Cooking pot and its manufacture

Abstract

A method of manufacturing a cooking pot comprises deep-drawing stainless steel sheet to define a pot-shaped intermediate blank comprising an early-stage rim (48d); exposing a distal portion (50) of the early-stage rim (48d) to a forging to move material from the distal portion (50) of the early-stage rim (48d) to a proximal portion (52) located closer to a side wall (14) of the cooking pot, thereby increasing a material thickness of the proximal portion (52) of the early-stage rim (48d); and trimming off the forged distal portion (50) of the early-stage rim (48d) from the proximal portion (52), to form a cut rim having a free edge having a material thickness which is greater than a material thickness of the side wall (14).

Description

[0001] COOKING POT AND ITS MANUFACTURE

[0002] Field of the invention

[0003] The present invention relates to a cooking pot, and to a method of manufacturing a cooking pot.

[0004]

[0005] Kitchen utensils such as cooking pots are often made of stainless steel. There are different types of stainless steel, wherein some are more corrosion resistant than others. As cooking pots operate in a wet environment and at elevated temperatures, highly corrosion resistant steel grades are often used. Corrosion resistance may also be increased by polishing the cooking pot surface to a high-gloss finish. A high corrosion resistance, however, typically comes at an increased cost of material and / or manufacture.

[0006]

[0007] It is an object to solve, or at least mitigate, parts or all of the above drawbacks of prior art. To this end, according to a first aspect, there is provided a method of manufacturing a cooking pot, the method comprising providing a flat cooking pot blank of stainless steel sheet; deep-drawing the cooking pot blank to define a potshaped intermediate blank comprising a bottom wall extending in a bottom wall plane, a circumferential side wall extending from the bottom wall, and an early-stage rim extending radially away from a pot axis normal to the plane of the bottom wall; exposing a distal portion of the early-stage rim to a forging to move material from the distal portion of the early-stage rim to a proximal portion of the early-stage rim, said proximal portion being closer to the side wall than said distal portion, thereby increasing a material thickness of the proximal portion of the early-stage rim; and trimming off the forged distal portion of the early-stage rim from the proximal portion of the early-stage rim, to form a cut rim defined by the proximal portion of the early-stage rim, the cut rim having a free edge having a material thickness which is greater than a material thickness of the side wall. The provision of an edge of the rim which is free, i.e. which is not rolled or folded, reduces the tendency of the edge to corrode. Moreover, by locally increasing the material thickness of the cut rim, a thinner material may be used for the remainder of the cooking pot, thereby reducing cost of the raw material as well as the cost of manufacture of the cooking pot, without thedrawback of a reduced corrosion resistance which otherwise generally accompanies a small material thickness at an edge. The move of material from the trimmed, distal portion of the early-stage rim to the proximal portion, which remains on the cooking pot also after cutting off said distal portion, reduces material spillage. Preferably, said distal portion of the rim, which distal portion is forged, extends about most of, such as about at least 75% of, or more preferably about the entire circumference, of the early-stage rim. Typically, the free edge of the cut rim may have a material thickness which is greater than the original material thickness of the flat cooking blank. The material thickness of the free edge of the cut rim may also be greater than the material thickness of the bottom wall. According to embodiments, the flat cooking pot blank may be made of stainless steel sheet having an original thickness of 0,6 mm or less, for example 0,5 mm, and the thickness of the proximal portion of the early-stage rim, after forging the distal portion, may be at least 0,7 mm. Alternatively or additionally, the material thickness of the proximal portion of the early-stage rim, after forging the distal portion, may be less than 1,5 mm, and more preferably, 1,0 mm or less.

[0008] Thereby, only a moderate amount of material needs to be moved from the distal portion of the early-stage rim to the proximal portion of the early-stage rim in the forging operation, which facilitates manufacture of the cooking pot. Alternatively or additionally, the material thickness of the proximal portion of the early-stage rim, after forging the distal portion, may be less than 2 times the original thickness of the stainless steel sheet of the flat cooking pot blank; such relative dimensions facilitate manufacture of the cooking pot. Preferably, the forging is a cold-forging, i.e. the forging is performed at a temperature of less than the recrystallization temperature of the stainless steel sheet, and more preferably the forging is performed at room temperature. Any or all method steps described herein, including the deep-drawing step and / or any coining step, as the case may be, may be performed as a coldworking process, i.e. take place at a temperature of less than the recrystallization temperature of the stainless steel sheet, and more preferably at room temperature. The pot axis defines a cylindrical coordinate system, and thereby also defines a radial direction and a circumferential direction in relation to the pot axis, which directions are sometimes referred to hereinbelow.

[0009] According to embodiments, the method may further comprise coining the free edge of the cut rim to form a coined rim. The strain induced in the surface of the cut rim by coining also contributes to a further increase in corrosion resistance of the free edge. The coined rim may have a material thickness in any of the intervals definedhereinabove for the proximal portion of the early-stage rim. The free edge may be coined to a rounded profile to increase the user comfort of handling the cooking pot.

[0010] According to embodiments, deep-drawing said cooking pot blank may comprise deep-drawing the cooking pot blank to further define a first handle of said pot-shaped intermediate blank, said first handle forming part of the proximal portion of the early-stage rim and extending away from the pot axis. Thanks to forming the handle as an integral part of the rim, the interface between the first handle and the side wall will be free from any structures, such as welds or similar, which might otherwise initiate corrosion. Preferably, the thickness of the free edge of the handle is increased by forging the distal portion of the early-stage rim, which is trimmed off, along the handle. A second handle, opposite to the first handle, may be formed in the same process.

[0011] According to embodiments, providing a flat cooking pot blank of stainless steel may comprise cutting said flat cooking pot blank as one of a plurality of flat cooking pot blanks cut in a dense hexagonal circle-packing pattern from a stainless steel sheet, each of said plurality of flat cooking pot blanks having a base shape integrally formed with at least one protruding area, formed in an interstice between base shapes of adjacent flat cooking pot blanks, wherein said first handle is formed, at least partly, preferably entirely, from said at least one protruding area of said flat cooking pot blank. Thereby, the first handle is formed of interstitial material which would otherwise be mere waste, which reduces the cost of the cooking pot. The base shapes may be circular, or may have any other suitable shape which comprises a circle fit in the dense hexagonal circle-packing pattern. The interstice may be trianguloid. Likewise, the at least one protruding area may be trianguloid. According to embodiments, the base shape of each of said plurality of flat cooking pot blanks is integrally formed with two diametrically opposing protruding areas formed in respective interstices between the base shapes of adjacent flat cooking pot blanks, wherein said first handle and a second handle are formed, at least partly, preferably entirely, of respective ones of the two protruding areas to form a stock pot.

[0012] According to embodiments, the method may further comprise cutting an elongate heat-barrier slot in said first handle, the heat-barrier slot having a direction of elongation extending in the circumferential direction of the pot axis, and / or deep-drawing or embossing said first handle to form at least one elongate embossment having a direction of elongation extending away from the pot axis, and / or deep-drawing or embossing said first handle to define a cup-shape which tapers downwards.

[0013] According to embodiments, the method may further comprise shot peening at least the free edge of the rim, and preferably also the outer surface of the side wall, more preferably the entire surface of the cooking pot including a bottom face of the bottom wall.

[0014] According to a second aspect, there is provided a cooking pot comprising a bottom wall extending along a bottom wall plane, a pot axis being defined as the normal to the plane of the bottom wall; and a circumferential side wall of stainless steel sheet extending from the bottom wall to a rim having a free edge, wherein the free edge of the rim has a material thickness which is greater than a material thickness of the side wall. As explained above, the free edge reduces the tendency of the edge to corrode, and the greater material thickness of the free edge, compared to other parts of the cooking pot, provides further corrosion resistance without the added cost of a greater material thickness overall. Typically, the free edge of the rim may also have a material thickness which is greater than the material thickness of the bottom wall, and / or a material thickness which is greater than the material thickness of the rim at a distance of 3 mm from the free edge of the rim towards the pot axis. According to embodiments, the bottom wall may be circular, and the side wall may have a circular cross-section as seen along the pot axis. The circumferential side wall may define, together with the bottom wall, a pot bowl having a height-to-width ratio of at least 0,35. Such a height-to-width ratio is particularly well suited for e.g. a stock pot or a saucepan. Alternatively or additionally, the pot bowl may be configured to hold a maximum volume of liquid content of at least 2 litres; for example, the pot bowl may be configured to hold a maximum volume of liquid content of between 2,5 litres and 5,5 litres. Alternatively or additionally, a cooking pot aperture of the pot bowl may have a maximum width of between 150 mm and 250 mm, and / or the pot bowl may have a total height along the pot axis of at least 80 mm, for example between 80 mm and 180 mm. Preferably, the side wall has a material thickness of less than 1 ,2 mm, and more preferably of less than 0,7 mm, and / or the bottom wall has a material thickness of less than 1 ,2 mm, and more preferably of less than 0,7 mm. For e.g. saucepans and stock pots, such a material thickness enables obtaining a low manufacturing cost without substantially hampering the performance of the cooking pot. The rim may be forged and / or cut rim and / or coined.According to embodiments, the cooking pot may further comprise a first handle extending away from the pot axis, wherein said first handle is integrally formed of said stainless steel sheet as an extension of the rim. Thanks to said first handle being integrally formed with the rim, there is no attachment interface, such as a weld or fastener, between the first handle and the side wall. The lack of an attachment interface adds further corrosion resistance to the cooking pot. Moreover, the first handle can be formed in the same forming process as the side wall. Thanks to the high position of the handle at the rim, heat transfer from the bottom wall and from any hot content within the cooking pot is kept low. Corrosion tends to increase with increasing temperature; accordingly, the position of the handle also contributes to reduce any tendency of the handle to corrode. The high position of the handle at the rim may also make the cooking pot easier to stack in an efficient manner.

[0015] Preferably, said first handle is free from any other elements attached thereto, i.e. said first handle is in its entirety formed from said stainless steel sheet extension of the rim; thereby, no such other elements may initiate corrosion.

[0016] According to embodiments, said first handle may have the shape of a tab tapering in a direction radially away from the pot axis, wherein the tab preferably has the shape of an isoceles trapezium. Thereby, the shape of the handle is adapted to the trianguloid shape of interstitial spaces between base circles in a hexagonal circle packing pattern of cooking pot blanks in a stainless steel sheet. Such a cooking pot is particularly material-saving and cost-efficient.

[0017] According to embodiments, an upper perimeter of the side wall may define a cooking pot aperture, and said first handle may extend from a handle base in a direction away from the side wall by a total radial handle length being less than 0,4 times a total width of the cooking pot aperture, and / or said handle base may have a circumferential width, along the perimeter of the cooking pot aperture, being less than 0,6 times the total width of the cooking pot aperture. Such a size is particularly well adapted for dense hexagonal circle packing of cooking pot blanks in a stainless steel sheet. Moreover, the limited circumferential width of the handle base limits the heat transfer to the handle. Alternatively or additionally, preferably, the handle base has a circumferential width of at least 0,3 times the total width of the cooking pot aperture; this results in a high strength and rigidity of the handle, which permits the use of a thin material thickness.

[0018] According to embodiments, said first handle may comprise a proximal handle portion adjacent to the side wall, and a distal handle portion adjacent to the freeedge, wherein the material thickness of the proximal handle portion is thinner than the material thickness of at least a portion of the distal handle portion, wherein preferably the distal handle portion has a free edge which is forged and / or coined. Thanks to the reduced thickness of the proximal handle portion, less heat will be conducted to the distal handle portion, which thereby becomes more comfortable to grip. At the same time, the comparatively higher thickness of the at least a portion of the distal handle portion makes the distal handle portion comfortable to hold.

[0019] Preferably, the proximal handle portion has a thickness of 0,6 mm or less, and / or the distal handle portion has a thickness of 0,7 mm or more.

[0020] According to embodiments, said first handle may comprise a heat-barrier slot, preferably an elongate heat-barrier slot having a direction of elongation extending in the circumferential direction of the cooking pot. Thereby, heat transfer to a distal handle portion, adjacent to the free edge, will be reduced by the air gap defined by the heat-barrier slot.

[0021] According to embodiments, said first handle may comprise at least one elongate embossment having a direction of elongation extending away from the side wall. The embossment may be obtained by any suitable method, such as deep-drawing, stamping or embossing. The elongate embossment increases the stiffness of the first handle, which enables the use of a thin material thickness for the first handle. Thereby, heat transfer to a distal handle portion, adjacent to the free edge, will be limited by the thin material thickness of the first handle, which increases user comfort. According to embodiments, the first handle may define a cup-shape. A through-hole may be formed in the bottom of the cup shape to allow any water to run out therefrom; thereby, the risk of corrosion in the handle is further reduced. The through-hole may also reduce heat transfer from the pot to the handle and may be elongate to define a heat-barrier slot as defined above.

[0022] According to embodiments, said first handle may comprise a proximal handle portion adjacent to the side wall, and a distal handle portion adjacent to the free edge, wherein the distal handle portion is positioned lower than the proximal handle portion. Thereby, gripping of the handle without slipping is facilitated.

[0023] According to embodiments, the cooking pot may further comprise a second handle opposite to said first handle. The second handle may be shaped in accordance with the first handle, and may be positioned opposite to the first handle across the cooking pot aperture.According to embodiments, the side wall may extend from the bottom wall to a cooking pot aperture, and the side wall may define, together with the bottom wall, a pot bowl, wherein the pot bowl tapers downwards, i.e. in the axial direction from the cooking pot aperture towards the bottom wall. The tapering makes the cooking pot nestable, which saves valuable transport space by enabling several identical cooking pots to be nested or stacked one inside the other. Preferably, the pot wall tapers monotonously, i.e. without any non-tapering segments, in the downwards direction along at least 80%, and more preferably at least 90%, of an axial height of the pot wall. The side wall may, for example, define the shape of a right -frustum of a cone. By optionally having one or more handles integrally formed with the rim, the high position of the handle’s interface with the side wall allows a tight nesting of cooking pots without the handle(s) of a first, inner cooking pot interfering with the side walls of a second, outer cooking pot in which the first cooking pot is to be nested. Preferably, the side wall forms a side wall inclination angle with the pot axis of less than 12° at the height of the axial centre of the pot bowl; such a side wall inclination angle is particularly well suited for a saucepan or a stock pot. Preferably, the side wall forms a side wall inclination angle with the pot axis of more than 4° along at least 80%, and more preferably at least 90%, of an axial height of the pot bowl; thereby, a compact nestability is obtained. For example, the side wall may form a side wall inclination angle with the pot axis of between 6° and 10°. Preferably, the side wall has a material thickness of less than 1,2 mm, and more preferably of less than 0,7 mm; a thin wall reduces the stacking height, and allows cooking pots to be more tightly stacked.

[0024] According to embodiments, said first handle may define a cup-shape which tapers downwards. Thereby, when nesting cooking pots one inside another, also the handles can be nested one inside the other. Preferably, the cup shape of said first handle tapers monotonously, i.e. without any non-tapering segments, in the downwards direction along at least 50%, and more preferably at least 80%, of an axial height of the cup shape.

[0025] According to embodiments, the stainless steel sheet may be of a ferritic stainless steel type, such as an AISI 430 standard stainless steel. Ferritic stainless steel is generally much less expensive than austenitic stainless steel, but has the drawback that it has a lower resistance against corrosion. Thanks to the increased corrosion resistance provided by the design as defined by any or all of the above embodiments, a ferritic stainless steel can be used for the pot without unduly increasing the tendency to corrode.According to embodiments, a surface of the pot may be shot-peened. High-gloss polishing is an expensive and time-consuming process, requiring up to 20 process steps. However, thanks to the increased corrosion resistance provided as defined by any or all of the above embodiments, no high-gloss polishing is required to obtain a sufficient corrosion resistance - not even if the cooking pot is made of a ferritic stainless steel. Instead, shot-peening, which can be made in a single process step, provides a sufficient resistance of the surface against stains and corrosion. The shot-peening induces permanent strain in the outermost surface of the pot, which counteracts the formation of pores and pits that may lead to corrosion.

[0026] According to embodiments, the material thickness of the side wall may be 0,6 mm or less, whereas the material thickness of the rim at the free edge may be at least 0,7 mm. Preferably, also the bottom wall has a thickness of 0,6 mm or less.

[0027] According to embodiments, the material thickness of the rim at the free edge may be less than 1,5 mm, and more preferably, 1,0 mm or less. Such a thickness facilitates obtaining the material thickness of the rim at the free edge by forging. Alternatively or additionally, the material thickness of the rim at the free edge may be less than 2 times the material thickness of the side wall; such relative dimensions also facilitate manufacture of the cooking pot.

[0028] According to embodiments, the bottom wall may be integrally formed of a single piece of stainless steel sheet together with the side wall and the rim. Thereby, there will be no corrosion-sensitive attachment interface, for example a weld, between the bottom wall and the side wall. Moreover, by having the bottom wall formed of said stainless steel sheet, the bottom wall will be free from any integrated heat transfer element(s) of e.g. aluminium, which might otherwise initiate corrosion. Heat transfer from below may anyway be kept at an attractive level, for example by having a bottom wall thickness of 0,6 mm or less.

[0029] According to embodiments, the entire cooking pot may be integrally formed from a single piece of stainless steel sheet. Thereby, no material interfaces may initiate corrosion, such that corrosion is minimized.

[0030] According to embodiments, the cooking pot may be draw-formed, and in particular, deep-drawn.

[0031] According to embodiments, said rim may be forged to obtain said material thickness which is greater than the material thickness of the side wall.

[0032] It is noted that embodiments of the invention may be embodied by all possible combinations of features recited in the claims. Further, it will be appreciated that thevarious embodiments described for the method according to the first aspect are all combinable with the various embodiments described for the cooking pot according to the second aspect of the present invention, and vice versa.

[0033] Brief description of the drawings

[0034] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and nonlimiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

[0035] Fig. 1 A is a view of a cooking pot illustrated in a first perspective;

[0036] Fig. 1 B is a view of the cooking pot of Fig. 1 A illustrated in a second perspective;

[0037] Fig. 2A is a plan view of a stainless steel sheet with a cutting pattern illustrated thereupon;

[0038] Fig. 2B is a perspective view of the stainless steel sheet of Fig. 2A, with a flat cooking pot blank cut therefrom following the cutting pattern;

[0039] Fig. 3A is a perspective view of deep-drawing machinery configured to perform a first deep-drawing step applied to the flat cooking pot blank of Fig. 2B;

[0040] Fig. 3B is a perspective view of the deep-drawing machinery of Fig. 3A performing the first deep-drawing step on the flat cooking pot blank of Fig. 3A to result in a first pot-shaped intermediate blank;

[0041] Fig. 3C is a perspective view of deep-drawing machinery performing a second deep-drawing step, on the first pot-shaped intermediate blank of Fig. 3B, to result in a second pot-shaped intermediate blank;

[0042] Fig. 3D is a perspective view of deep-drawing machinery performing a third deep-drawing step, on the second pot-shaped intermediate blank of Fig. 3C, to result in a third pot-shaped intermediate blank;

[0043] Fig. 3E is a perspective view of deep-drawing machinery performing a fourth deep-drawing step, on the third pot-shaped intermediate blank of Fig. 3D, to result in a fourth pot-shaped intermediate blank;

[0044] Fig. 4A is a vertical section of an early-stage rim of the fourth pot-shaped intermediate blank of Fig. 3E;

[0045] Fig. 4B corresponds to the vertical section of Fig. 4A, and illustrates a forging step applied to a distal portion of the early-stage rim of Fig. 4A;Fig. 4C corresponds to the vertical section of Figs 4A-B, and illustrates a step of trimming off the distal portion of the early-stage rim of Fig. 4A from a proximal portion of the early-stage rim to result in a cut rim;

[0046] Fig. 4D corresponds to the vertical section of Figs 4A-C, and illustrates a step of coining the cut rim of Fig. 4C to result in a coined rim;

[0047] Fig. 5A is a schematic illustration of a shot-peening step applied to a surface of the cooking pot of Figs 1 A and 2A;

[0048] Fig. 5B is a magnified section view of a surface region of the cooking pot, and illustrates the impact of a single shot-peening ball onto the surface of the cooking pot;

[0049] Fig. 6 is a plan view of the cooking pot of Figs 1 A and 1 B as seen from above; Fig. 7 is a section of the cooking pot of Figs 1 A and 1 B, the section taken along the plane VII-VII indicated in Fig. 6;

[0050] Fig. 8 is a section of the cooking pot of Figs 1 A and 1 B, the section taken along the plane VIII-VIII indicated in Fig. 6, along with a magnified detail view of a rim of the cooking pot;

[0051] Fig. 9 is a perspective view in section, the section taken along the plane VII-VII indicated in Fig. 6, of two instances of the cooking pot of Figs 1A and 1B nested one inside the other;

[0052] Fig. 10 is a perspective view of stacks of instances of the cooking pot of Figs 1 A and 1 B nested one inside the other, along with stacks of lids shaped to fit the cooking pots, all packaged between opposing carton trays to define a unit load shaped to fit on a pallet; and

[0053] Fig. 11 is a flow chart illustrating a method of manufacturing the cooking pot of Figs 1A and 1B.

[0054] All the drawings are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.

[0055] Detailed description of the exemplary embodiments

[0056] Figs 1A and 1B illustrates a cooking pot 10 from two different perspectives. The cooking pot 10 comprises a bottom wall 12 extending along a bottom wall plane P (Fig. 1B). A circumferential side wall 14 extends from the bottom wall 12 to an upper perimeter 18 of the side wall 14, which defines a circular cooking pot aperture 20. The side wall 14 defines, together with the bottom wall 12, a pot bowl 22. In the illustrated embodiment, the pot bowl 22 is shaped and dimensioned to hold amaximum volume of liquid content of about three litres. The bottom wall 12 is circular, and the side wall 14 follows a circular path about an axis of symmetry defined by a pot axis A, which is a normal to the plane P of the bottom wall 12. A rim 16 extends from the upper perimeter 18 of the side wall 14 in a direction radially away from the pot axis A. The entire cooking pot 10 is integrally formed of a single piece of AISI 430 standard ferritic stainless steel sheet 24. The stainless steel sheet 24 of the cooking pot 10 is free from any folds or other elements where the stainless steel sheet is double-folded or otherwise forms any small cavities which may retain water and initiate corrosion. In particular, the rim 16 is unhemmed, i.e. it does not have any hem, whether closed or open, where the rim 16 is rolled or folded onto itself. Instead, a free edge 16a of the rim 16 faces radially away from the pot axis A.

[0057] The cooking pot further comprises a first handle 26 and a second handle 28 extending away from the pot axis A. The handles 26, 28 are integrally formed of the stainless steel sheet 24 as an extension of the rim 16, and are free from any other elements attached thereto, as well as from any hems.

[0058] In the illustrated embodiment, the first and second handles 26, 28 are identical, and for reasons of simplicity, only the first handle 26 is described in detail; however, it will be appreciated that the second handle 28 may alternatively be different, and may present none or only a subset of the various features described for the first handle 26. The first handle 26 has a proximal handle portion 26a adjacent to the side wall 14, and a distal handle portion 26b adjacent to the free edge 16a of the extension, defined by the first handle 26, of the rim 16. The first handle 26 defines a cup-shape 30 extending downwards along the axial direction of pot axis A. Two elongate embossments 32a, 32b extend from the cup shape 30 towards the pot axis A and the upper rim 18 of the side wall 14. The cup shape 30 and the embossments 32a, 32b increase the stiffness of the first handle 26. At its bottom, the cup shape 30 is provided with a through-hole 34. The through-hole 34 is configured as an elongate slot having its direction of elongation extending in the circumferential direction of the cooking pot 10, i.e. in the circumferential direction about the pot axis A. The through-hole 34 serves double duty; it allows any water or other liquid to run out of the cupshape 30, and the air gap defined by the elongate slot serves as a heat-barrier which decreases the heat transfer from the proximal portion 26a of the handle 26 to the distal portion 26b of the handle 26.

[0059] Figs 2A-5B illustrate a method of manufacturing the cooking pot 10 of Figs 1A and 1 B. Starting with Figs 2A and 2B, a sheet 36 of stainless steel is provided, forexample as a strip or band of stainless steel sheet rolled off from a roll. In the illustrated embodiment, the stainless steel sheet 36 has an original thickness dO (Fig.

[0060] 2B) of 0,5 mm. Flat cooking pot blanks 38 are cut from the stainless steel sheet 36; the provision of the steel sheet 36 from a roll facilitates providing a continuous flow of flat cooking pot blanks 38 to subsequent manufacturing steps. Each flat cooking pot blank 38 has a shape which somewhat resembles a lemon, with a circular base shape 38a which is to define the pot bowl 22 (Fig. 1A) of the final cooking pot 10, and two protruding areas 38b extending in opposite directions from the circular base shape 38a. The protruding areas 38b are trianguloid-shaped, and are to define the handles 26, 28 of the final cooking pot 10. The flat cooking pot blanks 38 are cut from the stainless steel sheet 36 with their respective circular base shapes 38a arranged in a dense hexagonal circle-packing pattern 39, such that each cooking pot blank 38 is surrounded by up to six immediately adjacent flat cooking pot blanks 38. The protruding areas 38b are formed of trianguloid interstices 39a formed between the contours of the circular base shapes 38a of adjacent flat cooking pot blanks 38, as best illustrated in Fig. 2A.

[0061] The subsequent manufacturing steps will be described only with reference to a single flat cooking pot blank 38; it will be appreciated that all cooking pot blanks 38 may be processed in the same manner. Now referring to Figs 3A-3E, the overall shape of the cooking pot 10 (Fig. 1A) is obtained by deep-drawing the flat cooking pot blank 38, in a plurality of deep-drawing steps, to define a pot-shaped intermediate blank. Starting with Fig. 3A, a rim 38c of the flat cooking pot blank 38 is clamped between a clamp 42 and a first forming tool 40a comprising a first deep-drawing cavity, which in the view of Fig. 3A is hidden below the flat cooking pot blank 38. In a first deep-drawing step, illustrated in Fig. 3B, a first deep-drawing press tool 44a presses the circular base shape 38a (Fig. 2B) of the flat cooking pot blank 38 into the deep-drawing cavity of the first forming tool 40a, which cavity matches the shape of the first deep-drawing press tool 44a, so as to shape the flat cooking pot blank 38 into a first pot-shaped intermediate blank 46a. In the first deep-drawing step, the outer rim 38c (Fig. 2B) of the cooking pot blank 38 is drawn towards the deep-drawing cavity as the cooking pot blank 38 is pressed further into the deep-drawing cavity, but the outer rim 38c remains, after the first deep-drawing step, within the original plane of the flat cooking pot blank (Fig. 3A) as a first early-stage rim 48a of the first pot-shaped intermediate blank 46a.In a second deep-drawing step, illustrated in Fig. 3C, the first early-stage rim 48a (Fig. 3B) of the first pot-shaped intermediate blank 46a (Fig. 3B) is clamped between a clamp 42 and a second forming tool 40b comprising a second deep-drawing cavity (not illustrated). A second deep-drawing press tool 44b presses the first pot-shaped intermediate blank 46a into the deep-drawing cavity of the second forming tool 40b, so as to shape the first pot-shaped intermediate blank 46a into a second pot-shaped intermediate blank 46b. Part of the first early-stage rim 48a has now been drawn into the deep-drawing cavity of the second forming tool 40b, but a distal portion of the first early-stage rim 48a (Fig. 3B) remains as a second early-stage rim 48b after the second deep-drawing step.

[0062] Fig. 3D illustrates a third deep-drawing step, in which the second early-stage rim 48b of the second pot-shaped intermediate blank 46b (Fig. 3C) is clamped between a clamp 42 and a third forming tool 40c comprising a third deep-drawing cavity (not illustrated). A third deep-drawing press tool 44c presses the second potshaped intermediate blank 46b into the deep-drawing cavity of the third forming tool 40c., so as to shape the second pot-shaped intermediate blank 46b into a third potshaped intermediate blank 46c. The third pot-shaped intermediate blank 46c comprises a third early-stage rim 48c.

[0063] A fourth deep-drawing step, illustrated in Fig. 3E, shapes the first and second handles 26, 28, including the cup shapes 30 (Fig. 1A) and embossments 32a, 32b (Fig. 1 A), and establishes the final shape of the pot bowl 22. In the fourth deep-drawing step, the third early-stage rim 48c (Fig. 3D) of the third pot-shaped intermediate blank 46c (Fig. 3D) is clamped between a clamp 42 and a fourth forming tool 40d comprising a fourth deep-drawing cavity (not illustrated), which matches the outer shape of a fourth deep-drawing press tool 44d. The fourth deep-drawing press tool 44d presses the third pot-shaped intermediate blank 46c into the deep-drawing cavity of the fourth forming tool 40d, so as to shape the third pot-shaped intermediate blank 46c into a fourth pot-shaped intermediate blank 46d comprising a fourth early-stage rim 48d. One of the deep-drawing steps, such as the third deep-drawing step of Fig. 3D or the fourth deep-drawing step of Fig. 3E, also adds a slight depression 12a, as seen from below, to the bottom face 12b of the bottom wall 12. The depression 12a reduces any tendency of the bottom face 12b to become convex in response to repeated heating and cooling during use.

[0064] After deep-drawing, the pot bowl 22 has assumed its final shape, and the original rim 38c of the flat cooking pot blank 38 (Fig. 3A), after having been deformedin the deep-drawing steps, now defines the early-stage rim 48d of the fourth potshaped intermediate blank 46d, which early-stage rim 48d extends radially away from the pot axis A.

[0065] Figs 4A-4C illustrate the processing of the fourth early-stage rim 48d.

[0066] Preferably, the fourth early-stage rim 48d is processed as described in the following along its entire circumference about the pot bowl 22 (Fig. 3E).

[0067] Starting with Fig. 4A, the fourth early-stage rim 48d has a material thickness d1 corresponding to the original material thickness dO of the stainless steel sheet 36 (Fig. 2B), i.e. 0,5 mm. Also the side wall 14 has a material thickness d3 of about 0,5 mm.

[0068] In a first edge processing step, illustrated in Fig. 4B, a distal portion 50 of the fourth early-stage rim 48d is exposed to a forging to move material from the distal portion 50 of the fourth early-stage rim 48d to a proximal portion 52 of the fourth early-stage rim 48d, the proximal portion 52 being located closer to the side wall 14 than the distal portion 50. The forging thereby thins out the distal portion 50 of the fourth early-stage rim 48d, and increases the material thickness of the proximal portion 52 of the fourth early-stage rim 48d; in the illustrated embodiment, the distal portion 50 of the fourth early-stage rim 48d is forged to increase the material thickness d2 (Fig. 4C) of the proximal portion 52 of the fourth early-stage rim 48d to 0,7 mm. The forging typically takes place at ambient temperature.

[0069] In a second edge processing step, the forged distal portion 50 of the fourth early-stage rim 48d is cut off from the proximal portion 52 of the fourth early-stage rim 48d, to form a cut rim 54 defined by the proximal portion 52 of the fourth early-stage rim 48d as illustrated in Fig. 4C. The cut rim 54 has a free edge 54a having the material thickness d2, which is greater than the original material thickness dO of the stainless steel sheet 36 (Fig. 2B). The material thickness d2 is also greater than the material thickness d3 of the side wall 14, as well as the original material thickness d1 of the fourth early-stage rim 48d (Fig. 4A). The material thickness d2 of the free edge 54a of the cut rim 54 is also greater than the material thickness (not illustrated) of the bottom wall 12 (Fig. 1A), which maintains the original material thickness dO of the stainless steel sheet 36 (Fig. 2B).

[0070] In a third edge processing step illustrated in Fig. 4D, the free edge 54a of the cut rim 48c is coined to a rounded profile, to define a coined rim 56. The material thickness of the coined rim 56 remains greater than the original material thickness dO of the stainless steel sheet 36 (Fig. 2B), the material thickness d3 of the side wall 14,and the material thickness d1 of the fourth early-stage rim 48d (Fig. 4A); typically, the coined rim 56 maintains the material thickness d2 obtained in the forging step.

[0071] The elongate through-holes 34 (Fig. 1A) of the first and second handles 26, 28 are cut, for example laser-cut or punched, at any suitable stage along the process in a non-illustrated method step.

[0072] Then, as a finishing step, the entire cooking pot 10, which now has the shape illustrated in Figs 1Aand 1B, is shot-peened in a shot-peening step illustrated in Figs 5A and 5B. The shot peening entails striking the surface 10a of the cooking pot 10, of which only a small portion is illustrated in Figs 5A and 5B, with round shot 60 of e.g. metal, glass or ceramic with force sufficient to create plastic deformation of the surface 10a. The plastic deformation results in a compressive residual stress layer of the surface 10a, which gives the cooking pot 10 a matte appearance and protects the surface 10a against corrosion.

[0073] Fig. 6 illustrates the cooking pot 10 as seen from above. The upper perimeter 18 of the side wall 14, which also defines the maximum fill level of the cooking pot 10 at which it will start to overflow, follows a circular path C1 about the cooking pot aperture 20. The outer perimeter 56a of the coined rim 56 (Fig. 4D) follows a circular path C2 except for at the first and second handles 26, 28, where the outer perimeter 56a of the coined rim 56, which defines the free edge 16a (Fig. 1A) of the cooking pot’s 10 rim 16 (Fig. 1A), instead follows the outer contour of the respective handle 26, 28. The pot bowl 22 has a largest width W, at the level of the cooking pot aperture 20, of about 200 mm.

[0074] Each of the first and second handles 26, 28 extends from a handle base B, defined as a circumferential segment extending along the perimeter 18 of the pot aperture 20 between the circumferential positions of two points B1, B2, which points mark where the outer perimeter 56a leaves the circular path C2 and starts to extend radially beyond the circular path C2. In Fig. 6, the base B and points B1, B2 are indicated for the first handle 26 only.

[0075] Each of said first and second handles 26, 28 has a respective circumferential width HW, measured between the points B1, B2 along the handle base B, of about 95 mm. Moreover, each of said first and second handles 26, 28 extends radially away from the side wall, i.e. the perimeter 18 of the cooking pot aperture 20, by a total handle length HL, in the radial direction, of about 35 mm. Each of the first and second handles 26, 28 is configured as a tab having the general shape of an isoceles trapezium tapering in a direction radially away from the pot axis A.Turning now to Fig. 7, the pot bowl 22 has a total axial height H, from the bottom wall plane P to the level of the pot aperture 20, of about 120 mm. Accordingly, the pot bowl 22 has a height-to-width ratio H / W of about 0,6. As illustrated, the distal handle portion 26b is positioned on a lower level than the proximal handle portion 26a, which facilitates gripping the handle 26. The distal handle portion 26b also comprises the coined rim 56, which has the material thickness d2 (Fig. 4D) which is greater than the material thickness of the proximal handle portion 26a, which proximal handle portion 26a maintains the approximate original material thickness dO (Fig. 2B) of the steel sheet 36.

[0076] As illustrated in the magnified view of a section of the rim 16 in Fig. 8, the material thickness d2 at the free edge 16a of the rim 16 is also greater than a material thickness d4 of the rim 16 at a distance d of about 3 mm from the free edge 16a of the rim 16 towards the pot axis A. In the illustrated embodiment, at the distance d from the free edge 16a, the rim 16 maintains the original material thickness dO (Fig. 2B) of the stainless steel sheet 36, i.e. d4=d0.

[0077] As also illustrated in the section of Fig. 8, the pot bowl 22 tapers downwards, i.e. in the axial direction from the cooking pot aperture 20 towards the bottom wall 12. At the height of the axial midpoint between the bottom wall plane P and the pot aperture 20, i.e. at the axial position corresponding to H / 2 along the pot axis A, the side wall 14 forms a side wall inclination angle a of about 8° with the pot axis A. For clarity of illustration, the side wall inclination angle a is illustrated in relation to a line which is parallel to the pot axis A. The side wall inclination angle a is in this embodiment constant along a main part of the height H, such that at least a portion of the side wall 14 defines a right frustum of a cone. Adjacent to the pot aperture 20 and adjacent to the bottom wall 12, the side wall inclination angle is greater than 8°. The tapering of the pot bowl 22 which results from the side wall inclination angle a makes the cooking pot 10 nestable, such that identical cooking pots 10 can easily be stacked one inside the other.

[0078] Referring back to Fig. 7, also the respective cup shapes 30 of the first and second handles 26, 28 taper downwards, such that when nesting cooking pots 10 one inside another, also the handles 26, 28 of the cooking pots 10 can be nested one inside the other.

[0079] The section of Fig. 9 illustrates a stack 70 of two identical cooking pots (Fig. 1A) as described hereinabove. The stack 70 comprises a first cooking pot 10 and a second cooking pot 10’. The pot bowl 22 of the first cooking pot 10 is nested insidethe pot bowl 22’ of the second cooking pot 10’ to an axial nesting increment N, defined as the axial distance between the bottom wall planes P, P’ of the first and second cooking pots 10, 10’, of about 5% of the total axial height H (Fig. 7) of the pot bowl 22. Each additional identical cooking pot 10 in the stack 70 of cooking pots increases the axial height of the stack 70 by a respective additional axial nesting increment N. Moreover, the first handle 26 of the first cooking pot 10 is nested inside the first handle 26’ of the second cooking pot 10’, and the second handle 28 of the first cooking pot 10 is nested inside the second handle 28’ of the second cooking pot 10’, such that the handles 26, 26’, 28, 28’ do not unduly increase the axial nesting increment N.

[0080] Fig. 10 illustrates the highly efficient stacking of a large number of cooking pots 10 as described hereinabove, which stacking is enabled by the shape of the cooking pots 10. The cooking pots 10 are packaged, together with stacks of lids 72 fitting the cooking pots 10, between a pair of mutually opposing carton trays 74a, 74b.

[0081] Fig. 11 is a flow chart summarizing the method of manufacturing the cooking pot 10 (Fig. 1A) described in detail with reference to Figs 2A-5B.

[0082] In step 101 , the flat cooking pot blank 38 (Fig. 2A) of stainless steel sheet is provided, optionally by cutting said flat cooking pot blank 38 as one of a plurality of flat cooking pot blanks cut in a dense hexagonal circle-packing pattern 39 (Fig. 2A) from a stainless steel sheet 36 (Fig. 2A).

[0083] In step 102, the flat cooking pot blank 38 is deep-drawn, optionally in more than one deep-drawing sub-step, to define the pot-shaped intermediate blank 46d (Fig. 3E).

[0084] In step 103, the distal portion 50 (Fig. 4B) of the early-stage rim 48d (Fig. 3E) is exposed to a forging to move material from the distal portion 50 of the early-stage rim 48d to a proximal portion 52 (Fig. 4B) of the early-stage rim 48d, thereby increasing the material thickness of the proximal portion 52 of the early-stage rim 48d.

[0085] In step 104, the forged distal portion 50 of the early-stage rim 48d is trimmed off from the proximal portion 52 of the early-stage rim 48d, to form the cut rim 54 (Fig.

[0086] 4C) having the free edge 54a of a material thickness d2 which is greater than the material thickness d3 of the side wall 14.

[0087] In optional step 105, the through-hole 34 defining the elongate heat-barrier slot is cut in the first handle 26, and optionally in the second handle 28 (Fig. 1A).In optional step 106, the free edge 54a (Fig. 4C) of the cut rim 54 is coined to form a coined rim 56 (Fig. 4D).

[0088] In optional step 107, at least the free edge of the rim, i.e. the cut rim 54 (Fig.

[0089] 4C) or the coined rim 56 (Fig. 4D) as the case may be, and preferably the entire cooking pot 10, is shot-peened.

[0090] Some of the steps of Fig. 11 may be performed in a different order, in particular the optional steps 105-107.

[0091] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. For example, the manufacturing method described hereinabove comprises several deep-drawing steps. However, the cooking pot may alternatively be deep-drawn in one single deep-drawing step, or may be shaped by any other suitable method which does not involve deep-drawing at all.

[0092] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

Claims1. A method of manufacturing a cooking pot, comprisingproviding a flat cooking pot blank (38) of stainless steel sheet;deep-drawing the cooking pot blank (38) to define a pot-shaped intermediate blank (46d) comprising a bottom wall (12) extending in a bottom wall plane (P), a circumferential side wall (14) extending from the bottom wall (12), and an early-stage rim (48d) extending radially away from a pot axis (A) being normal to the plane (P) of the bottom wall (12);exposing a distal portion (50) of the early-stage rim (48d) to a forging to move material from the distal portion (50) of the early-stage rim (48d) to a proximal portion (52) of the early-stage rim (48d), said proximal portion (52) being located closer to the side wall (14) than said distal portion (50), thereby increasing a material thickness (d2) of the proximal portion (52) of the early- stage rim (48d); andtrimming off the forged distal portion (50) of the early-stage rim (48d) from the proximal portion (52) of the early-stage rim (48d), to form a cut rim (54) defined by the proximal portion (52) of the early-stage rim (48d), the cut rim (54) having a free edge (54a) having a material thickness (d2) which is greater than a material thickness (d3) of the side wall (14).

2. The method according to claim 1 , further comprising coining the free edge (54a) of the cut rim (54) to form a coined rim (56).

3. The method according to any of the preceding claims, wherein deep-drawing said cooking pot blank (38) comprises deep-drawing the cooking pot blank (38) to further define a first handle (26) of said pot-shaped intermediate blank (46d), preferably said first handle (26) forming part of the proximal portion (52) of the early-stage rim (48d) and extending away from the pot axis (A).

4. The method according to claim 3, wherein providing a flat cooking pot blank (38) of stainless steel comprisescutting said flat cooking pot blank (38) as one of a plurality of flat cooking pot blanks (38) cut in a dense hexagonal circle-packing pattern (39) from a stainless steel sheet (36), each of said plurality of flat cooking pot blanks (38) having a base shape (38a) integrally formed with at least one protruding area(38b), formed in an interstice (39a) between base shapes (38a) of adjacent flat cooking pot blanks (38), wherein said first handle (26) is formed, at least partly, preferably entirely, from said at least one protruding area (38b) of said flat cooking pot blank (38).

5. The method according to any of the claims 3-4, further comprisingcutting a heat-barrier slot (34), preferably an elongate heat-barrier slot (34), in said first handle (26), the heat-barrier slot (34) preferably having a direction of elongation extending in the circumferential direction about the pot axis (A), and / ordeep-drawing or embossing said first handle (26) to form at least one elongate embossment (32a, 32b) having a direction of elongation extending away from the pot axis (A), and / ordeep-drawing or embossing said first handle (26) to define a cup-shape (30) which tapers downwards.

6. The method according to any of the preceding claims, further comprising shot peening at least the free edge of the rim (54, 56), and preferably also the outer surface of the side wall (14), more preferably the entire surface (10a) of the cooking pot (10) including a bottom face of the bottom wall (12).

7. The method according to any of the preceding claims, wherein the distal portion (50) of the early-stage rim (48d) is forged to increase the material thickness (d2) of the proximal portion (52) of the early-stage rim (48d) to a material thickness (d2), after forging, of less than 1,5 mm, and / or to a material thickness (d2), after forging, of less than 2 times an original thickness (dO) of the stainless steel sheet of the flat cooking pot blank (38) prior to forging.

8. A cooking pot comprisinga bottom wall (12) extending along a bottom wall plane (P), a pot axis (A) being defined as the normal to the bottom wall plane (P) of the bottom wall (12); anda circumferential side wall (14) of stainless steel sheet (24) extending from the bottom wall (12) to a rim (16) having a free edge (16a), wherein the free edge (16a) of the rim (16) has a material thickness (d2) which is greater than a material thickness (d3) of the side wall (14).

9. The cooking pot according to claim 8, further comprising a first handle (26) extending away from the pot axis (A), wherein said first handle (26) is integrally formed of said stainless steel sheet (24) as an extension of the rim (16).

10. The cooking pot according to claim 9, wherein said first handle (26) has the shape of a tab tapering in a direction radially away from the pot axis (A), wherein the tab preferably has the shape of an isoceles trapezium.

11. The cooking pot according to any of the claims 9-10, whereinan upper perimeter (18) of the side wall (14) defines a cooking pot aperture (20),said first handle (26) extends from a handle base (B) in a direction away from the side wall (14) by a total radial handle length (HL) being less than 0,4 times a total width (W) of the cooking pot aperture (20), and / orsaid handle base (B) has a circumferential width (HW), along the circumferential rim (18) of the cooking pot aperture (20), being less than 0,6 times the total width (W) of the cooking pot aperture (20).

12. The cooking pot according to any of the claims 9-11, wherein said first handle (26) comprises a proximal handle portion (26a) adjacent to the side wall (14), and a distal handle portion (26b) adjacent to the free edge (16a), wherein the material thickness (d1) of the proximal handle portion (26a) is thinner than the material thickness (d2) of at least a portion (56) of the distal handle portion (26b), wherein preferably the distal handle portion (26b) has a free edge (16a) which is forged and / or coined.

13. The cooking pot according to any of the claims 9-12, wherein said first handle (26) comprises a heat-barrier slot (34), preferably an elongate heat-barrier slot (34) having a direction of elongation extending in a circumferential direction about the pot axis (A).

14. The cooking pot according to any of the claims 9-13, wherein said first handle (26) comprises at least one elongate embossment (32a, 32b) having a direction of elongation extending away from the side wall (14).

15. The cooking pot according to any of the claims 9-14, wherein said first handle (26) comprises a proximal handle portion (26a) adjacent to the side wall (14), and a distal handle portion (26b) adjacent to the free edge (16a), wherein the distal handle portion (26b) is positioned on a lower level than the proximal handle portion (26a).

16. The cooking pot according to any of the claims 9-15, further comprising a second handle (28) opposite to said first handle (26).

17. The cooking pot according to any of the claims 8-16, wherein the side wall (14) extends from the bottom wall (12) to a cooking pot aperture (20), and the side wall (14) defines, together with the bottom wall (12), a pot bowl (22), wherein the pot bowl (22) tapers downwards, i.e. in the axial direction (A) from the cooking pot aperture (20) towards the bottom wall (12).

18. The cooking pot according to claim 17 in combination with any of the claims 9- 16, wherein said first handle (26) defines a cup-shape (30) which tapers downwards.

19. The cooking pot according to any of the claims 8-18, wherein the stainless steel sheet (24) is of a ferritic stainless steel type, such as an AISI 430 standard stainless steel.

20. The cooking pot according to any of the claims 8-19, wherein a surface (10a) of the cooking pot (10) is shot-peened.

21. The cooking pot according to any of the claims 8-20, wherein the material thickness (d3) of the side wall (14) is 0,6 mm or less, whereas the material thickness (d2) of the rim (16) at the free edge (16a) is at least 0,7 mm.

22. The cooking pot according to any of the claims 8-21, wherein the material thickness (d2) of the rim (16) at the free edge (16a) is less than 1,5 mm, and / or wherein the material thickness (d2) of the rim (16) at the free edge (16a) is less than 2 times the material thickness (d3) of the side wall (14).

23. The cooking pot according to any of the claims 8-22, wherein the bottom wall (12) is integrally formed from a single piece of stainless steel sheet (24) together with the side wall (14) and the rim (16).

24. The cooking pot according to any of the claims 8-23, wherein the entire cooking pot (10) is integrally formed from a single piece of stainless steel sheet (24).

25. The cooking pot according to any of the claims 8-24, wherein the cooking pot (10) is draw-formed, and in particular, deep-drawn.

26. The cooking pot according to any of the claims 8-25, wherein said rim (16) is forged to obtain said material thickness (d2) which is greater than the material thickness (d3) of the side wall (14).

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