Note: Descriptions are shown in the official language in which they were submitted.
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HYDROFORMING APPARATUS
FIELD OF THE INVENTION
[0001] This invention is related to a hydroforming apparatus for hydroforming
a
workpiece.
BACKGROUND OF THE INVENTION
[0002] Many parts such as the ones used in automotive structures are
manufactured using a hydroforming process. The hydroforming process requires
large
presses up to 5,000 tons to hold the hydroforming die close during the
hydroforming
process. These presses are large, expensive, require large amounts of energy
to
operate and require special and expensive installations, yet the work is done
using the
hydroforming pressure not the press forces. In an effort to reduce the
automotive
vehicle weight, high strength steel is being used, which means larger
hydroforming
presses are required.
[0003] Processes such as hydroforming process requires large presses to clamp
the die in place while forming is done by other means such as applying
internal
pressure to form the part.
[0004] As shown in Figs. 2a and 2b, the hydroforming technique according to
the
prior art includes providing a die 10 having a lower portion 12 and an upper
portion 14
which combine to define a die cavity 16. The upper portion 14 is moved
generally
downward into a closed position forming a die cavity 16 over a round tube 22.
Side
plugs 18 and 20 are then moved sideways to engage the tube 22, to seal both
ends of
tube 22, and a hydraulic pressure source is connected to the interior of tube
22 through
an opening 24 inside plugs 18 and 20, thereby expanding tube 22 until it
conforms to
the shape of the die cavity 16.
[0005] The force F required to keep the die 10 closed varies according to the
size
of the tube 22 and typically is in the magnitude of thousands of tons. In
order to supply
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the force F a large press is used to keep the die 10 closed. For example, the
press
typically provides a force F of 5,000 tons or more. With reference to Fig. 3,
the prior art
press is relatively large and expensive. The prior art press often is mounted
to a
subsurface structure, which is relatively expensive.
SUMMARY OF THE INVENTION
[0006] In its broad aspect, the invention provides a hydroforming apparatus
for
hydroforming a workpiece. The apparatus includes a die and an outer ring
subassembly. The die includes a lower die section mounted in a lower die
holder and
an upper die section mounted in an upper die holder. One of the upper and
lower die
holders is movable relative to the other between an open position, in which
the
workpiece is positionable between the upper and lower die holders, and a
closed
position, in which the lower and upper die sections combine to define a die
cavity
therebetween in which the workpiece is hydroformed. In addition, each of the
upper
and lower die holders has an outer surface respectively. The outer ring
subassembly
includes a ring and one or more first cam segments attached to an inner
surface of the
ring. The outer ring subassembly also includes one or more second cam segments
and
one or more tapered wedges positioned between the first and second cam
segments.
The second cam segment is movable between an open position, in which the
second
cam segment is positioned distal to the first cam segment, and a closed
position, in
which the second cam segment is disposed proximal to the first cam segment.
The
outer ring subassembly also includes one or more biasing means for biasing the
second
cam segment to the closed position. The tapered wedge is movable between an
extended position, in which the second cam segment is pushed by the tapered
wedge
to the open position, and a retracted position, in which the second cam
segment is
moved to the closed position by the biasing means. Also, the second cam
segment
includes a lower surface shaped to engage the outer surface of the upper and
lower die
holders. In addition, the outer ring subassembly is movable between a forward
position,
in which the lower surface of the second cam segment engages the outer surface
upon
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the tapered wedge moving to the extended position, and return position, in
which the
lower surface is disengaged from the outer surface of the upper and lower die
holders.
[0007] In another aspect, the outer surfaces of the upper and lower die
holders
cooperate to form a cylindrical shape when the upper and lower die holders are
combined.
[0008] In another of its aspects, the hydroforming apparatus additionally
includes
one or more hydraulic cylinders for moving the tapered wedge between the
retracted
position and the extended position.
[0009] In yet another aspect, the hydraulic cylinder exerts a first force
directed in
a first direction on the tapered wedge to move the tapered wedge to the
extended
position.
[0010] In another aspect, the tapered wedge includes a substantially planar
contact surface and the second cam segment includes a substantially planar
mating
surface. Upon movement of the tapered wedge to the extended position, the
contact
surface and the mating surface engage each other substantially on a contact
plane.
The contact plane defines an acute angle between the contact plane and the
first
direction so that, upon movement of the tapered wedge to the extended
position, a
second force is transmitted which is directed toward the outer surface, to
assist in
holding the upper and lower die holders together during hydroforming.
[0011] In yet another aspect, the outer ring subassembly is movable along
guide
rods between a forward position and a returned position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will become more fully understood from the
detailed
description and the accompanying drawings wherein:
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[0013] Fig. 1 is a sectional view of a hydroforming apparatus according to the
invention showing an outer ring over a die holder;
[0014] Fig. 2a is a sectional view of a hydroforming apparatus of the prior
art
showing a prior art hydroforming die in an open position, drawn at a larger
scale;
[0015] Fig. 2b is a sectional view of the prior art hydroforming apparatus of
Fig.
2a showing the hydroforming die thereof in a closed position;
[0016] Fig. 3 is a sectional view of the prior art hydroforming apparatus of
Figs.
2a and 2b showing the hydroforming die in a hydroforming press, drawn at a
smaller
scale;
[0017] Fig. 4a is a sectional view of the hydroforming apparatus according to
the
invention without the outer ring showing the hydroforming die in the open
position,
drawn at a larger scale;
[0018] Fig. 4b is another sectional view of the hydroforming apparatus of Fig.
4a;
[0019] Fig. 5a is a sectional view of the hydroforming apparatus according to
the
invention without the outer ring showing the hydroforming die in the closed
position;
[0020] Fig. 5b is another sectional view of the hydroforming apparatus of Fig.
5a;
[0021] Fig. 6a is a sectional view of an embodiment of the outer ring of the
invention with tapered wedges thereof each in a retracted position and lower
cam
segments each in an open position;
[0022] Fig. 6b is a sectional view showing an upper tapered wedge and cam
segment, drawn at a larger scale;
[0023] Fig. 6c is a sectional view of the tapered wedge, drawn at a larger
scale;
[0024] Fig. 6d is a sectional view of the lower cam segment, drawn at a
smaller
scale;
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[0025] Fig. 7a is a sectional view of the outer ring of Fig. 6a with tapered
wedges
thereof each in an extended position and lower cam segments each in a closed
position;
[0026] Fig. 7b is a sectional view showing an upper tapered wedge and cam
segment, drawn at a larger scale;
[0027] Fig. 8a is a cross sectional view of the outer ring of Fig. 6a, drawn
at a
smaller scale;
[0028] Fig. 8b is a cross-sectional view of a portion of the outer ring of
Fig. 8a,
drawn at a larger scale;
[0029] Fig. 9a is a sectional view of the outer ring of Fig. 6a showing guide
rods
and bushings;
[0030] Fig. 9b is a sectional view of the outer ring of Fig. 6a, drawn at a
smaller
scale;
[0031] Fig. 10 is a sectional view of the die and die holder and outer ring of
Fig.
6a with the die closed and the outer ring in the returned position, drawn at a
smaller
scale;
[0032] Fig. 11 is a sectional view showing the outer ring of Fig. 6a in the
forward
position;
[0033] Fig. 12 is a sectional view showing the outer ring in the returned
position
and the die holder in the open position after hydroforming is complete;
[0034] Fig. 13a is a plan view of two rings which are included in an
embodiment
of the outer ring of the invention, drawn at a smaller scale;
[0035] Fig. 13b is a plan view of a portion of the rings of Fig. 13a, 'drawn
at a
larger scale;
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[0036] Fig. 14 is a sectional view of an alternative embodiment of a tapered
wedge, drawn at a larger scale;
[0037] Fig. 15a is a sectional view of an alternative embodiment of the outer
ring
of the invention including two sets of tapered wedges and cylinders and upper
and
lower cams associated therewith, drawn at a smaller scale;
[0038] Fig. 15b is a sectional view of a set of the tapered wedges and
cylinders of
Fig. 15a, drawn at a larger scale;
[0039] Fig. 16 is a sectional view of an embodiment of a hydroforming
apparatus
according to the invention with two outer rings, drawn at a smaller scale;
[0040] Fig. 17 is a sectional view of an alternative embodiment of a
hydroforming
apparatus according to the invention in which a diaphragm filled with
hydraulic pressure
is employed to keep the die closed;
[0041] Fig. 18a shows an alternative embodiment of the invention, including a
double tapered wedge and lower cam segment; and
[0042] Fig. 18b is a sectional view of an upper tapered wedge and cam segment
of the invention illustrated in Fig. 18a.
DETAILED DESCRIPTION
[0043] As shown in Figs. 1, 4a, 4b, 5a, and 5b, in one embodiment, the
hydroforming apparatus 108 according to the current invention includes a die
110
having a lower die section 112 and an upper die section 114. The lower and
upper die
sections 112, 114 preferably combine to define a die cavity 116. The lower die
section
112 is mounted in a lower die holder 126 and the upper die section 114 is
mounted in
an upper die holder 128. The lower die 112 and the lower die holder 126
preferably are
fixed and the upper die 114 and the upper die holder 128 are movable up and
down
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between an open position (as shown in Figs. 4a and 4b) and a closed position
(as
shown in Figs. 5a and 5b).
[0044] The upper die holder 128 is guided to and from the lower die holder 126
by using guide rods 125 and guide bushings 130 or by any other means that are
obvious to those who are skilled in the art. Furthermore, the upper die holder
128 is
moved up and down using a hydraulic cylinder 132 mounted to a frame 134 or by
any
other suitable means as would be known by those skilled in the art.
[0045] Furthermore an outer surface 127 of the lower die holder 126 is
provided
with a half-cylindrical shape and an outer surface 129 of the upper die holder
128 is
provided with a half-cylindrical shape so that when the upper die holder 128
is moved to
the closed position, the outer surface 127 of the lower die holder 126 and the
outer
surface 129 of the upper die holder 128 combine to form a cylindrical shape
(Figs. 5a,
5b).
[0046] As can be seen in Figs. 6a, 6b, 6c, 6d, 7a, 7b, 8a, and 8b, the current
invention includes an outer ring subassembly 136 including a ring 138, a first
cam
segment 140, a tapered wedge 142, and a second cam segment 144. The first cam
segment 140 is attached to an inner surface 139 of the ring 138 and the second
cam
segment 144 is attached to the ring 138 using bolts 58 and springs 60 (Fig.
8). The
second cam segment 144 is allowed to travel in the directions of arrows Ri, R2
(Figs. 6b,
7b) between an open position (Figs. 6a, 6b) and a closed position (Figs. 7a,
7b).
[0047] The tapered wedge 142 is placed between the first cam segment 140 and
the second cam segment 144 and is moved by a cylinder 148. The tapered wedge
142
is allowed to move in the directions of arrows Xl, X2 (Figs. 6b, 7b) between a
retracted
position (Figs. 6a, 6b) and an extended position (Figs. 7a, 7b). The cylinder
148 is
attached to the ring 138 by a mounting bracket 150. Each tapered wedge 142 has
a
substantially planar surface 143.
[0048] A contact surface 152 of the tapered wedge 142 is positioned at a small
angle 153 relative to a plane ("P" in Fig. 6c) parallel to the planar surface
143 that is
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less than 45 degrees. Also, the second cam segment 144 has a substantially
planar
surface 145. A mating surface 154 of the second cam segment 144 is positioned
at a
small angle 155 relative to a plane ("Q" in Fig. 6d) parallel to the mating
surface 154.
Preferably, the angle 155 is the same as the small angle 153 (as illustrated
in Fig. 6c)
so that when the tapered wedge 142 is in the retracted position, the second
cam
segment 140 is moved by the spring 160 (Fig. 8b) to the open position as shown
in Fig.
6b. Also, as the tapered wedge 142 is moved to the extended position, the
second cam
segment 140 is moved to the closed position as shown in Figs. 7a, and 7b.
[0049] The cylinder 148 exerts force Fl on the said tapered wedge 142 (Fig.
7b).
The contact surface 152 of the tapered wedge 142 is in contact with the mating
surface
154 of the second cam segment 144 so that the force Fl that is exerted on the
tapered
wedge 142 results in a force F2 that is exerted on the second cam segment 144
in a
direction perpendicular to the said force Fl (Fig. 7b). Because the angles 153
and 155
are each less than 45 degrees, the force F2 is greater than the force Fl. In
practice
and according to this invention, the angles 153 and 154 provide a slope having
a ratio
between 5:1 to 20:1 (i.e., relative to the planar surfaces 143, 145
respectively) so that
the force F2 is greater than the said force Fl by a ratio of between about 5
times and
about 20 times respectively.
[0050] With reference to Fig. 8b, a lower surface 156 of the second cam
segment
144 is curved with the same cylindrical radius as the outer surfaces 127 and
129 of the
lower die holder 126 and the upper die holder 128.
[0051] With reference to Fig. 8b, the first cam segment 140, the tapered wedge
142, and the second cam segment 144 preferably are equal in number to each
other.
Fig. 8a shows 24 first cam segments 140, the tapered wedges 142, and second
cam
segments 144.
[0052] With reference to Figs. 9a and 9b, the outer ring subassembly 136 is
guided by guide rods 162 and guide bushings 164 so that the outer ring
subassembly
136 can be moved horizontally between a forward position (Figs. 1, 11) and a
returned
position (Fig. 10). The movement of the outer ring subsequently 136 can be by
a
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cylinder or a motor and gear and rack or any other suitable means as is known
by those
who are skilled in the art. The means of guiding the outer ring subassembly
136 can be
as described using the guide rods 162 and the guide bushings 164 or by any
other
suitable means.
[0053] Fig. 10 shows the upper die holder 128 and the upper die section 114 in
the closed position, with the tube 22 in the cavity 116. The side plugs 18 and
20 are
positioned to seal both ends of the tube 22. The outer ring subassembly 136 is
in the
returned position and the tapered wedges 142 are in the retracted position
(Fig. 10)
allowing the second cam segments 144 to move to the open position (Fig. 10).
The
outer ring subassembly 136 is moved horizontally to the forward position
(Figs. 1, 11) so
that the lower die holder 126 and the upper die holder 128 are contained
inside the
second cam segments 144. Next, the cylinders 148 are extended, moving the
tapered
wedges 142 to the extended position and the second cam segments 144 to the
closed
position. The curved lower surfaces 156 of the lower cam segments 144 contact
the
curved outer surface 127 of the lower die holder 126 and the curved outer
surface 129
of the upper die holder 128. The cylinders 148 exert the force Fl (Fig. 7b) on
the
tapered wedges 142 and the tapered wedges 142 consequently exert the force F2
(Fig.
7b) on the second cam segments 144. Since the second cam segments 144 are in
contact with the lower die holder 126 and the upper die holder 128, the force
F2 is
transmitted to the lower and upper die holders 126 and 128. The force F2 keeps
the
lower and upper die holders 126 and 128 closed and keeps the lower die section
112
and the upper die section 114 closed during the hydroforming operation.
[0054] Next, a hydraulic pressure source (not shown) is connected to the
interior
of the tube 22 through the opening 124 inside the plugs 118 and 120 to provide
fluid
under pressure which expands the tube 22 until the tube 22 conforms to the
shape of
the die cavity 116, as is known in the art. Then, the hydraulic pressure
source is
disconnected and the cylinders 148 are retracted, moving the tapered wedges
142 to
the retracted position and the second cam segments 144 to the open position
(Figs. 6a,
6b). This allows the outer ring subassembly 136 to move horizontally to the
returned
position (Fig. 10). After the outer ring subassembly 136 has been moved to the
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returned position, the upper die holder 128 and the upper die segment 114 are
moved
to the open position, allowing the removal of the tube 22 as illustrated in
Fig. 12.
[0055] Since the force F2 is greater than the force Fl, the force require to
keep
the die 110 closed during the hydroforming operation of the invention is
smaller than
would be needed in a prior art hydroforming apparatus.
[0056] Also, since the force F2 required to keep the die 110 closed is
contained
within the outer ring subassembly 138 (which has a cylindrical shape, known to
be
efficient in load carrying), the structure of the apparatus of the invention
is smaller and
lighter than that of the prior art.
[0057] Additional embodiments of the invention are shown in Figs. 13a, 13b,
14,
15a, 15b, 16, 17, 18a, and 18b. In Figs. 13a, 13b, 14, 15a, 15b, 16, 17, 18a,
and 18b,
elements are numbered so as to correspond to like elements shown in Figs. 1,
4a, 4b,
5a, 5b, 6a, 6b, 6c, 6d, 7a, 7b, 8a, 8b, 9a, 9b, 10, 11, and 12.
[0058] As shown in Figs. 18a and 18b, in another embodiment of the invention,
the bolts 158 and the springs 160 (i.e., such bolts and springs shown in Fig.
8b being
included in the hydroforming apparatus 108) are replaced by a double tapered
wedge
278 (instead of the tapered wedge 42) and double tapered lower cam segment 282
(instead of the lower cam segment 44) or any other suitable means so that the
second
taper 280 is used to move the lower cam segments 282 to the open position.
[0059] In another embodiment of the invention, an outer ring subassembly 336
includes a ring 338 which is made of two or more rings 368 and 370, as
illustrated in
Figs. 13a and 13b. Preferably, the outer ring 368 is pressed over the inner
ring 370 so
that the outer ring 368 is exerting pressure F3 over the outer surface of the
inner ring
370, and the outer ring 368 is under tension forces F4 while the inner ring
370 is under
compression forces F5. The amount of the pressure F3 is such that the
compression
force F5 in the inner ring 370 is greater than the force F2 required to keep
the die 10
closed during the hydroforming operation such that no expansion in the ring
338 occurs
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as a result of the hydroforming operation. Also, the energy required to keep
the die 10
closed during the hydroforming operation is kept to a minimum.
[0060] As shown in Fig. 14, in another embodiment of the invention, a tapered
wedge 442 is made of one tapered ring 443 and moved by one cylinder 474. In
this
embodiment, the tapered lower surface 452 of the tapered ring 443 is
cylindrical in
shape and the upper tapered surface 454 of the lower cam segment 444 is also
cylindrical to match the tapered and cylindrical surface 452. Similarly an
outer surface
472 of the tapered ring 443 is cylindrical and matches the inner surface 439
of the outer
cam segments 440.
[0061] Figs. 15a and 15b disclose another embodiment of the invention. In this
embodiment, the outer ring 538 provides the tapered wedges 542 and the upper
cam
segments 540 and the lower cam segments 544 and the cylinders 548 and the
brackets
550 from both sides of the die, as illustrated.
[0062] In another alternative embodiment of the invention it is preferred that
two
of the outer rings 636 (one from either side of the upper and lower die
holders 626 and
628 as illustrated in Fig. 16) are provided so that the travel of the outer
ring 636
between the forward and return positions is kept to a minimum.
[0063] In another embodiment of the invention a diaphragm 776 is used instead
of the tapered wedges, the cylinders, and the upper and lower cam segments
(Fig. 17).
The diaphragm 776 is filled with hydraulic fluid and hydraulic pressure is
added inside
the diaphragm 776 such that the diaphragm 776 will exert force on the upper
and lower
die holders 726 and 728 so that the die 10 is kept in the closed position
during the
hydroforming operation.
[0064] The movement of the outer ring horizontally between the open and closed
positions can be vertically between an upper and lower position and the die
holders 728
and 726 and the die 10 are mounted vertically.
[0065] The invention describes a fixed lower die holder 26 and lower die 12
and a
movable die upper holder 28 and upper die 14. Both the upper and lower die
holders
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26 and 28 and the upper and lower dies 12 and 14 can be movable or the upper
die
holder 28 and the upper die 14 are fixed while the lower die holder 26 and the
lower die
12 are movable.
[0066] The invention being thus described, it will be obvious that the same
may
be varied in many ways. Such variations are not to be regarded as a departure
from the
spirit and scope of this invention, and all such modifications as would be
obvious to one
skilled in the art are intended to be included within the scope of the
following claims.
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