c comprises valve port disk 6 valve passage disk 8 valve assembly cover 10 and drive motor 12 in the embodiment illustrated in fig1 4 valve port disk 6 and valve passage disk 8 are shown as circular in construction although they may be shaped otherwise for example polygonal valve port disk 6 and valve passage disk 8 are preferably made from a durable material such as ceramic which can be ground to a highly polished flat finish to enable the faces of the disks to form a fluid tight seal when pressed together valve port disk 6 has a highly polished flat circular engagement surface 14 a smooth cylindrical sidewall 16 fig1 feed opening 18 outer openings 20a 20b and inner openings 22a 22b openings 20a and 20b lie in the same ring array i e they each are the same radial distance from the geometric center of surface 14 openings 22a and 22b likewise lie in the same ring array openings 18 20a 20b 22a and 22b are on the same diameter line through the geometric center of circular surface 14 and they extend completely through disk 6 in a direction perpendicular to surface 14 openings 20a and 20b are shown as being the same size as openings 22a and 22b although they can have different sizes all openings of a given array of openings are the same size however valve passage disk 8 which likewise has a highly polished smooth circular engagement surface 24 and a smooth sidewall 26 has several arcuate passages or channels cut into surface 24 each of which has as its center of rotation the geometric center of circular surface 24 these include optional blind feed passage 28 which has a center circular portion 30 and an arcuate.