Patent GB-815733-A (GB)
Title: Improvements in or relating to baking ovens
IPC: A21B1/48
Filed: 1955-03-26
Abstract: 815,733. Bakers' ovens. COLLINS & CO. Ltd., T., and COLLINS, A. T. March 23, 1956 [March 26, 1955], No. 8907/55. Class 51 (2). A bakers oven incorporating a conveyer and means to circulate and heat the oven atmosphere without admixture with combustion products has atmosphere extraction and readmission means respectively located at regions of the oven chamber that are spaced apart both vertically and horizontally and extend throughout the width of the conveyer path within the chamber. In an oven in which bread is baked on a conveyer 12a, Fig. 1, whilst moving through a chamber 11, a fan in a casing 29, Fig. 2, draws the atmosphere from the chamber through ducts 25 and causes it to pass to the suction side of the fan through the annular space surrounding the central conduit 17 of a heat-exchanger 16 in the same direction as the combustion gases which issue from an oil or gas burner 19 into the conduit 17 for eventual discharge to a flue 20. The fan returns the reheated atmosphere to the chamber through ducts 27, Figs. 2, 3, and conduits 28. The chamber, to which steam may be admitted through a duct 14, may comprise lengthwise parts or the oven may consist of superposed chambers. In either case each part or chamber may be served by a separate heat-exchanger and circulation system. In a two-tier oven each chamber has such an exchanger and system 30a, 30b, Fig. 7, in each of which a burner end 31, Fig. 6, leads to a furnace retort 32 and thence to atmosphere via a conduit 33 transfixed by cross-tubes 34. A fan 43 induces oven atmosphere to flow from the chamber through extraction ducts 41a or 41b, Fig. 4, and trunking 40 to a jacket 38, surrounding the conduit 33, through which it is forced to flow in a zig-zag path by baffles therein. The reheated atmosphere is extracted from the jacket by the fan 43 and readmitted to the chamber through re-admission ducts 44a (or 44b). In a further heat-exchanger, the atmosphere is drawn from the oven chamber by a fan 60, Fig. 12, and reheated by passage around a combustion chamber 53 and through a sinuous passage defined by the walls of the exchanger 45 and internal baffles 55 during the course of which it is heated by gilled tubes 52 through which flows the hot gases emanating from the chamber 53. In another oven construction, the gaseous flow from a re-admission duct 28a, Fig. 8, to an extraction duct 25a, is in the same direction as the conveyer travel, whilst the flow direction from a duct 28b to a duct 25b is counter thereto. Fig. 9 shows two re-admission structures 28c, 28d, with extraction ducts 25a, 25b, therebetween, and also two similar but inverted re-admission structures 28c<SP>1</SP>, 28d<SP>1</SP> ,  located between the conveyer laps with extraction ducts 25a<SP>1</SP>, 25b<SP>1</SP>, between them. In an oven having top and bottom electrical or hot gas heating means 62, 63, Fig. 10, the atmosphere flows from either of two re-admission ducts 28e, 28f, to an extraction duct 25 in a direction counter to the conveyer travel. Baffles 64, 65 trap the atmosphere in the upper part of the oven and flaps 66, 67, at the entry end of the oven define a zone into which steam is injected through means 68. In yet another arrangement of re-admission ducts, the ducts 44a, Fig. 13, have perforated tubes 44c projecting therefrom lengthwise of the oven chamber. The re-admission ducts may have individuallyoperated dampers, e.g. 69, Fig. 2, and the oven temperature may be controlled by manually and/or thermostatically regulating the burner and/or the atmosphere circulating fan speed. The oven atmosphere may be electrically heated and a heat-exchanger having its input circuit connected to a fuel burning heater may have an electrical heater associated with its atmosphere (or output) circuit. Specification 732,897, [Group XXX], is referred to.