US4026983A — Method of producing seamless tubular articles hav…

Claim 1

Independent Claim 301 words

A method for producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing partable mating die members having mold cavity portions which cooperate, when said die members are closed, to define a cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed: advancing downwardly a depending tubular length of pliable thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; while said tubular parison continues advancing downwardly, causing relative movement between the depending end of and the remainder of said tubular length while still pliable, first in a direction lateral to the tubular axis of said length as downwardly advanced and then in an upward direction generally opposed to the tubular axis of said length as advanced to cause a portion of said tubular length to sag into a loop that has the general shape of the arcuate portion of the article being formed but to cause a straight portion of said tubular length, having the general shape of the straight portion of the article being formed, into which the arcuate tubular length portion leads, to remain; closing said die members about said tubular length with said arcuate and said straight portion lying inside said mold cavity; introducing a blow molding duct into said tubular length to provide communication with the interior thereof; introducing fluid under pressure through said duct to force the wall of said tubular length outwardly into contact with the surface of said mold cavity; separating said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die cavity portions.

Claim 2

Independent Claim 301 words

A method for producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing partable mating die members having mold cavity portions which cooperate, when said die members are closed, to define a cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed: advancing downwardly a depending tubular length of pliable thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; while said tubular parison continues advancing downwardly, causing relative movement between the depending end of and the remainder of said tubular length while still pliable, first in a direction lateral to the tubular axis of said length as downwardly advanced and then in an upward direction generally opposed to the tubular axis of said length as advanced to cause a portion of said tubular length to sag into a loop that has the general shape of the arcuate portion of the article being formed but to cause a straight portion of said tubular length, having the general shape of the straight portion of the article being formed, into which the arcuate tubular length portion leads, to remain; closing said die members about said tubular length with said arcuate and said straight portion lying inside said mold cavity; introducing a blow molding duct into said tubular length to provide communication with the interior thereof; introducing fluid under pressure through said duct to force the wall of said tubular length outwardly into contact with the surface of said mold cavity; separating said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die cavity portions.

Claim 3

Independent Claim 300 words

A method for producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing partable mating die members having mold cavity portions which cooperate, when said die members are closed, to define a cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed; downwardly extruding a length of tubular parison of heated pliable thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; while the tubular parison continues to be extruded downwardly, causing relative movement between the depending end of and the remainder of said tubular parison while still pliable, first in a direction lateral to the tubular axis of said parison as downwardly extruded and then in an upward direction generally opposed to the tubular axis of said parison as extruded to cause a portion of said parison to sag into a loop that has the general shape of the arcuate portion of the article being formed, but to cause a straight portion of said tubular parison, having the general shape of the straight portion of the article being formed and into which the arcuate parison portion leads, to remain; closing said die members about said tubular parison with said arcuate and said straight portions lying inside said mold cavity; introducing a blow molding duct into said parison to provide communication with the interior thereof; introducing fluid under pressure through said duct to force the parison wall outwardly into contact with the surface of said mold cavity; separating said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die cavity portions.

Claim 4

Independent Claim 300 words

A method for producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing partable mating die members having mold cavity portions which cooperate, when said die members are closed, to define a cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed; downwardly extruding a length of tubular parison of heated pliable thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; while the tubular parison continues to be extruded downwardly, causing relative movement between the depending end of and the remainder of said tubular parison while still pliable, first in a direction lateral to the tubular axis of said parison as downwardly extruded and then in an upward direction generally opposed to the tubular axis of said parison as extruded to cause a portion of said parison to sag into a loop that has the general shape of the arcuate portion of the article being formed, but to cause a straight portion of said tubular parison, having the general shape of the straight portion of the article being formed and into which the arcuate parison portion leads, to remain; closing said die members about said tubular parison with said arcuate and said straight portions lying inside said mold cavity; introducing a blow molding duct into said parison to provide communication with the interior thereof; introducing fluid under pressure through said duct to force the parison wall outwardly into contact with the surface of said mold cavity; separating said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die cavity portions.

Claim 5

Dependent Claim 48 words

The method for producing a tubular article having an arcuate portion along its tubular axis as claimed in claim 2, further comprising the steps of: closing a first end of said tubular parison, and thereafter introducing said blow molding duct into said tubular parison while in said mold.

Claim 6

Dependent Claim 84 words

The method for producing a tubular article having an arcuate portion along its tubular axis as claimed in claim 3, wherein said first parison end is the depending end and wherein said method further comprises the step of: continuously extruding said parison; severing said parison, after sufficient length has been extruded to form said tubular article and this has been enclosed in said molding die, to form a trailing end of the severed length and introducing said blow molding duct into said trailing end.

Claim 7

Dependent Claim 105 words

The method for producing a tubular article having an arcuate portion along its tubular axis as claimed in claim 2, wherein said mating die members are separable along an axial plane of the article coincident with the axial plane of its arcuate portion, and wherein said die members are also translationally movable in a direction parallel to said plane between first and second stations, whereby at one of said stations said die members are offset from said parison so as not to interfere with its extrusion and bending, while at the other of said stations said die members are in flanking relation to said parison.

Claim 8

Dependent Claim 54 words

The method for producing a tubular article having arcuate portion along its tubular axis as claimed in claim 2, further comprising the step of: selectively increasing extrusion pressure on said thermoplastic resin as it is extruded to increase the amount of resin extruded at locations on said parison where increased wall thickness is desired.

Claim 9

Dependent Claim 44 words

The method for producing a tubular article having arcuate portion along its tubular axis as claimed in claim 2, further comprising the step of: introducing pressure into the interior of said parison during extrusion to prevent collapse of said parison during the bending thereof.

Claim 10

Dependent Claim 74 words

The method for producing a tubular article having an arcuate portion along its tubular axis as claimed in claim 2, wherein said parison is extruded from a die having a hole defining the outside shape of said parison and a mandrel defining the inside shape of said parison, said method further comprising the step of: shifting said mandrel relative to said hole to change the parison wall thickness along the length of the parison.

Claim 11

Dependent Claim 29 words

The method as defined in claim 8, which includes shifting said mandrel eccentrically of said hole in said die to change the parison wall thickness circumferentially of the parison.

Claim 12

Independent Claim 383 words

A method of producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing shiftable mating die members partable in a direction perpendicular to the direction of shift and having mold cavity portions which cooperate when said die members are clamped together to define a mold cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed; downwardly extruding a depending tubular parison of heated thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; grasping the leading end of said parison while it advances downwardly and thereby causing relative movement between the depending end of and the remainder of said tubular parison in the parting plane of said die members while said parison is still pliable first in a direction lateral to the tubular axis of said parison as downwardly extruded and then in an upward direction generally opposed to the tubular axis of said parison as extruded to cause said parison to sag into a loop intermediate its length into the general shape of the arcuate portion of the article to be formed and to cause it to have a straight portion having the general shape of the straight portion of the article to be formed into which the arcuate parison portion leads; shifting said die members while parted to a position flanking the arcuate and straight portions of said parison and then closing said members with said arcuate and straight parison portions lying inside said mold cavity; severing said enclosed arcuate and straight portions from the remainder of the parison and shifting said closed die members away from the region where it would interfere with the continued extrusion of the remainder of the parison; introducing a blow molding duct into the severed end of the parison in said mold cavity to provide fluid communication with the parison interior; introducing fluid under pressure through said duct to force the parison walls outwardly into contact with the surface of said mold cavity; parting said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die members.

Claim 13

Independent Claim 383 words

A method of producing a seamless tubular article having an arcuate portion along its tubular axis that leads into at least one straight portion, said method comprising the steps of: providing shiftable mating die members partable in a direction perpendicular to the direction of shift and having mold cavity portions which cooperate when said die members are clamped together to define a mold cavity having an arcuate section that leads into at least one straight section configured to the external shape of the article to be formed; downwardly extruding a depending tubular parison of heated thermoplastic resin having an outside diameter slightly less than the outside diameter of the article to be formed; grasping the leading end of said parison while it advances downwardly and thereby causing relative movement between the depending end of and the remainder of said tubular parison in the parting plane of said die members while said parison is still pliable first in a direction lateral to the tubular axis of said parison as downwardly extruded and then in an upward direction generally opposed to the tubular axis of said parison as extruded to cause said parison to sag into a loop intermediate its length into the general shape of the arcuate portion of the article to be formed and to cause it to have a straight portion having the general shape of the straight portion of the article to be formed into which the arcuate parison portion leads; shifting said die members while parted to a position flanking the arcuate and straight portions of said parison and then closing said members with said arcuate and straight parison portions lying inside said mold cavity; severing said enclosed arcuate and straight portions from the remainder of the parison and shifting said closed die members away from the region where it would interfere with the continued extrusion of the remainder of the parison; introducing a blow molding duct into the severed end of the parison in said mold cavity to provide fluid communication with the parison interior; introducing fluid under pressure through said duct to force the parison walls outwardly into contact with the surface of said mold cavity; parting said die members after the plastic has cooled sufficiently to rigidify; and stripping the molded tubular article from said die members.

Claim 14

Dependent Claim 68 words

The method of producing a seamless tubular article having an arcuate portion along its tubular axis as claimed in claim 10, wherein the loop forming operation comprises the steps of: pivoting said closed parison end on a radius about a fixed point to cause said parison to loop downwardly intermediate its length to form the arcuate portion prior to clamping said die members together about said loop portion.

Claim 15

Dependent Claim 58 words

The method as defined in claim 10, wherein the loop forming operation comprises the steps of: horizontally moving said closed parison end at a rate correlated to the rate of parison extrusion to cause said parison to loop downwardly intermediate its length to form the arcuate portion prior to clamping said die members together about said loop portion.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1980-05-30	1980-11-29	1981-05-31	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1984-05-30	1984-11-29	1985-05-31	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1988-05-30	1988-11-29	1989-05-31	$7700.00	Window Closed / Lapsed

Method of producing seamless tubular articles having an arcuate portion along the tubular axis

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