A seminal change in flour milling occurred in 1785 when Oliver Evans built an automatic flour mill to eliminate manual labor in material handling (Figure 4.9). Previously, several stages of grinding had been required, which included manual sifting between the stages to remove finished flour and inedible particles and to winnow out coarse materials for further grinding. In the automated mill, however, men and buckets were replaced by elevators to take the grain to the top of a tall building, and by downpipes and conveyors to move partially processed grain from machine to machine as it flowed from the top to the bottom of the building.
The main items of equipment in the automated mill were the
■ Elevators, conveyors, and chutes by which grain and its products were transported
■ Cylindrical reel separators that Evans invented to make sieving continuous
■ Grinding stones
■ The “hopper boy,” which cooled the ground meal in a hygienic manner
The automated hopper boy was named after the human hopper boy, whose job in the pre-1785 plants was to rake the freshly ground flour manually to cool it before further processing. If not done quickly and thoroughly, the flour could be contaminated by insects (McAndrew 2000). Evans’ hopper boy was a drum containing a slowly rotating rake into which hot flour flowed from the elevator and from which cool flour flowed to the sifter. Evans changed flour milling from a labor-intensive process that was unhygienic, with semiprocessed flour waiting in open piles for manual transportation to the next station, to a continuous, hygienic, and automated process.