Abstract: The invention relates to a method of making glass-ceramic plates which are bent at a radius of curvature especially suitable in the manufacture of cooking plates.

Abstract: The invention is directed to an arrangement for adjusting a pressure-fluctuation free supply of gas and for controlling an operating pressure of an air/gas mixture to a radiation-gas burner of a gas cooking apparatus. The radiation-gas burner has a burner chamber and is mounted in a housing below a cover plate. The arrangement includes a gas supply conduit connectable to a gas source for receiving the gas and a pressure controller is mounted in the gas supply conduit for controlling the pressure of the gas to a constant operating pressure of at least 2.5 mbar above atmospheric pressure. A control unit is connected to the pressure controller for receiving the pressure-controlled gas and for metering the gas to the radiation-gas burner. The control unit includes a valve block having at least one exchangeable nozzle adapted to the type of gas from the gas source and a feed conduit has a clear cross-sectional area and communicates with the burner chamber. The feed conduit has an inlet opening adjacent the nozzle.

Abstract: A burner is disclosed, comprising: a burner body and a burner lid coupled to the burner body so as to form a plurality of gas ports in a substantially circular and substantially planar arrangement, said gas ports being interposed between the burner body and the burner lid and adapted to have a corresponding array of flames extending from the gas ports during combustion of a fuel gas.

Abstract: Arrangement of an electrical heating element as a cooking zone, having as a carrier a ceramic of very high thermal conductivity, in a cutout of a surface consisting of glass-ceramic, glass, ceramic, metal or plastic. The ceramic carrier of the heating element can rest with overlap on regions of the surface which deviate from the main plane of the plate-like surface so as form elevations running linearly, such as cone frustums, spherical segments and/or cones, and which define the edge of the cutout. This elevated rest of the heating element serving as a bearing, and the underside of the surface serving as an abutment for a cover arranged below the main plane of the surface and closing off the cutout downwards, and the heating element being fixed positively and non-positively in the cutout of the surface by way of fastening elements connected firmly to the heating element and firmly and releasably to the cover.

Abstract: A burner unit for a gas cooking unit includes an upwardly concave, disk-shaped member. There is a manifold below the disk-shaped member which has a top with a circular opening. The manifold is connected to the disk-shaped member within the opening. There is a circular gap extending about the disk-shaped member between the member and the manifold. The manifold has a gas connection located radially outwards from the disk-shaped member. There is an opening for air adjacent the connection. Air mixes with gas entering the manifold through the connection and an air/gas mixture passes through the gap between the manifold and the disk-shaped member.

Abstract: The gas burner of the present invention includes a mated burner body and a burner lid. A plurality of gas ports in a substantially circular and planar arrangement are interposed between the mated body and lid and are directed radially from the body and lid. An air shield member is coformed to and extends radially from the burner body or burner lid. Extending radially from the air shield member in substantial radial alignment with the gas ports is a plurality of flame partitions equal in number to the gas ports. Each flame partition has two attached tabs which are substantially perpendicular to each other when the flame partition is observed in cross-section.

Abstract: A fluid control assembly that includes fluid valving, fluid regulation, automatic safety shut-off valving and manual shut-off valving in one assembly, a novel fluid control unit that integrates the above functions in one unit, and a novel ignitor and a novel seal and diaphragm for use in the assembly.

Abstract: A gas burner for a cooking device. The gas burner includes a burner head connected to a mixing pipe. An impeller disk is disposed above the burner head and below a cover. The impeller disk is operable to swirl a gas stream and defines a generally circular inner opening. The impeller disk includes a body and a plurality of paddle-shaped flame guidance members formed by a plurality of evenly-spaced and radially-directed cuts in the body. The flame guidance members are bent such that edges of the flame guidance members form oblique angles with the body. The edges each have an end disposed above the body and another end disposed below the body.

Abstract: A gas cookstove having in its top face an opening forming a recess for accommodating a removable container below which is mounted at least one gas burner supported by a tray retained on the edge of the recess like opening and interposed between a casing and the bottom of the removable container, the cookstove being applicable to the cooking of any foodstuff in a container removably fitted into the top of the cookstove.

Abstract: An infrared gas burner for a gas cooker including a mixing tube arranged between a gas valve and a burner unit and adapted to mix gas supplied from the gas valve with air, a support member for supporting a ceramic plate within the burner unit in such a manner that the gas mixture emerging from the mixing tube passes through flame holes of the ceramic plate, a temperature control unit adapted to measure a temperature of flames generated by the burner unit, thereby controlling the amount of gas supplied to the burner unit based on the measured temperature, and a cover unit disposed over the burner unit and adapted to transfer infrared radiant heat and exhaust heat generated at the burner unit to a cooking pot laid thereon. The mixing tube is configured to mix gas with air in an optimum state for the combustion of the gas while uniformly distributing the gas mixture through flame holes of a ceramic plate, the transfer of heat to the body of a burner unit is reduced, thereby minimizing loss of heat.

Abstract: A portable, outdoor cooking apparatus is provided which is capable of operating as both a stove and a barbecue grill. The cooking apparatus includes an elongated burner tube and a pivoting parabolic-shaped heat diffuser which can be rotated between an upright position in which the concave surface of the heat diffuser covers the burner tube for barbecue cooking and an inverted position in which the heat diffuser leaves the burner tube exposed directly to the cooking surface for stove cooking.

Abstract: A portable, outdoor, high temperature griddle is provided capable of cooking international foods in a cross-wind without adversely affecting the flame. A wind-deflector is provided which sits between the griddle and the burners and deflects the wind along a tortuous pathway to reach the burners.

Abstract: A combination of a gas stove with oxygen device is provided. The disclosure comprises generally a pair of valves secured to the front side of a gas stove. The valves each has a rotor plug therein and each rotor plug has an elongate shaft axially connected and extended outward through the central hole of the valves with one of the shaft connected to a knob at a free end. Each of the shafts has a gear perpendicularly secured to an appropriately middle periphery and meshed each other. So that the two valves can be operated in concert when turns the knob. One of the valves supplies gaseous fuel and other supplies oxygen to the same burner in proper rate and mixed in the burner before burnt at the apertures. Both the gaseous fuel and the oxygen are supplied via a branched pipe so that they can enter into every portion of the burner.

Abstract: A unique outdoor full function cooking appliance including a cart, a grill fixedly mounted on the cart and having a hemispherical body and a lid, two ring burners one disposed within the other, mounted within the hemispherical body, a flame tamer arranged within the hemispherical body and located above the two ring burners, a supporting mount fitted in a central portion of the flame tamer, a circular disc, and a cooking wire grid mounted with the hemispherical body and located above the supporting mount, whereby the cooking appliance combines the functions of barbecue gas grill, stove and oven in one unit thereby enabling it to be used with other cooking wares for making soup, sauce, frying dishes, and vegetable in addition to barbecuing.

Abstract: A range for sealed combustion of a gaseous fuel has a hob assembly and an oven. The hob assembly comprises a glass ceramic cooking surface sealed to a support box and one or more burners. The hob assembly and oven are connected to a fresh air intake/exhaust manifold, such that there is no air exchange between the range and the room in which it is located. Narrow heat transfer passageways are defined between the cooking surface and an internal surface around each burner.

Abstract: The gas cooking assembly of the invention includes at least one gas-fired burner which has a burner chamber and a burner plate, especially a burner plate made of fiber material, the gas-fired burner being arranged below a continuous cooking plate made of a material conductive to heat radiation such as a glass ceramic, glass, ceramic or the like material. Control units are provided for metering gas as well as conventional ignition units, safety units and temperature-monitoring units. Exhaust-gas channels conduct away combustion gases. A blower brings additional air to the burner plate. The blower and control unit are located in a partitioned-off space wherein an overpressure is maintained by the blower. The partitioned-off space is connected via pipes to the burner chamber and to the ambient. The pipes are gas tight at their peripheral surfaces in the region outside of said partitioned-off space.

Abstract: An atmospheric gas burner produces improved turndown by separating a small number of the burner ports for simmer service. The burner has an internal baffle which includes a cup section having four outwardly-extending channels. Each one of the channels aligns with a separate one of the ports. The burner also includes a first fuel nozzle arranged to provide fuel to all of the ports in conventional fashion and a second fuel nozzle which provides fuel to the four simmer ports only. The second fuel nozzle has an injection orifice with a smaller cross-sectional area than the injection orifice of the first fuel nozzle. Preferably, the second orifice is sized to provide the same input rate at a maximum pressure that the first orifice does at a minimum pressure. By using a small number of ports for simmer service, the gas velocity through these ports is increased and improved turndown is achieved. In another embodiment, the baffle divides each port into upper lower sections, instead of separating some of the ports.

Abstract: There is provided a range for sealed combustion of a gaseous fuel comprising a hob assembly and an oven. The hob assembly comprises a glass ceramic cooking surface sealed to a support box and one or more burners. The hob assembly and oven are connected to a fresh air intake/exhaust manifold, such that there is no air exchange between the range and the room in which it is located.

Abstract: A sealed gas surface burner having a ring portion that sits on the main top around the periphery of the main top aperture through which the burner extends. The ring portion forms a substantially liquid tight seal with the main top, and has a raised shoulder to prevent liquid on the main top from running down through the burner aperture in the main top. A burner body is supported by the ring portion at spaced intervals to provide passageways from underneath the main top. A cap is supported by the burner body thereby forming a chamber which receives a mixture of gaseous fuel and primary combustion air. The mixture issues from ports in the side wall of the burner body where it is ignited to produce a cooking flame. Secondary combustion air is drawn from underneath the main top through the passageways in the burner to support combustion of the flame.

Abstract: A cooking appliance having a plate of a material transparent to thermal radiation, such as glass-ceramic, having adjustable heat sources distributed under, in, or on the plate, which are heated by direct or indirect heat transfer, electrically, and/or by gas and/or other heating means, the plate possessing at least two types of heat sources which use different kinds of heat transfer, these all being heated by means of gas.

Abstract: A gas-fired broiler which produces infrared heat by means of stainless steel radiants. Stainless steel baffles are located adjacent to and between each pair of radiants which causes the flue air and spent gases to be redirected over the hot radiants, thus superheating the air. The superheated air and the heat from the radiants further heat the baffles. By incorporating the baffles between each pair of radiants to block the direct venting of the air, greater efficiency is achieved. The improved efficiency of the broiler is provided by producing higher cooking temperatures while using the same amount of BTU's.

Abstract: A novel dual mode, downdraft gas range provides a sealed top and sealed gas burners that can be operated effectively in a power burner mode with a downdraft exhaust and otherwise in an atmospheric mode. In the range, a separate and independently operating air/gas supply chamber for each sealed burner is supplied with a controllable flow of gas, and, in the power burner mode, with a controlled forced flow of primary combustion air from a combustion air blower and pressure-adjustable air plenum that supply all air/gas chambers, and each air/gas supply chamber is provided with a gated opening, which is operated to provide an unobstructed flow of primary combustion air from atmosphere in non-power burner operation. The mixture of air and primary combustion air flows from the air/gas supply chamber through a sealed conduit formed to be free of obstructions and abrupt changes in direction with a flow diffuser provided adjacent the gas burner.

Abstract: A gas hob has a glass ceramic top plate and gas fired heat radiating burner units below the top plate. Each burner unit has a lower plate which includes a number of concentric chambers. A ceramic burner plate is disposed over the lower plate. The burner plate is perforated to match the arrangement of concentric chambers to provide concentric gas burning rings. The supply of gas to the burner units is controllable by respective control valves enabling gas to be supplied only to the burner plate perforation at which supply of heat is required. A fan below the level of the burner units supplies air to a plenum chamber which communicates with ducts leading to the concentric chambers. The fan supplies combustion air at all times when a burner unit is in operation. Gas from the control valve mixes in the ducts with air from the plenum chamber before entering one of the concentric chambers and the gas burning ring.

Abstract: This invention relates to a spirit stove. The spirit stove comprises a top (11) which is provided with at least one hot plate (15) of hear conducting material which is placed so that the plate joins the top. The stove has a spirit burner (33, 36, 37, 38) which is placed below the plate and to which air flows and from which fumes leave by natural ventilation. The plate is surrounded by a heat insulating material (23) having a surface which is exposed to the flames and/or the fumes.

Abstract: A dual mode downdraft gas range provides a number of substantial advantages, including operation in a powered burner mode and an atmospheric mode. In the powered burner mode, a plurality of powered open flame surface burners can provide even heat from each of the burners as a result of burner flames that provide substantially complete combustion close to the burner outlets in short, stable flames that are unaffected by an adjacent downdraft exhaust or other outside influences. In the atmospheric mode, the gas burners can operate without a downdraft exhaust. The gas range can meet agency requirements in both the powered mode and atmospheric mode of operation and can be inherently fail-safe in the event of a power failure in the downdraft exhaust system. The gas range can be economically and easily manufactured and assembled, with burner controls arranged for convenient operation at one side of the range box for the plurality of burners.

Abstract: A burner construction, igniter assembly therefor and methods of making the same are provided, the igniter assembly comprising an electrically insulating body member having an intermediate portion and having opposed end surfaces one of which is adapted to be disposed adjacent a cap of a burner construction, and an electrically conductive L-shaped electrode carried by the body member and having two legs one of which extends out of the intermediate portion thereof for sparking to the cap, the body member comprising an electrically insulating cover member secured to the intermediate portion so as to cover part of the one leg of the electrode and to define part of one surface of the body member, the one surface having a groove therein for feeding fuel from a chamber of the burner construction to the one leg of the electrode that is not covered by the cover member.

Abstract: A spirit stove comprises a fuel container (14) having an opening (15) through which fuel can be poured to fill the container, and through which combustion by-products are exhausted during burning. The stove has a burner tube (23) placed above the opening and a flame spreader (39) situated above the burner tube. The flame spreader is pivotally mounted to the spirit stove and can be moved from a first position in which it covers the opening (24) of the burner tube to a second position in which a slot is created between the flame spreader and the burner tube which is large enough to admit an igniter to be inserted into the burner tube, the flame spreader in the last mentioned position still generally covering the opening of the burner tube to inhibit direct pouring of fuel down into the opening (15).

Abstract: A heating apparatus comprising a burner including a burner body having an air-fuel mixture chamber and a burner cap formed with a plurality of flame ports, a pan formed with an opening for receiving the burner body, a top plate placed on an upper face of the heating apparatus and a trivet placed on the top plate. The burner cap includes a cylindrical portion formed with an air passage, a convex portion projecting upwardly from an inner face of the cylindrical portion and a cover member formed integrally with an upper portion of the cylindrical portion through the convex portion such that a gap is defined between an upper end of the cylindrical portion and a lower face of the cover member.

Abstract: A gas cooking appliance for cooking chow mein, pan cakes or the like on a hot plate mounted thereon, which cooking appliance includes a pulse combustion burner installed within as internal compartment of the appliance and having a combustion chamber coupled with a bottom portion of the hot plate to take place pulse combustion of a mixture of gaseous fuel and air supplied thereinto, wherein the hot plate is in the form of a thick metallic plate formed therein with a tailpipe passage which is connected at one end thereof to an exhaust port of the combustion chamber and extends outwardly through the metallic plate to permit the flow of combustion products discharged therethrough from said combustion chamber.

Abstract: A heating device for mounting in a window opening, particularly useful for vehicles, camper shells, and other enclosures, which includes a mounting plate; air intake and exhaust tubes, a burner contained within a sealed housing, an external fuel source, and a connecting line between the fuel source and the burner. The lower portion of the mounting plate rests upon the window sill and an upper portion engages the outer surface of the window framework to make the device useable for both vertically and horizontally movable windows. The sealed housing, which includes a cooking surface, precludes noxious fumes or explosive fumes from escaping into the confines of the area being heated. The external fuel source, preferably a portable propane tank, rests on the ground outside the enclosure, as an additional safety factor. A heat deflector, pivotal over the top surface of the burner housing, disperses the heated air to prevent overheating of the ceiling and also serves as a safety guard.

Abstract: A gas burner includes a burner tube that has a gas supply tube extending into one end and an air intake orifice adjacent thereto. A perforated shield is clamped onto the tubes to enclose the air intake orifice.

Abstract: An insect guard is provided for guarding against the entrance of insects into the venturi tubes of gas grills which may result in clogging of the fuel flow to the burners of a gas grill. The insect guard includes using a plurality of small openings to define the primary air opening in the venturi tube, and also providing for a close tolerance fit at the connection between the venturi tube and the outlet orifice of the valve such that insects are substantially prevented from entrance into the venturi tube.

Abstract: A cooking grill assembly of high energy efficiency is disclosed. A gas burner arm heat source is oscillated through an arc of a variable amount in order to limit the heat source cooperation with the cooking grill to that area of the grill on which the food is to be cooked. A means to limit the heat source to this given area of the grill is provided and includes a motor, drive linkage, and variable stop means so that the arc of the burner tube oscillation is limited to the selected area. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Abstract: Equipment for the controlled and uniform cooking of foods of lesser thickness so that cooking occurs uniformly on the whole upper surface of the food and uniformly on the whole lower surface of the food comprising a base having a hole; a lower burner disposed below the hole; a heat conducting plate disposed over the hole, a lower surface of food resting on the plate being uniformly cooked by the thermal conduction from the lower burner through the plate; a chamber having an open bottom spaced from the plate; an upper burner disposed in the chamber; a fume deflector device mounted to the chamber and mounted between the upper burner and the heat conducting plate for deflecting and evenly distributing hot fumes generated by the upper burner so that a uniform column of hot fumes descends vertically toward the heat conducting plate and strike perpendicularly over an upper surface of food resting on the plate; and a deflector ring encircling and concentric with the chamber and having a lower end in contact with at

Abstract: Gas burner arranged to operate with several types of gas, comprising a burner body equipped with an air inflow regulator ring which is a cylinder of revolution with an air inlet in its cylindrical side wall. The two end surfaces are provided respectively with two coaxial apertures for the outflow of the gas mixture of different diameters. This ring and its mounting emplacement in the body are such that it can be positioned in one or the other of two possible positions, with the aperture of largest diameter or of smallest diameter facing the gas nozzle accordingly as the gas is respectively a liquified petroleum or a manufactured or natural gas.

Abstract: Flat type gas burner with a body having a central vertical passage and a cap which define between them an annular convergent-divergent duct supplying flame orifices in the annular foot of the cap. The burner comprises an enclosure into which opens a flame orifice conferring on the mixture a flow speed identical with that of the other orifices. The volume of the enclosure permits an expansion of the mixture substantially to static pressure. The outlet aperture of the enclosure confers on the mixture a speed of flow 7 to 12 times less than that of the other orifices.

Abstract: An insect guard is provided for guarding against the entrance of insects into the venturi tubes of gas grills which may result in clogging of the fuel flow of the burners of a gas grill. The insect guard includes using a plurality of small openings to define the primary air opening in the venturi tube, and also providing for a close tolerance fit at the connection between the venturi tube and the outlet orifice of the valve such that insects are substantially prevented from entrance into the venturi tube.

Abstract: A gas stove burner-combustion chamber, the burner supplied with gas and with primary air from a primary intake plenum and disposed at the top of a secondary intake plenum having opposite side baffles closely spaced from the burner, divergent radiants extending upward from the baffles and sealed at the underside of a griddle plate and thereby forming an isolated combustion chamber open to a flue, and there being a plurality of said burner-combustion chambers arranged adjacently parallel with space therebetween occluded beneath the griddle plate, the burners being individually controlled for temperature variation at different areas of the griddle plate.

Abstract: A cooking stove such as an induction heating cooking stove which is fitted into an aperture on top of a kitchen unit has one or more independent heater units mounted within an outer case, below a top plate which cooking pans, etc can be heated. Each heater unit consists of an open-ended box-shaped internal chassis having one or more heater elements mounted on a top face thereof and an aperture formed in a bottom face thereof. Each internal chassis is provided with a motor-driven cooling fan which acts to produce a flow of cooling air through the interior of the chassis and out through the lower aperture into a ventilation duct, and hence to the atmosphere via a cooling air inlet/outlet section which can be conveniently provided at the upper rear part of the top of the stove. No additional ventilation apertures need be provided in the kitchen unit, and the number of heater elements can be readily varied as required, while the overall design is extremely simple and readily manufactured.

Abstract: A gas-fired cooking range having a powered combustion air and gas input; proportional turndown burner control irrespective of the number of burners being used or the degree of turndown of any burner; light-weight jet impingement/radiation members being provided on each burner for efficient heat transfer to utensils and a simplified ignitor/sensor system for all burners operable by any individual burner control.

Abstract: A cooking device having a table surface provided with a gas burner container with a plurality of surrounding ventilation holes disposed generally above a burner located within the burner container.

Abstract: A griddle includes a thick metal plate having a cooking surface and is heated from below by four infrared gas burner units. A deflector plate is mounted adjacent the outer edge of the two outer burner units and is upwardly bent at about a 45.degree. angle for deflecting infrared energy near the outer edges of the two outer burners toward the outer extremities of the bottom of the plate for producing a uniform surface temperature over the cooking surface.

Abstract: A cooking panel comprising gas-fired burner units and a continuous cooking surface consisting of glass ceramic or comparable material which is particularly suited for incorporation in kitchen appliances consists of one or two, low-height structural parts in which all main components if the burner units such as combustion chamber, gas mixing chamber, gas mixing means, exhaust gas ducts, warming zones and exhaust gas stack are integrated. These integrated structural parts can be economically manufactured with known wet molding techniques for silicate fiber material--this leading to a weight reduction--and can be built in with a minimum of assembly outlay.

Abstract: The invention relates to furnaces equipped with an insulating inner lining formed from fibers. The object of the invention is to reduce the thermal discontinuities at the level of the orifice tube of the burner. For this purpose, the orifice tube consists of blankets of fibers arranged radially round the burner and compressed to a greater extent in the inner part facing the axis of the burner than in the outer part. The density in the inner part preferably reaches 300 to 400 kg/m.sup.3.

Abstract: A cooking apparatus comprises a plurality of grease-catching elements below a rack supporting food being cooked. Each of the grease-catching elements has a heat-shielding member which protects the grease-catching element from radiant energy from a heat source. An air gap is formed between the grease-catching element and the heat-shielding member to allow free flow of air therethrough, thus ensuring that the grease-catching element is properly cooled. By allowing free flow of air through the air space, a very hot heat source may be employed without fear of raising the temperature of the grease-catching elements above the ignition point of grease drippings. The grease-catching apparatus of the invention finds particular utility in an outdoor grill, but may be applied to other types of cooking devices.

Abstract: A closed top pulse combustion burner for a flat cooking surface. The burner comprises a shallow rectangular box-like combustion chamber with its top providing a cooking surface area. Pulse combustion operation of the burner promotes high thermal efficiency. An internal baffle arrangement in the burner box provides a high degree of temperature uniformity at the cooking surface. The rectangular configuration of the burner unit allows modular construction of multiple burner units which can be individually operated at different times and/or temperatures.

Abstract: Disclosed is a gas-fired cooktop for a range which provides high thermal efficiency and low emissions of air pollutants, particularly low levels of NO.sub.x. The cooktop includes a perforated tile burner which radiates infrared energy upward at a high flux rate to rapidly quench burner gas temperatures and inhibit the formation of NO.sub.x. A perforated glass-ceramic jet plate positioned between the burner and a cooking vessel transmits most of the radiant infrared energy from the burner to the vessel and also forms jets of combustion products which are directed against the bottom of the vessel for convective heating. Thermal efficiencies of up to about 70 percent and NO.sub.x emissions as low as about 15 parts per million are achieved by the cooktop.

Abstract: A cooking appliance unit including a top plate on which food items are cooked, a horizontal frame formed around the outer periphery of the top plate, having inlet and outlet ventilation holes on only one side thereof, and a cooking appliance body below the plate and frame having walls defining first, second and third chambers therein. A heating device is provided in the second chamber below the top plate. A control device is provided in the first chamber, the first chamber being in fluid communication with the inlet holes, and the second chamber through a ventilation opening in a partition wall. The third chamber is disposed below the second chamber separated by another partition wall which contains a cooling fan, the third chamber being in fluid communication with the exhaust holes.

Abstract: A temperature control means for a cooking griddle wherein a tubular thermostat is clamped to the bottom of the griddle plate, shielded from direct engagement by the heating medium and having a predetermined portion of the temperature sensing bulb of the thermostat directly exposed to the heating medium for cooperation with the actuating fluid in the thermostat tube so as to operate the on-off switch of the heating medium within a temperature range of about 5 degrees F.

Abstract: The electronic components in the cavity of a modular induction cooktop cartridge are cooled as a result of ventilation provided by a proximity ventilation system. The cooktop cartridge is raised relative to the surface of the range and ports are provided on opposite sides of the cartridge in the raised portion whereby the proximity ventilation system educts air from the cavity and thereby causes an air circulation path through the cavity.