Cooking device

Abstract

Cooking device (1) comprising a pan-shaped holder (2) having a bottom (3) surrounded by a wall (4) extending between said bottom (3) and an elevated rim (5) of said holder (2) to provide a preparation space (21). Said wall (4) carries mutually spaced external fin members (71,72) enclosing a number of mutually separated flow channels (7) and extending substantially from said bottom (3) along the wall (4) towards said rim (5) of said holder (2). Said wall carries wall portions of said fin members (71,72) that diminish in size as they approach said rim. Said bottom (3) carries a bottom portions of said fin members (71) enclosing a number of mutually separated second channels (7) radially extending from a central region (30) of said bottom (3) towards a periphery of said bottom (3). Said channels (7) between the wall portions are a continuous extension of the channels (7) between the bottom portions.

Description

[0001]Cooking device The present invention relates to a cooking device, comprising a pan-shaped holder having a bottom surrounded by a wall, extending between said bottom and an elevated rim of said holder to provide a preparation space, wherein said pan shaped holder carries a number of mutually spaced fin members at a side across from said preparation space. Cooking devices, such as pans or pots, are often used in preparation of food. The pot or pan generally has a pan-shaped holder defining a preparation space in which food to be prepared is contained. The holder is placed near a heat source to heat at least part of said holder. One of the problems with conventional cooking devices is that when the holder is placed on a heat source, such as a gas burner, substantial thermal energy arising from combustion is dissipated and wasted as heat into the surrounding air since the cooking devices have weak energy capture rate, mainly due to its smooth bottom surface. This inefficiency is particularly problematic in industrial kitchens, where multiple heat sources are often used simultaneously, leading to increased energy consumption and heat loss. As a consequence, a substantial part of the generated heat dissipates into the environment. This is in particular undesired in industrial kitchens where multiple heat sources are often used simultaneously. In order to improve the thermal efficiency of a cooking device, US patent No.5,564,589 discloses a pot or pan featuring heat transferring fins in a spiral pattern to the bottom and helical patterns to the side wall of the pot or pan. These fins are meant to offer a more effective heat transfer from the stove flame to the pan or pot. However, the fins on this known pot or pan make the cooking device significantly more prone to contamination from caked-on spills or overflowing boils, which can be difficult to clean. The present invention has inter alia for its object, among others, to provide a cooking device with an improved heating efficiency in which these and other inconveniences and disadvantages are overcome to at least a considerable extent. In order to achieve the above-stated object, a cooking device of the type described in the opening paragraph, according to the invention, is characterized in that said fin members each comprise a wall portion connected to said wall of said holder, said wall portion having a diminishing size in a direction from said bottom to said rim. Hereinafter, fin members may interchangeably also be referred to as rib members to express their protruding nature. The size of the fin member refers particularly to the amount of protrusion relative to the (otherwise not disturbed) outside surface of the holder. The reduced size of the fin members as they are nearer to the rim results in a corresponding reduction of weight and material and, moreover, less heat loss to the surrounding air. Moreover, the decreasing height of these fin members as they reach the rim of the holder, leads to a corresponding decrease of the exposed cross sectional face around the holder that may be contaminated during cooking, particularly if the fins end at a distance to that rim. In that respect, a preferred embodiment of the cooking device according to the invention is characterized in that said wall portion comprises a distal tip that ends substantially flush with said wall of said holder. This way the wall portion vanishes into the wall of the holder to leave a substantially smooth surface at the top near the rim, which is particularly favourable from a perspective of ease of handling and cleaning, while optimizing thermal efficiency. The fin members define flow channels in between them that guide hot gasses that were heated by the heat source, particularly combustion gasses from a stove flame. The fin members provide additional contact area to said gasses along the bottom and wall of the preparation space that promotes a further transfer of heat conveyed by said gasses to the holder. Particularly, adjacent fin members may extend substantially parallel to one another. By extending substantially parallel to one another a width of the flow channels formed between adjacent fin members will be substantially consistent throughout. This provides for consistent heat flow throughout the flow channels and, accordingly, a homogeneous heat distribution about the cooking device. In a further preferred embodiment the cooking device is characterized in that said wall of said holder widens relative to said bottom, and in that said distal tip ends beneath the rim of said wall. Especially with such a sloping wall, the rim may reside beyond a point where the fin members end. Any overcooking boils, in that case, are particularly less likely to contaminate the fin member structure. Moreover, seen in a top view, the rim of such a sloping wall may entirely hide the fin member structure from sight. The cooking device, hence, may look no bulkier than any other cooking device lacking fins that would improve the thermal efficiency. The cooking device may have a sloping wall that diverges with respect to the bottom of the preparation space. With such an inclined wall, a particular embodiment of the cooking device according to the invention is characterized in that said wall portions of said fin members have a ridge extending opposite a base that approaches said wall in said direction from said bottom to said rim, and particularly extends substantially upright relative to said bottom. The wall portions may have a straight ridge that converges towards said wall as the wall widens. In a further preferred embodiment, the cooking device according to the invention is characterized in that at least a portion of said fin members comprise a bottom portion, contiguous with said wall portion, said bottom portion being connected to said bottom. These bottom portions protrude from the bottom and confine separate flow channels in between adjacent bottom portions. The flow channels between wall portions are particularly a continuous extension of these flow channels that are formed between bottom portions at the bottom of the cooking device. Like the wall portions, also these bottom portions provide additional contact area with the heat source and the hot gasses generated beneath the bottom. A specific embodiment of the cooking device according to the invention is characterized in that said fin members comprise mutually substantially identical first fin members and mutually substantially identical second fin members, alternating with said first fin members, wherein the bottom portions of said first fin members extend along said bottom over a first distance, and wherein the bottom portions of said second fin members extend along said bottom over a second distance, said second distance being smaller than said first distance. A gap between consecutive first fin members is filled this way at the bottom over part of its distance by a second fin member. This is particularly beneficial in a further embodiment of the cooking device according to the invention that is characterized in that the bottom portions extend radially in a direction from a central region of said bottom towards a periphery of said bottom. In that case the bottom portions will create an increasing gap as they reach the periphery of the bottom. By the interposition of a second or even further fin members within this greater gap, an optimal contact area with the hot gasses is preserved without deterioration a flow resistance. In that sense, especially cooking devices with a relatively large bottom may be characterized in that said fin members comprise mutually substantially identical further fin members, alternating with said first and second fin members, wherein the bottom portions of said further fin members extend along said bottom over a further distance, being in between said first distance and said second distance. In a further preferred embodiment the cooking device according to the invention is characterized in that said bottom portions are curved in a longitudinal direction, particularly flaring out from the central region of said bottom to its periphery. The curved shape of the bottom portions not only extends the contact area due to their greater length compared to straight fin portions, but moreover facilitates a stable placement on all kinds of stove grate configurations. Heat generated by a heat source underneath the central region can enter the channels freely that are formed in between the curved and particularly outward flaring bottom portions to be guided towards the periphery of the bottom. This promotes heat to be distributed over the entire bottom and allows the entire bottom to absorb heat. A still further preferred embodiment of the cooking device according to the invention is characterized in that said bottom portions have a curved base profile in a transverse direction, extending towards said bottom. This curved frontal profile in the lowermost section of the fin members leads to a aerodynamic favourable shape offering less flow resistance to the flow of hot gasses. In a further preferred embodiment, the cooking device according to the invention is characterized in that said fin members are integral with said bottom and said wall of said holder. Forming the fin member as an integral extension of the bottom or wall of the holder creates an optimal heat contact. Accordingly, the fin member portions may conduct any heat that was captured from the passing hot gasses efficiently to the bottom or wall of the preparation space. Furthermore, the integral fin members allow to be manufactured monolithically with the wall and / or bottom, for instance by casting, which is particularly favourable from a technical as well as economical point of view. Satisfactory results were achieved in practice with a specific embodiment of the cooking device according to the invention, characterized by fin members having bottom portions that define adjacent flow channels of between 5 and 35 millimetres deep. These channels confine the hot gasses and guide them to the periphery of the bottom where the gasses continue to flow in between the wall portions of the fins. In order not to exceed a too large flow resistance to the hot gasses and to allow the holder to be cast from a single material, a further specific embodiment of the cooking device according to the invention is characterized in that said fin members are a distance of at least 2 millimetres and at most 20 millimetres spaced apart. The amount of fin members may be determined accordingly such that, by being provided at a regular mutual pitch the inter-distance between adjacent fin members will be preserved all along the bottom to be at least this minimal spacing of 2 millimetres and no more than 20 millimetres. Alternatively the holder may be constructed out of a number distinct materials. In that respect a specific embodiment of the cooking device according to the invention is characterized in that said bottom comprises a base layer, providing an external surface of said bottom, and comprises a top layer, providing a cooking surface of said preparation space. The distinct materials of the cooking device may be united or bonded together by suitable manufacturing techniques, like casting, forging, welding or pressing. Particularly, said top layer of said bottom may be provided by a pan-shaped insert that is bonded to said holder in heat exchanging contact with said base layer and said wall of said holder. To promote said bonding process, the mating surfaces of said inlay and said holder may have underwent a surface preparations, such as texturing or undercuts. Particularly said external surface of said bottom as well as other outer heat absorbing surfaces of the cooking device may be textured, particularly by having a waviness or dimples, to induce turbulence and enhance heat transfer. Furthermore, at least part of the holder may be covered by a functional coating, such as a non-stick coating and / or anti-corrosion coating, to facilitate ease of cooking and cleaning as well as an extended lifespan over multiple use cycles. A further preferred embodiment of the cooking device according to the invention is characterized in that a closed jacket is provided surrounding at least said wall portions of said fin members. The jacket blankets the wall portions and thereby create duct in between wall portions. This prevents hot gasses, captured inside said ducts, from escaping prematurely, while exhaust openings are provided at the top of said jacket towards said rim to exhaust said gasses. However, forcing the gasses through these ducts, provides for an improved capture and absorption of heat and, accordingly, a more efficient use of energy consumed by the heat source. The jacket may be removable to aid cleaning. To prevent any boils, splatter or other contamination from entering any gap or joint between the jacked and the wall, a further preferred embodiment of the cooking device is characterized in that either said rim comprises an outward protruding edge portion that extends over said jacket and / or an upper portion of the jacket is all around sealingly connected to said wall. A preferred embodiment of the cooking device according to the invention is characterized in that any heat absorbing parts of said holder are made substantially uniformly from a heat resistant material, particularly from metal or ceramics, more particularly from one or more of aluminum, cast iron, steel, like titanium, steel, stainless steel or carbon steel, and copper. These heat resistant materials allow for the cooking device to be used with heat sources without potential damage to the fin members and / or jacket and moreover will conduct heat very well to the preparation space. A cooking device according to the invention may particularly provide a pressure cooker, saucepan, a frying pan, a pot, a wok, griddle or a casserole. Accordingly, a wide variety of food stuff or the like may conveniently be prepared with a cooking device according to the invention. To have a visual feedback while cooking concerning the temperature attained by the cooking device, a further particular embodiment of the cooking device according to the invention is characterized in that said holder is covered at least partly by a thermo-chromatic coating. Such thermo-chromatic coating has the ability of shifting from colour to thereby visually indicate a sense of the temperature of that part of the cooking device. With a view to a safe handling of the cooking device, a further specific embodiment of the cooking device according to the invention is characterized in that said holder comprises a handle, and in that a heat deflector lies interposed between said wall of said holder and said handle. The part of the cooking device, like a frying pan, that is attached to the handle may be shaped to deflect the flow of gasses away from the handle, which will significantly reduce the temperature of the handle and ensures a safer handling both during, as well as after cooking. Alternatively the heat deflector may comprise a separate heat screen. The invention will now be further elucidated on the basis of an exemplary embodiment and accompanying drawings. In the drawings: Figure 1 shows a bottom perspective view of a first embodiment of a cooking device according to the invention; Figure 1A shows a detailed view of the cooking device of figure 1; Figure 2 shows a front perspective view of the cooking device as shown in figure 1; Figure 3 shows a front perspective view of a second embodiment of a cooking device according to the invention; Figure 4 shows a bottom perspective view of the cooking device of figure 3; Figure 5 shows a front perspective view of a section of the cooking device of figures 3 and 4; Figure 6 shows a sectional side view of the cooking device of figures 3 to 4; Figure 6A is an enlarged view of a portion of figure 6; Figure 7 shows a detailed view of an underside of the cooking device of figures 3 to 6; Figure 7A is an enlarged view of a portion of figure 7; Figure 8 shows an exploded view of a third embodiment of the cooking device according to the invention; Figure 9 shows a perspective view to the bottom of the cooking device of figure 8; Figure 10 shows a frontal view of part of the bottom of the cooking device of figure 8; Figure 11 shows an exploded view of a fourth embodiment of the cooking device according to the invention; Figure 12 shows a perspective view to the bottom of the cooking device of figure 11; and Figure 13 shows a cross sectional view of the cooking device of figure 11; It is noted that the drawings are purely schematic and not drawn to scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are designated in the figures with the same reference numeral. With reference to figure 1, a cooking device is generally indicated by reference numeral 1. In this embodiment the cooking device 1 is a frying pan used on a heat source, in particular, a gas stove. However, in alternative embodiments it may also be a pot, a saucepan, a pressure cooker or a casserole. The cooking device 1 has a generally pan-shaped holder 2. The pan shaped holder 2 has a bottom 3 and a wall 4 surrounding the bottom 3. The bottom 3 is a generally flat area with the wall 4 extending substantially upright between the bottom 3 and an elevated rim 5. A preparation space 8 is provided between the bottom 3 and the wall 4 in which food stuff or the like can be prepared. The pan shaped holder 2 is manufactured from a heat conductive material, for example, stainless steel or copper. The preparation space 8 may be coated with a functional coating to make it food safe or non-stick. An outer surface of the holder 2 may be coated to make it easy to clean and to protect it from weathering. The coatings may be anodized aluminium, a ceramic coating or a polytetrafluoroethylene (PTFE or Teflon®) coating. To capture heat generated by the heat source the holder carries on an external surface thereof a set of mutually spaced fin members 71, 72. The fin members 71,72 are cast integral with the wall 4 and bottom 3 of the holder from a heat conducting material and are preferably less than 35 millimetres high. First fin members 71 each comprise a bottom portion that extends from a central region 30 along the bottom 3 toward a periphery 35 of the bottom. As shown in figure 1, these bottom portions are curved and flare radially outwards from the central region 30 of the bottom 3 towards the periphery 35. The first fin members 71 are substantially identical and, except from them extending radially, are mutually substantially parallel with one another. The first fin members 71 enclose mutually separated flow channels 7 between their bottom portions , which extend radially from the central region 30 towards the periphery 35 of the bottom 3. These flow channels 7 are substantially identical and guide heated gasses, that are generated primarily at the central region 30, towards the periphery 35. Along the wall 4 of the holder, the first fin members each comprise a wall portion. The wall portions extend from the periphery 35 of the bottom 3 towards the rim 5 and are substantially parallel to one another. In this embodiment the wall portions are straight. However, in alternative embodiments these wall portions may be curvy, in particular wavy, to increase a length thereof. As the first fin members flare out radially from the central region 30 towards the periphery of the bottom 3, their mutual space increases. In order not to exceed the distance between adjacent fin members to over 20 millimetres, the holder further carries a number of second fin members 72. Like the first fin members 71, also the second fin members 72 are formed integral with the wall 4 and the bottom 3 of the holder 2 and protrude less than 35 millimetres relative to the outside surface of the holder. As can be seen in figure 1, the second fin members 72 are placed midway in between first fin members 71 to reduce the gap of the flow channels 7 as they spread out towards the periphery. Everywhere it is observed that adjacent fin members 71,72 are a distance of between 2 and 20 millimetres spaced apart to provide an optimal heat exchange with the hot gasses flowing in between and to facilitate casting of the bottom in one piece. These second fin members 72 have only a small bottom portion, bridging the periphery of the bottom, and are primarily composed of a wall portion that is connected to the wall 4. These wall portions of the second fin members 72 alternate with the wall portions of the first fin members 71. In between them, these wall portions offer continuous extensions of the flow channels 7 that are initially formed in between the bottom portions of the first fin members 71, allowing heated gasses to continue to flow through the flow channels that are created this way in between the wall portions of both the first and second fin members 71,72. Also these extensions of the flow channels 7 are substantially identical to provide a homogenous heat distribution. As shown in figure 1, the wall portions of the first and second fin members 71,72 have a decreasing size as they extend along the wall 4 and approach the rim 5 of the wall. More specifically, as shown in figure 1, a distal tip of the wall portions ends substantially flush with the wall 4 of the holder 2. As shown in figure 2, the wall 4 widens relative to the bottom 3, whereas the distal tip of the wall portions ends below the rim. As a result, in a top view, the wall portions lie concealed within the inclined wall 4 of the holder 2 and leave hardly no exposed cross sectional area that could otherwise be contaminated by boils or spatters. A handle 11 extends from the holder 2. The handle 11 is an elongate body with a hook receiving opening towards an outer end thereof. The handle 11 is made from an isolating material. Handles of frying pans can get hot. To reduce this effect, a heat deflector 12 is added to the handle 11 to deflect hot flue gas away from the handle 11 in the presence of a heat source. Further the handle 11 and / or the holder 2 may be covered by a thermo-chromatic coating that visualizes a temperature of that part of the cooking device as a warning to the user. In use, the cooking device is placed on a burner of a gas stove. The central region 30 will be situated substantially centrally above the burner. Hot gasses heated by the burner are trapped in between fin members and initially flow radially outwardly through the flow channels 7 that are provided between the bottom portions of the fin members 71. The hot gasses are guided by these flow channels 7 towards the periphery where they split into sub-channels by the second or third fin members 72,73 to restrict their width to between 2 and 20 millimetres. The wall portions of the fin members continue to guide the hot gasses along the wall of the holder. As the heated gasses are guided through the flow channels, they may exchange heat with the fin members that will relay the absorbed heat to the holder by thermal conduction. In a second embodiment of the invention, as shown in figures 3 to 7, a jacket 6 surrounds the wall 4 particularly covering the wall portions of the fin members 71. The jacket 6 may be integral with the wall 4 or may be a separate part. The jacket 6 is manufactured from a heat resistance material. A lower end of the jacket 6 may extend beyond the periphery of the bottom 3, defining a collar covering an edge portion of the bottom 3. A number of exhaust openings 9 extend through an upper end region of the jacket 6. Each of the exhaust openings 9 corresponds to a flow channel 7 between adjacent wall portions of the fin members 71. In this embodiment the fin members are all straight, extending radially outward from a cental region 30 of the bottom. The jacket 6 particularly blankets the flow channels, whilst being spaced from the wall 4 by means of the wall portions of the fin members 71, as shown in figures 5 to 7. The fin members 71 maintain a gap between the wall 4 and the jacket 6 that tapers as the size of their wall portions diminishes. The holder 2, fin members 71 and jacket 6 may, in particular, be moulded from a heat resistant and heat conducting solid by means of investment casting. As shown in figure 6A, the rim 5 has an outward protruding edge portion 51 that extends over the jacket 6. The lower edge of the jacket 6 counteracts hot gasses from escaping from underneath the jacket 6. Finally, the gasses are allowed to exit the flow channels at the distal tips of the wall portions through the exhaust openings 9. A third embodiment of the cooking device according to the invention is shown in figure 8. The device comprises a pan-shaped holder consisting of a base member 21 of a first material and an inlay or insert 22 of a second material. The base member 21 may be manufactured for instance from cast iron, aluminium or titanium steel, whilst the inlay 22 may for instance be made from stainless steel and may carry a non-stick coating to provide a non-sticking cooking surface to the preparation space 4. Both parts are shown in exploded view and are joined together by press-fitting or another suitable boding technique. The base portion 21 has an attachment portion 23 for mounting a handle typical to a frying pan, like the handle 11 of figure 1. As shown in figure 9, this portion 23 of the base member is specifically shaped to provide a heat deflector that counteract thermal conduction between the holder 21 and the handle. The deflector 23 and the inlay 22 may both have holes which are aligned to mount the handle. Like in the preceding embodiments, a series of fin members is formed integrally with the base member 21. As shown in figures 9 and 10, these fin members 71 are curved and particularly flare entirely from a central region 30 of the bottom towards a periphery 35 of the bottom. From that periphery 35, each fin member has a wall portion that extends straight up along the wall 4 towards the rim 5 of the holder. These wall portions have a diminishing height as they approach the rim 5 and eventually vanish at their distal tip into the wall 4 to leave an entirely flush wall surface. Alternatively, also the wall portions of the fins might be curved. As particularly shown in figure 10, the fin members comprise a series of first fin members 71 that comprise a bottom portion flaring out radially from the central region 30 towards the periphery 35 where they continue into a wall portion of decreasing size along the wall 4. The fin members further comprise second fin members 72, like in both preceding embodiments, that are basically formed by a wall portion extending along the wall with only a minor bottom portion crossing the periphery of the bottom. In this embodiment of a larger bottom diameter, further fin members 73 are positioned in between the first and second fin members 71,72 to limit the mutual distance between adjacent fin members. The further fin members 73 each comprise a bottom portion shorter than that of the first fin members 71 and lie centred in between consecutive first and second fin members 71,72 or even further fin members as the diameter of the bottom increases. Like the first fin members 71 and second fin members 72, also the further fin members 73 are formed integral with the wall 4 and the bottom 3 of the holder 2 and protrude less than 35 millimetres away from the holder. Like the bottom portions of the first fin members 71, also those of the further fin members 73 are curved, flaring out radially towards the periphery 35 of the bottom 3. Like the other fin members 71,72, the further fin members 73 extend into a substantially straight wall portion along the wall 4 of the holder, alternating with the wall portions of the other fin members 71,72. Flow channels are formed in between the fin members 71,72,73 that guide the heated gasses over the bottom and wall of the holder and that allow improved heat exchange by means of the fin members 71,72,73. By placing these further fin members 73 in between second fin members 72, as shown in the enlarged view of figure 10, a mutual distance between adjacent fin members 71-73 is observed of everywhere between at least 2 millimetres and at most 20 millimetres by interposition of also these intermediate further fin members 73. This promotes the heat exchange between the hot gasses and the fin members and, moreover, facilitate easier manufacturing of the base member 21. A fourth embodiment is shown in figures 11-13. In this case the cooking device comprises a cooking pot 31 having first fin members 71 and second fin members 72, similar to those of the first embodiment. The cooking pot 31 is surrounded by a shell or jacket 32 that tightly fits the cooking pot 31 but remains removable therefrom. The shell 32 is formed from a heat conducting material, like a light metal such as aluminium. Heat isolated grip handles 43 are connected at opposite sides to the jacket 42 to facilitate handling of the cooking device. Figure 13 shows a cross section through the device, clearly demonstrating the diminishing width of the wall portion of the fin members 71 as they reach the rim of the holder 41. It is envisaged that the invention is desirable to use since the cooking device allows for optimal absorption of heat generated by from a heat source. Accordingly, less energy is required to achieve a result which results in energy saving. Using this cooking device cooking time will also be less. Furthermore, due to the cooking device absorbing a substantial amount of the generated heat instead of it entering space, an area surrounding the heat source will have a lower temperature. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. For example, the exhausts of the channels may be a slit between the rim and the jacket.

Claims

Claims: Cooking device (1), comprising a pan-shaped holder (2) having a bottom (3) surrounded by a wall (4), extending between said bottom (3) and an elevated rim (5) of said holder (2) to provide a preparation space (21), wherein said pan shaped holder carries a number of mutually spaced fin members at a side across from said preparation space, characterized in that said fin members each comprise a wall portion connected to said wall of said holder, said wall portion having a diminishing size in a direction from said bottom to said rim.

2. Cooking device according to claim 1, characterized in that said wall portion comprises a distal tip that ends substantially flush with said wall of said holder.

3. Cooking device according to claim 1 or 2, characterized in that said wall of said holder widens relative to said bottom, and in that said distal tip ends beneath the rim of said wall.

4. Cooking device according to claim 3, characterized in that said wall portions of said fin members have a ridge extending opposite a base that approaches said wall in said direction from said bottom to said rim, and particularly extends substantially upright relative to said bottom.

5. Cooking device according to any of the preceding claims, characterized in that said adjacent fin members extending substantially parallel to one another.

6. Cooking device according to any of the preceding claims, characterized in that said fin members each comprise a bottom portion, contiguous with said wall portion, said bottom portion being connected to said bottom.

7. Cooking device according to claim 6, characterized in that said fin members comprise mutually substantially identical first fin members and mutually substantially identical second fin members, alternating with said first fin members, wherein the bottomportions of said first fin members extend along said bottom over a first distance, and wherein the bottom portions of said second fin members extend along said bottom over a second distance, said second distance being smaller than said first distance.

8. Cooking device according to claim 7, characterized in that said fin members comprise mutually substantially identical further fin members, alternating with said first and second fin members, wherein the bottom portions of said further fin members extend along said bottom over a further distance, being in between said first distance and said second distance.

9. Cooking device according to claim 6, 7 or 8, characterized in that said bottom portions extend radially in a direction from a central region of said bottom towards a periphery of said bottom.

10. Cooking device according to claim 9, characterized in that said bottom portions are curved in a longitudinal direction, particularly flaring out from the central region of said bottom to a periphery of said bottom.

11. Cooking device according to claim 9 or 10, characterized in that said bottom portions have curved base profile in a transverse direction, extending towards said bottom.

12. Cooking device according to any one of the preceding claims, characterized in that said fin members are integral with said bottom and said wall of said holder.

13. Cooking device according to anyone of the preceding claims, characterized in that said fin members are a distance of at least 2 millimetres and at most 20 millimetres spaced apart.

14. Cooking device according to any one of claims 6 to 10, characterized in that said bottom portions of said fin members define an adjacent flow channel, having a depth of between 5 and 35 millimetres.

15. Cooking device according to any one of the preceding claims, characterized in that said bottom comprises a base layer, providing an external surface of said bottom, and comprises a top layer, providing a cooking surface of said preparation space.

16. Cooking device according to claim 15, characterized in that said top layer of said bottom is provided by a pan-shaped insert that is bonded to said holder in heat exchanging contact with said base layer and said wall of said holder.

17. Cooking device according to claim 15 or 16, characterized in that said external surface of said bottom is textured.

18. Cooking device according to any one of the preceding claims, characterized in that at least part of the holder is covered by a functional coating.

19. Cooking device according to anyone of the preceding claims, characterized in that a closed jacket (6) is provided surrounding at least said wall portions of said fin members.

20. Cooking device according to claim 19, characterized in that said rim (5) comprises an outward protruding edge portion (51) that extends over said jacket (6).

21. Cooking device according to claim 19 or 20, characterized in that any heat absorbing parts of said holder (2) are made substantially uniformly from a heat resistant material, particularly from metal or ceramics, more particularly from one or more of aluminum, cast iron, steel, like titanium steel, stainless steel or carbon steel, and copper.

22. Cooking device according to anyone of the preceding claims providing a pressure cooker, saucepan, a frying pan, a pot, a wok, griddle or a casserole.

23. Cooking device according to anyone of the preceding claims, characterized in that said holder is covered at least partly by a thermo-chromatic coating.

24. Cooking device according to anyone of the preceding claims, characterized in that said holder comprises a handle, and in that a heat deflector lies interposed between said wall of said holder and said handle.

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