Abstract: A composite piston (30) for a vibration pump comprises a core (32), activating a piston, and a piston (34) made of plastic and obtained by means of molding on an insert formed by the core (32). The composite piston (30) thus obtained achieves objects of high precision at a low cost which cannot be achieved with traditional simple pistons made entirely of ferromagnetic metal.

Abstract: A valve combination for vibration pumps performs multiple functions of self-priming, compensation of negative pressure and protection against over pressure. A body (12) contains a non-return valve (18). A valve (26) releases air and compensates for negative pressure. A safety valve (48) vents accidental over pressure originating, for example, from a boiler source. The valve (26) in order to achieve negative pressure compensation, comprises a plug provided with grooves or incisions (40a-c) for favoring the external flow of air subject to negative pressure.