CH622729A5 - Press for induction brazing metal workpieces including raised or curved peripheral portions - Google Patents

Description

The present invention relates to a brazing press two or more metal coats together to obtain a laminated metal structure and, more particularly, a press for brazing on a first part comprising on the one hand, a flat central part and, d on the other hand, a curved or raised peripheral part, a second part covering this central part and partially the peripheral part.

Such brazing presses are generally used in the manufacture of cooking vessels, where it is advantageous to combine with a deep-drawn stainless steel, for example, and comprising a flat bottom and raised and curved skirts, a part called a diffuser bottom. heat to a metal that is a good thermal conductor, such as copper, aluminum or their alloys.

In French patent N ° 2087328, a brazing press has been described making it possible to join a stamped with raised edges, a preformed diffusing coating whose opposite face of the stamped also has raised edges of shape adapted to that of the 'stamped. This brazing is carried out here using a single intermediate heating part made of ferromagnetic material, called "susceptor", which is of particular shape, that is to say that it comprises a thin central part, slightly concave and raised edges of significant thickness, the opposite face of the diffuser base adapts to the final external shape that it must take after it is brazed on the stamped. The pressure exerted by the press on the edges of the susceptor makes them slightly pivot, thanks to its concavity, with respect to its center and, consequently, strongly presses the raised edges of the diffusing base against the corresponding parts of the stamp.

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To perform brazing of these curved peripheral parts, the press described in the aforementioned patent further comprises an additional inductor surrounding the edges of this susceptor.

Experience has shown that after a certain number of pressing and heating operations, the susceptor thus arranged loses the concavity of its central part and it is necessary to remove the susceptor from the press and to put it back into correct shape. applying, for example, pressure on its center, which means the interruption of production for the time necessary to replace the susceptor with another in good condition.

We have also described, in French patent No. 2105660, a press for stamping a flat coating plate placed on a stamped flat bottom with raised edges so that this plate covers the bottom as well as the edges, and to braze them together then. Such a press comprises a mandrel carrying the pressed part, two coaxial jacks, the first of which carries on its lower end a rigid block including the main inductor and the flat central part of the ferromagnetic susceptor. The first cylinder being actuated first, it presses the flat coating plate against the flat bottom of the stamping. The second cylinder carries on its lower end a rigid cylindrical jacket or box surrounding the inductor block. This jacket carries on its lower end the annular peripheral part of the susceptor, distinct from its central part, and intended, on the one hand, to conform by stamping the periphery of the diffuser coating plate to the raised edges of the stamping and, d on the other hand, using an additional inductor surrounding this peripheral part from the outside, to join them by brazing.

Furthermore, in French patent No. 2153620, a brazing press has also been described for joining a preformed diffuser coating to a stamped part to cover the flat bottom and the raised edges thereof where, to obtain intimate contact between the raised edges of the stamp and the periphery of the diffuser coating, additional pressure is exerted from below on the edges of the skirt of the stamp so as to slightly deform it. This is obtained here, either using elastic means such as springs, or using a double-acting press (with two cylinders). The additional pressure exerted on the skirt must be carefully dosed at the limit of elasticity because it is necessary to avoid, on the one hand, the permanent deformation of the stamping and, on the other hand, the insufficiency or the total absence deformation due, for example, to the weakening of the springs, the stamping being generally very rigid. This increases the cost of installation.

The object of the present invention is to create a brazing press which makes it possible to avoid the risk of permanent or insufficient deformation by exerting additional pressure, not on the skirt, but on the curved edges of the coating, without requiring the use a double-acting press as in the second cited patent of the holder.

To this end, the subject of the invention is a brazing press for joining a stamping device comprising a planar circular bottom, a symmetrical skirt around an axis and curved parts connecting the bottom to the skirt, to a previously formed part, called diffuser coating, having to cover said bottom and at least partially said curved parts of the stamp, said press comprising a fixed support frame, a single jack fixed to the frame, a mandrel supporting the stamp and carried by the movable rod of the jack, a block containing a main inductor coupled to the frame and located above and facing the mandrel, intermediate heating means made of a ferromagnetic metal comprising two separate parts, constituted by a flat central part inserted between said coating and said inductor block which door, and a peripheral part of annular shape whose inner face has a shape adapted to that of the outer face of the peripheral parts of the diffuser coating covering the curved parts of the stamped part, an additional inductor surrounding the peripheral part of the intermediate means, in order to heat it, and a cylindrical sleeve made, at least in part, of a non-deformable insulating material coaxially surrounding the main inductor block and coupled to its end opposite the mandrel to said annular peripheral part as well as to the additional inductor surrounding it and, at its other end, to the press frame, said press being characterized in that one of the central parts and peripheral of the intermediate heating means or the block or sleeve which carry them, are coupled to the press frame using elastic coupling means, calibrated and guided using guide means so as to be able to perform a limited axial displacement relative to the other part which is fixed to the frame, so that, when said single cylinder pushes the mandrel towards the block, pressures respectively exerted es on the respective central and peripheral portions of the bottom of the pressed and the coating are independent of one another.

The invention will be better understood and the characteristics and advantages will appear with the aid of the description below, given by way of example, and of the appended drawings relating thereto, in which:

- fig. 1 shows a section in elevation of a part of a first embodiment of a brazing press according to the invention;

- fig. 2 shows a section in partial elevation of a first embodiment of a second embodiment of such a brazing press;

- fig. 3 illustrates in section a second embodiment of this second embodiment, and

- fig. 4 shows a partial axial section in elevation of a part of the preferred embodiment of a brazing press according to the second embodiment of the invention.

Fig. 1 is a partial section, axial in elevation of the first embodiment of the invention.

In fig. 1, there is shown at 1 the main inductor of the brazing press enabling two plates to be brought together, the first of which is formed by the bottom of a stamped piece 2 of stainless steel, for example, and the second of which is a plate a metal which is a good heat conductor which must constitute a thermal diffuser coating 3 which will, for example, be made of aluminum or an alloy of this metal. In the interface between the two elements which must be joined by brazing, a brazing contribution is deposited generally comprising a flux and a metal alloy generally having a melting point slightly lower (from 30 to 40 ° C) than that of the two metals with a lower melting point (i.e. aluminum or its alloy).

Stamped part 2 is supported by a mandrel composed of two parts, the first 4 of which, joined to the rod 14 of the jack mounted on the press frame, is made of metal, and the second of which 5 which comes into contact with the bottom of the stamp 2 to receive the diffusing coating 3 provided by brazing, is in a thermal insulator, that is to say in a poor heat conductive material, such as an asbestos-cement compound. The second part 5 of the mandrel is supported by the first 4 and its upper end conforms to the shape of the interior of the bottom of the pressed part 2.

The diffuser coating 3 is preformed, that is to say its face facing the stamped 2 is adapted to the shape of the latter. The main inductor 1 is coated with a plastic material or with a cement-based refractory compound, forming a rigid block 6 which is carried by a metal plate 7 secured to an arm of the press frame, produced in a known manner ( not shown), so as to be arranged facing the mandrel and coaxially with it. The inductor block 6 can be protected against heating (when it is not refractory) by a cold screen and by an asbestos-cement thermal insulation plate (not shown) which are inserted, according to the prior art, between the underside of block 6 and an intermediate heating element made of a ferromagnetic material, called susceptor in the aforementioned patents of the holder.

The dimensions of the main inductor 1 correspond

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substantially to those of the flat part of the bottom of the stamped 2 and it approximately covers it.

The main inductor 1 is of the conventional type used, generally, to heat a flat surface as uniformly as possible, such as a flat spiral (called “pancake” in the English-speaking literature) with uniform or non-uniform pitch, or a spiral conical or frustoconical. It is also possible to advantageously use an inductor derived from the flat spiral, as described in French patent N ° 2087071, comprising a plurality of concentric turns, connected in series and located respectively at different distances from the heating susceptor so to obtain a substantially uniform temperature distribution in the interface between the bottom of the pressed 2 and the diffusing coating 3. Because the diffusing coating 3 has raised edges which must also be brazed at the pressed 2, the press comprises here two separate intermediate heating components, one of which 100 is planar and constitutes the central part of the susceptor situated below the main inductor 1 and the other of which Ì0Ì. is annular and constitutes the peripheral part of the surrounding susceptor, d on the one hand, the central part 100 and, on the other hand, the curved periphery of the diffuser coating 3, as described in the aforementioned second and third patents of the licensee.

More specifically, the central part 100 of the susceptor here consists of a flat plate at least approximately the dimensions of the flat part of the bottom of the stamp 2 and, consequently, those of the inductor block 6. The underside of this plate is intended to come into direct contact with the upper face of the flat central part of the diffuser coating 3 and to be heated by the main inductor 1.

The peripheral part 101 of the susceptor, of annular shape, here comprises a curved or inclined lower face so as to match the shape of the outer face of the raised edges of the diffusing covering 3, a planar upper face and a substantially cylindrical outer lateral face (or possibly frusto-conical). The two parts of the susceptor 100,101 are made in. substantially non-deformable and slightly magnetic steel.

The main inductor 1, as in the first three French patents mentioned above, being only provided for brazing the flat part of the diffuser coating 3 with the stamped part 2, it is necessary to provide an additional inductor 110 to ensure the heating of the peripheral annular part 101 of the susceptor and, by this, the brazing of the raised edges of the diffuser coating 3 to the curved part of the stamped part 2, which connects the bottom to the skirt thereof. This additional inductor 110, of substantially helical shape (solenoid) is produced, for example, using a cylindrical or rectangular tube, made of copper for example, traversed by a cooling fluid and it is maintained using of parts 12, for example molded, of an insulating material, preferably refractory, which allow its attachment to an element integral with this peripheral part 101 by means of screws 13. The additional inductor 110 must be placed around and near the external lateral face of the peripheral part 101 of the susceptor so as to ensure a tight coupling with the latter, surrounding it. The number of turns and the shape of this additional inductor 110 as well as the intensity of the high-frequency current which flows through it, are determined so as to obtain a uniform distribution of temperature throughout the interface between the diffusing coating 3 and the stamped 2. This is possible either experimentally, that is to say by brazing a few samples and then dismantling them for examination, or using a temperature reading in this interface by means of thermocouplers, depending on the process described in the aforementioned fourth patent of the holder.

The stamp 2, shown in FIG. 1, includes a flat central part which constitutes its bottom and a frustoconical skirt connected to the bottom by curved parts which, like the bottom, must be joined by brazing to the diffusing coating 3. To replace the pressure exerted on the edges of the diffuser coating 3 by the pivoting of the edges of the single susceptor described in the first aforementioned patent of the holder which would allow it to be pressed against the corresponding parts of the stamping, we act here, in accordance with the invention, on the periphery of the coating s diffuser 3 by an auxiliary pressure exerted on the raised edges thereof, by means of the annular part 101 of the susceptor. This auxiliary pressure must be independent of; that acting on the bottom of the stamped 2 and on the flat part of the ^ coating 3 diffuser, in order to act on the periphery thereof io while it is softened by heating.

To this end, the annular, peripheral part 101 of the susceptor is mounted integrally on the lower end of a cylindrical and hollow sleeve (or jacket) 15, made of an insulating and non-deformable material, surrounding the inductor block 6 and which is mounted by its upper end on the support plate 7 thereof using elastic compressible means, such as compensating springs 16, which compression there by the upward movement of the jack and the mandrel 4,5 provides the desired auxiliary pressure. The sleeve 15 can be made of ceramic or, more economically, using fibers impregnated with resin, such as bakelized wood fibers or asbestos fibers embedded in a silicone resin.

It will be noted here that these elastic means can be constituted by several helical springs in the shape of a "rod" 25 calibrated, arranged symmetrically with respect to the axis of the inductor block 6, on a circle surrounding the latter and joined by their. respective ends to the support plate 7 and to the sleeve 15.

The total height of the sleeve 15 with the annular part 101 of the susceptor attached to it is chosen so that, when the springs 16 are completely compressed, the inner periphery of the underside of this annular part 101 is located above the underside of the central plate 100 of the susceptor. In this way, an auxiliary pressure is obtained exerted on the curved or raised periphery of the diffuser coating 3 inde-35 hanging from that which is exerted on its flat central part, due to the compression force of the springs 16 which are calibrated.

Due to its elastic suspension, the sleeve 15 is displaceable and, in order to obtain its correct operation in combination with the assembly of the press, the movements of the sleeve 15 40 must be limited, using guide means, to directions parallel to its axis, that is, from bottom to top and from top to bottom.

These guide means can be obtained, for example, by adjusting the internal dimensions of the sleeve 15 to the external dimensions of the inductor block 45 and making the adjoining surfaces slippery relative to one another. Another way to produce these guide means can be the use of several vertical rods, rigidly mounted in the fixed support plate 7, integral with the press frame, these rods penetrating so into adjusted vertical holes, made in the sleeve 15 or in an integral part thereof. These rods and holes cooperate together and must be arranged symmetrically with respect to the axis of the sleeve 15.

It is possible to advantageously combine the guiding means with the elastic suspension means as illustrated in FIG. 1.

Such a combined assembly comprises rigid guide and retaining rods 17, provided with threads (no screws) on their two ends, one of which is screwed into tapped holes in 60 the fixed support plate 7 so that the rods 17 are oriented vertically and arranged around the block 6, symmetrically to the axis thereof. The wall of the sleeve 15 has holes 18 starting from its upper end, located and adjusted so as to allow the insertion of all the rods 17 and of sufficient length to ensure correct guiding in the vertical direction. The lower end of the holes 18 opens onto cells 19 of sufficient size to allow, on the one hand, the screwing of a retaining nut 21 on the tapping of the lower end

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and, on the other hand, the entire vertical stroke of the sleeve 15 under the action of the jack pushing the rod 14. It is these retaining nuts 21 which determine the low position of the sleeve 15 and, by that, that of the annular part 101 of the susceptor.

The springs 16, which could be coil springs, are threaded on the rods 17 before their insertion into the holes 18 of the sleeve 15 so as to be arranged between the plate 7 and the upper end of the latter.

Experience has shown that it is very advantageous to use springs 16 each composed of a stack of elastic elements or elementary springs 22, each of which may be constituted by an elastic washer of frustoconical shape (commercially called washers " Belleville ”), because their use makes it possible to vary the elasticity and the rigidity of the assembled spring 16 by changing the orientation and / or the number of elements 22 stacked. In fig. 1, these elements 22 have been stacked head to tail (in the opposite direction) in an alternating fashion, which gives maximum elasticity and minimum rigidity. They can also be stacked in parallel or one can combine or alternate the two ways of assembly to obtain the desired parameters.

It will be noted here that it is also possible and perfectly equivalent to place the springs 16 between the lower end of the sleeve 15, which is then inverted and fixed to the support plate 7 and the annular part 101 of the susceptor which then carries the one of the ends of the rods 17, for example.

The operation of the brazing press in fig. 1 is as follows:

- When the press cylinder is actuated, it drives the rod 14 carrying the mandrel 4, 5 and the stack of the elements to be brazed 2, 3 upwards;

- The springs 16 being relaxed, the peripheral part 101 of the susceptor is located clearly below the central part 100 of the latter and between the first in contact with the curved periphery of the aluminum diffuser coating 3;

- Following the upward movement of the jack causes the springs 16 to be compressed until the flat central part of the covering abuts on the central plate 100 of the susceptor, fixed to block 6, the pressure force then exerted on an article of about 200 millimeters in diameter can be of the order of 4 tonnes;

- the auxiliary pressure on the periphery of the covering 3 is then exerted, independently of that compressing its central part, by means of compensating springs 16 suitably calibrated and can reach several hundred kilograms, which is sufficient to intimately apply the periphery of the coating 3 at the adjacent parts of the stamped part 2, when the aluminum reaches a temperature of approximately 580 ° C. and becomes easily deformable after the generator running supplying the main inductors 1 and additional 110.

The stamp 2 which is shown in FIG. 1 has a frustoconical skirt (a frying pan), therefore there is no problem in separating the periphery of the diffuser coating 3 from the annular part 101 of the susceptor immediately after brazing. However, this is not the case when the skirt is cylindrical (a pan) and when the coating must cover the beginning of it. Indeed in this case, due to the higher coefficient of expansion of the aluminum and the weakness of the caloric evacuation of the upper part 5 of the mandrel, the annular part 101 of the susceptor securely encircles the periphery of the coating 3 after its brazing on the stamping and does not release it until the stamping is sufficiently cooled. This means that, after brazing, the mandrel 4, 5 is withdrawn downwards, the stamp remains attached to the peripheral part 101 of the susceptor and this slows down the production rate. It would be possible to blow fresh air into the deep drawn from below from the mandrel 4, 5 or from above on the coating 3 through a cylindrical space between the inductor block 6 and the sleeve 15, formed for this purpose, in order to accelerate the cooling, but the time saving thus obtained is insufficient.

A second embodiment of the press in accordance with the invention has therefore been envisaged in which pressure is exerted on the periphery of the parts to be brazed independently of that exerted on their central part and, during the withdrawal of the mandrel after brazing, a thrust is exerted on this central part in order to push the stamped towards the mandrel, despite the strapping of the stamped provided with the coating by the annular part of the susceptor.

Fig. 2 is a partial sectional elevation of this second embodiment of the brazing press according to the invention.

In fig. 2, the mandrel 4, 5 follows the internal shape of the stamped 20 with a cylindrical skirt (pan), the inductor block 6 and the flat plate 100, joined to the bottom of this block 6, only cover the respective flat parts of the bottom of the stamped 20 and of the diffuser coating 3, the curved periphery of which reaches the beginning of the cylindrical skirt of the stamped 20 and is therefore liable to remain retained after brazing by the annular part 101 of the susceptor.

To avoid this drawback, a solution derived from that adopted in French patent No. 2087328 cited above is used here, where the mobility of the inductor block is recommended with respect to the fixed sleeve which surrounds it and which presses on the periphery of the susceptor in order to fold the periphery of the covering 3 by means of the raised periphery of the susceptor produced in one piece. This mobility was obtained in this prior patent using a spring pressing against the upper face of the inductor block.

In the second embodiment of the invention, illustrated in FIG. 2, the sleeve 150 is fixed, by its upper end, to the support plate 7 (by screws, for example) and it carries on its lower end, the peripheral annular part 101 of the susceptor as well as the additional inductor 110 intended to heat it by induction. The inductor block 6 is mounted on the same support plate 7 using elastic means, so that it can move parallel to its axis of symmetry, so that the pressure exerted on the respective flat central parts of the two parts to be brazed 20, 3 either independently of the auxiliary pressure exerted on the raised or curved periphery.

The elastic means here consist of a set of helical springs in the form of a "flange" 160, arranged symmetrically with respect to the axis of the inductor block 6, between the lower face of the support plate 7 and the upper face of the block 6 .

There are also provided means for guiding the axial movement of the inductor block by means of rigid guide and retaining rods 170 at the two tapped ends, one of which is screwed into the inductor block 6 and the other of which penetrates through guide holes 180 adjusted in cells or bowls 190 formed in the support plate 7 where they are provided with stop screws 210 defining the lower position of the inductor block 6, when the mandrel 4, 5 is distant from it. The springs 160 are threaded on the rods 170; they can be replaced by frustoconical washers of the "Belleville" type used in the first embodiment of FIG. 1 or by any other known type of spring.

The operation of the press according to the second embodiment of the invention is as follows:

- When the jack is actuated, the mandrel 4, 5 carrying the stamped 20 and the coating 3 begins its upward movement;

- during this upward movement, the flat upper face of the diffuser coating 3 first comes into contact with the lower face of the central part 100 of the susceptor, the low position of which, determined by the stop screws 210, is located below the underside of the adjacent periphery of the annular part 101 of this susceptor;

- In the following upward movement, the springs 160 are compressed and provide the pressure exerted on the flat central parts of the two elements 20, 3 which are to be brazed;

- Then, the mandrel 4, 5 comes into abutment on the annular part 101 which is fixed, by means of the curved periphery of the

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bottom of the deep-drawn 20 and the periphery of the diffuser coating 3; when, after starting the high-frequency generator (not shown) connected to the additional winding 110, the periphery of the covering 3 has reached a temperature around 580 ° C., the pressure exerted by the jack on this periphery la deforms so as to press it intimately on the adjacent parts of the stamped part 20 during brazing, and

- When, after the heating has stopped, the mandrel 4, 5 begins its downward movement, the pressure exerted by the springs 160 on the flat central part of the covering makes it possible to push the stamped part 20 down and to release it from its strapping in the substantially vertical surfaces of the annular part 101 of the susceptor, without waiting for it to cool.

The two embodiments of the invention described above are equivalent, because they both make it possible to obtain, using a single jack press, two pressures independent of each other and acting one on the flat central part and the other on the curved edges of all the elements to be brazed 2 (20) and 3.

Fig. 3 shows a partial axial section in elevation of another embodiment of the second embodiment illustrated by FIG. 2, with the jaws (block 6, mandrel 4, 5) of the press apart.

In fig. 3, the elastic connecting means 161 between the inductor block 6 and the support plate 7 consist of a single assembly of frustoconical washers 22 ("Belleville"), where they are stacked by two washers in the place followed by two washers upside down to compose a set calibrated as needed. The single assembly 161 is arranged coaxially with the inductor block 6 while being threaded on the guide means which consist of a hollow sleeve 181 screwed by its upper end into a tapped hole 182, formed in the bottom of a bowl 191 of the support plate 7 and by a guide and retaining rod 171 arranged in the axis of the block 6 and fixed to the upper end thereof. The rod 171 is inserted into the hollow 183 of the sleeve 181 in an adjusted fashion and its upper end is tapped so as to carry the retaining nut 211 determining the low position of the block 6 and, consequently, the length of its stroke. In addition, the assembled spring 161 is bordered at the bottom by a first ring 163 made of insulating material and at the top by a second ring 162 surrounding the sleeve 181.

The sleeve fixed at the top to the support plate 7, surrounding the inductor block 6 and carrying at the bottom the peripheral, annular part of the susceptor 101, is produced here in two integral parts, the upper 151 of which is made of non-refractory insulating material (wood Bakelized, for example) and the lower part 152 of which adjoins the annular part 101 of the susceptor, is made of a refractory insulating material, such as asbestos fibers molded in a silicone-based resin (marketed in France under the name "SYNDANIO"). The lower part 152 of the sleeve has a flange 153 which surrounds it and which is intended to carry the additional inductor by means of screws 130 and nuts 131.

This additional inductor is constituted here by a single turn in the form of a solid conductive ring 111 and open, surrounding at a short distance the side wall of the peripheral part 101 of the susceptor. This ring 111 carries, attached to it by brazing, a tube 112 of the same material (copper) traversed by a cooling fluid.

The main advantage of the embodiment of FIG. 3 is the ease of the respective adjustments of the stroke of the inductor block 6 by a single screw 211 and of the auxiliary pressure by the arrangement of the washers 22 of a single spring 161.

It is also possible to improve the operation of a brazing press by making the temperature distribution between the bottom of the stamp (2 or 20) and the diffusing coating (3) more uniform during their brazing.

One of the possibilities of such an improvement has been described in the French patent No. 1425005 or the corresponding British patent No. 1064903 where it has been proposed to use, in a brazing press to join together by brazing two or more flat circular plates of different diameters, a flat spiral inductor (called "pancake coil" in Anglo-Saxon literature) of large diameter and a set of monospire short-circuit windings of different diameters, interchangeable and one of which is arranged around the plates to be brazed, in the same plane and coaxially with the latter, so as to form a screen by covering the turns of the inductor which exceed the dimensions of these plates and thereby to standardize the distribution of the temperatures generated by the alternating magnetic flux which crosses them.

Experience has shown that the annular peripheral part of the susceptor partly plays the role of the short-circuited ring with respect to the main inductor, but since it exhibits a significant resistance to the induced current when hot and the fact that 'it is arranged below the main inductor, the effect of temperature equalization on the edges is insufficient.

Fig. 4 illustrates in partial section in elevation the preferred embodiment of the second embodiment of the invention which improves the uniformity of temperatures on the periphery of the plates to be brazed by using a metal support piece of cylindrical shape surrounding the main inductor to carry the annular, peripheral part of the susceptor.

The preferred embodiment of a brazing press according to the invention and shown in FIG. 4 will therefore be mainly characterized by the fact that it further comprises, inserted between said insulating sleeve and said annular peripheral part of the susceptor to which it is respectively fixed, a cylindrical support piece, made of a metal alloy having a thermal conductivity of low value, and which surrounds the main inductor block, in order to make the alternating magnetic flux generated by the main inductor in the flat central part of the susceptor more homogeneous.

In this preferred embodiment of FIG. 4, the elastic connecting means 164 between the inductor block 6 and the support plate 7 consist of at least three assemblies of frustoconical washers 22 (“Belleville”) stacked, which are arranged symmetrically with respect to the axis of the inductor block 6. The washer springs 22 are threaded onto mounting means constituted by threaded rods at both ends 172, the upper 73 of which are screwed into tapped holes in the support plate 7 and the lower 174 of which are inserted into suitable holes. of U-shaped coupling jumpers 60 secured to the upper face of the inductor block 6 and are retained there by means of retaining nuts 212 whose position determines the length of the stroke of the block 6. The stacked springs 22 take support at the top on a flange 175 secured to the rod 172 and at the bottom on a hollow cylindrical block 165 threaded onto the rod 172 and the height of which is chosen according to the number of washers 22 stacked and in the manner of e stack them to obtain the desired pressure.

The means for axially guiding the movements of the inductor block 6 are constituted here by a single assembly disposed in the axis thereof and comprising a hollow sleeve 184 screwed by its upper end into a tapped hole 185, made in the bottom of a bowl 191 of the support plate 7 and by a guide rod 61 disposed in the axis of the block 6 and integral with the upper end of the latter. The rod 61 is inserted into the recess 186 of the sleeve 184 in an adjusted fashion.

The sleeve 15 fixed at the top to the support plate 7, surrounding the inductor block 6 and carrying at the bottom the peripheral, annular part of the susceptor 101, is produced here in three integral parts, the upper 151 of which is made of non-refractory insulating material (bakelized wood, for example) and the lower part of which, 155, adjoins the annular part 101 of the susceptor, is, according to the present addition, made of a refractory metal alloy of low thermal conductivity and high mechanical resistance,

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such as a nickel alloy with other metals such as chromium, iron and / or molybdenum, for example.

Such an alloy of nickel (from 70 to 80 percent), chromium (from 17 to 14 percent) and iron (from 10 to 5 percent) and generally marketed under the name "INCONEL" (Trademark registered by "THE INTERNATIONAL NICKEL CO., INC. ”) Has a relative magnetic permeability close to that of air (from 1.003 to 1.007) and a thermal conductivity substantially around the thirtieth of that of copper so as to limit thermal losses by leaks. These are also limited by the fact that this alloy has excellent mechanical strength, which makes it possible to reduce the thickness of the lower part 155 of the sleeve 15 which is in the form of a belt or of a thin metal ring, but practically undeformable.

The metal belt 155 is fixed at the top to the intermediate part 154 forming a flange (or to the upper part 151 directly) and, when the latter 154 fears heat (such as bakelized wood, for example), the top of the belt 155 comprises , brazed on it, a metal tube 156 (of copper, for example) traversed by a cooling fluid.

At the bottom, the belt 155 in "INCONEL" carries the annular part 101 of the susceptor, either directly fixed on it using screws or rivets, for example, or removably using hooks 157 or tabs in U, made of stainless refractory metal, one end of which is made integral with the belt 155 and the other end of which, free, is introduced by notches 105 in an annular groove 104 formed in the cylindrical outer wall of the peripheral part 101 of the susceptor . The removable mounting of the peripheral part 101 of the susceptor on the lower part 155 of the sleeve 15 of the support has the advantage of allowing brazing on stampings 20 of different shapes (pots or pans) but of diameters close to diffusing coatings 3 also of various shapes and thicknesses using the same inductor assembly or the easy change of the annular part 101 during breakage or wear.

The fact that this closed belt 155 represents, with respect to the main inductors 1 which it surrounds and the additional 110 which surrounds it, a short-circuited turn traversed by an induced current which has the effect of shielding and reducing the intensity of heating on the periphery of the flat central part of the bottom of elements 3 and 20 and, therefore, to make the temperature distribution more homogeneous, the path of the induced current must be well concentrated in certain places. It is therefore sometimes advantageous to make there oblong vertical slits 158 the number, lengths and locations of which are determined experimentally, when the reduction in temperature on the periphery proves to be too great with a belt 155 full (for articles small diameter, for example). An intermediate part 154 has been inserted between the insulating upper part 151 and the conductive lower part 155 of the sleeve.

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radial projection which is intended to carry the additional inductor 110 by means of threaded rods 134, nuts 131 and 133, and parts made of insulating material coming into contact with the metallic parts thereof. These insulating parts include a sleeve 135 provided with a flange 136, threaded on the threaded rod 134, and two washers 137, 138 the first 137 of which is rigid to determine the spacing between the turns of the additional inductor 110 and the second 138, as well as the collar 136 of the sleeve 135, serve to isolate the inductor 110 from the screws 131. The upper thread 139 of the rod 134 is screwed into a tapped hole in the central part forming the flange 154 of the sleeve 15, which is , preferably also in non-refractory insulating material (a plastic material or a compound of polymerizing resins and glass fibers, textile or wood, for example).

It should be noted that the upper 151 and intermediate 154 (flange) insulating parts of the sleeve 15 can be made in one piece, with significant material losses during its machining.

In the preferred embodiment of FIG. 4, the additional inductor 110, coupled to the annular, peripheral part 101 of the susceptor, is constituted here by two superimposed turns, composed of two solid conducting rings 111, surrounding at a short distance the side wall of the peripheral part 101 of the susceptor . Each ring 111 carries on its periphery, attached to it by brazing, a tube 112 of the same material (copper) traversed by a cooling fluid.

The press according to the present invention makes it possible to obtain, by means of a single jack press, two pressures independent of one another and acting respectively, one on the flat central part, and the other on the curved edges of the elements to be brazed 20 and 3.

It should also be noted that the metal support belt 154 of the annular, peripheral part of the susceptor 101 can also be used in the first embodiment of the invention, shown in FIG. 1, where it is the sleeve 15 which is coupled to the press frame by the elastic means 16 and the inductor block 6 is fixed.

The present invention obviously also extends to equivalent means accessible to those skilled in the art, such as, for example, presses where the mandrel is fixed and the inductor block with its accessories are mounted on the sound rod. cylinder.

The invention is applicable in particular to the brazing of heat diffusing coatings made of a metal which is a good thermal conductor, such as aluminum or copper, on stainless steel cooking vessels (deep drawn) (saucepan, frying pan or pressure cooker). It is also possible to braze two or more coatings on the same stamp to create multilayer structures (stainless steel, aluminum or copper and steel).

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4 sheets of drawings

Claims (10)

622,729 1. Brazing press for joining a stamping (2, 20) comprising a planar circular bottom, a skirt symmetrical around an axis and curved parts connecting the bottom to the skirt, to a previously formed part, called a diffuser coating (3 ), in front, cover said bottom and at least partially said curved parts of the stamping (2,20), said press comprising a fixed support frame (7), a single jack fixed to the frame (7), a mandrel (4 , 5) supporting the stamping (2.20) and carried by the movable rod (14) of the jack, a block (6) containing a main inductor (1) coupled to the frame (7) and located above and opposite of the mandrel, intermediate heating means made of a ferromagnetic metal (100, 101) comprising two separate parts, constituted by a flat central part (100) inserted between said coating (3) and said inductor block (6) which carries it, and a peripheral portion (101) of annular shape whose inner face has a shape adapted to that of the outer face e peripheral parts of the diffuser coating (3) covering the curved parts of the stamping (2, 20), an additional inductor (110 or 111,112) surrounding the peripheral part (101) of the intermediate means, in order to heat it and a sleeve cylindrical (15, 140, 151, 154, 155) made, at least in part, of a non-deformable insulating material coaxially surrounding the main inductor block (6) and coupled at its end opposite the mandrel (4, 5) to said part annular device (101) as well as to the additional inductor (110, 111, 112) surrounding it and, at its other end, to the frame (7) of the press, said press being characterized in that the one of the central (100) and peripheral (101) parts of the intermediate heating means (100, 101) or the block (6) or sleeve (15) which carry them, are coupled to the frame (7) of the press using elastic coupling means, calibrated (16, 160, 161, 164) and guided by means of guide means (17,18,170, 180,171,183, 61,186) so as to be able to effect a limited axial displacement relative to the other part (101, 100) which is fixed to the frame (7), so that, when said single cylinder pushes the mandrel (4, 5) towards the block (6), pressures respectively exerted on the respective central and peripheral portions of the bottom of the pressed (2, 20) and of the coating (3) are independent of one another. 2. Press according to claim 1, characterized in that said inductor block (6) is joined to the frame (7) by elastic means (160, 161, 164) allowing it to move parallel to its axis and providing pressure acting on the respective flat central parts of the pressed part (20) and of the covering (3) independently of that exerted by the jack (14) and by means of the peripheral annular part (101) of the intermediate heating means, on the curved parts of the stamping (20) and on the periphery of the diffuser coating (3), said elastic means (160, 161, 164) allowing, when after brazing, the mandrel (4, 5) moves away down, d ejecting the finished product from the peripheral part (101) which, by surrounding it, is likely to retain it. 2 3. Press according to one of claims 1 and 2, characterized in that said elastic means (16, 160,161,164) are constituted by calibrated springs (22, 160), arranged symmetrically with respect to the common axis of the inductor block (6), the sleeve (15, 150,151) and the jack (14). 4. Press according to one of claims 1, 2 and 3, characterized in that the part movable relative to the frame (7) is also joined to said frame (7) by means of retaining means (21, 210, 211, 212) limiting the amplitude of its axial movement in the direction of the mandrel (4, 5) or relative to the fixed part. 5. Press according to one of claims 1, 2, 3 and 4, characterized in that the guide means (17,170, 171, 18, 180, 183) consist of at least one guide rod (17, 170, 171) sliding in at least one bore (18,180,183) respectively integral with the axially movable part (15 or 6) or the fixed part (6 or 15, 150 , 151), arranged symmetrically with respect to the common axis of the block (6), the sleeve (15,150,151) and the jack (14). 6. Press according to claims 4 and 5, characterized in that the retaining means (21, 210, 212) are constituted by radial projections mounted at the free ends of the guide rods (17,170,171) which emerge from the bores (18,180,183) in which they slide. 7. Press according to one of claims 5 and 6, characterized in that the elastic means (16,160,161) constituted by springs (160) or assemblies (16,161,164) of elementary springs (22), provided with axially oriented openings , are arranged so as to surround the rods (17, 170) or the sleeves (181) provided with bores (183) in which the latter slide, forming part of the guide means (17-18,170-180, 171-181- 183). 8. Press according to one of claims 2 to 7, characterized in that said support sleeve (15) comprises an insulating upper part (151, 154) fixed at the top to the frame (7) of the press and a lower part (155) made of a metal alloy with low thermal conductivity and carrying at the bottom the peripheral part (101) of the intermediate heating means, the two parts (15,154, 155) of the sleeve (15) being fixed to each other , said metal lower part (155) forming a closed short-circuit belt around the main inductor, in order to make the distribution of temperatures more uniform in the flat central part (100) of the intermediate heating means. 9. Press according to claim 8, characterized in that said alloy is an alloy of nickel with at least one other metal chosen from the class comprising chromium, iron or molybdenum. 10. Press according to one of claims 8 and 9, characterized in that said metallic lower part (155) comprises oblong notches oriented axially, making it possible to limit the trajectory of the induced currents at desired locations so as to obtain the optimal temperature homogenization.