Slightly Pressurized Flat-top Stove

Abstract

A kitchen range having a smooth top of heat-resistant glass, beneath which there are infrared gas burners. Heating is by infrared radiation and conduction through the glass top. The products of combustion are exhausted through an outlet at the rear of the range. Its burners are positioned within a closed chamber into which a small blower directs air so as to produce a slightly elevated air pressure.

Description

This invention relates to gas ranges or stoves of the flattop type, and more in particular to stoves of the type shown in U.S. Pat. No. 3,470,862, which utilize infrared radiant heating.

It is an object of the present invention to provide improved gas ranges of the general type of the one disclosed in the above-identified patent. Another object is to provide improved control for gas burners of the type shown in the above-identified patent. These and other objects will be in part obvious and in part pointed out below.

In the drawing:

FIG. 1 is a perspective view with parts broken away of one embodiment of the invention;

FIG. 2 is a fragmentary top plan view of the embodiment of FIG. 1; and

FIG. 3 is a sectional view on line 3--3 of FIG. 2.

Referring to FIG. 1 of the drawing, a flattop, gas-fired cooking range or stove 2 has four burner units 4, 6, 8 and 10. Each of the burner units is formed by an integral sheet material assembly 12 (see also FIG. 3) which is supported in a sheet metal traylike shell 14. Shell 14 has a bottom wall 16 (see also FIG. 2), a rear wall 18, sidewalls 20 and a front structure 22. Structure 22 includes a horizontal top strip 28 and a bottom strip 27, both of sheet metal, and a vertical front panel 24. Strip 28 is attached at its ends to the sidewall 20, and at its rear edge there is an angle strip forming a ledge 29. The angle strip also extends along the sides of the shell where it is attached to the tops of the sidewalls. At the rear of the shell there is an air outlet grill 26 which rest upon an angle strip 31 attached to wall 18 and a cross strip 33 which provides a supporting ledge and which also provides an extension of ledge 29.

Resting upon ledge 29 is a plate 30 of heat-resistant glass which has its top surface flush with the top surface of shell 14 and grill 26. Plate 30 provides a removable closure for the top of the shell and forms a closed chamber 31, with there being the air outlet grill 26 at the rear through which hot gases and air are exhausted. Each of the burner units 4, 6, 8 and 10 has an annular flange 35 which is in alignment with ledge 29 so that plate 30 presses tightly against the flange, and effectively closes the top of the burner unit. As will be more fully discussed below, plate 30 transmits infrared radiation very effectively, and during use it is heated to a relatively high temperature. Hence, the disc portion above each burner unit provides a smooth cooking surface upon which utensils or materials may be placed to be heated by the combined action of infrared radiation heating and conduction heating.

As shown at the upper left-hand corner of FIG. 2, a small blower 60 is mounted in front panel 24 so as to draw air through a grill 66 from the front of the range into the chamber 31 formed by shell 14 and plate 30. Blower 60 has an electric motor 62 which is energized automatically whenever any of the burner units is turned on. Blower 60 does not produce a substantial air pressure, but delivers a sufficient volume of air to chamber 31 to maintain a slightly pressurized condition therein. As is discussed below, this slightly pressurized air is utilized by the burner units in a manner to give greatly improved results. Grill 26 permits the excess air to discharge from the chamber, but the grill provides sufficient resistance to maintain the desired air pressure in the chamber. The elevated air pressure around the burner units creates a tendency for the air to leak into the units. The excess air flows past the burner units so as to cool the exposed surfaces, and it is then discharged upwardly through grill 26.

Each of the burner units has a plenum chamber 36 at the bottom to which a mixture of gas and air is delivered through a tangential supply duct 38. A plurality of adjustable angle bracket assemblies 45, mounted on the bottom of shell 14, support the burner assemblies. The upper portion of the burner unit is enlarged to provide an annular ledge 39 upon which rests a wire mesh infrared burner element 41. Burner element 41 provides a combustion surface throughout the top of the cylindrical plenum chamber 36. Above burner element 41 the cylindrical hot gas chamber 43 provides a heating zone from which the infrared radiation and the heat of conduction pass through the disc portion of plate 30.

Mounted in the sidewall of plenum chamber 36 is a tangential supply duct 38 which has a flared open end 40. Spaced from and aligned with the open end 40 of the duct is a gas supply valve 42 which receives gas from a supply pipe 48, and which has a control knob 44 and a gas discharge nozzle 46 mounted in front panel 24. Gas from the valve is discharged horizontally toward the flared open end 40 of its duct 38, thus forming a venturi assembly by which the gas entrains the desired amount of the slightly pressurized fresh air from chamber 31 for proper combustion. The turning of the knob 44 to open a valve 42 also energizes the blower motor 60 and an ignitor 49 for that burner mounted in ledge 39 above the burner surface so as to ignite the burner. The burner element 41 is of a wire mesh which produces infrared radiation when the burner unit is ignited.

Extending rearwardly from each of the hot gas chambers 43 is a rectangular gas outlet duct 50 which terminates beneath grill 26 and has a top gas outlet opening 52, and an end wall 54 which deflects the gas upwardly through the grill. Hence, when a burner unit is operating, the hot gases are discharged through opening 52, and there is sufficient jet effect to cause a circulation of fresh air at grill 26 so that the fresh air mixes with the hot gases and dilutes the hot gases and reduces the temperature of the air passing upwardly from the grill. As indicated above, the circulation of the air through shell 14 prevents excessive heating of the walls of the burner units. That characteristic is very important, particularly with ranges or stoves for domestic and general usage. Normally, when air at atmospheric pressure is aspirated by the jet of gas, there are limitations upon the limits on reducing the heating effect of the burner. Special arrangements may be provided for overcoming this difficulty. However, with the present invention, the difficulty is overcome by the simple procedure of producing a slightly pressurized air condition in chamber 31. That gives additional beneficial effects as discussed above. It also insures the proper exhausting of the products of combustion from the burner units. The pressurized air condition in chamber 31 insures the entrainment of air with the gas even at very low gas flow rates. Hence, the burners may be modulated throughout a very wise range of heating rates.

When a burner unit is ignited, the infrared radiation is transmitted through the disc portion 56 of plate 30, which is the portion or zone of the plate directly above the burner unit and is defined by flange 35. Disc portion 56 is also heated primarily by conduction from the hot gases in chamber 43, but there is some heating by the infrared radiation. In this embodiment, this disc portion 56 of an ignited burner unit is heated to a temperature of the order of 1,000.degree. to 1,100.degree. F. A utensil or other material placed upon the disc portion 56 is heated by the combined and direct action of both the infrared radiation from the burner element 41 and the heating by the disc portion 56. The by disc portion 56 may be primarily by direct conduction, but there is also substantial radiation from the disc portion.

As indicated above, plate 30 is a heat resistant glass, and it has a very low heat-transfer factor. Hence, while the disc portion 56 is at a very high temperature, there is negligible transfer of heat horizontally along plate 30 beyond the edge of disc portion 56, i.e., at flange 35. Therefore, plate 30 remains at substantially room temperature except for the specific areas or portions which are heated by the ignited burner units. It has been pointed out above that the gases which are discharged from an ignited burner produce a jet effect which causes hot gases and fresh air to mix and pass upwardly through and from grill 26. That circulation of fresh air through chamber 31 assists in maintaining the room temperature condition of the portions of plate 30 which are not directly above the various burner units.

This tangential duct arrangement for delivering the air-gas mixture to the plenum chamber aids in providing a satisfactory pattern of gas-air flow and distribution within the plenum chamber to insure uniform combustion and infrared radiation throughout the combustion surface of the unit. The products of combustion pass horizontally from the hot gas chamber 43 of a burner at a relatively slow rate of flow. That permits the gases to heat the disc portion 56 and then to pass rearwardly, as explained above.

Claims

What is claimed is:

1. In a gas range, the combination of, a shell construction forming a closed chamber, a pair of grill assemblies mounted in said shell respectively defining an air inlet and an air outlet therein, a gas burner unit positioned within said chamber, said burner unit comprising means forming a plenum chamber and a hot gas chamber, a burner element closing the top of said plenum chamber, and forming the bottom of said hot gas chamber and adapted to produce infrared radiation when said burner unit is ignited, a plate of heat resistant glass which transmits infrared radiation and transmits heat by conduction, said plate having a bottom surface extending over the top of said hot gas chamber, thereby to confine the hot gases in said hot gas chamber from flowing upwardly, means providing a hot gas discharge passageway from said hot gas chamber to said air outlet to discharge said hot gases from said range, blower means for supplying air to said closed chamber to maintain an air pressure therein greater than atmospheric pressure, said grill assemblies being adapted to restrict the flow of air therethrough thereby to maintain said air pressure within said closed chamber at a pressure slightly elevated above atmospheric pressure, and an air and combustible gas supply assembly comprising a supply duct operatively connected at one end to said plenum chamber and having a flared open end in said closed chamber and a gas discharge nozzle located in spaced relation to and substantially coaxially of said flared open end, said supply duct and said discharge nozzle defining a venturi assembly whereby gas discharged from said nozzle entrains pressurized air in said chamber and is projected with said entrained air through said duct to said plenum chamber

2. A gas range as described in claim 1 wherein one of said grill assemblies is located along a front edge of said shell construction forming said air inlet, and the other of said grill assemblies providing said air outlet is located at the side of said shell assembly opposite to said front side and opens upwardly of said shell, and wherein said means providing a hot discharge passageway projects the hot gases upwardly through said air outlet.

3. A gas range as described in claim 2 wherein said shell construction and said gas burner unit are formed of sheet material.

4. A gas range as described in claim 2 which includes a plurality of said burner units and said means providing a gas discharge passageway and a corresponding number of said air and gas supply assemblies.