GB1598333A

GB1598333A - Electrical heating device for a food-containing unit

Info

Publication number: GB1598333A
Application number: GB5128677A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-12-09
Filing date: 1977-12-09
Publication date: 1981-09-16

Description

(54) AN ELECTRICAL HEATING DEVICE FOR A FOOD-CONTAINING UNIT (71) We, EDWARD McINLAY MOF- FAT and ELIZABETH MOFFAT, both of SA Ford Road, Bonnybridge, Scotland, REID MOFFAT, of 8 Arnothill Gardens, Falkirk, Scotland, and ROBERT MOFFAT of 15 Highland Dykes Drive, Bonnybridge, Scotland, all British subjects, trading as E.

& R. MOFFAT, a British Company of Bonnymuir Works, Bonnybridge, Stirlingshire, FK4 2BS, Scotland, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: This invention relates to an electrical heating device for a food-containing unit and to a food-containing unit incorporating such a heating device.

According to one aspect of the invention an electrical heating device for a foodcontaining unit comprises a housing subdivided internally by partitioning means into a heating chamber, having at least one air outlet and containing an electrical heating element, and an air inlet chamber having at least one air inlet, the partitioning means having an opening therethrough between the two chambers, and a fan for drawing air in through said air inlet(s) and forcing a stream of air over said heating element and through said air outlet(s), the air inlet(s) and the air outlet(s) being angularly spaced apart substantially 90" with respect to the flow direction of said stream through the opening so that flow(s) of air drawn in through said air inlet(s) is (are) substantially perpendicular to flow(s) of air expelled through said air outlet(s), and being spaced apart in the direction of flow of air through the opening between the two chambers.

Suitably the housing comprises a substantially parallelepipedic casing in which the partitioning means is arranged so that both the heating chamber and the air inlet chamber are also substantially parallelepipedic.

Typically the air inlet chamber is open ended to provide a pair of air inlets, and the heating chamber is also open ended to provide a pair of air outlets.

A thermostat for controlling the operation of the heating element may be provided in the air inlet chamber, preferably adjacent the, or one of the, air inlets.

The fan may be provided with two sets of blades, one set of blades being for providing the flow of air between said air inlet(s) and said air outlet(s), and the other set of blades being for directing cooling air on to the motor driving the fan. Suitably a perforated casing surrounds the motor of the fan enabling cooling air to be drawn in through the perforations.

The heating element may be of any suitable shape, but conveniently is in spiral form.

According to another aspect of the invention there is provided a food-containing unit incorporating a heating device according to said one aspect of the invention.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a heating device according to the invention, Figures 2 and 3 are side and end sectional views, respectively, of a food-warming unit incorporating the heating device shown in Figure 1, and Figure 4 is a view on an enlarged scale of part of Figure 3 showing the heating device.

Figure 1 shows a heating device, generally designated by the reference numeral 1, comprising a housing provided by a substantially right parallelepipedic casing 2, which is divided internally by a partition 3 into a heating chamber 4 and an air inlet chamber 5, each of substantially right parallelepipedic shape, and a perforated, substantially right parallelepipedic casing 6 mounted on the casing 2.

An axial-flow fan 7, comprising a pair of axially spaced-apart blades 8 and 9 each fixed on an axle 17 driven by an electric motor 10, is positioned within the housing of the device 1, the motor and blade 9 being positioned in the perforated casing 6, and the blade 8 being positioned coaxially within a circular opening 11 provided in the partition 3. A spiral electric heating element 30 is positioned within the heating chamber 4 coaxial with the fan 7 and the opening 11.

The air inlet chamber 5 has a pair of opposed open ends 12 and 13 serving as air inlets for the intake of air into the heating device 1. As seen in Figure 1 these air inlets are provided at the sides of the heating device 1. The heating chamber 4 also has a pair of open ends 14 and 15 which serve as air outlets for the outflow of heated air from the heating device 1, the open ends 12 and 13 being spaced apart from the open end 14 and 15 in the axial direction of the fan 7.

However the open ends 14 and 15 are angularly spaced apart substantially 90 , as viewed in the axial direction of the fan 7, from the open ends 12 and 13, the open ends 14 and 15 being provided at the top and bottom, respectively, of the heating device 1 (as viewed in Figure 1).

In use of the heating device 1, the blade 8 of the axial-flow fan 7 draws in air through the air inlets provided by the open ends 12 and 13 of the air inlet chamber 5 and passes the air in a generally axial direction through the opening 11 towards the heating element 30. The air is then deflected over the heating element 30 and expelled through the air outlets provided by the open ends 14 and 15 of the heating chamber 4. It will thus be appreciated that, viewed in the axial direction of the fan 7, the flow of air drawn into the heating device 1 is angularly spaced from the flow of heated air passed out of the device. In order to prevent over-heating of the motor 10 of the fan 7, the blade 9 draws cooling air through the perforations of the casing 6 and blows the cooling air onto the motor 10.It will be appreciated that an opening 18 is provided in the wall 19 of the casing 2 through which the axle 17 of the motor 10 passels. In order to prevent or deter the flow of cooling air through this opening 18 and into the air inlet chamber 5 it is desirable to make the clearance between the axle 17 and opening 18 as small as possible and/or to mount the casing of the motor 10 against a part of the wall 19 which surrounds the opening 18.

The heating element 30 is suitably thermostatically controlled by means of a thermostat 20 positioned in the air inlet chamber 5 adjacent one of its open ends 13. The thermostat is thus shielded by the partition 3 from the direct radiant heat of the heating element 30.

Figures 2 to 4 show a wheeled foodcontaining unit 21 in the form of a hotcupboard which incorporates the heating device 1. The unit 21 has heat-insulating side walls 22, a top 23, a bottom 24, and a door 25. A gasket 26 is provided around the frame of the heat-insulating door 25 to seal the door against its frame when the door is closed thereby preventing the outflow of heated air from the interior of the unit 21. The device 1 is sealingly mounted within a rectangular opening 27 provided in the heat-insulating bottom 24 and is arranged to heat (or at least reduce the cooling rate of) articles or food resting on open mesh shelves 28 and 29 provided in the unit 21.A control unit 31 is provided in the unit 21 which controls the heating device 1 enabling the unit 21 to be rapidly and efficiently heated and thereafter maintained at a balanced, even and relatively low temperature (e.g. up to 200"F) with positive control against overheating.

It will be appreciated that in a foodcontaining unit provided with a heating device 1, the air in the food-containing unit is continuously recycled through the heating unit thereby gradually raising the temperature of air in the unit until a desired pre-set temperature is reached. The re-introduction of heated air through the heating device 1 minimises the energy requirement of the device and can result in an energy saving of at least 50% over conventional heating devices. The recycling of air also reduces the drying effect of the air on the food articles within the unit 21.

The heating device 1 may be incorporated in other types of food-containing units, e.g.

cabinets, trolleys or service counters.

In another embodiment of the invention a water tray may be provided in the food containing unit to further reduce the drying effect of the air on foodstuffs in the unit.

WHAT WE CLAIM IS: 1. An electrical heating device for a food-containing unit comprising a housing sub-divided internally by partitioning means into a heating chamber, having at least one air outlet and containing an electrical heating element, and an air inlet chamber having at least one air inlet, the partitioning means having an opening therethrough between the two chambers, and a fan for drawing air in through said air inlet(s) and forcing a stream of air over said heating element and through said air outlet(s), the air inlet(s) and the air outlet(s) being angularly spaced apart substantially 90" with respect to the flow direction of said stream through the opening so that flow(s) of air drawn in through said air inlet(s) is (are) substantially perpendicular to flow(s) of air expelled through said air outlet(s), and being spaced apart in the direction of flow of air through

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the casing 2. An axial-flow fan 7, comprising a pair of axially spaced-apart blades 8 and 9 each fixed on an axle 17 driven by an electric motor 10, is positioned within the housing of the device 1, the motor and blade 9 being positioned in the perforated casing 6, and the blade 8 being positioned coaxially within a circular opening 11 provided in the partition 3. A spiral electric heating element 30 is positioned within the heating chamber 4 coaxial with the fan 7 and the opening 11. The air inlet chamber 5 has a pair of opposed open ends 12 and 13 serving as air inlets for the intake of air into the heating device 1. As seen in Figure 1 these air inlets are provided at the sides of the heating device 1. The heating chamber 4 also has a pair of open ends 14 and 15 which serve as air outlets for the outflow of heated air from the heating device 1, the open ends 12 and 13 being spaced apart from the open end 14 and 15 in the axial direction of the fan 7. However the open ends 14 and 15 are angularly spaced apart substantially 90 , as viewed in the axial direction of the fan 7, from the open ends 12 and 13, the open ends 14 and 15 being provided at the top and bottom, respectively, of the heating device 1 (as viewed in Figure 1). In use of the heating device 1, the blade 8 of the axial-flow fan 7 draws in air through the air inlets provided by the open ends 12 and 13 of the air inlet chamber 5 and passes the air in a generally axial direction through the opening 11 towards the heating element 30. The air is then deflected over the heating element 30 and expelled through the air outlets provided by the open ends 14 and 15 of the heating chamber 4. It will thus be appreciated that, viewed in the axial direction of the fan 7, the flow of air drawn into the heating device 1 is angularly spaced from the flow of heated air passed out of the device. In order to prevent over-heating of the motor 10 of the fan 7, the blade 9 draws cooling air through the perforations of the casing 6 and blows the cooling air onto the motor 10.It will be appreciated that an opening 18 is provided in the wall 19 of the casing 2 through which the axle 17 of the motor 10 passels. In order to prevent or deter the flow of cooling air through this opening 18 and into the air inlet chamber 5 it is desirable to make the clearance between the axle 17 and opening 18 as small as possible and/or to mount the casing of the motor 10 against a part of the wall 19 which surrounds the opening 18. The heating element 30 is suitably thermostatically controlled by means of a thermostat 20 positioned in the air inlet chamber 5 adjacent one of its open ends 13. The thermostat is thus shielded by the partition 3 from the direct radiant heat of the heating element 30. Figures 2 to 4 show a wheeled foodcontaining unit 21 in the form of a hotcupboard which incorporates the heating device 1. The unit 21 has heat-insulating side walls 22, a top 23, a bottom 24, and a door 25. A gasket 26 is provided around the frame of the heat-insulating door 25 to seal the door against its frame when the door is closed thereby preventing the outflow of heated air from the interior of the unit 21. The device 1 is sealingly mounted within a rectangular opening 27 provided in the heat-insulating bottom 24 and is arranged to heat (or at least reduce the cooling rate of) articles or food resting on open mesh shelves 28 and 29 provided in the unit 21.A control unit 31 is provided in the unit 21 which controls the heating device 1 enabling the unit 21 to be rapidly and efficiently heated and thereafter maintained at a balanced, even and relatively low temperature (e.g. up to 200"F) with positive control against overheating. It will be appreciated that in a foodcontaining unit provided with a heating device 1, the air in the food-containing unit is continuously recycled through the heating unit thereby gradually raising the temperature of air in the unit until a desired pre-set temperature is reached. The re-introduction of heated air through the heating device 1 minimises the energy requirement of the device and can result in an energy saving of at least 50% over conventional heating devices. The recycling of air also reduces the drying effect of the air on the food articles within the unit 21. The heating device 1 may be incorporated in other types of food-containing units, e.g. cabinets, trolleys or service counters. In another embodiment of the invention a water tray may be provided in the food containing unit to further reduce the drying effect of the air on foodstuffs in the unit. WHAT WE CLAIM IS:

1. An electrical heating device for a food-containing unit comprising a housing sub-divided internally by partitioning means into a heating chamber, having at least one air outlet and containing an electrical heating element, and an air inlet chamber having at least one air inlet, the partitioning means having an opening therethrough between the two chambers, and a fan for drawing air in through said air inlet(s) and forcing a stream of air over said heating element and through said air outlet(s), the air inlet(s) and the air outlet(s) being angularly spaced apart substantially 90" with respect to the flow direction of said stream through the opening so that flow(s) of air drawn in through said air inlet(s) is (are) substantially perpendicular to flow(s) of air expelled through said air outlet(s), and being spaced apart in the direction of flow of air through

the opening between the two chambers.

2. An electrical heating device according to claim 1, in which the housing comprises a substantially parallelepipedic casing in which the partitioning means is arranged so that both the heating chamber and the air inlet chamber are also substantially parallelepipedic.

3. An electrical heating device according to claim 2, in which the air inlet chamber is open ended to provide a pair of air inlets, and the heating chamber is also open ended to provide a pair of air outlets.

4. An electrical heating device according to any one of the preceding claims, comprising a thermostat for controlling the operation of the heating element provided in the air inlet chamber.

5. An electrical heating device according to claim 4, in which the thermostat is located adjacent the, or one of the, air inlets.

6. An electrical heating device according to any one of the preceding claims, in which the fan is provided with two sets of blades, one set of blades being for providing the flow of air between said air inlet(s) and said air outlet(s), and the other set of blades being for directing cooling air on to the motor driving the fan.

7. An electrical heating device according to claim 6, comprising a perforated casing surrounding the motor of the fan for enabling the said other set of blades to draw cooling air in through the perforations.

8. An electrical heating device according to any one of the preceding claims, in which the heating element is in spiral form.

9. An electrical heating device constructed and arranged substantially as herein described with reference to, and as illustrated in, Figure 1 of the accompanying drawings.

10. A food containing unit incorporating a heating device according to any one of the preceding claims.

11. A food containing unit constructed and arranged substantially as herein decribed with reference to, and as illustrated in, Figures 2 to 4 of the accompanying drawings.