Method of belling plastic pipe and apparatus therefor

An improvement in the method of belling plastic pipe wherein a section of pipe is conveyed to a first station in which at least one end of the pipe is subjected to heating to soften the pipe-end, said pipe-end having an annular edge wall, the pipe is then moved to a second station for insertion of a belling mandrel into the heat-softened end of the pipe, following which insertion the pipe-end is cooled and the inserted mandrel is withdrawn, said improvement comprising:

• a. Providing at said second station where the heat-softened pipe-end is disposed, a pair of mating mold halves spaced from each other, each of said mold halved defining a portion of a cavity, said cavity having (i) a first inner portion which coincides with the outside diameter of the plastic pipe as it arrives in the second station and is disposed inwardly of the softened pipe-end;
• and, (ii) a second portion with an inside diameter greater than the said outside diameter of the pipe-end and defining the outer configuration desired for the finally belled pipe-end;
• said second portion of the cavity extending from the first inner portion out beyond the softened pipe-end when in said second station;
• and bringing said mold halves together under great pressure about the softened pipe-end;
• b. Extending said softened pipe-end into said mold cavity by inserting a mandrel axially into the softened pipe-end immediately after said mold halves have been brought together thereabout, said mandrel comprising a leading substantially cylindrical nose having an outside diameter just sufficiently smaller than the inside diameter of the pipe-end so as to be insertable therein;
• and a following section configured similar to said second portion of the mold cavity but externally dimensioned to provide between the walls of said following section and the inside walls of the cavity, spacing substantially equal to the thickness desired for the wall of the end of the pipe after it is belled;
• c. Axially compressing the expanded pipe-end by forcing a sleeve, slidable coaxially about the said following section of the mandrel, over the latter section and toward the leading cylindrical section of the mandrel, said sleeve presenting an annular edge face to the edge wall of the heat-softened expanded end and having an outside diameter just sufficiently less than the inside diameter of the portions of the molds defining the second portion of the cavity so as to be slidable into said second portion of the cavity when said mold halves are closed together under pressure;
• whereby, when said mold halves are so closed together under pressure about a heat-softened pipe and said mandrel is forced into the open end of the cavity defined by the mold halves, the leading nose of the mandrel will slide into the heat-softened pipe-end beyond the second portion of the mold cavity and into the first portion thereof, while the following section of the mandrel forces the heat-softened pipe-end outwardly to assume the configuration of the space between the said following section and the mold walls defining the second portion of the mold cavity;
• and the said annular edge face of the sleeve, when the sleeve is forced axially against the end of the expanded pipe-end, compresses the softened pipe-end axially in said space;
• d. Cooling the pipe-end while said pipe-end is retained in the mold cavity and with the mandrel still inserted in the pipe-end and said sleeve is providing axial compression;
• and,
• e. Thereafter retracting the sleeve, withdrawing the mandrel, opening the mold halves, and removing the pipe with its thus-belled end.

The improvement in the method of belling plastic pipe wherein a section of pipe is conveyed to a first station in which at least one end of the pipe is subjected to heating to soften the pipe-end and the pipe is then moved to a second station for the insertion into the pipe through the heat-softened end thereof, a belling mandrel, following which insertion the pipe-end is cooled, and then the mandrel is withdrawn from the pipe-end and the pipe is ejected from the second station, the improvement comprising,

• a. Bringing together about the heat-softened pipe-end after the pipe has been moved to its second station, a pair of mating mold halves, each of said mold halves defining one half of a cavity, said cavity having
• i. A first inner portion which coincides with the outside diameter of the plastic pipe as it is disposed in the second station and is disposed about the inner area of the softened pipe-end;
• and,
• ii. A second portion with an inside diameter greater than the outside diameter of the pipe-end and defining the desired outer configuration for the pipe-end after its belling, said second portion of the cavity extending from the first inner portion beyond the extremity of the softened pipe-end when disposed in said second station;
• b. Forcing the heat-softened pipe-end radially outwardly against the walls of the mold halved defining said cavity by inserting axially into the heat-softened pipe-end a mandrel, said mandrel having an outside configuration similar to that of the mold walls defining the cavity but with dimensions sufficiently smaller to provide, when said mandrel is disposed within said mold cavity, a space between the mandrel and the mold walls of the desired thickness of the pipe-end after belling is completed;
• c. Compressing the thus-expanded pipe-end axially within said mold halves through the open end thereof by moving a sleeve-like ram over the mandrel into said annular space between the mandrel and the mold walls and against the pipe-end;
• d. Cooling the pipe-end while said pipe-end is retained in the mold cavity with the mandrel still inserted in the pipe-end and with the sleeve still providing axial compression;
• and,
• e. After sufficient cooling of the mandrel, first retracting the sleeve axially along the mandrel, then withdrawing the mandrel and opening the mold halves and removing the pipe with its thus-belled end.

Apparatus for compression molding an end of the thermo-plastic pipe to bell the same, said apparatus comprising:

• a. A heating area to heat-soften the end of the pipe;
• b. A belling station;
• c. Conveyor means to dispose the end of a pipe to be belled in said heating area and to retain said pipe-end in said heating area for a predetermined period to heat-soften said pipe-end and then to move the pipe transversely to its axis so that said heat-softened pipe-end is disposed in the belling station;
• d. A belling mandrel, said belling mandrel being co-axially aligned with, but, in its first position, spaced from the heat-softened end of said pipe, said mandrel being movable from its said first position to a second position wherein the mandrel is inserted in the heat-softened pipe-end, said mandrel having a leading substantially cylindrical nose with an outside diameter just sufficiently smaller than the inside diameter of the pipe so as to be insertable therein, and a following section configured to the desired internal configuration of the finally belled pipe-end;
• e. A pair of mating mold halves, said mold halves being disposed in transverse alignment with the heat-softened pipe-end when disposed in said belling station, and said mold halves being movable from a first position spaced from each other to a second position wherein said mold halves are tightly closed together about the heat-softened pipe-end, when in said belling station each of said mold halves defining one-half of a cavity, said cavity having
• i. A first inner portion which coincides with the outside diameter of the plastic pipe as it arrives in the belling station, and is disposed inwardly out of the softened pipe-end;
• and
• ii. A second portion with an inside diameter greater than the outside diameter of the pipe-end and defining the outer configuration desired for the finally belled pipe-end, said second portion of the cavity the outer configuration desired for the finally belled pipe-end, said second portion of the cavity extending from the first inner portion axially beyond the softened pipe-end when disposed in said belling station, the walls of the mold halves when so closed together defining said cavity and being spaced from the following section of the mandrel by the thickness of the walls desired for the pipe-end after belling.
• f. A compression sleeve, said sleeve having an inside diameter just sufficiently greater than the outside diameter of the following section of the mandrel as to be slidable thereover, and an outside diameter just sufficiently smaller than the inside diameter of the mold walls defining the second portion of the cavity as to be slidable therein, said sleeve having an annular end edge face, and said sleeve being slidable over said mandrel between a first position remote from the mandrel nose and a second position over the following section of the mandrel toward said mandrel nose to contact said transverse annular end wall of the pipe-end;
• g. Means to force said sleeve slidably axially over said mandrel after said mandrel has been inserted in said heat-softened pipe-end from the sleeve's first position to its second position to cause said annular end edge face to contact and compress the said annular end wall of the heat-softened pipe-end as it is disposed in the spacing between the walls of the mold halves defining said cavity and the following section of the mandrel, said means to force being disposed symmetrically about the axis;
• h. Means to cool the heat-softened pipe-end after said compression and mandrel insertion has occurred;
• i. Means to retract said sleeve back along said mandrel to its first position;
• j. Means to retract said mandrel back to its first position;
• k. Means to move said mold halves back to their respective first positions;
• and
• l. Means to eject the belled pipe from its disposition wherein its end is in said belling station.

The combination of

• a. A core element;
• b. A sleeve element fitting closely about said core element but slidably axially relative to said core element;
• c. Means to move each of said core element and said sleeve element reciprocably relative to each other, said means comprising:
• i. A first elongated member connected to, and co-axially extending from the core element in one direction;
• ii. A first housing co-axially surrounding a portion of said elongated member distally from the core element, said first housing having end walls each of which is orificed to encompass said first elongated member closely but slidably therethrough;
• iii. A first piston surrounding and secured to said first elongated member and reciprocable in said first housing, said first housing having means to admit pressure fluid to one or the other of its opposite ends, thereby to drive said first piston reciprocably in said first housing and to move with said first piston and said first elongated member and said core element;
• iv. An outer tubular member connected to said sleeve element and extending co-axially about a portion of the first elongated member in said one direction;
• v. A second housing axially spaced from the first housing, said second housing being intermediate the first housing and said sleeve element, said second housing surrounding co-axially said outer tubular member and having end walls each of which is orificed to encompass said outer tubular member closely but slidably therethrough;
• vi. A second piston reciprocable in said second housing and secured to said outer tubular member, said second housing also having means to admit pressure fluid alternatively to its opposite ends;
• thereby to drive said second piston reciprocably in said second housing and to move with said second piston, said outer tubular member and said sleeve;
• and
• vii. Stationary mounting means, said mounting means including means to hold fixedly in co-axial alignment both of said first and second housings.

The combination of

• a. A cylindrical core element;
• b. A co-axial cylindrical sleeve element surrounding said core element but slidably axially relative to said core element;
• c. Means to move each of said cylindrical element and said sleeve element reciprocably relative to each other, said means comprising:
• i. A first elongated cylindrical extension member connected co-axially to and extending from the core element in one direction;
• ii. A first cylinder co-axially surrounding a portion of said cylindrical extension member distally from the core element, said first cylinder having end walls each of which is orificed to encompass said first cylindrical extension member closely but slidably therethrough;
• iii. A first annular piston surrounding and secured to said cylindrical extension member and reciprocable in said first cylinder, said first cylinder having means to admit pressure fluid to one or the other of its opposite ends, thereby to drive said first annular piston reciprocably in said cylinder and to move with said first piston said first extension member and said core element;
• iv. An outer tubular member connected to said sleeve element and extending co-axially about a portion of the first elongated cylindrical extension member in said one direction;
• v. A second cylinder axially spaced from the first cylinder, said second cylinder being intermediate the first cylinder and said sleeve element, said second housing surrounding co-axially said outer tubular member, and having end walls each of which is orificed to encompass said outer tubular member closely but slidably therethrough;
• vi. A second annular piston reciprocable in said second cylinder and secured to said outer tubular member, said second cylinder also having means to admit pressure fluid alternatively to its opposite ends thereby to drive said second piston reciprocably in said second cylinder and to move with said second piston, said outer tubular member and said sleeve;
• and,
• vii. Stationary mounting means, said mounting means including means to hold fixedly in coaxial alignment both said first and second cylinders.