Grommet

Details Grommet Grommet

2001-10-29

2003-10-28

Knight, Anthony (Department: 3676)

Miscellaneous hardware (e.g., bushing, carpet fastener, caster,

Bushing

C174S15200A, C174S15300A, C174S068300, C277S616000

Reexamination Certificate

active

06637070

ABSTRACT:

CROSS REFERENCE TO THE RELATED APPLICATION
The present application is based on Japanese patent application No. 2000-329477, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a grommet of the type which forms an air layer (closed space) therein to enhance a noise-insulating effect.
2. Description of the Related Arts
One known grommet of this type is disclosed in JP-A-9-289723.
FIGS. 5A
to
5
D are cross-sectional views showing the construction of the grommet, disclosed in this publication, and the process of mounting it on a panel.
This grommet G
1
, shown as the first conventional example, includes a larger-diameter tubular portion
1
, having a fitting groove (fitting portion)
2
formed in its outer peripheral surface so as to fit on a peripheral edge of a through hole Pa in the panel P, a smaller-diameter tubular portion
3
for passing a wire (wire harness) W, passing through the panel through hole Pa, therethrough, a shield wall
4
, which interconnects an axially-intermediate portion of the smaller-diameter tubular portion
3
and a distal end of the larger-diameter tubular portion
1
to close a space between the larger-diameter tubular portion land the smaller-diameter tubular portion
3
, and is elastically deformable so as to displace the smaller-diameter tubular portion
3
in the axial direction relative to the larger-diameter tubular portion
1
, an annular noise-insulating wall
5
, which is disposed closer to a proximal end
3
b
of the smaller-diameter tubular portion
3
than the shield wall
4
is, and extends radially outwardly perpendicularly from an outer peripheral surface of the smaller-diameter tubular portion
3
, and an annular engagement projection
9
formed on an inner peripheral surface of the larger-diameter tubular portion
1
at a proximal end thereof.
For using this grommet G
1
, first, the wire harness W is passed through the smaller-diameter tubular portion
1
, and then the wire W is passed through the panel through hole Pa as shown in FIG.
5
A. Then, by pulling the wire W, a distal end
3
a
of the smaller-diameter tubular portion
1
is passed through the panel through hole Pa, and the larger-diameter tubular portion
3
, connected to the shield wall
4
, is brought into engagement with the peripheral edge of the panel through hole Pa, as shown in FIG.
5
B. In this condition, when the wire W is further pulled, the shield wall
4
is stretched in the axial direction, with its inner peripheral portion pulled by the smaller-diameter tubular portion
3
, and the larger-diameter tubular portion
1
is pulled by the shield wall
4
, so that the fitting groove
2
becomes fitted on the peripheral edge of the panel through hole Pa, as shown in FIG.
5
C. At this time, the smaller-diameter tubular portion
3
is displaced forward relative to the larger-diameter tubular portion
1
because of the deformation of the shield wall
4
, and therefore an outer peripheral edge
5
a
of the noise-insulating wall
5
, formed on the outer peripheral surface of the smaller-diameter tubular portion
3
at the proximal end
3
b
thereof, is forced through the annular engagement projection
9
to enter the interior of the larger-diameter tubular portion
1
.
When the noise-insulating wall
5
thus enters the interior of the larger-diameter tubular portion
1
, with the fitting groove
2
in the larger-diameter tubular portion
1
fitted on the peripheral edge of the panel through hole Pa, the application of the pulling force to the wire W is canceled. As a result, the smaller-diameter tubular portion
3
is returned toward its original position because of the restoring action of the shield wall
4
as shown in
FIG. 5D
, and the outer peripheral edge
5
a
of the noise-insulating wall
5
is engaged with the engagement projection
9
formed on the inner peripheral surface of the larger-diameter tubular portion
1
, so that a closed space
7
, in which the air is filled, is formed between the noise-insulating wall
5
and the shield wall
4
. As a result, the noise-insulating ability of the grommet G
1
is enhanced.
The type of grommet G
2
as shown in
FIGS. 6 and 7
is also known as another conventional example.
The grommet G
2
, shown as the second conventional example, includes a larger-diameter tubular portion
11
, having a fitting groove
12
for a panel through hole, a smaller-diameter tubular portion
13
for passing a wire W therethrough, a shield wall
14
, interconnecting the larger-diameter tubular portion
11
and the smaller-diameter tubular portion
13
, and an annular noise-insulating wall
15
integrally connected at its outer peripheral edge
15
a
to an inner peripheral surface of the larger-diameter tubular portion
11
. An inner peripheral edge
15
b
of the noise-insulating wall
15
is held in intimate contact with the outer peripheral surface of the wire W passed through the smaller-diameter tubular portion
13
, thereby forming an air-filled, closed space
17
between the noise-insulating wall
15
and the shield wall
14
.
In the first conventional grommet G
1
, the annular engagement projection
9
is formed on the inner peripheral surface of the larger-diameter tubular portion
1
, and the outer peripheral edge
5
a
of the noise-insulating wall
5
, formed on and projecting from the smaller-diameter tubular portion
3
in the direction perpendicular to the axis thereof, is engaged with the engagement projection
9
, thereby forming the closed space
7
for noise-insulating purposes. However, in order that the final shape with the closed space
7
, shown in
FIG. 5D
, can be maintained, the engagement projection
9
and the noise-insulating wall
5
need to have a certain degree of rigidity. Namely, the grommet G
1
is of such a construction that the noise-insulating wall
5
is held in intimate contact with the engagement projection
9
by the restoring force of the shield wall
4
so as to maintain the noise-insulating ability, and therefore the noise-insulating wall
5
and the engagement projection
9
must be kept in the mutually-engaged condition against this restoring force.
Since the noise-insulating wall
5
and the engagement projection
9
have the increased rigidity, a large force is required in the process from the step of
FIG. 5B
to the step of
FIG. 5C
, that is, in the process of insertion of the noise-insulating wall
5
into the larger-diameter tubular portion
1
through the engagement projection
9
, and this invited a problem that the noise-insulating wall
5
could not be easily inserted into the larger-diameter tubular portion
1
.
In contrast, it may be proposed that the engagement projection
9
and the noise-insulating wall
5
are decreased in rigidity so as to reduce the inserting force. In such a case, however, the engagement projection
9
and the noise-insulating wall
5
can be easily disengaged from each other, and when this disengagement occurs, the air layer is lost, which leads to a possibility that the noise-insulating ability is not maintained.
And besides, in the final shape of
FIG. 5D
, the noise-insulating wall
5
is pressed against the engagement projection
9
(in order to positively maintain the intimate contact therebetween) by the restoring force of the shield wall
4
, and therefore the smaller-diameter tubular portion
3
is not completely returned to its initial position, and there was encountered a problem that the dimension from the fitting groove
2
to the distal end of the grommet G
1
before mounting the grommet on the panel P as shown in
FIG. 5A
was different from the dimension after mounting the grommet on the panel P as shown in FIG.
5
D. Namely, the dimension a before mounting the grommet is increased to the dimension b after mounting the grommet. As a result, the wire W can not be mounted accurately in a predetermined position.
The second conventional grommet G
2
, shown in FIGS.
6
and
7
, has no problem in so far as it is used in its original shape. However, in the

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