witij
at least one of the pieces to be joined together.
9. A method as claimed in Claim 8, wherein the
intensity of the current circulating through the electrodes is decreased
for at least part of the time subsequent to the moment in which the
brazing material begins to melt, by connecting at least one resistive
component in series with the electrodes.
10. A method as claimed in Claim 5 and one or more
of the remaining claims, wllich is used for sealing a tube of a circuit
containing a fluid under pressure.
11. A method as claimed in Claim 10, wherein the
tube is meelBlically deformed on both sides of the weld before the weld
is made.
12. An apparatus for carrying out the method as
claimed in the preceding Claims, comprising at least one electrode ol'
negative temperature coefficient, and means for connecting it to a
source of electricity.
13. An apparatus as claimed in Claim 12, wherein the
means izor connecting it to the source of electricity comprise the
actual piece or pieces on which the electrode acts.
14. An apparatus as claimed in Claim 12 and/or 13,
comprisillg a pair of electrodes of~ negative temperature coefficient
which are mobile substantially in the same plane but in opposite
directions, and between which the piece or pieces, used as tlie
electrical connection means, are gripped
15. An apparatus as claimed in one or more of Claims
12 to 14, comprising a switch for connecting a resistive component I in
series with the electrodes.
16. An apparatus as cm aimed in Claim 15, wherein
the switch is controlled by a thermostat.
17. An apparatus as claimed in Claim 14, wherein at
least one electrode is mounted resiliently yieldable in a mobile
operating head wliicl, comprises at least one jaw for deforming the
piece, in particular for mechanically closing a tube.
18. An apparatus as claimed in Claim 17, comprising
two mobile heads and control means for moving said heads.
Description:
Method of and apparatus for welding together pieces constructed of metals of high thermal and electrical conductivity.
This
invention relates to a method of welding together pieces constructed of
metals, which can be different, but which have high thermal and
electrical conductivity.
Although the invention can be applied to
many fields, those of particular interest are a) joining a copper tube
to an aluminium tube, for example in the refrigeration circuit oi' a
domestic refrigerator, and b) sealing the copper tube through which the
refrigerant fluid is charged into the refrigeration circuit of a
domestic refrigerator.
In case a) , the copper tube can be the
capillary tube and alluminium tube the evaporator and/or the suction
tube of the compressor in the circuit. The capillary tube is that
element of the refrigeration circuit in which the (theoretically
isenthalpic) expansion occurs of the liquid refrigerating fluid whicli
leaves the condenser to then enter the evaporator. As the undercooling
of the capillary tube increases the useful effect of the refrigeration
circuit, it is usual to insert a portion of the capillary tube in said
suction tube.
It is therefore necessary to make at least one joint
at the point in which the capillary tube enters the suction tube. A
further joint is usually necessary at the point in wliic the capillary
tube enters the evaporator, particularly if this latter is in the form
of a tubular coil. As it must be ensured that the refrigeration circuit
is absolutely hermetically sealed, the quality of the joints must be
excellent, in spite of the difficulties due to tulle fact that the two
pieces to be joined together are dii'ferent from each other, and have
such a high electrical conductivity that it is impossible to make the
joint by conventional resistance welding.
Again with reference to
case a), a Jointing system is known which uses a short auxiliary copper
tube having an outer diameter intermediate between the diameter of the
capillary tube and the diameter of the aluminium tube. The capillary
tube passes through said auxiliary tube, and is joined to one end
thereof by torch brazing.
The other end of the auxiliary tube is joined to the aluminium tube by further brazing or by pressure welding.
This
jointing system is certainly of good quality, but is relatively
complicated and above all costly because of the copper construction of
said auxiliary tube. The absolute value of this cost is very high when,
in a modern industry, daily production amounts to several thousands of
refrigerators.
With regard to case b), in the known method the
copper charging tube is firstly closed by mechanical deformation using a
clamp, and then, with the clamp applied, it is filled from its open end
with a brazing material melted by means of a torch. This method has the
disadvantage of not completely ensuring the opening of the welding
zone, requiring the use of specialised labour and involving the use of a
large quantity of brazing material when related to a daily production
of several thousands of refrigerators.
The object of the present
invention is to provide a new welding method, in particular for joining a
copper capillary tube to an aluminium tube, and for closing the end of
t}ie charging tube of a refrigeration circuit, in which low cost and
simplicity of operation are attained together with excellent weld
quality.
According to the method of the invention, a piece to be
welded is placed in contact with at least one electrode having a
negative temperature coefficient so as to recieve the heat energy
developed in it when it is connected to a source of electricity.
In
a preferred embodiment of the method ac cordillar to the invention, he
piece or pieces to be welded together are placed in contact with a pair
of electrodes having a negative temperature coefficient so as to
establish electrical continuity between these electrodes and receive the
heat energy which is developed in these latter as a consequence of
establishing electrical continuity.
The term electrode having a
negative temperature coefficient" indicates an electrode, the electrical
resistallce of which decreases as the temperature increases.
The
heat transmitted by the electrode or electrodes to the piece or pieces
melts the welding material in contact with the piece, or at least
transforms the piece into its plastic state so that, in this latter
case, it is sufficient for the electrodes to exert a low pressure on the
piece to form the weld.
The apparatus which enables the method to
be carried out and is also part of the invention comprises at least one
electrode of negative temperature coefficient, and meals lor conne
cting
it to a source of electricity.
In the preferred embodiment of the
apparatus, the mealls for connecting it to tulle source OS' electricity
comprise the actual piece or pieces on which the electrode is to act.
In
the most advantageous embodinlent of the invention, the apparatus
comprises a pair of electrodes of Negative temperature coefficient,
which are mobile sub staiitially in the same plane but in opposite
directions, and between which are gripped the piece or pieces to be
welded, these latter being utilised as the electrical connectioii means.
All
the characteristics and advantages of the present invention will be
apparent from the description given hereinafter (which, as a
non-limiting example of application of this method, relates both to
joining a copper capillary tube to an aluminium suction tube of the
refrigeration circuit oi a domestic refrigerator by brazil and to
sealing the end ol the charging' tube of such a refrigeration circuit)
and from the accompanying drawing, in which:
: Figure 1 is a
sectional diagrammatic view, through their axes, of two tubes during the
operations involved in their joining; Figure 2 is a cross-section
through said tubes on the line Il-Il of Figure 1 after the joint has
been completed and the electrodes used have been removed; Figure 3 shows
the electrical circuit used for melting the brazing material; Figure 4
shows the variations in the current intensity through the suction tube
and its temperature adjacent to the electrodes during the joining by
brazing; Figure 5 is a side view of the apparatus for welding (sealing)
the charging tube of a refrigeration circuit; Figure 6 is a section on
the line VI-VI of Figure 5, and Figure 7 shows a portion of the charging
tube after its sealing.
With reference to Figures 1 and 2, a
copper capillary tube 1 is inserted directly into a portion of an
aluminium tube 2, for example representing the tube which constitutes
the evaporator of a refrigeration circuit of a domestic refrigerator.
There is thus a first great financial advantage in eliminating the
aforesaid auxiliary copper tube. The aluminium tube 2 can have an outer
diameter of 10 mm (against the 2 mm of the capillary tube 1), and has
previously been mechanically deformed over a small portion 3 just after
the mouth 4 to provide a flare 5 and a double lobed section at said
portion 3 (see Fig. 2).
The brazing material and its de-oxidising
agent are placed in the flare 5. These substances are indicated together
by the reference numeral 6. The brazing material tried by the applicant
in the example of the application of the method described here was the
alloy known commercially as "So) dwiiol 1 265" of Messrs. Degussa ( the
alloy carries the symbol L-CdZn 20, in accordance with D1N 1707). This
is a eutectic cadmium-zinc alloy with Hs.5es of cadmium and a melting
point of 266 C. The de-oxidising agent tried was wSoldaflux AL" of
Messrs.
Degussa (carrying the symbol F-LW 3, in accordance with
DIN 8511), its action being effective over the temperature range of 200
to 300 C.
According to the invention, the high conductivity of the
aluminium with which the tube 2 is made is utilised to melt the brazing
material. Thus the aforesaid technical and economical drawbacks due to
the use of torch brazing are obviated. For this purpose, an electrical
circuit (shown diagrammatically in Fig. 3) is constructed comprising the
terminals 7 and 8 which receive an alternating single phase current
from the secondary winding of a voltage step-down transformer (not
shown), supply cables 9 and 10, and a pair of electrodes 11 and 12 of a
material such as graphite which has a negative temperature coeffi cient.
By the Joule effect, the electrical energy at the electrodes 11 and 12
is transformed into heat which reaches the brazing material by
conduction through the tube 2.
These electrodes are brought into
contact with the portion 3 of the tube 2 at the beginning of brazing.
ln the electrical circuit diagrai ot' Fig. 3, the electrodes are shown
as two variable resistor with the said reference numerals 11 and 12,
whereas the reference numeral 13 indicates the resistance, obviously of
extremely low value, of the tube 2 through which tulle circuit is made.
The
circuit also comprises a switch 14 wlich, according to the control
signals which it receives from the regulator 15, can be shifted from
tulle contact 16 to the contact 17 to connect into the circuit a
secondary branch 18 which comprises a high ohmic resist or 19.
The
reglll ator 15 can be any device able to cause said resistor 19 to be
connected in series with the electrodes 11 and 12 and tube 2 when the
brazing material has reached its melting point, so reducing the current
intensity l in the electrical circuit. In this respect, the applicant
has fouiid that this lives an energy saving because the absorbed power
of the circuit call be reduced by as much as 7596 during tlie second
brazing stage (i.e.
when the switch 14 is closed on tlie contact
17) with respect to the first stage (i.e. when the switch 14 is closed
on the contact 16). Advantageously, said regulator 15 is a rapid
response thermostat, the sensor of which determines the temperature of
the aluminium tube 2 in the immediate vicinity of the point in which it
is joined to the capillary tube 1.
However, the regulator 15 can
be in the form of a timer, provided it is known accurately after what
time from the beginning of the operation the timer must shift the switch
14 from the contact 16 to the contact 17 (on the basis of all accurate
trial run of the brazing operation).
The variation in current
intensity I (measured in amperes) passing through the tube 2 during
brazing, and the variation in temperature in C of this tube ( which can
be sprayed with a conventional coolant after' brazing) shown in Figure 4
have been obtained by tests carried out by the applicant.
After
the brazing material has melted, the electrodes 11 aiid 12 are removed
from contact with the portion 3 of the tube 2, so that it is possible to
remove this latter (now joined to the capillary tube 1) and proceed to a
further brazing operation. In Figure 1 the approach and withdrawal of
the tube electrodes are shown by arrows.
Fiiially, it silould be
noted that in this example the el ectiodes do not exert any mechanical
deformation action on the pieces to be joined together ( the tubes 1 and
2 in tills example). Thus(also because of the fact that the material of
which the electrodes are made has a Ilegative tell1J#erature
coefficient, i.e.
its electrical resistance decreases as its
temperature increases) the method described herein is conceptually the
opposite of collventional resistaiice welding of ferrous metals, which
have a relatively high thermal and electrical conductivity.
The
advalltages of the method according to the present invention can be
suiirtriarised as follows: pieces made of materials of high electrical
and thermal conductivity can be joined together by brazing other than
torch brazing, and thus more simple to carry out and of much higher
reliability; the energy consumption can be considerably reduced by not
supplying excess energy when this is not required; in tlie particular
case of joining a capillary tube to an aluniinium tube, it is no longer
necessary to use an intermediate auxiliary tube.
With reference to
Figures 5 to 7, which show the sealing of the tube for charging the
refrigeration circuit of a domestic refrigerator with refrigerant fluid,
the tube in question, constructed for example of copper, is indicated
by the reference numeral 100. It is welded to the casing 101 which
contains the compressor and its electrical drive motor (not shown), and
communicates with the casing interior.
In order to introduce the
refrigerant fluid, a connector element 102 incorporating a non-return
valve 103 is mounted on the free end of tle tube 100 by well known
methods. Again by well known methods, a charging pistol is connected to
the connector element, and when operated causes pressurised refrigerant
fluid to flow into the circuit. After the charging operation, the pistol
is disconnected from the connector element, and the circuit then
contains pressurised refrigerant fluid which cannot escape because of
the non-return valve 103.
The problem solved by the invention is
to properky seal the tube 100 after said charging operation, without
usi)ig welding material.
According to the inventioll, the problem
is solved by causing localised plasticising or fusion of the charging
tube, mainly by the lleat given up by electrodes 104, 105 of negative
temperature coefficient, for example of graphite, which are moderately
pressed from opposing sides against the tube and thus cause permanent
sealing of the tube by welding as a result of the plasticising or fus
ioll .
Advai)te(J;eousiy, to prevent the pressurised refrigerant
fluid iii the circuit from being able to escape through tlle passages
wllic}l can open up in the plasticising or fusion zone, the tube is
closed before welding and maintained closed during welding, by
mechanical deformation exerted in a zone between the electrodes 104, 105
and the casing 101, and optiollally also in a zone between the
electrodes and tulle free end of the charging tube.
The said
operations are carried out by the device shown in Figures 5 to 7,
comprising electrodes 104, 105 and means for localised temporary
mechanical closure of the tube.
Tulle device in question comprises
a pair of levers 106, 107 rotatable about their pivots 108, 109, and
supported at their ends in a pair of parallel fixed side plates 110.
Each
lever 106, 107 comprises at one end a working head 111 in which the
electrode 104, 105 is disposed, and at the other end a roller 112 which,
urged by springs 113, 114, is kept in contact with the end of a rod 115
of a piston 116. This piston is slidably mounted in a cylinder 117, and
on one of its ends there acts a return spring 118 and on the other end
there acts a pressurised fluid fed for example through a solenoid valve,
not shown.
The end part 119 of the rod 115 is conical so that
when the pressurised fluid is fed into the cylinder 117, the consequent
movement of the piston 116 in the direction of the arrow A causes the
levers 106, 107 to rotate in such a direction as to cause the working
heads 111 to approach each other.
These heads comprise a fork
structure with a pair of anns 12(), 121, the purpose of which is to
deform the tube 100 at tlie two sides of the electrodes 104, 105 wheii
the rod 115 is moved in the direction of the arrow A.
Each
electrode 104, 105 is removably housed in a dovetail cavity 122 provided
in a partly slotted metal block 123, with ducts 124 for the passage of
cooling water ied through flexible hoses, not shown. Tlie block 123 is
provided witlj a shank 125 of polyg'oiiai or square crosssection
slidable in a bore of correspolldillg cross-section provided in tlie
crosspiece 126 of tlse fork structure. The shank 125 comprises a head
127 against which a compression spring 128 acts,
its other end resting against a wall 129 rigid with the fork structure.
In
the device concerned, the electrical circuit extends from the terminals
B and C of an electricity source, through the electrodes 104, 105 and
through the tube 100, when this latter is in contact with the
electrodes.
The tube and electrodes are therefore in series when
the device operates. The circuit is opened when the electrodes 104, 105
withdraw from the tube 100 following the return of the rod 115. Thus the
welding operation, which will be discussed in greater detail
hereinafter, can be controlled by the operator by operating the valve
(e.g. a three-way valve) associated with the cylinder 117.
Operation
is as follows: The two heads 111 are initially spaced apart from each
other to allow the insertion of the tube 100 to be sealed (welded). When
the tube is dosed between the heads, the operator feeds fluid under
pressure to the cylinder 117. The rod 115 moves in the direction of the
arrow A, the levers 106, 107 rotate about the pivots 108, 109, and the
heads 111 approacl# the tube 100. The electrodes 104, 105 firstly touch
the tube at the point N, but electricity is not as yet fed to the
electrical circuit, even though this is ready to receive it.
The
arms 120, 121 tlien act on the tube to deform it and close it
mechanically in two zones K and M to tlie sides of the welding po
int N,
this point being where the electrodes act.
The connector element 102 caii not be removed.
Electricity
is now fed to the terminals B, C (e.g. by means of a contact) and flows
in the circuit which is closed through the electrodes 104, 1()5 and
tube 100. The electrodes 104, 105 progressively increase in temperature
and thus heat point N to a sufficient extent to transform it into its
plastic or partly molten state so that the small pressure wlsich the
electrodes exert on the tube (by virtue of the springs 128) is
sufficiei,# to produce deformation and corlsequent welding (when the
opposing sides of the tube come into contact with each other).
On
termination of welding (sealing), the operator unloads the cylinder 117,
the two heads 111 withdraw from the tube and as the circuit is broken
the electricity no longer traverses the electrodes 104, 105, which
therefore cease to heat up.
The apparatus is thus ready for a new working cycle.
The
present invention covers any other field of application of the
described method, comprising the joining together of more than two
pieces and the utilisation of the conductivity of all or some of the
metals of which the pieces are constructed, to perform the welding, i.e.
the fusion of the brazing materials.