GB2129269A

GB2129269A - Hot air oven

Info

Publication number: GB2129269A
Application number: GB08327706A
Authority: GB
Inventors: Rene Voegilin; Oscar Bongard
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-10-15
Filing date: 1983-10-17
Publication date: 1984-05-16
Also published as: MA19931A1; FR2534452A1; IT8323305A0; BE897997A; ES526484A0; JPS59131831A; DE3337162A1; IT1169573B; ES8405589A1; GB8327706D0; IT8323254V0; NL8303527A

Abstract

In the oven hot air is recycled for baking products in dough form, the oven having at least one baking chamber. Each lateral wall of each baking chamber (10) simultaneously comprises means for supplying hot air 65, 66, 67, 68 in the form of jets (60, 61, 62, 63) and means for extracting cooled air 81, 82. As a result of the flow of air and the reflux of cooled air, turbulence is caused, leading to uniform distribution of the heat in each baking chamber. In a variant, apertures 81, 82 are not concentric with tubes 65, 66, 67, 68 but are composed of a plurality of holes disposed in a peripheral manner with respect to the tubes in a circle which is concentric to the tubes. Alternatively, the apertures 81, 82 are annular segments disposed concentrically with respect to the tubes. In another embodiment, the jets (60, 61) are offset with respect to the jets (62, 63) and apertures 81, 82 may also be offset. <IMAGE>

Description

SPECIFICATION Oven The invention relates to an oven in which hot air is recycled for products baked in the form of dough such as bread, fancy bread, cakes, pastries and the like, and in particular to an oven comprising at least one baking chamber.

In accordance with the state of the art, ovens in which hot air is recycled comprising at least one baking chamber in which the dough products to be baked are placed are already known. The products to be baked are either placed on fixed supports such as hearths, in which case each space separating two hearths constitutes a baking chamber, or on movable conveyors such as conveyor belts, shelves and the like. When the movable supports are constituted by shelves, the latter may be removed from and/or placed in the oven either simultaneously by disposing them on a movable open trolley or individually by sliding them on the guides of two wall mountings rigid with the internal lateral walls of the baking chamber.

In order to ensure uniform baking of all the products to be baked, it is necessary to ensure that there is a uniform distribution of heat either in the baking chamber when this invoives an oven having a single baking chamber, or in all the baking chambers in the case of a multiple hearth oven.

Some of these known ovens are not provided with any heat equalizing mechanism. Hot air is simply blown, for example, into each baking chamber in an oven having several baking chambers or into the single baking chamber, i.e. in this case between the superposed shelves, via apertures in the form of holes or slots provided in the two lateral walls of the baking chamber(s) and the cooled air is extracted through one or several apertures provided in the rear wall or in the roof.

The air which always follows the same path is gradually cooled between the first products which it contacts and the last products which it contacts.

The drawback of these ovens is that the heat is not made uniform over all the products to be baked. As a result of this the products are not uniformly baked.

The US Patent Specification 3.529.554 also discloses an oven in which hot air is recycled comprising a speciai mechanism for suitable equalization of the heat. In this oven, the hot air is blown through holes and/or slots provided in one of the lateral walls of the baking chamber and the air from which the heat has been taken is extracted through similar apertures provided in the opposite lateral wall. The hot air flow is periodically reversed and, consequently, the wall through which the hot air is blown becomes the wall through which the cooled air is extracted.

This periodic reversal is achieved by means of a mechanism comprising motorised shutters which periodically reverse the blow or suction functions of the tubes through which the hot air circulates and which connect the heat generator to the baking chamber.

Another mechanism used for the periodic reversal of the hot air flow is often constituted by the use of two separate fan units which operate alternately, one unit causing the hot air to flow in one direction and the other unit causing it to flow in the opposite direction.

The French Patent Application 2 469 124 discloses an oven in which hot air is recycled which comprises, in addition to a mechanism for periodically reversing the flow of hot air, a rotary distribution of the hot air injection into the baking chamber by means of jets of hot air which are disposed vertically in the baking chamber and subjected to a slow alternating rotation in order to ensure uniform baking.

However, these ovens which make use of mechanisms for achieving uniform heating have several drawbacks. In the first place the cost price of these ovens is considerably increased as a result of the cost of these mechanisms and, secondly, these ovens consume a certain amount of power for the operation of these mechanisms.

In addition, as a result of the large number of components of these mechanisms, they are subject to operating malfunctions and are therefore somewhat unreliable.

The object of the present invention is to remedy these drawbacks. The invention, as set out in the claims, resolves the problem of providing an oven in which hot air is recycled in which the heat is uniformly distributed over all the products to be baked without the provision of a mechanism for the uniform distribution of the heat.

For this purpose, the invention relates to an oven in which hot air is recycled for products based in the form of dough such as bread, fancy bread, cakes, pastries and the like, and in particular to an oven comprising at least one baking chamber, characterised in that each lateral wall of each baking chamber simultaneously comprises means for introducing hot air in the form of jets and means for extracting the cooled air such that, as a result of the flux of hot air and the reflux of cooled air, there is provided a turbulence causing a uniform distribution of the heat in each baking chamber.

The advantages provided by this invention consist essentially in that the reliability of the oven is increased as a result of the fact that there is no mechanism for uniformly distributing the heat over all the products to be baked leading to a lower power consumption and a reduction in the cost price of the oven.

The invention is described in detail in the foliowing description which is given purely by way of non-limiting example with reference to the attached drawings, in which: Fig. 1 is an elevation in cross-section of an oven in which hot air is recycled in accordance with the invention, Fig. 2 is a view from the left in cross-section along the line lI-Il of Fig. 1, Fig. 3 is a plan view in cross-section along the line Ill-Ill of Fig. 1, Fig. 4 shows a detail of Fig. 1 on a larger scale.

Several types of ovens in which hot air is recycled are already known. In a first type, the oven comprises superposed hearths and each space disposed between two hearths forms a baking chamber. In a second type, the oven comprises a single baking chamber in which there are placed, via movable supports such as conveyor belts, shelves which are placed in the oven simultaneously by means of a movable trolley or shelves which are placed in the oven individually by sliding them onto the guides of two wall mountings rigid with the internal lateral walls of the baking chamber.

The present invention may be applied equally as well to both types of oven but, for the sake of better understanding and by way of non-limiting example, the description given below relates to an oven having a single baking chamber, and in particular to an oven having a single baking chamber in which the products to be baked are located and removed by means of movable open trolley.

Reference is made to Figs. 1 to 3.

The oven 1 comprises a housing 2 constituted by a roof 3, a base 4, two lateral walls 5, 6, a rear wall 7 and a front wall 8 having an insulated door 9 providing access to the baking chamber 1 0. This housing 2 is surrounded by an insulating material 11 enclosed by an outer jacket 12.

The baking chamber 10 is defined by a hollow chamber 13 having a U-shaped cross-section which extends from the rear wall 7 to the front wall 8, the two arms 14, 1 5 parallel to the lateral walls 5, 6 being connected together by a transverse wall 1 6. This hollow chamber 13 is formed by two parallel walls 17, 18, i.e. the outer wall 17 and the inner wall 18. The two vertical arms 19, 20 of this inner wall 18 of the hollow chamber 13 constitute the lateral walls of the baking chamber 10. These parallel walls 17, 18 enable the provision of extraction ducts for the cooled air 21 .22, which ducts are connected to a manifold 23 which is itself connected to an extraction cone 24 of a recycling fan 25.The latter supplies the cooled air to a hot air generator 26 traversed by heating batteries of electrical resistances 27, 28. In accordance with a further embodiment the heating element may also be constituted by a gas or liquid combustion device.

In the case of this type of oven having a single baking chamber, the products to be baked 30 are located in the baking chamber 10 via the opening 29 in the front wall 8 using an open trolley 31 which, after climibing an inclined ramp 32, rests on the base 4.

This open trolley 31 comprises a base 33 provided with swivel castors 34, 35, 36, 37 rotating about a horizontal axle 38, 39, 40, 41 held by fork joints 42, 43, 44, 45 rigid with the lower face 46 of the base 33. The upper face 1 7 of this base 33 has fixed to it two lateral uprights 48, 49 whose internal faces 50, 51 are provided with guideways 52, 53, 54 disposed one above the other on which there are disposed shelves 55, 56.

57 etc. containing products 30 to be baked which are shown in the drawings, by way of non-limiting example, as French loaves.

In certain types of oven having a single baking chamber, the guideways 52, 53, 54 are directly rigid with the external face of the two vertical arms 19, 20 of the internal wall 18 of the hollow chamber 13. In this case, the shelves 55, 56, 57 containing the products 30 to be baked, are placed one after the other in the baking chamber 10.

In the case of the type of oven having a number of baking chambers, the guideways 52, 53, 54, which are rigid with the outer face of the two vertical arms 19, 20 of the inner wall 18 of the hollow chamber 13, act as supports for the various hearths on which the products to be baked are disposed.

The arrangement of the hollow chamber 13 enables two hot air supply manifolds 58, 59 for the hot air coming from the hot air generator 26 to be provided between the outer wall 1 7 of the two arms 14, 15 of the hollow chamber and the two lateral walls 5, 6.

In accordance with the invention which may be applied both to ovens having a plurality of baking chambers and to ovens having a single baking chamber, there is provided within each baking chamber 10 a turbulent flow of hot air which is pulsed into the said baking chamber 10 in the form of jets 60,61,62,63.

In accordance with a first embodiment, the jets 60, 61, 62, 63 flowing from each of the arms 19, 20 of the innter wall 1 8 face one another and are orientated towards the vertical median plane 64 of each baking chamber 10. For this purpose there are provided injection tubes 65, 66, 67, 68 which pass from one side to the other of the vertical arms 14, 1 5 of the hollow chamber 13.

These injection tubes 65, 66, 67, 68 communicate on one side at right angles to the outer face of the two vertical arms 19, 20 of the inner wall 1 8 of the hollow chamber 13 and, on the other side, at right angles to the outer face of the two arms 69, 70 of the outer wall 17 of the hollow chamber 13. As a result of this, each baking chamber 10 is caused to communicate with the supply manifolds 58, 59. These injection tubes 65, 66, 67, 68 are disposed in horizontal rows 71,72. There are as many horizontal rows 71, 72 of injection tubes 65, 66, 67, 68 etc. as there are spaces between the bases 73 of the shelves 55, 56, 57 and the tops 74 of the products 30 to be baked. In addition, there is provided a final horizontal row 75, 76 at the bottom underneath the lowermost shelf 57 and a final horizontal row 77, 78 at the top above the products 30 to be baked disposed on the topmost shelf 55.

Reference is now made to Fig. 4.

The injection tubes 65, 66 of any crosssectional shape of the vertical arm 1 9 of the inner wall 18 are designed to spray jets of hot air, which diverge to a very slight extent, between the tops 74 of the products 30 to be baked and the bases 73 of the shelves 55, 56, 57, as far as the vertical median plane 64 of each baking chamber 10 when they contact the jets of air supplied from the injection tubes 67, 68 which blow the air from the other vertical arm 20. In this way there is obtained a reciprocal inversion of the hot air jets causing the required turbulence. The circulation obtained in this way is shown schematically by the arrows 79, 80. The blanket of hot air produced at right angles to each injection tube 65, 66, 67, 68 is therefore turbulent.The incoming hot air jets and the outgoing jets of cooler air are mixed and simultaneously contact the same points of the tops 74 of the products 30 to be baked and the bases 73 of the shelves 55, 56, 57. The heat is therefore made uniform and, consequently, the products 30 to be baked are uniformly baked.

However, it is necessary to extract the air which has been cooled by the products 30 to be baked in order to obtain this turbulence. For this purpose, as shown in Fig. 4, the vertical arms 19, 20 of the inner wall 18 of the hollow chamber 13 are provided with apertures 81, 82 concentric to the injection tubes 65, 66, 67, 68 etc. Consequently, there is provided between the external periphery 83 of the injection tubes 65, 66, 67, 68 and the internal periphery 84 of the apertures 81,82 a passage 85, 86 via which the cooled air is extracted by the recycling fan 25 by means of the extraction ducts 21,22.

This relative arrangement of the injection tubes 65, 66, 67, 68 and the extraction apertures 81,82 forces the jets of air injected towards the vertical median plane 64 of each baking chamber 10 to return towards the inner emission wall 98 peripheraliy with respect to the injected air jet 60, 61,62.

The drawback relating to the successive contacting of the products with a flow of air whose temperature is decreasing is therefore avoided, without having to use special mechanisms for uniformly distributing the heat which may, in any case, only provide average uniformity as a result of their periodic action.

In accordance with a variant of this first embodiment, the apertures 81,82 are not concentric with the injection tubes 65, 66, 67, 68 but are composed of a plurality of holes disposed in a peripheral manner with respect to the injection tubes 65, 66, 67, 68 in a circle which is concentric to the said injection tubes 65, 66, 67, 68.

In accordance with a further variant of this first embodiment, the apertures 81,82 are constituted by annular segments disposed concentrically with respect to the injectioh tubes 65, 66, 67, 68.

In accordance with a further embodiment, which is basically designed for ovens which are not very wide, the jets 60, 61 flowing from one of the arms 19, 20 of the inner wall 1 8 of the hollow chamber 1 3 are offset with respect to the jets 62, 63 flowing from the other arm 20, 1 9 of the inner wall 18 of the hollow chamber 13. In this way the air jets 60, 61 flowing from the arm 14 pass through each baking chamber 10 from left to right whereas the jets 62, 63 flowing from the arm 1 5 pass through each baking chamber from right to left and the interpenetration of the jets causes the required turbulence between the hot air jets injected and the cooled air jets extracted.

In the same way as the injection tubes 65, 66, 67, 68, the extraction apertures 81,82 are in an offset arrangement and interposed between two consecutive injection tubes.

Although the invention has been described with reference to a particular embodiment, it is obvious that it is in no way limited thereto, and that various modifications with respect to shapes, materials and combinations of these various elements may be made thereto without departing from the scope of the invention.

Claims

1. An oven in which hot air is recycled, for products baked in dough form such as bread, fancy bread, cakes, pastries, and the like, the oven comprising at least one baking chamber, each lateral wall of the or each baking chamber simultaneously comprising means for introducing hot air in the form of jets and means for extracting the cooled air, which means, as a result of the flow of the air and the reflux of the cooled air, cause turbulence providing uniform distribution of the heat in the baking chamber.

2. An oven as claimed in claim 1, in which the extraction means comprises a hollow chamber having a U-shaped cross-section composed of two arms which are parallel to the lateral walls of the housing of the oven, the cooled air which has been extracted by a recycling fan.circulating in the hollow chamber.

3. An oven as claimed in claim 2, in which the hollow chamber comprises an outer wall and an inner wall in order to form extraction ducts for the cooled air, the two vertical arms of the inner wall constituting the lateral walls of the baking chamber.

4. An oven as claimed in claim 2 or 3, in which the hollow chamber extends from the rear wall to the front wall of the housing of the oven.

5. An oven as claimed in any preceding claim, in which the extraction means comprises apertures provided in the immediate vicinity of the introduction means.

6. An oven as claimed in any preceding claim, in which the introduction means comprises two manifolds which invert the hot air coming from the recycling fan and pass through a hot air generator provided with heating elements, these supply manifolds for the hot air being disposed between the outer wall of the two arms of the hollow chamber and the two lateral walls of the housing of the oven.

7. An oven as claimed in any preceding claim, in which the introduction means comprise injection tubes for the hot air, having any desired cross-section, which pass from one side to the other of the vertical arms of the hollow chamber.

8. An oven as claimed in claim 7, in which the hot air injection tubes communicate on one side at right angles to the outer face of the two vertical arms of the inner wall of the hollow chamber and, on the other side, at right angles to the outer face of the two arms of the outer wall of the hollow chamber.

9. An oven as claimed in claim 7 or 8, in which the hot air injection tubes are disposed in horizontal rows, the number of rows being a function of the number of spaces between the bases of the shelves and the tops of the products to be baked.

10. An oven as claimed in claim 9, further comprising a final horizontal row of injection tubes located below the lowermost shelf for containing products to be baked.

11. An oven as claimed in claim 9 or 10, further comprising a final horizontal row of injection tubes located above the level of the products to be baked on the topmost shelf.

12. An oven as claimed in any of claims 7 to 11, when dependent on claim 5, in which the apertures are concentric to the hot air injection tubes.

13. An oven as claimed in any of claims 7 to 11, when dependent on claim 5, in which the extraction means comprise passages for the cooled air located between the outer periphery of the injection tubes and the inner periphery of the apertures.

14. An oven as claimed in any of claims 7 to 11, in which the extraction means comprise a plurality of holes disposed in a peripheral manner to the injection tubes in a circle concentric to the said injection tubes.

1 5. An oven as claimed in any of claims 7 to 11, in which the extraction means comprise annular segments disposed concentrically with respect to the injection tubes.

1 6. An oven as claimed in any preceding claim, in which the jets flowing from one of the arms of the inner wall of the hollow chamber are offset with respect to the jets flowing from the other arm of the inner wall of the hollow chamber.

17. An oven as claimed in claim 16, in which the injection tubes of the arms of the inner wall of the hollow chamber are disposed in a staggered manner.

18. An oven as claimed in claim 16 or 17, in which the extraction apertures for the cooled air are disposed in a staggered manner.

19. An oven as claimed in claim 18, in which the apertures are interposed between two consecutive injection tubes.

20. An oven substantially as described with reference to, and as shown in, the accompanying drawings.