Disconnector for drinking water distribution system

Disconnector intended to be inserted in a drinking water distribution system so as to prevent, in the case of a pressure drop for any reason whatsoever, the water which is downstream and may be considered as polluted, from being fed-back upstream beyond the disconnector. The passage of the water through this disconnector from upstream to downstream and the prevention of feedback of polluted water from downstream to upstream are controlled by a hollow piston closed at both its ends slidable between two end positions under the effect of the greater of the upstream or downstream pressures, whose cylindrical wall has therethrough upstream and downstream apertures, in combination with seals whose lips are applied to said cylindrical wall and which according to the position of the piston, allow the water to pass through these apertures or not.

BACKGROUND OF THE INVENTION 
Disconnectors are small appliances inserted in drinking water distribution 
systems so as to prevent, in the case of a pressure drop upstream for any 
reason whatsoever, the water which is downstream and may be considered as 
polluted from being driven back upstream beyond the disconnector. 
Such appliances have already been proposed for this purpose formed from a 
more or less cylindrical body with coaxial inlet and outlet, a central 
chamber having a discharge outlet towards the drain in case of feedback 
and membrane and valve sealing members upstream and downstream of this 
central chamber, allowing free passage of the water through the body of 
the appliance in normal operation and stopping the arrival of water coming 
from upstream as well as feedback of water coming from downstream in the 
case of a downstream pressure greater than the upstream pressure, the 
leaks of polluted water fed back which may occur penetrating into the 
central chamber and being discharged towards the drain. 
Such appliances have not always the reliability desired because of hazards 
due to the membranes and to the seal of the valves which is not always 
perfect. 
SUMMARY OF THE INVENTION 
To avoid this disadvantage, the disconnector of the present invention, 
still having a hollow cylindrical body with aligned upstream inlet and 
downstream outlet and a central chamber having a discharge outlet towards 
the drain for feedback water is characterized in that the distribution is 
provided by a hollow piston, closed at both its ends, sliding axially in 
the hollow body between two end stops, in one direction under the action 
of the upstream pressure and in the other under that of an antagonistic 
spring which is added to the downstream pressure, comprising in its 
cylindrical wall upstream apertures allowing the water arriving from 
upstream to penetrate into the hollow piston and downstream apertures 
allowing this water to leave the hollow piston to reach the outlet of the 
disconnector, in the case of normal operation, in combination with 
circular seals, having lips applied to the outer cylindrical surface of 
the hollow piston, preventing the penetration of water coming from 
upstream into this hollow piston, as well as that of feedback water, in 
the case of a downstream overpressure, while allowing leaks of feedback 
water to be discharged to the drain.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The disconnector shown comprises a hollow cylindrical body 1, with an 
upstream inlet 2 for drinking water and a downstream outlet 3 for polluted 
water; the hollow body 1 has been shown in two parts, its downstream part 
4 being fitted to its upstream part by means of bolts 5. 
In this hollow body there is fixed an intermediate cylinder 6 leaving 
therebetween an annular empty space 7, open on the upstream side and 
closed on the downstream side, with O-seals 8a and 8b; a hollow axial 
piston 9, closed at its upstream 10 and downstream 11 ends, may slide 
between two end positions, limited respectively by an upstream stop 12 and 
a downstream stop 13, either from left to right of the figure in normal 
operation when the upstream pressure is greater than the downstream 
pressure, shown in FIG. 1, or in the opposite direction when the 
downstream pressure, assisted by that of the antagonistic spring 14, 
becomes greater than the upstream pressure, shown in FIG. 2. 
The hollow piston 9 is separated from cylinder 6 by a free annular zone 15 
in which it is held by four circular seals, fixed in auxiliary cylinder 6 
and whose lips 16, 17, 18 and 19 rub against its external wall; the lips 
of these seals are sloped alternately upstream, downstream, again upstream 
and finally downstream. 
The auxiliary cylinder 6 has therethrough an orifice 20 opening into the 
hollow space 15, defined by it, hollow piston 9 and the lipped seals 17 
and 18. 
Piston 9 has therethrough an upstream orifice 21 and a downstream orifice 
22 which, in normal operating position, are situated respectively between 
seals 17 and 18, and downstream of seal 19, as shown in FIG. 1, and in the 
feedback position, respectively between seals 16 and 17 and between seals 
18 and 19, as shown in FIG. 2. 
In normal operation, when the upstream pressure is greater than the 
downstream pressure and when all the parts of the disconnector are in the 
position shown in FIG. 1, water arriving from upstream penetrates into the 
disconnector through its inlet 2, passes into the free space 7 between 
auxiliary cylinder 6 and hollow body 1, passes through orifices 20 of the 
auxiliary cylinder, and 21 of the hollow piston, to penetrate into this 
latter, from which it exits through the downstream orifice 22 thereof to 
arrive at the outlet 3 of the disconnector. The pressure drop is minimum. 
On the other hand, in the case of feedback, the parts being then in the 
position shown in FIG. 2, water coming from upstream cannot penetrate into 
the hollow body and is isolated from downstream by seals 16, 17 and 18, 
and its pressure tends to apply the lips thereof against the outer wall of 
hollow piston 9; the polluted water fedback is blocked downstream by seal 
19 whose lip it tends to apply against the external wall of hollow piston 
9, and the leaks which might pass under this lip are discharged through 
downstream orifice 22 of hollow piston 9 towards the drain, through the 
discharge orifice for polluted water 23 in which it may arrive after 
passing through opening 24 provided for this purpose in auxiliary cylinder 
6, between the two seals 18 and 19. 
When hollow piston 9 is in its intermediate position, shown in FIG. 3, the 
upstream water is still isolated in the upstream part of the appliance, as 
in the case of FIG. 2, by the three lipped seals 16, 17 and 18, of which 
the first two prevent penetration into the hollow piston 9 through its 
upstream orifice 21 and the third 18 blocks its passage downstream. 
On the other hand, the polluted water fedback is not yet prevented, by 
lipped seal 19, from penetrating through downstream orifice 22 of hollow 
piston 9 inside this latter but it goes directly to the discharge orifice 
to drain 23, passing under the lip of the lipped seal 19 and through 
orifice 24 of auxiliary cylinder 9. 
It will be readily understood that the embodiment which has been described 
with reference to the accompanying drawings has been given purely by way 
of indication and is in no wise limiting and that numerous modifications 
may be made without departing from the spirit and scope of the present 
invention.