Leg manifold mounting arrangement

Details Leg manifold mounting arrangement Leg manifold mounting arrangement

2002-12-09

2004-12-21

Heitbrink, Jill L. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

C425S572000, C425S588000

Reexamination Certificate

active

06833102

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to moulding apparatus for the injection moulding of plastics. More particularly, this invention relates to the mounting of a “leg manifold” in a multi-level stack moulding arrangement.
BACKGROUND OF THE INVENTION
In designing multi-level, multi-cavity stack moulds, such as 2, 3 or 4 level moulds, consideration must be given to maintaining balanced melt flow. It is often ideal to originate melt flow from a central axis of the mould for each level. This may require a melt flow path which originates at the mould axis, extends radially outwardly through a “leg manifold” to the edge of the mould, crosses a “level” through a crossover nozzle and returns radially inwardly back to the central axis through a further leg manifold displaced longitudinally along the mould axis from the first leg manifold. The number of leg manifolds will depend on the number of mould levels. Typical arrangements where radially inward and outward melt flow paths are present are illustrated in U.S. Pat. No. 5,846,472 (three level) and U.S. Pat. No. 5,458,843 (two and four level).
As injection moulding apparatus are principally made of metal which expands significantly between room temperature and its operating temperature, provision has to be made to accommodate thermal growth/contraction of the leg manifold by amounts on the order of 0.125 inches (approximately 3.3 mm). FIG.
1
schematically illustrates a typical axial cross-section through a “prior art” mounting arrangement. A leg manifold
10
is illustrated as providing a fluid conduit between a sprue bushing
12
located on the central axis
14
of the mould and a crossover nozzle housing
16
disposed generally parallel to but radially outwardly of the central axis
14
of the mould. The leg manifold
10
is located on the central axis
14
by a means such as a first manifold insulator
18
having a first locating spigot
20
which engages a socket
22
in the leg manifold
10
across from the sprue bushing
12
.
In theory at least, the leg manifold
10
will expand radially outwardly from the mould axis
14
. The end of the leg manifold adjacent the crossover nozzle housing
16
is clamped between the crossover nozzle housing
16
and a second manifold insulator
24
. The second manifold insulator
24
has a second locating spigot
26
. The second locating spigot
26
, is received in a slot
28
in an injection plate
30
against which it presses. While, it is intended that longitudinal movement should be accommodated by movement of the second spigot
26
in the slot
28
and sliding movement between the leg manifold
10
and the crossover nozzle housing
16
, often this doesn't occur. Instead the first locating spigot
20
ends up being sheared off in turn pressing the leg manifold
10
toward the sprue bushing
12
and misaligning the sprue bushing
12
in its locator ring
30
.
A further disadvantage to the prior art design is that there is no clamping force applied to the sprue bushing end of the leg manifold
10
. When “sprue break” occurs in the injection moulding cycle during which the injection machine nozzle is disengaged from the sprue bushing
12
. The sprue bushing is slidably received in a locating ring
32
and therefore doesn't “clamp” the leg manifold
10
against the first manifold insulator
18
. Repeated engagement and disengagement of the injection machine nozzle and sprue bushing
12
has a “hammering” effect on the leg manifold
10
which eventually causes curvature of the leg manifold away from the sprue bushing.
It is an object of the present invention to provide a mounting arrangement for a leg manifold which better accommodates thermal growth and shrinkage than the above described arrangement.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, a manifold mounting arrangement is provided wherein a leg manifold is fixedly secured at a central location along its length rather than at its sprue bushing and whereby thermally induced length changes are accommodated outwardly from this central location. Additionally, a first end of the leg manifold is clampingly secured between a sprue housing and a manifold insulator to avoid movement of the first end toward the sprue upon a sprue break portion of the injection moulding cycle.
More specifically, a manifold mounting arrangement for a leg manifold of an injection moulding apparatus is provided. The manifold mounting arrangement includes an injection plate, a manifold plate secured to the injection plate and a cavity defined between the manifold plate and the injection plate. The leg manifold, which has first and second opposite ends, is disposed in the cavity. The first end of the leg manifold is located by a first manifold insulator extending between the first end and the manifold plate and by a sprue housing having a flange extending between the leg manifold and the injection plate. The second end of the leg manifold is located by a second manifold insulator extending between the second end and the injection plate and by a crossover nozzle housing having a flange extending between the leg manifold and the manifold plate. The leg manifold has a melt passage extending through it which fluidly communicates at the first end with a sprue passage extending through the sprue housing and at the second end with a crossover nozzle passage extending through the crossover nozzle housing. The leg manifold is further supported along its length between central manifold insulators which extend between the leg manifold and the injection plate and between the leg manifold and the manifold plate. The first and second manifold insulators are positioned to allow longitudinal movement of the first and second ends of the leg manifold relative respectively to the sprue housing and the crossover nozzle housing in response to thermal expansion and contraction of the leg manifold. The central manifold insulators constrain the leg manifold from longitudinal movement to limit such movement to the first and second ends.
The central manifold insulators may be secured by respective securing means extending into the injection and manifold plates and at least some of the central manifold insulators may be provided with projections or recesses which engage corresponding projections or recesses in the like manifold to constrain its longitudinal movement.
The securing means may include a socket extending into the manifold plate and a socket extending into the injection plate for respectively receiving the second and the first manifold insulators.
The securing means may alternatively be threaded fasteners. In a preferred embodiment, the central manifold insulators are disposed about midway along the length of the leg manifold so that normal movement is divided approximately equally between the first and second ends relatively respectively to the sprue housing and the crossover nozzle housing.


REFERENCES:
patent: 3812228 (1974-05-01), Skoroszewski
patent: 4586887 (1986-05-01), Gellert
patent: 4588367 (1986-05-01), Schad
patent: 5044927 (1991-09-01), DiSimone et al.
patent: 5220154 (1993-06-01), Gunther
patent: 5540580 (1996-07-01), Takada
patent: 5705202 (1998-01-01), Gellert
patent: 5846472 (1998-12-01), Rozema et al.
patent: 6561790 (2003-05-01), Blais et al.
patent: 6669462 (2003-12-01), Jenko

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