Patent Description:
Typical commercial electric chargrills utilise electric heating elements housed within the grill bars on which food items rest. Fats and oils generated by the cooking process are channelled away into a fat tray, which may also contain water to reduce the risk of fat fires. Over time, the fat tray will become full of fatty residue and this must be safely disposed of. However, fat fires are still a major concern and there are widespread problems with inappropriate disposal of fatty residues such as disposal down drains.

<CIT> describes an example of a known electric grill. This includes an electrically heated heating platform, with side walls and grill bars spaced above it to define a heating chamber. An air supply is located in the side walls.

The present invention provides an electric grill comprising a heating platform, a plurality of side walls, a plurality of grill bars spaced above the heating platform and a heating chamber defined between the heating platform, the side walls and the grill bars, wherein the heating platform is electrically heated, the grill further comprising a first air supply located centrally in the heating platform for delivery of pressurised air into the heating chamber and configured to direct airflow out across the heating platform, and a secondary air supply located in the side walls and configured to direct airflow along the side walls to create a vortex of air flowing around the centrally located first air supply.

Preferably, the heating platform comprises two conductive plates with electric heating elements sandwiched in between them. For example, the first plate may comprise upper and lower surfaces and a plurality of grooves are formed on the lower surface, the second plate may comprise upper and lower surfaces and a plurality of grooves are formed in the upper surface, wherein the grooves in the first and second plates co-operate to form channels for receiving heating elements when the first and second plates are sandwiched together.

The grill bars do not contain heating elements and are heated by radiation from the heating platform. Preferably the heating platform is configured to reach a temperature of up to <NUM> so as to heat the grill bars to a temperature up to <NUM>. For example, the heating platform may be formed from metal or a ceramic material.

The first air supply may comprise at least one opening in the heating platform connected to a source of pressurised air and an airflow diverter configured to divert airflow evenly across the surface of the heating platform. The airflow diverter may comprise an elongate column extending through an opening in the heating platform and a cap mounted on the upper end of the column. In particular the airflow diverter may comprise a column with a plurality of radially projecting ribs.

The second air supply may comprise at least one opening in each side wall located adjacent an end of the side wall and connected to a source of pressurised air.

Preferably, the heating platform and side walls are located within a housing having inner and outer walls and an air chamber between the inner and outer walls, wherein the air chamber is connected to a source of pressurised air and communicates with the opening in the heating platform and with the openings in the side walls. Typically, the source of pressurised air comprises at least one fan.

In another embodiment, the heating platform and side walls are located within a housing having inner and outer walls and a first air chamber between the inner and outer walls, wherein the air chamber is connected to a source of pressurised air and communicates with the openings in the side walls of the heating chamber, and further comprising a second air chamber defined between the heating platform and the inner wall of the housing, wherein the source of pressurised air comprises a fan configured to draw air from the second air chamber and to supply it to the first air chamber.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:.

<FIG> shows a perspective view of an electric grill <NUM> in accordance with one embodiment of the present invention. This is illustrated as a freestanding unit, but a grill incorporating the present invention could also be configured as a built-in unit.

The grill <NUM> comprises a body <NUM> largely made of sheet metal. Grill bars <NUM> are provided above a heating chamber which is subscribed further below. The body <NUM> may include a vertical back plate <NUM>. Although not shown, a hinged lid may also be provided which can close over the top of the grill bars <NUM> to provide an enclosed cooking chamber. The grill bars <NUM> are typically made of cast iron and are able to withstand temperatures up to about <NUM>-<NUM>.

<FIG> and <FIG> show part of the grill <NUM> in <FIG> with the grill bars <NUM> removed to show the heating chamber <NUM> beneath. The heating chamber <NUM> is defined between a heating platform <NUM>, side walls <NUM> and the grill bars <NUM> (when present).

The heating platform <NUM> is electrically heated. Electrically powered heating elements may be located within the heating platform <NUM>. For example, the heating platform <NUM> may comprise two metal plates 20a,20b each with upper and lower surfaces. The lower surface of the upper plate 20a and the upper surface of the lower plate 20b are both machined with a number of grooves <NUM>. When the plates 20a and 20b are sandwiched together the grooves <NUM> in each plate align to define channels into which heating elements are fitted. For example, the grooves <NUM> may be semi-circular in cross-section so that when the plates 20a and 20b are sandwiched together, the grooves <NUM> align to define channels with a circular cross-section. <FIG> shows the upper plate 20a in place and <FIG> shows the lower plate 20b with the grooves <NUM>, the upper plate 20a having been removed for illustrative purposes.

As noted above, the two plates 20a, 20b may both be formed of metal, e.g. steel, or another conductive material, for example a ceramic material such as silicon carbide. In this case, heat insulation may be provided underneath the heating platform <NUM>. Alternatively, the lower plate 20b may itself be formed from an insulative material.

In use, the heating platform <NUM> is heated by the heating elements and acts as a primary heat source for cooking. The grill bars <NUM> which are located a short distance, e.g. <NUM>-<NUM>, above the heating platform <NUM> are heated largely by radiant heat and some convection from the heating platform <NUM>. Thus, the grill bars <NUM> form a secondary heat source for cooking, but do not contain heating elements themselves. The heating platform <NUM> is typically heated to a temperature up to about <NUM>, at which pyrolytic processes occur, and this enables the grill bars <NUM> to reach a temperature of <NUM>-<NUM>. This source of primary heat provided by the heating elements set inside the heating platform <NUM> remains at a constant temperature, and so any required changes to the secondary heat source for different cooking styles can be achieved through adjustments to the depth between the grill bars <NUM> and the heating platform <NUM>.

Food items resting on the grill bars <NUM> are cooked through primarily by heat from the primary heat source, that is the heating platform <NUM>. Direct contact of the food items with the secondary heat source, i.e. the grill bars <NUM>, brands the food items with chargrill lines without completely burning the food items. The temperature which the grill bars <NUM> attain provides a suitable environment for the Maillard reaction to occur, which gives food its distinctive browned appearance and desirable flavour.

The grill <NUM> of the present invention does not include a fat tray to collect excess fats and oils. Instead, the grill <NUM> further comprises a forced air supply system to help the oxidation process of any fat and oils produced by the foodstuffs that would otherwise drip down into the heating chamber <NUM> during cooking.

When fats and oils combust, the large carbon chain molecules associated with them require more oxygen to achieve complete combustion. With insufficient airflow, a sooty, carbon rich flame with excess carbon monoxide will be produced. However, in the present invention, the forced air supply results in cleaner burning of the fats and oils and a reduction of the black acrid smoke associated with partially burnt oils and fats. It is known that pyrolytic actions commence at around <NUM> and with the addition of oxidation in an aerated environment provided by the forced air supply of the present invention, this can aid in the oxidation of the organic material into an inorganic dust or ash. Therefore, the grill <NUM> of the present invention ensures complete combustion of any oils and fats, leaving only light ash residue which can be easily vacuumed away during periodic cleaning. The grill <NUM> does not create fatty residues which present a risk of fire as well as health and environmental concerns.

To provide the forced air supply system in the present invention, the heating chamber <NUM> is provided within a double-skinned support structure <NUM> which includes first and second air supplies which supply pressurised air into the heating chamber <NUM>. The support structure <NUM> comprises inner and outer casings <NUM>,<NUM> nested together with an air chamber <NUM> between them. This can be seen in <FIG>. The inner casing <NUM> has a centrally located opening <NUM>. Below opening <NUM> there may be an air inlet assembly <NUM> comprising a perforated wall extending between the inner and outer casings <NUM>,<NUM> defining a central air chamber beneath the opening <NUM>. The structure of the air inlet assembly <NUM> may be similar to that described in <CIT>. A tube <NUM> extends upwardly from the opening <NUM> to the underside of the heating platform <NUM>. The heating platform <NUM> is also provided with a central opening <NUM> which is coaxial, but of a smaller diameter, than the tube <NUM> and the opening <NUM>. These features are best seen in <FIG>.

Pressurised air is supplied into the chamber <NUM>, for example by fan <NUM> (which is shown only schematically in <FIG>, although in practice this may be located within the body <NUM> of the grill <NUM>, below the support structure <NUM>).

The first (primary) air supply delivers pressurised air into a central region of the heating chamber <NUM>. Pressurised air from the air chamber <NUM> passes, via the air inlet assembly <NUM> and the opening <NUM> into the tube <NUM> and then through opening <NUM> in the heating platform <NUM> into the heating chamber <NUM>.

An air channelling device <NUM> is located in the opening <NUM> and protrudes up into the heating chamber <NUM> and down into the tube <NUM> towards opening <NUM>. The air channelling device <NUM> comprises a central column with a plurality of radially projecting ribs. For example, there may be four projecting ribs, so that it is cruciform in cross-section as seen in <FIG> and <FIG>. A circular cap <NUM> is located on the top end of the air channelling device <NUM> as seen in <FIG>. The lower part of the air channelling device <NUM> can be seen in <FIG> while the upper end, without the cap, is illustrated in <FIG>. The air channelling device <NUM> divides the opening <NUM> in the heating platform <NUM> into four quadrants. The cap <NUM> deflects upward airflow passing through these four quadrants and diverts it laterally to flow out into the heating chamber <NUM> across the heating platform <NUM>. This arrangement distributes airflow fairly evenly around the heating chamber <NUM>.

The secondary air supply comprises a plurality of openings <NUM> in the side walls <NUM> of the heating chamber <NUM>. Preferably one or more openings <NUM> are provided in each side wall, located at one end near to a corner where one side wall <NUM> meets the next. The openings <NUM> communicate with the air chamber <NUM> formed in the support structure <NUM> and therefore jets of pressurised air exit the openings <NUM> into the heating chamber <NUM>. Since the openings <NUM> are located towards the corners, this tends to create a vortex airflow which swirls around the heating chamber <NUM>. This helps to pull the airflow from the primary air source in the centre outwardly, to ensure there is good airflow throughout the whole heating chamber <NUM>. In addition, if any fat or oil droplets do combust, the airflow pushes such flare ups laterally rather than upwards. This minimises the flare up and also prevents the food being cooked from becoming burnt.

<FIG> is a schematic plan view of the heating platform <NUM> illustrating the airflow. The arrows P emanating out from the central opening <NUM> represent the airflow extending out in all directions from the first air supply. The arrows S extending from close to the corners and along the edges represent the airflow from the second air supply which tends to swirl around the heating chamber <NUM>, in this case in an anticlockwise direction. The air flow from central opening <NUM> initially spreads out radially in all directions across the heating platform <NUM> but is gradually diverted by the air flow from openings <NUM> in order to create the vortex of air flowing around the opening <NUM>.

The forced airflow provided by the first and second air supplies permits fuller combustion of any fats and oils from the food items. Any flames which do occur burn more cleanly and quickly and the production of smoke is reduced or eliminated. Any residue will form ash or dust which can be cleared from the heating chamber <NUM> by vacuuming. No fatty residue or stagnant oil remains to be disposed of.

As noted above, the grill <NUM> of the present invention does not include a fat tray to collect fats and oils dripping from the food being cooked. Instead, the heating chamber <NUM> below the grill bars <NUM> is an enclosed, controlled environment with airflows provided in a controlled manner via the first and second air supplies. Air can only be exhausted from the heating chamber <NUM> from the top, through the grill bars <NUM>. This contrasts with conventional grills which require fat trays beneath the grill bars and are therefore of a more open construction and subject to external, uncontrolled air movements below the grill bars. In the present invention, the enclosed heating chamber with controlled airflows provides the improved performance of the present invention.

In this way, an improved electric grill is provided. The grill cooks foodstuffs quickly and efficiently, to maintain flavour and texture and with minimal shrinkage. It also obtains the desired chargrill characteristics without burning the food or creating unwanted smoke and fatty residues. The entire heating chamber is heated to a very high temperature which allows the vapourisation of animal fats and oils to occur, minimising residues and keeping the food items succulent.

An alternative embodiment of the electric grill <NUM> of the present invention is shown in <FIG>. This differs from the embodiment above in relation to certain features of the secondary air supply into the heating chamber <NUM>, although the other features of the grill <NUM> are the same as described previously.

In this case, the secondary airflow supplied to the openings <NUM> in the side walls <NUM> of the heating chamber <NUM> is drawn from a second air chamber <NUM> which is the space between the inner casing <NUM> and the underside of the heating platform <NUM>. The air in this second air chamber <NUM> will be heated up when the grill <NUM> is in use and is drawn via a duct <NUM> connecting the space <NUM> to a fan <NUM>. The fan <NUM> then supplies this heated air into the air chamber <NUM> between the inner and outer casings <NUM>,<NUM> of the support structure <NUM>. This heated air then flows via the openings <NUM> into the heating chamber <NUM> to create the vortex airflow which swirls around the heating chamber <NUM>. The heated air may also be supplied to the air inlet assembly <NUM> and into the centre of the heating platform <NUM> in the heating chamber <NUM>. Alternatively, the primary air supply to the air inlet assembly <NUM> may be ambient air supplied by another fan.

Claim 1:
An electric grill (<NUM>) comprising a heating platform (<NUM>), a plurality of side walls (<NUM>), a plurality of grill bars (<NUM>) spaced above the heating platform (<NUM>) and a heating chamber (<NUM>) defined between the heating platform (<NUM>), the side walls (<NUM>) and the grill bars (<NUM>), wherein the heating platform (<NUM>) is electrically heated, characterized in that the grill (<NUM>) further comprises a first air supply located centrally in the heating platform (<NUM>) for delivery of pressurised air into the heating chamber (<NUM>) and configured to direct airflow evenly across the heating platform (<NUM>), and a secondary air supply located in the side walls (<NUM>) and configured to direct airflow along the side walls (<NUM>) to create a vortex of air flowing around the centrally located air supply.