Valves and valve actuation – With means to increase head and seat contact pressure – With positive reduction
Reexamination Certificate
2001-02-23
2003-07-29
Lee, Kevin (Department: 3753)
Valves and valve actuation
With means to increase head and seat contact pressure
With positive reduction
C251S192000
Reexamination Certificate
active
06598853
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates of a valve of the type generally having seal plates which are urged outwardly against inner surfaces of a valve body to block flow through valve body apertures, and in which the seal plates are moved inwardly away from the valve body prior to rotation to move the seal plates away from the apertures to permit flow through the valve.
Typical prior art valves of this type have a tapered central member which is forced in a direction perpendicular to that of the flow through the valve to press seal plates against inner surfaces of a body of the valve by a wedging action. Opening of such a valve is effected by first withdrawing the tapered member slightly to remove the force urging the seal plates against the valve body followed by rotation of the tapered member by 90° to rotate the seal plates away from the opposed apertures in the valve body and align a through bore in the tapered member with the apertures for permitting flow through the valve. Closing of the valve includes a reversal of the above described two stage process. In such valves, the provision of an actuating mechanism which accommodates the lost motion associated with movement of the tapered member perpendicular to flow through the valve and provides a two stage actuation sequence involving translational and rotational movement adds undesirably to the size and complexity of the valve. The taper of the tapered member also adds undesirably to the size of the valve. A further adverse consequence of the use of a tapered member, is that in order to avoid the overall size of the valve being prohibitively large, the aperture therein, through which flow occurs when the valve is open, is usually less than the full bore size of pipes connected to the valve, leading to undesirable restriction of flow through the valve.
Particularly in the field of remote submarine interconnection of pipework, there exists a requirement for compact closely juxtaposed valves which can be actuated without the complications associated with prior art valves of the type described above.
SUMMARY OF THE INVENTION
An object of the invention is to provide a design of valve which permits the valve to be compact and easily actuated and avoids at least some of the disadvantages associated with prior art valves. A further object of the invention is to provide a design of valve which permits a gang of closely juxtaposed valves to be simply actuated by straightforward rotation.
A further object of the invention is to provide a valve of the above described type which avoids surfaces which are to be sealed against each other from rubbing against each other with a large force perpendicular to the surfaces as the surfaces converge towards a sealed state or depart therefrom. Such rubbing tends to lead to a high rate of wear.
Thus according to the invention there is provided a valve comprising a valve body defining a throughflow direction, two seal means which are urgeable away from each other against complementary sealing surfaces to prevent flow through the throughflow apertures and actuating means which is rotatable in an opening direction about a rotation axis substantially perpendicular to the throughflow direction to rotate each seal means from its associated throughflow aperture to allow fluid flow therethrough, wherein the valve includes restraining means for arresting rotation of each seal means by the actuating means in a closing direction opposite to the opening direction when each seal means is aligned with its associated complementary sealing surface, the actuating means including a first camming surface for each seal means which is urged against a first cam following surface of the associated seal means to urge its sealingly against its complementary sealing surface in a direction away from the rotation axis after rotation of the seal means has been arrested and upon further rotation of the actuating means in the closing direction.
As a consequence of the urging of the seal means outwardly by means of a rotary camming action, the need for the above described two stage actuation involving moving an actuation means axially and then rotating it is obviated as is the requirement for a tapered wedging member which contributed to the above described disadvantages. A plurality of valves constructed according to the invention can be closely juxtaposed in a gang and all opened or closed simultaneously by interconnecting their aligned actuating means and applying a simple turning force to one or both ends of the gang of interconnected actuating means. Furthermore, since the seal means are moved against the complementary sealing surfaces after rotation of the sealing means has been arrested, wear of the seal means and these surfaces is largely avoided.
Preferably each first camming surface is situated on the exterior of a central spool part of the actuating means in order that the first camming surfaces can bear directly on inner surfaces of the seal means and thereby provide a very compact arrangement. Furthermore, each first camming surface preferably comprises a portion of a circular cylindrical surface having its central longitudinal axis transversely offset from the rotation axis and more preferably the central longitudinal axes of the two first camming surfaces are transversely offset from the rotation axis in opposite directions. With such an arrangement, accurate machining of the first camming surfaces and complementary first cam following surfaces is facilitated since surfaces having non-circular cross-sections are avoided. A further advantage of such an arrangement is that large areas of the first camming surface and associated first cam following surface will remain in contact during camming actions thus reducing high wear rates associated with camming actions in which only small areas of the camming surfaces interact.
To facilitate production of the actuating means still further, preferably the central spool is constituted by first and second joined spool halves each having an exterior surface defining one of the first camming surfaces.
So as to avoid unnecessary valve components and ensure that the valve is as compact as possible, preferably each seal means includes a seal plate having an arcuate inner surface constituting the first cam following surface and a metal seal may be provided on an outer surface thereof.
In order to ensure that each seal means is clear of the valve body prior to rotation of the seal means away from the throughflow apertures, to avoid damage to the seal means or valve body, preferably the actuating means includes a second camming surface for each seal means against which a second cam following surface bears which is urged towards the rotation axis upon initial rotation of the actuating means in the opening direction thereby drawing the seal means away from its associated complementary sealing surface.
Preferably each second camming surface and second cam following surface comprise a part of a circular cylindrical surface, so as to benefit from the advantages associated with such circular camming surfaces discussed above.
The second cam following surface of each seal means is preferably situated at an end region of the seal means and more preferably second cam following surfaces are situated at opposite end regions of each seal means, each engaged by a corresponding second camming surface of the actuating means. Such an arrangement contributes to the compactness of the valve and ensures an efficient straight withdrawal of the seal means from the throughflow apertures thus avoiding the danger of the seal means jamming as they are withdrawn. Conveniently the second camming surfaces are situated adjacent ends of a central spool part of the actuating means.
Since the seal means preferably overlie a central spool part of the actuating means, the second camming surfaces are preferably formed in plate means projecting radially outwardly with respect to the rotation axis.
In order to ensure that no rotational movement of the seal means occurs prior to their withdrawal, the va
Appleford David Eric
Lane Brian William
Alpha Thames Limited
Lee Kevin
Summa & Allan P.A.
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