Industrial electric heating furnaces – Resistance furnace device
Patent
1991-11-26
1993-10-05
Reynolds, Bruce A.
Industrial electric heating furnaces
Resistance furnace device
373111, 373117, 373128, 432121, 432253, H05B 310
Patent
active
052512312
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vacuum furnaces and, more particularly, to the arrangement of electrical heating elements in such a furnace.
2. Description of the Related Art
Conventionally, electrical heating elements are disposed in such furnaces closely adjacent to the walls of the furnace, the elements comprising either sinuously wound elongate resistive elements, or pad-like sintered resistive elements arranged around the inner periphery of the furnace. Vacuum furnaces have a pressure vessel inside which are arranged insulating elements to minimise heat transfer to the walls of the pressure vessel in order to protect the integrity of the vacuum under which the vessel operates in use.
However, when there are multiple workpieces being treated in the furnace, unless they are all positioned equidistantly from the heating elements, non-uniform heat treatment of the load may occur. Furthermore, masking of the radiated heat applied to particular workpieces can also occur, resulting in insufficient heat treatment thereof.
Additionally, the application of differential heating to certain types of workpieces is difficult to achieve in a satisfactory manner.
SUMMARY OF THE INVENTION
In order to overcome these problems therefore, according to the present invention there is provided an electrically heated vacuum furnace having a plurality of heating elements distributed in an array extending within the furnace, whereby the application of radiant heat energy from the elements of the array to articles within the furnace can be accurately controlled. Additionally, the furnace may include a plurality of shield sections adjustably disposed within the furnace in shielding relationship to selected parts of articles to be treated in the furnace, whereby differential heating of portions of the articles can be achieved. Alternatively, the furnace may include a plurality of shield sections adjustably disposed within the furnace in shielding relationship to selected ones of plural layers of components, whereby the articles in different layers in the furnace can still be heated and cooled uniformly.
A further advantage of the invention is that a reduction in temperature of the heating elements in comparison with known techniques may be achieved, by spreading the sources of heat radiation throughout the furnace rather than locating them solely around the periphery. The technique also obviates the need for complex and costly gas circulation systems, which are needed to improve heat-up times and temperature uniformities in the low temperature (black radiation) ranges, by enabling close spacing of the workpieces from the heating elements.
BRIEF DESCRIPTION OF THE DRAWING
Two examples of a furnace constructed in accordance with the present invention will now be described with reference to the accompanying drawings in which:
FIG. 1 is a diagramatic cross-section through a first example of a vacuum furnace;
FIG. 2 is a diagramatic longitudinal section through the furnace of FIG. 1;
FIG. 3 is a diagrammatic cross-section of a second example of a vacuum furnace; and,
FIG. 4 is a diagrammatic plan section through the furnace of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The furnace of the first example is shown diagrammatically in FIGS. 1 and 2 for simplicity. The furnace has an elongate, tubular form, housing 1 which comprises a pressure vessel so that the furnace can be evacuated in use. Since the evacuation of the furnace forms no part of this invention, elements relating thereto are neither described nor shown in the drawings.
The furnace has a front opening 2 and a rear opening 3 through which articles to be heat treated in the furnace can be loaded into and passed out of the furnace respectively. Air-tight doors (not shown) are provided to seal the ends of the pressure vessel. A loading chamber and a cooling chamber (not shown) may be located immediately in front of and behind the furnace respectively, communicating with the interior of the furnace through the o
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patent: 3726984 (1973-04-01), Barbier et al.
patent: 3995101 (1976-11-01), Isaksson
patent: 4103099 (1978-07-01), Allsopp
patent: 4347431 (1982-08-01), Pearce et al.
patent: 4416623 (1983-11-01), Takahashi
Croker Michael N.
Ellis Michael G.
Hoang Tu
Ipsen Industries International GmbH
Reynolds Bruce A.
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