Electric heating – Metal heating – Of cylinders
Patent
1986-09-15
1989-09-26
Paschall, M.
Electric heating
Metal heating
Of cylinders
219 10491, 219 1057, 116208, H05B 610
Patent
active
048702390
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention is concerned with an apparatus for heating, more particularly the invention concerns the heating of drums and their contents.
BACKGROUND OF THE INVENTION
Many industrial and chemical products have a high viscosity at low temperatures, and it is therefore often difficult to handle quantities of such products contained in drums under cold or cool conditions. Furthermore, it is common to store the above-mentioned products outside of manufacturing plant, and although the interior of the plant may be at a temperature sufficient to lower the viscosity of the product, the rate of heat transfer into the drum or other container may be insufficient to warm the contents quickly if the product is needed urgently.
As a consequence, various means for heating drums have been suggested.
In the known prior art, drums and other such containers have been heated by steam coils or jackets or by radiant electrical heating in order that the contents may be handled at a temperature at which the viscosity of the content is lower than the viscosity at the ambient temperature. It has also been suggested that induction heating could be employed as an alternative to radiant and/or steam heating.
It is found that the cost of constructing a robust induction heater is prohibitive. Known induction heaters suffered from inevitable mishandling during use, which resulted in the exposure of, and damage to, the current carrying windings. This is not only dangerous to the user, but also necessitates replacement of the heater.
SUMMARY OF INVENTION
According to one aspect of the present invention there is provided an induction heater comprising a substantially cylindrical jacket adapted to be placed around an article which is to be induction heated, and an induction coil arranged within the jacket, characterized in that protuberances project inwardly from the internal surface of the jacket to keep the article spaced apart from the said surface so as to avoid abrasion of the surface by the article.
By providing the abovementioned inwardly projecting protruberances, it is possible to greatly reduce the abrasion of the inner surface of the article and so prevent exposure of the conducting coils which lie below the said inner surface.
Conveniently the protuberances are axially extending ribs.
Although the magnetic flux through the interior of the coil is substantially uniform near the centre of the coil, there is some variation from the ideal Helmholz field. In the interests of uniform heating the article is thus located by means of the axial protruberances.
Preferably, the protuberances incorporate means to provide a change in the visible colour thereof when worn down.
In order to prevent damage to the coils after extended use, it has been found useful to incorporate a coloured material into the ribs as a layer provided towards the base of each rib. As the rib is worn down towards the inner surface of the jacket, the coloured material becomes exposed and provides an indication that the induction heater should be re-lined. Although it is considered that the most useful coloured material would be relatively hard and therefore not mark the drum, it is also considered that in certain applications the coloured material could be sufficiently soft to leave a visible mark on the drum.
Typically, the induction heater comprises a cylindrical jacket and an induction coil, the jacket comprising a cylindrical former on the outside of which the coil is wound, and an outer cover in the form of a plurality of part-cylindrical segments joined together to cover the outside of the coil.
By employing this form of construction, preferably with two shells forming the outer cover, it is possible to construct an induction heater having a relatively smooth outer surface. This is important in many applications where hygenic conditions are required. Furthermore the multi-part construction aids rebuilding of the heater when the wear limit is reached.
The protuberances may be integral with the cylindrical jacket, or may be secured
REFERENCES:
patent: 1885171 (1932-11-01), Balmer
patent: 2848566 (1958-08-01), Limpel
patent: 3228735 (1966-01-01), Stewart
patent: 3502840 (1970-03-01), Khrenov et al.
patent: 3678883 (1972-07-01), Fischer
patent: 3691339 (1972-09-01), Cachat
patent: 3805010 (1974-04-01), Cuvelier
patent: 3827275 (1974-08-01), Suttan et al.
patent: 3860737 (1975-01-01), Moscatello
patent: 3922999 (1975-12-01), Meginnis
patent: 4247736 (1981-01-01), Grigoriev et al.
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