Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
1996-09-04
2001-06-26
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C425SDIG001, C425SDIG002, C425SDIG002
Reexamination Certificate
active
06250911
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to heater usable in an injection-molding mold.
BACKGROUND OF THE INVENTION
A standard heater for an injection-molding mold has a normally cylindrical casing made of metal and coaxially receiving an electrical resistance-type heater wire normally shaped as a helix. A mass of electrically insulating but thermally conductive potting surrounds the heater wire and fills the interior of the casing. Terminals at one or both ends of the casing connect to the ends of the resistance wire.
Such a heater is seated in a groove in the mold and an electrical current is passed through its heater element to heat it and the mold. When the element burns out, which is inevitable, the old heater is pried out and a new one is fitted to the groove, normally being potted in place with heat-conductive material or grout and/or being clamped down in the groove.
It is fairly common for the groove to be nonstraight. Thus the heater must be bent to the necessary nonstraight shape. Since the casing is normally made of a high-alloy steel, this bending must take place in a shop and be carried out to high tolerances in order to ensure a good fit of the heater in the groove. Obviously this bending/fitting operation is expensive and considerably raises the cost of replacing the heaters in a mold plate. Moreover the refitting operation can be delayed as the appropriately bent heaters are made up.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide an improved heater for an injection-molding mold.
Another object is to provide such a heater which can be installed in a simple low-cost manner.
A further object is the provision of a heater assembly for a mold which offers superior heat exchange and where the heater can easily be replaced.
SUMMARY OF THE INVENTION
These objects are achieved according to the invention in a heater having, as is known, an elongated tubular casing, an electrical heating element extending longitudinally inside the casing, and a mass of electrically insulating potting filling the casing around the element. According to the invention the casing is made of a ductile metal and is deformable by hand, and the electrical heating element and potting mass are also easily deformed by hand.
Thus according to this invention the heater can be bent by hand to fit the mold plate. The potting, which is relatively incompressible but flexible, allows the casing and element to bend without substantial change in the cross-sectional shape of the heater. The refitter need merely have a heater of the right length and diameter, and he can bend it at the site to fit the mold. This greatly simplifies the installation.
According to this invention the metal contains copper. It can also be nickel.
In another arrangement corresponding generally to that of German Utility Model 92 17 183.4 the casing is annularly corrugated and formed by a succession of like U-section rings each having a pair of parallel legs and a bight portion interconnecting the respective legs and a succession of like rounded annular webs interconnecting the rings and each joining a leg of one respective ring with a leg of an adjacent respective ring. Each leg and each bight portion has a respective width and the transverse widths are all generally the same. Such a heater can be bent readily but will maintain its cross-sectional shape very well.
According to more specific features of this embodiment of the invention the casing has a transverse width that is about five times as great as the width of the legs. Furthermore, each web has a longitudinal width equal to between one-fifth and one-seventh the width of the legs.
It is possible for the casing according to the invention to be of generally rectangular section with rounded longitudinally extending corners. Such a heater fits in a steel plate formed with a nonstraight groove of a section complementary to a section of the casing. The section of the groove is generally rectangular and has a plurality of flat sides and the plate has a face surface parallel to at least one of the sides.
REFERENCES:
patent: Re. 30126 (1979-10-01), Churchill
patent: 1667857 (1928-05-01), Harpster et al.
patent: 4197449 (1980-04-01), Fessenden
patent: 4263577 (1981-04-01), Bauchert et al.
patent: 4300038 (1981-11-01), Schwarzkopf
patent: 4575619 (1986-03-01), Porzky
patent: 4593182 (1986-06-01), Schwarzkopf
patent: 4642043 (1987-02-01), Schwarzkopf
patent: 5247158 (1993-09-01), Steinhauser et al.
patent: 9217834 (1993-04-01), None
Dubno Herbert
Heitbrink Tim
Hotset Heizpatronen u. Zubehohr GmbH
Wilford Andrew
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