Return check valve

#The invention relates to a backflow preventing check valve with a housing in which a closing member is arranged, movable between a closing position and an opening position, and abutting with a sealing region on a valve seat in the closed position. A device is provided for pressure compensation when the backflow preventer is closed and a fluid volume is occluded on the outflow side.

#Check valves are used in gas, water or the like supply lines in order to prevent a backflow of the fluid against the regular throughflow direction. Thus check valves are also increasingly being built into water lines, in order to counter the penetration of dirty water into the fresh water supply line in the case of a reduced pressure.

#However, the use of such check valves in the field of single lever mixing fittings frequently gives rise to the problem that the water, which is trapped between the closed check valve on the one hand and the likewise closed valve seat on the other hand when the cold water side or hot water side is shut off, is strongly heated up by external influences until system pressures arise which lead to damage to the weakest portion of the supply line and thus frequently to the check valve. This can ultimately result in a closure of the supply line or to a likewise undesired crossflow.

#Further features of the invention will become apparent from the following description of an embodiment example according to the invention in connection with the claims and also the accompanying drawing. The individual features can be embodied individually or collectively in an embodiment according to the invention.

#FIG. 1 is a cross-sectional view of a backflow preventer, the closing member of which carries a coating which encloses a pressure compensation space between itself and the coated region of the closing member,

#FIG. 2 is a cross-sectional view of a backflow preventer in which the pressure compensation space is formed by an annular sleeve which is provided on the inside of the inflow side housing section, and

#Two backflow preventers 1, 10 are shown in FIGS. 1 and 2, and can be used in a fluid line in the region of a water fitting. The backflow preventers 1, 10 can for example serve as a cold or hot water check valve which is connected on the cold or hot water side upstream from a single lever fitting.

#The backflow preventers 1, 10 have a housing 2 in which a closing member 3 is provided in the throughflow direction Pf 1, movable between a closed position and an open position. The closing member 3 is movable from its closed position, respectively shown on the left-hand side, against the force of a return spring 4 into its open position, respectively shown on the right-hand side. In the closed position, the closing member 3 of the backflow preventer 1, 10 abuts on a valve seat 5.

#If the single lever mixing fitting is closed, the water enclosed between the water fitting and the cold or hot water check valve 1, 10 can itself for example or due to a rise in the surrounding temperature, warm up or heat up such that an extremely high system pressure arises. So that this high system pressure does not cause continuing damage, the backflow preventers 1, 10 respectively have a device for pressure compensation.