U.S. patent application number 09/845920 was filed with the patent office on 2001-10-18 for sheet metal hemming method and apparatus.
Invention is credited to Wiens, Philip V..
Application Number | 20010029766 09/845920 |
Document ID | / |
Family ID | 25296429 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029766 |
Kind Code |
A1 |
Wiens, Philip V. |
October 18, 2001 |
Sheet metal hemming method and apparatus
Abstract
A sheet metal hemming method and apparatus for securing inner
and outer sheet metal panels together by forming a generally flat
hem along respective peripheries of the two panels. A fixture
receives and holds an outer sheet metal panel that is formed to
include an upstanding border flange. An inner sheet metal panel is
stacked on top of the outer panel. A hemming tool movably supported
adjacent the fixture bends the upstanding border flange of the
outer sheet metal panel over a periphery of the inner panel and
into a position forming an acute angle relative to an underlying
portion of the outer panel. The hemming tool also bends an outer
portion of the border flange down onto the periphery of the inner
panel and into a position over and generally parallel to the
underlying portion of the outer sheet metal panel.
Inventors: |
Wiens, Philip V.; (Ontario,
CA) |
Correspondence
Address: |
REISING ETHINGTON BARNES KISSELLE
LEARMAN AND MCCULLOCH PC
P O BOX 4390
TROY
MI
48099-4390
US
|
Family ID: |
25296429 |
Appl. No.: |
09/845920 |
Filed: |
April 30, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09845920 |
Apr 30, 2001 |
|
|
|
09475748 |
Dec 30, 1999 |
|
|
|
6257043 |
|
|
|
|
Current U.S.
Class: |
72/312 |
Current CPC
Class: |
F16B 5/0096 20130101;
Y10T 29/53791 20150115; B21D 39/021 20130101 |
Class at
Publication: |
72/312 |
International
Class: |
B21D 011/00 |
Claims
What is claimed is:
1. A sheet metal hemming apparatus for securing two sheet metal
panels together by forming a generally flat hem along respective
peripheries of the two panels, the apparatus comprising: a fixture
configured to receive and hold a sheet metal panel having an
upstanding border flange; a hemming tool movably supported adjacent
the fixture and configured to bend the upstanding border flange of
a sheet metal panel supported on the fixture into a position
forming an acute angle relative to an underlying portion of the
panel; the hemming tool configured to bend an outer portion of the
border flange into a position over and generally parallel to the
underlying portion of the sheet metal panel.
2. A sheet metal hemming apparatus as defined in claim 1 in which
the hemming tool includes a roller configured to engage and bend
the border flange while rolling along a length of the flange.
3. A sheet metal hemming apparatus as defined in claim 2 in which
the roller includes a generally frusto-conical forming surface
configured and positioned to bend an inner portion of the border
flange into a position forming an acute angle relative to the
underlying portion of the panel.
4. A sheet metal hemming apparatus as defined in claim 3 in which
the frusto-conical forming surface is inclined relative to the
cylindrical forming surface at an obtuse included angle of between
110 and 160 degrees.
5. A sheet metal hemming apparatus as defined in claim 4 in which
the frusto-conical forming surface is inclined relative to the
cylindrical forming surface at an angle of about 125 to 145
degrees.
6. A sheet metal hemming apparatus as defined in claim 2 in which
the roller includes a generally cylindrical forming surface
configured and positioned to bend the outer portion of the border
flange into position over and generally parallel to the underlying
portion of the sheet metal panel.
7. A sheet metal hemming apparatus as defined in claim 2 in which:
the fixture is constructed to receive an inner sheet metal panel
stacked on an outer sheet metal panel having an upstanding border
flange; the roller is configured to hem the border flange over a
peripheral edge of the inner panel; and a frusto-conical forming
surface of the roller is disposed outboard of the peripheral edge
of the inner panel when the roller is engaged with the border
flange such that a cylindrical forming surface of the roller
overlies the inner panel.
8. A sheet metal hemming apparatus as defined in claim 2 in which
the hemming tool is configured to fold the border flange along a
fold line such that the fold line has an outer be nd diameter
that's less than three times the thickness of the sheet metal
panel.
9. A sheet metal hemming apparatus as defined in claim 2 in which
the hemming tool is configured to fold the border flange along a
fold line such that the fold line has an outer bend diameter that's
less than twice the thickness of the sheet metal panel.
10. A sheet metal hemming apparatus as defined in claim 2 in which
the hemming tool is configured to fold the border flange along a
fold line such that the fold line has an outer bend diameter that's
generally equal to the thickness of the sheet metal panel.
11. A sheet metal hemming apparatus as defined in claim 2 in which
the apparatus includes a robot arm configured to support the roller
for rotational and translational motion relative to the panels.
12. A sheet metal hemming apparatus as defined in claim 2 in which
the apparatus includes a roll form hemming machine configured to
support the roller for rotational and translational motion relative
to the panels.
13. A sheet metal hemming apparatus as defined in claim 2 in which
an inner end of the roller includes a radially-extending annular
rim configured to guide the roller along a periphery of the
fixture.
14. A sheet metal hemming apparatus as defined in claim 2 in which
the radially-extending roller annular rim is axially biased against
the fixture.
15. A sheet metal hemming apparatus as defined in claim 2 in which:
the roller is supported on a roller axle; and a ball roller is
supported on the roller axle in a position to guide the roller
along a periphery of the fixture by rolling along an outer wall of
the fixture.
16. A sheet metal hemming apparatus as defined in claim 2 in which
the apparatus includes a pre-hem tool configured to bend the border
flange to an acute included angle relative to the sheet metal
panel.
17. A sheet metal hemming apparatus as defined in claim 16 in which
the pre-hem tool bends the border flange to an angle between 25 and
75 degrees relative to the sheet metal panel.
18. A method for securing two sheet metal panels together by
forming a generally flat hem along respective peripheries of the
two panels, the method including the steps of: providing an outer
sheet metal panel having a generally upstanding border flange along
a periphery of the outer panel; folding the border flange until the
flange is inclined over an underlying portion of the outer panel;
and further folding the border flange such that an outer portion of
the flange is disposed generally parallel to an underlying portion
of the outer panel.
19. The method of claim 18 in which: the following additional steps
are included before the step of folding the border flange:
providing an inner sheet metal reinforcing panel that is slightly
smaller than the outer sheet metal panel; and placing the inner
panel against an inner surface of the outer panel such that a
peripheral edge of the inner panel is disposed adjacent and
generally parallel to the border flange of the outer panel; and in
which: the step of folding the border flange includes folding the
border flange until the flange is included against the peripheral
edge of the inner panel such that a distal edge of the panel is
spaced from the inner surface of the inner panel; and the step of
further folding the border flange includes folding the border
flange such that the portion of the flange disposed generally
parallel to the underlying portion of the outer panel lies flat
against the inner surface of the inner panel, securing the inner
panel to the outer panel.
20. The method of claim 18 in which the step of folding the border
flange includes: providing a roller including a generally
frusto-conical forming surface; and bending an inner portion of the
border flange into a position forming an acute angle relative to
the underlying portion of the panel by rolling the frusto-conical
forming surface along the inner portion of the flange.
20. The method of claim 18 in which the step of folding the border
flange includes providing a roller having a generally
frusto-conical forming surface angled to accommodate a given inner
panel thickness and to provide a desired outer panel flange fold
radius.
21. The method of claim 18 in which the step of further folding the
border flange includes: providing a roller including a generally
cylindrical forming surface; and bending the outer portion of the
border flange into position over and generally parallel to the
underlying portion of the sheet metal panel by rolling the
cylindrical forming surface along the outer portion of the flange.
Description
[0001] This is a continuation in part of U.S. Ser. No. 09/475,748
filed on Dec. 30, 1999.
TECHNICAL FIELD
[0002] This invention relates generally to the hemming of sheet
metal and more particularly, to a hemming apparatus and method for
forming a generally flat hem.
BACKGROUND OF THE INVENTION
[0003] It is well known to construct motor vehicle body panels,
doors, hoods, fenders, tailgates, trunks and deck lids by stamping
an outer sheet metal panel and separately stamping an inner sheet
metal reinforcing panel and then joining the two panels together by
hemming a flange of the periphery of the outer panel over an
adjacent edge of the inner panel to secure the panels together.
Desirably, the outer panel is slightly larger than the inner panel
to provide a border flange portion along the periphery of the outer
panel that can be folded over the peripheral edge of the inner
panel to define the hem flange that connects the two panels.
[0004] When the flange is folded over the peripheral edge of the
inner panel with a traditional hemming apparatus and method, the
resulting edge of the hemmed panels has a generally smooth, curved
or arcuate shape with a diameter of the bend equal to twice the
thickness of the outer panel plus the thickness of the inner panel.
With inner and outer panels of the same thickness, the diameter of
the bend for a standard hemming apparatus and method is equal to
three times the thickness of a sheet metal panel. While many
standard hemming methods and devices produce a smooth and fair hem
or fold line, the relatively large bend diameter of the fold line
reflects light in various directions along the curved fold line.
This creates the visual impression that the gap between adjacent
hemmed panels of the vehicle body is larger than it actually is,
that the gap is inconsistent or that the panels are not flush with
one another.
[0005] According to known hemming processes, an outer sheet metal
panel is stamped and formed to include a border flange along a
periphery of the outer panel. An inner sheet metal reinforcing
panel is formed and shaped to be slightly smaller than the outer
sheet metal panel. The inner panel is placed against the outer
panel such that a periphery of the inner panel is disposed adjacent
and generally parallel to the border flange of the outer panel. The
two panels are then secured together by hemming the border flange
of the outer panel over the adjacent periphery of the inner panel.
In more conventional hemming processes this is done by folding the
border flange over the inner panel such that the flange lies flat
against the inner panel--resulting in a relatively large flange
bend diameter. In a less-conventional process known as an "open
hem" process, the panels are secured together by folding the border
flange over the inner panel such that the flange is inclined
against the outer edge of the inner panel and an outer edge of the
flange is spaced from the inner panel. This leaves a smaller flange
bend diameter but also leaves an elongated gap between and along
the outer edge of the flange and the inner panel that foreign
material can collect in.
SUMMARY OF THE INVENTION
[0006] The invention is a sheet metal hemming apparatus for
securing two sheet metal panels together by forming a generally
flat hem along respective peripheries of the two panels. The
apparatus includes a fixture configured to receive and hold a sheet
metal panel having an upstanding border flange and a hemming tool
movably supported adjacent the fixture and configured to bend the
upstanding border flange of a sheet metal panel supported on the
fixture into a position forming an acute angle relative to an
underlying portion of the panel. The hemming tool is configured to
bend an outer portion of the flange into a position over and
generally parallel to the underlying portion of the sheet metal
panel.
[0007] The invention also includes a method for forming a generally
flat hem along respective peripheries of the two panels. According
to this method one can secure two sheet metal panels together by
forming a generally flat hem along respective peripheries of the
two panels. An outer sheet metal panel is formed to include a
generally upstanding border flange along a periphery of the outer
panel. The border flange is then folded until the flange is
inclined over an underlying portion of the outer panel. The border
flange is then further folded such that an outer portion of the
flange is disposed generally parallel to an underlying portion of
the outer panel.
[0008] Objects, features and advantages of this invention include
providing a relatively simple hemming apparatus that produces a
hemmed flange having a first portion inclined relative to a second
portion, that provides a hemmed flange with a reduced bend
diameter, that provides a fold line having a more consistent
appearance when viewed from different angles, that provides
adjacent hemmed panels on a vehicle visually appearing to have a
narrower or smaller gap between them, that eliminates the need for
a separate assembly operation to provide sealing material between
the hemmed flange and inner panel by providing a closed hem, that
is readily adaptable for use with panels having different
configurations, that is reliable, durable, of relatively simple
design and economical manufacture and assembly and that has a long,
useful service life.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other objects, features and advantages of this
invention will be apparent from the following detailed description
of the preferred embodiments and best mode, appended claims and
accompanying drawings in which:
[0010] FIG. 1 is a perspective view of an automobile having various
body panels formed from hemmed inner and outer sheet metal
panels;
[0011] FIG. 2 is a perspective view of the interior of a vehicle
door having hemmed inner and outer sheet metal panels;
[0012] FIG. 3 is a cross-sectional view taken generally along line
3-3 of FIG. 1;
[0013] FIG. 4 is an enlarged fragmentary sectional view of the
encircled portion 4 in FIG. 3;
[0014] FIG. 5 is a fragmentary sectional view illustrating a prehem
tool for initially bending the flange of the outer sheet metal
panel;
[0015] FIG. 6 is a fragmentary sectional view illustrating a final
hem tool constructed according to a first embodiment of the
invention;
[0016] FIG. 7 is an enlarged fragmentary sectional view
illustrating an alternative modified hemmed flange
configuration;
[0017] FIG. 8 is a fragmentary sectional view similar to that of
FIG. 3 but illustrating a known hemmed flange configuration;
[0018] FIG. 9 is a cross-sectional view of a second hem tool
embodiment of the invention;
[0019] FIG. 10 is an end view of a roller of the hem tool of FIG.
9; and
[0020] FIG. 11 is a cross-sectional view of a third hem tool
embodiment of the invention.
DETAILED DESCRIPTION
[0021] Referring in more detail to the drawings, FIGS. 1 and 2
illustrate a vehicle 10 having various body panels 12, doors 14, a
trunk 16 and a hood 18 wherein each may be formed from inner and
outer sheet metal panels 20, 22 connected together by a hem 24
embodying the invention. As best shown in FIGS. 3 and 4, the
various body panels 12, 14, 16, 18 of the vehicle 10 may each
comprise an outer sheet metal panel 22 that is slightly larger than
an inner sheet metal panel 20 and has a border flange 25 along the
periphery of the outer panel 22 that is folded or hemmed over the
peripheral edge 40 of the inner panel 20 to form the hem 24
connecting inner and outer panels 20, 22 together. A smooth and
fair hem outer edge 26 is required to avoid blemishes on the
finished, painted panel and to ensure a consistent gap between
adjacent panels 20, 22.
[0022] FIGS. 5 and 6 illustrate a method and a first apparatus
embodiment of the invention for forming a flat hem 24 in the outer
sheet metal panel 22 onto the inner sheet metal panel 20 to connect
the panels 20, 22 together. A second hemming method and second and
third flange hemming apparatus embodiments for producing flat
modified hems are shown in FIGS. 9-11. Reference numerals with the
subscript "a" in FIGS. 9 and 10 indicate alternative configurations
of elements that also appear in the first embodiment. Likewise,
reference numerals with the subscript "b" in FIG. 11 indicate
alternative configurations of elements that also appear in the
first or second embodiments. Unless indicated otherwise, where a
portion of the following description of the first embodiment uses a
reference numeral to refer to the figures, that portion of the
description applies equally to elements designated by the
subscripts "a" and "b" in FIGS. 9-11. Likewise, unless indicated
otherwise, where a portion of the description of the second
apparatus embodiment uses a reference numeral to refer to the
figures, that portion of the description applies equally to
elements designated by the subscript "b" in FIG. 11.
[0023] The hemming method and apparatus provide a smooth and fair
fold line defining the outer edge 26 of the outer panel 22 having a
reduced outside bend diameter 27 that is less than three times the
thickness of a sheet metal panel 20 or 22, desirably less than
about twice the thickness of a sheet metal panel 20 or 22, and
preferably generally equal to or less than the thickness of a
single sheet metal panel 20 or 22, to improve the appearance of the
outer edge 26 and of the automotive vehicle body in general. To
achieve the reduced outside bend radius or diameter 27, the hemming
apparatus and method produce a hemmed flange 24 that has an inner
portion 28 adjacent the outer edge 26 that is generally flat and
inclined relative to an outer portion 30 folded flat against the
inner sheet metal panel 20.
[0024] The improved hem 24 may be produced with a standard hemming
press using an improved hemming tool 32 (FIG. 6) with an end
forming face 33 having a first, generally planar section 34
constructed to form the outer portion 30 of the flange and a second
portion 36 inclined relative to the first section 34 to form the
inner portion 28 of the flange 24. As best shown in FIGS. 5 and 6,
to form the hem, the inner sheet metal panel 20 is disposed on the
outer sheet metal panel 22 that in turn is received on a locating
and support fixture 42 in a press. A prehem tool 44 having an
inclined forming face 46 is preferably carried by an upper platen
of a press (not shown) and is advanced toward and engages the
upstanding flange 25' of the outer sheet metal panel 22 to bend it
from an initial included angle of approximately 90 degrees to a
prehemmed acute included angle of between 25 and 75 degrees, and
preferably about 45 degrees, to form a prehemmed flange 25".
Thereafter, as shown in FIG. 6, the final hem tool 32 also carried
by an upper platen of the press, is advanced toward the prehemmed
flange 25" to bend the flange into its final, hemmed position and
form the flange 25 having an outside bend diameter 27 that is less
than three times the thickness of a sheet metal panel 20 or 22.
[0025] The final hem tool 32 has a forming face 33 with a generally
planer first section 34 constructed to form the outer portion 30 of
the flange 25 substantially flat onto the inner sheet metal panel
20 and thus provide a so called "closed hem" without any gap
between an outside edge 54 of the flange 25 and the inner panel 20.
The second section 36 of the forming face 33 is inclined at an
obtuse included angle relative to the first section 34 and is also
preferably generally planer to form the generally flat, inclined
inner portion 28 of the hemmed flange 25 immediately adjacent to
the outer edge 26 or bend in the outer sheet metal panel 22.
Desirably, the second section 36 is disposed at an included angle
of about 100 to 160 degrees relative to the first section 34 and
preferably about 135 degrees. The angle may be varied to permit the
location of the peripheral edge 40 of the inner sheet metal panel
20 to be varied relative to the outer edge 26 or hem line.
Preferably, the second section 36 of the final hem tool 32 does not
immediately overlie and is spaced outboard of the inner sheet metal
panel 20 to prevent the inner sheet metal panel 20 from being
unduly pinched by the inclined second section 36 of the hemming
tool 32 and inner portion 28 of the flange 25. Thus, as shown in
FIG. 4, the longitudinal distance "a" from the peripheral edge 40
of the inner panel 20 to the outer edge 26 of the outer panel 22 is
preferably greater than the longitudinal distance "b" from the fold
or bend 56 between the inner portion 28 of the flange 25 and the
outer portion 30 and the outer edge 26 of the outer panel 22.
[0026] A modified hem flange embodiment is illustrated at 70 in
FIG. 7. The modified hemmed flange 70 has an outer bend diameter
27' equal to about twice the thickness of the outer sheet metal
panel 22'. An inner portion 71 of the flange 70 is folded flat onto
the outer sheet metal panel 22' and an outer portion 72 of the
flange 70 is folded flat or closed on the inner sheet metal panel
20'. To prevent creasing of the flange 70 and to provide the outer
portion 72 above the inner sheet metal panel 20', a smooth or
generally arcuate transition or ramp section 74 is preferably
provided between the inner and outer portions 71, 72 of the hemmed
flange 70.
[0027] In either hemmed flange embodiment 25,70, the outer bend
diameter 27,27' at the outer edge of the flange 25, 70 is
substantially less than in the prior art, as shown in FIG. 8,
wherein the outer bend diameter 80 of an outer panel 82 is equal to
the sum of the thickness of the inner panel 82 and twice the
thickness of the outer panel 84. If the panels 82 and 84 are of
equal thickness the radius of the bend 80 is equal to three times
the thickness of either panel. Desirably, the outer bend diameter
27 may be generally equal to one or two times the thickness of the
outer sheet metal panel 22 or less. The reduced bend diameter
27,27' of the present invention provides an improved appearance of
the finished hemmed panels by themselves, and in assembly relative
to the prior art hemmed panels they appear to have a substantially
more uniform and smaller gap and a flush alignment.
[0028] As with the first method and apparatus embodiment of FIGS.
1-6, the second embodiment shown in FIGS. 9 and 10 and the third
embodiment shown in FIG. 11 are for forming a flat hem 24a, 24b in
an outer sheet metal panel 22a, 22b onto an inner sheet metal panel
20a, 20b to connect the panels 20a, 20b; 22a, 22b together.
[0029] According to the second embodiment shown in FIGS. 9 and 10,
the apparatus includes a support fixture in the form of a die ring
42a. The die ring 42a is shaped to receive and hold a sheet metal
panel, such as the outer sheet metal panel shown at 22a, having an
upstanding border flange 25a formed along at least a portion of the
panel 22a. The border flange 25a of the outer sheet metal panel 22a
is bendable to the flanged position shown in FIG. 9. The inner
sheet metal panel 20a is stacked on top of the outer sheet metal
panel 22a in a layered disposition.
[0030] A roll hemming tool 60 is movably supported adjacent the
fixture 42a and includes a forming roller 68 that engages and bends
the border flange 25a while rolling along a length of the border
flange 25a. The forming roller 68 is supported by a bearing 70 that
is, in turn, supported on a forming roller axle 72. The forming
roller 68 includes an outer circumferential forming face 62 that
actually engages the border flange 25a. The forming face 62
includes a frusto-conical first portion 64 shaped to bend the
upstanding border flange 25a of the outer sheet metal panel 22a
along a first fold line 26a of the border flange 25a into a
position forming an acute angle relative to an underlying portion
of the inner sheet metal panel 20a as shown in FIG. 9. The forming
face 62 of the hemming tool 60 forming roller 68 also has a
cylindrical second portion 66 shaped and positioned to bend an
outer portion 30a of the border flange 25a into a position over and
generally parallel to the underlying portion of the inner sheet
metal panel 20a. The second portion 66 of the forming face 62 bends
the outer portion 30a of the border flange 25a along a second fold
line 56a that is generally parallel to and spaced from the main
fold line 26a.
[0031] The apparatus may also include a pre-hem tool such as the
pre-hem tool 44 shown in FIG. 5, that pre-bends the border flange
25a to an acute included angle relative to the underlying portion
of the panel before the forming roller 68 is used to form the final
hem. When such a pre-hem tool 44 is used, it bends the border
flange 25a to a pre-hem angle of between 25 and 75 degrees relative
to the underlying portion of the panel.
[0032] Whether or not a pre-hem tool is to be employed, the forming
roller 68 is shaped such that the frusto-conical first portion 64
of the forming surface 62 is shaped to incline relative to the
cylindrical second portion 66 of the forming surface 62 at an
obtuse included angle of between 110 and 160 degrees depending on,
among other considerations, the thickness of the outer sheet metal
panel.
[0033] In fabricating the roller 68, the angle of the
frusto-conical first portion 64 of the forming surface 62 is
selected to provide a border flange angle that meets requirements
specified for an intended application. Depending on the selected
angle of the frusto-conical first portion 64 of the forming surface
62, a border flange 25a that is hemmed by the hemming tool 60 may
end up having an outer bend diameter 26a that's less than three
times the thickness of the outer sheet metal panel 22a, less than
twice the thickness of the outer sheet metal panel 22a, or that's
approximately equal to the thickness of the outer sheet metal panel
22a.
[0034] The forming roller 68 is supported in a position to hem the
border flange 25a over a peripheral edge 40a of the inner sheet
metal panel 20a as shown in FIG. 9. When the forming roller 68
engages the border flange 25a, the frusto-conical first portion 64
of the forming surface 62 of the forming roller 68 is disposed
outboard of the peripheral edge 40a of the inner panel 20a such
that the cylindrical second portion 66 of the forming surface 62 of
the forming roller 68 overlies the peripheral edge 40a of the inner
sheet metal panel 20a.
[0035] To support the forming roller 68 for rotational and
translational motion relative to the inner and outer sheet metal
panels 20a, 22a, the apparatus includes a forming roller support
arm 76. The forming roller support arm 76 may extend from any
suitable manipulating means known in the art to include a robot arm
or a roll form hemming machine. The support arm 76 and manipulating
means support the roller axle 72 in such a way as to allow the
roller 68 to be moved along a path that will cause the roller 68 to
engage and hem the outer panel border flange 25a as described above
and shown in FIGS. 9 and 10.
[0036] An inner end of the forming roller 68 includes a
radially-extending annular rim 78 configured to guide the forming
roller 68 along a periphery 79 of the fixture 42a. The
radially-extending annular rim 78 is axially biased against the
fixture 42a by a spring 86 disposed axially around the forming
roller axle 72. The spring 86 is disposed between the forming
roller 68 and a spring retainer portion 88 of the forming roller
support arm 76. The spring 86 may be a coil spring, a gas spring or
any other suitable biasing device known in the art.
[0037] According to the third flange hemming apparatus embodiment
shown in FIG. 11, a ball roller 90 is supported on a collar 92 that
is fixed to a forming roller axle 72b immediately adjacent a
forming roller 68b. The ball roller 90 serves the same purpose as
the radially extending annular rim 78 of the roller 68 in the
second flange hemming apparatus embodiment of FIGS. 9 and 10 in
that the ball roller 90 is disposed in a position to guide the
forming roller 68b along a periphery 79b of a die ring fixture 42b.
However, the ball roller 90 of the third embodiment accomplishes
this by rolling along an outer side wall 94 of the die ring fixture
42b rather than turning against the side wall 94.
[0038] In practice, the second and third apparatus embodiments may
be used to hem two sheet metal panels together by first providing
an outer sheet metal panel 22a, 22b having a generally upstanding
border flange 24a, 24b along a periphery 26a, 26b of the outer
panel 22a, 22b. An inner sheet metal reinforcing panel 20a, 20b,
that is slightly smaller than the outer panel 22a, 22b, is then
positioned against the outer sheet metal panel 22a, 22b. The inner
panel 20a, 20b is positioned against an inner surface of the outer
panel 22a, 22b such that a peripheral edge 40a, 40b of the inner
panel 20a, 20b is disposed adjacent and generally parallel to the
border flange 24a, 24b of the outer panel 22a, 22b.
[0039] The forming roller 68, 68b is fabricated so that the
frusto-conical first portion 64, 64b of its forming surface 62, 62b
is angled to accommodate the thickness of the inner panel 20a, 20b
and to provide a desired outer panel border flange fold radius. The
forming roller 68, 68b is then mounted on a support arm 76, 76b of
a robot or a roll hemming machine that is then programmed or
otherwise configured to roll the forming roller 68, 68b along the
hem. As the forming roller 68, 68b rolls along the border hem, the
frusto-conical first portion 64, 64b of the forming surface 62, 62b
of the roller 68, 68b folds the border flange 24a, 24b into its
inclined position over the underlying portion of the outer panel
22a, 22b while the cylindrical second portion 66, 66b of the
forming surface 62, 62b simultaneously folds the outer portion 30a,
30b of the border flange 24a, 24b into a position flat against the
inner surface of the inner panel 22a, 22b. This is done by rolling
the forming roller 68, 68b along the border flange 24a, 24b such
that the frusto-conical first portion 64, 64b of the forming
surface 62, 62b rolls along an inner portion 98, 98b of the border
flange 24a, 24b and the cylindrical second portion 66, 66b of the
forming surface 62, 62b rolls along the outer portion 30a, 30b of
the border flange 24a, 24b. In its inclined position the border
flange 24a, 24b forms an acute angle relative to the underlying
portion of the panel.
[0040] Alternatively, a pre-hem roller or steel 44 may be used to
fold the border flange 24a, 24b until the border flange is inclined
against the peripheral edge 40a, 40b of the inner panel 20a, 20b
such that a distal edge of the panel is spaced from the inner
surface of the inner panel 20a, 20b as shown in phantom in FIG. 5.
One of the two forming roller embodiments is then employed to
further fold the border flange 24a, 24b such that the portion of
the border flange 24a, 24b disposed generally parallel to the
underlying portion of the outer panel 22a, 22b lies flat against
the inner surface of the inner panel 20a, 20b, securing the inner
panel to the outer panel.
[0041] This description is intended to illustrate certain
embodiments of the invention rather than to limit the invention.
Therefore, it uses descriptive rather than limiting words.
Obviously, it's possible to modify this invention from what the
description teaches. Within the scope of the claims, one may
practice the invention other than as described.
* * * * *