Methods for making molded plug and plug valve

• US 4,180,542 A
• Filed: 05/11/1978
• Issued: 12/25/1979
• Est. Priority Date: 09/04/1973
• Status: Expired due to Term

• Current Assignee: NIBCO Incorporated
• Original Assignee: Celanese Corporation
• Inventors: Wrasman, Thomas J.
• Primary Examiner(s): Hoag, W. E.
• Application Number:
  US05/904,868
• Time in Patent Office: 593 Days
• Field of Search: 264/242, 264/250, 264/274, 264/299, 264/318, 264/259, 264/275, 264/328, 425/182, 425/190, 251/309, 251/310, 251/314, 251/315, 164/9, 164/98, 164/112, 164/137
• US Class Current: 264/242
• CPC Class Codes: B29C 45/14754 being in movable or releasable engagement with the coating, e.g. bearing assemblies
• CPC Class Codes: F16K 27/067 with spherical plugs
• CPC Class Codes: F16K 5/0689 between housing and plug

Abstract

Method for making a plug valve having a housing molded in place about a pre-formed rotary valvemember. The rotary valve member is molded with the mold parting lines lying in a plane containing the axis of the flow passageway. Around the passageway orifice, the mold parting line is eliminated by use of a core insert which forms a recessed region with an annular mold parting line spaced from the orifice. The housing includes a body portion which surrounds the rotary valve member and an annular lip seal member formed as a homogenous part of the body portion and extending inwardly adjacent the recessed region of the valve member. The inwardly extending portion of the lip seal member has the property of flexing to form a fluid-tight seal when the valve member is in its closed position. On valves having non-threaded end sockets, an annular reservoir is provided between the lip seal member and the socket portion to prevent solvent or cement from contacting the lip seal member when the valve is connected to a pipeline by use of solvent welding.

Claims

1. A method of molding a rotary plug for use in a plug valve having a housing with seating faces, said plug being rotatably mountable within the housing and including a curved exterior surface which is engageable with the seating faces, said method comprising the steps of:

providing a pair of mold halves having cavity walls which form a first exterior surface portion of said plug to be substantially symmetrical about a turning axis of the plug;

placing a pair of core sections end-to-end for forming a through passageway through the plug, said cores having annular flange faces which form second exterior surface portions of said plug, defining annular seat-engaging surface areas which surround outer edges of both ends of the passageway to be formed and which are to engage inner ends of the seating faces in an open position of the plug; and

introducing molten molding material into the mold around said core and against said annular flange faces and hardening said material to form said plug with first mold parting lines on opposite sides of the plug lying in a plane containing the axis of the through passageway except at said annular seat-engaging surface areas where second parting lines between the mold cavity halves and the flange faces of said cores define a closed curve symmetrical about the axis of the through passageway, so that when said rotary plug is disposed within the valve housing, said inner ends of said seating faces avoid contact with mold parting lines in both the open and closed positions of said plug.

2. A method according to claim 1, wherein said step of placing a pair of core sections comprises placing core sections having annular flange faces which form annular seat-engaging surface areas which are recessed inwardly relative to the curvature of said first exterior surface portions of said plug so that seating faces which are engaged by said recessed annular surface areas in an open position of said plug are engaged more firmly by said first exterior surface portions of the plug.

3. A method of molding a rotary ball for use in a ball valve having a housing with seating faces, said ball valve being rotatably mounted within the housing and including a generally ball-shaped exterior surface which is engageable with the seating faces, said method comprising the steps of:

providing a pair of mold halves having cavity walls which form a first, substantially spherical exterior surface portion of said ball to be substantially symmetrical about a turning axis of the ball;

placing a pair of core sections end-to-end for forming a cylindrical passageway through the ball, said cores having annular flange faces which form second exterior surface portions of said ball, defining annular seat-engaging surface areas that are recessed inwardly relative to said first exterior surface portion of said ball and which surround outer edges of both ends of the passageway so as to be engageable with inner ends of the seating faces in an open position of said ball; and

introducing molten molding material into the mold around said core to form said ball with first mold parting lines on opposite sides of the ball lying in a plane containing the axis of the cylindrical passageway except at said annular seat-engaging surface areas where second parting lines between the mold cavity halves and the flange faces of said cores define a circle substantially concentric with the axis of the cylindrical passageway, so that when said rotary ball is disposed within the valve housing, said inner ends of said seating faces avoid contact with mold parting lines in both the open and closed positions of said ball.

4. A method for molding a rotary plug valve including a rotary plug disposed in a housing having seating faces, said plug being rotatably mounted in the housing and including an exterior surface which is engageable with the seating faces to block the travel of fluid, said method comprising the steps of:

molding the rotary plug having a first exterior surface portion, a through passageway with orifices at opposite ends surrounded by second exterior surface portions comprising annular seat-engaging surface areas that are recessed inwardly relative to said first exterior surface portion of said plug, said plug having first mold parting lines lying on opposite sides in a plane containing the axis of said flow passageway except for said annular seat-engaging areas which are surrounded by second mold parting line defining a closed curve symmetrical about the axis of said flow passageway;

providing a pair of housing mold cavities having parting faces lying in a plane containing the turning axis of said plug;

providing a pair of core inserts adapted to be placed in an end-to-end relationship into the plug passageway and each having an annular face extending radially outwardly a first distance toward the walls of the mold cavity;

mounting said plug into said housing mold cavity with the core inserts extending into passageway and with said annular faces spaced from said recessed annular seat-engaging surface areas by a second distance;

introducing molten molding material into said housing mold halves around said core inserts and into the spaces between said annular faces and said recessed annular seat-engaging surface areas on both sides of said plug, said first distance being sufficiently large to provide annular lips extending radially inwardly from an inner wall of said housing to a location disposed radially inwardly of an outer diameter of said recessed annular seat-engaging areas of said plug, said second distance being sufficiently large to allow a complete fill out of molten material which fuses properly along the knit line but sufficiently small so that the inner ends of the lips, which define said seating faces, having the property of flexing in response to engagement with said first external surface portion to form a fluid-tight seal with said first exterior surface portion of the plug when the ball is rotated to a valve closed position;

hardening said molding material; and

removing said molded valve housing from said mold halves with the rotary plug in place after the housing material has set.

5. The method as defined in claim 4, wherein the first distance is between about 1/10th inch and 1/8th inch, and the second distance is between about 0.03 and 0.05 inch.

6. The method as defined in claim 4, wherein said step of molding the rotary plug comprises the steps of:

providing a pair of mold halves having cavity walls which form said exterior surface portion of said plug to be substantially symmetrical about a turning axis of the plug;

placing a pair of core sections end-to-end for forming said through passageway through the plug, said cores having annular flange faces which form said second exterior surface portions of said plug, defining said recessed annular seat-engaging surface areas which surround outer edges of both ends of the passageway to be formed and which are to engage inner ends of the seating faces in an open position of the plug; and

introducing molten molding material around said core and against said annular flange faces and hardening said material to form said plug with said first and second mold parting lines so that when said rotary plug is disposed, within the valve housing, said inner ends of said seating faces avoid contact with mold parting lines in both the open and closed positions of said plug.

7. A method for molding a rotary ball valve including a rotary ball disposed in a housing having sealing faces, said ball being rotatably mounted in the housing and including an exterior surface which is engageable with the seating faces, said method comprising:

molding the rotary ball having a first, substantially spherical exterior surface portion, a through flow passageway with circular orifices at opposite ends surrounded by second exterior surface portions comprising annular seat-engaging surface areas that are recessed inwardly relative to said spherical first exterior surface portion of said ball, said ball having first mold parting lines lying on opposite sides in a plane containing the axis of said flow passageway except for said annular seat-engaging surface areas which are surrounded by second mold parting lines defining circles substantially concentric with the axis of said flow passageway;

providing a pair of housing mold cavities having parting faces lying in a plane containing the turning axis of said ball;

providing a pair of core inserts adapted to be placed in an end-to-end relationship into the ball passageway and each having an annular face extending radially outwardly a first distance toward the walls of the surrounding mold cavity;

mounting said ball into said housing mold cavity with said core inserts disposed within the ball passageway and with said annular faces spaced from said recessed annular seat-engaging surface areas by a second distance;

introducing molten molding material into said housing mold halves around said core inserts and into the spaces between said annular faces and said recessed annular seat-engaging surface areas on both sides of said ball, said first distance being sufficiently large to provide annular lips extending radially inwardly from an inner wall of the housing to a location disposed radially inwardly of an outer diameter of said recessed annular seat-engaging surface areas of said rotary ball and with said ball being in an open position;

said second distance being sufficiently large to allow a complete fill-out of molten material which fuses properly along the knit line but sufficiently small so that the inner ends of the lips which define said seating faces, have the property of flexing in response to engagement with said first exterior surface portion to form a fluid-tight seal with the first exterior surface portion of the ball when the ball is rotated to a valve-closed position;

hardening said molding material; and

removing the molded valve housing from said mold halves with the rotary ball in place after the housing material has set.

8. The method as defined in claim 7, wherein the first distance is between about 1/10th and 1/8th inch, and the second distance is between about 0.03 and 0.05 inch.

9. The method as defined in claim 7, wherein said step of molding the rotary ball includes the steps of:

providing a pair of mold halves having cavity walls which form said first, substantially spherical, exterior surface portion of said ball to be substantially symmetrical about a turning axis of the ball;

placing a pair of core sections end-to-end for forming a cylindrical passageway through the ball, said cores having annular flange faces which form said second exterior surface portions of said ball, defining said recessed annular seat-engaging surface areas; and

introducing molten molding material into the mold around said core to form said ball with said first and second mold parting lines, so that when said rotary ball is disposed within the valve housing, said inner ends of said seating faces avoid contact with mold parting lines in both the open and closed positions of said ball.