Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1996-09-24
1998-10-13
Ferensic, Denise L.
Fluid handling
Line condition change responsive valves
Direct response valves
1374542, F16K 1500
Patent
active
058197907
DESCRIPTION:
BRIEF SUMMARY
This invention relates to fluid check valves and in particular to dual plate check valves, that is to say check valves having two plates or flaps.
Dual plate check valves comprise an annular housing with two substantially semi-circular or D-shaped valve members, referred to as plates or flaps and sometimes also referred to as flappers or wafers, pivotally mounted on a diametral hinge pin. In some cases each plate may be mounted on a separate hinge pin. These plates can take up a valve closed position in which they shut respective semi-circular or D-shaped apertures defined in the housing by a diametral cross piece. The plates are generally spring-urged towards the closed position. They can be urged by pressure of a given level on the upstream side of the valve towards an open position in which they lie generally parallel to the housing axis. A stop pin may be provided parallel to and downstream of the hinge pin to prevent either plate from pivoting more than 90.degree. from the valve closed position.
Such dual plate check valves are non-return valves which open in response to pressure at a given level at the upstream side, that is to say pressure applied to the plates via the semi-circular openings. As pressure decreases, and the flow rate drops, the plates may be urged by reverse pressure, in some cases with the assistance of spring means, towards the valve closed position.
The hinge and stop pins are both normally fixed into the housing by being inserted through holes bored in the housing and then retained therein by means of screwed plugs applied from outside the housing. A requirement is that the screw plugs should permit easy disassembly so that internal parts such as the pin itself, the plates and the spring, if present, can readily be replaced as required. However, corrosion can, over a period, when combined with differential thermal expansion and contraction, loosen the plugs. Leakage may arise due to the plug threads being differentially attacked in corrosive situations leading to local corrosion and eventually leakage and loosening of the plugs.
Dual plate check valves may be of sandwich type, to be held in pipework between two flanges by long bolts, or alternatively of lug type, having lugs extending outward at one or both ends. Particularly with the sandwich type of valve the screw plugs can interfere with the fixing bolts.
To address the above problems the present applicant has previously proposed in European patent application EP-A-0,160,576 dual plate check valves with flaps mounted on one or more hinge pins where the or each hinge pin extends at each end into a bore in an insert, the inserts being received in respective slots in the body. Various means are proposed for retaining the inserts in place within the slots without movement. The preferred retaining system comprises a ring which extends into a groove at the end of the body, from which groove said slots extend, wherein the zone of abutment between the ring and body is radially inwards of the edge of the body, the ring having a smaller outer radius than the external radius of the body and being held in position in the valve body by screws.
Such dual plate check valves wherein the or each hinge pin and, where present, the stop pin are mounted in transverse bores in inserts received in slots formed in the interior of the annular housing provide solutions to the above problems. Such valves may employ an arrangement when there is some play between the hinge pin and insert to reduce wear on sealing surfaces because on opening the inner straight edge of the "D" shaped valve plates lift off the seat before pivoting occurs, so that the plate does not scuff on the cross member of the seat. This can be brought about by providing play between the hinge pin and the inserts. While the play between hinge pin and inserts will in due course cause wear, it is wear in cheap and easily replaceable parts, not in the valve body itself.
We have now developed an alternative system for holding the pin mounting inserts firmly in slots in the housing without m
REFERENCES:
patent: 3678958 (1972-07-01), Satterwhite et al.
patent: 4196745 (1980-04-01), Schutzer
patent: 4867199 (1989-09-01), Marx
patent: 4977926 (1990-12-01), Hocking
patent: 5301709 (1994-04-01), Gasaway
patent: 5381821 (1995-01-01), Muddiman
patent: 5392810 (1995-02-01), Cooper et al.
Copy of International Report dated Sep. 28, 1995.
Ferensic Denise L.
Goodwin International Limited
Kim Joanne Y.
LandOfFree
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