Dispensing – With heating or cooling means – Heating only
Reexamination Certificate
2001-10-15
2003-09-09
Kaufman, Joseph A. (Department: 3754)
Dispensing
With heating or cooling means
Heating only
C222S509000
Reexamination Certificate
active
06616015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to pressure molding systems, which are used, for example, to mold articles such as closures for containers. More specifically, this invention relates to improvements in pressure molding systems that increase their operating life and reliability.
2. Description of the Related Technology
Pressure molding systems typically include a source or sources of hot flowable plastic material, a number of mold cavities, and at least one distribution manifold system or “hot runner” for supplying the hot flowable plastic material to the mold cavities. This is done via nozzles under conditions of controlled pressure and temperature, and with substantially uniform flow rates, thereby creating uniform quality molded products in each of the mold cavities.
FIGS. 1 and 2
depict one commercially available pressure molding system, which is described in U.S. Pat. No. 4,588,367 to Schad. As may be seen in
FIGS. 1 and 2
, a floating manifold
11
is disposed between thermal expansion support elements
12
,
13
that are received in mating wells
14
,
16
formed in a manifold plate
17
and a backing plate
18
, respectively. A pressure molding system
19
advances plastic material under high pressure through a conduit
21
into a main manifold channel
22
and thence to nozzles,
23
and
24
, which, in turn, direct plastic into mold, cavities
26
and
27
formed in platens
28
and
29
.
As shown in
FIG. 2
, the thermal expansion element
12
includes a tubular member
32
that surrounds and is spaced from a nozzle
24
. One end of the tubular member
32
is connected to the body of the expansion element by a bridge
33
, and the other end terminates in a peripheral flange
34
, which fits within the sidewall
36
of well
14
. On the opposite side of manifold
11
, well
16
formed in abutment
18
receives a support element
13
. Element
13
, independent of a nozzle, is seated in the bottom of well
16
and its head
43
contacts one side of floating manifold
11
as does head
44
of combined nozzle
24
and thermal expansion support element
12
upon the opposite side of the manifold.
As temperature builds up during the course of machine start-up, the manifold
11
conducts heat to nozzle
24
. In addition, the nozzle
24
is heated by electric resistance heaters
50
that are supplied electricity by a plurality of electric wires. The manifold
11
tends to expand as the temperature increases and the tubular members
32
-
32
a
of support elements
12
and
13
also expand creating compressive forces to effect a seal at the interface of each nozzle and its mating manifold orifice.
As may be seen in
FIG. 3
, the nozzle
23
is disposed within a nozzle cavity
52
that is defined in the mold platen
28
. In operation, nozzle cavity
52
fills with hot flowable plastic material
58
, which is forced out of the gate
56
into the mold cavity
26
as it is displaced by additional hot flowable plastic material that is introduced from the nozzle
23
. A shut-off seal
54
is provided to seal or shut off the nozzle cavity
52
from the space in which, among other things, the electric resistance heater is disposed. Shut-off seal
54
is typically made of a metallic material, such as steel, and is sized so as to press tightly against the wall
60
defining a lower end of the nozzle cavity
52
.
Unfortunately, in practice it has been determined that the shut-off seal
54
is insufficiently effective in containing the hot flowable plastic material within the nozzle cavity
52
during operation. This may be due to a number of factors, such as damage that can occur to the seals
54
and the walls
60
during routine maintenance and mold changeovers. Regardless of the reasons, the result of leakage from the seals
54
is that plastic material ends up in unwanted areas of the manifold structure, and in particular in the area of the electric resistance heaters
50
. This has been found to disable individual heaters
50
, in particular by fouling the electrical wires, which results in the entire mold freezing up and becoming disabled.
A need exists for an improved system and method for increasing the reliability and operating life of pressure molding systems of the type that have been described above in reference to
FIGS. 1-3
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an improved system and method for increasing the reliability and operating life of pressure molding systems of the type that have been described above in reference to
FIGS. 1-3
.
In order to achieve the above and other objects of the invention, a system for pressure molding plastic material includes, according to a first aspect of the invention, a source of hot flowable plastic material; a manifold for receiving hot flowable plastic material from the source and for transporting the hot flowable plastic material; a nozzle cavity that is defined by at least one wall; a nozzle disposed within the nozzle cavity, the nozzle being operatively in communication with the manifold for receiving hot flowable plastic material therefrom; a heater for heating the nozzle, the heater being positioned outside of, but close to, the nozzle cavity and having at least one electrical supply wire; a shut-off seal positioned within the nozzle cavity to seal the nozzle with respect to the wall defining the shut-off cavity; and a secondary seal positioned between the shut-off seal and the electrical supply wire for ensuring that any hot flowable plastic material that might leak through the shut-off seal does not come into contact with the heater.
According to a second aspect of the invention, a nozzle assembly for pressure molding plastic material, includes a nozzle cavity that is defined by at least one wall; a nozzle disposed within the nozzle cavity, the nozzle being constructed and arranged to receive hot flowable plastic material from a source thereof; a heater for heating the nozzle, the heater being positioned outside of, but close to, the nozzle cavity and including an electrical supply wire; a shut-off seal positioned within the nozzle cavity to seal the nozzle with respect to the wall defining the shut-off cavity; and a secondary seal positioned between the shut-off seal and the heater for ensuring that any hot flowable plastic material that might leak through the shut-off seal does not come into contact with the electrical supply wire.
According to a third aspect of the invention, a method of retrofitting a pressure molding system of the type that includes a nozzle cavity having a nozzle disposed therein that is constructed and arranged to receive hot flowable plastic material from a source thereof, a heater for heating the nozzle that is positioned outside of, but close to, the nozzle cavity and includes an electrical supply wire, and a shut-off seal positioned within the nozzle cavity to seal the nozzle with respect to the wall defining the shut-off cavity, includes steps of gaining access to an area within the pressure molding system that is between the shut-off seal and the heater; and installing a secondary seal in the area between the shut-off seal and the heater to ensure that any hot flowable plastic material that might leak through the shut-off seal does not come into contact with the electrical supply wire.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
REFERENCES:
patent: 4588367 (1986-05-01), Schad
patent: 4592491 (1986-06-01), Chollet
patent: 4790458 (1988-12-01), Moore
patent: 5747102 (1998-05-01), Smith et al.
Crown Cork & Seal Technologies Corporation
Kaufman Joseph A.
Knoble & Yoshida LLC
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