Valves and valve actuation – Limit stop – Rotary valve
Reexamination Certificate
1999-05-21
2001-07-17
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Limit stop
Rotary valve
C251S293000, C251S315050, C251S315160
Reexamination Certificate
active
06260820
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to valves, and more particularly to configurations of polymeric valves and methods for constructing them.
BACKGROUND OF THE INVENTION
Valves are common components of almost any piping system. Although they can be constructed in many different configurations and sizes, a typical valve will include a few basic elements. These include: a valve body that houses internal components within an internal cavity; inlet and outlet pipes leading to and from the valve body; and a valve member that is positioned within the cavity of the valve body. These components are attached such that fluid entering the valve through the inlet pipe is either allowed by the valve member to flow therethrough to the outlet pipe or prevented from such flow based on the position and/or orientation of the valve member within to the valve body.
In many instances, the valve member of a valve is a rotatable structure, such as a ball or frustoconical plug, that includes a passageway through which fluid can flow. Rotation of the valve member moves the passageway from an orientation aligned with the inlet and outlet pipes (in which fluid can pass through along a flow axis) and an orientation perpendicular to the flow axis (in which fluid flow is blocked). Often valves that employ a rotating valve member include structures on the valve member (or a component attached thereto, such as the valve stem or adapter) and the body that interact to control the degree of rotation of the valve member. For example, many valves are designed to rotate through only 90 degrees between the open and closed positions, with further rotation being prevented by stops located on the upper portion of the body and the lower surface of the adapter.
Valves can be formed of a variety of materials, including both metallic and polymeric materials. Valves formed of polymeric materials can be advantageous in many pipeline environments; they do not rust or corrode, they are typically lighter weight than metal valves, they can be quickly welded into place when the pipelines are also formed of a polymeric material, and often the pieces of the valve (and in particular the valve body) can be molded in an injection or compression molding process rather than requiring extensive machining.
Although they enjoy the foregoing advantages, polymeric valves typically require several assembly steps. Of course, the configuration of components formed of polymeric materials is limited by the practicalities of the molding process. As a consequence, if the valve body is injection or compression molded, it is generally molded in two or three separate pieces that are joined in a subsequent welding or fusion operation. The valve member and accompanying stem and adapter (which facilitate rotation of the valve member) are typically formed of separate pieces that are assembled in a subsequent operation (usually after the valve member has been placed inside the valve body pieces and they have been fused). All of these post-molding assembly steps can add cost to the finished valve. Also, it may be desirable that the valve include structure that halts rotation of the valve in desired positions; if so, these structures are also subject to the practical limitations of the molding process.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a method of constructing a polymeric valve with reduced labor steps and cost.
It is also an object of the present invention to provide such a method that produces a polymeric valve that meets or exceeds the performance of currently produced polymeric valves.
It is an additional object of the present invention to provide such a method that produces a polymeric valve with stops that desirably limit rotation of the valve.
These and other objects are satisfied by the present invention, which is directed to a polymeric valve that can be produced by an insert-molding method. The method comprises the steps of: providing a mold comprising a pair of mating mold halves, with each of the mold halves including a mold cavity; providing a valve member-stem unit comprising a valve member of substantially circular cross-section attached to a stem, with the valve member including a passageway extending therethrough in a direction generally normal to the stem; inserting a mold core into the passageway of the valve member-stem unit to form a mold insert assembly; positioning the mold insert assembly within the cavity of a first of the mold halves; positioning a second of the mold halves in adjacent contacting relationship with the first mold half such that the mold insert assembly is located within the mold cavities of the first and second mold halves; injecting a polymeric material into the mold half cavities such that a valve casing forms around and captures the valve member-stem unit; and removing the valve casing, the valve member-stem unit and the mold core from the mold halves. With this method, the casing of the valve can be formed around the ball-stem unit during molding so that the product of the molding steps is ready for use.
As another aspect of the present invention, a preferred valve that can be formed by the aforementioned method comprises: a casing including a body having an internal cavity, an inlet attached to the body and an outlet attached to the body opposite the inlet; and a valve member being positioned at least partially within the cavity and having an outer surface of substantially circular cross-section. The valve member includes a passageway extending diametrically across its substantially circular cross-section and has an axis of rotation extending substantially normal to the passageway. The valve member further includes a slot extending inwardly toward the passageway from the outer surface, the slot being defined by slot surfaces and being configured to receive a projection extending from a valve casing when said valve member is placed within a valve body and rotated about the axis of rotation. The slot is further configured such that a stop portion of at least one of the slot walls acts as a stop for halting rotation of the valve member relative to the valve body in a first rotative direction. The valve also comprises a stem attached to the valve member that extends away from the valve member along the axis of rotation. In this configuration, the valve member includes stops that interact with the projection of the casing to desirably limit rotation of the valve member, and can be formed with the method set forth hereinabove.
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Catalog article LYCO (R.W. Lyall) Molded In-Place Ball Valve.
Copy of International Search Report for PCT/US 00/13910.
Catalog article British Gas TransCo Technical Specification for Distrubution Valves Part 2—Plastics Bodied Valves of Size up to 63 mm Suitable for Operation at Pressures not Exceeding 5.5 bar (Sep. 1995).
Bastianelli John
Myers Bigel & Sibley & Sajovec
Nordstrom Valves, Inc.
Shaver Kevin
LandOfFree
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