Universally mounted adjustable die

Details Universally mounted adjustable die Universally mounted adjustable die

1998-11-10

2002-05-07

Nguyen, Nam (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Distinct means to feed, support or manipulate preform stock...

Extrusion shaping means

C425S381000, C425S466000

Reexamination Certificate

active

06382944

ABSTRACT:

BACKGROUND OF THE INVENTION
Extrusion dies are frequently used to provide a tubular coating to a wire or other product which provides a generally cylindrical substrate. A typical die assembly
101
for performing this function is shown in FIG.
1
. The basic assembly
101
consists of a die body
102
, a tip
103
, a die holder
104
, and a die
105
held in place by end caps
106
and
114
. The tip
103
is mounted within an axial bore of the die body
101
and is itself constructed with an axial bore
107
having a downstream exit portion
108
. In operation, a wire or other tubular product
116
is fed through bores
107
and
108
to exit axially at
115
. An annular extrusion passage
109
, surrounds exit
115
, and is positioned to receive flowing plastic and apply it, in a tubular layer, to the product
116
at exit
115
.
The die assembly
101
is an assembly of machined parts, each having its own manufacturing tolerance. These tolerances tend to multiply with the assembly of the components. It is therefore a difficult task to maintain the desired coaxial relationship between the product and the extruded layer. An adjustment mechanism is generally needed to insure concentricity of the die and pin so as to provide an even thickness of the applied layer. This is generally accomplished simply by mounting the die holder
104
for adjustment, along x and y coordinates. The adjustment may be actuated through adjusting screws
112
. As shown in
FIG. 1
, the adjustment motion of the prior art is radially towards and away from the axis
117
, of the assembly
101
as a torque is applied to an adjustment screw
112
. This may require a significant adjustment torque because of the high thrust loads on the die holder during operation.
SUMMARY OF THE INVENTION
The die assembly of this invention may be generally described as a cross head die in that it receives molten plastic from an extruder which enters the die passages in a direction that is transverse to the longitudinal axis of the assembly. The plastic must then be turned to flow downstream axially towards an annular tapered extrusion channel. The extrusion channel surrounds an axially extending passage through which a wire or tubular product may be directed to receive a cylindrical layer from the extrusion passage. In order to apply a cylindrical layer of constant radial depth, the position of the die relative to the tip must be precise. Since the degree of positioning accuracy cannot be maintained during assembly of the components, an adjustment mechanism is provided which allows the relative position of die and tip to be adjusted after assembly.
The die body of this invention is constructed with a recess at its downstream end to receive the die holder which supports the die in a fixed relation. The die holder and die body recess engage to allow a pivot motion between the two components. To accomplish the pivot motion, the recess is constructed with a spherical internal surface which mates with a spherical external surface constructed on the die holder. These surfaces engage and operationally cooperate to allow the die holder to pivot in a substantially universal motion. To actuate the adjustment, adjusting screws are provided in the die body which engage the die holder at a position axially displaced from the spherically engaged surfaces of the die body and die holder. This provides a mechanical advantage proportional to the distance that the adjustment screws are displaced from the fulcrum formed by the spherical surfaces and results in a reduction of the torque which must be exerted on the adjustment screws to correct the relative position of the die and tip. In this manner the die and tip may be accurately maintained in a concentric relation.


REFERENCES:
patent: 4472129 (1984-09-01), Siard
patent: 5286183 (1994-02-01), Tonsi et al.
patent: 5346384 (1994-09-01), Hegler et al.
patent: 5690971 (1997-11-01), Buluschek
patent: 635727 (1962-01-01), None
patent: 168915 (1921-07-01), None

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