AU2008257251A1 - Culinary article with improved contact surface and manufacturing method - Google Patents

Description

1 CULINARY ARTICLE WITH IMPROVED CONTACT SURFACE AND MANUFACTURING METHOD The present invention relates to a culinary article, the 5 base of which has, at the lower outer face, at least one added metal insert covering at least partly this base. The article, including its base, typically consists of soft metal such as aluminium. The way of manufacturing the article and/or its base with an added metal insert is also relevant. 10 In the present application, the term of "metal" covers metal and metal alloy. From EP-A-0960667, a culinary article is known comprising: - a metal pot(dish) locally defining a lower base portion 15 for the article, where said dish(pot) has, along a section perpendicular to this base, a toothed area, - and at least one added base insert lining the underneath of said metal dish, at least locally at the location of its base portion, this insert which has an 20 apparent lower face, being in a harder metal than the one of the metal dish and having sectionally, at least one perforated or toothed area, attached by male/female fit engagements with the toothed area of said metal dish. The "teeth" are folds or drawn parts of the plate 25 defining a plurality of pads creating under the base, supporting discontinuities when they are laid on a support. These "teeth" or pads, like the possible orifices made in the insert, are typically organized along concentric circles. If the insert is perforated, the orifices are filled with 30 the soft metal of the metal dish. Different drawbacks are noted: - the insert/"soft" base attachment is similar to fastening or crimping (in the fashion of a stone which is set), essentially, 35 - this attachment is imperfect; in the lower face, the soft base which receives the insert is pre-drawn, - the orifices may be imperfectly filled, 2 - if softer filling material juts out from the lower level of the added insert, contact with for example a glass ceramic plate risks scratching the latter, in particular if the softer material is aluminium. 5 An object of the invention aims at overcoming all or part of these drawbacks. Another object is to avoid the occurrence of imperfections, related to the manufacturing method or to the use, or further foreign members at the soft metal/added insert interfaces, further inducing risks of scratches on 10 brittle surfaces and/or surface contact defects. Indeed, bearing imperfections when the article is laid, risk causing defects of stability and/or deposit of the soft metal on the support. Moreover, in the case when the hard metal insert has the 15 function of allowing the article to be heated by induction, via a suitable generator, the larger the number of orifices through the insert, the more the efficiency of heating by induction risks being impaired. In order to at least limit all or part of these drawbacks 20 and to improve the situation, the invention proposes, according to one feature, that around said perforated or toothed area of the added base insert, an area lower down is found, defining a peripheral continuously solid crown-shaped contact surface, in said harder metal. 25 Thus, it is favourably provided that this contact surface area covers the base portion of the dish, around said male/female fit engagements, and has a lower face, all or part of which is at least slightly lower down relatively to the lower limit of said perforated or toothed area and/or of the 30 toothed area of said metal dish. In this way, the pressure(support) of the culinary article applied on a supporting element will be concentrated there. Moreover it is recommended that said "peripheral contact surface area" should have a width (L hereafter) larger than 35 the shortest distance (dl) separating two successive teeth, along a straight line joining the centre of the base and a peripheral edge of the latter.

3 Two manufacturing methods are also proposed hereafter. They may be used for obtaining the aforementioned article, at least in the case when the added insert comprises perforations. Complementarily or alternatively, with these 5 methods it is already possible to manufacture a base, in particular for a culinary article. Once such a reinforced, stable and not very aggressive base is obtained, the remainder of the article may be made. For this, continuation of the deformation under the pressure 10 of the original block of soft metal is proposed until a sidewall has developed for the article. Other advantages and particularities of the present invention will now be presented in embodiments given hereafter as non-limiting examples. 15 By applying this invention, the possibility is considered of further improving the thermal and mechanical properties of the base of the article, including during induction heating or high temperature bakes of the coating(s) to be added, such as the anti-adherent one typically provided in the inner face, 20 notably of the base (detachment problems, blistering), or further during repeated thermal shocks. In the drawings which will support the examples: - Fig. 1 shows a culinary article diagram, according to a sectional vue perpendicular to the base, according to a first 25 embodiment in accordance with the invention, - Figs. 2 and 3 more widely show according to the same view, second and third embodiments of an article according to the invention, respectively; the parts, areas, means... are marked thereon with the same marks as in Fig. 1, but 30 respectively provided with a prime (') and with a quotation mark ("), - Fig. 4 shows an alternative with at least one partly toothed base, according to the same sectional view, - Figs. Sa, 5b, Sc and 6a, 6b, 6c show steps for applying 35 two manufacturing methods which may be used within the scope of the invention, - Fig. 7 shows a bottom view of Fig. 2, 4 - and Fig. 8 shows the actually bent base of the article of Fig. 1. In the present description, any cooking item comprising typically at least one handle and one (hollow) dish receiving 5 the product of the preparation to be heated or cooked, is called a "culinary article". The base of the dish is a sensitive portion, since it is the most subject to heat from a suitable source. Frying pans, saucepans..., are thus relevant. In Figs. 1-3, the culinary article 1, 1', 1'' comprises a 10 hard metal portion, la, 1', la" and a softer metal portion lb, lb', lb". Both of these portions are assembled under the article in order to form a performing reinforced base. The portion la, la', la" may be in stainless steel, the portion lb, lb', lb" in aluminium. 15 The portion lb, lb', lb" is preferably a single-piece, as illustrated, and has a transverse base wall 21, 21', 21'' from which a sidewall 3, 3, 3" rises. It has a hollow dish shape. At least one portion of the base wall is lined underneath by the hard metal portion, la, la' , la", which appears as a 20 perforated base insert. In Fig. 1, the insert la has a central area 23 surrounded with a contact surface area 25 through which the culinary article 1 may bear upon a support. The contact surface area 25 is continuously solid (i.e. here without any orifice) and 25 crown-shaped. The central area 23 is crossed right through by orifices 230 fit filled with the soft metal of the base wall 21, for assembling. These orifices are either regularly distributed or not, in one or more areas, typically along several radii which 30 may be concentric and begin close to the centre of the plate la (see on this point Figs. 2 and 3). Thus, the insert la which provides an apparent lower face lla, shows in Fig. 1, in a sectional view, at least one perforated area 231 attached by male/female fit engagements 35 with a toothed area 210 of the metal dish lb.

5 Around all or part of the area 210 a continuously solid area 211 is found, covered or lined, underneath by the peripheral contact surface area 25. In order that the pressure of the article 1 exerted on 5 its supporting element is concentrated towards the contact surface area 25, the latter has a lower face, all or part of which is at least slightly lower down (d) relatively to the lowest limit (1) of the areas 231 and 210. Thus, it should be understood that the illustrations of article bases in Figs. 1, 10 2, 3 are at a large scale and do not in fact have a flat lower face (such as lla in Fig. 1), but a curved or recessed face in order to ensure a position below the contact surface area 25, as in the illustration of Fig. 8 where the curvature is exaggerated. 15 If for example the orifices 230 were not totally filled with the soft metal of the base wall 21, the guard height (d) would increase relatively to the sole low limit of the perforated area 231. In Fig. 8, the straight line which joins the centre of 20 the base and the peripheral edge 27 of the latter is marked as 25a. Along this straight line (i.e. along a section perpendicular to the base and containing the straight line) the peripheral contact surface area 25 has a width (1) larger 25 than the shortest distance (dl) separating two successive teeth 210a, 210b of the area 210. Preferably, this width (L) will be larger than or equal to the one (L') between the inner 12 and outer 11 limits respectively of a group of two outer (210c') and inner (210a') 30 teeth respectively, of the metal dish separated by at least one third tooth (210b'); i.e. typically of the order of 7mm, see Fig. 2. Thus, the bearing/attachment/induction yield compromise will be performing. 35 In order to ensure the guard height (d) and thus place lower down relatively to it (them) at least one portion of said lower face lla of the base, here of the peripheral 6 contact surface area 25, the perforated area 231, and here the whole base plate from the centre up to its contact surface area 25, extends along a curved lower surface 100a, which is concave downwards (and coincides here with 1). 5 In order to attach together at best the portions la, la', la" and lb, lb', 1b", the added base insert is favourably also engaged(inserted) into the metal dish, in an area 29, 29', 29" located away, set back from the contact surface area 25 and from said more central male/female fit engagements, such as 10 210a, 231 in Fig. 1 and 210", 231" in Fig. 3. This area of mating male/female fit engagements such as 29 is favourably located beyond the periphery of the contact surface area such as 25 and the surface such as 211 of the dish which is covered by the latter. 15 In Fig. 1, the area 29 receives the attachment to the dish lb of an attachment portion 31 which peripherally extends the contact surface area 25, in a single piece with the insert la, and which defines an edge set back relatively to this area 25. 20 This edge 31 externally surrounds the area 25, to which it is connected by a stiffening fold 33, and has orifices 310 fit filled with the metal of the dish lb, thereby achieving the aforementioned mating male/female fit engagements of the area 29. 25 The fold 33 is tilted at an angle, outwards. In Figs. 2 and 3, one therefore has also an attachment portion 31', 31" in a single piece with the peripheral contact surface area 25', 25" and the added base insert la', la", which may have the same previous characteristics as the one la 30 - idem for the dish 1b' , lb" with a base 21' , 21" facing lb and 21 - except that the attachment portion 31', 31" defines, for the part la', la" a raised peripheral edge 35', 35" where there is a male/female fit engagement for retaining this part in (underneath) the base of the metal dish lb', lb", in an 35 area therefore located, set back from said contact surface area 25', 25".

In Fig. 2, the retaining male/female fit engagement 29' comprises orifices 310' which cross the attachment portion 31' and fit filled with the metal of the dish. The orifices 310' are located in the curvature, here the radius. 5 In Figs. 1 and 2, the raised peripheral portion 35, 35' is only inserted into the border of the dish and is therefore entirely visible. In Fig. 1, this portion has at its base a curvature which connects the edge 35' and the area 25' and is crossed by the orifices 310' . In Fig. 1, said raised portion 10 35 defines the perforated outer peripheral edge 31. In Fig. 3, the folded curved peripheral edge 35" ends in the dish lb" where it is therefore embedded, engaged therein. Among the characteristics useful for applying the invention, but not indispensable, it will be noted that: 15 - the area 25, 25', 25" may be at least globally flat, - this solid contact surface area is a continuous crown; the crown may be in several portions, - a continuously solid area may surround the toothed area 210, 210', 210" of the dish lb, lb', lb", 20 - the attachment portion 31, 31', 31" is in a single piece with the insert, the same for the contact surface area; otherwise the attachment portion may be used for attaching the contact surface area, the central portion of the insert being moreover inserted, such as for example in the preceding 25 embodiment, this however complicates manufacturing, - the added insert la, la', la" may not comprise a perforated area 231, 231', 231" - or only one or more of such area(s) - but, as a replacement or complement, at least one toothed male/female engagement area as in Fig. 4, 30 - the perforated or toothed area of the base plate and/or the toothed area of the metal dish under which this plate is applied extend(s) along a curved lower surface, concave downwards; as regards this characteristic, a shoulder such as a downward fold may be provided. 35 In Fig. 4, 241d shows a toothed male/female fit engagement area of the insert 10a cooperating with the toothed area 210d of the dish 10b under which this insert is 8 flattened, with its contact surface area 25d lower down. This is less performing in terms of attachment, but beneficial for induction. Two manufacturing methods are more particularly proposed 5 in order to obtain the illustrated culinary articles, or at least one base for such articles. Indeed, it is explained later on that the base may be obtained alone on the one hand, the remainder of the article may be produced on the other hand, in particular subsequently to the base. 10 Hereafter, the insert la, la' or la" is a single piece and perforated rather than toothed, the modifications for a toothed solution (see for example Fig. 4) being within the competence of one skilled in the art, the filling of the orifices is then replaced with that of the steps between 15 teeth. A both perforated and toothed solution may be contemplated. This having been specified, according to the first method illustrated in Figs. 5a and 5b, the following steps are conducted: 20 First one starts with a raw, non-preformed block 37 in lightweight metal - or therefore in lightweight alloy - on the one hand, and with the desired insert on the other hand. This insert is already perforated (and/or toothed) where it has to be so, as described earlier. 25 Let us consider that this is the one la" of Fig. 3. Typically (see Fig. 5a), initially one has a hollow insert (called cap) in a harder metal or metal alloy than that of the block 37 and having in its central portion, through-orifices 230". These orifices are positioned along successive radii 30 with, around them, the solid area 25" with its width (L) larger than the shortest distance (dl) separating two average successive radii of orifices of this central portion. And the solid area is therefore bordered on its perimeter, by the raised peripheral edge 35". 35 This hollow plate and the block are then applied against each other under pressure (see Fig. 5b) until: 9 - the metal or the softer alloy is pushed back under pressure (via a press) by forcing it to fill the recess 41 and said orifices 230" of the plate, the raised peripheral edge of which engages(is inserted) into the material of the block by 5 embedding its end therein, as this also seen in Fig. 3, and - at least one portion of the lower face of said solid area 25" is therefore placed at least slightly lower down (d) relatively to the lowest limit of the orifices of the central portion, so as to produce the expected supporting solid 10 peripheral contact surface area of the obtained assembly. Typically if, as shown in Fig. 5a, the peripheral edge 35" is initially vertical, it may be deformed inwards and/or outwards when applying the cap and the block under pressure, it will be positioned at an angle relatively to the central 15 portion of the insert (Fig. 5b). This may strengthen the attachment. According to the second method illustrated in Figs. 6a, 6b, it will proceed as follows on the other hand in order to notably obtain the solutions of Figs. 1 and 2. 20 Let us assume that we seek to achieve the solution of Fig. 1: we start again with a raw, non-preformed block 37 in light metal or light alloy on the one hand, and with the desired insert on the other hand. The insert is already perforated (or toothed) there where 25 it has to be, as described earlier. At this moment, it is still in the condition of a flat plate, or already slightly bent as in Fig. 6a, then with the aforementioned cavity, in order to provide the sought position lower down (d) (a peripherally shouldered shape with the same purpose may a 30 priori be also contemplated, as already indicated). The orifices 230 in the central portion may be positioned along successive radii with therefore around them the solid area 25 and its width (L) larger than (dl) . Here this area 25 is itself, on its perimeter, surrounded by the orifices 310 which 35 may be regularly distributed, all along a same radius. But the area 25 may only be irregularly surrounded by the orifices 310.

iU As earlier, this plate and the block 37 will then be applied under pressure against each other (always via a press) (see Fig. 6b) until: - the softer metal (the alloy) is pushed (back) under 5 pressure from the block, forcing it to have said plate la inserted at the surface and to fill (all) its orifices, by flowing, - the plate is folded towards the block, at the periphery of said solid area, by generating here the fold 33 in the 10 insert, therefore between the periphery of the area 25 and the outer edge 250, this fold being positioned at an angle relatively to the central portion 23 and generating the edge 31 which surrounds it externally and which therefore, like the whole insert, is engaged into the border of the block 37 (see 15 also Fig. 1), - and therefore at least one portion of the aforementioned lower face of said solid area 25 is also placed at least slightly lower down relatively to the lowest limit of the orifices 230 of the central portion, so as to produce as 20 already indicated the sought contact surface area lower down. Favourably, the fold 33 will have been generated between said area 25 and the peripheral orifices 310, so that the latter are found at the location of the edge. By conforming according to the alternative of Fig. 2, the 25 raised outer peripheral edge 35' will be folded just once in order to be inserted into the border of the block, the peripheral orifices 310' located in the connecting roundness having favoured a performing attachment, without interfering with the support. 30 Figs. Sa, 5b and 6a, 6b also illustrate that the pressure applied between each insert and the block 37 has naturally caused a deformation of this block which finally assumes the shape of the base, here 21 or 21''. As shown, it is further provided that beyond this step, 35 the deformation under pressure of the block will be favourably continued until the sidewall (3 in Fig. 5c and 3'' in Fig. 6c) is developed then forming a single piece with the base.

As regards the aforementioned application under pressure between the retained insert and the bloc 37, the latter will preferentially be performed within the scope of cold coining, with a press which may attain 2,000 tons. Provision is made 5 for manufacturing by stamping between a die and a punch, including for the skirt forming the sidewall in lightweight metal. Alternatively, it is possible to resort to flow-turning in order to make the sidewall. As regards the height of the drawn portion for engagement 10 of the insert, it will be favourably at least equal to the thickness of this insert. As regards the making of the contact surface area so that its lower face is below the remainder of the base, the latter may intervene as soon as the manufacturing of the insert (or 15 plate), with straightaway a bent shape for example, or later on, during the setting up of pressure between the insert and the block of soft metal, or even when the sidewall of the article is developed, or even within the scope of subsequent rework, via pressure exerted on this base. Different 20 techniques are known. Moreover, as regards the type of male/female fit engagement made, if the insert is perforated, it is in particular possible to resort to perforations with a lip, as taught in EP-A-688525. 25 It will also be recalled that an insert solution incorporating both perforated areas and toothed areas is covered by the invention. In Fig. 7, the bottom view, which refers back to the half sectional view of Fig. 2 (section II-II), shows a concentric 30 organization of the perforations or central holes 210', with the non-perforated peripheral contact surface 25' of width L and the outmost complementary attachment orifices 310'. The added harder insert la' is interrupted peripherally in 35' and the softer base lb appears at the location of the peripheral 35 crown, between 35' and 27, and in the location of the filled perforations (210', 310').

Claims (18)

1. A culinary article (1, 1', 1'') comprising: - a metal dish(lb, lb', lb'', 10b) locally defining a 5 lower base portion for the article where said dish has, along a section perpendicular to this base, a toothed area (210, 210'', 210d) - and at least one added base insert (la, la', la'', 10a) lining underneath said metal dish, at least locally in the 10 location of its base portion, said insert, which has an apparent lower face, being in an harder metal than that of the metal dish and having, along said section, at least one toothed area (231, 231'', 241d) attached by male/female fit engagements (230, 2330'', 210a, 210a') with the toothed area 15 (210, 210'', 210d) of said metal dish and around which a crown-shaped continuously solid peripheral contact surface area (25, 25', 25'', 25d) in said harder metal is disposed lower down, characterized in that, along a straight line (25a) joining the centre of the base and a peripheral edge (27) of 20 said base, said peripheral contact surface area (25, 25', 25'', 25d) has a width (L) larger than the shortest distance (dl) separating two successive teeth (210, 210'', 210d).

2. A culinary article (1, 1', 1'') comprising: 25 - a metal dish(lb, lb', lb'', 10b) locally defining a lower base portion for the article where said dish has, along a section perpendicular to this base, a toothed area (210, 210'', 210d) - and at least one added base insert (la, la', la'', 10a) 30 lining underneath said metal dish, at least locally at the location of its base portion, said insert, which has an apparent lower face, being in a harder metal than that of the metal dish and having, along said section, at least one perforated area (231, 231'', 241d) attached by male/female fit 35 engagements (230, 230'', 210a, 210a') with the toothed area (210, 210'', 210d) of said metal dish and around which a crown-shaped continuously solid peripheral contact surface 1iJ area (25, 25', 25'', 25d) in said harder metal is disposed, characterized in that, along a straight line (25a) joining the centre of the base and a peripheral edge (27) of said base, said peripheral contact surface area (25, 25', 25'', 25d) is 5 lower down and has a width (L) larger than the shortest distance (dl) separating two successive teeth (210, 210'', 210d).

3. The culinary article according to claim 1 or 2, 10 characterized in that the peripheral contact surface area (25, 25', 25'', 25d) is in a single part with the added base insert (la, la', la'', 10a).

4. The culinary article according to any of the 15 preceding claims, characterized in that the insert (la, la', la'', 10a) in hard metal is adapted for heating the article by induction.

5. The culinary article according to claim 3 or to 20 claim 3 and claim 4, characterized in that in an area located at a distance and set back from the peripheral contact surface area (25, 25', 25'', 25d) and from said male/female fit engagements (230, 230'', 210a, 210a'), the added base insert is locally inserted (29, 29', 29'') in the metal dish (lb). 25

6. The culinary article according to claim 3 or claim 3 and claim 4, characterized in that, in an area located beyond, at a distance and set back from said male/female fit engagements (230, 230'', 210a, 210'), of the periphery of said 30 peripheral contact surface area (25, 25', 25'', 25d) and of the surface of the dish covered by the latter, the added base insert is, complementarily, locally inserted (29, 29', 29'') into the metal dish. 35

7. The culinary article according to claim 3 or to claim 3 and any of claims 4 to 6, characterized in that the peripheral contact surface area (25, 25', 25d) extends for 14 attachment to said metal dish, peripherally, with an attachment portion (31, 31') in a single piece with the added base insert (la, la', 10a) and which defines a raised portion, set back relatively to said peripheral contact surface area 5 (25, 25', 25d) and having orifices (310, 310') fit filled with the metal of the metal dish(lb, lb', 10b).

8. The culinary article according to claim 7, characterized in that said raised peripheral portion (31') is 10 only inserted into the border of the dish(lb') and has at its base with a curvature crossed by orifices (310' ) fit filled with the metal of the metal dish.

9. The culinary article according to claim 7, 15 characterized in that said raised peripheral portion defines an outer peripheral edge (31) where orifices (310) are fit filled with the metal of the metal dish (lb).

10. The culinary article according to claim 3 or to 20 claim 3 and any of claims 4 to 6, characterized in that the peripheral contact surface area (25'') extends, for attachment to said metal dish(lb''), peripherally, with an attachment portion (31'') in a single piece with the added base insert (la'') and which defines a folded edge (35''), the end of 25 which is embedded in the material of the block and which is positioned at an angle relatively to the central portion of the insert (see Figs. 5b and 5c).

11. The culinary article according to any of the 30 preceding claims, characterized in that the peripheral contact surface area (25, 25', 25'', 25d) has, along said section perpendicular to the base and containing a straight line (25a) joining the centre of this base and a peripheral edge (27) of the latter, a width (L) larger than or equal to 35 that (L' ) between the respectively inner and outer limits of a group of two respectively outer (210c') and inner (210a') 15 teeth (210) of the metal dish separated by at least one third tooth (210b').

12. A manufacturing method adapted for being used in 5 order to obtain the culinary article according to claim 2 or to claim 2 and any of claims 3 to 11, the metal insert (la, la', la'', 10a) of which comprise at least one of said perforated areas (231, 231'', 241d), or at least one culinary article base, this method comprising the following steps: 10 - providing a non-perforated raw block (37) in light weight metal or in light weight metal alloy, - providing a hollow insert (la''), in a harder metal or metal alloy than that of the block, the insert having in the central portion, orifices (230'') crossing it, positioned 15 along successive radii with, around them, a solid area (25'') having, along a straight line (25a) joining the centre of the insert (la) and its periphery (27), a width (L) larger than the shortest distance separating two successive orifice radii (230'') of this central portion, this solid area (25'') being 20 bordered by a raised peripheral edge (35''), - applying under pressure the hollow plate and the block against each other until: * the metal or the softer alloy of the block (37) is pushed under pressure by forcing to fill the recess and said 25 orifices (230'') of the insert, the raised peripheral edge (35'') of which engages into the material of the block, while inserting its end therein, and * at least one portion (lb, lb', lb'') of the lower face of said solid area (25'') is placed at least slightly lower 30 down relatively to the lowest limit of the orifices (230'') of the central portion, so as to produce a solid peripheral contact surface area (25''), where the support of the obtained assembly put down on a supporting element is concentrated. 35

13. The method according to claim 12, characterized in that during the application under pressure, the raised peripheral edge (35'') is deformed and is positioned at an lb angle relatively to the central portion (231'') of this insert (la).

14. A manufacturing method adapted for being used for 5 obtaining the culinary article (1, 1') according to claim 2 or to claim 2 and any of claims 3 to 11, the metal insert (la, la') of which comprise at least one of said perforated areas (23, 231), or at least one culinary article base, this method comprising the following steps: 10 - providing a non-preformed raw block (37) in lightweight metal or in lightweight metal alloy, - providing a plate shape insert (la, la' ) in a harder metal or metal alloy than that of the block, the insert having in the central portion orifices (230) crossing it, positioned 15 along successive radii with, around them, a solid area (25, 25') having, along a straight line joining the centre of the plate and its periphery, a width larger than the shortest distance separating two successive orifice radii (230) of this central portion, this solid area itself being at least locally 20 surrounded by peripheral orifices (310, 31), - applying under pressure the insert and the block (37) against each other until: * the plate is folded towards the block (37), at the periphery of said solid area (25, 25'), 25 * the metal or the softer alloy of the block is pushed under pressure forcing it to have the insert (la, la') engage therein into the border, by filling said orifices of this insert, * at least one portion of the lower face (lla) of said 30 solid area (25, 25') is placed at least slightly lower down relatively to the lowest limit of the orifices (230) of the central portion (23, 231), so as to produce a solid peripheral contact surface area (25, 25') where the support of the obtained assembly put down on a supporting element is 35 concentrated. 1/

15. The method according to claim 14, characterized in that the produced fold (33) is between the solid contact surface area (25) and said peripheral orifices (310), so as to generate a raised outer peripheral edge (31), engaged into the 5 border of the formed block.

16. The method according to claim 14, characterized in that the fold (33) is produced so that said peripheral orifices (310, 31) are located in a curvature thereof. 10

17. The method according to any of claims 13 to 14, characterized in that deformation under pressure of the block (37) is continued until a single-piece sidewall (3, 3', 3'') is developed with the portion lined on the outside by said 15 insert (la, la, la'').

18. The method according to any of claims 12 to 17, characterized in that said insert is provided so that it has, on the side of the lower face (lla) of said solid area (25, 20 25', 25''), a curved surface (100a) concave downwards.