US1976557A - Furnace - Google Patents

Description

Oct. 9, 1934. o. s. HASKELL.

FURNACE Filed July 27, 1955 F'igJ.

| I I I I I I I I I I I I I I Fig. 5.

Inventor: Orin 5. Hdskeus u 7 Attorney.

4o bodying my Patented Oct. 9, 1934 FURNACE Orin S. Haskell, Scotla, N. Y., asdgnor to General Electric Company, a corporation of New York Application July 2'1, 1933, Serial No. 682,434

8Claims.

My invention relates ticularly to furnaces for heat treating or annealing metals, and has for its object an improved fumace of this type wherein provision is made for speed, uniformity and accuracy of control of the heating and cooling operation.

My invention has special application to furnaces such as disclosed in the Farmer Patent No. 1,739,958 dated Dec. 17, 1929, in which the heating means is mounted in a hood which encloses the charge during the heating operation, after which the charge is removed from the hood, either by raising the hood or by lowering the charge, for the cooling operation. The charge is furthermore enclosed in a metal shield which remains over it during the heating operation and also during the whole or substantial part of the cooling operation to prevent exposure of the heated charge to the outside air and resulting oxida- '20 tion.

In carrying out my invention I provide means for effecting a circulation of the gas inside the metal hood so as to provide for uniformity in the heating and cooling operations. More particularly, I provide a fan having radial blades mounted below the charge together with a support for the charge above the fan provided with a central aperture, whereby the fan forces the gas outward radially to the side wall of the inner metal hood along which the air flows upward and returns centrally through the charge and the aperture in the support to the fan. I have also provided means external to the metal hood for accelerating the cooling rate together 5 with a seal for the hood.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is an elevation view largely in section of an electric furnace eminvention; Fig. 2 is an enlarged plan view showing the details of the support for the charge and the fan; Fig. 3 is an enlarged fragmentary view showing the cooling means applied externally to'the hood, while Fig. 4 is a fragmentary view similar to Fig. 3 showing a modified form of cooling means.

Referring to the drawing, while I have shown my invention in one form in connection with a single, heat insulated supporting base 10, it will be understood that there may be a'plurality of these bases for supporting the charge on which the charge may be placed as desired after which the heating hood 11 shown as being cylindrical in shape is placed over the charge, as by suitable means such as a crane. The use of a plurality of to furnaces, more parbases provides for the more efficient utilization of the heating hood, for while one charge is being heated others may be cooled or loaded on a base.

As shown, the base 10 is substantially horizon- 6o tal and it is built up from spaced metallic plates 12 and 13 between which is suitable heatinsulating material 14, the plates being secured together by suitable braces and supported in elevated relation with the floor or foundation by means of a plurality of posts 15. Around theperiphery of the support 10 is' a channel 16 for containing a suitable sealing liquid '17, such as oil, water, or any molten or fluid compound which may be replenished from a supply pipe -18. This seal is for a shield or casing 20 which encloses the charge 21. The shield is made from a relatively thin sheet of metal and it is preferably cylindrical in form. It is open at the bottom and provided with a horizontal flange 22 at the bottomwhich rests on the base 10. The outer edge of the flange 22 is turned downward to form a second flange 23 extending around the periphery of the shield and immersed in the sealing'fluid 1'1 whereby a gas-tight seal is formed the base.

In this way the outside air is excluded from the interior of the shield 20, in other words, from the heating chamber enclosed by the shield 20 and the base, so that oxidation of the charge is m prevented. Furthermore, by means of suitable pipes 24 and 25 a suitable neutral or reducing gas, such as nitrogen or hydrogen or a mixture of the two, may be admitted into the heating chamber to purge it of air and gases from oil vapors from 90 work. I For the purpose of circulating the gas inside the shield 20 a fan 26 is provided. Preferably the fan is operated during both the heating and cooling operations in order to expedite these ,1 operatiohsLand also to provide for uniformity in temperature in all parts of-the charge. This fan is moimted in the bottom of the heating chamber on the base 10, preferably in such posi- ,tion on the bwerthat it is centrally 1mm with 1 respect to the shield 20. It is mounted for rotation on a shaft 2'7 which is substantially vertical and has its axis substantially coincident with the :yertical center line of the shield 20. This fan is provided with a plurality of radially ex tending blades 28 (Fig. 2) whereby when the fan is rotated the gas in the heating chamber is thrown outward radially with respect to the tan and thereby caused to flow radially from the fan along the bottom of the heating chamber to the I between the shield and '5 horizontal supporting plate 30 to the center of the fan where it is the bottom of, the culation.

The upward flow of the gas along the inside of the shield is produced in part by convection due to heat applied to the side wall of the shield'as by suitable electric heating units 31 for the charge carried on the inner wall of the hood 11. Preferably these heating units are mounted on substantially the entire inner wall of the hood so as to apply heat uniformly to the entire outer side wall of the shield 20. The shield, it will-be- 0bagain thrown outward along heating chamber for recirserved, is of such size as to substantially fill the heating space enclosed by the hood, sufllcient space being provided between the side wall of the shield and the inner wall of the hood for the heating units 31.

The supporting plate 30 is somewhat smaller than the shield so as to leave a relatively narrow space a around its periphery between it and the shield for the circulation of the gas in the shield. The supporting plate is furthermore of special construction to facilitate the efllcient cir-' culation of the gas. -As shown, it is provided with a'flat top for supporting the charge 21, the charge being preferably arranged or mounted on the plate in an annular form so as to leave a central opening or zone32 for the downward circulation of the gas to the central apertures 29 in the supporting plate. On its lower side the supporting plate is provided with strengthening ribs 33 and with an. annular flange 34 forming a support for the plate, which flange in turn rests on a circular supporting member 36 placed just above the fan 26. This member 36 is provided with a central aperture 37 which is concentric with the axis of rotation of the fan and through which the downwardly flowing gas passes to the fan for recirculation. The member 36 is furthermore provided with a plurality of radially and circumferentially extending supporting blades 38 around its periphery which blades rest on the base 10 so as to supp rt themember 36.

The supporting blades 38 of the member 36 are preferably curved somewhat in a plane perpendicular to the axis of rotation of the fan as shown in Fig. 2, the concave surfaces of the blades facing the axis of rotation of the fan. The supporting blades 38 are furthermore arranged at a sub-.

stantial angle with radial lines extending from the axis of rotation of the fan and through the blades. This curved shape of the blades 38 and their angular relation provides for maximum emciency of flow of gas delivered by the fan.

As shown, the fan is driven by a motor 39 mounted on a bracket 40' secured to the lower side of the supporting base 10 and having its shaft connected through a universal or flexible coupling 41 to the shaft 27 of the fan. The motor operatesto drive the fan in the direction with respect to the'blades 38 indicated in- Fig. 2 by the-arrow 42. The efficiency of the fan is furthermore improved by mounting each fan blade 2841i; a considerable angle with a radial line passing through it from the axis of rotation of the fan, as shown in Fig. 2, this angle being described in-a direction opposi to the direction of rotation of the fan.

Preferably the fan is formed from a circular metal plate or disc 43 provided with a central hub 44 which is secured to the fan shaft 27. The

hood 11.

shaft 27, a well 45 is formed around the shaft in the supporting bracket 40, the top opening of the well as defined by the bracket being sealed by providing a suitable gasket between the bracket and the supporting base 10. At the bottom of the well a suitable packing gland 46 is provided around the shaft 27. This oil well is maintained filled with asuitable oil from a reservoir 47 which is connected to the well through a pipe 48.

Any suitable construction may be used for the As previously noted, the hood carries on its inner face a plurality of electric heating units 31. Preferably the hood is constructed of suitable electrically insulating and heat refractory material 50, the whole being surrounded and reinforced by a suitable metallic casing 51.. A

central attachment means 52 ,is provided at the by a casing 54 where connections are made "with a suitable electrical supply source.

In accordance with my invention I furthermore provide means for providing a controlled rate of cooling of the charge .after the heating hood 11 has been removed for the cooling operation. It will be understood that during the cooling operation the shield 20 remains in place to exclude the outside atmosphere from the charge. For this purpose I provide a metallic duct or pipe 55 which encircles the shield at its upper end and is rigidly secured thereto as by a brazed joint 56. The pipe is provided with apertures 57 in its lower side in position to direct water or other cooling fluid from the pipe against the outer, wall of the shield. When the heating hood 11 has been removed, a suitable connection is made between a source of supply of water or other cooling fluid, and the pipe 55 and the water admitted at such a rate as to give the desired cooling rate for the charge. The water flowsdownward over the outer surface of the shield, \thus providing an effective cooling means.

If desired the cooling pipe may be removably supported on the hood, as by lugs 58 (Fig. 4) carried by the hood, so that it can be put in position after the heating hood has been removed.

What Iv claim as new and desire to .secure by Letters Patent of the United States, is:-

1. A furnace comprising bottom, top and side walls forming a closed heating chamber, heating means adjacent said .side walls, a fan provided withwadially extending bottom wall substantially centrally thereof for rotati about a substantially vertical axis, a supporting plate for the charge mounted above said fan and of somewhat smaller size than the chamber so as to leave a space between said side wall for the circulation of the gas in said chamber, said supporting plate being provided with a substantially central aperture for the downward flow of gas, means for rotating blades mounted on saidits periphery and said fan whereby the gas in said chamber is forced radially outward toward the side wall of said chamber and then upward, said gas returning downward to the fan through a central region of saidchamber and said aperture, and stationary radially extending blades around the periphery of said fan.

,2. A furnace comprising a supporting base, a supporting plate for the charge mounted above said base in spaced relation therewith, a fan mounted between said base and said plate for forcing the gas in said chamber radially outward, stationary radially extending blades around the periphery of said fan, a removable shield enclosing the charge resting on said base, means providing a gas-tight seal between said shield and said base, a heating hood enclosing said shield and resting on said base and heating means mounted on the side wall of said hood.

3. A furnace comprising a-supporting base, a supporting plate for the charge mounted above said base in spaced relationtherewith, said plate being provided with a central aperture, a removable shield enclosing the charge resting on said base, means providing a gas-tight seal between said shield and said base, a heating hood enclos-' ing said shield and resting on said base, heating means mounted on the side wall of said hood, a fan mounted between said base and said plate below said aperture arranged to force the gas in said shield' radially outward to the side wall of said shield, the gas then-flowing upward along the side wall of the shield and returning through a central zone and said aperture to said fan, and

. stationary radially extending blades around the periphery of said fan.

4. A furnace comprising a supporting base, a fan mounted centrally of said base for rotation about a substantially vertical axis, radially extending blades on said fan arranged to produce a radial flow of gas when said fan is rotated, a member above said fan provided with curved supports forming stationary fan blades around the periphery of said-fan, said member being provided with an aperture substantially above said fan, a supporting plate for the charge mounted ing the charge resting on said base and a removabove said member, said plate being provided with a central aperture substantially above the aperture in said member, a removable shield enclosable heating hood enclosing said shield.

5. A furnace comprising a base, a support for the charge on said base, a fan mounted between said support and said base arranged to produce a circulation of gas radially along said base, a metal shield arranged to be placed over said fan and said support and the charge mounted on said support, a hood arranged to enclose said shield, heating means carried by said hood, and means for applying a cooling medium to the exterior of said shield.

6. A furnace comprising a base, a support for the charge on said base, a fan mounted between said support and said base arranged to produce a circulation of gas radially along said base, a metal shield arranged to be placed over said fan and said support and the charge mounted on said support, a hood surrounding said shield, heating means carried by said hood and a duct means mounted on the exterior of said hood provided with orifices for directing a cooling fluid over the exterior surface of said shield.

7. A furnace comprising a base, a support for the charge on said base, a fan mounted between said support and said base arranged to produce a circulation of gas radially along said base, a 05 metal shield arranged to be placed over said fan and said support and the charge mounted on' said support, a hood arranged to enclose said shield, heating means carried by said hood, duct means for directing a cooling fluid'over said hood, and means on the exterior of said hood for removably supporting said duct means.

8. A furnace comprising a base, a supportfor the charge on said base, a removable metal shield enclosing said support and the charge mounted on said support, a fan for producing a circulation of gas in said shield, a hood enclosing said shield, heating means carried by said hood, and means for applying a cooling medium to the exterior of said shield.

ORIN S. HASKELL.

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