Molded plastic elbow

Abstract

An improved molded plastic elbow and a related mold assembly and manufacturing method are provided, wherein the elbow defines an internal flow path having a smoothly radiused inside turn. The elbow is formed by injecting plastic material into a tubular mold cavity formed by closed mold members in cooperation with a pair of slidably retractable core units of circular cross section and having distal ends in mating, angularly set end-to-end contact to form the internal flow path having a turn formed along the length thereof. Each core unit comprises an outer core pin to form an outer portion of the flow path and including a ramped track for slide-fit mounting of an inner slide segment which forms an inner portion of the flow path and further includes a curved inside edge to form a portion of the smoothly radiused inside turn. Initial retraction of each outer core pin from the mold cavity permits relative advancement of the inner slide segment along the ramped track toward a centerline of the flow path, sufficiently for the curved inside edge of the inner slide segment to clear the radiused inside turn of the molded elbow and thereby enable interference-free linear withdrawal of the core unit from the molded plastic part.

What is claimed is:  
     
         1 . A molded plastic body comprising a unitary molded plastic element defining an elbow-shaped internal flow path, said internal flow path having a turn of about 90° formed along the length thereof with a smoothly radiused inside turn surface.  
     
     
         2 . The molded plastic body of  claim 1  wherein said internal flow path has a circular cross section.  
     
     
         3 . The molded plastic body of  claim 1  wherein said body comprises a molded plastic and generally tubular fitting for interconnecting a pair of fluid pipes.  
     
     
         4 . The molded plastic body of  claim 3  wherein said molded plastic element further includes means generally at opposite ends thereof for connection to the pair of pipes.  
     
     
         5 . The molded plastic body of  claim 3  wherein said turn along said flow path further includes a smoothly radiused outside turn surface.  
     
     
         6 . The molded plastic body of  claim 1  wherein said body comprises a molded plastic valve body for use in controlling fluid flow.  
     
     
         7 . A mold assembly for making a molded plastic body having an elbow-shaped internal flow path defined by a smoothly radiused inside turn surface, said mold assembly comprising: 
 a pair of mold members adapted for movement to a closed position to define a mold cavity having a shape conforming to the exterior geometry of a body to be molded; and    a pair of retractable core units each movable between an advanced position protruding into said mold cavity and cooperating with each other to define an internal flow path in the body to be molded, and a retracted position substantially withdrawn from said mold cavity;    said core units having angularly set distal end faces for abutting end-to-end engagement with each other when said core units are in said advanced positions to define the internal flow path with a turn formed along the length thereof;    each of said core units comprising an outer core pin defining an outer portion of the internal flow path and including a ramped track extending longitudinally and angularly inwardly from a distal end thereof, and an inner slide segment defining an inner portion of the internal flow path, said inner slide segment being movably carried on said ramped track and including a curved inner edge disposed generally at a distal end thereof, wherein said curved inner edges of said inner slide segments of said core units cooperatively define a smoothly radiused inside turn surface of the internal flow path;    said inner slide segment of each of said core units being movable along said ramped track on the associated outer core pin upon movement of said core unit toward said retracted position subsequent to molding of said body within said mold cavity, to shift said inner slide segment in an outward direction relative to a centerline of the internal flow path sufficiently for interference-free withdrawal of said core unit from said mold cavity and said body molded therein.    
     
     
         8 . The mold assembly of  claim 7  wherein said core units cooperatively define the internal flow path to have a generally circular cross sectional shape.  
     
     
         9 . The mold assembly of  claim 7  further including insert means cooperating with said mold members to form connection means on the body to be molded for interconnecting the body to a pair of pipes.  
     
     
         10 . The mold assembly of  claim 7  wherein the turn formed along the length of the internal flow path comprises a turn of about 90°.  
     
     
         11 . The mold assembly of  claim 7  wherein said body comprises an elbow fitting.  
     
     
         12 . The mold assembly of  claim 7  wherein said body comprises a valve body.  
     
     
         13 . The mold assembly of  claim 7  wherein said angularly set distal end faces on said core units comprise angularly set distal end faces on the distal ends of said outer core pins for abutting end-to-end engagement with each other when said core units are in said advanced positions, and angularly set distal end faces on the distal ends of said inner slide segments for abutting end-to-end engagement with each other when said core units are in said advanced positions, said core pins and said inner slide segments cooperatively defining the internal flow path with the turn formed along the length thereof when said core units are in said advanced positions.  
     
     
         14 . The mold assembly of  claim 12  further including interlocking means on said distal end faces of said core pins for interlocking said core pins when said distal end faces are in abutting end-to-end engagement.  
     
     
         15 . The mold assembly of  claim 7  further including interengaging key and slot means formed on said outer core pin and said inner slide segment of each of said core units, for slidably guiding said inner slide segment along said ramped track.  
     
     
         16 . The mold assembly of  claim 14  further including means for limiting displacement of said inner slide segment along said ramped track to prevent separation of said inner slide segment from said outer core pin.  
     
     
         17 . A method of making a molded plastic body wherein the fitting includes an internal flow path having a turn formed along the length thereof defined by a smoothly radiused inside turn surface, said method comprising the steps of: 
 forming a mold cavity having a shape conforming to the exterior geometry of a body to be molded;    advancing a pair of core units to protrude into the mold cavity in end-to-end abutting engagement with each other to cooperatively define an internal flow path through the body to be molded with a turn formed along the length of the internal flow path;    each of the core units comprising an outer core pin defining an outer portion of the internal flow path and including a ramped track extending longitudinally and angularly inwardly from a distal end thereof, and an inner slide segment defining an inner portion of the internal flow path and being movably carried on the ramped track and further including a curved inner edge disposed generally at a distal end thereof to define a portion of a smoothly radiused inside turn surface of the internal flow path;    injecting plastic material into the mold cavity to form the body; and    retracting each of the core units from the mold cavity, said retracting step comprising retracting the outer core pin to permit movement of the inner slide segment along the ramped track of said outer core pin to shift the inner slide segment in an outward direction relative to a centerline of the internal flow path sufficiently for interference-free withdrawal of the core unit from the mold cavity and the body molded therein.