WO1997035505A1

WO1997035505A1 - Food heating unit

Info

Publication number: WO1997035505A1
Application number: PCT/US1997/004531
Authority: WO
Inventors: William J. Hansen
Original assignee: Alto-Shaam, Inc.
Priority date: 1996-03-27
Filing date: 1997-03-14
Publication date: 1997-10-02
Also published as: AU2338197A

Abstract

A food warming and holding receptacle powered by a source of electrical energy comprises a well (12) supported on a planar surface, and at least one tray (28) containing food disposed in the well. The sheath (32) is fixed to a well and a one-piece, flattened, looped heating element (34) is slidably mounted in the sheath and connected with the source of electrical energy for conveying heat to the food in the tray.

Description

FOOD HEATING UNIT

Field of the Invention This invention relates broadly to food heating apparatus of the type employed in delicatessens and restaurants, and, more particularly, pertains to a food heating unit equipped with a heating element for maximizing heat transfer to the food.

Background of the Invention It has always been a concern for those in the food service industry to efficiently and safely maintain and control the heat supplied to food such as that served from an open warming well or a closed oven. One acceptable method for heating food resides in the use of a high temperature, tubular heating cable which is strung or wrapped repeatedly back and forth at regular intervals on a well or oven framework beneath a conductive metal surface. Such heating cable is typically comprised of a high resistance nichrome conductor, an insulation layer of mica tape, a wrap of teflon impregnated glass tape, a fiberglass braid for strength, and an outermost protective jacket. The heating cable is connected with suitable electrical thermostat controls and is connected to a source of electrical utility power so as to convert electrical energy into heat. Unfortunately, use of the tubular heating cable as described above poses a number of problems. One of the drawbacks exists in the labor intensive efforts required to manually string the cable. Another drawback is found in the serviceability of the cable which is difficult to access once installed. Perhaps the most critical problem lies in the inefficiency of the heating cable to provide uniform heat to the food in the trays or oven. Uneven high temperatures sometimes result in undesirable warping of the conductive metal surface.

Accordingly, it remains desirable to provide an improved food heating unit which offers a greater efficiency in heat distribution to certain zones with improved control therein. It is also desirable to provide an improved food warming and holding unit which is simple to assemble, and which utilizes common parts which are easy to service and/or replace. It remains further desirable to employ a heating element which will retain the stiffness of the conductive metal surface.

Summary of the Invention The present invention advantageously provides a food heating system employing an improved heating element which exhibits a marked increase in the amount of heat transfer. The heating element of the present invention provides a greater surface area per linear unit of length which reduces the power requirement previously demanded by the prior art tubular heating cable. In one aspect of the invention, a heating unit for supporting food therein comprises at least one wall, a sheath connected to the wall, and a flattened heating element disposed in the sheath for maximizing heat transfer to the wall. In the preferred embodiment, the wall defines a base of an open well and the sheath is a rigid, U-shaped member. The heating element is preferably positioned substantially parallel to the wall and is slidable into and out of the sheath. The heating element defines a heating zone in the wall and includes a pair of terminals projecting from the sheath.

In another aspect of the invention, a food warming and holding receptacle powered by a source of electrical energy comprises a well supported on a planar surface and at least one tray containing food disposed in the well. A sheath is fixed to the well, and a one-piece, flattened, looped heating element is slidably mounted in the sheath and connected with the source of electrical energy for conveying heat to the food in the tray.

In yet another aspect of the invention, a food heating apparatus connected to a source of electrical energy comprises a well including a base mounted on a planar surface. The base has an inner surface and an outer surface, the base having a plurality of spaced apart support brackets extending from the inner surface thereof. The apparatus includes a series of trays, each of which is suspended in the well above the inner surface by an adjacent pair of support brackets and defines an air space bounded by the inner surface, the adjacent pair of support brackets, and the tray. A multiplicity of sheaths is included, each of the sheaths being mounted to the outer surface between the adjacent pair of support brackets. A flattened, serpentine-shaped, rigid heating element is slidably mounted in each of the sheaths and lies substantially coextensive with the length and the width of each of the trays. The heating element has terminals connected to a source of electrical energy for superheating the air space and localizing heat transfer to the food in each of the trays. Still another aspect of the invention resides in a method of supplying a heating unit for supporting food therein. The method comprises the steps of providing at least one wall; connecting a sheath to the wall; and disposing a flattened, heating element in the sheath for maximizing heat transfer to the wall. Brief Description of the Drawings

The invention will become better understood by reference to the following detailed description of the preferred exemplary embodiment when read in conjunction with the appended drawing wherein like numerals denote like elements, and: Fig. 1 is perspective, top view of a food heating unit embodying the present invention;

Fig. 2 is a perspective, bottom view of the food heating unit of Fig. 1 illustrating a heating element incorporated therein;

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2; and Fig. 4 is cross-sectional, detail view taken on line 4-4 of Fig. 3.

Detailed Description of the Preferred Embodiment Referring now to the drawings, a food heating unit connectable to a source of electrical energy, such as an electrical utility, is generally identified by the numeral 10. In the preferred embodiment, food heating unit 10 is represented by an open top warming well 1 2 such as the type employed in a delicatessen or restaurant for warming and holding perishable food. Although not illustrated, it should be understood that the invention is equally applicable to one or more walls of an enclosed oven.

Well 12 includes a generally rectangular, stainless steel base 14 which has end walls 1 6 and sidewalls 1 8 and is mounted by a series of legs 20 upon a support surface. Base 14 has an inner, or upper, surface 22 as well as an outer, or lower, surface 24. A plurality of spaced apart support brackets 26 extend upwardly from the inner surface 22 and extend along the width of the well 1 2 for supporting an array of generally rectangular trays 28 containing food. Each of the trays 28 has flanges 30 from which the trays 28 are suspended in the well 1 2 above the inner surface 22 by adjacent pairs of the support brackets 26. In assembled form, an air space 31 is defined by the inner surface 22, an adjacent pair of support brackets 26, and a respective tray 28.

Mounted to the outer, or lower, surface 24 of the base 14 is a series of U-shaped sheaths 32 disposed between each adjacent pair of support brackets 26. Each of the sheaths 32 is of metallic construction and extends along the length and width of the superposed tray 28. As a salient feature of the invention, a flattened, serpentine- shaped, rigid heating element 34 is slidably mounted in each of the sheaths 32 and lies substantially coextensive with the length and width of respective tray 28. Each heating element 34 is a modular, continuous looped component formed with a series of four straight runs 36 interconnected with three bends 38 and extends substantially parallel to the base 14 and the bottom of the tray 28. Heating element 34 is preferably comprised of a cluster of nickel-chromium resistant wires insulated by a layer of magnesium oxide. Such heating element 34 is commercially available from the Watlow Company of St. Louis, Missouri and is sold under the FIREBAR^® trademark. In order to supply the heating unit 1 0 with a source of electrical energy, heating element 34 is provided with a pair of spaced terminals 40 which protrude from the sheath 32 when the heating element 34 is slidably mounted therein. Heating element 34 is particularly attractive in offering a flattened surface geometry which superheats the air space 31 beneath and around the sides of the tray 28 and maximizes the amount of heat transferred to the base 14. For example, while a prior art tubular heating cable may transfer heat over a width of .03", the heating element 34 of the present invention is able to transfer heat over a much larger width of .52" for a singular run 36 such as depicted in Fig. 4. Heating element 34 defines a specific zone for each tray 28 in which more power is available per unit length owing to its flattened configuration. Also, because of the protected nature of the heating element 34, it is convenient to locate a temperature sensor adjacent thereto which will provide accurate temperature feed back. In order to ensure that heat energy is directed to the base 14, each sheath 32 is surrounded typically by a 1 -1 Va " layer of insulation 42 which is held in place by a retaining jacket 44.

It should be appreciated that the present invention provides a food heating unit in which the efficiency of heat transfer is vastly improved. Use of the heating element not only simplifies assembly and makes maintenance easier, but provides a modularity which enables quick expansion or reduction of the food heating unit. It also has been found that because the heating element provides a more even transfer of heat, there is a noticeable improvement in well stiffness. Likewise, there is an improved zone control of temperatures. Because of the isolated heating element, each of the warming chambers underlying the trays is easily cleaned. Unlike the prior art, the protected heating element, when exposed to salts and moisture, exhibits low current leakage. While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention set forth with following claims.

Claims

i claim:

1 . A heating unit for supporting food therein comprising: at least one wall; a sheath connected to said wall; and a flattened heating element disposed in said sheath for maximizing heat transfer to said wall.

2. The heating unit of claim 1 , wherein said wall defines the base of an open well.

3. The heating unit of claim 1 wherein said sheath is a rigid, U- shaped member.

4. The heating unit of claim 1 , wherein said heating element is positioned substantially parallel to said wall.

5. The heating unit of claim 1 , wherein said heating element is slidable into and out of said sheath.

6. The heating unit of claim 1 , wherein said heating element defines a heating zone in said wall.

7. The heating unit of claim 1 , wherein said heating element includes a pair of terminals projecting from said sheath.

8. A food warming and holding receptacle powered by a source of electrical energy, the receptacle comprising: a well supported on a planar surface; at least one tray containing food disposed in said well; a sheath fixed to said well; and a one-piece, flattened, looped heating element slidably mounted in said sheath and connected with said source of electric energy for conveying heat to the food in said tray.

9. The food warming and holding receptacle of claim 8, wherein said heating element is a continuous member having a pair of terminals connectable with said source of electrical energy.

10. A food heating apparatus connected to a source of electrical energy, the apparatus comprising: a well including a base mounted on a planar surface, said base having an inner surface and an outer surface, said base having a plurality of spaced apart support brackets extending from said inner surface thereof; a series of trays containing food, each of said trays being suspended in said well above said inner surface by an adjacent pair of said support brackets and defining an air space bounded by said inner surface, said adjacent pair of support brackets, and said tray; a multiplicity of sheaths, each of said sheaths being mounted to said outer surface between said adjacent pair of support brackets; and a flattened, serpentine-shaped, rigid heating element slidably mounted in each of said sheaths and lying substantially coextensive with the length and the width of each of said trays, said heating element having terminals connected to a source of electrical energy for superheating said air space and localizing heat transfer to the food in each of said trays.

1 1 . The food heating apparatus of claim 10, wherein each of said heating elements is a continuous member having four runs, each adjacent pair of runs being interconnected by a bend.

12. A method of supplying a heating unit for supporting food therein, said method comprising the steps of: providing at least one wall; connecting a sheath to said wall; and disposing a flattened, heating element in said sheath for maximizing heat transfer to said wall.