ITUD960011U1 - EVAPORATOR FOR REFRIGERATORS - Google Patents

Abstract

Handle structure for containers such as pans and the like, comprising a longitudinal tie rod with a polygonal head (18) and a knob (16) with a housing for the polygonal head. The knob is axially movable with respect to the tie rod between an active position, in which it is keyed in rotation with the head for the rotation of the tie rod during locking / unlocking of the handle to the container, to a passive position, in which the knob is constrained in rotation from the polygonal head, to rotate freely while remaining the tie rod. FIGURE 5.

Description

Patent description for industrial model

Title:

Evaporator for refrigerators

The present invention relates to an evaporator for refrigerators. State of the art

At the present state of the art it is known that the main component of the refrigeration circuit refrigerator is the evaporator, that is a part of the circuit in which the refrigerant fluid expands (eg freon, isobutane R600, R134A, and other equivalent fluids). The refrigerant fluid is previously compressed by the compressor and after passing through an external heat exchanger as a condenser, it is sent into said evaporator by means of a capillary tube.

The capillary tube generally conveys the compressed refrigerant fluid to the evaporator in a practically liquid form. This fluid, flowing free into the evaporator expands and becomes gaseous, subtracting calories and thus cooling the surrounding area.

This happens due to the known fluid dynamics law PV = RT = constant, where P indicates the pressure of the fluid, V indicates its volume, T indicates the absolute temperature = -273 C ° and R is a constant.

on the basis of the above formula it is therefore known that to reduce the pressure the volume is increased or vice versa, ie the said compressed refrigerant fluid is left free to expand and exits from the capillary tube and in this way cooling is obtained.

This expansion occurs inside a conduit made in said evaporator which takes its name precisely from the fact that when the refrigerant fluid is compressed in the capillary it is substantially liquid and when it comes out of it, thanks to its free expansion, it evaporates immediately and expands by subtracting heat from the walls of the evaporator which for this reason cool the surrounding environment of the cold room.

The refrigerant fluid then circulates freely in the evaporator and is then sucked through the return pipe from the compressor.

The gaseous refrigerant fluid is compressed again by the compressor, which is external to the refrigerator compartment.

Compression entails a considerable increase in the temperature of the refrigerant fluid, so that it is made to pass after passing through a finned coil tubular condenser, always placed outside the cold room, generally on the back of the refrigerator.

The finned condenser releases heat to the ambient air and cools down, the cooling determines the condensation of the compressed gas, making it liquefy, for this reason this external heat exchanger is called a condenser.

The compressed liquid refrigerant then passes into a very small diameter tube called the capillary tube, which flows into the evaporator as mentioned.

The cycle is repeated in a closed circuit and cooling continues. To reduce the costs of the refrigerant circuit, a single coaxial duct is generally used, i.e .:

• a return pipe of the refrigerant fluid in gaseous form from the evaporator (which has an internal diameter substantially greater than the external diameter of said capillary tube), and

• the said capillary tube (with a much smaller diameter than the first), coming directly from the condenser, which is inserted inside the return tube and the whole is sent to the evaporator which is placed inside the refrigerator compartment.

The reasons for this inclusion of the said capillary tube, within the return tube, are dictated:

- both for efficiency reasons to further cool the capillary with the returning coolant still cold coming from the evaporator;

- both for technological reasons of constructive economy as with this system only one pipe has to be welded to the evaporator.

To obtain this result, however, it is necessary to have an absolutely hermetic closed circuit, not in contact with the air and without leaks, so that the evaporator has a circuit that is also closed on a single mouth as a manifold, where yes branches directly to "Y" with a delivery duct, generally straight with respect to the mouth in the form of a manifold sleeve, and a return duct, generally at 90 degrees with respect to the first and near said mouth, where it will be entered and provided to the welding of the coaxial pipe leading to the condenser and compressor.

The welding of said coaxial pipe takes place in such a way that:

• the external return pipe is welded immediately at the inlet, within the respective nozzle manifold sleeve, allowing free connection with the evaporator return pipe, while

• the capillary tube continues beyond said return duct until it engages within said evaporator delivery duct.

There must be no communication between the outside of the capillary tube and the inside of the delivery duct, otherwise the closed circuit would not take place, so the following steps are carried out for the connection:

• fill with a sealing paste around the end of the capillary tube;

the return tube is inserted with the respective protruding capillary tube, within the mouth in the sleeve of the evaporator manifold, so that the paste at the end of the capillary clogs the surrounding area of the delivery branch;

• a first section of the outgoing branch of the evaporator is crimped, so that this crushing, with the aid of said sealing paste, completely occludes the rearward opening of the outside of said capillary tube (in this in this way the capillary tube will open only into the outgoing duct of the evaporator and the refrigerant fluid will only be able to expand within said outgoing duct as an evaporation duct.

The refrigerant fluid is forced to travel through the entire circuit provided in the evaporator (circuit which involves a significant increase in volume) and will return after having traveled through the entire evaporator circuit, through the return duct entering annularly outside the said capillary tube. and inside said return pipe.

The exterior of the said return pipe is welded onto the said sleeve of the manifold inlet duct, by brazing or by means of filler material in inert gas (T.I.G. system), so as to have a perfectly watertight seal.

Advantageously, the evaporator is made:

Formerly by joining two aluminum sheets with the interposition of an alloy sheet and subjecting to temperature, of which at least one was preformed to provide between the two sheets the desired refrigerating circuit for evaporation of the refrigerant fluid.

In today's technique, the evaporator plate is made with the coupling, by means of a lamination process, of two or more layers of aluminum alloy tape according to the "Roll Bond" technique. screen printing, the circuit which will receive the refrigerant fluid and which, in fact, constitutes in the lamination phase a solution of continuity between the layers, allowing it to detach at the desired height, by means of a subsequent inflating action.

As mentioned, the refrigerant circuit piping is a set of a connection pipe between the evaporator and the rest of the refrigeration circuit and can be made of aluminum and copper with a traditional bimetallic junction (made of resistance or spark) and a coaxial capillary which it acts as a lamination valve for the refrigerant fluid. Drawbacks of the state of the art

The aforementioned operation is extremely complex and expensive.

In particular, it has been found that the complexity and cost substantially derive from the last step of brazing or welding with filler material in an inert environment.

In fact, due to the complexity of the system, this welding operation cannot be done mechanically or automatically, but only manually, and in particular it is not possible even a robotization at convenient costs.

The cause of this is due to the continuous variation of the shapes of the evaporator and of the coupling positions of the coaxial pipe of the refrigeration circuit.

Initially, brazing systems were used with the use of an alloy with a very high silver content (therefore extremely expensive) with a traditional manual torch system.

This technique of using silver alloys was in demand:

- both for the need to keep the brazing temperature low;

- both to make possible a maximum penetration, due to the capillarity principle, of the molten alloy in the interstice or interspace between the outside of the return pipe and the manifold inlet manifold of the evaporator.

In the absence of the use of expensive high quality alloys of silver, copper, zinc, and other metals, poor welding results were obtained:

• both for the need to raise the welding temperature further with easy evaporation of the flux and therefore easy formation of aluminum oxide which actually hindered the welding between metals;

• both for the reduced fluidity of the alloy

Today, an electric arc welding with tungsten electrodes and with filler material in inert gas known as the T.I.G. system is generally used. (Tungsten Inert Gas).

But even this solution has strong qualitative limits, particularly due to the manual ability that involves a variability and therefore the (danger of defective welding, for example of oxidation of the surfaces to be welded or for not complete care of the welding operation.

These operations must be done manually by a single operator, which hinders mechanization at acceptable costs.

The system is also dangerous because it forces the operator to work in the presence of electromagnetic waves and in a toxic environment, for which it requires the use of particular shielding elements and the presence of suitable ventilation and suction systems.

A further problem also arises from the fact that, as is known, the welding areas are always areas with a different chemical-physical-mechanical characteristics with respect to the two elements being welded.

In fact, the welding areas are known as areas of possible corrosion and cracks.

This teaches him not only the technique but also and above all the experience. See, for example, the technique of aeronautical constructions where still today re-embossing is used instead of welding for the joining of light alloy elements (sheets).

This is particularly obvious in the case of continuous dynamic stresses, which can precisely cause cracks and fissures that lead to definitive failure.

It is now known that, albeit indirectly, said coaxial pipe is also subject to continuous vibrations imparted by the compressor, which are transmitted for good or bad, albeit in a reduced form, also to the welding area to the evaporator, with the risk of breaking in the long run.

Laboratory experiences in this sense have amply proved the above stated.

The welds must be made with maximum accuracy and the welding area must be very thickened with a considerable amount of filler material, this involves not only a consumption of material in addition to what is strictly necessary for the actual welding, but also a worsening of the aesthetic aspect.

The possible external cleaning of the weld itself is also expensive.

Purpose of this innovation

The purpose of the present invention is to obviate the aforementioned drawbacks and make it possible:

• not only to completely mechanize the production of the evaporators, overcoming the problems of manual welding described above, but also to provide a qualitatively and performing better product, and this in its entirety or at least in the area that affects the said welding area ;

• and this at possibly lower costs.

Revelation of the innovative essence

This and other purposes are achieved as claimed by means of a new evaporator unit of the type which comprises an evaporator plate made of aluminum or its alloys, to which a metal pipe of the refrigerant circuit is inserted into a corresponding junction area, in a corresponding collector sleeve. mouth of the evaporation circuit of said evaporator, characterized in that:

- the external surface of at least said junction area is covered with a layer of molten metal made adherent by immersion;

- the interspace of said graft is sealed by penetration of the same molten metal that covers the surrounding external area.

Advantages of the invention

In this way, not only is a qualitatively superior evaporator obtained in terms of resistance to wear, corrosion, etc., but a better seal and sealing is also guaranteed and the production system can also be completely mechanized because the evaporator units can be conveyed. in continuous or stepwise line of advancement, then in a continuous cycle.

And the above in a completely automatic way without the need for operators, since the shape of the evaporator or the position or width or shape and number of couplings are independent.

Furthermore, in this way, in a single operation, all the welds, even of several couplings, are carried out at the same time.

Costs are therefore significantly reduced

The resulting advantages are enormous and such as to fully justify the very important technological innovation, which despite using widely known technologically knowledge, it has been possible to combine them in a way hitherto unimaginable with immediate repercussions both on qualitative production and on cost and safety no longer needing to labor.

In other words, the metal bath replaces the need for welding or brazing, as the grafts are intimately blocked by the penetration of molten metal within them, which provides an equal if not superior performance.

In fact, the said metal bath not only allows the metal to penetrate by capillarity between the male and female of the grafts, but also forms an external protective coating layer.

In fact, it is known that in the case of bimetallic pipes (part of the aluminum pipe and part in copper, galvanic currents are created which cause corrosion. Passivation therefore provides not only the advantage of surface protection against wear but also adequate protection against corrosion.

The evaporator can then be safely subjected to further painting, with the advantage that at least in the welding area (or the entire evaporator if completely immersed in the metal bath) it will have a double protective layer against wear and oxidation corrosion. .

Advantageously, the evaporator used and the said return pipe are made of aluminum or aluminum alloy and the said molten metal is an alloy substantially of zinc and aluminum.

The alloy comprises Zinc 95% plus or minus 5% and Aluminum providing both fluidity and compatibility at an adequate low temperature.

And the heating of the molten bath preferably takes place within a range between 420 and 460 ° C, where the alloy has an excellent fluidity.

In this way, a maximum intimacy of ligament and penetration of the metal is obtained to block the male-female coupling joints in the desired way.

Equally advantageously, said evaporator unit is preheated before immersion in said molten metal bath, at a temperature at least 10-15 ° C above the bath temperature. In this way a maximum capillarity of penetration of the metal is ensured between said nozzle manifold sleeve and the return pipe.

Equally advantageously, in order to avoid the danger of hindering the amalgam of the molten metal with the internal surface of the nozzle manifold sleeve and the external surface of the said return pipe, the said molten metal is subjected to ultrasound, so that the ultrasonic vibrations favor the detachment of the oxide layer from the surfaces involved in the bath, allowing greater intimate contact.

Advantageously, the bath will take place in a vertical axial direction. In this way there is the advantage not only of wetting only the junction area which advantageously can be projecting, but it will also have the advantage of allowing the oxides in the junction space of the collector sleeve of the inlet of the return pipe, to detach by floating or be pushed towards the annular bottom above the abutment of the pipe in the manifold, also favoring a clogging of said gap and preventing the metal from passing inside the evaporator flow and return ducts.

Furthermore, the oxides which detach externally in the metal bath can be skimmed because they float periodically from said bath, thus being able to use the molten metal completely with minimum loss.

Since with the extraction of the evaporator unit from the bath, a drop of metal may occur which will cool on the surface leaving the drop, this can be avoided by means of a suitable jet of air.

Description of a preferred embodiment

These and other advantages will appear from the following description of a preferential embodiment solution with the help of the attached drawings, the details of which are not to be construed as limiting but only provided by way of example.

Figure 1 is a view of the preassembled evaporator assembly.

Figure 2 is an enlarged partial sectional view of the junction area within said inlet sleeve of the pipe of the refrigeration circuit with the evaporator.

Figure 3 is a schematic view of how the production plant of the evaporator unit can be mechanized, in the phase of fixing the refrigerant circuit piping to the evaporator plate, where it is shown that both couplings (piping-piping and evaporator piping) they are immersed in the bath and then simultaneously sealed, ie welded by the molten bath.

Figure 4 again schematically shows the junction area in an enlarged manner.

Figure 5 is a schematic sectional view of the coupling area in the refrigerant circuit piping at the branch with the capillary tube coming out.

Figure 6 represents a schematic sectional plan view of the graft of Fig.5.

Figure 7 represents a schematic cross-sectional plan view of the coupling of Fig. 5, in variant to the solution of Fig. they favor the penetration of the molten material (obviously said corrugations or grooves could alternatively be realized in the female part, ie outer sleeve).

Referring to the figures, it can be seen that 1 indicates the evaporator plate, which, as mentioned, is made by joining two shaped sheets to form a single set (roll bond) with the evaporation circuit V which branches from a nozzle manifold sleeve 12 with a delivery "A" and a return (R-1 "') after complete expansion in a large evaporation surface (1").

To the evaporator plate, the said pipe of the refrigeration circuit is inserted into said inlet manifold sleeve which comprises a return pipe 3 and a capillary tube 5 which is located inside the return pipe 3, and projects from it, to continue inside the delivery of the evaporator 1 ', where it is clamped by caulking 11 of the delivery duct which forms a watertight seal around the capillary tube by means of a sealing paste, which allows only the outlet in the delivery duct.

The return pipe 3 is completely inserted into said sleeve 12 where it engages in intimate contact, allowing the return pipe (R-1 "') to allow the outflow of the refrigerant fluid gas annularly outside the capillary pipe (5) and inside the return pipe 3.

At a certain distance in length of the return pipe 3 + capillary pipe 5, there is a welding node, generally socket (4), where the two pipes are separated (3) and (5) to be, upon assembly in the casing of the refrigerator, taken outside the cold room.

The evaporator plate is generally rectangular and is supplied to the refrigerator industry flat or slightly pre-folded to facilitate complete folding.

The pipe 3 + 5 welded to the evaporator is conveniently placed next to the evaporator plate and the free capillary is rolled up, as indicated by way of example in figures 1 and 3.

This is obviously done for technical reasons to reduce the overall dimensions, in order to facilitate handling and packing.

According to the invention, the preassembled evaporator units E (1 + 3 + 5) as shown in Fig.1 are hung on a continuous conveyor "C".

These evaporators are first made to pass through a preheating station (for example heating tunnel "T") where in any case the junction area 13 'is preheated which conveniently projects with respect to the lower edge of the evaporator plate 13.

The heating takes place at a temperature at least 10-15 ° higher than in the aluminum-zinc metal alloy bath (B).

After preheating, the conveyor (C) conveys the evaporator unit (E) directly in partial or total immersion within the molten metal bath (B).

the path continues and the evaporator comes out of the bathroom.

A jet of air not illustrated will remove the metal drops and promote rapid solidification.

At this point the evaporator unit is ready for shipment to the final assembly to form the refrigerator without further processing, or it will pass to a subsequent painting station.

Advantageously, as mentioned:

- during the dive the whole will be subjected to ultrasonic vibration.

In this way, the surface oxide will be thrown and will tend to float on the bath favoring the intimate attachment of the metal alloy both on the surface of the evaporator and on the surface of the pipeline concerned.

Periodically the slag floating on the bath (B) will be removed by skimming.

Since the sleeve joint will be arranged vertically downwards, the oxide stock will be pushed up by the pressure of the molten metal, and will accumulate annularly along the graft constriction (6) providing a natural plug against the danger of the metal melt oozes into the delivery and return ducts inside the evaporator.

In the figures (a junction area (13 ") has been created projecting with respect to the lower edge (13), nothing excludes, however, that said projection 13 'does not exist and that a part of the evaporator or even the entire evaporator with the aim of providing an additional protective coating (a much more expensive operation but which would provide an evaporator with greater resistance to corrosion and wear).

The junction area can also be moved to an edge of the evaporator and this in this case will be hung inclined diagonally, in which case no protuberances will be required and the immersion part can be minimal.

Obviously the piping can be made of aluminum and its alloys or copper and its alloys. In fact, the coating due to the metal bath entails a passivation of the joint subject to galvanic corrosion, which is particularly more dangerous when dealing with different metals (eg Aluminum with Copper).

The respective branch 4 can also be subjected to said bath, also providing the same sealing therein using the same technique as described above.

In this case, the immersion of Fig. 3 must provide that the portion of the branch (4) is also immersed, arranging the pipe alongside the evaporator plate in a different way, or even more immersing the entire evaporator unit.

Figure 7 illustrates a convenient variant of the coupling, shaping the return pipe (3 and 3 ') inside the sleeve (4). This promotes the penetration of the molten alloy.

The solution of figure 5 represents the connection of two return pipes 3 and 3 'with the exit of the capillary pipe 5, all encapsulated by the cup sleeve 4. In this case the return pipe 3 is in aluminum and its continuation 3 'is conveniently made of copper.

It is however understandable that only one return pipe 3 entirely in aluminum can be used, with a lateral hole for the capillary tube outlet (5), all encapsulated by the cup sleeve (4).

Alternatively, the sleeve 4 could also be eliminated and obtained from the shaping by widening the mouth of the return pipe from the evaporator (3) and inserting the return extension (3 ') into it, in which case the sleeve (4) would be part integral part of the first section of return pipe (3).

Advantageously, to facilitate the penetration of the molten metal into said collector sleeve, a lateral hole may be provided on said collector sleeve.

In this case, this vent will favor the penetration of the metal, since said vent may be of such a value that it automatically closes upon extraction from said bath by capillarity and subsequent solidification. Additional benefits

The use of ultrasonic technology for the assembly of the evaporator unit involves not only a reduction in the number of connection points, but also the possibility of avoiding the use of deoxidizing substances with the consequent guarantee on the internal cleaning of the circuit and with a general improvement of environmental operating conditions.

The design and the geometric preparation of the joint before setting up the implant will provide guarantees of repetition.

The realization of an interlocking system consisting of a numerically controlled roto-translator, allows to obtain an indirect control in process on the constancy of the characteristics.

Furthermore, the very typology of ultrasonic welding allows to determine the process parameters upstream and guarantee the repeatability of the result with their constancy, freeing it from the skill of the operator.

The geometry of the joint on the panel is predetermined with a tool capable of creating the appropriate seat to accommodate the exchanger tube and to prevent any blockage of the joint. The work phases:

• The first phase consists in inserting the end of the refrigerant circuit piping into the inlet manifold sleeve (whose seat will be pre-calibrated) of the evaporator plate, with the insertion of the first inside a pre-calibrated seat.

• The second phase involves preheating the panel-pipe assembly of the refrigeration circuit to a temperature of 10-15 ° C above the melting point of the solder.

• The third phase consists in immersing the preheated assembly in a bath of molten zinc and aluminum alloy.

• After a few seconds of adaptation of the tube exchanger-panel assembly inside the alloy, the action of the ultrasounds begins which subjects the whole together to molecular vibrations.

• The cavitation introduced by the ultrasonic excitation of the molten alloy removes the oxides from the submerged metal surfaces favoring the amalgamation of the molten alloy with the molten metal.

• The combination between the main pressure of the liquid alloy caused by the joining of the assembly that is immersed in the molten alloy and the ultrasonic vibration causes the alloy to penetrate and fill the cavities between the two parts to be joined, pushing the oxide towards the tall.

• Part of the oxides dissipate inside the molten alloy, and subsequently will float to the surface, where they can be easily removed.

<•> At the exit from the bath, a cleaning and control phase can be envisaged with possible removal of alloy residues and subsequent functional testing.

the refrigerant circuit piping can be sealed in the same phase or also in the preventive phase as regards the deviation node 4 with a similar technique.

Claims (9)

CLAIMS 1. Evaporator unit of the type which includes an evaporator plate in aluminum or its alloys, to which a metal pipe (3) of the refrigeration circuit (3,4,5) is inserted in a corresponding junction area (1 "), in a corresponding inlet manifold sleeve (12) of the evaporation circuit (1 ', 1 ", V") of said evaporator (1), characterized in that: - the external surface of at least said junction area is covered with a layer of molten metal made adherent by immersion; - The interspace of said graft (3-12) is sealed by penetrating the same molten metal that covers the surrounding external area. 2. Evaporator unit according to the preceding claim, characterized in that the said junction area projects (13 ') with respect to the edge (13) of the evaporator plate (1). 3. Evaporator unit according to the preceding claims characterized in that the said junction area (13 ') is arranged in an edge of the evaporator plate (1). 4. Evaporator unit according to the preceding claims, characterized in that it is entirely covered with a protective layer of molten metal made adherent by immersion (B). 5. Evaporator unit according to the preceding claims, characterized in that it comprises a second coupling (4) of said refrigerant circuit piping (3-3'-5), which, designed to make the respective capillary tube (5) come out from said return pipe (3), it is also sealed and coated by immersion in said bath of molten metal (B). 6. Evaporator unit according to the preceding claims, characterized by the fact that said refrigerant circuit piping (3-3'-4-5) provides for the use of a single metal material such as aluminum or aluminum alloy substantially of the same material as the evaporator. 7. Evaporator unit according to the preceding claims, characterized in that the sleeve (4) of said second coupling (3-3'-4-5), is eliminated and replaced by the respective sleeve enlargement of the respective return pipe from the evaporator (3). 8. Evaporator unit according to the preceding claims, characterized in that said couplings provide a shaping of the male or female part with grooves (N). 9. Evaporator unit according to the preceding claims, characterized by the fact that said refrigerant circuit piping (3'3'-4-5) provides for the use of a single integral return tube (3-3 '), without junctions , which uses a cup sleeve (4) which allows said capillary tube (5) to come out of said return tube, encapsulating it and filled with molten metal in said bath (B)