Patent GB-1144722-A (GB)
Title: Improvements in or relating to dough mixing apparatus
Inventor: WADE PETER
IPC: G05D24/02
Filed: 1966-02-14
Abstract: 1,144,722. Automatic power control of doughmixing apparatus. FLOUR MILLING & BAKING RESEARCH ASSOCIATION. Feb. 14, 1967 [Feb. 14, 1966], No.6319/66. Heading G3R. [Also in Division B1] Dough mixing apparatus comprises means to automatically add water to the mix at one or more predetermined temperatures to achieve optimum consistency, the amount of water or its rate of input being dependent on the difference between the actual power transmitted by the mixer to the mix and the nominal power absorbed by a mix of desired consistency at the particular predetermined temperature, the latter power being empirically determined to obtain a graph relating power input to dough temperature. In the embodiment shown in the Figure a signal representative of the actual power transmitted by the mixer driving motor 2 is obtained via circuit elements 3, 3a, 4, 72 and is compared with a signal representative of nominal power obtained from a potentiometer 67 whose position alters in accordance with the change of dough temperature and whose output is arranged to correspond to the empirically determined graph. The resultant of these two signals is used to control the addition of water to the mixer 1 via members 74--77 so making the actual power equal to the nominal, this addition being made over a predetermined temperature range whose lower and upper limits are respectively set by a fixed potentiometer 55, 56 and an adjustable potentiometer 57. In a typical mixing operation dough having a water content less than optimum is inserted in the mixer 1 and the motor 2 is started through members 31--33, which action also energizes a time delay circuit 35, 36 chosen to allow the mix to obtain a uniform inital temperature before energizing, via members 37, 38, a motor 39 which adjusts a potentiometer 41 to a setting corresponding to this temperature transmitted from the mix via members 15, 16, 17. Due to the closed condition of a contact 82a the error signal applied to member 74 has no effect until the predetermined temperature set by members 55, 56 is reached, whereupon contact 82a is opened by members 81, 82, 85 and addition of water commences at a rate determined by the characteristics of the shaping circuit 74 which, for example, may add an integral term to the signal or may square it. When the temperature set by potentiometer 57 is reached, contact 82a is reclosed by members 82, 84, 85 and another relay 61 is energized to changeover contact 61a and control motor 64 so that potentiometers 54, 67 are returned to their "OFF" positions in preparation for the next mixing operation. The dough temperature continues to rise until a predetermined value set by a potentiometer 86 is reached whereupon the motor 2 is de-energized via members 90, 32, 33. In another embodiment described, Fig. 1 (not shown), the power error signal is isolated until a predetermined temperature is reached, whereupon it is used to add an appropriate quantity of water to the mix and is then isolated again. In a further embodiment, Fig. 2 (not shown) the error signal is used to add water at a series of pre-set temperatures, the signal again being isolated, applied and re-isolated in each case.