GB2163845A

GB2163845A - A heat accumulator for convection ovens

Info

Publication number: GB2163845A
Application number: GB08519988A
Authority: GB
Inventors: David Wyn Jones
Original assignee: Mono Equipment Ltd
Current assignee: Mono Equipment Ltd
Priority date: 1984-08-09
Filing date: 1985-08-08
Publication date: 1986-03-05
Also published as: GB8420232D0; GB8519988D0

Abstract

A heat accumulator for a convection oven has an array of horizontal parallel bars (3) in a substantially vertical stack. The bars are side-by-side in sets (4, 5) with spacing between. Each set is staggered transversely to the bar length in relation to the set above and below, and at one stage of a baking cycle water sprayed over the top set will trickle down over all the others, turning to steam. This distribution is aided by angled ribs on the bars, the ribs facing each other across a space between bars sloping in opposite directions. Lateral plates (10) are provided to re-direct water splashing outwardly back into the array. <IMAGE>

Description

SPECIFICATION A heat accumulator for convection ovens This invention relates to bakers' ovens of the type known as convention ovens where hot air is blown through the baking chamber. An established technique with these ovens is to use this hot air also to heat up an accumulator. At the beginning of the next baking cycle water is sprayed or distributed over this accumulator and is transformed into steam which permeates the chamber. This enhances the colour and crispness of the crust. It is important that a large amount of steam should be generated in a short period of time, which requires a large surface area and good water distribution over it. At the same time, the hot air must have good access during the latter part of the baking cycle to restore heat to the accumulator for the next generation of steam.

A favoured arrangement is to make the accumulator as an upright structure at the side of the baking chamber and separated from it by a grille or perforated bulkhead. Water need then only be sprayed or distributed over the upper part of the accumulator, from which it will trickle down to reach the lower parts. Care has to be taken to ensure that it does not channel into rivulets, leaving parts of the accumulator dry.

It is the aim of this invention to provide an accumulator which meets these needs.

According to one aspect of the present invention there is provided a heat accumulator for a convection oven comprising an array of generally horizontal, parallel bars arranged in a substantially vertical stack, the bars being side-by-side in sets, and adjacent sets being vertically spaced and staggered transversely to the bar length relative to those above and below.

The vertical spacing allows for the passage of air transversely through the stack and rapid vertical descent of the water.

The bars preferably have angled rib formations and facing rib formations on adjacent bars are advantageously angled in opposite direction. This has the effect of promoting even distribution of water over the length of the bars.

The rib formations may be helical on a basically cylindrical rod, and they may be continuous or interrupted. One preferred form of bar is a length of reinforcing rod for concrete, which is produced with angled projections along opposite sides which are in effect interrupted helical ribs.

It is prudent also to position guide means to recover and re-direct outwardly splashed water descending the array back into the array. These may be elongated plates extending parallel to the bars and angled downwardly and inwardly in relation to the array.

The stagger is conveniently by one bar, and the majority of sets will normally comprise just two bars. However, the uppermost and lowermost sets may have three bars, while the remainder are pairs, each having one bar aligned vertically with the central bars of the two extreme sets.

According to another aspect of the present invention there is provided a convection oven equipped with a heat exchanger as defined above.

According to a further aspect of the present invention there is provided a method of baking using such a convection oven.

For a better understanding of the invention one embodiment will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 is a front elevation of a heat accumulator for a convection oven.

Figure 2 is a vertical section on the line ll-ll of Figure 1, and Figure 3 is a horizontal section on the line Ill-Ill of Figure 1.

The accumulator has an elongated base 1 in the form of a trough which provides a sump for water.

There will be an outlet (not shown) to a drain or, possibly, for recirculation of the water. Two columns 2 extend upwardly from the ends of the base and between them extend sets of side-by-side horizontal bars 3, most of the sets being pairs 4 but the uppermost and lowermost ones 5 having three bars. Conveniently, these are lengths of steel reinforcing rod, and they have angled ribs 6 which may be regarded as interrupted helical formations.

The bars may be supported by the columns 2 in various ways, but in this example each column is an inwardly facing channel member across which there extend a number of plates 7 which form shelves for supporting the ends of the bars 3.

These may be secured, by welding for example, or they may simply rest in depressions in the shelves.

In another arrangement (not shown) the ends of the bars may rest on spacer elements retained by the channel members so that the stack is built up simply by dropping in spacers and rods in alternation.

The pairs 4 are arranged so that in cross-section, as seen in Figure 2, they have a staggered or zigzag appearance. Each pair has an "outer" bar on one side or the other and an "inner" bar, all the inner bars being aligned in a vertical plane with the central bars of the triple sets 5 at the top and bottom of the array.

There is a slot between the bars of each pair 4 and between adjacent bars of the sets 5, and there is also vertical spacing between adjacent pairs 4 and between the sets 5 and the top and bottom pairs 4. The bars are arranged so that on opposite sides of each slot or space the ribs 6 angle in mutually transverse directions. This has the effect of promoting even distribution of water over all the bars of the array.

A water distribution pipe 8 extends between the upper ends of the columns 2 and in operaion sprays water over the uppermost set 5 of three bars, an inverted channel-shaped cover 9 ensuring that the water is confined to this zone. Also extending between the columns 2 and outside the bars on each side there are angled plates 10. Each plate is closely adjacent an outer bar of a pair 4 and slopes downwardly and inwardly, to be virtually tangential to the ribs 6 on the outer under side, thereby forming a slot. Water passing down the array and possible splashing outwardly will be re-directed back into it to trickle over the bars lower down. These plates 9 have heat retention properties and also act as part of the accumulator, contributing to the production of steam when impinged upon by water.

Although pairs 4 of bars will generally by sufficient, it is possible that a thicker accumulator may be preferred. There may therefore be three or even more bars in each set.

Claims

1. A heat accumulator for a convection oven comprising an ar.ray of generally horizontal, parallel bars arranged in a substantially vertical stack, the bars being side-by-side in sets, and adjacent sets being vertically spaced and staggered transversely to the bar length relative to those above and below.

2. A heat accumulator as claimed in claim 1, wherein the bars have angled rib formations.

3. A heat accumulator as claimed in claim 2, wherein facing rib formations on adjacent bars are angled in opposite directions.

4. A heat accumulator as claimed in claim 2 or claim 3, wherein the rib formations are helical on a basically cylindrical rod.

5. A heat accumulator as claimed in claim 2, 3 or 4, wherein the rib formations are continuous.

6. A heat accumulator as claimed in claim 2, 3 or 4, wherein the rib formations are interrupted.

7. A heat accumulator as claimed in any preceding claim wherein adjacent bars in each set are spaced to form a slot therebetween.

8. A heat accumulator as claimed in any preceding claim wherein guide means are positioned to recover and re-direct any outwardly splashed water descending the array back into the array.

9. A heat accumulator as claimed in claim 8, wherein said guide means are elongated plates extending parallel to the bars and angled downwardly and inwardly in relation to the array.

10. A heat accumulator as claimed in any preceding claim, wherein the stagger is by one bar.

11. A heat accumulator as claimed in any preceding claim, wherein the majority of sets comprise two bars.

12. A heat accumulator as claimed in claim 11, wherein the uppermost and lowermost sets comprise three bars while the remainder are pairs of bars, each pair having one bar aligned vertically with the central bars of the two extreme sets.

13. A heat accumulator substantially as her ainbefore described with reference to the accompanying drawing.

14. A convection oven equipped with a heat accumulator as claimed in any preceding claim.

15. A method of baking wherein a product is baked in a convection oven as claimed in claim 14.