GB2045593A - Bakers oven - Google Patents

Abstract

A baker's oven, for baking biscuits and confectionery, has an oven chamber 10, a moving band 11 for transport of articles to be baked through the oven, and at least one heating panel 12 below the band 11 for transmission of radiant heat to the band and articles thereon. Supplementary heat may be supplied to the articles on band 11 by a forced convection system 13 above the band. <IMAGE>

Description

SPECIFICATION A method of baking biscuits This invention relates to a method of baking biscuits and other like confectionery articles, and a baker's oven for performing the said method.

The baking process for such articles is usually defined into three distinct stages, namely the development of the structure of the product from the initial dough, the controlled removal of moisture therefrom, and the final application of colour and surface texture.

To ensure that production rates demanded by the baking industry may be met, and in order that all three baking stages are properly completed, and especially that moisture removal is carried out gradually, it is usually necessary for the oven to be of substantial length, with each stage of the process being carried out immediately following the previous one without the articles having to be transported to a separate piece of equipment.

The cost of such equipment and the floor space required to house it have increased to degrees which are now becoming unacceptable. There is therefore an urgent need to provide a technique for baking such articles, wherein the overall length of the baking plant is reduced whilst maintaining the required production rates.

It is therefore an object of the present invention to provide a method of baking biscuits and other like confectionery articles, and a baker's oven for performing the said method, wherein the aforementioned requirements are met at least to a substantially improved extent.

According to the present invention, there is provided a method of baking biscuits and other like confectionery articles, comprising the steps of transporting the articles on a moving band through a baking chamber, and applying radiant heat within the chamber below the latter by means having an incandescent surface disposed below the band and which extends across substantially the entire width of the band and along at least a portion of the path of movement thereof, thus to effect a rapid transfer of radiant heat uniformly to the said band and the articles thereon.

Further according to the invention, there is provided a baker's oven for performing the aforesaid method, comprising an oven chamber, a moving band for transporting articles to be baked through the oven chamber, and at least one heating panel disposed in the chamber below the band which provides an incandescent surface extending across substantially the entire width of the band and along at least a portion of the path of movement thereof to apply radiant heat uniformly to the band and the articles thereon.

Preferably, transfer of heat to the articles is further provided by a forced convection current created above the band.

An embodiment of a baker's oven designed and constructed to perform the method of this invention, will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of the baker's oven; and Figure 2 is a cross-sectional view taken on line ll-ll of Fig. 1 and enlarged for the sake of clarity.

The oven chamber is generally indicated at 10, and an endless band 11, conveniently, though not especially of steel mesh, is provided for transporting the articles to be baked through the oven chamber. Below the band 11 there are provided a number of luminous heating panels 1 2 details of whose construction will be referred to hereinafter.Above the band 11 are two forced convection systems generally indicated at 13, and each comprising a duct 1 4 which spans the width of the chamber 10 and has a number of slots 1 5 opening downwardly towards the band 11, and an impeller 1 6 driven by a motor 1 7 for circulating a forced current of air through the duct in the direction of arrows 1 8. The speed of operation of the impeller 1 6 as determined by the motor 1 7 is adjustable to vary the flow rate of air through the forced convection system.

Downstream of the forced convection systems 1 3 with respect to the direction of travel of the band 11 from left to right in Fig. 1, are a further pair of luminous heating panels 20 providing radiant heat acting downwardly on to the upper surface of the band and the articles thereon.

A pair of exhaust fans having ducts 21 and 22 are provided to withdraw gases from the interior of the oven chamber in a controlled manner by varying the flow rate through the ducts 21 and 22 as determined by their respective drive motors 23 and 24 whose speeds are adjustable.

A pair of baffles 25 and 26 are provided effectively to divide the oven chamber into three discrete zones in order to prevent, or at least to minimise, the movement of hot gases along the oven in the direction of travel of the band 11.

Referring now to Fig. 2 it will be seen that each luminous panel 1 2 comprises an array of porous bricks 30 supported on a perforated plate 31 above a plenum chamber 32, to which is fed a combustible gas and air mixture via an inlet pipe 33. The panel is bounded by a single peripheral row of bricks 34 which are also porous and which are supported on a perforated plate 35 below which is a plenum chamber 36 fed, via pipes 37, with cool air. The pipe 33 is fed with gas from pipe 38 and with air from pipe 39 to create a gas and air mixture, whilst the pipes 37 receive air alone from the pipe 39.

As the gas and air mixture passes upwardly through the porous bricks 30 it is ignited by means (not shown) where it emerges from the upper surface of the bricks. This creates an incandescent surface having a very high temperature, for example, in the region of 1,000 C and this infra-red radiant source is defined within the area bounded by the row of cool bricks 34. The incoming gas and air mixture serves to cool the bricks 30 in their lower regions and is thereby pre-heated which improves the combustion efficiency and eliminates heat loss from the brickwork. The incandescent surface reaches it operating temperature very rapidly upon ignition of the gas and air mixture, and when the gas is turned off the supply of cool air can be continued if required, to cool the brickwork rapidly.Each panel 1 2 whose surface extends across substantially the entire width of the band 11 and along a portion of the path of movement thereof is preferably adjustably mounted on screws 40 so that the distance between the band 11 and the surface of the panel 1 2 may be adjusted according to the amount and rate of transfer of heat required for a particular baking process.

In use, the rapid transfer of heat from the luminous panels 1 2 to the band and the articles being baked results in the very rapid formation of the internal structure of the articles. Moisture removal is also achieved very rapidly and uniformly in each article being baked and this controlled uniform removal of moisture results in the ability to cool the products subsequent to baking far more rapidly than with hitherto known systems without the risk of cracking or so-called checking of the products. Furthermore, the conditions in the oven are very readily controlled by adjustment of the effect of the forced convection currents created by the impeller 1 6 and by adjustment of the rate of exhaust through the ducts 21. The final colour and surface texture is imparted to the products by the overhead luminous panels 20.

Any conventional means can be included in the oven to detect the presence or absence of articles on the band. If the feed of articles to the oven ceases, then the heat input to the oven must be reduced. With conventional flame burners their heat output must be reduced whilst maintaining a certain minimum temperature in the oven in readiness for the moment when the feed of articles recommences. However, the more rapid return to temperature of the oven provided by the use of luminous panels enables some or all of them to be completely turned off during a break in the flow of articles, thereby conserving fuel gas.

It will be appreciated that by causing the forced convection currents to move through the oven generally in the opposite direction to that of the band, there is a resultant reduction in heat transfer along the oven during baking.

Therefore, it is possible, more easily, to control the three stages of the baking process.

For a specified production rate the physical length of the oven chamber incorporating luminous panels in accordance with this invention is very much less than with conventional heating systems.

If required, the humidity of the ambient air in the oven chamber can be controlled by the selective injection of steam, for example, on the suction side of the forced convection systems 1 3. In this way, migration and removal of moisture in and from the products is controlled to provide an overall improved surface appearance in certain types of product.

Adjustment of the height of the panels 1 2 with respect to the band 11 is made to suit different products being baked and different thicknesses of band. In this way, an economic use of fuel gas can be ensured.

It is not intended to limit the invention to the above example only, many variations such as might readily occur to one skilled in the art, being possible without departing from the scope of the invention as defined by the appended claims.

For example, the number of luminous panels 1 2 or the forced convection system 1 3 or indeed the exhaust systems 21, 22 can be different from that shown in Fig. 1, according to the length of the oven as determined by the output required. In some cases the use of forced convection above the band may be unnecessary.

The luminous panels 20 in the final stage of the oven can of course be replaced by any other source of radiant heat to provide the required colour and surface texture. Dampers can be provided in the forced convection systems 30 and the ducts 21 and 22 in place of the variable speed facility of those units, in order to control their operation, although it is not thought that such readily controllable conditions can be achieved by the use of dampers.

Although the luminous panels 1 2 have been shown to be arranged lineariy spaced along the oven, they may be arranged in any configuration below the band to transmit heat upwardly therethrough to the products. In certain cases, it may be advantageous to combine the use of luminous panels with conventional flame burners in providing the most suitable source of heat for the product.

The overriding advantage of the luminous panel when compared with conventional flame burners is the greater area of heated surface available and the rapid rate of heat transfer provided.

Claims (14)

1. A method of baking biscuits and other like confectionery articles, comprising the steps of transporting the articles on a moving band through a baking chamber, and applying radiant heat within the chamber below the latter by means having an incandescent surface disposed below the band and which extends across substantially the entire width of the band and along at least a portion of the path of movement thereof, thus to effect a rapid transfer of radiant heat uniformly to the said band and the articles thereon.

2. A method according to claim 1, com prising the further step of providing a forced convection current of air above the band.

3. A method according to claim 2, wherein the direction of flow of the forced convection current through the oven chamber is generally opposite to the direction of movement of the band.

4. A method according to claim 2, or claim 3, wherein the flow rate of the forced convection current is adjustable.

5. A method according to any one of the preceding claims, wherein the products of combustion within the oven chamber are exhausted at a controlled rate thus to control the conditions within the oven.

6. A baker's oven for performing the method according to claim 1, comprising an oven chamber, a moving band for transporting articles to be baked through the oven chamber, and at least one heating panel disposed in the chamber below the band which provides an incandescent surface extending across substantially the entire width of the band and along at least a portion of the path of movement thereof to apply radiant heat uniformly to the band and the articles thereon.

7. A baker's oven according to claim 6, including a plurality of heating panels disposed below the band along the path of movement thereof.

8. A baker's oven according to claim 6, including a forced convection system providing a current of air flowing above the band.

9. A baker's oven according to claim 8, wherein the forced convection system comprises two ducts each having a number of outlet slots therein acting downwardly and spaced apart along the path of movement of the band, each duct including an impeller driven by a variable speed motor for effecting circulation of hot gases through the oven chamber.

10. A baker's oven according to claim 6, including one or more similar heating panels at the downstream end of the oven with respect to the direction of the moving band and acting downwardly on to the articles thereon to provide a final colour and surface texture to the articles.

11. A baker's oven according to claim 6, including one or more exhaust systems for withdrawing gases from the oven chamber, the rate of flow through the exhaust systems being adjustable to control conditions within the oven.

12. A baker's oven according to claim 6, wherein the oven chamber is effectively divided into three zones by a pair of baffles placed within the oven chamber above the band thus to prevent the passage of hot gases through the oven during baking.

1 3. A method of baking biscuits and other like confectionery articles, substantially as hereinbefore described.

14. A baker's oven for performing the method according to claim 1, substantially as hereinbefore described, with reference to, and as illustrated in the accompanying drawings.