Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Reexamination Certificate
2000-04-20
2002-12-17
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
C277S637000, C277S638000, C251S305000, C251S306000
Reexamination Certificate
active
06494466
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The present invention relates to a type of seal used in a rotatable valve. A valve member, pivotally disposed in a valve housing, makes contact with the seal to form a leak-tight boundary in the valve housing to secure a flow of fluid through the valve. Specifically, the invention relates to an improvement in the seals used in these valves.
2) Description of the Related Art
Valves having resilient seals are widely used in commerce and have a multitude of applications. Such valves are commonly used in fluid piping systems to stop and start the flow of fluid through the piping system. The specific construction of these valves differs widely depending upon the application in which the valves are used. Generally, the valves of the type to which the present invention pertains include a valve housing with an inlet and outlet port, a hollow interior defining a volume through which fluid flows between the inlet and outlet ports, and a rotatable valve member mounted within the interior of the valve housing. The valve member is pivotably disposed within the hollow interior of the valve housing about an axis which is generally perpendicular to the flow of fluid through the valve. Generally, the valve member is mounted on a shaft that extends through the hollow interior of the valve housing. The shaft is turned by a mechanical drive system for opening and closing the valve. When the valve member is rotated to a position that defines a plane which is generally parallel with the direction of fluid flow, the valve is fully open. When the valve member is rotated to a position that defines a plane which is generally perpendicular to the direction of fluid flow, the valve is closed.
To provide a leak tight boundary within the valve housing, the valve is provided with a seal. In conventional construction of these valves, the seal has many forms. Generally, the seal is an annular member positioned in the interior of the valve body that is adapted to contact the valve member as the valve member rotates to the closed position. Often the seal is affixed to the interior of the valve housing by means of an interior annular groove in the valve housing. The groove helps retain the seal in a position where it will contact the perimeter of the valve member when the valve member is in the closed position to form a leak tight boundary between the valve and the valve housing under a wide range of pressures and fluid flow conditions. Conventional valve construction also involves the use of mechanical means such as adhesives, frictional engagement, welding, and riveting to help retain the seal in position in the annular groove of the valve housing interior.
In some prior art valve structures, such as the one disclosed in U.S. Pat. No. 3,544,066, a curable polymeric material, such as epoxy resin is used to retain the valve seal within the internal annular groove of the valve body. In the '066 patent, the seal is constructed from a Buna-N type of rubber material with 60-75 durometer hardness. The valve seal is inserted into the internal annular groove and the epoxy resin is introduced, in liquid form, between the annular exterior surface of the seal and the internal annular groove. The integrity of the seal formed in this manner is dependent upon the epoxy's bonding strength and the amount of epoxy coverage between the seal and groove surfaces. Thus, as disclosed in the '066 patent and in later designs of seals for use in conventional valves, the surface area of the seal and groove surfaces exposed to the epoxy is increased to raise the relative strength of the bond between the seal and the groove. In the '066 patent, the seal is formed with a grooved inner surface to increase the seal inner surface exposed to the epoxy, and thereby improve the gripping co-action between the seal and the epoxy resin to bond the seal to the groove.
To assist in retaining the seal within the interior annular groove of the valve housing, conventional valve designs use a seal with a formed profile that interlocks with the formed groove profile in the housing of the valve. In U.S. Pat. No. 3,799,501 such a structure is disclosed. In the '501 patent, the seal is formed with annular fins on its side faces that cooperate with the chevron cross section of the annular groove formed in the interior surface of the valve housing. To provide the maximum amount of frictional engagement between the seal and the groove, the profiles are closely matched. When the valve member is moved to the closed position, the elastomer ring compresses under the force of the valve member and interlocks tightly with the annular groove.
However, the use of both of these techniques to secure the seal in the valve housing has been a continuing challenge to designers of these valves. Epoxy resin alone has been found to be insufficient to retain a seal in the groove under extreme flow conditions. For example, under a throttle flow condition, wherein an extreme pressure differential exists between the upstream and downstream sides of the valve (e.g., when a valve is only slightly open and fluid is forced through a highly restricted area), differential pressures acting on the valve seal may cause the relatively large volume of epoxy under the seal to deform, thus moving the seal in the annular groove. Without a structure surrounding the seal to retain the seal in position in the valve housing (an interlock), the seal may fail to seat against the valve member when the valve member is returned to the closed position. In this situation, the integrity of the leak tight boundary of the valve is breached.
On the other hand, when the profiles of the seal and the valve housing or groove are closely matched so as to provide a maximum amount of surrounding and gripping co-action between the two surfaces, the injected epoxy cannot be consistently and evenly dispersed between the two surfaces to effectively bond the surfaces together. As a result, the integrity of the seal may also be compromised, since a portion of the seal may be held in the groove only by the frictional cooperation of the inter-engaging profiles.
The use of a closely matched and tight fitting interlock between the seal and the interior annular groove has other draw backs. The cost of constructing a valve using a system of inter-engaging profiles increases with the complexity of the form of the interlock. Generally, the valve housing is cast with the annular groove having the formed profile for the interlock. In order to increase the frictional engagement and strength of the interlock, the formed profile used in the annular groove must be fabricated with a relatively high level of dimensional accuracy so that it closely matches the complementing formed profile on the seal. This high level of dimensional accuracy requires more stringent manufacturing controls for both the seal and the valve housing/groove, thus increasing the cost of the valve.
When a more closely matched formed profile and tighter fitting interlock is used between the seal and the groove to increase the frictional engagement, the seal becomes more difficult to install in the groove. Using conventional installation methods, the seal is mechanically forced into the groove. Although the seal is generally flexible and compressible, when the interlock between the seal and the groove is tightly controlled during manufacture, the amount of force needed to insert the seal in the groove dramatically increases because of the near interference fit between the seal and the groove. Consequently, during installation of the seal in the groove, the large amount of force exerted on the annular interior surface of the seal may result in damage to the seal as it is inserted into the groove. Since the interlock portion of the seal generally has the smallest cross section, the interlock surfaces of the seal may not be able to withstand the amount of force needed to install the seal in the groove. Hence, the damage may be sustained on the seal portion of the interlock, where the resultant
Hartman Brian T.
Hartman Thomas A.
Knight Anthony
Peavey Enoch E
Thompson & Coburn LLP
LandOfFree
Valve seal construction with non-congruent side serrations does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Valve seal construction with non-congruent side serrations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve seal construction with non-congruent side serrations will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2977148