Thermally insulated runner manifold and injection nozzle...

Details Thermally insulated runner manifold and injection nozzle... Thermally insulated runner manifold and injection nozzle...

1999-08-16

2002-07-16

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With coupling between charger and mold

C425S570000, C425SDIG002, C425SDIG002

Reexamination Certificate

active

06419476

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to pressurized fluid distribution systems, and more particularly to thermally insulated runner manifold systems and associated mold cavity injection nozzles for injection molding of plastic materials.
BACKGROUND OF THE INVENTION
Apparatus for molding of plastics, particularly injection molding, comprises dies mounted on die blocks, which blocks in turn are mounted on the platens of a press. Molten or plasticized material is forced by pressure out of a nozzle of a molding machine injection ram and through a mold tooling sprue bushing or the like which serves to transmit or conduct the plasticized material from the ram nozzle to the runners provided in a manifold plate. The plasticized material is then fed via runner outlet nozzles to the various individually associated mold cavities in the die blocks. These cavities are maintained at a temperature appropriate to cause solidification of the plastic formed in the die, a substantially different temperature than that of the manifold plate. In the case of thermoplastics, such mold cavities are maintained at a reduced temperature sufficient to cause solidification of the liquified thermoplastic material filling the cavity. In the case of a thermoset compound the die blocks are heated to an appropriate temperature to cause curing or “setting” of the plasticized material or compound in the die cavity after likewise being injection filled with such material in a liquid state. “Runnerless” manifold systems are widely used in the construction of such injection molds for producing plastics and rubber parts. These manifold systems provide a method for accepting the molding material from the injection ram of the injection molding machine and distributing this material into multiple cavities or to multiple locations within the mold to produce either multiple parts simultaneously or to fill a large part mold cavity from multiple locations. In all instances, the manifold system is designed in such a way as to permit the molding material within the manifold runner passageway system to remain in its fluid plastic or uncured state such that the material remaining resident in the manifold system may be used in the next molding cycle. In this way there is no need for wastefully leaving a solid runner attached to the molded part upon demolding. For that reason, these systems are often referred to as “runnerless” molding systems. In the context of thermoplastic molding such a system also is referred to as a “Hot Runner System”. When used in the context of thermoset plastic or rubber molding, such a system is referred to as a “Cold Runner System.”
This injection molding apparatus and technology of the prior art is described hereinafter in order to highlight the difficulty associated with heating or cooling of the plastic material while it is resident in the runner channels in order to maintain the fluidity of the resident plastic material during the period of closure of the injection gate in the injection cycle thereby enabling its use in the following molding cycle.
For example, as illustrated in
FIGS. 1
,
2
,
3
,
4
and
4
A, a “cold runner manifold system” is part of an injection mold assembly
20
used for the production of a rubber molded part
22
. Such a cold runner system is made up of a piping or channel manifold plate
24
containing multiple channels, or “runners”
26
, providing multiple flow exits through which uncured liquid rubber material flows upon being pressurefed from the outlet nozzle of an injection molding machine ram into a single manifold entrance point
28
(FIG.
1
). Mold-cavity-injection nozzles
30
(
FIGS. 3
,
4
and
4
A) are threaded into the manifold plate
24
, one at each channel or runner exit.
During the injection portion of the molding cycle, these distribution channels or runners distribute the uncured rubber evenly within the mold to a number of molding cavities
32
that are configured to produce molded rubber parts
22
. The manifold distribution system fills the cavities
22
of the mold
20
simultaneously under controlled pressure supplied by the injection molding machine injection ram. The temperature of this uncured rubber is held generally in the range of 50° C. while resident in the manifold distribution system. However, the cavity steel (upper and lower cavity plates
34
and
36
,
FIGS. 4 and 4
a
) of the mold is maintained at a much higher and constant cure temperature, typically within a general processing range of 160° C. As the mold cavities
32
are filled, the curing process begins. The system is thus referred to as a “cold runner system” because the system exists within a mold that is operating at a steel temperature in the realm of 160° C. while the manifold plate
24
and the rubber molding material within it is operating at a temperature in the realm of 50° C. The manifold plate runner system thus requires water cooling to maintain its lower temperature because the manifold plate runner system must operate in close proximity to, but at a significantly lower temperature than, the rest of the heated mold components (i.e., mold steel. In such a prior art system, referred to as a “cold runner system”, such cooling is provided by water channels
38
that extend roughly parallel to, or are in proximity to, the manifold rubber flow passages or runners
26
.
In all instances these manifold systems require nozzles
30
at the cavity end of the runner channels
26
to facilitate, control and direct the flow of the molding material into the associated part cavities
32
. These prior art nozzles
30
are conventionally formed from steel or some other high strength alloy that is highly heat conductive, and are threaded or otherwise affixed to the manifold plate
24
to bear upon mold closure on the back of the upper cavity plate
34
, thereby providing a direct channel for the molding material to flow into the individual cavities
32
. The nozzles are typically of either a conventional “flow through” or “valve gate” design.
Thus it will be seen that nozzles
30
used in these prior art manifold systems are located at the junction between the manifold system plate
24
and the part cavities
32
of the upper cavity plate
34
of the mold or tool
20
. This location is a site where a significant temperature gradient differential occurs, i.e., as indicated above the manifold plate
24
is typically at a temperature that is 70° C. to 80° C. different from the cavity plates
34
and
36
which hold or form the molded part cavities
32
.
Each nozzle
30
if not externally augmented in some way, will be influenced by temperature from the mold steel defining the part mold cavities and ultimately will achieve a temperature that will permit the fluid molding material resident in the nozzle to cure or solidify before that material is injected into the part cavities. In order to prevent this from happening, the nozzles are either heated or cooled, depending upon whether the type of injection molding application in which they are used is molding from thermoplastic or thermosetting plastic materials.
For thermoplastics molding applications, nozzles
30
are conventionally heated to roughly the same degree as the manifold system to insure that the material in the nozzle does not solidify during the cure or cooling cycle when the material in the part cavities
32
is cooled to provide the solidification necessary to produce a molded part
22
. When applied to thermoset plastics or rubber molding, the nozzles
30
are cooled to roughly the same temperature as the manifold system to insure that the semi-liquid or uncured material resident in each nozzle remains in the uncured state during the mold heating or curing phase of the molding cycle when the molding material resident in the mold cavities
32
is being heat cured to provide the solidification necessary to produce a molded part
22
.
Such heating or cooling of nozzles is necessary in prior art systems due to the thermal conductivity of the materials used in the construction of the prior art nozzles and

Affiliated with

Also associated with

Rating

Thermally insulated runner manifold and injection nozzle... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Thermally insulated runner manifold and injection nozzle..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermally insulated runner manifold and injection nozzle... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2905130