|Publication number||US20060180137 A1|
|Application number||US 10/541,138|
|Publication date||Aug 17, 2006|
|Filing date||Feb 18, 2004|
|Priority date||Feb 18, 2003|
|Also published as||WO2004074743A1|
|Publication number||10541138, 541138, PCT/2004/192, PCT/AU/2004/000192, PCT/AU/2004/00192, PCT/AU/4/000192, PCT/AU/4/00192, PCT/AU2004/000192, PCT/AU2004/00192, PCT/AU2004000192, PCT/AU200400192, PCT/AU4/000192, PCT/AU4/00192, PCT/AU4000192, PCT/AU400192, US 2006/0180137 A1, US 2006/180137 A1, US 20060180137 A1, US 20060180137A1, US 2006180137 A1, US 2006180137A1, US-A1-20060180137, US-A1-2006180137, US2006/0180137A1, US2006/180137A1, US20060180137 A1, US20060180137A1, US2006180137 A1, US2006180137A1|
|Original Assignee||Malolo Pty. Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (4), Classifications (9), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to cooking surfaces on which meat or other pieces of food can be cooked. Although the invention will primarily be described in relation to its application to an outdoor barbeque it can equally be used in domestic and commercial kitchens or anywhere a surface for cooking of food is required.
Traditional cooking surfaces take the form of a hot plate or spaced grill bars of various types. Both hot plates (griddles) and conventional grill bar arrangements primarily cook food by either radiant or conducted heat or a combination of both. In the case of grill bars some form of heat distribution is usually employed between the heat source, usually a gas flame and the grill bars. These may take the form of rocks, metal plates, angled bars and the like, all designed to radiate the heat more evenly at the cooking surface. The heat transmitted to traditional grill bar surfaces is thus a combination of some air heated by the burners that circulates upwardly through the grill bars and radiant heat transmitted from the rocks, metal plates, angled bars and the like. In most cases the radiant heat and some conducted heat from the grill bars themselves perform the majority of the cooking of food on the grill bar surface.
There are a number of disadvantages associated with conventional grill bar cooking surfaces. Firstly, the conducted and radiant heat dominated cooking process tends to dry the foods being cooked. Additionally, it is very difficult to regulate the temperature of the cooking surface of conventional grill bars because of the radiant heat transfer mechanism below. Consequently the grill bars are frequently heated to a point where they will burn or char meat rather than browning it, producing an acrid or burnt taste to the food. Another difficulty is that any fat heated during the cooking process melts and drips through the grill bars and on to the radiating heat source below. These surfaces are heated to an even higher temperature than the grill bars and consequently flare-ups and fat fires frequently result.
It is an object of this invention to provide a cooking surface which will overcome, or at least ameliorate one or more of the foregoing difficulties.
According to one aspect of this invention there is provided a cooking surface defined by an upperside of a series of parallel closely spaced bars and a corresponding series of burners extending respectively along and adjacent an underside of each bar so that melted fats or other material falling from or between the bars fall past a combustion zone around the burners and food on the surface is shielded from the radiant heat of the burners.
In one form of the invention the bars have a substantially flat underside. In another form of the invention the bars have a concave underside. The concave underside can be smoothly curved or formed by protruding edges for example. By suitably dimensioning the bars and burners and placing the bars adjacent and above the burners, the combustion zone around the burners is under and shielded by the bars so that any melted fat or other material falling between the bars does not fall into the combustion zone. Additionally, there is no radiant heat from the burners delivered to the cooking surface.
Preferably, the ratio of the area of the bars forming the cooking surface to the spaces between the bars is about 2.5:1.
The burners are preferably positioned and configured so that the gas flame has the outer mantle just reaching the underside of the corresponding bar. In this way the heat source is as close as possible to the grill bar without the position of the grill bar resulting in incomplete combustion of gas because of restricted flow of the secondary combustion air. The burners are preferably supplied with gas from a manifold extending adjacent one edge of the cooking surface. Preferably an even heat distribution along the burner length is achieved by increasing the size of the gas ports slightly in the direction away from the supply manifold. This has been found to be an effective way to compensate for gas flow friction in the burner which would otherwise reduce heat output towards the remote end of the burner.
The burners are preferably formed with an oval shaped cross section and the elongated dimension of the oval is arranged vertically. This configuration has reduced gas friction compared to a circular burner and also allows a greater cross section area for a given width so that the burner can be shielded by a relatively narrower grill bar.
The grill bars are also preferably sloped upwardly away from the manifold by a small amount so as to provide a flue for the gas burner and ensure complete combustion. Preferably the burners have a slope of about 1%.
The configuration of the grill bars and burners of this invention allows very precise control of the temperature of the grill bars. Preferably the temperature of the grill bars is controlled to between 2800 and 295° C. This enables one to cook at the highest temperature possible to achieve optimum cooking results while reducing the risk of flare-ups and fat fires. This temperature is the point just prior to the flash-point of fat (around 300° C.) when it mingles with meat juices.
In one form of the invention a temperature sensor can be provided to provide an input to a feedback gas control to maintain the grill bar temperature at a selected level.
The grill bars are preferably convex on the upper surface. In one form of the invention, the grill bars can be curved or formed by a central flat section with downwardly angled flanges along the longitudinal sides. In the one form of the invention the grill bars are stamped from thin gauge metal. The thin gauge metal has the advantage of heating and cooling relatively quickly. In another form of the invention the grill bars can be formed from cast iron or any other suitable material.
The gas burners are preferably arranged in a series of discrete banks including a selected number of burners. Each of the banks has its own subsidiary manifold with its own gas cock. Each gas cock is supplied from a primary manifold which is in turn under the control of a single regulator valve. This allows the temperature of regions of the cooking surface to be readily controlled.
It will be apparent the cooking surface of the present invention results in the majority of the cooking at the surface being done by convection rather than radiant and conducted heat. The increase in convective heat ensures that the food retains its juice and enhances its flavour. The convection heat does not seal the outside of the meat as much as radiant and conducted heat and the heat permeates the food more evenly maintaining higher moisture level. Additionally, because each grill bar provides a shield to the burner any fat that melts during the cooking process drips downwardly between the burners. That is, the fat does not come in contact with the burner or any heat source heated to above the flash point of the fat. This virtually eliminates all fat fires during the cooking process. A large amount of the convection heat is provided by a hot air flow from the region around the burner moving upwardly through the gap between the grill bars. The amount of air that passes through the grill bars and hence the temperature of that air is largely determined by the amount of air admitted to a region below the burners. By providing a suitable housing extending from adjacent the edges of the cooking surface and downwardly underneath the burners, airflow can be regulated through desired apertures provided to optimise the convectional airflow.
The invention also provides a facility for the roasting of foods. Because the cooking surface of this invention provides an effective way in which a convectional airflow of air can be generated it provides an excellent means of heating an oven like space. By placing a suitable hood over the cooking surface, the interior is effectively and evenly heated to roasting temperatures. It will be appreciated that a vent is suitably positioned in the hood or enclosure so as to provide a continual flow of air. The operation of the cooking surface as part of an oven is found to be significantly enhanced by the use of an angled baffle which is positioned over the central burners below the cooking surface. The baffle extends outwardly and upwardly from the central region the food to be roasted is supported on the adjacent portion of the grill bars. The burners in the zone immediately under the baffle are not utilised and the heating takes place indirectly by a convectional flow of air from the banks of burners at the remote edges of the cooking surface. The baffle is also configured so as to drain any fat produced in the roasting process to the center of the baffle which can be provided with an aperture to direct the flow through one of the gaps between the burners.
Preferably the grill bars used in the barbeque are mounted so as to allow for thermal expansion without warping. In one preferred form of the invention the grill bars are mounted by lower edges engaging tracks formed in transversely extending mounting rails. This form of the invention also allows the ready replacement of one or more grill bars. This is particularly useful where the grill bars are treated with a non-stick coating that ultimately may wear or be damaged through misuse.
In another aspect of the invention there is provided a vented barbeque hood assembly including a hood to cover at least part of a cooking surface and enclose a cooking region, a vent opening in said hood to provide a passageway for egress from the cooking region, and a manually operated baffle cooperating with said vent opening and selectively operable to move between an open position in which egress from the cooking region is permitted and a closed position in which egress is substantially prevented.
Preferably, the baffle is formed by a part cylindrical member rotatable about its axis to move between the closed and open positions.
In a preferred form of the invention the opening extends along substantially all of a rear edge of the hood.
Preferably, the cylindrical baffle is mounted on an axle and a handle is connected for rotation of the axle to move the baffle between the open and closed positions.
In the open position the baffle allows egress of hot air and cooking vapours from the cooking region and cooking can be performed in a barbeque like manner. When the baffle is in the closed position egress of hot air is prevented and the cooking regions forms an oven like space. The oven like space can be used for roasting. Preferably, the baffle can be moved to selectively control the amount of egress from the cooking surface and thus the temperature within the cooking region.
One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.
Gas is supplied to the burners 26 via a manifold assembly 30. Manifold 30 is connected to a gas supply line 32 that provides liquefied petroleum gas (LPG) from a conventional cylinder and regulator arrangement (not shown). The LPG is regulated to a pressure of approximately 2.75 kpa by a standard regulator arrangement. It will be apparent that other gas types, such as natural gas, may be used with the corresponding modifications to the burners 26. A cross over tube 34 extends across the burners 26 to provide for ease of lighting. The cross over tube 34 is supplied with gas from gas supply 32 via a line 36.
The distance between the burners 26 and grill bars 22 is an important parameter. In the preferred form of the invention the distance is adjusted to provide an optimum balance between heating of the grill bars and production of the convection flow of hot air whilst still protecting the food on the cooking surface from direct radiant heat and at the same time protecting the burner from any material falling through gap 28. In practice it has been found that in the preferred form of the invention the burner should be placed as near as possible to the grill bar whilst still allowing substantially complete combustion of the gas from burner 26. This distance varies according to the burner design and precise shape of the grill bar but substantially corresponds to positioning of the burner so that the top of the outer mantle 40 of the gas flame just reaches the grill bar 22.
It will be apparent to those skilled in the art that the positioning of the burner 26 in this way will ensure an adequate supply of secondary air from the region around the flame to ensure complete or substantially complete combustion.
The grill bars 22 can be formed from any suitable material. In a preferred form of the invention they are formed from a pressed thin gauge mild steel. The mild steel grill bars are economical to produce and because they are thin gauge they heat and cool relatively quickly in response to the amount of heat supplied by the burner 26.
As is shown from the schematic cross sections of
The barbeque 12 of the preferred embodiment is preferably operated so that the grill bars 22 are heated to between 280° and 295° C. This has been found to produce very good cooking results with a variety of meats. In particular chops and steaks have been found to be particularly evenly cooked and have a high level of moisture retention. During the cooking process flare-ups and fat fires are almost entirely eliminated. As a consequence the cooking process becomes extremely simple. Unlike other forms of open grill the absence of any fat flare ups means that the meat can simply be placed on the grill for a desired time period, and only need to be turned once during the cooking period. This means that the level of skill required to effectively cook on an open grill is limited to a simple timing operation. This advantage of the invention leads to considerable opportunities for use in commercial kitchens with a cost saving on expensive skilled chef time.
Another significant advantage of the present invention is the radiant heat produced at the cooking surface is almost entirely eliminated. This means that the area above the cooking surface is not subject to radiant heat and thus less discomfort is produced when reaching across the cooking surface for example to turn food at the rear of the cooking surface.
The conditions for each of the thermograph measurements were as follows:
It will be apparent from the thermographs that under a wide variety of operating conditions a very high degree of uniformity or evenness is achieved over the cooking surface of the present invention. From
FIGS. 23 to 25 show a vented barbeque hood assembly 100 suitable for use with the above described barbeque. The assembly 100 includes a hood 101 hingedly connected (not shown) to the barbeque in the conventional manner. The hood thus encloses a cooking region 102 immediately above the cooking surface. The rear side 103 of the hood 101 is provided with three vents 104 which substantially extend along the rear side 103 of the hood. The vents are formed by cutting out sections from the rear corner of the hood 101. Portions 105 of the hood left between the vents 104 provide for support of the upper part of the hood 101. A cylindrical baffle 106 is mounted adjacent the vents 104. The baffle 106 is formed by a cylindrical section cut to remove three sections that form openings 107. Annular bands 108 and a longitudinally extending brace 109 are left in place so the structure maintains its integrity. A length of angle section 110 is fixed to the inside of the hood 101 so that the baffle 106 is captively retained between the lower corner 111 of the hood and the angle section 110. This is best seen in
The foregoing describes only some embodiments of the present invention and modifications can be made without departing from the scope of the invention.
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|U.S. Classification||126/25.00R, 126/39.00E|
|International Classification||A47J37/07, B08B15/02, F24B3/00|
|Cooperative Classification||B08B15/02, A47J37/0713|
|European Classification||A47J37/07B3, B08B15/02|
|Apr 17, 2006||AS||Assignment|
Owner name: MALOLO PTY LTD., AUSTRALIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MCDONALD, ROSS;REEL/FRAME:017491/0544
Effective date: 20050808