Patent GB-664063-A (GB)
Title: Improvements in baking cereal products
IPC: A21B2/00
Filed: 1949-03-21
Abstract: 664,063. Electric control systems. SCRIBBANS-KEMP, Ltd., and HENDON, A. L. March 20, 1950. [March 21, 1949] No. 7610/49. Class 40 (i). [Also in Groups XI and XL (b)] In baking cereal e.g. a continuous band to make Swiss roll, the percentage loss of moisture from the batter is measured by weighing or by electrical conductance or capacity tests so that the amount of heating given to the dough can be adjusted to give the baked product the desired degree of dryness and uniformity of baking. This can be done by automatic means (not described) for controlling the oven temperature or the speed of a conveyor passing through the oven, or to terminate the time of baking. The baking heat 8 can be applied between upper and lower electrodes 1 and 3 of a high frequency heater. The weight of the partly cooked batter lying on the electrode 3 tips the attached frame 7, Fig. 2 about a pair of spaced pivots 8 whereby the bar 13 presses up on a bent lever 15 to swing the rod 19 of a soft iron core 20 of an electromagnet 21 to the right and away from 21 against the action of a counterweight 22 adjustable on 19. The amount of this out of balance which can be a measure of the moisture content is indicated on a meter (not described) as follows : A beam of light from electric lamp 23 is directed through a lens 24 and through a slot in a vane 18 at the lower end of the lever 15 moved as above. When the slot is in the normal position an image of the slot passes through a lens 25 and is reflected by a mirror 26 equally on to two photo electric detectors 27 which can be coupled to an indicating meter. When the slot is out of position unequal light falls on the photo electric detectors 27 which inequality is indicated on the meter. The weighing system is adjusted by moving the counter-weight 22 until the meter of the photo electric cells shows zero when there is no load on the electrode 3. The operator, reading the meter, applies a restoring current to the electro-magnet 21 to pull in its core 20 so that lever 15 is moved to depress 13 and pivot the frame 7 to raise the electrode 3 to its former position to maintain at least the tuning of the H.F. circuit. To use the apparatus without any known automatic control a current meter and a variable resistance is included in the solenoid circuit. A calibration curve showing the relation between weights and current can be drawn from various experimental weights placed on 3. The batter is then placed on 3 with the H.F. current off. From the curve is read off the value to which the electromagnet (21) current must fall to restore balance when the desired final weight of the (dry) batter is reached. The variable resistance is then adjusted to give this current so that the system becomes unbalanced and the H.F. is switched on. Baking proceeds until the electrode plate 3 rises to balanced position (as shown by the disappearance of current in the photo electric cell circuit) and the H.F. field is then switched off by hand. Automatic control. The electromagnet is replaced by a solenoid coil moving in a constant magnetic field. The out of balance current in the photo electric circuit is amplified and applied to the coil so that the weighing system is continually being rebalanced during baking. To control the baking process a voltage proportional to the coil current (and thus to the weight) is fed to an electronic computing unit, which stores the value of the current corresponding to the initial weight of the dough etc. whereby the H.F. field is switched on, to compute the current corresponding to the required final weight and to switch off the H.F. field when this weight is reached. The baking may be arranged to be finished or browned by radiant and/or convection heat. The automatic control may be made to adjust the power absorbed from the H.F. field in accordance with the moisture content.