Buhrmill

a machine for milling fodder crops into feed for livestock. They are sometimes used in low-output agricultural mills to grind wheat into flour or to thresh bran. At large industrial mills, buhrmills have been replaced by roller mills.

The working member of a buhrmill (see Figure 1) is a pair of buhrstones with a vertical axis of rotation—the upper stone (runner) rotates, and the lower stone (bed) is stationary. The runner is driven by a shaft (spindle), which rotates in a vertical bearing and rests on an end thrust bearing. To cool the product being milled, the buhrmill is ventilated through a pipe, which is connected to a chamber made of filtering cloth fabric. The chamber is periodically shaken in order to rid the fabric of the flour particles caught in it. The distance between the working surfaces of the buhrstones can be regulated by a handwheel. A feed mechanism provides evenness of delivery of the initial product into the machine.

Figure 1. Buhrmill with a vertical axis of rotation

Buhrmills with vertical axes of rotation but with rotating lower and stationary upper millstones (hulling mills) are used at milling plants, mostly for hulling rice. The productivity of a buhrmill depends on the structural and mechanical properties of the grain being processed. If the productivity of a buhrmill in processing normally moist grain is taken to be 1, the productivity for rye is 0.9, for barley 0.8, and for oats 0.7. Productivity is greatly reduced as the moisture content of the grain increases.