U.S. patent application number 09/845346 was filed with the patent office on 2002-11-07 for hydroformed vehicle frame assembly and method.
Invention is credited to Gabbianelli, Gianfranco, Perry, William.
Application Number | 20020162224 09/845346 |
Document ID | / |
Family ID | 25295023 |
Filed Date | 2002-11-07 |
United States Patent
Application |
20020162224 |
Kind Code |
A1 |
Gabbianelli, Gianfranco ; et
al. |
November 7, 2002 |
Hydroformed vehicle frame assembly and method
Abstract
A method for forming a vehicle side rail structure includes
forming a cylindrical tubular metal blank, forming a conical
tubular metal blank, the conical tubular metal blank having a wider
end portion and a narrower end portion, and joining the wider end
portion of the conical tubular metal blank to one end portion of
the cylindrical tubular metal blank by welding to form a welded
tubular assembly. The method further includes bending the
cylindrical tubular metal blank portion of the welded tubular
assembly and hydroforming the welded tubular assembly by placing
the welded tubular assembly into a hydroforming die cavity and
pressuring an interior of the welded tubular assembly with
hydroforming fluid so as to expand the welded tubular assembly into
general conformity with surfaces defining the die cavity. The die
cavity surfaces defines a generally octagonal shape along a portion
thereof so as to conform the conical tubular metal blank portion of
the welded tubular assembly therewith and thereby provide the
conical tubular metal blank portion of the welded tubular assembly
with a generally octagonal cross-sectional configuration.
Inventors: |
Gabbianelli, Gianfranco;
(Troy, MI) ; Perry, William; (Shalby Township,
MI) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
25295023 |
Appl. No.: |
09/845346 |
Filed: |
May 1, 2001 |
Current U.S.
Class: |
29/897.2 |
Current CPC
Class: |
B62D 21/02 20130101;
Y10T 29/49622 20150115; B21D 26/033 20130101; B62D 21/12 20130101;
B62D 65/00 20130101 |
Class at
Publication: |
29/897.2 |
International
Class: |
B21D 053/88 |
Claims
In the claims:
1. A method for forming a vehicle side rail structure, comprising:
forming a cylindrical tubular metal blank; forming a conical
tubular metal blank, said conical tubular metal blank having a
wider end portion and a narrower end portion; joining said wider
end portion of said conical tubular metal blank to one end portion
of said cylindrical tubular metal blank by welding to form a welded
tubular assembly; bending said cylindrical tubular metal blank
portion of said welded tubular assembly; hydroforming said welded
tubular assembly by placing said welded tubular assembly into a
hydroforming die cavity and pressuring an interior of said welded
tubular assembly with hydroforming fluid so as to expand said
welded tubular assembly into general conformity with surfaces
defining said die cavity, said die cavity surfaces defining a
generally octagonal shape along a portion thereof so as to conform
said conical tubular metal blank portion of said welded tubular
assembly therewith and thereby provide said conical tubular metal
blank portion of said welded tubular assembly with a generally
octagonal cross-sectional configuration.
2. A method of forming a vehicle frame module including a pair of
side rail structures interconnected by a cross structure,
comprising: (i) forming each of said pair of side-rail structures
by: forming a conical tubular metal blank, said conical tubular
metal blank having a wider end portion an a narrower end portion;
joining said wider end portion of said conical tubular metal blank
to one end portion of said cylindrical tubular metal blank by
welding to form a welded tubular assembly; hydroforming said welded
tubular assembly by placing said welded tubular assembly into a
hydroforming die cavity and pressuring an interior of said welded
tubular assembly with hydroforming fluid so as to expand said
welded tubular assembly into general conformity with surfaces
defining said die cavity, said die cavity surfaces defining a
generally octagonal shape along a portion thereof so as to conform
said conical tubular metal blank portion of said welded tubular
assembly therewith and thereby provide said conical tubular metal
blank portion of said welded tubular assembly with a generally
octagonal cross-sectional configuration; (ii) forming a pair of
connecting sleeves, each formed separately from said side rail
structures, said connecting sleeves having a relatively narrowed
end and a relatively wider end; (iii) disposing said connecting
sleeves in surrounding relation to respective ones of said side
rail structures in the vicinity of said welded joints of said
hydroformed welded tubular assemblies; (iv) welding said relatively
narrow ends of said connecting sleeves to said respective ones of
said side rail structures; (v) attaching opposite ends of a cross
member to said connecting sleeves so that said cross member extends
between said connecting sleeves.
3. A method according to claim 2, further comprising bending said
cylindrical tubular metal blank prior to said hydroforming.
4. A method according to claim 2, wherein said connecting sleeves
are each formed from a pair of sleeve members each constructed of a
metal material and each sleeve member having two free end portions
and wherein said disposing comprises placing each pair of members
in surrounding relation with one of said side rail structures in
the vicinity of the welded joint thereof and welding associated
free end portions of each pair of sleeve members to one
another.
5. A method according to claim 4, wherein each sleeve member of
each said pair has a C-shaped cross section.
6. A method according to claim 4, wherein said relatively narrow
ends of said connecting sleeves are each welded to a portion of an
associated side rail structure that was formed from said
cylindrical tubular metal blank portion.
Description
FIELD OF THE INVENTION
[0001] The present invention is generally related to motor vehicle
frame structures and more particularly to a frame assembly of
tubular hydroformed construction.
BACKGROUND OF THE INVENTION
[0002] Conventional prior art motor vehicle frames are typically
formed by stamping several structural components and then welding
these individually stamped structures together. In more recent
years, stamped and welded frame members have to some extent been
replaced by hydroformed frame members.
[0003] Hydroforming is a technique that utilizes high pressure
fluid to outwardly expand the metallic wall of a longitudinally
extending tubular blank into conformity with the surfaces of a die
cavity of a die assembly. An individual hydroformed member can have
a wide range of cross-sectional geometries previously not
achievable on a practical, cost-effective basis. Generally, a blank
is a tubular member having a pair of open ends, a uniform
cross-sectional geometry and a uniform wall thickness. During
hydroforming, selected portions of the blank may be outwardly
expanded to vary the cross-sectional geometry and/or circumference
of portions of the blank. Outward expansion tends to reduce wall
thickness in the area of the expansion which may be undesirable.
Wall thinning can be compensated for to a certain degree by pushing
one or both ends of the blank axially inwardly during outward
expansion. This causes metal flow into the areas of outward
expansion, thereby replenishing wall thickness in these areas.
There are limits, however, on the amount of expansion of a single
blank that can be achieved without excessive wall thinning.
[0004] When large variations in cross-sectional size and/or
geometry of a hydroformed structure are required for a particular
application, it has been proposed to hydroform two members
separately and then join the two hydroformed members to one another
after hydroforming to form a single structure having the desired
geometry along its length. Individually hydroformed parts can be
joined, for example, by welding. Individual hydroformed parts are
highly dimensionally accurate (as compared to, for example, stamped
parts). Welding two individual hydroformed parts to form a larger
hydroformed structure may introduce dimensional inaccuracies in the
hydroformed structure, in part because the two hydroformed members
may not be properly positioned with one another prior to welding
and in part because the heating and cooling of the hydroformed
members that occurs during welding may distort the shape of one or
both members and therefore of the resulting hydroformed structure.
Specifically, the heating required to form a weld may cause
unpredictable and uncontrollable distortions in the geometry of the
hydroformed structure and may compromise the dimensional accuracy
that would otherwise be achievable from hydroforming. Hydroforming
individual parts and then welding them to one another in a
subsequent manufacturing step may also increase manufacturing costs
by requiring separate hydroforming dies for each member of a
particular structure.
[0005] Tubular hydroforming has been proposed for the lower side
rail components of vehicle ladder frame assemblies. Some vehicle
frame designs require relatively large variations in
cross-sectional geometry of the lower side rails, particularly to
address vehicle crashworthiness. Crush caps are sometimes mounted
on the forward ends of side rails and are constructed and
positioned to absorb the energy of a head-on crash. It is known to
hydroform a crush cap and a portion of a lower side rail separately
and to join the hydroformed crush cap and hydroformed side rail at
a joint in a subsequent manufacturing step. This manufacturing
procedure may compromise the dimensional accuracy of the frame and
may increase manufacturing costs for the reasons cited above. There
is a need in the automotive industry for a more accurate and more
economical method of mounting a crush cap on a vehicle side
rail.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method of forming a vehicle
side rail structure comprising (a) forming a cylindrical tubular
metal blank; (b) forming a conical tubular metal blank, the conical
tubular metal blank having a wider end portion and a narrower end
portion; and (c) joining the wider end portion of the conical
tubular metal blank to one end portion of the cylindrical tubular
metal blank by welding to form a welded tubular assembly. The
welded tubular assembly is shaped by hydroforming to form the
vehicle side rail structure. The welded tubular assembly may
optionally be bent prior to hydroforming. For example, the
cylindrical tubular metal blank portion of the welded tubular
assembly may be bent. The welded tubular assembly is then
hydroformed by placing the welded tubular assembly into a
hydroforming die cavity and pressurizing an interior of the welded
tubular assembly with a hydroforming fluid so as to expand the
welded tubular assembly into general conformity with surfaces
defining the die cavity. The die cavity surfaces define a generally
octagonal shape along a portion thereof so as to conform the
conical tubular metal blank portion of the welded tubular assembly
therewith and thereby provide the conical tubular metal blank
portion of the welded tubular assembly with a generally octagonal
cross-sectional configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 shows a perspective view of a modular ladder frame
assembly constructed according to the principles of the present
invention;
[0008] FIG. 2 is a partially exploded perspective view of the frame
assembly of FIG. 1 showing a forward module, a central module, and
a rearward module in exploded relation to one another;
[0009] FIG. 3 is a side elevational view of a side rail assembly of
the modular ladder frame assembly;
[0010] FIG. 4 is a view similar to FIG. 4 except showing portions
of the side rail assembly in exploded relation;
[0011] FIG. 5 is a cross sectional view of a welded tubular
assembly within a die cavity of a hydroforming die assembly shown
schematically and of a pair of ram members of a hydroforming ram
assembly shown schematically and in fragmentary view;
[0012] FIG. 6 is a side elevational view of the modular ladder
frame assembly;
[0013] FIG. 7 is an enlarged fragmentary view of a portion of the
modular ladder frame assembly as indicated in FIG. 1;
[0014] FIG. 8 is a view similar to FIG. 7 except having a portion
of a connecting sleeve of the modular ladder frame assembly broken
away and not shown to show more clearly a portion of a forward side
rail structure of the modular ladder frame assembly; and
[0015] FIG. 9 is an enlarged fragmentary view of another embodiment
of a ladder frame assembly showing a connecting sleeve thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIG. 1 shows a perspective view of a ladder frame assembly
10 constructed according to the principles of the present
invention. The ladder frame assembly 10 includes a forward module
12, a central module 14, and a rearward module 16. The modules 12,
14, 16 are shown in exploded relation in FIG. 2. The assembled
ladder frame assembly 10 includes a pair of longitudinally
extending side rail assemblies 24, 26 and a plurality of laterally
extending cross structures generally designated 28 interconnected
therebetween.
[0017] The side rail assemblies 24, 26 are of mirror image
construction so only side rail assembly 24 will be considered in
detail, but the discussion applies equally to side rail assembly
26. Corresponding portions of the side rail assemblies 24, 26 are
designated by identical reference numbers to facilitate discussion
of the invention. It can be understood, however, that these
corresponding portions are of mirror image construction.
[0018] The side rail assembly 24 includes a forward side rail
structure 30, a central side rail structure 32 and a rearward side
rail structure 34. The forward module 12 includes the forward side
rail structure 30 and forward cross structure interconnected
therebetween. The forward cross structure includes first, second,
third and fourth cross structures 36, 38, 40 and 42, respectively.
The central module 14 includes the central side rail structures 32
and a central cross structure 44 rigidly interconnected
therebetween. The rearward module 16 includes a pair of rearward
side rail structures 34 and a rearward cross structure 46 and
rearward cross assembly 48 interconnected therebetween.
[0019] The rearward side rail structure 34 includes two hydroformed
rail portions 50, 52 connected at joint 54. The central side rail
structure 32 is preferably a tubular structure formed by roll
forming and then seam welding a sheet of metallic material. The
forward side rail structure 30 is of tubular hydroformed
construction and includes hydroformed rail portions 56, 58
connected at joint 60 (see FIGS. 3 and 8, for example).
[0020] The structure of the tubular hydroformed forward side rail
structure 30 can be understood from FIGS. 3 and 4. Many of the
structural features of the forward side rail structure 30 are
formed during the hydroforming operation that creates the same. A
hydroforming operation for forming the forward side rail structure
30 can be understood from FIG. 5. The forward side rail structure
30 is formed by hydroforming a welded tubular assembly 62. The
welded tubular assembly 62 is comprised of a roll formed
cylindrical tubular metal blank 64 and a roll formed conical
tubular metal blank 66. The conical tubular metal blank 66 has a
wider end portion (or wide end portion) 68 and a narrower end
portion (or narrow end portion) 70. The wider end portion 68 has a
larger circumference than the narrower end portion 70. The welded
tubular assembly 62 is formed by welding the wide end portion 68 of
the conical tubular metal blank 66 to one end portion 72 of the
cylindrical tubular metal blank 64. Preferably the wide end portion
68 of the conical blank 66 is inserted inside the one end portion
of the cylindrical blank 64 in telescopic relation therewith and
welded to form the joint 60. Alternatively, a welded tubular
assembly may be constructed by forming a conical blank that may be
joined to a cylindrical blank by welding an end of the cylindrical
blank inside a wide end of the conical blank. The blanks 64, 66 may
be welded to one another by laser welding or any other suitable
welding method. Laser welding is preferred because the joint 60
should be "fluid tight". That is, joint 60 should be constructed to
prevent a pressurized hydroforming fluid inside the welded tubular
assembly from passing through the joint 60 to the outside of the
welded tubular assembly during hydroforming.
[0021] Each blank 64, 66 is constructed of a suitable metallic
material and has a closed transverse cross section and open tubular
ends. Preferably, each blank 64, 66 is constructed of a suitable
steel (such as, for example, a suitable high strength low alloy, or
"HSLA", steel) or other metallic material of sufficient strength.
Each blank 64, 66 may be formed by any suitable method. For
example, the cylindrical blank 64 may be formed from a continuous
strip of metallic material that is shaped by roll forming and seam
welded to have a closed transverse cross section. The continuous
tubular structure may then be cut to the length required. The
conical tubular metal blank may be formed by roll forming and seam
welding a wedge-shaped sheet of metallic material.
[0022] The cylindrical portion of the welded tubular assembly 62 is
preferably bent prior to being placed in a hydroforming assembly.
As shown in FIG. 5, for example, the cylindrical blank 64 of the
welded tubular assembly 62 is bent in two places. If a relatively
"sharp" bend or angle (that is, an angle greater than 30 degrees)
is required in the tubular hydroformed structure, the present
invention may bend and hydroform the blank 64 according to the
teachings of U.S. Pat. No. 5,953,945 entitled METHOD AND APPARATUS
FOR WRINKLE-FREE HYDROFORMING OF ANGLED TUBULAR PARTS, which patent
is hereby incorporated by reference into the present application in
its entirety. The blank 64 portion of the welded tubular assembly
62 may be bent in a computer numeric controlled ("CNC") bending
machine prior to being placed in the die assembly or,
alternatively, may be bent by stretch bending, or by any other
suitable method. A suitable lubricant may be applied to the
exterior of the welded tubular assembly 62 prior to placing it in a
die assembly.
[0023] The welded tubular assembly 62 is then placed between the
die halves 74, 76 of the die assembly 78 and the assembly is
closed. The welded tubular assembly 62 is preferably immersed in a
fluid bath so that it is filled with hydroforming fluid (not
shown). A hydroforming ram assembly 80, 82 (a portion of each is
represented schematically in FIG. 5) is engaged with each end 70,
84 of the welded tubular assembly 62 such that a ram member 86, 88
of each assembly 80, 82 seals an end 84, 70, respectively, of the
welded tubular assembly 62. The ram members 86, 88 include
hydraulic intensifiers which can intensify the hydroforming fluid,
thereby increasing the fluid pressure of the fluid within the
welded tubular assembly 62 to outwardly expand the tubular metallic
walls, 90, 92, respectively, of the tubular blanks 64, 66 of the
assembly 62 into conformity with the die surfaces 94 of the die
cavity to thereby form a tubular hydroformed side rail structure 30
having an exterior surface that is fix into a predetermined
(determined by the shape of the die cavity) configuration.
Preferably each blank 64, 66 is constructed of the same metallic
material and the walls 90, 92 are of approximately equal thickness
to one another, although neither of these conditions is required by
the invention. That is, the blanks 64, 66 may be constructed of
different materials from one another and/or the thickness of the
walls 90, 92 may be different from one another.
[0024] The cylindrical blank 64 may have, for example, an
essentially constant circumference and an essentially circular
cross section along its length prior to outward expansion during
the hydroforming operation. The conical tubular blank 64 may have,
for example, an essentially circular cross section at each point
along its length. Thus, the circumference of the conical blank 66
decreases from the wide end 68 to the narrow end 70 (prior to
outwardly expansion), but the cross section at any point is
circular. The hydroforming process may be computer controlled to
control the flow of the hydroforming fluid to thereby control the
manner in which the metallic material of the welded tubular
assembly 62 expands (in a radial direction) during the hydroforming
process. The die cavity of the die assembly 78 is shaped to provide
a rearward portion of the welded tubular assembly 62 with a
quadrilateral (preferably rectangular) cross-section, the forward
portion of the assembly 62 with an octagonal cross section, and an
intermediate transition portion of the welded tubular assembly 62
with a cylindrical cross section in the area of the welded joint 60
therebetween. This construction is best appreciated from FIG.
8.
[0025] The fluid pressure and the axial pressure may be controlled
independently of one another. The ram members 86, 88 may push
axially inwardly on opposite ends 70, 84 of the welded tubular
assembly 62 to create metal flow within the walls 90, 92 of the
assembly 62 during outward expansion to maintain the thickness of
each wall 90, 92 within a predetermined range of its original wall
thickness. The ram members 86, 88 may be operated, for example, to
maintain the wall thickness of each wall 90, 92 of the respective
tubular blanks 64, 66 within about +/-10% of its original wall
thickness.
[0026] The fluid pressure within the welded tubular assembly 62
causes the walls 90, 92 to expand into conformity with the surfaces
94 defining the hydroforming die cavity so as to irregularly
outwardly expand the walls into conformity with the surfaces 94 and
thereby provide the welded tubular assembly 62 with a shape
corresponding to the forward side rail structure 30. The shape of
the die cavity thus corresponds to the shape of the forward side
rail structure 30. More particularly, the die cavity defines a
generally octagonal shape along a portion thereof so as to conform
the conical tubular metal blank portion 66 of the welded tubular
assembly 62 therewith and thereby provide the conical tubular metal
blank portion 66 of the welded tubular assembly 62 with a generally
octagonal cross-sectional configuration as a result of the
hydroforming operation.
[0027] If holes are to be formed in a hydroformed forward side rail
structure 30, the holes may be formed while the side rail structure
30 is in the die assembly 78 during the hydroforming operation or
may be formed after the structure 30 is removed from the die
assembly along with any other required further processing of the
structure 30. More particularly, holes may be formed during the
hydroforming process in what is known as a hydropiercing operation.
A hydropiercing operation is disclosed in U.S. Pat. No. 5,460,026
which is hereby incorporated by reference in its entirety into the
present application. Alternatively, holes or notches of various
sizes and shapes may be cut (preferably using a laser) in the
forward side rail structure 30 after the hydroforming operation is
completed.
[0028] It can be appreciated that, as a result of the expansion of
the welded tubular assembly 62 during the hydroforming operation,
the transverse cross section of the forward side rail structure 30
varies along its length to have quadrilateral (preferably
rectangular), octagonal, and cylindrical cross sections as
described above. It is also contemplated to hydroform the various
portions of the forward side rail structure 30 to have other cross
sectional configurations (including other sizes and shapes). It can
thus be understood that altering the cross-sectional configuration
of the tubular hydroformed forward side rail structure 30 can be
accomplished without departing from the principles of the present
invention.
[0029] It can be appreciated that the rearward side rail structure
34 may be formed by carrying out a method similar to the method for
making the forward side rail structure 30. That is, two or more
tubular blanks (each of which may be formed by roll forming) may be
welded together to form a welded tubular assembly. The welded
tubular assembly may be bent and hydroformed to form the rearward
side rail structure 34.
[0030] The ladder frame assembly 10 may be constructed by first
assembling the modules 12, 14, 16 and then connecting the assembled
forward and rearward modules 12, 16 to the forward and rearward
ends, respectively, of the assembled central module 14. The
assembled modules 12, 14, 16 are shown in FIG. 2.
[0031] To assemble the rearward module 16, the rearward cross
assembly 48 and the rearward cross structure 46 may be
interconnected between the rearward side rail structures 34 by
welding or other appropriate method. To assemble the central module
14, the central cross structure 44 may be connected between the
central side rail structures 32 by welding or other appropriate
method. The forward modules 12 may be assembled by welding the
cross structures 36, 38, 40, 42 between the forward side rail
structures 30. Each cross structure 36, 38, 40, 42 is preferably a
metallic structure that is constructed of one or more pieces that
have each been shaped by stamping and welded together. The cross
structures 38, 40 and 42 are connected between the quadrilateral
rearward portions of the forward side rail structure 30. The manner
in which the cross structure 36 is connected between the forward
side rail structure 30 can be appreciated from FIGS. 7 and 8.
[0032] A pair of connecting sleeves 104, 106 are disposed in
surrounding relation to respective forward side rail structures 30.
The connecting sleeves 104, 106 are identical so only sleeve 104
will be discussed in detail, but the discussion applies equally to
sleeve 106. The connecting sleeve 104 has a relatively narrow end
108 and a relatively wide end 110. The connecting sleeve 104 is
disposed on the forward side rail structure 30 in the vicinity of
the welded joint 60 of the hydroformed welded tubular assembly 62.
Specifically, the relatively narrow end 108 of the sleeve 104 is
welded in the vicinity of the joint 60 to the exterior of the
forward end of the portion of the side rail structure 30 formed
from the cylindrical tubular blank 64.
[0033] The relatively wide end 110 of the connecting sleeve 104
provides an attachment surface to which one end of the first cross
structure 36 may be attached. Opposite ends of the first cross
structure 36 are thus connected to respective connecting sleeves
104, 106 so that the cross structure extends between the sleeves
104, 106. The connecting sleeve 104 thus provides a support
structure and an attachment surface on the forward end of the side
rail assembly 24 for the first cross structure 36. As best
appreciated from FIG. 7, the wide end portion 110 of the connecting
sleeve 104 is spaced radially outwardly from the relatively smaller
diameter octagonally shaped forward end of the forward side rail
structure 30. The octagonal forward end portion of the side rail
structure 30 is constructed and arranged to be "crumpled" or
crushed in the event that the front end of a vehicle constructed
using the ladder frame assembly 10 is involved in a head-on vehicle
accident. The connecting sleeve 104 is constructed to allow
crumpling of the octagonal forward end portion (that is, the
portion forward of the joint 60) of the forward side rail structure
30 while providing a secure attachment structure for the first
cross structure 36 to maintain the structural integrity of the
vehicle frame 10 during crumpling of the octagonal end. For
example, the wide end 110 of the connecting sleeve 104 provides an
interior space constructed and arranged to allow crumpling of the
forward end portion of the side rail structure 30 during a
collision without breaking or weakening the joint between the first
cross structure 34 and the sleeves 104, 106. The sleeve may be of
one-piece construction and may be made of a metallic material that
has been shaped by roll forming and seam welding.
[0034] The connecting sleeve 104 is partially broken away and not
shown in FIG. 8 to show the structural details of a portion of the
forward module 12 in the vicinity of the sleeve 104 and of the
joint 60 more clearly. The construction of the joint 60 (formed
between the tubular blanks 64, 66 prior to hydroforming) can be
understood from FIG. 8. Specifically, a series of circumferentially
spaced openings 112 are formed in the end 72 of the blank 64. The
conical blank 66 is inserted into the end 72 of the cylindrical
blank 64 and the joint 60 is formed by welding. The blanks may be
welded together using laser welding, as mentioned above. Welding
material may be disposed within the openings 112 to secure the two
blanks 64, 66 together. It can also be appreciated from FIG. 8 that
the relatively narrow end 108 of the connecting sleeve 104 is
welded (by mig welding, for example) to a cylindrical exterior
surface portion of the forward side rail structures 30 in the
vicinity of the joint 60 and that the relatively wide end 110 of
the sleeve 104 extends forwardly from the joint 60 and radially
outwardly spaced from a portion of the octagonal forward end
portion of the side rail structure 30.
[0035] The hydroformed construction of the forward side rail
structure 30 can also be understood from FIG. 8. Specifically, it
can be understood that the forward side rail structure 30 is
hydroformed to have a relatively large circumference rearward end
portion 120 having a quadrilateral (preferably rectangular)
cross-section, a relatively small circumference forward end portion
122 having an essentially octagonal cross section and an
intermediate (or "transition") portion 124 therebetween in the
vicinity of the joint 60. The intermediate portion 124 has an
essentially circular cross-section. The octagonal forward end
portion 122 is tapered so that its circumference continuously
decreases in a direction forwardly of the joint 60 and terminates
in an octagonal tubular open end 126. Four circumferentially spaced
indentations or depressions 128 are formed near the open end 126 of
the forward end portion 122 of the side rail structure 30 during
hydroforming. The depressions 128 are constructed and arranged to
facilitate crush initiation during a collision.
[0036] A more preferred embodiment of the connecting sleeve is
shown in FIG. 9. FIG. 9 shows a connecting sleeve 130 mounted on
the forward side rail structure 30 of a vehicle ladder frame
assembly 132 (shown in fragmentary view). Portions of the vehicle
ladder frame assembly 132 that are identical to portions of the
frame 10 are identified by identical reference numerals and are not
described further. The connecting sleeve 130 is of multi-piece
construction. Preferably, two sleeve members 133, 135, each having
a C-shaped cross section are welded together to form the sleeve
130. Each member 133, 135 is preferably constructed of a metallic
material that has been shaped by stamping. Each member 133, 135
includes a wall structure 134, 136, respectively, which is
preferably constructed of a strip of metallic material having
opposite free end portions. The members 133, 135 are disposed in
surrounding relation around the side rail structure 30 in the
vicinity of the joint 60 of the forward side rail structure.
Opposite ends of the wall structure 136 (of member 135) are
"lapped" (that is, disposed in overlying relation) over and welded
to associated ends of the wall structure 134 (of the member 133) to
form the sleeve 130. The sleeve 130 is disposed around the forward
side rail structure 30 in the vicinity of the joint 60. Preferably
the sleeve 130 is welded to the side rail structure 30 by mig
welding, although any appropriate welding method can be used. The
wall structures 134, 136 are shaped to provide the sleeve 130 with
a relatively narrow end 138 which is attached to the side rail
structure 30 in the vicinity of the joint 60 and a relatively wide
end 140. The relatively wide end 140 provides attachment structure
for and an attachment surface for the first cross structure 36. One
or more weld openings 142 are provided in the portions of the wall
structures 134, 136 which define the relatively narrow portion 138
of the sleeve 130. The welding material (not shown) may be disposed
in each opening 142 (preferably by mig welding) to help secure the
sleeve 130 to the forward side rail structure 30.
[0037] Alternatively, a connecting sleeve (similar to sleeve 130,
for example) may be of one-piece construction. When this
construction is employed, a single strip of a metallic material may
be wrapped in surrounding relation around the front side rail
structure 30 in the vicinity of the joint 60, clamped thereto, and
welded to form the connecting sleeve.
[0038] It should be pointed out that although the ladder frame
assemblies described herein are referred to as "modular", this
characterization is intended to be broadly construed and is not
intended to limit the manner in which any of the ladder frame
assemblies is constructed. It is contemplated that each module
(such as modules 12, 14, 16 of the ladder frame assembly 10) be
assembled separately and then assembled to one another to form the
ladder frame assembly. An example of a method for connecting the
forward and rearward modules 12, 16 to the central module 14 can be
understood from FIG. 1. Each end of each roll formed central side
rail structure 32 may be provided with a "fish mouth" opening. The
rearward fish mouth openings 150 of the central module 14 are
constructed and arranged to receive the forward end portion of each
rearward side rail structure 34 of the rearward module 16 therein
in telescopic relation. Similarly, the forward fish mouth openings
152 are constructed and arranged to receive the rearward end
portions of the forward side rail structures 30 of the forward
module 12 therein in telescopic relation. Each fish mouth opening
150, 152 may then the crimped to hold the associated side rail
structure 34, 30 therein and each forward and rearward side rail
structure 30, 34 may then be welded (for example by mig welding) in
the associated fish mouth opening 152, 150.
[0039] It is contemplated to construct each ladder frame assembly
in a variety of ways, however, and so it is to be understood that
no limitations on the order in which the various hydroformed
members and other structural members are joined together to form
each ladder frame assembly is to be implied from anything shown or
stated in the present application. For example, the ladder frame
assembly 10 may be constructed by first connecting the forward side
rail structures 30 and the rearward side rail structures 34 to
respective ends of the central side rail structures 30 to as
illustrated in FIGS. 3 and 4 to form the pair of assembled side
rail assemblies 24, 26, and then connecting the assembled side rail
assemblies 24, 26 in laterally spaced relation to one another by
connecting the cross structure 28 therebetween.
[0040] Thus, it can be appreciated that although the ladder frame
assembly 10 in FIG. 2 is show in exploded view as a series of
assembled modules 12, 14, 16, it is understood that, while it is
contemplated and preferred to completely assemble each module
separately before the modules are connected together to form the
ladder frame assembly, this is not required by the invention and
the invention is therefore not limited to this method of
construction.
[0041] It can be understood that the modular approach allows a
particular module to be used in the construction of a wide range of
ladder frame assemblies. For example, the central module 14 of the
ladder frame assembly 10 shown in FIG. 1 generally defines the
passenger compartment portion of a vehicle. Several different
forward and rearward modules can be constructed for use on a
central module having a particular construction to provide ladder
frame assemblies having different configurations and/or different
lengths. A range of forward modules can be easily constructed, for
example, to accommodate a wide range of vehicle front
configurations. Similarly, the rear module can be reconfigured to
provide different ladder frame assembly lengths (and thus different
vehicle lengths) and a variety of vehicle styles and appearances.
It is contemplated to provide a wide range of forward modules that
include forward side rail structures each being constructed from a
welded tubular assembly that has been hydroformed to define a
tapered forward end portion having an octagonal cross-section as
described above.
[0042] Thus, while the invention has been disclosed and described
with reference with a limited number of embodiments, it will be
apparent that variations and modifications may be made thereto
without departure from the spirit and scope of the invention.
Therefore, the following claims are intended to cover all such
modifications, variations, and equivalents thereof in accordance
with the principles and advantages noted herein.
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