초록

A flange can be formed on the end of a plastic pipe utilizing a die and mold which define a flange shaped mold cavity which expands under the pressure of compression plastic flow of pipe as the cavity is filled with a near molten end of the thermo-plastic pipe and the flange is being formed.

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1. A method for forming a flange on the end of a thermoplastic pipe, said method comprising (a) positioning a first end of a thermoplastic pipe in a first generally tubular portion of a mold cavity formed between a die and a mold, said mold cavity having a closed end formed by a portion of the di

1. A method for forming a flange on the end of a thermoplastic pipe, said method comprising (a) positioning a first end of a thermoplastic pipe in a first generally tubular portion of a mold cavity formed between a die and a mold, said mold cavity having a closed end formed by a portion of the die; (b) urging at least one of the first end of the thermoplastic pipe and the die portion forming the closed end of the cavity toward the other with sufficiently great a force to move the portion of the die forming the end of the mold cavity to form a second generally tubular portion of the mold cavity connected to the first generally tubular portion of the mold cavity; and (c) flowing the first end of the pipe into the second generally tubular portion of the mold cavity as it is formed. 2. A method as in claim 1 wherein (a) the die is resiliently urged toward the first tubular portion of the mold cavity; and (b) the force between the die portion closing the end of the mold cavity and the first end of the thermoplastic pipe is sufficiently great to overcome the resilient urging of the die against the mold, thereby causing the die to move away from the mold and the second generally tubular portion of the mold cavity to be formed between the die and the mold. 3. A method as in claim 2 further comprising heating the first end of the pipe to a sufficiently high temperature to cause it to become plastic but not sufficiently high to cause it to decompose prior to or during the positioning of the first end of the pipe in the first generally tubular portion of the mold cavity. 4. A method as in claim 3 further comprising pressurizing the first end of the pipe to a pressure of between about 500 and 1500 pounds per square inch after it has flowed into the second generally tubular portion of the mold cavity and then cooling the first end of the pipe. 5. A method for forming an end on a thermoplastic pipe comprising (a) providing a thermoplastic pipe having a longitudinal axis, a first end and a second end, wherein a portion of the pipe adjacent the first end at a molding temperature, and a portion of the pipe adjacent the second end is at a temperature below molding temperature; (b) positioning the heated end portion of the pipe between a collar which closely fits the outside of the pipe and a pin which closely fits the inside of the pipe; (c) flowing at least a portion of the heated end of the pipe longitudinally between the pin and the collar; and (d) flowing at least a portion of the pipe generally radially outwardly and into a flange shaped cavity from between the pin and the collar. 6. A method as in claim 5 wherein the flange shaped cavity expands in a longitudinal direction as the portion of the pipe flows thereinto. 7. A method as in claim 6 wherein the expanding flange-shaped cavity is at least partially defined by a portion of the collar, and the collar moves in a longitudinal direction toward the second end of the pipe as the cavity expands. 8. A method as in claim 7 wherein the pin moves in a longitudinal direction past the cavity as it expands. 9. Apparatus comprising (a) a mold defining a borehole having a shoulder therein, a first portion of said borehole having a first diameter and a second portion of said borehole having a second diameter, (b) a die having a shoulder on its exterior surface positioned in the mold, a first portion of the die having a third diameter and a second portion of the die having a fourth diameter, said die being longitudinally movable in the borehole from a first position in which at least a portion of the shoulder of the die is adjacent to at least a portion of the shoulder of the mold to a second position in which a generally tubular mold cavity is defined between the die and the mold, said cavity being at least partially defined between the shoulder in the borehole and the shoulder of the die; (c) at least one spring cooperating with the die so as to become compressed when the die is moved into the second position; and (d) a means associated with the at least one spring for limiting the second position of the die. 10. Apparatus as in claim 9 wherein (a) the mold defines a generally cylindrical borehole having a generally annular shoulder therin, and the borehole abruptly expands at the annular shoulder from a first diameter to a second diameter; (b) the die has a first generally cylindrical exterior surface spaced apart from the portion of the borehole having the first diameter, a second generally cylindrical exterior surface positioned adjacent the portion of the borehole having the second diameter, and a generally annular shoulder between the generally cylindrical exterior surface having the first diameter and the generally cylindrical exterior surface having the second diameter, the generally annular shoulder of the die being in juxtaposed relationship with the generally annular shoulder in the borehole; and (c) the at least one spring comprises at least one helical spring. 11. Apparatus as in claim 2 further comprising a means for causing relative closing movement between a tubular workpiece positioned in the generally tubular mold cavity and the mold. 12. Apparatus comprising: (a) a support member defined by a support member basewall having a central aperture therethrough and a skirt depending generally normally from the support member basewall about the exterior perimeter of the support member basewall; and (b) a die defined by a die basewall having an exterior perimeter and a central aperture defined by an interior perimeter said central aperture being larger than the aperture through the support member and a skirt depending generally normally from the die basewall adjacent the interior perimeter of the die basewall, the exterior perimeter of the die basewall being positioned inwardly from the skirt of the support member and in a close fit, and the skirt of the die being positioned on the side of the die basewall away from the aperture in the support member basewall. 13. Apparatus as in claim 12 further comprising (a) a pin positioned inwardly from the skirt of the die having a flange affixed generally normally thereto, said pin having a cross section so as to be closely received by the aperture through the support member basewall and loosely received by the aperture through the die basewall, the flange on the pin being displaced from the skirt of the die, oriented about normally with respect to the skirt of the die, and having a cross sectional dimension through the pin larger than the dimension across the skirt of the die; and (b) a means cooperating with the pin urging the pin toward the aperture through the support member basewall and the flange toward the skirt of the die. 14. Apparatus as in claim 13 wherein (a) the support member has an annularly shaped basewall extending generally radially inwardly from a tubularly shaped skirt; (b) the die has an annularly flange shaped basewall extending generally radially outwardly from a tubularly shaped skirt; and (c) the pin is tubular and the flange affixed to the pin is annular.