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Browse Prior Art Database

Valve Gate Actuation Method and Apparatus

IP.com Disclosure Number: IPCOM000008031D
Publication Date: 2002-May-13
Document File: 15 page(s) / 82K

Publishing Venue

The IP.com Prior Art Database

Abstract

In an injection molding machine, a valve gate actuation method and apparatus is provided for use in the flow control of molten material to a mold cavity. The valve gate actuation method comprise a flexible bladder operatively attached at one to an elongated valve stem. The valve stem extends from the bladder to a gate area of an injection nozzle. Communication of a pressurized fluid to the flexible bladder provides the motive force to selectably open and close the nozzle gate.

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Background of the Invention

Field of the Invention

       This invention relates to hot runner valves, and more
particularly, to hot runner valves gates which are activated to
an open, closed or multi-position using an elongated bladder
assembly.

Summary of the Prior Art

       Hot runner systems can be categorized into two types
with respect to the method of closing off the mold cavity
injection gate. These types include a thermally closed gate and
a mechanically closed gate. This invention relates to mechanical
or valve gate closing mechanisms for use in single or multi-
cavity molds and molding systems as well as single cavity molds.
Typically, a valve gated actuating mechanism is a unitized
device which is attached to a valve stem or other commonly known
gate closing component. Accordingly, valve stem actuation
devices typically consume a considerable amount of space within
a mold platen. As a result of such large space consumption,
molds are formed which are too large for typical injection
molding machine, resulting in increased expense due to the
necessity to use larger and more materials for producing a
larger mold to accommodate the mechanism.

       Such a scenario typically arises when a valve gated
hot runner system is desired for a single, multi-level or stack
mold. Most valve gated actuation mechanisms assume a large
space which would be better used for an opposing injection
nozzle housing arrangement or in cases where nozzles are closely

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spaced together. Such is the case for typical mechanically
actuated closed gate mechanisms and a typical thermally
activated closed gate mechanisms. In comparing two such
mechanisms, it is obvious that the mechanically closed gate is
generally significantly larger than the thermally closed gate.
Accordingly, it would be beneficial in the art to design a
mechanically actuated closed gate system of a size comparable to
thermally closed gate systems.

       U.S. Pat. No. 5,894,025 to Lee et al., shows a nozzle
suitable for attachment to the hot runner of an injection
molding machine. The actuating mechanism used to move the valve
stem in reciprocating fashion is shown as an annular piston,
where a pressurized fluid is employed as the motive force. As
with all piston type actuators, it is necessary to provide
resilient seals which serve to prevent pressure leak from the
pressurized chambers on both sides of piston, so that maximum
force is transferred to the piston. Additionally, pressurized
fluid leakage can lead to, wasting energy or fluid substance;
creating undesirable noise; fire hazards; and undesirable
cooling effects on the hot melt conveying components adjacent to
it. The resilient seals for this nozzle design must be of a very
high temperature capability.

       U.S. Pat. No. 4,082,226 shows a typical valve gate
actuating mechanism. An annular piston of complex and bulky
design is used, which includes many parts requiring high
manufacturing expense and laborious assembly time. By necessity,
the p...