Diaphragm pump with at least one reciprocating piston and balancing device therefor

A diaphragm pump (1) comprising at least one diaphragm (4) and, fastened to the diaphragm, a reciprocating piston (2) acted upon by a connecting rod (5) which, in turn, is acted upon and driven at an end facing away from the reciprocating piston (2) by one of an eccentric (6) and a cranked portion of a drive shaft, the diaphragm pump's rotating masses and at least part of its oscillating masses being balanced by at least one counterweight (7) fixedly mounted thereon and moving in synchronism therewith, an annular cavity (9) within a co-rotating housing (10) arranged concentrically to an axis of rotation (8) about which the eccentric (6) or the cranked portion of the drive shaft revolve during operation of the diaphragm pump (1), the annular cavity (9) having a radial width bounded by an outer surface (13) and an inner surface (16), at least two rolling elements (12) arranged in said cavity (9) which are capable of rolling freely on the outer surface (13) serving as a raceway, the annular cavity (9) having an interior which is devoid of liquid and empty except for the rolling elements (12), and the radial width of the annular cavity (9) slightly exceeding a radial diameter of the rolling elements (12), in such a way that, as a result of an unbalance present during start-up of the diaphragm pump, the rolling elements (12) are movable to and fro between the outer and inner surfaces (13, 16), so that during start-up the rolling elements (12) are initially entrainable in a circumferential direction due to a sliding friction between themselves and the outer and inner surfaces (13, 16).