Convector surface cooking unit

Claim 2

A surface cooking unit for an electric range comprising range top means having an opening therein, means in said opening for supporting a utensil on the range top, disk means spaced slightly below the plane of a utensil bottom supported on said supporting means to define a planar air circulation space in said range top means immediately below said utensil bottom, said air circulation space closable at least partially by a utensil supported thereon, a casing member depending from said range top, pan means providing an inner spill chamber located in spaced relation within said casing member and underlying said disk means in space relation thereto, said pan means cooperating with said casing to provide an outer spill chamber therebetween, electrical heating means, means in said unit for supporting said electrical heating means in spaced relation intermediate said disk means and said pan means whereby upper and lower plenums are defined respectively above and below said heating means, supply air outlet means connecting said upper plenum with said air circulation space, vertical passage means connecting said supply air outlet means with said outer spill chamber, central air passage means in the form of a central vertical tube having its upper end in communication with said air circulation space and its lower end extending vertically below said air impelling means into said pan means to thereby bypass said heating means and pass spillage directly from said return air inlet means into said inner spill chamber, air return inlet means connecting said air circulation space with said central air passage means which in turn is connected to said lower plenum, air impelling means intermediate said pan means and said lower plenum for circulating air between said heating means and said air circulation space for heating said utensil, and said central air passage means communicating with said inner spill chamber whereby spillage on said unit entering said return air inlet means and said supply air outlet means will pass into said inner and outer spill chambers respectively and bypass said heating means.

Claim 3

The surface cooking unit of claim 1 wherein valve means are provided for interconnecting said inner spill chamber and said outer spill chamber said valve means being normally closed in response to the differential air pressure between said inner and outer spill chambers, and said valve means being automatically opened by spillage in said inner spill chamber.

Claim 4

The surface cooking unit of claim 1 wherein said impelling means includes a cup-shaped depending fan housing telescopically received in space relation in said pan means, said lower end of said central tube concentrically spaced within said depending housing defining return air corridor means therebetween for supplying return air to said impelling means, said depending fan housing having aperture means spaced vertically below the lower end of said central tube whereby the flow of return air is redirected vertically upwardly to said impelling means while allowing gravitational flow of the spillage into said inner spill chamber.

Claim 5

The surface cooling unit of claim 1 wherein air deflecting means are positioned between said upper plenum and said vertical outer passage means, and air deflecting means having an upstanding air deflecting portion redirecting the heated airflow from said upper plenum from a substantially horizontal outward flow to a substantially vertically upward flow.

Claim 6

The surface cooking unit of claim 4 wherein said air deflecting means having aperture means underlying said air supply outlet allowing gravitational flow of spillage into said vertical passage to whereby readily separate the spillage froM the heated airflow.

Claim 7

Surface cooking unit for an electric range comprising range top means having an opening therein, means in said opening for supporting a utensil on the range top, disk means spaced slightly below the plane of the utensil bottom to define a planar air circulation space in said range top means immediately below the utensil bottom, a casing member depending from said range top surrounding said cooking unit, said casing member having concentrically spaced pan means therein underlying said disk means defining an outer spill chamber between said pan means and said casing, said pan means defining an inner spill chamber, concentrically spaced shell means in said casing supported on said pan means, central tube means depending from said disk means and concentrically spaced within said shell means establishing supply air duct means therebetween, said shell means and said tube means cooperatively supporting electrical heating means in spaced relation below said disk means thereby defining an upper plenum intermediate said disk means and heating means, outer supply air outlet means connecting said upper plenum with said air circulation space, vertical passage means defined intermediate said casing member and said shell means connecting said supply air outlet means with said outer spill chamber, air impelling means supported in said supply air duct means in spaced relation below said heating means operative to circulate air between said heating means and said air circulation space for heating the utensil, said central tube means providing a return air passage connecting said air circulation space with said supply air duct means, stator means concentrically supported in said supply air duct means in overlying relation to said impelling means defining a lower plenum intermediate said stator means and said heating means, said lower plenum communicating with said supply air duct means via said stator means whereby air exiting from said stator means is directed radially inwardly to said lower plenum means.

Claim 8

Surface cooking unit for an electric range comprising range top means having an opening therein, means in said opening for supporting a utensil on the range top, disk means spaced slightly below the plane of the utensil bottom to define a planar air circulation space in said range top means immediately below the utensil bottom, a casing member depending from said range top surrounding said cooking unit, said casing member having concentrically spaced pan means therein underlying said disk means defining an outer spill chamber between said pan means and said casing, said pan means defining an inner spill chamber, concentrically spaced shell means in said casing supported on said pan means, central tube means depending from said disk means and concentrically spaced within said shell means establishing supply air duct means therebetween, said shell means and said tube means cooperatively supporting electrical heating means in spaced relation below said disk means thereby defining an upper plenum intermediate said disk means and heating means, outer supply air outlet means connecting said upper plenum with said air circulation space, vertical passage means defined intermediate said casing member and said shell means connecting said supply air outlet means with said outer spill chamber, air impelling means supported in said supply air duct means in spaced relation below said heating means operative to circulate air between said heating means and said air circulation space for heating the utensil, said central tube means providing a return air passage connecting said air circulation space with said supply air duct means, stator means concentrically supported in said supply air duct means in overlying relation to said impelling means defining a lower plenum intermediate said stator means and said heating means, said lower plenum communicating with said supply air duct means via said stator means whereby air exiting from said stator means is directed radially inwardly to said lower plenum means.

Claim 9

The surface cooking unit of claim 6 wherein said impelling means includes a depending housing concentrically spaced within said pan means, and said central tube means being telescopically received in spaced relation within said depending housing thereby defining a vertical return air corridor therebetween connecting said return air passage with said impelling means.

Claim 10

The surface cooking unit of claim 7 wherein said depending housing has aperture means therein providing communication between said return air passage and said inner spill chamber permitting spillage from a cooking operation to bypass said heating means and pass from said air return passage and into said inner spill chamber.

Claim 11

The surface cooking unit of claim 6 wherein said heating means comprises an electrical resistance coil, a coil support ring and an annular heater guard having an inverted channel-shaped cross section disposed in overlying concentric relation to said coil support ring, said coil support ring and said heater guard forming said upper plenum, said heater guard having peripheral air outlet means connecting said upper plenum with said vertical passage means, and deflector means in said vertical passage means operative to deliver the heated air from said upper plenum to said outer supply air outlet means, and aperture means in said deflector means located below said peripheral air outlet means to provide ready spillage segregation from the heated air.

Claim 12

The surface cooking unit of claim 6 wherein said pan means having a heat-insulating cover member, said cover member having a central opening therein for passage of said depending housing therethrough, and gasket means substantially sealing said cover member from said depending housing to provide a thermal break in the heat path between said pan means and the heated air.

Claim 13

The surface cooking unit of claim 6 wherein control means are provided for throttling the power input to said electrical heating means tO limit the maximum air temperature in said upper plenum of said unit.

Claim 14

A surface heating unit for an electric range comprising range top means having an opening therein, means in said opening for supporting a utensil on the range top, a burner disk spaced a predetermined distance below the plane of a utensil bottom supported on said supporting means to define a planar air circulation space in said range top means immediately below said utensil bottom, said air circulation space closable at least partially by a utensil supported thereon, an outer casing member depending from said range top, a heater coil assembly in said casing member including a coil support ring having a central opening a center return air tube said support ring retained on an upper flange of said return air tube so as to be substantially flush with the upper end thereof, said return air tube flange supporting said heater coil assembly in spaced relation below said burner disk whereby an upper plenum is defined between said burner disk and said heater coil assembly, said coil support ring having a convolute U-shaped groove in its upper face, a continuous spiral resistance coil supported in said convolute groove, vertical air passages providing communication between said groove and a lower plenum whereby air from said lower plenum flows through said air passages and is heated by said heating coil as it flows into said upper plenum, supply air outlet means connecting said upper plenum with said air circulation space, air impelling means in the form of a centrifugal fan having forwardly curved blades located in spaced relation below said heater coil assembly, stator means in the form of stationary forwardly curved vanes fixedly supported between parallel horizontal plates defining said lower plenum between said stator means and said heater coil assembly, return air passage means connecting said air circulating space with said lower plenum, said centrifugal fan operative for recirculating air serially from said lower plenum, through said heater coil assembly to said upper plenum, and then to said air circulation space for heating the utensil, whereby the flow of air from said centrifugal fan blades to said stator vanes is changed from an outwardly directed tangential swirl to a radially inward and thence upwardly directed flow of air into said lower plenum such that the resultant pressure in said lower plenum is increased to thereby provide a sufficient air mass flow to said air circulation space to maximize the convection rate of heat transfer along the plane of a utensil bottom supported on said surface cooking unit, and means for adjusting said burner disk relative to the plane of a utensil bottom supported on said supporting means to change said predetermined distance thereby to vary the air mass flow to said air circulation space.

Claim 15

A surface heating unit for an electric range comprising range top means having an opening therein, means in said opening for supporting a utensil on the range top, a burner disk spaced a predetermined distance below the plane of a utensil bottom supported on said supporting means to define a planar air circulation space in said range top means immediately below said utensil bottom, said air circulation space closable at least partially by a utensil supported thereon, an outer casing member depending from said range top, a heater coil assembly in said casing member including a coil support ring having a central opening a center return air tube said support ring retained on an upper flange of said return air tube so as to be substantially flush with the upper end thereof, said return air tube flange supporting said heater coil assembly in spaced relation below said burner disk whereby an upper plenum is defined between said burner disk and said heater coil assembly, said coil support ring having a convolute U-shaped groove in its upper face, a continuous spiral resistance coil supported in said convolute groove, vertical air passages providing communication between said groove and a lower plenum whereby air from said lower plenum flows through said air passages and is heated by said heating coil as it flows into said upper plenum, supply air outlet means connecting said upper plenum with said air circulation space, air impelling means in the form of a centrifugal fan having forwardly curved blades located in spaced relation below said heater coil assembly, stator means in the form of stationary forwardly curved vanes fixedly supported between parallel horizontal plates defining said lower plenum between said stator means and said heater coil assembly, return air passage means connecting said air circulating space with said lower plenum, said centrifugal fan operative for recirculating air serially from said lower plenum, through said heater coil assembly to said upper plenum, and then to said air circulation space for heating the utensil, whereby the flow of air from said centrifugal fan blades to said stator vanes is changed from an outwardly directed tangential swirl to a radially inward and thence upwardly directed flow of air into said lower plenum such that the resultant pressure in said lower plenum is increased to thereby provide a sufficient air mass flow to said air circulation space to maximize the convection rate of heat transfer along the plane of a utensil bottom supported on said surface cooking unit, and means for adjusting said burner disk relative to the plane of a utensil bottom supported on said supporting means to change said predetermined distance thereby to vary the air mass flow to said air circulation space.

Claim 16

The surface heating unit of claim 12 including an alternating current power supply for energizing said resistance coil, said power supply having first and second conductors, bimetal switch means connected in series circuit with said first conductor for controlling said resistance coil in accordance with a predetermined operating temperature selection, temperature sensing means in said upper plenum for controlling said power supply in accordance with with a preselected maximum temperature in said upper plenum, said temperature sensing means including ta thermocouple sensing device for generating a voltage proportional to said preselected maximum temperature in said upper plenum, semiconductor switch means in the form of a silicon-controlled rectifier bank in series with said power supply, said rectifier bank including a pair of opposed silicon-controlled rectifiers in parallel with said second conductor, each of said silicon-controlled rectifiers including a gate electrode, a diode connected between said power supply and each said gate electrode whereby each said silicon-controlled rectifier is rendered conductive during one half-cycle of the current from said power supplY, relay contact means in series with said temperature sensing means interposed between said silicon-controlled rectifiers wherein said relay is operative to open and close the gate circuit of said silicon controlled rectifiers on each half-cycle of current from said power supply and potentiometer means in series with said relay contact means for adjusting the flow of current through said relay contact means to limit the air temperature in said upper plenum to the desired maximum value.