Impeller type pump having seal means and protective means

Claim 1

a front casing comprising first ceramic main portion defining therein an inlet, one part of a pump chamber and one half of a discharge port, and a first protection member covering the first ceramic main portion; a back casing confronting the front casing and comprising a second ceramic main portion defining therein the other part of the pump chamber and the other half of the discharge port, and a second protection member covering the second ceramic main portion; a plurality of projections each having a flattened end surface, extending toward the second protection member and formed in spaced relation with each other on that marginal surface of the first protection member which confronts the second projection member; a plurality of projections each having a flattened end surface, extending toward the first protection member and formed in spaced relation with each other on that marginal surface of the second protection member which confronts the first protection member, said projections of the second protection member being so arranged that the flat end surfaces of the projections of the second protection member abut against the respective flat end surfaces of the projections of the first protection member; a continuous packing disposed between the marginal areas of the first and second ceramic main portions; and narrowed portions for reducing the circumferential speed of waste water therebetween more than the circumferential speed of waste water in the pump chamber, said narrowed portions being provided at those areas of the confronting marginal portions of the first and second ceramic main portions which are adjacent to the pump chamber inwardly of said packing.