US1867737A - Carburizing furnace - Google Patents

Description

19, 1932. H w ER I CARBURIZING FURNACE Filed July 11, 1930 patented July 19, 1 932 UNITED STATES reams?! PATENT HAROLD W. FLETCHER, F HOUSTON, TEXAS, ASSIGNOR TO HUGHES TOOL COMPANY, HOUSTON, TEXAS, A CORPORATION OF TEXAS GARJB'U'RIZING FURNACE Application filed July 11,

My invention relates to furnaces for the I heat treatment of metals, and is particularly adapted for use in treating tools and similar objects by heat in the presence of a carburizing atmosphere.

is an object of my invention to provide means to maintain within the furnace a temperature such as is necessary for the proper treatment of the tools through the use of a heating unit entirely within the furnace.

It is another object of the invention to provide means for circulating the carburizing material constantly through and against the tools to be hardened so that said tools may be uniformly exposed to contact with the carburizing materials.

I also desire to form a simple and compact structure of heat treating furnace in which the metals or tools to be treated may be readi- 1y introduced therein for treatment and also readily removed after treatment.

Referring to the drawing herewith, I have shown in Fig. l a central vertical section through a furnace constructed in accordance with my invention. "Fig.2 isa. transverse .section taken on the plane 22 of Fig. 1.

I have shown my furnace as cylindrical in general outline, although it is to .be'understood that, it may be made in anydes red shape or form. There is an outer shell 1 having vertical sides and a circular base 2 which is adapted to contain a heat insulating material 3. Said insulating material may be of a general fibrous construction such as asbestos or 5 any similar well known type of heat insulating material unaffected by ordinary high temperatures.

Within the outer wall 3 of heat insulating material is an inner wall or lining 4 of firebrick or other similar heat resisting material of a rigid nature, which forms an interior linin for the furnace. The lower section of the rebrick shown at 5 is-formed' with a series of recesses 6 therein to receive'the lower 5 ends of guide members 7. Said guide members. may be of angle iron construction, sup ported at their upper ends by connection with a plate 8 resting upon the upper end of a ring 9 of firebrick. Between the guide members? and the wall 1980. Serial No. 467,203.

4 of the furnace is a space within which I place my heating unit indicated at 10, said heating unit is preferably an electrical heating unit made'of strips of electricalresisting material formed in ribbons of metal extendmg in loops up and down the face of the wall 4. This ribbon of material is connected at" and have an outer shell indicated at 17. The

ring 16 extends downwardly below the ring 15 and is spaced slightly from the guide members 7. The metal sheath 17 on the ring 15 has radially extending plates 18 through which screw rods 19 may project. Said rods are shown as pivotally secured at 20 to the outer heat insulating wall 1 and extend upwardly through the plate 18v and have thumbnuts '21 on their upper ends.

In the carburizing operation gas is introduced into the furnace-by Way of a pipe 22 extending into the inner ring 16 for a short distance and connected with a central passage 23 which extends downwardly through the cover plate and furnishes space for the passage ofxa carburizing gas, and also receives a shaft 24 upon a motor 25 mounted on the-upper side of the cover plate. The passage23 is closed below the motor 25 by a plate 26. which largely obviates the escape of gas around the motor shaft. On the lower end of the motor shaft and within the furnace is a fan 27.

Spaced slightly below the fan 27 is an annular plate 29 supported on .the lower side of the cover plate and allowing the fan to circulate the gas in the furnace laterally around the outer edge of the plate 29. Said gas may pass downwardly through the furnace and furnace.

upwardly through the opening in the plate 99 to be again circulated outwardly as before. There is a valve 31 in the gas line to regulate the amount of gas entering the I find it necessary to provide a vent for the escape of the used gas from the furnace, such a vent is shown at 32. It extends upwardly through the cover plate and connects with the line 33 through which the gas may be carried away.

To determine the temperature of the furnace, a thermocouple 34 is provided. This structure being well known in the art, no further description is necessary.

For the handling of tools ormetal parts to be carburized, I have shown a basket 35 which may be made of any desired metal adapted to resist the action of heat and in which the tools to be carburized may be inserted.

In the operation of the device, the tools to be carburized will be placed in a basket and lowered into the furnace. The cover plate will then be placed in position and latched firmly against the upper wall of the furnace so that no gas may escape. The heating element will then be turned on to bring the temperature within the furnace to the proper point. Gas will then be introduced through the line 31 to the furnace, and the motor 25 will be started to operate the fan 27 and circulate the carburizing gas through the basket and the tools therein. A slight amount of gas may gradually escape through the pipe 33 to allow for the entrance of new gas as the process is carried out. The gas which is used may be methane or other hydrocarbon gas as may be desired in the particular treatment of the charge of tools in the basket. When the process has been carried on for sufficient length of time to properly treat the tools, the entrance of gas may be discontinned, the motor stopped, and the basket with the tools therein removed.

The advantages of this construction lie in the fact that the heating of the furnace may be carried on with the heating element entirely within the inner chamber of the furnace. Furthermore the manner in which the carburizing gas is circulated through the tools during their treatment enables me to obtain a uniform contact of the gas with all of the tools being treated so that uniform and furnace, a shaft for. said fan extending through said inlet, means to rotate said fan, and a vent for the gas from said furnace.

In testimony whereof, I hereunto aflix my signature, this 7th day of July, A. D. 1930.

HAROLD W. FLETCHER.

fan on said door and a vent from said furnace for spent gas.

2. A furnace, a heating unit within the same, an inlet opening for gas to said furnace, a rotating fan to circulate the gas in said

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