Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Plural sequential shaping or molding steps on same workpiece
Reexamination Certificate
1998-07-15
2001-01-09
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Plural sequential shaping or molding steps on same workpiece
C264S161000, C264S296000, C264S318000, C264S328100, C264S328160, C264S334000, C425S438000, C425S547000, C425S556000, C425S577000, C425SDIG002, C249S063000
Reexamination Certificate
active
06171539
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a method for molding axially hollow grommets as well as a device and mold for use therein.
2. Description of Prior Art
In the automotive industry, a grommet is used to seal a hole in a panel through which a wire harness has passed. Generally it is molded from an elastomeric material and the wire harness is passed through the grommet prior to insertion. Since the grommet is made of an elastomer, it is able to deform and fill the hole through which the wire harness passes and provide both soundproofing and waterproofing. Typically, the panel is a firewall and thus the soundproofing and waterproofing aspect is between the engine compartment and the passenger compartment.
Conventionally, grommets have been molded in a funnel design, wherein the large end has a stopping flange which interacted with the panel so as to fill the hole. The small end fits tightly around the bundle of wires in the wire harness so as to form a secure seal.
An improved design for a grommet has been suggested in Japanese Application Number 61-112732, filed Jul. 24, 1986. In this Application, the grommet, as removed from the mold, is shown in FIG.
1
. Grommet
15
comprises hollow
30
, body
24
, long tube funnel section
31
and short tube funnel section
32
. Funnel sections
31
and
32
have long tube portions and short tube portions which have been marked
33
and
34
, respectively. Annular depression
35
is molded into body
24
of grommet
15
. Also, reinforcement
38
is molded into end
17
of long tube portion
33
.
FIGS. 2 and 3
illustrate the use of grommet
15
with wire harness W/H to fill a hole in panel P. As shown therein, the user of grommet
15
must invert long tube funnel section
31
into short tube funnel section
32
so that long tube portion
33
doubles within short tube portion
34
, thus forming double walled portion
36
. Wire harness W/H is then inserted through grommet
15
and tape
39
is secured around the end of double walled portion
36
. Because of cavities
37
, body
24
is able to deform as shown in
FIGS. 2 and 3
, so that grommet
15
can be easily inserted into the hole in panel P. The arrows in
FIG. 2
illustrate the flexing action of the elastomeric material used to mold grommet
15
. It is preferred that sealant
40
be injected around the wire harness so as to increase the waterproofing and soundproofing ability of the grommet.
one of the problems with grommet
15
is that the operator, when mounting the grommet on the wire harness, has a difficult time inverting long tube funnel section
31
into short tube funnel section
32
.
It is well known to mold thermoplastic resin or rubber materials about a mandrel within the cavity of a split mold into a hollow article having an axial opening therethrough. However, there is no prior art device that could remove the object from the mandrel after molding and, at the same time, insert long tube funnel section
31
into short tube funnel section
32
. It is an object of the present Invention to provide apparatus which is capable of being utilized rapidly and reliably.
SUMMARY OF THE INVENTION
Applicant has now discovered a method for forming a grommet of the type where the grommet has a body, an axial hollow therein, a peripheral channel in the body, a short tube funnel section at one end, and a long tube funnel section at the other end. The long tube funnel section is inverted into the short tube funnel section to form a double walled portion. The molding process entails the formation of a double walled portion of the grommet by using the core in the molding apparatus to reverse the long tube funnel section into the short tube funnel section.
Broadly, the grommet in accordance with the present invention comprises: a body, a long tube funnel section on one side of the body, and a short tube funnel section on the other side of the body. The molding space is defined by a core and an external multi-part mold structure, which structure has a middle plate.
The method comprises
(a) molding the grommet in a closed mold so that the middle plate, which is part of the multi-part structure, is in contact with the body of the grommet when the mold is closed;
(b) opening the mold, leaving the core and the middle plate in contact with the grommet;
(c) moving the core through the grommet so that the long tube funnel section is inverted into the short tube section, thereby forming the double walled portion; and
(d) releasing the grommet from contact with the middle plate and the core.
The novel mold of the present invention has L-shaped protrusions at one end of the core and corresponding depressions in the external multi-part mold structure. The method of the present Invention avoids the problem of the operator having to invert the long tube funnel section into the short tube funnel section, and the grommet can be employed as produced without further manipulation.
The device for carrying out the method comprises a fixed mold, a movable mold, and a middle plate between the two molds. The movable mold is adapted for movement among a closed position, wherein the fixed mold and the movable mold are adjacent each other with the middle plate between them; an intermediate position, wherein the movable mold and the middle plate are spaced apart from the fixed mold; and an open position, wherein the movable mold is spaced further apart from the fixed mold than the middle plate. The plane of the middle plate is preferably perpendicular to the movement of the movable mold.
There is a core affixed to the movable mold and the core, the fixed mold, and the movable mold define a molding space for the grommet when they are in the closed position. In this position, an edge of the middle plate projects into the molding space so that, when moldable material is injected into the space and solidifies, the peripheral channel is formed with the edge therein.
The core has, on its mold end remote from the middle plate, a retaining element which, when the movable mold is moved from the intermediate position to the open position, carries the adjacent neck of the grommet into the axial hollow. To effectuate this, the edge in the channel prevents the body from moving toward the open position.
In a preferred form of the device, the movable mold is mounted slidably on at least one guide pin which extends parallel to the direction of movement of the movable mold. The proximal end of the guide pin is mounted on the fixed mold and the distal end is remote therefrom. It has been found advantageous to provide two guide pins which are spaced apart in a direction perpendicular to the movement.
The guide pin also carries a stop member for the middle plate adjacent the distal end. Thus, when the movable mold moves from the intermediate position to the open position, the middle plate is retained in the intermediate position. If the moldable material so requires, a heating device can be provided adjacent the molding space to cure or otherwise set the moldable material.
The operation of the device comprises introduction of the moldable material through a sprue and a gate into the molding space while the various elements are in the closed position. This is followed by movement of the movable mold to the intermediate position, whereby the grommet is disengaged from the fixed mold. At this point, the moldable material formed by the sprue and the gate is attached to the grommet.
The movable mold is then further moved to the open position, but the middle plate remains in its intermediate position due to the stop members on the distal ends of the guide pins. The retaining element on the mold end of the core remote from the middle plate engages the adjacent end of the grommet. The edge of the middle plate being in the intermediate position, retains the body of the grommet in that position so that, as the core is withdrawn, the retaining element pulls the end of the grommet into the axial hollow. Thereafter, the grommet is removed from the middle plate and the sprue and gate are removed.
In a modification
Bierman, Muserlian and Lucas
Poe Michael I.
Silbaugh Jan H.
Sumitomo Wiring Systems Ltd.
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