Molded electrical connector with a deformable elastic ridge

Details Molded electrical connector with a deformable elastic ridge Molded electrical connector with a deformable elastic ridge

1999-09-14

2001-10-30

Ortiz, Angela (Department: 1732)

Electrical connectors

With sealing element or material for cooperation with...

C428S141000, C428S066400

Reexamination Certificate

active

06309238

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to a molding process and, more specifically, both to a molded electrical connector system and to a process for molding such a system substantially without producing undesirable flash.
BACKGROUND OF THE INVENTION
Injection molding is a well-known process for molding plastic parts. One application of injection molding is the formation of electrical connectors. The newly emerging field of electrical connector products requires very tightly toleranced elastomers. As illustrated in
FIG. 1
, molded elastomers
10
used in electrical connectors are often vulcanized to a carrier frame
12
to enhance the dimensional stability of the elastomer. The elastomer mold apparatus
100
has an upper mold
20
, a lower mold
22
, and a mold cavity
24
defined between upper mold
20
and lower mold
22
and adapted to receive molded elastomer
10
and carrier frame
12
. Upper mold
20
is typically designed to locate on a datum surface
16
of carrier frame
12
to mold critical design elastomer features to the smallest tolerance possible. Datum surface
16
is located on the top of steps
14
, which are integrally formed as part of carrier frame
12
, along datum line A—A.
Upper mold
20
has partitions
26
which form the space
28
which accepts the material of elastomer
10
. The critical height dimension of elastomer
10
is controlled with to datum surface
16
. Upper mold
20
seats on datum surface
16
, without compressing datum surface
16
, to define the height of elastomer
10
. Partitions
26
must not contact carrier frame
12
when upper mold
20
contacts datum surface
16
; otherwise, undesirable deformation of carrier frame
12
might occur. Upper mold
20
cannot simultaneously contact two surfaces while still retaining sufficient control over the height of elastomer
10
. Consequently, a clearance
30
exists between partitions
26
and carrier frame
12
.
Flashing of the elastomer material may occur, at non-datum surfaces of carrier frame
12
such as the surfaces under partitions
26
of upper mold
20
, because partitions
26
do not “shut off” or locate on these non-datum surfaces to seal the flow of elastomer during the injection molding process. Clearance
30
created by the failure to seal the flow of elastomer allows protrusions
40
, known as “flash,” on the finished article which must then be removed in a separate operation. Flash
40
is difficult to remove from the finished molded part. Typically, flash
40
is removed by a labor-intensive, manual process which adds cost to the part and poses a risk of handling damage.
The problem of flash has been the subject of a number of corrective attempts. Known attempts have been directed toward changes in the design of one or more mold components. Four such attempts are summarized below.
U.S. Pat. No. 5,597,523 issued to Sakai et al. discloses a molding apparatus (
10
) and method in which a mold cavity gasket is deformed by separately applied pressure to prevent flash formation. The molding apparatus has upper and lower molds (
12
and
14
, respectively), both made of metal, and a mold cavity (
16
) defined between the molds and adapted to receive a molding material such as epoxy resin. Due to manufacturing tolerances, a clearance on the order of a few microns tends to remain between the upper and lower molds in the clamped position—particularly when the molds are unheated. If such a clearance exists, the molding material may flow out of the mold cavity and into the clearance. When this occurs, undesirable flash will result.
To avoid flash, an annular recess (
20
) is defined adjacent to the mold cavity. A gasket (
22
) is fit in the recess and made of a deformable material such as lead. The gasket may also be made of synthetic resin, plastic, or other electrically insulative organic materials. A passage (
24
) is defined in the lower mold with one end of the passage communicating with the recess and the other end connected to a pump (
26
). A pressure medium such as silicon oil (
25
) fills the passage and exerts pressure on the gasket. This pressure deforms the gasket sufficiently to form a seal around the mold cavity. Although the seal prevents flash, the molding apparatus must be modified to create a recess and a passage in the mold, to accommodate a gasket, and to incorporate a pump and oil.
U.S. Pat. No. 5,543,159 issued to Iltgen discloses a flash-proof reaction-injection-molding (RIM) mold and a method of making the mold. RIM molds, like many molds, have at least two mold segments (
14
,
16
) which, in a closed position, come together to define a mold cavity (
8
) and into which the reactants (
2
,
4
) are injected. In a mold-open position, the mold permits removal or ejection of the molded article from the mold cavity. The mold segments each have a surface (
20
,
22
) which faces the other mold segment. The surfaces have complementary shapes and come together, in the mold-closed position, along a plane known as a parting line (
12
) (thus, the parting line is analogous to the datum surface
16
of FIG.
1
).
There is usually some degree of mismatch between the mold segment surfaces. This mismatch results in the formation of small gaps between the mating surfaces at the parting line, and particularly at the edge (
24
) of the parting line which is exposed to the mold cavity. When such gaps occur at the edge of the parting line, the liquid mixture injected into the mold cavity can invade the parting line at its edge and produce protrusions (i.e., flash) on the finished article which must then be removed in a separate operation.
To address the flash problem, Iltgen provides an interlayer film (
18
′) of thermosetting resin between the mating mold surfaces. The resin fills any small gaps between those surfaces to prevent intrusion of the parting line by any liquid reactants injected into the mold cavity. The thermosetting resin adheres firmly to the surface (
20
) of one of the mold segments. Preferably, the surface of the mold segment to which the resin film adheres is roughened to provide a multiplicity of anchoring sites for the film. Again, although Iltgen addresses the problem of flash, his solution requires modification of the RIM mold to include a roughened mold surface to which a thermosetting resin adheres.
U.S. Pat. No. 4,686,073 issued to Koller discloses a mold modification similar to that of Iltgen. In his device for casting electric components on a terminal carrier plate (
4
), Koller incorporates a silicon rubber layer (
2
) which is cast on the surface of a flat, lower mold component (
1
). The silicon rubber layer is about 1 mm thick and contains recesses (
3
) which closely correspond to the dimensions of and accommodate the terminal carrier plate. A central mold component (
5
) is clamped down onto the lower mold component. The central mold component contains chambers (
7
). A ridge (
8
) surrounds the port which defines the bottom of each chamber. These chambers match the electrical components which are to be cast. An upper mold component (
9
) has openings (
10
) through which the casting resin (
11
) passes.
When the central mold component is clamped down, the silicon rubber layer is deformed by the ridges to seal the side surfaces (
12
) of the terminal carrier plate. Consequently, casting resin cannot penetrate the underside (
13
) and the side surfaces of the terminal carrier plate during casting. Although Koller does not address the problem of flash, he does propose a mold designed to prevent undesirable flow of casting resin. The mold design has a ridge and a cast-on silicon rubber layer.
U.S. Pat. No. 5,118,271 issued Baird et al. is directed to an apparatus for encapsulating a semiconductor device. The mold of the apparatus has a first cavity plate (
17
) and a second cavity plate (
13
). A semiconductor lead frame (
10
) to be encapsulated is placed between the cavity plates. The mold is closed so that the clamping surfaces (
23
) of the cavity plates clamp directly onto the lead frame. once the mold is closed, an enca

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