WO2003011092A1

WO2003011092A1 - Fryer or boiler pan with accelerated convective movements

Info

Publication number: WO2003011092A1
Application number: PCT/IT2002/000023
Authority: WO
Inventors: Angelo Mora
Original assignee: Elframo S.R.L.
Priority date: 2001-07-27
Filing date: 2002-01-16
Publication date: 2003-02-13
Also published as: ITBG20010024A1

Abstract

This pan for fryers and boilers has the feature of comprising, for containing the cooking liquid, a rounded base provided with a large heat transfer surface, and internally comprising lateral partitions (8A, 8B) arranged to cooperate with the heated walls of the pan to create channels (10A, 10B) for conveying convective movements intensified by a progressive heating of the cooking liquid along a rising path, said movements producing a rapid circulation favouring heat transfer between the pan and the cooking liquid, and a reduction in the time required for cooking.

Description

DESCRIPTION

FRYER OR BOILER PAN WITH ACCELERATED CONVECTIVE

MOVEMENTS

TECHNICAL FIELD This invention relates to a fryer or boiler pan with accelerated convective movements. BACKGROUND ART

The frying or cooking of the large quantities of food (potatoes, courgettes, fish, tagliatelle, pasta, rice, etc.) required by restaurants, snack bars or fast food outlets is accomplished by suitable fryers or boilers. These fryers or boilers are able to heat large quantities of the cooking liquid very rapidly. In this respect they consist of a pan lapped externally by large fierce flames generally produced by suitable gas burners and able to rapidly heat the quantity of liquid contained in them to frying temperature. In this regard, it should be noted that the said cooking takes place by immersing into the boiling liquid (water, oil) contained in the pan a basket containing a considerable mass of food to be cooked; as it is at ambient temperature (or even at a temperature below zero) its immersion creates a sudden cooling of the liquid. This means that the liquid cooled in this manner must be immediately supplied with the heat necessary to return it to the required boiling or frying temperature. A problem related to these operational requirements is that the heat generated by the flames is unable to pass to the oil in a satisfactory manner. In this respect, the heat transfer follows relationships which, although conceptually well known, are materially limited in their industrial application. For example, although it is known that the quantity of heat that can pass through a wall is proportional to the so-called "heat transfer surface". The known means for increasing this heat transfer surface (such as fins, corrugations in the sheet metal, etc.) have proved unsatisfactory in terms of efficiency for the production costs involved. The intrinsic behaviour of metals on prejudicial direct exposure to the flames must also be considered, together with the contamination by metal salts or ions which could derive from direct contact of the food with such cooking pans when constructed of metals of high thermal conductivity. Another relationship states that the quantity of heat transferred between a wall and a fluid is proportional to the fluid transit velocity. Considering in this sense the heat transfer between the hot pan wall and the colder liquid, the said "transit velocity" is that deriving from convective movements, generated by the reduction in specific gravity caused by the temperature increase in one region compared with the greater specific gravity present in other regions external thereto within the mass of cooking liquid. These convective movements are of chaotic and tumultuous type, so that their potentiality for rising becomes dispersed within the circulatory disorder which normally occurs in a heated liquid mass. In traditional boilers and fryers, the heating means generally used are the flames generated by suitable gas burners: this is known to give rise to a series of problems, such as the danger of explosion and the need to convey the off-gases to the flue. An object of the present invention is to define a pan for fryers and boilers which is suitable for use with other heating means, such as high frequency electromagnetic induction or heating by blown hot air. Another object is to define a pan for fryers and boilers, which has a particularly large external heat transfer surface. Another object is to define a pan with a flame-lapped external surface receiving the heat source, as aforestated, which has a long operational life. Another object is to define a pan, as aforestated, having an internal configuration which increases the velocity of convective movements. Another object is to define a pan, as aforestated, which results in large- trajectory convective movements such as to achieve a more constant temperature of the liquid mass in contact with the food to be cooked. DISCLOSURE OF THE INVENTION

These and further objects will be seen to have been attained on reading the ensuing detailed description of a fryer or boiler pan having the characteristics defined in claim 1. BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of non-limiting example in the accompanying drawings, in which:

Figure 1 is a section through a fryer or boiler of a size determined by a basket for containing food to be cooked; Figure 2 is a top view of a lateral-walled structure resting within a pan for containing the cooking liquid.

BEST MODE FOR CARRYING OUT THE INVENTION With reference to the aforesaid Figure 1 , a fryer or boiler 1 comprises a pan 2 with an internal surface 2A and an external surface 2B, for containing oil or water 3 to a minimum level 4A and a maximum level 4B. On the external surface of this pan there are welded a plurality of solid columnar bodies 5 in a number and of dimensions substantially expressed by Figures 1 and 2. These columnar bodies and the external surface of the pan 2 are shown as hypothetically struck by typical flames produced by usual gas burners 7. Said burners 7 have an elongate structure and are positioned below the left side S and right side D of the pan 2. As the fryer or boiler possesses a flue positioned in a rear region P, the hypothetical flames present in the regions S and D tend to converge rearwards. For this reason the pan 2 possesses columnar bodies 5A only in said rear region P, and not in the opposite front region. As the columnar bodies are welded to the constituent sheet metal of the pan 2, they transfer thereto the flame heat absorbed by them. This is because the pan 2, being filled with oil or water at frying or boiling temperature, is at a much lower temperature than that of the flame. These columnar bodies are consequently to be considered as integral with the pan, and in this manner provide an outer surface thereof which is extremely large. This results in extremely easy heat transfer enabling large quantities of heat to be transferred to the cooking liquid in a very short time. The heavy structure and the projection-welding of the columnar bodies 5 means that high resistance is offered to the typical physical-chemical phenomena created by the flames, resulting in a long pan life, notwithstanding its greater capacity to absorb heat. The considerable metal mass of these columnar bodies is also advantageous for heating by electrical induction. As the interior of the pan 2 is filled with cooking liquid, the pan walls heat the liquid molecules in contact with it, these latter consequently undergoing a reduction in their specific gravity. This causes them to float on the liquid molecules of lower temperature, to result in chaotic upward movements determining convective circulation extending to the entire inner volume of the pan. Said typical convective circulation is prevented by the pan of the invention, because it comprises lateral partitions 8A, 8B which deviate the upward movements (indicated by short black arrows) in accordance with the obliqueness of the said lateral partitions. Orderly upward currents 11A, 11B receiving the upward vertical components of all the movements of the oblique fluid threads consequently arise within interspaces 10A, 10B existing between the inner surface of the pan 2 and the facing partition. Said rising currents 11 A, 11 B are consequently very rapid. This means that as there is no discontinuity in the liquid mass being heated, the entire flow transiting through the interspaces 10A, 10B is continuously replaced by an equal flow of liquid drawn from pan regions at lower temperature. This "less hot" liquid also receives the said large quantity of heat transmitted by its contact with the pan walls associated with columnar bodies, and hence receives thrusts which integrate it with the said upward currents 11 A, 11B. These currents then pass through a perforated basket 2 (represented by its outline), to transfer a quantity of their heat to food pieces 13 to be cooked, then descend downwards in circulatory directions 14. This descent is due to the increase in the specific gravity of the relatively cooled liquid. In this manner two concurrent circulatory currents arise (one to the right and the other to the left) which by virtue to their high velocity, transfer a considerable quantity of heart to the food pieces 13 to be cooked. The food is hence cooked in a shorter time. From the aforegoing it will be apparent that the said circulation is facilitated by paths which reduce hydrodynamic resistance, i.e. by a pan 2 which presents rounded shapes of the type illustrated. The said lateral partitions 8A, 8B can be fixed to the pan 2 in various ways. A preferred method is however to combine them into a removable structure which rests on the interior of the pan 2. Said removable structure is shown in top view in Figure 2 (in which the basket 12 is not shown). Said structure comprises two robust rectilinear rods 15A, 15B welded to two profiled rods 16A, 16B. The profiling of these latter rods comprises bending in an oblique plane to define, along each of these, three points of contact with the pan interior. More specifically, they comprise short bends at their ends to define central points of base contact 17A, 17B and lateral contact points 18A, 18B, 19A, 19B. These rods present points of geometrical contact with the two lateral partitions 8A and 8B, at which welds are made in known manner; holes or apertures are specifically required to enable the ends to project in order to define the points of contact 18 A, 18B, 19 A, 19B. The upper edge of the partitions comprises one or more lugs 20A, 20B, 20C, 20D bent outwards to skim the lateral vertical walls of the pan. These lugs serve as a guide for "centered" insertion of the basket 12 into the pan 2, until it rests on the transverse rods 15A, 15B of the removable structure. These lugs also serve to maintain a constant distance between the partitions 8A and 8B and the inner walls of the pan 2, in order to ensure the presence of the interspaces 10A, 10B for transit of the convective movements 11A, 11B.

Claims

1) A fryer or boiler pan to be disposed in a position corresponding with burners (7) generating flames (6) or other heat sources arranged to heat said pan, this latter having an internal surface (2A) and an external surface (2B) and containing cooking liquid (3), characterised by comprising a plurality of bodies (5) projecting from the external surface (2B) in order to form a large heat transfer surface, and internally comprising conveying means (8A, 8B) arranged to cooperate with the heated walls of the pan to create interspaces (10A, 10B) for conveying (11 A, 11V) convective movements (9) intensified by a progressive heating of the cooking liquid along a rising path, said movements producing a rapid circulation favouring heat transfer between the pan and the cooking liquid, and a reduction in the time required for cooking.

2) A pan as claimed in claim 1 , characterised in that the projecting bodies are columnar bodies.

3) A pan as claimed in claim 1 , characterised in that the conveying means are flat partitions (8A, 8B).

4) A pan as claimed in claim 3, characterised in that the flat partitions (8A, 8B) are located in positions corresponding with lateral walls of the pan. 5) A pan as claimed in claim 4, characterised in that the lateral partitions (8A, 8B) are inclined towards the lateral walls of the pan. 6) A pan as claimed in claim 3, characterised in that the lateral partitions (8A, 8B) are integrated into a removable structure resting on the inside of the pan (2). 7) A pan as claimed in claim 6, characterised in that the removable structure comprises transverse rods (15A, 15B) for supporting the basket.

8) A pan as claimed in claim 6, characterised in that the removable structure comprises rods (16A, 16B) profiled to each form three points (17A, 18A, 19A; 17B, 18B, 19B) for their resting in the interior of the pan.

9) A pan as claimed in claim 3, characterised in that the lateral partitions (8A, 8B) comprise, along their upper edges, lugs (20A, 20B, 20C, 20D) provided as a guide for the centered insertion of a basket (12) into the pan (2). 10) A pan as claimed in claim 9, characterised in that the lugs (20A, 20B, 20C, 20D) prevent any approach between the partitions (8A, 8B) and the pan walls, in order to maintain a distance therebetween and hence form interspaces (10A, 10B) for the transit of rising convective movements (11 A, 11B). 11) A pan as claimed in the preceding claims, characterised by a structure suitable for its heating by known electrical induction using alternating current.