US2707925A - Heating systems for bakers' ovens and other heating chambers - Google Patents

Description

J. F. NAYLOR 2,707,925 HEATING SYSTEMS FOR BAKERS OVENS AND OTHER HEATING CHAMBERS May 10, 1955 2 Sheet-Sheei 1 Filed April 28, 1950 Inventor $55M fiwms Mon /Q May 10, 1955 J. F. NAYLOR 2,707,925

HEATING SYSTEMS FOR BAKERS OVENS AND OTHER HEATING CHAMBERS Filed April 28. 1950 2 Sheets-Sheet 2 HEATING SYSTEMS FOR BAKERS @VENS AND OTHER HEATENG CHAMBERS .loscph Francis Naylor, Newton-le-Willows, England, as-

signor to T. & T. Vicars Limited, l lewton-le willows, England, a British company Application April 28, 1959, Serial No. 158,724

Claims priority, application Great Britain April 28, 1949 6 Claims. 3!. l07--63) This invention concerns heating systems for bakers ovens and other heating chambers of the type in which a conveyor adapted to carry the material to be heat treated'passes between heat exchange ducts which are part of a closed system circulating a gaseous heat carrying medium and have heating means at intervals therein.

The principal object of the present invention is to provide a heating system of the above type in which heat radiation from the ducts may he more efficiently controlled. According to the present invention, in a heating system of tl e type described the heat exchange ducts are constructed from metal of heavy section and include a plurality of substantially parallel passages longitudinally of the flow of the heat carrying medium, adjustable balancing dampers being disposed at intervals in each of said passages.

The dampers are preferably arranged in sets, each set comprising a damper in each of said passages in staggered disposition one to the other over a short length of the ducting. A set of dampers may be disposed lust prior to each heating means in the gaseous flow. Each damper may be substantially equal in order to the cross-sectional area of flow of the passage in which it is disposed and supported by a spindle so as to be rotatable about its transverse axis in respect to the passage. One end of each spindle may protrude from the oven side and have adjusting means attached thereto.

The invention will be described further by way of example with reference to the accompanying drawings in which:

Fig. 1 is a diagrammatic sectional representation of one end of a heating system of the type described.

Fig. 2 is a plan view of a section below the oven roof and above the ducting.

Fig. 3 is a sectional elevation on the line Ill-4E of Fig. 2.

Fig. 4 is a sectional end elevation on the line lV-lV of Fig. 3, and

Pig. 5 is a detailed View of one form of adjusting means.

Referring to the diagrammatic Fig. 1 a heating systern of the type described is provided in a long oven 11 in which the biscuits are to be baked. An endless conveyor 12 passes over a roll 13 outside one end of the oven H and between two lengths l4, 15 of heat exchange ducts. It then passes over a similar roll (not shown) outside the other end of the oven and back to the first roll 13 along the bottom of the oven. The upper and lower lengths 14, 15 of heat exchange ducts are connected by trunks at one end of the oven (not shown) and at the other end of the oven the lower length of ducting 15 exhausts to a circulating fan 16 which feeds the upper length of ducting 14. An escape chinmney 1? controlled by a damper 18 is provided just after the fan outlet. The direction of circulation of a heat carrying gaseous medium is indicated by the arrows. At intervals along the ducts 14, 15 enlarged portions 19 are provided at which heating means are disposed and dampers are provided at intent; aerlid 2,707,925 Patented May it), 1955 tervals within the ducts. The ducts are manufactured from metal of heavy section.

The more detailed Figs. 2, 3, 4, and 5 show by way of example a portion of the upper duct 14. A length of ducting is cast and is supported in position in the oven by means (not shown), but which usually consist of suitable girders and heat insulating substances, with a small gap 22 between the next succeeding section. Connection of the succeeding portions which is also not shown usually consists of an encircling lap of asbestos topped by steel plates and bolted to one section only or"- the duct to allow for expansion. The duct 14 has three parallel passages 14a, 14b, 14c separated by dividing walls 23, 24 and at intervals sets of dampers are provided, each set being preferably just prior to a heating r cans in the gaseous flow through these passages. The divi walls 23, 24 are interrupted at each enlarged portion 1? so that the heating means 20 may extend freely transversely of the ducting. The interruption of the longitudinally extending dividing walls at each enlarged portion lit provides openings or passages permitting gaseous medium to flow from one longitudinally extending parallel passage into another longitudinally extending parallel passage assuming, of course, that the pressure differential is such as to cause the gaseous medium to flow in the manner described. Since the heatmeans 2d extends freely transversely of the ducting, said eating means passing through said openings or pass es provided by the interruption of the longitudinald1 g dividing walls 23, 24, it is apparent that s or passages are substantially in alignment a transverse to the length of the ducting. A complete set of dampers comprises one damper 25,

-lled at one end in an outer or dividing wall according to which damper it supports and at the other end the oven. The spindles 28, 29, 34) support their respective dampers 25, 2e, 27 along their central transverse axes when the dampers 25, 26, 27 are disposed nearly vertically in the passages, ll la, 14b, 1 the passages are not quite completely blocked (see Fig. 4). The ends or" the spindles 25%, 29, 3d which protrude from the oven ii are provided with handles 28a, 2%, 343a, the main portions of which are at right angles to the spindles. A spring loaded stud 23b, 29b, 3% at the outer end of each handle 28a, 29a, 39a is able to move in a circular are over the face of a quadrant secured to the oven wall in which recesses are provided. The spring loaded studs 23b, 29b, 3% can therefore engage in any of the recesses as desired and the recesses are conveniently marked to indicate the position of the respective dampers.

Fig. 5 shows an adjusting handle similar to those in Figs. 2, 3 and 4 but with the handle upwardly extending instead of downwardly extendin Either type of handle could be adapted for satisfactory use but it is important that the dampers should never reach a completely closed position. In other words the gaseous flow must never be wholly interrupted. To prevent this a suitable stop 34 may be provided on the quadrant of the adjusting means to prevent further movement of the handle. in the embodiment shown in Figs. 2, 3 and 4 a suitable stop would be to the right of each handle 28a, 29a, 39a.

The bottom of each section of ducting of the upper length 14 is provided with downwardly projecting. cor-.

U of the bottom length will, of course, have similar corrugations on their upper surfaces. These corrugated lengths have also a greater thickness than the rest of the ducting.

In operation the ducts being constructed of metal of heavy section, are capable of accumulating a large amount of heat and provide an efficient means of heat radiation to the articles which pass between them on the conveyor. The space between the upper and lower lengths of ducting comprises the treatment Zone.

The heating means 2t.- acting at intervals in the ducts 14, 15 may be, for instance, burners of the oil or gas type and serve to re-heat periodically the gaseous medium as it flows along the ducting.

Without the dampers 25, 26, 27 described above it would be impossible to control the heat radiation from the ducting except by controlling the amount of fuel or air supplied to the burners. This method of control would be difificult to carry out in an efficient manner. By means of the dampers, 25, 26, 27 however, the oven 11 is potentially divisible into substantially independent heating zones both longitudinally and transversely and accurate control of heat distribution within the oven 11 can be achieved both longitudinally and transversely. This control is facilitated by the convenient external adjusting means provided on each damper spindle 28, 2%, 30.

In Figs. 2, 3 and 4, for instance, the dampers 25, 26 in two adjoining passages 14a, 1412 are fully closed whilst the third damper 27 is fully open. This state of affairs would tend to increase the amount of heat supplied to the radiating surface of the ducting which surrounds the two adjoining passages 14a, 14b and is just prior to the dampers whilst the radiating surfaces of these passages 14a, 1411 after the dampers in the direction of the gaseous flow would be somewhat cooler. The passage 14c containing the open damper 27 would tend to remain at substantially equal temperatures at all parts. It might be necessary, however, to adopt the damper disposition just referred to in order to maintain equal temperatures transversely of the oven. In other words, the respective dampers can be positioned to permit a desired rate of flow longitudinally of the ducting and a desired amount of flow from one longitudinal passage into another longitudinal passage through an opening in a dividing wall located at an enlarged portion 19, or through a plurality of said openings. It is apparent that the ability to control the amount of straight longitudinal flow and to control also the amount of flow from one parallel passage to another parallel passage provides what can be described as a two-dimensional control of heat distribution throughout the length of the oven. Without such two-dimensional control, the oven heat tends to vary not only lengthwise of the oven but also transversely thereof. This may be due to the type of burner used or to inequalities of the heating effect in normal circumstances which can arise in unexpected ways. This example, however, serves to indicate the many different effects of damper manipulations which can be obtained and in practice it is possible, along with burner control, to accurately adjust the heat radiating strength of any part of the ducting as required.

I claim:

1. A heating system for bakers ovens and like heating chambers comprising a plurality of heavy metal duct sections serially connected together in a closed system, means to circulate a gaseous heat carrying medium longitudinally through said duct sections, a longitudinally extending partition wall positioned within said duct sections and providing parallel longitudinally extending passages within said duct sections, said partition wall being interrupted for a portion of its length to define an opening permitting gaseous medium to flow transversely from either parallel passage to the other parallel passage, and an independently adjustable damper positioned in each d of said parallel passages immediately in advance of said partition wall opening in the direction of flow of said gaseous medium, said dampers providing control of flow of gaseous heat carrying medium longitudinally along said parallel passages and said partition wall opening permitting gaseous heat carrying medium to flow from either parallel passage to the other parallel passage to effect heat redistribution in a direction transverse to the length of said duct sections.

2. A heating system for bakers oven and like heating chambers comprising a plurality of heavy metal duct sections serially connected together in a closed system, means to circulate a gaseous heat carrying medium longitudinally through said duct sections, a longitudinally extending partition wall positioned within said duct sections and providing parallel longitudinally extending passages within said duct sections, said partition wall being interrupted for a portion of its length to define an opening permitting gaseous medium to flow transversely from either parallel passage to the other parallel passage, gaseous medium heating means located at and extending freely through said partition wall opening in a direction transverse to the length of said duct sections, and an independently adjustable damper positioned in each of said parallel passages immediaely in advance of said partition wall opening in the direction of flow of said gaseous medium, said dampers providing control of flow of gaseous heat carrying medium longitudinally along said parallel passages and said partition wall opening permitting gaseous heat carrying medium to flow from either parallel passage to the other parallel passage to effect heat redistribution in a direction transverse to the length of said duct sections.

3. A heating system for bakers ovens and like heat ing chambers according to claim 2 wherein said partition wall is interrupted at intervals throughout its length to define a plurality of openings permitting gaseous medium to flow transversely from either parallel passage to the other parallel passage, there being a heating means located at and extending freely through each partition wall opening in a direction transverse to the length of said duct sections.

4. A heating system for bakers ovens and like heating chambers comprising a plurality of heavy metal duct sections serially connected together in a closed system, means to circulate a gaseous heat carrying medium longitudinally through said duct sections, longitudinally extending partition walls positioned within said duct sections and providing a plurality of parallel longitudinally extending passages within said duct sections, said partition walls being interrupted at intervals throughout the length of said walls to define openings permitting gaseous medium to how transversely from one parallel passage to another parallel passage, and an independently adjustable damper positioned in each parallel passage and immediately in advance of each of said partition wall openings, said dampers providing control of flow of gaseous heat carrying medium longitudinally along said parallel passages and said partition wall openings permitting gaseous heat carrying medium to flow from one parallel passage into another parallel passage to effect heat redistribution in a direction transverse to the length of said duct sections.

5. A heating system for bakers ovens and like heating chambers according to claim 4 including heating means located at and extending freely through each partition wall opening in a direction transverse to the length of said duct sections.

6. A heating system for bakers ovens and like heating chambers comprising a plurality of heavy metal duct sections serially connected together in a closed system, a portion of said serially connected duct sections being enlarged, means to circulate a gaseous heat carrying medi um longitudinally through said duct sections, longitudinally extending partition \valls positioned within said duct sections and providing a plurality of parallel longitudinally extending passages within said duct sections, each of said partition walls being interrupted at said enlarged portion of said serially connected duct sections to define openings permitting gaseous medium to flow transversely from one parallel passage to another parallel passage, heating means located at and extending freely through each partition wall opening in a direction transverse to the length of said duct sections, and an independently adjustable damper positioned in each parallel passage and immediately in advance of each of said partition wall openings, said dampers providing control of flow of gaseous heat carrying medium longitudinally along said parallel passages and said partition wall openings permitting gaseous heat carrying medium to flow from one parallel passage into another parallel passage to efiect heat redistribution in a direction transverse to the length of said duct sections.

References Cited in the file of this patent UNITED STATES PATENTS 1,657,959 Crosland Jan. 31, 1928 1,772,920 Smoot Aug. 12, 1930 2,501,765 Dumbleton et a1 Mar. 28, 1950 FOREIGN PATENTS 504,950 Great Britain May 3, 1939

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