GB1559703A

GB1559703A - Forced convection ovens

Info

Publication number: GB1559703A
Application number: GB2522176A
Authority: GB
Original assignee: Laurent J H
Current assignee: Laurent J H
Priority date: 1975-06-17
Filing date: 1976-06-17
Publication date: 1980-01-23
Also published as: FR2315062A1; DE2627094A1; FR2315062B1

Description

(54) IMPROVEMENTS IN OR RELATING TO FORCED CONVECTION OVENS (71) I, JEAN-HUBERT LAURENT, of 1 bis Rue du Printemps, 78230 Le Pecq, France, of French nationality, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to improvements in forced convection ovens which are suitable for cooking, for thermal regeneration, such as, for reheating cooled or frozen food, or for maintaining food at its temperature of consumption. It also relates to all other partly or wholly alimentary or industrial uses for ovens of this type.

Known ovens of this type are in the form of cabinets or enclosures in which air is circulated by means of vertical or horizontal suction and compression fans, the horizontal type of fans generally ensuring a better distribution of the heat, but at the cost of a much greater consumption of energy.

The oven according to the invention relates to the first type and, in most applications, particularly for thermal regeneration and the permanent maintenance of heat, allows a more balanced temperature to be obtained with a much lower consumption of energy, for an equal cooking or heating period.

Tn accordance with the invention, there is provided an oven, for cooking or thermal regeneration, comprising an enclosure closable by at least one hinged door, a semicircular or polygonal cross-sectioned casing which extends vertically within the enclosure and projects from a wall thereof, the casing having apertures and containing air heating means, a fan arranged to blow air downwardly through the casing, and a perforated baffle which is adjustable for controlling the amount of heated air blown through the apertures in an upper part of the casing.

The oven exterior is preferably of stainless steel, or other poor heat conductive material, whilst the interior is made of a metal which is a good thermal conductor, such as an aluminium alloy or aluminised steel sheet, thereby allowing a rapid and uniform diffusion of heat within the oven. The exterior and interior side walls may only be connected to one another by their edges at the openable side of the oven, so as to limit the conductive passage of heat to the exterior.

Thus, thermal insulation provided by the space separating the walls can be quite effective.

The base of the enclosuse and an outer frame ensure satisfactory rigidity of the oven.

The doors are hinged to joints of aluminium which ensure rapid dissipation of heat.

Orifices of larger dimensions than those of the casing apertures may be provided at the base of the casing to effect a large throughput of heated air and, thus, compensate for the customary temperature differential between the top and bottom of the oven.

The adjustable, preferably slidably, baffle, whose perforations can overlie the apertures in the casing, is used to reduce or increase the throughput of heated air at the upper part of the casing, and hence increase or reduce the heated air throughput of the orifices at the base of the casing, as required.

Between the casing and respective side walls of the enclosure, oblique or curved deflection plates can direct the flow of heated air from the casing apertures to pass between receptacles located within the enclosure and containing food to be cooked or heated. The natural upward convection of the heated air is accelerated by the suction of the fan acting through the intermediary of an air inlet located beneath the base and having apertures which are orientated and dimensioned as a function of the dimensions of the oven. Moreover, the flow of heated air leaving the casing, via the apertures and, optionally, the base orifices, and directed by the deflector plates is secondarily reheated by the radiation of heat from the casing, which is preferably also made of a good heat conductive material.After passing between the food-containing receptacles, it rises according to a predetermined path towards the suction inlet, of the fan while continuing to return and recycle any unused heat.

The deflector plates take part in the ther mal efficiency of the oven, by preventing excessive heating of the interior walls and losses to the exterior, whilst the casing, which is in contact on at least three sides with the heated air contained in the enclosure, dissipates, to a maximum degree, the heat which is produced in it by the heating means.

The fan, which is preferably installed above the enclosure, is independently controlled in order to ensure continual agitation and circulation of the air within the enclosure and, thus, the homogeneity of the interior temperature, even if a temperature control mechanism, such as a thermostat or simmerstat, has discontinued the heating, once the required temperature is attained or operates at the end of the heating period provided.

In one embodiment, an enclosure with a fixed base floor is provided with slide bars for receiving either plates of given dimensions or receptacles or trays carrying plates covered with lids, perforated covers or the like.

In another embodiment, the floor of the enclosure is fixed and a trolley, having supports provided with an array of slide bars, for receiving food receptacle-supporting trays, and a U-shaped base, is arranged such that, when the slide bars are located within the enclosure, one arm of the U-shaped base is located above the enclosure floor within the enclosure and the other arm of the U-shaped base is located below the enclosure floor outside the enclosure. The door or doors close up to the trolley after a detachable operating handle of the trolley has been removed therefrom. This handle may be a tube of circular cross-section which is detachably fixed between two supporting tubes on the trolley which may be of square cross section or of any other suitable form.

In yet another embodiment, the floor of the enclosure is constituted by the base of a trolley which is removably locatable within the enclosure and has supports provided with an array of slide bars for receiving food receptacle-supporting trays.

In these embodiments, enclosed panniers, utilised for the storage of prepared dishes in a cold chamber for example, can be stacked directly on the base platform of the trolley.

The plate-carrying shelves or panniers can be attached to or removed from the walls of the enclosure for storage purposes and for cleaning the oven.

Still another embodiment comprises a double enclosure in which respective casings project from the opposed sides of a partition wall separating the two enclosures. Air is blown into the two enclosures from the respective casings. This form of construction principally concerns movable trolley ovens intended for hospital service, for use in a self-service section, the dimensions of the plates and the enclosure being interrelated and the oven having its contents accessible from the two sides. The dimensions of these ovens are limited by the nature of the contents, the weight and other factors. They can advantageously be of small dimensions but can be capable of assembly together or with plate-carrying members, with handles which can be utilised for stabilising or moving the trolley.The handle mounting arrangements, by way of example, can be constituted by two arms hinged to fixed supports which are connected by a projecting cross tube for gripping purposes and which comprise perpendicular handles which are slightly curved so that they can be inserted into square tubular sections mounted on the trolley at the required height. A rod fixed perpendicularly beneath the cross tube, when at rest, is held by a blade spring of omega shape fixed to the body of the trolley. A fixed wheel mounted below the centre of the assembly can guide two trolley ovens having pivotable castor type wheels, if required.

In all the various embodiments, the external and interior walls are made rigid by the deflector plates and form an inner enclosure without any thermal transfer therebetween.

Maintenance of dishes at the temperature of consumption is ensured in two ways: if the oven is intended to remain in use permanently, the dishes can be transferred, for example, on to a carriage for the purposes of their distribution, and kept hot by regulating the thermostat to the desired temperature and a timer mechanism for maximum duration, the fan rotating continuously and regulating the distribution of heat; if the oven is mounted on a trolley and is intended for mobile service, such as on a railway platform or in a service area, there can be carried out, before, during or after the recirculation of heat, preheating of an auxiliary, natural convector in the form of a heat storage device, installed beneath the base of the enclosure. Under this base but above the framework of the trolley, a lower sheet is located which is covered with a heat insulator resistant to high temperature (glass wool or fibre or the like) above which are mounted either resistance heaters provided in blocks made of a refractory cement or reinforced heater elements covered for example with blocks of a refractory cement or other dense material, which may be provided with orifices facilitating diffusion of heat or which may be located between blocks for storing heat. In the latter arrangement, the heat storage blocks have the form of cement blocks fixed to the base of the enclosure and disposed alternately with the heater elements, in order to collect the radiant heat or that derived from the heated air blown through the lower part of the casing.The number of these blocks is variable according to the dimensions of the oven and possibly the number of resistance heaters, but advantageously there is a block at each side of the casing, in order to recover the heat instead of preventing its wastage. The reinforced heater elements are advantageously mounted on supports serving to locate them on the base of the oven or in the casing, a sheet of polished metal serving as a heat reflector being located between the supports. The wastage of heat is thus reduced and is concentrated towards the most favourable zone of the internal wall of the base or the casing which transmits it through to the oven enclosure per se.

The base itself is made of a metal which is a good conductor of heat and comprises orifices to accelerate the natural convection of the heat stored in the storage service.

This oven continuously renews, through the base, the heated air which escapes towards the top of the oven, depending upon the amount of opening of the doors.

A variant of this arrangement consists in providing between the base of the casing and the base on which it rests a horizontal aperture which can if desired be closable by a rotary or slide system, allowing part of the heated air to be passed over the heat storage block, which thus allows auxiliary heating to be dispensed with.

Fig. 1 is a perspective view of a first embodiment of oven; Fig. 2 is a plan view, in partial section, of the oven shown in Fig. 1; Fig. 3 is a perspective view of a second embodiment of oven; Fig. 4 is a perspective view of a third embodiment of oven; Fig. 5 is a partial elevational view of a fourth embodiment of oven subdivided into two heating compartments; Fig. 6 is a plan view, in partial section, of the embodiment of oven shown in Fig. 5.

Fig. 7 is an exploded, perspective view of a heat storage arrangement for use in the embodiment of oven shown in Figs. 5 and 6; and Fig. 8 is an elevational view of a fifth embodiment of oven having two mobile heating compartments detachably securable to each other.

Referring to Figs. 1 and 2, a forced convention oven comprises a cabinet I having two side walls, a back wall, a top and a base and closable by a pair of doors hinged to the front portions of respective side walls.

A vertically-extending rectangularly crosssectioned casing 2 inside the cabinet I projects forwardly from the cabinet back wall and contains heating elements 3. Apertures 4 are provided in the front wall and two side walls of the casing 2 and a larger, rectangular orifice 5 is provided at the bottom of each of these walls, adjacent the base of the cabinet 1.

Air is blown downwardly inside the casing 2 over the heating elements 3 by means of a fan 8, mounted in an air inlet housing 9, and passes as hot air through the apertures 4 and orifices 5 into the interior of the cabinet 1 proper. The orifices 5 at the base of the casing 2 provide a high throughput of heated air to compensate for the customary temperature differential between the top and bottom of the cabinet 1, as hereinbefore described. To further compensate for this temperature differential, perforated baffles 6 are slidably mounted to adjust the hot air passing through the apertures 4 at the upper part of the casing.

Extending between the rear of the casing 2 and the side walls of the cabinet 1 are oblique deflector plates 7 which guide the hot air between food receptacles stacked in the cabinet.

The natural, upward connection of the hot air in the cabinet 1 is accelerated by the suction of the fan 8 located in the housing 9.

The hot air leaving the casing 2, via the apertures 4 and orifices 5, after passing around and between the stacked food receptacles, rises towards the inlet housing 9 for subsequent recycling.

The deflectors 7 assist in the efficiency of the oven by reducing heat losses through the back of the cabinet 1, whilst the casing 2, which is in contact on these sides with the air in the cabinet 1, transfers the heat generated therein by the heating elements 3 to the air in the cabinet.

The cabinet may be provided with slide bars, as shown in dashed outline in Fig. 2, for receiving shelves or trays supporting receptacles containing food to be heated in the oven.

In the second embodiment, shown in Fig.

3, the oven operates on the same principle as that of the oven described with reference to Figs. 1 and 2, except that the optional slide bars, for receiving shelves or trays supporting food receptacles, are mounted on a trolley 14 which can be pushed up to and into the cabinet 1 such that the bars, supporting receptacles containing food to be heated, are located within the cabinet, whilst the wheeled base 11 of the trolley is located outside the cabinet. The front of the base of the cabinet 1 is recessed for receiving the trolley 14 and a detachable handle 12 is locatable in suitably shaped clips 13 provided on the trolley. After the slide bars of the trolley 14, and associated shelves or trays supporting food-containing receptacles, have been located within the cabinet 1, the handle 12 is detached from the trolley and the oven door closed.

The third embodiment of oven, shown in Fig. 4, is constructed, and operates, on the same principle as that of the oven described with reference to Fig. 3, except that a base 15 of the trolley 14 serves as the base of the cabinet 1, when the trolley has been received therein, the cabinet having no permanent base of its own, such as the base 10 of Fig.

3. Also, the trolley 14 of the oven shown in Fig. 4 has slide bars, for receiving shelves or trays (not shown) supporting food receptacles, which extend transversely with respect to the interior of the oven, when received therein, whereas the slide bars of the trolley shown in Fig. 3 extend parallel to the sides of the oven, when inserted therein.

Furthermore, the oven shown in Fig. 4 has a pair of closable doors, whereas that shown in Fig. 3 has a single closable door.

Referring now to Figs. 5, 6 and 7, a fourth embodiment of wheeled, forced convection oven comprises a cabinet la separated into two compartments by a central rectangularly cross-sectioned casing 2 divided by a partition 16 which extends between a pair of opposed walls of the cabinet. The casing 2 is apertured so that heated air can be blown by a fan (not shown) through the apertures, as indicated by the arrows, into the two compartments.

Each compartment is provided with a door, as shown in Fig. 6, whereby access to either side of the cabinet 1 is facilitated.

Located beneath the base floor of the two compartments is an auxiliary heater 19 in the form of a storage heater comprising a base 20 above which is mounted a heating element 21 covered with a perforated slab 22 through which heated air can diffuse upwardly by convection. The base floor of each compartment is constituted by a plate 23 having a stepped area provided with apertures 24 through which occurs natural convection of heat stored in the slab 22. The slab 22 absorbs both radiant heat from the heating element 21 and also some conductive heat from the heated air being blown through the lower orifices of the apertured casing 2 adiacent the slab.

Fig. 8 shows a fifth embodiment of forced convection oven comprising a pair of ovens detachably securable together on respective wheeled bases 17, the bases being detachably connectable together by means of a standard hook and eye coupling, as shown. Each oven is provided with a pair of handles 18.

Once again, each oven is provided with a perforated casing through which heated air is blown downwardly to heat food supported upon trays or shelves located upon opposed transverse slide bars. The right hand oven of Fig. 8 has a pair of upper and lower closable doors, whereas the left hand oven has a single, full-length door.

WHAT I CLAIM IS:- 1. An oven, for cooking or thermal regeneration, comprising an enclosure closable by at least one hinged door, a semi-circular or polygonal cross-sectional casing which extends vertically within the enclosure and projects from a wall thereof, the casing having apertures and containing air heating means, a fan arranged to blow air downwardly through the casing and a perforated baffle which is adjustable for controlling the amount of heated air blown through the apelture in an upper part of the casing.

2. An oven according to claim 1, comprising deflectors disposed obliquely with respect to the casing.

3. An oven according to claim 1 or 2 comprising a trolley whose base constitutes that of the enclosure and which is removably locatable in the enclosure and which has supports provided with an array of slide bars for receiving food receptacle supporting trays.

4. An oven according to claim 1 or 2 comprising a trolley, having supports provided with an array of slide bars, for receiving food receptacle supporting trays, and a U-shaped base which is arranged such that, when the slide bars are located within the enclosure, one arm of the U-shaped base is located above the enclosure base within the enclosure and the other arm of the U-shaped base is located below the enclosure base outside the enclosure.

5. An oven according to claim 3 or 4, in which the trolley has a removable handle which can be removed when the slide bars are located in the enclosure.

6. An oven according to any preceding claim on whose base trays supporting food to be cooked or thermally regenerated can be stacked.

7. An oven according to claim 1 or 2 or claim 6, when dependent upon claim 1 or 2, in which shelves are detachably secur-able to internal walls of the enclosure and can be readily detached therefrom.

8. An oven according to any preceding claim comprising two enclosures whose respective apertured casings are separated by a partition wall dividing the two enclosures.

9. An oven according to claim 8, which is mounted on wheels and comprises a heat storage device located beneath the bases of the enclosures and consisting of either resistance elements embedded in heat retaining material, whereby natural convection of heat from the heat storage device takes place through apertures which are inaccessible to any liquids spilt into the enclosure bases.

10. An oven according to claim 9, in which the resistance elements are mounted on a reflective sheet which reflects radiation towards the bases of the enclosures.

11. An oven according ta claim 9 or 10, in which a horizontal aperture, which may or may not be - regulatable by means of

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. same principle as that of the oven described with reference to Fig. 3, except that a base 15 of the trolley 14 serves as the base of the cabinet 1, when the trolley has been received therein, the cabinet having no permanent base of its own, such as the base 10 of Fig. 3. Also, the trolley 14 of the oven shown in Fig. 4 has slide bars, for receiving shelves or trays (not shown) supporting food receptacles, which extend transversely with respect to the interior of the oven, when received therein, whereas the slide bars of the trolley shown in Fig. 3 extend parallel to the sides of the oven, when inserted therein. Furthermore, the oven shown in Fig. 4 has a pair of closable doors, whereas that shown in Fig. 3 has a single closable door. Referring now to Figs. 5, 6 and 7, a fourth embodiment of wheeled, forced convection oven comprises a cabinet la separated into two compartments by a central rectangularly cross-sectioned casing 2 divided by a partition 16 which extends between a pair of opposed walls of the cabinet. The casing 2 is apertured so that heated air can be blown by a fan (not shown) through the apertures, as indicated by the arrows, into the two compartments. Each compartment is provided with a door, as shown in Fig. 6, whereby access to either side of the cabinet 1 is facilitated. Located beneath the base floor of the two compartments is an auxiliary heater 19 in the form of a storage heater comprising a base 20 above which is mounted a heating element 21 covered with a perforated slab 22 through which heated air can diffuse upwardly by convection. The base floor of each compartment is constituted by a plate 23 having a stepped area provided with apertures 24 through which occurs natural convection of heat stored in the slab 22. The slab 22 absorbs both radiant heat from the heating element 21 and also some conductive heat from the heated air being blown through the lower orifices of the apertured casing 2 adiacent the slab. Fig. 8 shows a fifth embodiment of forced convection oven comprising a pair of ovens detachably securable together on respective wheeled bases 17, the bases being detachably connectable together by means of a standard hook and eye coupling, as shown. Each oven is provided with a pair of handles 18. Once again, each oven is provided with a perforated casing through which heated air is blown downwardly to heat food supported upon trays or shelves located upon opposed transverse slide bars. The right hand oven of Fig. 8 has a pair of upper and lower closable doors, whereas the left hand oven has a single, full-length door. WHAT I CLAIM IS:-

1. An oven, for cooking or thermal regeneration, comprising an enclosure closable by at least one hinged door, a semi-circular or polygonal cross-sectional casing which extends vertically within the enclosure and projects from a wall thereof, the casing having apertures and containing air heating means, a fan arranged to blow air downwardly through the casing and a perforated baffle which is adjustable for controlling the amount of heated air blown through the apelture in an upper part of the casing.

a baffle, is provided between the base of the enclosure and the casing in order to effect heating of the storage device by means of heated air which is blown through the casing and which is independent of the resistance elements.

12. An oven according to claim 9, 10 or 11, comprising means for the attachment, at the height of handles, of a plurality of hinged members which thus permit the coupling together of two or more of the ovens.

13. An oven according to claim 1, substantially as herein described with reference to and as shown in Figs. 1 and 2, Figs. 3 and 4 Figs. 5 to 7 or Fig. 8 of the accompanying drawings.