Machine for preparing beverages, in particular espresso coffee, and valve and valve unit for use therein

Abstract

A machine for preparing beverages, in particular espresso coffee, comprises a hydraulic circuit including a brewing unit, a water tank, a pump having the inlet connected in fluid communication to the tank, and the outlet or delivery connected in fluid communication to the brewing unit. A normally closed one-way hydraulic valve, which is set between the pump and the brewing unit, enables a flow of water toward the brewing unit when the pressure of the water delivered by the pump exceeds a substantially predetermined threshold. There is a heating means for heating the water delivered by the pump. The machine has a normally open discharge valve having a main inlet (), connected between the one-way hydraulic valve and the brewing unit, a main outlet, connected toward a discharge space, and an open/close member set between the main inlet and the main outlet, designed to assume an open condition and a closed condition, where it enables and prevents, respectively, a flow of fluid between the inlet and the outlet, with the open/close member being urged by a corresponding spring into the open condition. The discharge valve is a hydraulically driven valve, which includes a chamber for hydraulic driving of the open/close member, an auxiliary inlet of the driving chamber, connected to the delivery of the pump, and an auxiliary outlet of the driving chamber, connected to the brewing unit, in such a way that water forced by the pump passes through the driving chamber before reaching the brewing unit. The discharge valve has a further outlet of the driving chamber, connected in fluid communication to a device for spillage of water from the driving chamber, in particular towards one of the water tank and the inlet of the pump.