Abstract: A rotary pump has a housing 1 with a driven rotor 7 installed in the housing 1. Vanes 12 are connected around the periphery of the rotor 7. Helical springs 14 are supported against rotor 7, which, acting on an inner surface of vanes 12, press the free end of the vanes 12 against the bore 6 of the housing 1. Each spring 14 has two coaxial sections of turns which spiral in opposite directions so that the springs 14 press the vanes 12 against the bore 6 of the housing 1 without tilting. These sections of turns are each designed with an adjacent support end 21 on the outer or inner section and a bail section, which is arranged between the inner and outer end of the sections of turns, connecting the inner and outer ends of these sections of turns rigidly together, and which projects radially beyond the sections of turns.

Abstract: A method for forming an arcuate electrode adapted for the electrolytic production of grooves in the arcuate surface of an article, in which grooves are first formed in a plane metal blank. The grooved blank is then reshaped to have a curvature corresponding to that of the article, and the grooved curved surface of the blank is coated with an insulating material. The insulating material is then removed from the surface of the blank, except in those areas overlying the grooves, and the thus bared portion of the blank is then eroded, for example, by etching, so that the residual insulating layer projects from the surface of the blank. In use, the thus formed electrode is employed as a cathode, with the projecting insulation being held in close contact with a corresponding curved surface of the article to be grooved. The article is connected as an anode, and an electrolytic liquid is directed to flow in the channels formed between the electrode and the article.