A TRANSPORTABLE EQUIPMENT FOR THE THERMAL TREATMENT OF METALS

Field of the invention

The present invention concerns the technical field relative to vacuum furnaces for the thermal treatment of metals.

In particular, the present invention refers to an innovative furnace of high efficiency and reduced dimensions, in such a way as to result both transportable and particularly suitable for the thermal treatment of a limited number of pieces.

Background Art

Equipments for the thermal treatment in vacuum of metals have long been known.

As per figure 1, these basically comprise a bell 1 (also called vacuum chamber) having a receiving chamber 2 (also called thermal treatment chamber) into which the piece or pieces to be treated is/are positioned. The receiving chamber 2 works in vacuum conditions, that is an internal depression is realized variable from 10ex-2 (ten raised to minus two) millibar up to values of ten raised to minus five millibar (10ex-5). The vacuum is essential in these processes since it avoids, the initiation of oxidation phenomena due to the presence of oxygen.

The thermal operations that are realized are multiple and can comprise, for example, hardening, brazing, tempering, ageing, annealing, stress relieving, solution heat-treatment or similar operations.

The bell 1, for obvious reasons of vacuum, therefore must be structurally dimensioned in an appropriate manner to avoid that the entire structure collapses on itself by means of the depression created.

Inside the bell a heating system is included to raise the temperature to the desired value as well as a cooling system. The heating system uses, for example, electrical resistances or burners. The cooling system is obtained through the injection of a gas into the receiving chamber 2. In such a manner, once the raising of temperature is realized to take the pieces to the pre- established temperature, the chamber is quickly cooled in such a way as to realize the desired thermal treatment.

Getting more into the detail of figure 1, a heat exchanger ' 3 is therefore highlighted arranged into the bell and that includes a coil 4 into which a cooling liquid circulates, generally water. A cooling gas, for example nitrogen, is injected into the chamber through a plurality of nozzles 6 or other openings and is sucked through an engine with fan 5 arranged behind the coil 4 itself in such a way that the gas sucked is forced to a passage through the coil and therefore in contact with the external surface of the coil itself. In such a manner, the cold gas in entry into the chamber 2 exchanges heat with the piece to be cooled (the hot piece yields heat to the gas) and, in turn, the gas heated by the contact with the piece yields heat to the coil during its sucking and is cooled again. Through a simple closed-cycle circulation the gas is therefore re-introduced in the chamber 2 through the said openings 6 once cooled, realizing a closed cooling circulation that continues for the necessary time up to the completion of the thermal treatment.

The background art presents a technical inconvenience due to the ^' fact that. the current configurations are such as to include an exchanger 3 integrated into the bell 1. This renders the dimensions of the bell very big and, contextually, it makes that the reduction of dimensions of it results very difficult. If, with such a configuration, an. excessive reduction of encumbrances should be tried, the cooling system would result inefficient and hardly realizable. In that sense, in the background art, such . equipments are of big dimensions to the point that they include chambers suitable for working not less that one hundred kilos of material.

It is therefore evident that, in accordance with the background art, the elaboration of few kilos of weight, for example just for experimental uses, is not economical. Moreover, such equipments are not transportable, but fixed in a permanent manner.

Disclosure of invention

It is therefore the aim of the present invention to provide an equipment for the thermal treatment of metals that solves at least in part the above mentioned inconveniences.

In particular, it is the aim of the present invention to realize an equipment for the thermal treatment of metals of reduced dimensions, accessorized with the main instrumentation, in such a way as to result easily transportable and therefore mobile from one place to the other .

It is therefore the aim of the present invention to provide an equipment that results structurally simple and that does not require long times of installation and test of functioning.

These and other aims are therefore obtained with the present equipment for the thermal treatment of metals in accordance with claim 1.

The equipment, as known, includes a bell (10) provided with a receiving cavity (20) into which one or more than one metal pieces to be thermally treated can be positioned and heating means to raise the internal temperature of the receiving cavity (20) at a pre-established value.

The equipment includes ah assembly of thermal exchange (100; 200; 300) to lower the temperature reached in the receiving cavity (20) in such a way as to operate the per- established thermal treatment on the pieces. Such assembly of thermal exchange (100; 200; 300), in accordance with the invention, is now arranged externally to the bell (10) in such a way as to allow a reduction of its dimensions.

In such a manner, it is therefore possible to realize bells of very reduced volume that allow a thermal treatment also on a limited number of pieces, without for this incurring excessive costs.

Moreover, realizing such an assembly externally to the bell allows, on one hand, to be able to realize anyway an efficient cooling system without for this reason having to increase the dimensions of the bell itself and, on the other hand, to be able to easily realize a transportable equipment .

Advantageously, the assembly of thermal exchange (100; 200; 300) forms a closed circulation path for a cooling fluid injected · in the receiving chamber. The closed circulation path comprises a thermal exchanger (30, 60; 230, 260', 260"; 330, 360', 360" ) _. directly integrated along the closed circulation path and into which the cooling fluid circulates directly. In such a manner, when the cooling fluid is injected into the cavity it circulates along the closed circulation from the receiving cavity (20) to the thermal exchanger to lower its temperature, to be then thrust again into the bell (10) in such a way as to be able to operate the lowering of temperature on the pieces internally arranged. Such a closed circulation system of the cooling fluid has the advantage of avoiding the integration of a specific coil into which a second cooling fluid is circulating that, in turn, cools the hot gas that has operated the lowering of temperature of the treated pieces.

Advantageously, the closed circulation path further includes an impeller (50) to force the circulation of the cooling fluid along the said closed circulation.

Advantageously, the closed circulation path is formed by a feed pipe (40') connected to the receiving cavity and through which the cooling fluid injected in the receiving cavity is sucked, by a return pipe (40'') through which the cooling fluid circulated into the receiving cavity is injected again, and by the thermal exchanger (30, 60; 230, 260', 260''; 330, 360', 360") with, the impeller (50) interposed between the feed pipe and the return pipe.

Advantageously, in a first possible solution the thermal exchanger (30, 60) can comprise a coil pipe (30) connected by an end to the feed pipe (40') and by the opposite end to the impeller (50) and a forced aeration system ( 60 ) , arranged with respect to the coil (30) in such a way as to be able to throw a cooling air flow against the coil, thus operating the lowering of the cooling fluid circulating inside the pipe that forms the coil.

Advantageously, the coil can be closed by a containment box (35) hermetically closed on one side through a guide channel (61), to guide the cooling air from the forced aeration system (60) against the coil, and open on the opposite side to allow the exit of the cooling air.

Advantageously, the thermal exchanger (230, 260', 260' ' ) , in a second version of the invention, can comprise an air/water plate exchanger (230) having a delivery (260' ) to inject a cooling, liquid and an exit (260' ') through which the heated liquid is expelled.

Advantageously, the plate exchanger (230) is connected on the opposite side to the delivery (40') and to the return (40'') in such a way that the circulating gas can exchange heat into the exchanger (230) through the injected cooling liquid.

Advantageously, in that case, a further cooling system can be included dimensioned to lower the temperature of the cooling liquid in exit from the plate exchanger.

Advantageously, the cooling liquid of the plate exchanger is a closed circulation one as well.

Advantageously, in that case, the cooling liquid of the plate exchanger can intercept also the bell to cool it externally.

In a third solution, the thermal exchanger (330, 360', 360'') can advantageously comprise an air/water exchanger (330) having a delivery (360') to inject a cooling liquid and an exit (360'') through which the heated liquid is expelled and wherein the said exchanger includes liquid/gas circulation finned pipes to improve the thermal exchange.

Also in this case the cooling liquid, for example water, can be made to circulate in a closed manner without requiring the connection to an external source. In that case, as already said for the second configuration, it will therefore have to be integrated to an auxiliary cooling system in such a way as to lower its temperature for the re-circulation and eventually such a liquid will also be able to be used to lower the external temperature of the bell.

Brief description of drawings

Further characteristics and advantages of the present equipment for the thermal treatment of metals, according to the invention, will result clearer with the description of some embodiments that follows, made to illustrate but not to limit, with reference to the annexed drawings, wherein:

- Figure 1 shows a thermal bell in accordance with the background art;

- Figure 2 shows an equipment in accordance with the present invention;

- Figure 3 shows a further view of the equipment of figure 2 to better highlight the pump for the vacuum;

- Figure 4 shows a scheme of functioning with reference to the first constructive solution;

- Figure 5 shows a second possible embodiment;

- Figure 6 shows a third possible embodiment.

Description of some preferred embodiments

With reference to figure 2, an equipment is described in accordance with the present invention. A support structure 11 supports a bell 10, generally cylindrical. The bell is placed horizontally, that is with its central symmetry axis arranged in parallel to the ground. However, nothing would impede the vertical arrangement of it.

Always as shown in figure 2, the bell 10 includes inside it a receiving cavity 20 delimited by lateral walls 21 appropriately dimensioned in the thickness and in the pre-chosen materials in such a way as to be able to resist to the depression values and to the temperatures necessary to operate such thermal treatments on the metals. The receiving cavity 20 includes inside it a sort of piece- bearing grating 22 on which the pieces to be thermally treated are arranged.

A system of mobile baffles 23, for example controlled pneumatically, appropriately seal the receiving cavity, isolating it from the external environment during the operations of treatment. Such baffles are auxiliary to the maintenance of the internal temperature of the chamber. The bell generally includes an opening similar to a hinged door, that is a hatch, to have access to the receiving cavity and naturally closable hermetically. The hermetic closure guarantees the maintenance of the vacuum conditions into the chamber.

The vacuum, as well known in the background art, _. is realized through a pump 80 visible in figure 2 and better highlighted in figure 3. The pump is connected to the internal cavity through a pipe 71 better highlighted in figure 3.

An assembly of thermal exchange (40', 30, 50, 60, 40'') serves to operate the cooling of the gas injected into the receiving chamber and, in accordance with the invention, is a closed circulation one and is arranged externally to the bell in such a way as to be able to reduce the overall dimensions of the latter.

Without modifying the above, a first possible embodiment of the invention is precisely represented by the following figures 2, 3 and 4 and they describe in detail, the configuration of the said assembly of thermal exchange.

Figure 2 and figure 3 show the internal cavity provided with a first entry 41 and a second entry 42 arranged in two different points of the chamber (preferably on two opposite parts of the grating 22).

The closed circulation formed by such an assembly of ^• thermal exchange includes a delivery 40' connected to the entry 42, and a return 40'' connected to the entry 41. The delivery and the return then intercept a cooling block (30, 50, . 60) that operates the cooling, as better described below.

The cooling block includes a coil 30, that is a pipe in the shape of a coil to realize a thermal exchanger. The coil includes an entry 31 that is connected to the delivery 40' and an exit 32 connected to a sucking impeller 50. The opposite part of the impeller 50 is then connected to the .return 40'' (as better highlighted in figure 3) in such a way as to realize the said closed circulation of the cooling fluid forced into the cavity 20 from the delivery 40' to the return 40''.

Going back to figure 2, a forced aeration system 60 includes a sucker 60 which, through a sucking engine, sucks air from the external environment to pipe it through a channel 61 directly on the pipe forming a coil 30. The coil 30, to improve the thermal exchange, is arranged into a containment box 35 to which the channel guide 61 of the forced air sucked by the aerator 60 is connected hermetically. The box 35 is therefore open on the opposite side to the connection with the channel 61 to allow the exit of the air flow.

Always as shown in figure 2, the bell 10 includes one or more than one entries 15 through which a cooling gas is injected into the cavity.

The entire assembly of thermal exchange forming the closed circulation described is arranged externally to the thermal bell 10 and placed on the support structure 11 which is mobile, for example, through wheels.

With reference to the schematization of figure 4, having described structurally all the basic elements of such a first possible embodiment, we can pass onto a description of its functioning.

Once the piece is taken to temperature, in order to operate the cooling, the injection of a cooling gas is realized through the entries 15 placed in the bell 10 and here marked with a dotted line just for descriptive simplicity purposes. The gas injected in the receiving chamber impacts with the material arranged into the chamber absorbing the heat of it. Contextually, the impeller 50 is activated by which the cooling gas injected in the receiving cavity is forced to circulate in a closed-cycle manner along the closed circulation (40', 30, 50, 40'') to go back to the receiving chamber. .

In particular, the cooling gas passes from the delivery 40' to be inserted into the pipe forming the coil 30 (see direction of the arrows in figure 4). The gas therefore circulates into the pipe of the coil and not externally to it as per the background art. In exit from the pipe forming the coil the gas goes up, thanks to the thrust of the impeller 50, towards the return 40'', where it will reach the receiving chamber cooled to start the circulation again.

The cooling takes place during the passage in coil thanks to the forced aeration system 60 which sucks the air from the external environment (see direction of the arrows applied to the grating of the aerator 60) and pipes it into the box 35 against the external surface of the coil heated by the circulating internal gas, therefore by actually realizing an air/water thermal exchanger. The air in exit from the box 35 is therefore hot air because it has absorbed the heat of the gas circulating into the pipe of the coil .

Further advantages of such a solution are therefore evident. In particular, it is not necessary anymore, as per the background art, a further water exchanger 3 inserted into the bell and that is hit by the cooling gas of the metal to lower its temperature. The gas that cools the metal is now directly circulating in the coil and cooled by a simple aeration system. The whole therefore results in a very simplified structure.

In a second possible configuration of the invention shown in figure 5, without modifying what has been described up to now, the cooling block includes an air/water plate exchanger 230. In particular, a cooling liquid (for example water) is fed by a delivery 260' which intercepts the plate exchanger to exit hot from an exit pipe 260''. The closed circulation is also in this case, as per the first configuration, formed in succession by the delivery 40', by the cooling block 230 into which the cooling gas circulates, by the impeller 50 and by the return 40' ' . In use, therefore though remaining unvaried what has been already described, the system of functioning ^' of the cooling block changes since in this case a liquid is injected into the plate exchanger 230 instead of being sent an air flow. The liquid circulating in the exchanger 230 is sucked through the exit 260'' from which it exits hot since it has absorbed the heat of the hot fluid circulating in the closed circulation (40', 230, 50, 30''). Such a solution, diversifying itself from the previous one in the use of water instead of air, is capable of discharging greater quantities of heat. Such a configuration can include the integration of a small auxiliary cooling system in such a way as to cool the water to be put in circulation again. It is not therefore in this way necessary to connect the system to an external water source but, instead, the same water can always be re-circulated and used also for cooling the bell externally.

In a third configuration of the invention, an air/water exchanger 330 is included which is identical to the previous one 230 except for the fact that a version of the exchange pipes of the finned-pipe type is included for improving the thermal exchange.

An ordinary control console allows to control the entire equipment, while an electrical connection to an external outlet allows to feed it electrically.