Electric heating – Heating devices – With heater-unit housing – casing – or support means
Reexamination Certificate
2000-05-05
2001-04-24
Hoang, Tu Ba (Department: 3742)
Electric heating
Heating devices
With heater-unit housing, casing, or support means
C219S468200, C219S544000
Reexamination Certificate
active
06222165
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tubular heating element. More particularly this invention concerns such sleeve heater that is fitted, for instance, around a nozzle of a plastic or metal extruding machine and a method making such a sleeve heater.
BACKGROUND OF THE INVENTION
In order to maintain an extruder nozzle or the like hot, a sleeve heater is used that basically comprises a tubular body in which is incorporated an electrical heating wire. Such a sleeve heater is typically slipped over the nozzle to be heated so it fits snugly therewith. When the wire is energized, the is nozzle or the like is appropriately heated. Thermostatic sensors can be built into the sleeve heater. In many situations the body being heated is not of perfectly uniform shape so the sleeve heater must be provided with cutouts or irregular formations that allow it to accommodate the contours of the body being heated. Furthermore in some situations specific regions of the body must be heated more or less than other regions, so the spacing of the turns or loops of the heating wire must be appropriately increased or decreased in the parts of the sleeve that will contact these regions.
Such a sleeve heater is typically made by winding the heating wire about a first tube and then fitting a second tube around the outside of this assembly and filling the space between them with heat-conducting potting. Fitting the heating wire to the inner tube is a tricky operation, in particular when nonuniform spacing of the turns is necessary or the wire must be guided around cutouts in the tubes. In general adapting such a system for a particular application is an extremely expensive and time-consuming chore.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved sleeve heater.
Another object is the provision of such an improved sleeve heater which overcomes the above-given disadvantages, that is which is of inexpensive and simple.
A further object is to provide an improved method of making a sleeve heater and mounting it on a body to be heated.
SUMMARY OF THE INVENTION
A sleeve heater is made by first cutting in one face of a flat metal plate a continuous groove and then fitting to the groove a heater wire with at least one end of the wire projecting past an edge of the plate. The plate is then plastically deformed with the wire to a tubular shape centered on an axis with the one face directed radially inward and axially extending edges of the sleeve angularly confronting each other. The installation on a body to be heated is completed by fitting the deformed plate over the body to be heated and tightening the plate on the body to grip it snugly.
The groove can be formed by milling and is of a depth smaller than a diameter of the wire so that same projects from the face of the plate. The path followed by the wire can be exactly tailored to the heat requirements of the body to which the heater is going to be fitted. The groove is wider at its base than at the face of the plate, typically being of dovetail shape. This ensures good contact of the wire with the body being heated and good retention of the wire in the groove.
The plate in accordance with the invention is formed of a heat-conducting metal, for instance brass, copper, or aluminum. In some situations where less heat conduction through the plate, but more directly from the wire to the body, is desired, stain-less steel can be used.
The face of the plate from which the wire projects is directed radially inward so the wire directly engages the body. The tightener can be a band that circumferentially surrounds the sleeve or fittings provided at edges of the sleeve, bridges edges of the plate. A screw or the like which can bridge the axially extending and angularly confronting edges of the split in the sleeve is turned to tighten the sleeve on the body.
In another arrangement according to the invention the plate is formed of two part-cylindrical sections connected together at a hinge. Each plate section is provided with its own such wire. Such a heater can be fitted from the side around the body it is intended to heat.
REFERENCES:
patent: 3475597 (1969-10-01), Desloge
patent: 4558210 (1985-12-01), Leary
patent: 5844210 (1998-12-01), Dowdle
patent: 5916468 (1999-06-01), Akiyama et al.
patent: 6054691 (2000-04-01), McGwire
Dubno Herbert
Hoang Tu Ba
Hotset Heizpatronen U. Zubehor GmbH
Wilford Andrew
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