GB2056249A - Improvements in ovens for baking foodstuffs - Google Patents

Abstract

An oven for baking foodstuffs includes a heating chamber bounded by generally vertical walls and has a carousel mounted therein for rotation about a generally vertical axis. There are two opposed walls each having at least one door. There may be two other opposed walls one of which contains at least a plurality of adjustable hot air supply orifices and the other of which contains at least a plurality of air extraction orifices. Each door may be associated with a position sensor, and an interlock is provided to prevent the carousel being rotated except when opposite doors are shut.

Description

SPECIFICATION Improvements in ovens for baking foodstuffs This invention relates to an oven for baking foodstuffs. The oven disclosed herein is particularly, although not exclusively, useful for baking meat products such as sausage rolls, prepared chicken portions, and meat pies.

There has been proposed, in British Patent Specification No. 855029, an oven for bakery use which includes a rotary turntable disposed in an oven chamber, there being means whereby racks of food products can be loaded onto the rotary turntable. Baking is achieved by supplying hot air to and extracting it from, the baking chamber. The air may be heated through the agency of a gas or oil burner and a heat exchanger. This design of oven has been found to be successful in many bakery applications, for example, baking bread and pastries, and it would be desirable to increase the versatility of the oven.

According to the present invention, there is provided an oven for baking foodstuffs which includes a heating chamber bounded by generally vertical walls, a turntable or carousel herein called a carousel mounted therein for rotation about a generally vertical axis, there being two opposed walls each having at least one door therein.

The oven preferably comprises a plurality of rack-receiving trays disposed around its axis of rotation and located at a level adjacent to the oven floor, each of the trays being slightly less in width than each of the doors.

The doors may be located opposite to one another and symmetrically in relation to the carousel rotation axis.

The oven may have two other opposed walls one of which contains at least a plurality of hot air supply orifices and the other of which contains at least a plurality of air extraction orifices.

The oven preferably includes a motor for rotating the carousel associated with control system having a manually-operable control means adjacent to the exterior of each door and arranged to effect a relatively slow rotation of the carousel for so long as the control means is operated. This is herein called an "inching" control and it is provided to allow adjustment of the position of the carousel so that a given sector of it is in accurate registry with one or other door. This permits racks carrying a foodstuff to be baked to be transferred, e.g. wheeled in, through one door and directly onto the carousel. The dther door permits baked foodstuff items to be removed directly into a room maintained under relatively sterile conditions.The control system preferably includes an interlock whereby neither of the two control means is effective to cause such rotation if either of the doors is open. For this purpose each door is provided with a position sensor such as a limit switch.

The invention will be better understood from the following particular description of an illustrative and non-limiting embodiment, given with reference to the accompanying schematic drawings, in which: Figure 1 is a plan view of one example of oven according to the invention; Figure 2 is a front elevation view, partly in section, of the oven of Figure 1; Figure 3 is a plan view taken from above showing the fan arrangements and hot air supply ducts; Figure 4 is a block diagram illustrating the general principal of part of an electrical control system of the oven; and Figure 5 is a diagrammatic vertical crosssection showing the arrangement of a steamextraction canopy.

When baking food products containing meat, it is a sound principle of hygiene and is moreover the subject of a regulation or directive of the European Economic Commission that the working area in which raw meat is handled or prepared should be entirely and totally separated from the working area in which cooked meat is handled, packed, and dispatched.

Moreover, there should be no transfer of personnel from one of the areas to the other without taking the strictest precautions as to hygiene.

An important feature of the design according to the present invention is that the oven has a heating chamber with an entry door and an exit door.

Referring to the figures, the illustrated oven has a front wall 10, a rear wall 12, and side walls 14 and 1 6. These walls define a heating chamber which is generally rectangular but it will be understood that an oven according to the invention could be constructed with a heating chamber which is other than rectangular. The heating chamber has an entry door 1 8 and an exit door 20. Each of these can be swung about a vertical axis and firmly held closed by a respective handle 22, 24. These handles are pivotable about respective axes 26 and co-operate with respective wedges 28, 30 on the doors 18, 20. Adjacent to each door is a control button 32, 34 whose purpose will be described later. A main control panel 36 is carried by the wall 10.

The wall 14 is provided with a number of exit orifices leading to a space within which is located a heat exchanger 40. This is positioned adjacent an oil or gas burner or electric heating elements 42 which provides the source of heat to heat air which is circulated through the oven chamber. The heat exchanger 40 may be a shell and tube design of heat exchanger through the tubes of which the products of combustion from the burner 42 are passed, with the air from the oven chamber passing through the shell and being indirectly heated therein by heat transferred through the walls of the tubes of the heat exchanger. The air flow arrangements will be better understood from Figure 3 which will be described later.

The oven chamber 11 contains a rotary carousel whose main support is a vertical rotatable shaft 50 carried in bearings 52, 54 which are seen in Figure 2. The shaft 50 carries six trays 56 connected by suitable tie bars 58, 60 to the shaft 50. It is arranged that the trays 56 are generally horizontal and are at substantially the same horizontal level as the top of a step at the base of each of the two doors 18, 20. The trays 56 are intended to receive racks, which may be wheeled, designed to carry a plurality of layers of items to be baked. For this purpose each rack may include a plurality of vertically-spaced shelves upon which the items to be baked are placed. The shaft 50 is driven to rotate about a vertical axis by a gear box 62 driven by an electric motor 64. The bearing 54 is fully enclosed and its top surface is located above the floor of the oven.The floor of the oven may be arranged to slope towards one or more outlet orifices.

Referring now to Figures 2 and 3, these illustrate the arrangement of ducting for carrying heated air from the heat exchanger 40 across the top of the oven in ducts 80, 82, and into vertically downwardly extending ducts 84, 86. Each of the ducts 80, 82 contains a fan or blower 88, 90. The oven wall 16 is provided with a series of adjustable horizontal slots which communicate with the duct 84 and a second series of horizontal slots which communicate with the duct 86. These are the hot air entry slots into the oven chamber 11. Each slot is defined by a pair of flanges whose positions can be adjusted so as to allow the width of the slot, that is to say its vertical height, to be altered during initial setting up of the oven.In this way, during the initial setting up, the flow of hot air into the various regions of the oven chamber can be altered as necessary to achieve a balanced heating effect. For simplicity in Figure 3, the turntable or carousel, the doors, and the arrangements for removal of hot fat are not shown.

The main control panel 36, Figure 1, contains a control switch which governs the operation of the motor 64 in normal running. However for loading or unloading of the racks onto the carousel, the "inching" control buttons 32 and 34 can be used to effect small limited rotations of the carousel in order to bring a tray 56 properly into registry with the relevant door 1 8 or 20. For safety reasons, an interlock is provided to ensure that neither of the two inching control buttons can cause rotation of the carousel if both doors 1 8 and 20 are open.

Figure 4 illustrates the principle. A main power supply 100 is shown which feeds the motor 64 through the contacts 104 of a relay having a solenoid 106. The solenoid coil can be energised from the control system power supply 102 by way of inching push button 32 or inching push button 34. Associated with the door 1 8 there is a limit switch 108 which is closed only when the door 1 8 is closed, and associated with the door 20 there is a limit switch 110 which is closed only when the door 20 is closed. Consequently, depression of the.

inching push button 32 or 34 can only energise the solenoid 106 when one opposite limit switch 108 or 110 is closed. Consequently rotation of the carousel when both doors are open cannot be effected. A separate electrical arrangement, not shown, is provided for controlling the rotation of the carousel during normal baking operation. The remainder of the oven control system, including its thermostats, is not shown for reasons of simplicity of explanation.

Reverting to Figure 1, the oven including its heat exchanger structure 40 and its ducting structure 84, 86 is preferably disposed in and sealed into a gap between two walls 116, 11 8 or against a wall with a suitably sized aperture in it, defining a boundary between a work area 120 where uncooked meat is handled, and a work area 122 wherein cooked meat is packed and dispatched. If desired, the main control panel 36 could be duplicated on the outside of the wall 12 to tenable alternative control of the whole range of oven operations either from the work area 1 20 or from the work area 122.

The sequence for operations will readily be understood. Food items containing uncooked meat are placed on the shelves of racks in the work area 120 and the entry door 18 is opened after the carousel has been appropriately positioned using the inching control button 32.

The racks are then fed in onto the trays 56, the carousel being appropriately indexed round to allow this to be done using the control button 32.

When the carousel is fully loaded the fans 88 and 90 are started up and the baking operation commences. Hot air from the ducts 84 and 86 passes through the hot air inlet slots into the baking chamber 11, passes across the food items on the rotating carousel, and through the air extraction orifices in the wall 14 into the heat exchanger 40. It is then reheated and circulated.

When the baking operation is completed, the fans 88 and 90 are shut off, the rotation of the carousel is stopped, and the exit door 20 is opened to allow removal of the racks in turn; the inching button 34 being used to rotate the carousel as necessary.

As a preferred feature of the invention, the roof of the heating chamber 11 has at least one exit orifice connected to a suction fan or blower and this orifice is connected by way of a stack or ducting to the exterior. The purpose of this is to allow suction to be applied to evacuate steam and fat vapour from the heating chamber. The oven exit orifice is not shown in the drawings. As a further preferred feature of the invention, a canopy useful for steam extraction may be provided above each door 1 8, 20. As seen in Figure 5, a rectangular canopy 138 is provided above the door 18. The canopy 138 has a front wall 140, a top wall 142, and end walls, not shown. A duct 144 leads from an upper region of the space within the canopy to an entry 146 of a suction blower 148. The suction blower 148 has an outlet 1 50 connected via a pipe 1 52 to a stack, not shown. The blower 148 may also be connected to evacuate the interior of the oven chamber 11, as mentioned above. A similar canopy 1 54 is located above the door 20 and steam and fat vapour rising into it. when the door 20 is opened, are similarly evacuated by the suction blower 148. For simplicity, in Figure 5, details of the oven carousel and heating arrangements have been omitted.

Claims (8)

1. An oven for baking foodstuffs which includes a heating chamber bounded by generally vertical walls, a carousel mounted therein for rotation about a generally vertical axis, there being two opposed walls each having at least one door therein.

2. An oven according to claim 1 in which there are two other opposed walls one of which contains at least a plurality of adjustable hot air supply orifices and the other of which contains at least a plurality of air extraction orifices.

3. An oven according to claim 2 in which at least some of the hot air supply orifices are each formed by a horizontal slot bounded by an upper and a lower flange member, at least one of the flanges being vertically adjustable to allow the slot width to be varied.

4. An oven according to claim 1,2 or 3 in which each door is associated with a position sensor, and an interlock is provided to prevent the carousel being rotated except when opposite doors are shut.

5. An oven according to any preceding claim including a canopy located over each door, and means for evacuating steam, fat vapour or like unwanted gases from the space within the canopy.

6. An oven according to claim 5 in which the evacuating means is a suction pump which is also connected to evacuate the heating chamber.

7. An oven according to any preceding claim in which the carousel comprises a plurality of rackreceiving trays disposed around its axis of rotation and located at a level adjacent to the oven floor, each of the trays being slightly less in width than each of the doors.

8. An oven substantially as herein described with reference to and as illustrated in the accompanying drawings.