Spring devices – Resilient shock or vibration absorber – Nonmetallic – resilient element
Reexamination Certificate
2001-05-14
2003-06-10
Graham, Matthew C. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Nonmetallic, resilient element
C267S141300
Reexamination Certificate
active
06575440
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for mounting a bushing into a sheet metal member and also to a sheet metal member and bushing assembly. The present invention more particularly relates to a vehicle frame member and a method for making the same with a shock absorbing mounting portion.
BACKGROUND OF THE RELATED ART
One method of installing a bushing into a sheet metal member, such as a hydroformed tubular member, requires piercing or blanking a hole in a portion of the sheet metal member. The sheet metal member is then passed on to a secondary operation where the edge portion surrounding the pierced or blanked hole is extruded or drawformed to form an annular flange portion. A steel bushing is forced into the opening so as to form an interference fit between the annular flange portion and the bushing. A tight tolerance is required between the extruded drawformed annular flange portion and the bushing to provide the appropriate interference fit.
FIGS. 1A-3B
illustrate conventional methods of installing a bushing in a hydroformed motor vehicle frame member.
FIGS. 1A and 1B
illustrate a punch
11
fastened to an upper moving ram of a reciprocating press, and an extrusion die
12
fixed to a lower stationary press bed. A tubular metal frame member which has been hydroformed from a seam-welded piece of sheet metal is partially shown and indicated at
100
.
The extrusion die
12
is inserted in an open end of the hydroformed tubular member
100
and then lifted upwards to support the underside of an upper wall
10
of the member
100
. The press ram then begins its downward stroke to force the punch
11
into contact with the metal material of the upper wall
10
, as shown in FIG.
1
A. When the press tonnage overcomes the tensile strength of the metal wall
10
, the punch
11
shears the metal wall
10
against an opening
13
in die
12
. The die opening
13
is defined at its upper end by a “hard” or 90° corner
35
.
The scrap material or slug
15
passes through the die opening
13
and is eventually discarded, leaving hole
14
in the upper wall
10
of the tubular member
100
. The diameter of the hole
14
corresponds to the outer diameter of punch
11
. As shown in
FIG. 1B
, the press ram then starts its upward movement back to its starting position to move punch
11
away from the tubular member
100
, and the tubular member
100
is then removed from the extrusion die
12
. As a result of this hole forming operation, the edge portion surrounding the hole
14
will have a sharp, burred corner.
As shown in
FIGS. 2A and 2B
, after hole
14
is formed, the tubular member
100
is then moved to a drawforming station. At the drawforming station, a second die
20
is positioned inside the tubular member
100
and a press ram with a drawforming punch
16
is then cycled through a downstroke to locate a punch pilot
17
in alignment with the hole
14
. The press ram then continues its downstroke to force a forming portion of the punch into engagement with the inner edge portion surrounding the hole
14
. As shown in
FIG. 2A
, the press ram lowers the punch
16
lowers to a preset depth, so that the forming portion thereof draws the inner edge portion downwardly against a beveled upper edge
36
of the second die
20
, thereby forming an annular drawformed flange portion
18
. The press then begins its upstroke and removes upper punch
16
and punch pilot
17
from the tubular member
100
. This causes the sharp, burred corner of annular flange portion
18
to be burnished smooth. As indicated by the arrow in
FIG. 2B
, the die
20
is then pulled out from the open end of the tubular frame member
100
.
FIGS. 3A and 3B
illustrate a steel can bushing
23
which has been pre-assembled in a separate operation from the punching operation. The tubular member
100
is placed in a holding fixture (not shown) that supports the underside of upper wall
10
close to the inner edge
25
of drawn flange
18
. The bushing
23
is located directly above the hole
14
either manually or via the use of a machine. Downward pressure is applied to top surface
26
of the bushing
23
to force the busing through the hole
14
in the direction indicated by arrow
24
. The pressure is then released and the finished assembly shown in
FIG. 3B
is produced with the bushing
23
being retained through an interference fit relation with the annular drawformed flange portion
18
.
The problem with the above-described conventional method is that the fit between the exterior surface of the steel can bushing
23
and the annular drawformed flange portion
18
must be kept tight to ensure that the bushing
23
does not become separated from the tubular member
100
. However, the fit must not be so tight that an extraordinarily high amount of effort is required to force the bushing
23
into the hole
14
. Also, removal of the drawforming punch
16
burnishes the inner corner of the flange portion
18
which engages the bushing
23
. As a result of this burnishing, the corner is smoother and does not “bite” into the bushing exterior to resist removal of the bushing.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a sheet metal member with a bushing securely mounted therein which does not suffer the shortcomings of the construction described above. Specifically, it is an object of the present invention to ensure that the interference fit between the bushing and the sheet metal member is sufficient to prevent separation of the bushing from the member during normal vehicle operation. To achieve this object, one aspect of the present invention provides a method for mounting a bushing into a metal member which comprises providing a metal member forming a bushing receiving opening in the metal member, the opening defined by an annular edge portion surrounding the opening. A bushing is then forced through the opening in a bushing driving direction such that the bushing engages the annular edge portion and deforms the annular edge portion in the bushing driving direction to form an annular flange portion on the metal member which projects in the driving direction and engages an exterior surface of the bushing in an interference fit relation so as to securely retain the bushing within the opening.
In the method of the present invention, the need for a separate drawforming step, as in the above-described conventional method, is eliminated. The bushing itself acts as the drawforming tool as it is forced into the opening in the tubular member. Because the bushing acts as the drawforming tool, a tight interference fit between the annular wall portion and the bushing is ensured. Thus, the method of the present invention not only ensures a secure fit between the bushing and the tubular member, the method of the present invention also eliminates some of the tooling and operational steps of the conventional method.
Further, the corner of annular wall portion will not be burnished smooth because the drawforming tool (i.e., the bushing) is not withdrawn during the operation. An unburnished, burred, sharp corner is preferred because the sharp corner tends to “bite” into the exterior of the bushing when force is applied to the bushing in a direction opposite to the direction in which it was forced through the opening. Specifically, the annular flange portion will be drawn inwardly against the bushing as a result of such a force being applied to the bushing due to the sharp, burred corner being engaged with the bushing exterior.
This aspect of the present invention is more particularly related to a method for making a vehicle frame member with a shock absorbing mounting structure to be mounted to another structural component of a motor vehicle. The method comprises providing a tubular member surrounding a hollow interior and a lateral opening formed through the member. The member has an annular edge portion surrounding the opening. A shock absorbing mounting structure has a mounting portion constructed and arranged to be secured to the structural component of t
Graham Matthew C.
Magna International Inc.
Pillsbury & Winthrop LLP
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