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Technology of flour milling

In the mill, in addition to the miller himself either two helpers also worked in case of flour milling, or one in case of preparation of feed mixtures. The milling was mainly driven by water, which powered a system of water wheels, later on a turbine. In the event of performance excess, the turbine powered both the mill and dynamo, which produced electricity and helped to keep rotations of the whole mill. Considering its performance, the mill was capable of processing 4 tons of grain to flour in 24 hours, while the mass for fine flour had to be processed even up to seven times. There could be up to 5 tons of wheat and 3 tons of barley in mill grain storage bins. It was possible to buy the flour by replacement. Per 100 kg of wheat a buyer got 35 kg of fine flour, 35 kg of semolina flour and 15 kg of feed flour. He also got 13 kg of bran and 2 kg of impurities and dust.

The technological process itself started on the ground floor, where the grain was poured into a hopper. A hectoliter weight was also measured. From there it was transported by bucket conveyors in wooden pipes, which provided the vertical movement of the material in the mill, up to the third floor. There, it was necessary to separate the grain from chaff and impurities.

A screening machine and a trieur, or simply a cleaner, were used for this purpose. The grain was cleaned from little stones, soil particles, dust, weeds, straw, chaff and other adulterants, which could have a significant impact on the deterioration of the final products quality.

The grain was further poured through a downcomer into the chamber, where the impurities were aspirated by a ventilator, called an aspirator. Havier particles of the adulterants were stored in storage chambers, lighter ones are sucked by aspiration into a filter. The grain particularly falls down onto a moving sieve. The sieve oscillates due to an eccentric axis of rotation, the grain moves on metal sieves, where smaller stones, chaff etc. fall through and are lead out separately from the grain. Under the machine there is a magnet, which captures small metal objects out of the grain, because they could cause the destruction of machinery, or a mill fire.

The trieur is a machine for cleaning the grain from adulterants of the same diameter as the main raw material, but which differ in length. This method is used for elimination of the adulterants, which cannot be separated by the sieves. It mainly concerns round grains, thus peas, vetch or weeds like cockle. A cylindrical trieur has a cylinder with calibrated holes inside. Being cleaned, the grain goes through the cylinder, individual components are compared to the holes and shorter particles are discharged through a collecting trough while longer ones slide down and are carried away by the cylinder. The cleaning machines were manufactured by the company Josef Prokop & Sons from Pardubice at the end of the 1920s.

The clean grain had to be weighed again. Afterwards, it was either stored in containers or went by gravity to a periodical peeling machine on the first floor.

There, the grain is sharpened, which means that husks – bran, peelings, tailings, sprout and beard, are eliminated. After that, groats remain only. The grain is poured into a feeding system through a downcomer. The feeding system doses it into the machine in periodical cycles. The dosing time could be set and thus it is called a periodic peeling machine. Inside the machine there are fast rotating metal wings, which throws the grain against the emery-covered walls of the drum box. The grain is sharpened due to this. After a certain period of the process, a valve is opened and the sharpened grain (groats) is poured, together with the husks, into a space, where the husks – bran, sprout and beard, are sucked by a ventilator into a filter.. The peeling machine was manufactured by the company Leopold Kašpar from Šternberk, approximately by the end of the 1920s.

The groats could be the final product, but here, they were further processed to flour. This means that they went through a roller mill, usually up to seven times. The roller mills had different types of rollers – either smooth ceramic or corrugated iron.

The ground mixture was again transported by the bucket conveyors to the third floor. There, it was necessary to separate individual sorts according to their particle size, i.e. meals, flours, semolina flour and others. Oscillating sieving machines were used for this purpose.

The oscillating sieving machine is in fact a system of sieves and overflows in frames placed one above the other. The frames hangs on racks. In the middle of the machine there is an eccentric, which is connected to the transmission via a belt. This results in the circular motion of the machine. The ground mixture is poured into the machine via a downcomer, where it is moved on the sieves (fine, coarse, coarsest) and sorted (sieved) due to the backward-and-forward motion. The material gradually falls down to other sieves. Through the complicated system of overflows, the individual sorts are lead from the machine into bagging spouts. The downcomers are connected with inputs and outputs of the sieving machine via textile bags.

The bigger of the machines was manufactured at the beginning of the 1930s by the company Josef Prokop & Sons, the smaller one probably by the company Antonín Jeřábek from Velkého Meziříčí in the 1920s. The first was used for sorting the milled wheat, the second for the milled barley.

The obtained individual sorts could be later blended according to needs in a blending machine. When the semolina flour was requested, the ground mixture had to be further cleaned.

A coarser ground semolina mixture may contain admixtures of bran husks, which decrease the final products quality. The cleaning machine is capable of eliminating these non-standard admixtures and sorting the semolina flour according to its particle size.

The mixture falls down, via a downcomer, on the frames with sieves oscillating due to an eccentric. It moves on the sieves and the ventilator in the upper part of the machine generates air-flow, which sucks out light particles of the bran husks over the sieves, where they are gathered in metal gutters. Due to vibration of the gutters they are lead from the machine separately. The lightest bran particles are sucked by the ventilator into a filter. Heavier semolina particles remain on the sieves and due to their vibration they are separated (sieved) to the final sorts, which fall down into bags on the floor below. The sieves in the input are finer, those in the output are coarser. This machine was manufactured by the company Josef Prokop & Sons at the beginning of the 1930s.

The separate chapter of the milling process is represented by a meal mill, or a milling machine with two mill stones. The flour was milled in such a meal mill till the end of the 19th century. Later on, it was mainly used for milling feed mixtures for livestock.