Coating apparatus – Solid member or material acting on coating after application – Running length work
Reexamination Certificate
2003-05-14
2004-11-09
Lamb, Brenda A. (Department: 1734)
Coating apparatus
Solid member or material acting on coating after application
Running length work
C118S420000
Reexamination Certificate
active
06814803
ABSTRACT:
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, in a prior art micro-extruder crosshead assembly
10
for producing a wire coated with extruded insulation, a wedge ring
12
is seated in a crosshead aperture
13
of a crosshead body
14
. The wedge ring
12
, itself defines a central aperture
16
, through which extends a die tip
18
that is anchored inside crosshead body
14
. A die
20
having a central aperture
22
, abuts wedge ring
12
and accommodates the forward end of the die tip
18
.
In operation, wire is drawn, in a forward direction
24
, through die tip
18
as pressurized extrudate (typically a molten polymer) is forced through wedge ring aperture
16
and into die aperture
22
so that it congeals about the wire. The pressure of the extrudate pushes against wedge ring
12
in forward direction
24
, forcing it against die
20
to form a good seal. By using a wedge ring
12
, misalignments between die
20
and wedge ring
12
can be forgiven, because wedge ring
18
can change its orientation slightly so that it seats against die
20
in a close to optimum manner.
Unfortunately, however, as efforts have been made to coat wires having a diameter in the range of 25 microns with a coating of extrudate having a thickness on the order of from 25-50 microns, problems have been encountered because gels form within the crosshead body
14
and cause a degradation of the process. Because of this gel formation, an extruder could not be kept in operation for more than about 10-20 minutes without a deterioration of the finished product occurring. After running the extruder for a number of minutes, pinholes begin to appear in the finished product coated wire.
SUMMARY
The present invention is a micro-extruder, comprising a funnel-shaped tip piece defining a front aperture, through which wire is drawn, and a front rim, around which extrudate flows, and which has an outer diameter of less than 3.8 mm (150 mils). In addition, a structurally unitary cross-head body has a front aperture and a protruding rim about this front aperture. The funnel shaped tip piece protrudes through the front aperture. Also, a die having a surface that defines an aperture is adapted and positioned to abut the protruding rim and to form a seal against the protruding rim, so that no extrudate may leak out between the surface defining an aperture and the protruding rim.
The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3635621 (1972-01-01), Miyauchi et al.
patent: 4605525 (1986-08-01), Baxter
patent: 4710114 (1987-12-01), Garner
patent: 5431867 (1995-07-01), Matsushita et al.
patent: 5458830 (1995-10-01), Shin et al.
patent: 5498145 (1996-03-01), Sikora et al.
patent: 5795531 (1998-08-01), Salzmann et al.
patent: 2002/0158357 (2002-10-01), Swanson et al.
Rauwendaal, Chris, Polymer Extrusion, 1994, pp. 68-79,102-107, 310-315.
Frados, Joel, Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., fourth edition (1991), pp. 188-191.
Advanced Neuromodulation Systems, Inc.
Lamb Brenda A.
Law Office of Timothy E. Siegel
Siegel Timothy E.
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