US 3626922 A
Description (OCR text may contain errors)
United States Patent Inventor Donald Richard Borge London, England Appl. No. 7,684 Filed Feb. 2, 1970 Patented Dec. 14, 1971 Assignee The Gas Council London, England Priority Jan. 31, 1969 Great Britain 5,403/69 FORCED CONVECTION OVEN 3 Claims, 2 Drawing Figs.
US. Cl 126/21 A Int. Cl F24c 15/32 Field olSearch 126/19, 21, 21 A, 39 C, 273
 References Cited UNlTED STATES PATENTS 2,524,272 10/1950 Sage 126/21 A UX 2,817,506 12/1957 Albright 126/21 A UX 3,384,068 5/1968 Perry et a1. 126/21 A 3,411,493 11/1968 Everson et a1. 126/21 A 3,463,138 8/1969 Lotter et a1. 126/21 A Primary Examiner-Charles J. Myhre AnorneyLarson and Taylor ABSTRACT: A gas fired forced convection oven comprises a heating or cooking zone, fan means for circulating a hot gaseous atmosphere in said zone, the gas distribution means including at least one fuel gas burner located in a passage lead ing to said zone, a throat located in the passage downstream of said burner and means for deflecting the circulating atmospheric gas issuing from said fan away from said burner and into said throat whereby the circulating atmospheric gas mixes with the combustion gases from the burner and enters the said heating or cooking zone.
FORCED CONVECTION OVEN BACKGROUND OF THE INVENTION This invention relates to forced convection ovens and is particularly concerned with gas fired ovens of this type. Such ovens are conventionally used to heat a number of separate containers or portions of precooked foods but the ovens may also be used for normal cooking purposes if required. A desirable characteristic of this form of oven is uniform heating throughout the oven space and such uniformity is obtained by controlling the temperature, quantity and flow patterns of the circulating medium.
In the present forms of gas heated convection oven the circulating medium is generally air heated indirectly by some form of heat exchanging system, the combustion products from the gas burners being vented to atmosphere. This arrangement tends towards operating inefficiency and adds considerably to the manufacturing and running costs.
It is therefore an object of the present invention to provide an improved form of gas fired forced convection oven in which the aforementioned disadvantages are minimized.
SUMMARY OF THE INVENTION According to the invention a forced convection oven comprises a heating or cooking zone, fan means for circulating a hot gaseous medium in said zone, the gaseous medium distribution means including at least one fuel gas burner located in a passage leading to said zone, a pressure reducing throat located in the passage downstream of said burner and means for deflecting the circulating gaseous medium issuing from said fan away from said burner and into said throat whereby the circulating medium mixes with the combustion gases from the burner and enters the said heating or cooking zones.
in a preferred arrangement the circulating medium enters the heating or cooking zone through apertured side panels flowing substantially horizontally across the cooking zone and leaves via an apertured rear panel. The fan may be located in a compartment positioned below the heating or cooking zone.
To enable the nature of the invention to be more readily understood, one embodiment of the invention will now be described, solely by way of example, with reference to the accompanying drawing, which shows diagrammatically a preferred form of oven. In the drawing:
BRIEF DESCRIPTION OF THE DRAWING FIG. I is a midsectional side view of the oven and FIG. 2 is a midsectional view looking from the front of the oven.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing a forced convection gas fired oven comprises a heating or cooking zone 1 having perforated side plates 2 through which a hot gaseous medium comprising a mixture of air and combustion products from the fuel burners used to heat the oven, is supplied by means of a fan 3. The fan is located in a distribution chamber 4 positioned below the heating or cooking space and circulates the gaseous medium to the side plates via a supply duct 5 at each side of the oven.
The side plate apertures 6 are arranged and dimensioned to provide a substantially uniform flow of gas across the heating or cooking zone and the gas is withdrawn from the oven zone through an apertured back plate 10 and returned to the distribution chamber and fan via an extract duct 7. The fan is driven by an electric motor 8.
The oven is heated by fuel gas burners 9 positioned at each side of the appliance, the burner ports in each case being arranged to fire directly upwards into a lower extension of the supply duct 5. A pressure reducing throat I1 is fonned at the lower end of each duct 5 and deflector or baffle plates 12, associated with the distribution chamber 4, are arranged to shield the burners and direct the gaseous medium circulated by the fan 3 into the throat where the circulating gaseous medium mixes thoroughly with the combustion gases from each burner.
It will be appreciated that the pressure reducing throat is shaped as a venturi or orifice tube to cause a sharp rise in the velocity of the circulating medium which together with an associated drop in the static pressure within the throat enables the combustion products to enter the side ducts 5 without down draughts efi'ecting the burner or burners situated below the deflector plate 12.
The oven is provided with a vent or flue (not shown) connecting with the extract duct 7 at a point where the internal pressure is only slightly positive in relation to atmospheric pressure, such that natural aspiration prevents a build up of excess combustion products within the oven.
During comparative tests it was shown that this form of direct fired forced convection oven provides a considerable advantage in both efficiency and thermal response times over the conventional and previously known forms of oven.
1. A forced convection oven comprising an openable chamber defining a cooking zone; fan means located in a compartment positioned below the cooking zone; inlet and outlet passageways between said compartment and the cooking zone for circulating a gaseous medium through said zone; gas fuel burners positioned at each side of the oven for heating the gaseous medium; said burners including ports arranged to fire directly upwards into the inlet passageways leading to the oven cooking zone; a pressure reducing throat within each inlet passageway and a deflector plate in each inlet passageway for shielding the burners and directing the gaseous medium circulated by the fan into the throat so that the circulating gaseous medium mixes with the combustion gases from each burner before passing into the cooking zone.
2. A forced convection oven according to claim 1 wherein the gaseous circulating medium comprises a mixture of air and combustion products from the fuel burner.
3. A forced convection oven according to claim 2 wherein the openable chamber includes top, bottom, back and side walls, said side walls including apertured panels therein and said back wall including an apertured panel therein, said oven further comprising means for directing the circulating medium into the cooking zone through the apertured panels in the side walls of the chamber so that, in operation, the medium flows substantially horizontally across the cooking zone and exits through the apertured panel in the back wall of the chamber.
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