DISPOSITIF ET PROCEDE DE FABRICATION D'UN TUYAU AVEC SUREPAISSEUR DES PAROIS AUX EXTREMITES

APPARATUS AND METHOD FOR FORMING A PIPE WITH INCREASED WALL-THICKNESS AT ITS ENDS

Abrégé français

La présente invention concerne un dispositif et un procédé d'extrusion permettant d'obtenir un tuyau de métal dont le diamètre intérieur est uniforme et dont les sections avant et arrière (62, 66) sont plus épaisse que la section centrale(64). Le procédé consiste à introduire une billette de métal (54) présentant un alésage (56) dans l'alésage cylindrique d'un conduit stationnaire (12). La billette (54) est déplacée axialement dans l'alésage du conduit (12) au moyen d'une presse (13) qui comporte une surface de pression (38, 39) et un mandrin (44) entre la surface de pression et la billette (54). Le mandrin (44) comporte une partie cylindrique arrière (48) de grand diamètre (48), une partie cylindrique centrale (50) de petit diamètre et une partie frontale (52) évasée vers l'extérieur et vers l'avant. Le métal de la billette (54) est introduit à force dans l'alésage de faible diamètre d'une première matrice en deux parties déposable (20), autour de la partie centrale (50) du mandrin (44), en faisant avancer la presse sur une première distance de manière à obtenir une section avant préliminaire (62) de tuyau. On continue de faire avancer la presse sur une deuxième distance pour faire passer à force le métal de la billette par l'alésage de la première matrice (51) autour de la partie arrière (48) du mandrin, d'extruder la partie centrale (64) du tuyau, de faire passer la section d'extrémité avant préliminaire (62) du tuyau sur la partie frontale évasée (52) du mandrin et de former la section d'extrémité avant (62) du tuyau. Enfin, on fait avancer la presse sur une troisième distance pour chasser le métal de la billette dans l'alésage relativement important d'une seconde matrice (63) autour de la partie arrière (48) du mandrin et former la section arrière (66) du tuyau.

Abrégé anglais

Apparatus for and method of extruding a metal pipe having a uniform inner
diameter, and forward and rearward end sections (62, 66) which are thicker
than the middle section (64) of the pipe. A metal billet (54) having a bore
(56) is inserted into an open ended cylindrical bore of a stationary container
(12). The billet (54) is moved axially within the bore of the container (12)
by a press (13) which includes a pressing surface (38, 39) and a mandrel (44)
extending forwardly from the pressing surface through the bore of toward the
billet (54). The mandrel (44) has a cylindrical large diameter rearward
portion (48), a cylindrical small diameter middle portion (50) and a forwardly
and outwardly tapering forward portion (52). Metal from the billet (54) is
forced through the small diameter bore of a two part removable first die (20)
around the middle portion (50) of the mandrel (44) by moving the press
forwardly for a first distance to form a preliminary forward end section (62)
of pipe. The press is moved forwardly for a second distance for forcing metal
from the billet through the bore of the first die (51) around the rearward
portion (48) of the mandrel for extruding the middle section (64) of pipe and
causing the preliminary forward end section (62) of pipe to pass over the
tapered forward portion (52) of the mandrel to form the forward end section
(62) of pipe. The press is moved forwardly for a third distance for forcing
metal from the billet through the relatively large bore of a second die (53)
around the rearward portion (48) of the mandrel to form the rearward end
section (66) of pipe.

Revendications

What is claimed:
1. An apparatus for extruding a metal pipe having a substantially uniform
inner
diameter, said pipe having a forward end section, a rearward end section and a
middle section
having an outer diameter which is substantially smaller than the outer
diameter of each of said
forward and rearward sections, said apparatus comprising:
(a) a machine frame;
(b) a container supported on the machine frame, said container having a
central
longitudinal axis and a longitudinal cylindrical first bore coaxial with said
central longitudinal axis for receiving a cylindrical metal billet having a
longitudinal cylindrical bore, said container having a front opening to said
first
bore and a rear opening to said first bore;
(c) a cylindrical inner die having a cylindrical second bore coaxial with said
first
bore, said inner die having an outer diameter equal to the diameter of said
first
bore, said second bore having a diameter which is smaller than the diameter
of said first bore, said inner die being divided longitudinally into two
substantially equal half portions, said inner die being movable through said
front opening along said central longitudinal axis between an inner position
within said first bore adjacent said front opening to an outer position
outside
of said first bore;
(d) an outer die assembly located forward of said container and having a
longitudinal cylindrical third bore which is coaxial with said first and
second
bores and which has a larger diameter than said second bore, one of said outer
die assembly arid said container being movable along said central longitudinal
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axis between an active position wherein said container and said outer die
assembly abut at said front opening and an inactive position wherein said
outer
die assembly and said container are spaced sufficiently to enable said inner
die
to be moved to said outer position for removal from said apparatus;
(e) a press located rearward of said container and movable along said central
longitudinal axis toward and away from said container, said press having a
circular forward pressing surface facing the rear opening of said container
and
a mandrel extending forwardly from said pressing surface toward said rear
opening, said pressing surface and said mandrel being coaxial with said first
bore, said pressing surface having substantially the same outer diameter as
the
inner diameter of said first bore with sufficient clearance to enable said
pressing surface to move longitudinally within said first bore, said mandrel
having a cylindrical rearward portion which has a smaller outer diameter than
the inner diameter of said second bore, a cylindrical middle portion which has
a smaller outer diameter than the outer diameter of said rearward portion, and
a frusto-conical forward portion which extends forwardly from said middle
portion from an outer diameter equal to the outer diameter of said middle
portion to an outer diameter substantially equal to the outer diameter of said
rearward portion; and
(f) an actuator for moving one of said outer die assembly and said container
along said longitudinal axis relative to the other of said outer die assembly
and
said container.
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2. An apparatus as recited in claim 1, wherein the longitudinal length of each
section of said mandrel, relative to the longitudinal length of said inner die
and a specific
billet length being such that said middle portion is within said second bore
when said billet
is pushed forwardly into engagement with said inner die by said press and said
press is
pushed forwardly along said central longitudinal axis a first distance to a
point that said
rearward portion is at the rearward end of said second bore for forcing metal
from said billet
through said second bore around said middle portion for extruding a
preliminary forward end
section of said pipe having an outside diameter which is equal to the diameter
of said second
bore and an inside diameter which is equal to the diameter of said middle
portion, the
forward movement of said press along said central longitudinal axis for a
second distance,
while said rearward portion is within said second bore, causing metal from
said billet to be
forced through said second bore around the rearward portion of said mandrel to
extrude the
middle section of said pipe having an outer diameter which is equal to the
inner diameter of
said second bore and an inner diameter which is equal to the outer diameter of
said rearward
portion, the forward movement of said press for said second distance also
causing the
preliminary forward end section of said pipe to pass over the forward portion
of said mandrel
so that said preliminary forward end section is expanded transversely of said
central
longitudinal axis to form the forward end section of said pipe having an inner
diameter which
is equal to the outer diameter of the rearward portion of said mandrel and a
thickness which
is greater than the thickness of the middle section of said pipe, the forward
movement of said
press along said central longitudinal axis for a third distance, after removal
of said inner die
from said apparatus and while said outer die assembly in said active position,
causing metal
from said billet to be forced through said third bore around the rearward
portion of said
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mandrel to extrude the rearward section of said pipe having an inner diameter
which is equal
to the outer diameter of said rearward portion and an outer diameter which is
equal to the
inner diameter of said third bore.
3 . An apparatus as recited in claim 1, wherein said outer die assembly
comprises:
(a) a die holder having a fourth bore, said die holder having a rearward end
and
a forward end;
(b) an outer die located in said fourth bore at the rearward end of said outer
die
holder and containing said third bore; and
(c) a stop member located in said fourth bore at the forward end of said die
holder, said stop member having a cylindrical fifth bore having a diameter
which is larger than the diameter of said fourth bore.
4. An apparatus as recited in claim 1, wherein said mandrel has a rearward end
and said press comprises:
(a) a housing having a chamber for containing said mandrel and a forward end
having a opening to said chamber;
(b) a pressing ring located at the forward end of said housing at said forward
opening, said pressing ring including said forward pressing surface and a
cylindrical bore having an inner diameter which is substantially equal to the
outer diameter of the rearward portion of said mandrel; and
(c) a driver operatively connected to the rearward end of said mandrel for
moving
said mandrel along said central longitudinal axis between a rearward
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withdrawn position in which said rearward portion is within said chamber and
a forward extended position in which the rearward portion of said mandrel in
within the bore of said pressing ring and the remainder of said mandrel is
forward of said pressing ring.
5. An apparatus as, recited in claim 1, wherein said apparatus further
comprises
an actuator for moving said one of said outer die assembly and said container
along said
central longitudinal axis relative to the other of said outer die assembly and
said container.
6. An apparatus as recited in claim 5, wherein said actuator is a fluid
actuator
comprising:
(a) a cylinder fixed to said machine frame; and
(b) a piston slidable within said cylinder and having a rearward end extending
rearwardly of said cylinder and operatively connected to said container.
7. An apparatus as recited in claim 6, wherein there is a first one of said
fluid
actuator on one side of said central longitudinal axis and a second one of
said fluid actuator
at an opposite side of said central longitudinal axis and said container is
fixed to
the pistons of said first and second fluid actuators.
8. An apparatus as recited in claim 1, wherein said outer die assembly
comprises:
(a) a carrier having a central bore coaxial with said central longitudinal
axis, said
central bore having a forward opening and a rearward opening;
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(b) a die holder within said central bore at the forward opening of said
central
bore, said die holder having a cylindrical fourth bore, a rearward end and a
forward end; and
(c) an outer die located in said fourth bore at the rearward end of said outer
die
assembly and containing said third bore; and a stop member located in said
fourth bore at the forward end of said holder, said stop member having a
cylindrical fifth bore having a diameter which is larger than the diameter of
said fourth bore.
9. An apparatus as recited in claim 8, wherein said outer die assembly further
comprises a retaining ring in said central bore and surrounding said die
holder.
10. An apparatus as recited in claim 9, wherein said outer die assembly
further
comprises a retaining plate within said central bore and forward of said die
holder, said
retaining plate having a cylindrical bore which is coaxial with said central
longitudinal axis
and having a diameter which is larger than the diameter of said fifth bore and
smaller than
the diameter of said fourth bore.
11. An apparatus as recited in claim 10, wherein said outer die assembly
further
comprises a guide tube fixed to said retaining plate and extending forwardly
through the
forward opening of said central bore, said guide tube having an inner diameter
is at least as
large as the inner diameter of the bore of said retaining plate.
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12. An apparatus as recited in claim 1, wherein said machine frame has a
chamber
which has a rear opening and a front opening, said outer die assembly being
located within
said chamber for longitudinal movement along said central longitudinal axis,
said apparatus
further comprising a releasable stop mechanism for releasably maintaining said
outer die
assembly within said chamber in functional contact with said inner die.
13. An apparatus as recited in claim 12, wherein said machine frame has a
transverse bore extending transversely of said central longitudinal axis and
intersecting said
chamber, said releasable stop mechanism comprising a gate slidably mounted
within said
transverse bore between an active position in which at least a portion of said
gate is within
said chamber and an inactive position in which said gate is outside of said
chamber.
14. An apparatus as recited in claim 13, wherein said releasable stop
mechanism
further comprises an actuator for selectively moving said gate to said active
and inactive
positions.
15. An apparatus as recited in claim 14, wherein said actuator is a fluid
actuator.
16. An apparatus as recited in claim 1, wherein said apparatus further
comprises
a guide table forward of said outer die assembly for supporting and guiding
said pipe as said
pipe is extruded.
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17. An apparatus as recited in claim 16, wherein said guide table has upwardly
extending rollers for supporting said extruded pipe.
18. An apparatus as recited in claim 17, wherein said apparatus further
comprises
a guide tube extending from said outer die assembly to said guide table for
guiding said
extruded pipe from said outer die assembly to said guide table.
19. A mandrel for use in a metal extruding machine for extruding a metal pipe
having a uniform inner diameter of a first dimension, a forward end section, a
rearward end
section, and a middle section between said forward and rearward end sections,
said middle
section having an outer diameter of a second dimension and each of said
rearward and
forward end sections having an outer diameter of which is greater than said
second
dimension, said mandrel comprising:
(a) a cylindrical rearward portion having an outer diameter equal to said
first
dimension;
(b) a cylindrical middle portion having an outer diameter substantially less
than
the outer diameter of said rearward portion; and
(c) a forward portion which has a frusto-conical outer surface extending
forwardly
from said middle portion from an outer diameter equal to the outer diameter
of said middle portion to an outer diameter equal to the outer diameter of
said
rearward portion.
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20. A method of extruding a cylindrical metal pipe having a constant inner
diameter, said pipe having a forward end section, a rearward end section and a
middle section
having an outer diameter which is substantially smaller than the outer
diameter of each of said
forward and rearward sections, said method comprising:
(a) positioning a cylindrical metal billet having a cylindrical longitudinal
bore
within a cylindrical first bore of a container by inserting said billet
through a
rear opening to said first bore, said first bore having a central longitudinal
axis, said container having a front opening to said first bore and containing
an
inner die within said first bore adjacent said front opening and an outer die
outside of said container adjacent said front opening, said inner die having a
cylindrical second bore which has a smaller diameter than the diameter of said
first bore, said .outer die having a third bore which has a diameter which is
less than the diameter of said first bore and greater than the diameter of
said
second bore, each of said inner and outer dies selectively being movable along
said central longitudinal axis, said inner die comprising two separable half
portions;
(b) positioning a press along said central longitudinal axis, said press
having a
circular forward pressing surface facing said container and a mandrel
extending forwardly from said pressing surface toward said container, said
pressing surface and said mandrel being coaxial with said first bore, said
pressing surface having substantially the same outer diameter as the inner
diameter of said first bore with sufficient clearance to enable said pressing
surface to move longitudinally within said first bore, said mandrel having a
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cylindrical rearward portion which has a smaller diameter than said second
bore, a cylindrical middle portion which has a smaller diameter than said
rearward portion, and a frusto conical forward portion which extends
forwardly from the diameter of said middle portion from a diameter equal to
said middle portion to a diameter equal to the diameter of said rearward
portion;
(c) moving said press forwardly along said central longitudinal axis so that
said
mandrel extends through the bore of said billet and said middle portion lies
within said second bore to form a first ring-shaped opening and the juncture
of said middle portion and said rearward portion is spaced rearward of said
inner die when said forward pressing surface first engages said billet to push
said billet against said inner die;
(d) moving said press forwardly a first distance along said central
longitudinal axis
to a point that the juncture of said middle portion and said rearward portion
is at the rearward end of said second bore for forcing metal from said billet
through said first ring-shaped opening to extrude a preliminary forward end
section of pipe having an outer diameter which is equal to the inner diameter
of said second bore and an inner diameter which is equal to the outer diameter
of said middle portion;
(e) moving said press forwardly along said central longitudinal axis a second
distance with said rearward portion within said second bore to form a second
ring-shaped opening for forcing metal from said billet through said second
ring-shaped opening to extrude the middle section of said pipe having an outer
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diameter which is equal to the inner diameter of said second bore and an inner
diameter which is equal to the diameter of said rearward portion and causing
the preliminary forward end section of pipe to pass over the forward portion
of said mandrel during forward movement of said press for said second
distance so that the preliminary forward end section of said pipe is expanded
transversely of said central longitudinal axis to an inner diameter which is
equal to the inner diameter of the middle section of said pipe and an outer
diameter which is greater than the outer diameter of the middle section of
said
pipe;
(f) moving one of said outer die and said container along said central
longitudinal
axis so that said outer die is spaced from said stationary container a
distance
at least equal to the longitudinal length of said inner die;
(g) removing said inner die from said first bore through said front opening so
that
said inner die is forward of said container;
(h) removing the half portions of said inner die from said pipe and mandrel;
(i) moving one of said outer die and said container rearwardly along said
central
longitudinal axis so that said outer die is in engagement with said container
and said rearward is within said third circular bore to form a third ring-
shaped
opening;
(j) moving said press forwardly along said central longitudinal axis for a
third
distance for forcing metal from said billet through said third ring-shaped
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opening to extrude the rearward section of said pipe having an inner diameter
which is equal to the outer diameter of said rearward portion and an outer
diameter which is equal to the inner diameter of said third bore; and
(k) removing said extruded pipe from said mandrel.
21. A method of extruding a metal pipe as recited in claim 20, wherein said
extruded pipe is removed from said mandrel by moving said mandrel rearwardly
along said
central longitudinal axis until said mandrel is rearward of said extruded
pipe.
22. A method of extruding a metal pipe as recited in claim 20, wherein said
container is moved rearwardly along said central longitudinal axis relative to
said outer die
and said mandrel at step (f) of claim 20 for forcing said inner die out of
said first bore.
23. A method of extruding a metal pipe as recited in claim 20, wherein an
unextruded portion of said billet remains within said first bore after the
forward movement
of said mandrel for said third distance and said method comprises the
following additional
steps:
(a) moving said mandrel rearwardly along said central longitudinal axis until
said
mandrel is rearward of said extruded pipe;
(b) moving one of said outer die and said container forwardly along said
central
longitudinal axis, so that said outer die is spaced from said container; and
(c) removing the unextruded portion of said billet from the rearward end
section
of said extruded pipe.
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24. A method of extruding a metal pipe as recited in claim 23, wherein said
container is moved rearwardly along said central longitudinal axis relative to
said outer die
and said mandrel at step (b) of claim 23 for forcing the unextruded portion of
said billet from
said first bore.
25. A method of extruding a cylindrical metal pipe having a uniform inner
diameter of a first dimension, a forward end section, a rearward end section,
and a middle
section between said forward and rearward end sections, said middle section
having an outer
diameter of a second dimension and each of said rearward and forward end
sections having
an outer diameter which is greater than said second dimension, said method
comprising the
following steps:
(a) pressing a cylindrical metal billet within a cylindrical bore of a
container
through a first ring shaped opening having an inner diameter which is less
than
said first dimension and an outer diameter which is equal to said second
dimension to extrude a preliminary forward end section of said pipe having an
inner diameter which is less than said first dimension;
(b) pressing said metal billet within said bore through a second ring shaped
opening having an inner diameter which is equal to said first dimension and
an outer diameter which is equal to said second dimension to extrude the
middle section of said pipe;
(c) moving said preliminary forward end section of pipe over a mandrel which
has
a frusto-conical outer surface shaped for expanding the preliminary forward
end section of said pipe to form the forward end section of said pipe having
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an inner diameter equal to said first dimension and an outer diameter which
is greater than said second dimension; and
(d) pressing said metal billet within said bore through a third ring shaped
opening
having an inner diameter which is equal to said first dimension and an outer
diameter which is greater than said third dimension to extrude the rearward
end section of said pipe.
26. An apparatus for extruding a metal pipe having a forward end section, a
rearward end section and a middle section having an outer diameter which is
substantially
smaller than the outer diameter of each of said forward and rearward sections,
said forward
end section having an inner diameter which is smaller than the inner diameter
of each of said
rearward end section and said middle section, said apparatus comprising:
(a) a machine frame;
(b) a container supported on the machine frame, said container having a
central
longitudinal axis and a longitudinal cylindrical first bore coaxial with said
central longitudinal axis for receiving a cylindrical metal billet having a
longitudinal cylindrical bore, said container having a front opening to said
first
bore and a rear opening to said first bore;
(c) a cylindrical inner die having a cylindrical second bore coaxial with said
first
bore, said inner die having an outer diameter equal to the diameter of said
first
bore, said second bore having a diameter which is smaller than the diameter
of said first bore, said inner die being divided longitudinally into two
substantially equal half portions, said inner die being movable through said
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front opening along said central longitudinal axis between an inner position
within said first bore adjacent said front opening to an outer position
outside
of said first bore;
(d) an outer die assembly located forward of said container and having a
longitudinal cylindrical third bore which is coaxial with said first and
second
bores and which has a larger diameter than said second bore, one of said outer
die assembly and said container being movable along said central longitudinal
axis between are active position wherein said container and said outer die
assembly abut at said front opening and an inactive position wherein said
outer
die assembly and said container are spaced sufficiently to enable said inner
die
to be moved to acid outer position for removal from said apparatus;
(e) a press located rearward of said container and movable along said central
longitudinal axis toward and away from said container, said press having a
circular forward pressing surface facing the rear opening of said container
and
a mandrel extending forwardly from said pressing surface toward said rear
opening, said pressing surface and said mandrel being coaxial with said first
bore, said pressing surface having substantially the same outer diameter as
the
inner diameter of said first bore with sufficient clearance to enable said
pressing surface to move longitudinally within said first bore, said mandrel
having a cylindrical rearward portion which has a smaller outer diameter than
the inner diameter of said second bore, a cylindrical middle portion which has
a smaller outer diameter than the outer diameter of said rearward portion, and
a frusto-conical forward portion which extends forwardly from said middle
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portion from an outer diameter equal to the outer diameter of said middle
portion to an outer diameter larger than the outer diameter of said middle
portion and smaller than the outer diameter of said rearward portion; and
(f) an actuator for moving one of said outer die assembly and said container
along said longitudinal axis relative to the other of said outer die assembly
and
said container.
27. A mandrel for use in a metal extruding machine for extruding a metal pipe
having a uniform inner diameter of a first dimension, a forward end section, a
rearward end
section, and a middle section between said forward and rearward end sections,
said middle
section having an inner diameter of a first dimension and an outer diameter of
a second
dimension, each of said rearward and forward end sections having an outer
diameter which
is greater than said second dimension, said forward section having an inner
diameter which
is less than said first dimension, said mandrel comprising:
(a) a cylindrical rearward portion having an outer diameter equal to said
first
dimension;
(b) a cylindrical middle portion having an outer diameter substantially less
than
the outer diameter of said rearward portion; and
(c) a forward portion which has a frusto-conical outer surface extending
forwardly
from said middle portion from an outer diameter equal to the outer diameter
of said middle portion to an outer diameter which is less than said first
dimension and greater than the outer diameter of said middle portion.
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28. A method of extruding a cylindrical metal pipe having a forward end
section,
a rearward end section and a middle section having an outer diameter which is
substantially
smaller than the outer diameter of each of said forward and rearward sections,
said forward
end section having an inner diameter which is smaller than the inner diameter
of each of said
rearward end section and said middle section, said method comprising:
(a) positioning a cylindrical metal billet having a cylindrical longitudinal
bore
within a cylindrical first bore of a container by inserting said billet
through a
rear opening to said first bore, said first bore having a central longitudinal
axis, said container having a front opening to said first bore and containing
an
inner die within said first bore adjacent said front opening and an outer die
outside of said container adjacent said front opening, said inner die having a
cylindrical second bore which has a smaller diameter than the diameter of said
first bore, said outer die having a third bore which has a diameter which is
less than the diameter of said first bore and greater than the diameter of
said
second bore, each of said inner and outer dies selectively being movable along
said central longitudinal axis, said inner die comprising two separable half
portions;
(b) positioning a press along said central longitudinal axis, said press
having a
circular forward pressing surface facing said container and a mandrel
extending forwardly from said pressing surface toward said container, said
pressing surface and said mandrel being coaxial with said first bore, said
pressing surface having substantially the same outer diameter as the inner
diameter of said first bore with sufficient clearance to enable said pressing
-28-

surface to move longitudinally within said first bore, said mandrel having a
cylindrical rearward portion which has a smaller outer diameter than the inner
diameter of said second bore, a cylindrical middle portion which has a smaller
diameter than said rearward portion, and a frusto conical forward portion
which extends forwardly from said middle portion from an outer diameter
equal to the outer diameter of said middle portion to a diameter which is
larger
than the outer diameter of said middle portion and smaller than the diameter
of said rearward portion;
(c) moving said press forwardly along said central longitudinal axis so that
said
mandrel extends through the bore of said billet and said middle portion lies
within said second bare to form a first ring-shaped opening and the juncture
of said middle portion and said rearward portion is spaced rearward of said
inner die when said forward pressing surface first engages said billet to push
said billet against said inner die;
(d) moving said press forwardly a first distance along said central
longitudinal axis
to a point that the juncture of said middle portion and said rearward portion
is at the rearward end of said second bore for forcing metal from said billet
through said first ring-shaped opening to extrude a preliminary forward end
section of pipe having an outer diameter which is equal to the inner diameter
of said second bore and an inner diameter which is equal to the outer diameter
of said middle portion;
(e) moving said press forwardly along said central longitudinal axis a second
distance with said rearward portion within said second bore to form a second
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ring-shaped opening for forcing metal from said billet through said second
ring-shaped opening to extrude the middle section of said pipe having an outer
diameter which its equal to the inner diameter of said second bore and an
inner
diameter which is equal to the diameter of said rearward portion and causing
the preliminary forward end section of pipe to pass over the forward portion
of said mandrel during forward movement of said press for said second
distance so that the preliminary forward end section of said pipe is expanded
transversely of said central longitudinal axis to an inner diameter which is
less
than the inner diameter of the middle section of said pipe and an outer
diameter which its greater than the outer diameter of the middle section of
said
pipe;
(f) moving one of said outer die and said container along said central
longitudinal
axis so that said outer die is spaced from said stationary container a
distance
at least equal to the longitudinal length of said inner die;
(g) removing said inner die from said first bore through said front opening so
that
said inner die is forward of said container;
(h) removing the half portions of said inner die from said pipe and mandrel;
(i) moving one of said outer die and said container rearwardly along said
central
longitudinal axis so that said outer die is in engagement with said container
and said rearward is within said third circular bore to form a third ring-
shaped
opening;
(j) moving said press forwardly along said central longitudinal axis for a
third
distance for forcing metal from said billet through said third ring-shaped
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opening to extrude the rearward section of said pipe having an inner diameter
which is equal to the outer diameter of said rearward portion and an outer
diameter which is equal to the inner diameter of said third bore; and
(k) removing said extruded pipe from said mandrel.
29. A method of extruding a metal pipe as recited in claim 28, wherein said
extruded pipe is removed from said mandrel by moving said mandrel rearwardly
along said
central longitudinal axis until paid mandrel is rearward of said extruded
pipe.
30. A method of extruding a metal pipe as recited in claim 28, wherein said
container is moved rearwardly along said central longitudinal axis relative to
said outer die
and said mandrel at step (f) of claim 20 for forcing said inner die out of
said first bore.
31. A method of extruding a metal pipe as recited in claim 28, wherein an
unextruded portion of said billet remains within said first bore after the
forward movement
of said mandrel for said third distance and said method comprises the
following additional
steps:
(a) moving said mandrel rearwardly along said central longitudinal axis until
said
mandrel is rearward of said extruded pipe;
(b) moving one of paid outer die and said container forwardly along said
central
longitudinal axis so that said outer die is spaced from said container; and
(c) removing the unextruded portion of said billet from the rearward end
section
of said extruded pipe.
-31-

32. A method of extruding a metal pipe as recited in claim 31, wherein said
container is moved rearwardly along said central longitudinal axis relative to
said outer die
and said mandrel at step (b) of claim 23 for forcing the unextruded portion of
said billet from
said first bore.
33. A method of extruding a cylindrical metal pipe having a forward end
section,
a rearward end section, and a middle section between said forward and rearward
end sections,
said middle section having an inner diameter of a first dimension and an outer
diameter of
a second dimension, said rearward end section having an inner diameter of said
first
dimension and an outer diameter greater than said second dimension, said
forward end section
having an outer diameter which is greater than said second dimension and an
inner diameter
of a third dimension which is less than said first dimension, said method
comprising the
following steps:
(a) pressing a cylindrical metal billet within a cylindrical bore of a
container
through a first ruig shaped opening having an inner diameter which is less
than
said third dimension and an outer diameter which is equal to said second
dimension to extrude a preliminary forward end section of said pipe having an
inner diameter which is less than said third dimension;
(b) pressing said metal billet within said bore through a second ring shaped
opening having an inner diameter which is equal to said first dimension and
an outer diameter which is equal to said second dimension to extrude the
middle section of said pipe;
-32-

(c) moving said preliminary forward end section of pipe over a mandrel which
has
a frusto-conical outer surface shaped for expanding the preliminary forward
end section of said pipe to form the forward end section of said pipe having
an inner diameter equal to said third dimension and an outer diameter which
is greater than said second dimension; and
(d) pressing said metal billet within said bore through a third ring shaped
opening
having an inner diameter which is greater than said first dimension and an
outer diameter which is greater than said second dimension to extrude the
rearward end section of said pipe.
-33-

Description

CA 02346705 2001-04-06
WO 00/21696 P(:T/US99/23618
APPARATUS AND METHOD FOR FORMING A PIPE WITH INCREASED WALL-THICKNESS AT ITS
ENDS
TECHNICAL FIELD
The present invention is directed to pipe manufacture, especially forming a
fluid
conveying pipe known in thE: trade as a "double ended upset pipe". Such a pipe
has a
forward, or "pin" end section, an elongated middle section and a rearward, or
"box" end
section. The inner diameters of all three sections of the pipe are the same.
The outer
diameters of the forward and rearward end sections of the pipe are
substantially greater than
the outer diameter of the middle section of pipe. Therefore, the thickness of
the middle
section of the pipe is substantially thinner than either of the forward and
rearward end
sections of the pipe.
BACKGROUND OF THE INVENTION
The present invention is directed to an apparatus for forming a fluid
conveying pipe
known in the trade as a "doubl.e ended upset pipe". Such a pipe has a forward,
or "pin" end
section, an elongated middle section and a rearward, or "box" end section. The
inner
diameters of all three sections of the pipe are the same. The outer diameters
of the forward
and rearward end sections of tlhe pipe are substantially greater than the
outer diameter of the
middle section of pipe. Therefore, the thickness of the middle section of the
pipe is
substantially thinner than either of the forward and rearward end sections of
the pipe. The
extra thickness of the forward and rearward end section of the pipe is
machined and/or
threaded to enable the forward, or "pin" end of a first pipe to be coupled to
the rearward or
"box" end of a second pipe.
In the past, metallic double ended upset pipes have been formed by extruding
the
middle and end sections of the pipe separately and welding the forward and
rearward end
sections to opposite ends of thE: middle section. Since the welded areas
represent potentially
2;5 weak areas of the pipe, each section of the pipe is made thicker than that
which would
normally be needed. This procedure is time consuming and expensive. The extra
thickness
which requires extra material also adds a material cost to the pipe. The added
weight of the
pipe adds still further costs in shipping and handling.

CA 02346705 2001-04-06
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Many metal extrusion devices and methods have been developed for extruding a
pipe
from a billet with the use of a~ press, a die, and a mandrel. However, there
is no known
apparatus or system for extruding an integral pipe having a uniform inside
diameter in which
the opposite end sections of the pipe have an outside diameter greater than
the outside
'.i diameter of the middle section ~of the pipe. These and other difficulties
experienced with the
prior art pipe extruding devices or methods have been obviated by the present
invention.
It is, therefore, a principal object of the invention to provide an apparatus
for
extruding a pipe from a metal billet for producing an integrally formed pipe
having a constant
or uniform inside diameter and a middle section which has a smaller outside
diameter than
1() the outside diameter of each of the opposite end section of the pipe.
A further object of the invention is the provision of an apparatus for
extruding a pipe
from a metal billet as described above in a single continuous extrusion
operation.
Another object of the present invention is the provision of a method of
extruding a
pipe from a metal billet in which the pipe has uniform inside diameter and a
middle section
15~ having a smaller outside diameter than the outside diameter of the
opposite end sections of
the pipe.
A still further object of the invention is the provision of a method of
extruding from
a metal billet a pipe as defined above in a single continuous process.
Still another object of the invention is the provision of having an outside
non-uniform
2C~ configuration mandrel for use i:n a metal extrusion machine for extruding
from a metal billet
a pipe having a uniform inside diameter and a middle section which has a
smaller outside
diameter than the outside diameter of the opposite end sections of the pipe.
Another object of the invention is the provision of an apparatus for extruding
a pipe
from a metal billet wherein the middle section of the pipe has a smaller
outside diameter than
25 the outside diameter of each of the opposite end sections of the pipe and
one end section of
the pipe has a smaller inner diameter that the inner diameter of the middle
section and
opposite end section of the pipe:.
With these and other objects in view, as will be apparent to those skilled in
the art,
the invention resides in the combination of parts set forth in the
specification and covered by
30 the claims appended hereto.
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BRIEF SUMMARY OF THE INVENTION
Apparatus for and method of extruding a metal pipe having a substantially
uniform
inner diameter. The forward and rearward end sections of the pipe are thicker
than the middle
section of the pipe. A heated metal billet having a cylindrical longitudinal
bore is inserted
into the rear opening of a cylindrical bore of a stationary container. A two-
part removable
inner die is located within the lbore of the container adjacent the forward
end of the container
and an outer die is located outside of the container adjacent the front end of
the container.
The inner die has a relatively small diameter cylindrical bore. The outer die
has a relatively
large diameter cylindrical bore;. The billet is moved along a central
longitudinal axis within
the bore of the container by a press which includes a circular forward
pressing surface and
a mandrel extending forwardly from the pressing surface toward the billet. The
mandrel has
a cylindrical relatively large diameter rearward portion, a cylindrical
relatively small diameter
middle portion and a frusto cc>nical forward portion which tapers outwardly in
the forward
direction from the diameter of the middle portion to the diameter of the
forward portion.
1.5 Metal from the billet is forcedl through the bore of the inner die around
the small diameter
portion of the mandrel by mowing the press forwardly for a first distance for
extruding a
preliminary forward end section of pipe. The press is moved forwardly for a
second distance
for forcing metal from the billet through the bore of the inner die around the
large diameter
rearward portion of the mandrel for extruding the middle section of pipe and
causing the
2~D preliminary forward end section of pipe to pass over the tapered forward
portion of the
mandrel. This causes the preliminary forward end section of pipe to be
expanded transversely
of its central longitudinal axis to an inner diameter which is equal to the
inner diameter of
the middle section and a wall thickness which is greater than the wall
thickness of the middle
section of pipe. The inner die is removed from the container and the press is
moved
2:i forwardly for a third distance for forcing metal from the billet through
the bore of the outer
die around the rearward portion of the mandrel to extrude the rearward end
section of pipe
having an inner diameter which is equal to the inner diameter of the middle
section of pipe
and a wall thickness which is ;greater than the wall thickness of the middle
section of pipe.

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BRIEF DESCRIPTION OF THE DRAWINGS
The character of the invention, however, may be best understood by reference
to one
of its structural forms, as illustrated by the accompanied drawings, in which:
FIG. 1 is a longitudinal cross-sectional view of the primary functional
components of
the extruding apparatus of the present invention for forming a double ended
upset pipe;
FIG. 2 is a side elevational view of the mandrel portion of the apparatus;
FIG. 3 is an end view of a two-part die which also forms a portion of the
apparatus;
FIGS. ~-12 are operational views illustrating the formation of the forward and
middle
sections of the pipe;
FIGS. 13-18 are operational views showing the formation of the rearward
section of
the pipe;
FIGS. 19a, 19b, I9c, and 19d are vertical cross-sectional views which may be
joined
together along the common lines A-A, B-B, and C-C and showing the overall
extruding
apparatus of the present invention; and
1:5 FIG. 20 is a view similar to FIG. 10 and showing a modified mandrel.
DETAILET) DESCRIPTION OF THE INVENTION
Referring first to FIGS.. 19a, 19b, 19c, and 19d, the pipe extruding apparatus
of the
present invention is generally indicated by the reference 10. Apparatus 10
comprises a
rearward machine base 72, and a forward machine base 72 connected to the
rearward machine
base by four connecting rods 74. A press, generally indicated by the reference
numeral 13,
is mounted on the pipe extruding apparatus 10 between the machine bases 70 and
72 for
longitudinal movement along central longitudinal axis 18.
Press 13 includes a crosshead 78 located between the machine base 70 and 72. A
piston 75 is connected to the rearward side of the crosshead 78 through a
horizontal connector
2-'i 79. Piston 75 is slidably mounted within a single acting hydraulic
cylinder 77 which is fixed
to the rearward machine base 72. Cylinder 77 is connected to a high pressure
hydraulic
source, not shown, through hydraulic line 73. Crosshead 78 is supported on a
pair of
longitudinal ways 81 and guidled on the connecting rails 74 for longitudinal
forward and
rearward movement along the longitudinal axis 18. Crosshead 78 has a
horizontal bore 65
3(1 which is coaxial with longitudinal axis 18. A double acting hydraulic
cylinder 81 is fixed to
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CA 02346705 2001-04-06
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the hydraulic cylinder 77 through a structural support 82. A piston, generally
indicated by
the reference numeral 85, includes a piston head 89 slidably mounted within
the cylinder 81
and a piston rod 93 extending from the cylinder 81 and fixed to the upper end
of the
crosshead 78. Cylinder 81 is connected to a high pressure hydraulic source,
not shown,
through hydraulic lines 76. Actuation of cylinder 77 causes the piston 75 and
the crosshead
78 to move forwardly toward the forward machine base 70. The relatively large
size of the
cylinder 77 provides the large f=orces required to force a billet through the
die structure to be
described at the forward end of the extruder. The crosshead 78 and the piston
75 are moved
rearwardly to their starting positions by actuating the cylinder 81 so that
the head 89 is moved
rearwardly within the cylinder $1. Press 13 also includes a cylindrical
housing or stem 36
that is fixed to the forward side of crosshead 78 and extends forwardly along
the longitudinal
axis 18. A double acting hydraulic cylinder 69 is fixed to the rearward side
of crosshead 78
and connected to the high pressure hydraulic source through hydraulic lines
68.
Stem 36 has a chamber 40 and a forward end 47 which contains a forward opening
49 to the chamber 40. A pressing ring 38 is located at the forward opening 49
of the housing
36 and contains a cylindrical bore 42 and a circular forward pressing surface
39. A mandrel
44 is located within the chamber 40 and has a rearward end 45 configured to be
coupled to
the forward end of a driving rod 46. A bushing 59 is fastened to the forward
end of the
driving rod 46 with a clearance fit within the stem 36. This helps to support
the driving rod
20~ 46 and maintains the mandrel 44 on center. The rearward end of the driving
rod 46 is
coupled to a piston 71 which is slidably mounted within the cylinder 69. The
cylinder 69
enables the mandrel 44 to be selectively moved forwardly and rearwardly along
the
longitudinal axis 18 relative to the stem 36. The mandrel 44 is coaxial about
the central
longitudinal axis 18. The mandrel 44 has a cylindrical rearward portion 48, a
reduced
diameter cylindrical middle portion 50, and a frusto conical forward portion
52 which tapers
outwardly from the reduced diameter middle portion 50 to the forward end of
the mandrel.
The extreme forward end of the mandrel 44 has the same diameter as that of the
rearward
portion 48. The mandrel 44 expends freely through the bore 42 of the pressing
ring 38. The
pressing ring 38 is not attached to the stem 36 and is supported on the
mandrel 44.
-5-

CA 02346705 2001-04-06
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A housing or container 12 is supported on the forward machine base 70. The
housing
12 is fixed to a pair of oppositely extruding connecting arms 80. Connecting
arms 80 are
fixed to the rearwardly extending ends 85 of a pair of pistons, generally
indicated by the
reference numeral 84. The forward ends of pistons 84 are slidably mounted
within double
acting hydraulic cylinders 88 which are connected to the high pressure
hydraulic source
through hydraulic lines 90. The hydraulic cylinders 88 are fixed to the
forward machine base
70. The housing 12 contains a cylindrical tube or liner 14 having a circular
bore 16 which
is coaxial with the longitudinal axis 18. The bore 16 has a circular rear
opening 15 and a
circular front opening 17. Referring also to FIGS. 1 and 3, a cylindrical
inner die 20 is
ll0 located within the bore 16 adljacent the front opening 17 of the bore. The
inner die 20 is
divided transversely along the: line 21 to form two separable halves 20a and
20b. An outer
die assembly, generally indicated by the reference numeral 23, is located
outside of the front
opening 17 of the bore 16. ~Clhe outer die assembly 23 includes a die holder
24 which has
a bore 37, a rearward end 41 " and a forward end 43 . An outer die 26 is
located within the
1.5 bore 37 at the rearward end 41 of the die holder 24. A back plate 30 is
located at the
forward end 43 of the die holder 24. The outer die 26 has a circular bore 28.
The back
plate 30 has a circular bore .32. The diameter of the bore 32 is slightly
larger than the
diameter of the bore 28. Thc: bore 22 of the inner die 20 has a smaller
diameter than the
diameter of the bore 28.
2;0 The pipe which is to be: formed by the extruding apparatus 10 of the
present invention
is formed from a cylindrical billet 54 that has a cylindrical longitudinal
bore 56. The size
of the billet 54 is such that there is a specified amount of clearance between
the outer surface
of the billet relative to the inner surface of the liner 14 which defines the
bore 16. The
diameter of the bore 56 of billet 54 has a specified clearance relative to the
outer diameter
25 of the portions 48 and 52 of the mandrel. The stem 36 of the press 13 moves
along the axis
18 and applies all of the forward force of the press 13 to the billet 54.
The outer die assembly 23 is located within a retaining ring 92 which is
located at the
rearward end of a removable housing or outer die carrier 98. Die carrier 98 is
located within
a horizontal chamber 100 in the forward machine base 70. Chamber 100 has a
rear opening
3~0 103 and a forward opening 99. Carrier 98 has a central horizontal bore 97
that has a forward
opening 86 and a rearward opening 87. The rearward portion of the bore 97 has
a
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CA 02346705 2001-04-06
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counterbore 96 which contains the retaining ring 92 and outer die assembly 23.
A retaining
plate 94 is located at the forward end of the counterbore portion of the bore
97. Retaining
plate 94 has a bore 91 which has a larger diameter than the bore 32 of the
back plate 30.
The outer die carrier 9'8 is maintained at the rearward end of the chamber 100
by a
releasable stop mechanism, generally indicated by the reference numeral 102.
Stop
mechanism 102 includes a pair of oppositely facing gates 104 slidably mounted
within
transverse bores 101 which intersect the chamber 100. Each gate 104 is
connected to one end
of a piston 108. The opposite end of each piston 108 is slidably mounted
within a hydraulic
cylinder 110. Each hydraulic cylinder 110 is fixed to the forward machine base
70. the
1~0 hydraulic cylinders 110 can be: controlled for selectively moving the
gates 104 between an
active position, as shown in FIG. 19d, in which the gates 104 are located
within the chamber
100 to an inactive position in v~rhich the gates 104 are outside of the
chamber 100. When the
gates 104 are in their active positions, they block any forward movement of
the outer die
carrier 98 and maintain the outer die assembly 23 against the forward end of
the container
1:5 12 and the inner die 20. Whc;n the gates 104 are in their inactive
positions, the outer die
carrier 98 can be removed from the chamber 100 through the front opening 99.
A guide tube 95 is fixed to the forward side of the retaining plate 94. Guide
tube 45
is coaxial with the longitudinal axis 18 and extends forwardly through the
front opening 99.
A table 112 is fixed to the guide tube 95 and extends below the tube 95. A
plurality of guide
20 rollers 114 are located on the supper surface of the table 112.
Having described the details of the pipe forming apparatus of the present
invention,
a double ended upset pipe blank is formed in accordance with the following
description.
Referring to FIG. l, the; mandrel 44 is shown retracted into the stem 36 to
enable the
billet 54 to be positioned between the mandrel 44 and the opening 15 of the
chamber 16.
2'i The billet 54 is then loaded into the bore 16 of the container 12. Once
the billet 54 has been
loaded into the bore 16, as shown in FIG. 4, the cylinder 69 is actuated to
force the driver
46 forwardly relative to the crosshead 78 and stem 36. The mandrel 44 is
thereby extended
forwardly by the driver 46, relative to the stem 36, so that the rearward
portion 48 of the
mandrel is at the forward end of the stem 36 and within the bore 42 of the
pressing ring 38.
3C1 At this point, the mandrel 44 is maintained in a fixed position relative
to the ring 38. The
cylinder 77 is actuated to move the press 13, comprising crosshead 78, stem
36, mandrel 44,
_7_

CA 02346705 2001-04-06
WO 00/21696 PCT/US99/2361$
and pressing ring 38, forwardl;y as a single unit. The press 13 is moved
forwardly, as shown
in FIG. 5, along the longitudinal axis 18 so that the mandrel 44 extends
through the bore 56
of the billet 54, through the bore 22 of the inner die 20, through the bore 28
of the outer die
26 and through the bore 32 of the back plate 30. The stem 36 also enters the
bore 16, as
:5 shown in FIG. 5. The pressing ring 38 is shown in FIG. 5 abutting the
rearward end of the
billet 54 just prior to applying a forward compressing force to the billet.
A preferred variation of this first step is to actuate cylinder 69 to push the
mandrel
44 through the bore 56 of the ibillet 54 while the billet is supported on a
moveable carriage.
The cylinder 77 is actuated to move the press 13 toward the container 12,
thereby carrying
the mandrel 44 and the billet :54 into the bore 16 of the container to the
position shown in
FIG. 5.
The billet is forced against the rearward end of the inner die 20 by
additional forward
movement of the press 13. A small forward movement of the press 13 squeezes
the billet
54 and forces metal from the billet to completely fill the space between the
inner surface of
1.'> the liner 14 and the billet. Medal at the forward end of the billet 54 is
also forced inwardly
toward the reduced diameter middle portion 48 of the mandrel 44 as shown in
FIG. 6 to form
an inward bulge or "upset" 60 of material. At this point, the forward force of
the stem 36
has squeezed the billet 54. The billet is thereby reduced slightly in length
and the
corresponding volume of the billet is diverted to the gap between the liner 14
and the billet
2(I 54 and to the gap between the mandrel and the billet to form the "upset"
60. The location
of the intersection between the reduced diameter middle portion 50 of the
mandrel and
rearward portion 48 of the mandrel, relative to the inner die 20, determines
the length of the
preliminary forward or "pin'" section 62 of the pipe, as shown in FIG. 7.
Continuous squeezing of the billet 54 by the forward movement of stem 36 for a
first
25~ distance forces metal from the billet through a first ring-shaped opening
or gap 51 between
the inner surface of the inner die 20 and the reduced diameter middle portion
50 of the
mandrel to form the cylindrical preliminary forward end section 62 of the
pipe, as shown in
FIG. 7. Preliminary forward end section 62 will eventually become the "pin" or
forward end
section of the pipe. The middles section 64 and the forward section 67 of the
pipe are formed
30~ by moving the press 13 forwardly for a second distance. At this point, the
cylindrical large
diameter rear portion 48 of thc~ mandrel reaches the rearward portion of the
inner die 20.
_g_

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When the rearward portion 48 ~of the mandrel enters the bore 22 of the inner
die 20, as shown
in FIG. 8, a second ring shaped opening 53 is formed between the inner surface
of the inner
die 20 and the rearward portion 50 of the mandrel. The inner diameter of the
second ring-
shaped opening 53 is greater than the inner diameter of the first opening 51.
This also means
:S that the second ring-shaped opening 53 is narrower than the first ring
shaped opening 51.
Metal from billet 54 is, therefore, forced through the opening or gap 53 by
the forward
pressure of the stem 36 as a tubular extrusion having a thinner wall
thickness. This begins
the formation of a cylindrical middle section 64 of the pipe. At the same
time, the
preliminary forward end section 62 of the pipe reaches the tapered forward
portion 52 of the
11) mandrel, as shown in FIG. 8, and begins to expand transversely of the axis
18. Since the
cross section of the billet 54 i<.; much larger than the cross section of the
finished pipe, the
extruded pipe is several times longer than the billet. The length of the
extruded pipe is
determined by the ratio of the .cross sectional area of the billet to the
cross sectional area of
the pipe (or extrusion ratio). For example, for an extrusion ratio of 12 to 1,
for every inch
1_'i that the press 13 advances, 12 inches of extruded pipe will be formed.
This elongation at the
point of extrusion causes the extruded pipe to slide over the outside diameter
of the mandrel
44, since the mandrel is maint~iined in a fixed relationship to the housing or
stem 36.
FIG. 9 shows further squeezing of the billet 54 and the lengthening of the
middle
section 64 of the pipe and continued flaring of the preliminary forward end
section 62 of the
2(1 pipe as it is forced over the tapered forward end portion 52 of the
mandrel 44.
FIGS. 10 and 11 show the completion of the expansion process for the forward
end
section of the pipe. As the forward end of the preliminary forward end section
62 of the pipe
passes the forward end of the tapered forward portion 52 of the mandrel, it
becomes
cylindrical, as shown in FIG. 10. Also, the inside diameter of the expanded
forward end
25~ section 62 is the same as the inside diameter of the middle section 64.
The preliminary
forward end section 62 of the pipe is shown fully expanded in FIG. 11, thereby
completing
the formation of the forward, or "pin", end section of the pipe and is
identified by the
reference numeral 67.
As the stem 36 continuf;s to advance forwardly, the length of the middle
section 64
30~ of the pipe gradually lengthens until the required length of pipe has been
extruded as shown
in FIG. 12. After the middle section 64 of the pipe has been formed, the
cylinder 77 is
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deactivated and the cylinders 8I and 85 are activated simultaneously to move
the stem 36 and
the container 12 rearwardly. The billet 54 and the partially extruded pipe
also move
rearwardly with the container 12, as shown in FIG. 13. This creates a small
gap between
the container 12 and the die holder 24 and eliminates the forward pressure on
the die carrier
98. The cylinders 110 are them actuated to remove gates 104 from the chamber
100 and the
removable die carrier 98 is moved forwardly to create a gap 57 between the die
holder 24
and the container 12, as shown in FIG. 14. Gap 57 is wider than the inner 20.
The cylinder
81 is deactivated and the cylinder 77 is again activated to move the stem 36
forwardly. This
forces the inner die forwardly out of the container 12 and into the space 57,
as shown in FIG.
15. When the inner die 20 clf:ars the front opening 17 of the bore 16, the two
halves of the
inner die 20 separate and fall aiway from the middle section 64 of the pipe,
as shown in FIG.
16. The housing 98 is moved rearwardly and the stem 36 and container 12 are
moved
forwardly to the rear opening 103 of the chamber 100 so that the die holder 24
abuts the
forward surface of the container 12, as shown in FIG. 17. The cylinders 110
are actuated
to return to the gates 104 to tile chamber 100 in front of the die carrier 98.
The remaining portion of the billet 54 is used to form the rearward or "box"
section
of the pipe.
The cylinder 77 is acW ated to move the press 13 and the stem 36 forwardly a
third
distance. The space between the rearward portion 48 of the mandrel and the
inner surface
2~0 of the bore 28 defines a third ring-shaped opening or gap 55. Forward
movement of the
press 13 for the third distance forces metal from the billet 54 through the
third ring-shaped
opening or gap 55. The bore 28 of the outer die 26 has a larger diameter than
the bore 22
of the inner die 20 so that the 'thickness of the ring-shaped opening or gap
55 is greater than
the thickness of the second ring-shaped opening or gap 53. Therefore, the
metal from the
2:5 billet 54 which is forced through the third opening 55 forms the
relatively thicker rearward
end section 66 of the pipe, as shown in FIG. 18. The outer diameter of the
rearward end
section 66 is substantially greater than the outer diameter of the middle
section 64 of the pipe.
At this point, the extrusion of the pipe is complete. A small unextruded
portion of the billet
54 remains after the full desired length of the pipe has been extruded. The
unextruded
30 portion is identified by the reference numeral 68 in FIG. 18. The
unextruded portion 68 can
be removed from the pipe at the extruder by actuating the cylinder 69 to move
the mandrel
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rearwardly out of the extruded pipe and by actuating the cylinder 88 to move
the container
12 rearwardly. The rearward movement of the container 12 pushes the unextruded
portion
68 of the billet out of bore 16~ where it can be sawed from the end of the
pipe. Preferably,
the extruded pipe, including t:he unextruded portion 68 is moved a short
distance rearward
to facilitate removal of the unextruded portion 68. The extruded pipe is
removed by
actuating the cylinders 110 to move the gates 104 to their inactive positions
out of the
chamber 100. The die housiing 98 is removed from the chamber 100 through the
front
opening 99. This enables the extruded pipe to be moved from the chamber 100
through the
front opening 99. The unextruded portion 68 can be removed from the rearward
end of the
extruded pipe by any desired means, i.e., shearing, sawing, grinding,
torching, laser cutting,
etc. The extruded pipe is then removed from the chamber 100. The extruded pipe
is a blank
pipe form for subsequent finishing. The ends of the pipe are threaded and
machined in a
conventional manner to form .a finished pipe.
Referring to F1G. 20, a modified mandrel, generally indicated by the reference
numeral 44', is shown within the container 12 at the expansion step of the
forward end
section of the pipe. The mandrel 44' has a cylindrical rearward portion 48', a
reduced
diameter cylindrical portion 50'' and a frusto conical portion 52' which
tapers outwardly from
the reduced diameter middle portion 50' to the forward end of the mandrel. The
mandrel 44'
is identical to the mandrel 44 with respect to the rearward and middle
portions of the
2iD mandrel. However, the mandrel 44' differs from the mandrel 44 with respect
to the frusto
conical forward portion of the mandrel. The outer diameter of the extreme
forward end of
the mandrel 44' is greater than the outer diameter of the middle portion 50'
and less than the
outer diameter of the rearward portion 48'. As the forward end of the
preliminary forward
end section 62 of the pipe passes the forward end of the tapered portion 52'
of the mandrel
2:5 44', section 62 becomes cylindrical, as shown in F1G. 20. However, the
inside diameter of
the expanded forward end section 62 is less than the inside diameter of the
middle section 64
of the pipe.
The invention having teen thus described, what is claimed as new and desired
to
secure by Letters Patent is:
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