Patent GB-697086-A (GB)
Title: Improvements in ovens
IPC: A21B1/40
Filed: 1949-07-09
Abstract: 697,086. Bakers' ovens. BARKER & SONS, Ltd., T., BARKER, F., and STEINER, E. R. Oct. 9, 1950 [July 9, 1949], No. 18223/49. Class 51(ii) [Also in Group XXX] An oven, e.g. a bakers' oven, is characterized in that gaseous fluid is brought into contact with the exterior of the (or each) working chamber whilst in a turbulent condition and in course of propulsion by a fan through a circuit which has no communication with such chamber, the temperature of the circulating fluid being controllable by the operation or otherwise of heating means external or internal to said circuit which is open to atmosphere only at a point or points adjacent the intake of said fan. The bakers' oven shown comprises upper and lower baking chambers 10 which communicate with one another at their ends and are arranged within an externally insulated (14) sheet metal casing 13 having a door at the front. The roof 11 and floor 12 of each chamber are provided externally with transversely arranged fins 17 either in spaced vertical planes as shown or with alternate strips oppositely inclined so as to form hollow fins of triangular section. The fins may be formed by constructing the roof and floor of metal channels the lateral flanges abutting. The finned surfaces of the chambers 10 are enveloped by sheet metal reservoirs 18, 18a, those 18 along the floors 12 extending the full length whilst the chamber roofs 11 are associated with a plurality of end-toend reservoirs 18a. Each such reservoir 18 (or 18a) has a false bottom (or top) consisting of a baffle placed in contact with the edges of adjacent fins 17 and having a plurality of openings 19 so that gaseous medium forced into the reservoir will be constrained to play on the sides of the fins 17. As shown (Figs. 3, 4,) each baffle comprises a plurality of transversely arranged metal strips 20 each of such strips having its edges cut such that tongues 21 left between these cuts may be inclined alternately upwards and downwards to form the openings 19. The oven is heated by a burner 23 arranged at the mouth of a refractory duct 24 leading to the intake of a fan 22 which delivers hot air and combustion products into a duct 25 having lateral branches 26 leading to the bottom reservoirs 18 from whence the hot gases pass through the openings 19 and impinge on the fins 17 before being led via collecting boxes 28 and ducts 29 to the upper reservoirs 18a. The ducts 29 feeding any given reservoir 18a (Fig. 5) are mutually opposed and the gases supplied thereby (after passing through openings 19) escape around the whole periphery of the teservoir 18a into the interior of the casing 13, which communicates at 30 with the burner duct 24. The duct 30 contains a damper 31 by means of which the gases leaving the casing 13 may be directed either to the fan intake or to an atmospheric outlet 32. At various points in its circuit dampers are provided to control the gas flow. Instead of the burner duct 24 being external to the casing 13 as shown it may extend through the upper part thereof and be perforated to allow entry of the hot air and gases within such casing, in which case an adjustable sleeve adapted to cover the perforations to any desired extent may replace the outlet damper 31. Furthermore, instead of each reservoir 18a being supplied by way of the associated reservoirs 18 there may be direct and independently controllable supplies to both such reservoirs and the several reservoirs may exhaust to the fan intake by way of separate ducts instead of through the casing 13. Electric heating may be employed in the oven resistance heaters being installed at either side of the fan 22. A further modification consists in the provision adjacent the roof 11 of either chamber 10, of transversely extending paddles which are rotated whilst the oven is in use so as to set up turbulence. The paddles may be located within part cylindrical domes provided in the chamber roofs 11 the external surfaces of these domes being finned and covered by apertured baffles 20. The paddle shafts may be hollow and perforated to allow the admission of steam to either chamber 10. The goods being baked are circulated through the oven in "continuous" " operation on trays by means of an endless conveyer system. The invention may, on the other hand, be applied to an oven having a single working chamber closed at one end (for example, a draw-plate oven or a peel oven).