US2131591A - Furnace - Google Patents

Description

W 27, 1938- F. E. KEITH ET AL 2,131,591

FURNACE Filed April 14, 1937 Inventors: Fay E. Keith, Cidr-on F. LindstT-om,

Theh'- Attorney- Patented Sept. 27, 1938 UNITED STATES PATENT OFFICE FURNACE Application April 14,1937, Serial No. 138,778

3 Claims.

Our invention relates to furnaces, more particularly to furnaces provided with sealing means utilizing a liquid or granular sealing material, and has for its object automatic means for venting the furnace to prevent displacement of the sealing means when the furnace is opened or closed.

Although generally applicable to furnaces provided with gas-tight seals, this invention has special application to furnaces of the type provided with a hood or bell-shaped enclosing member which is placed over the charge, heat being supplied to the interior of the hood. A furnace of this type is disclosed for example in Patent No.

1,739,958, issued December 17, 1929, to Malcolm Farmer,

These furnaces are usually provided with gastight sealing means between the hood and the base part on which the hood rests, such sealing means being especially advantageous when the heating chamber formed by the hood is supplied with a special neutral or non-oxidizing gas whereby escape of the gas is prevented. This sealing means commonly consists of a trough around the base member which contains a quantity of a liquid or granular sealing material such as oil or sand and with a flange on the hood which, when the hood approaches its lowermost position, enters the sealing material in the 30. trough. Thus it will be observed that the furnace chamber is actually sealed when the flange enters the sealing material which is shortly prior to the completion of the lowering movement of the hood and therefore the final lowering move- :75 ment compresses the air inside the hood. This results, in the event particularly that the hood is lowered quickly, in suflicient gas pressure to displace the sealing material or even throw the sealing material out of the trough. Also when the hood is raised after the completion of the heating operation, a partial vacuum is created before the seal is broken which vacuum tends also to displace the sealing material.

, In accordance with our invention we provide a vent for the hood which is automatically opened during the lowering or raising of the hood to provide for the free entrance and escape of gas and thus prevent the disturbance of the sealing material.

For a more complete understanding of this invention reference should be had to the accompanying drawing, a single figure of which is a vertical sectional view of a furnace embodying our invention.

Referring to the drawing, we have shown our invention in one form as applied to an electrically heated furnace provided with a hood or bell-shaped member ill which may be raised or lowered to open and close the furnace, although it obviously has general application to sealed fur- 5 naces. The hood I0 comprises heat refractory side and top walls I i which are suitably mounted in a supporting steel framework l2. Suitable electric heating units l3 are mounted on heat refractory and electrically insulating supports 10 secured to the side walls of the hood. This hood normally rests, as shown, on a base ll comprising a bottom wall l5 made of the heat refractory bricks and a supporting steel framework it. This base furthermore may be in the form of a 15 car mounted on wheels as disclosed for example in Patent No. 1,864,354, issued June 21, 1932, to Carl L. Ipsen and Albert N. Otis, whereby, when the hood has lifted, the car may be run under the hood and the hood then lowered onto the car. 20

For the purpose of conserving the heat in the interior of the hood and also the' neutral, reducing or non-oxidizing gas atmosphere, which may be a mixture containing lwdrogen and nitrogen, a gas-tight seal is provided between the bottom 25 edge of the hood and the base member ll. As shown, this seal comprises a trough i1 surrounding the base member, this trough being formed by a strip of steel l8 surrounding the heat insulating bricks IS in spaced relation therewith. To further increase the efllciency of the seal the trough is provided with a sheet metal partition wall i9 at its center which, as shown, is somewhat lower than the wall I8. In the trough is a suitable sealing material such as sand or, as 35 shown, a liquid 20 such as oil filling the trough to the level of the partition i9.

Extending into the trough are two depending sheet steel flange members 2i and 22 secured to it surrounding the hood at its lower end. The 40 outer flange 2i projects downward into the sealing liquid 20 somewhat farther than the inner flange 22. These two flanges 2i and 22 are secured at their upper edges in sealed relation with the lower end of the hood so that when either one or both of them enter the liquid a gas-tight seal is formed. As shown, a horizontal metal plate 23 is provided around the lower end of the hood and tightly secured to and joining the flanges 2i and 22. Also the inner flange 22 extends upward above the plate 23 for a short distance in spaced relation with the lower end of the hood so as to provide a vent chamber 24 around the lower end of the hood, the flange 22 being sealed 55 to the hood at the top by means of a horizontal flange 26.

For the purpose of venting the interior of the hood a plurality of vent openings 26 provided with normally closed valves 21 are provided in the inner flange 22, two being shown in the drawing. The valves 21 are normally each held in closed position by a spring 28 cooperating with the end of a lever arm 29 to which the valve is secured. Attached to each valve is an armature 36 of an operating coil 3| by means of which the valves may be opened.

In order that the valves 21 may be automatically opened whenever the hood is moved with respect to the base either to raise or to lower it, the operating coils 3| for the valves are electrically connected to be energized simultaneously with the energization of an electric motor 32 for raising and lowering the hood. This motor 32 is shown conventionally as a direct current motor and it is connected through suitable gearing 33 to hoisting drums 34 and 35 provided with lifting cables secured to the hood. The motor is controlled by an electromagnetically operated reversing switch 36 having operating coils 31 and 33, the energization of which is controlled by a manually operated two-way switch 40. Thus movement of the switch 40 toward the left to closed position energizes the coil 31 from the supply source 39 whereby the reversing switch 36 is thrown to its left-hand position and the electric motor started in a direction to raise the hood. At the same time the brake coil 4| connected across the motor armature is energized to release the brake 42. Before starting the motor the field switch 43 will of course be closed.

As shown, the two coils 3| are connected through suitable conductors so as to be energized concurrently with the energization of either one oi the coils 31 and 38 by movement of the switch 43 to initiate the raising or lowering operation. When the hood has been raised to the desired height to permit the insertion or removal of a charge the motor 32 is stopped by opening the switch 39 whereupon the switch 36 is moved to its central off position by suitable biasing springs 44 and 45. At the same time the brake coil 4| is deenergized whereupon the brake is applied to secure the hood in its raised position. When it is desired to lower the hood the switch 40 is thrown to its right-hand position to energize the coil 33. If desired, limit switches (not shown) may be provided for deenergizing the motor 32 upon the completion of the raising and lowering movements of the hood.

Thus it will be observed that the valves 21 are moved to their open positions to open the gas vents 26 during the raising and lowering of the hood, the valves being moved to their closed positions to seal the vent openings upon completion of the lowering movement, and also of course upon the completion of the raising movement, when the motor 32 is deenergized by deenergization of the coil 38. This provides for the free entrance of outside air into the heating chamber when the hood is raised and the escape of gas when the hood is being lowered so as to prevent displacement and waste of the liquid sealing material because of a partial vacuum or pressure generated in the chamber during the raising and lowering movement. It will be observed that because of the fact that the flanges 2| and 22 must extend downward into the sealing liquid to a substantial depth to assure a seal, the seal is actually made when the hood is being lowered before the hood reaches its lowermost position, i. e., immediately upon the entrance of the flanges into the liquid. As shown, the outermost flange 2| extends downward somewhat farther than the other and consequently it will first engage the liquid and seal the heating chamber. Conversely when the hood is being raised the seal is not broken until after the hood has been raised an appreciable distance and a partial vacuum would be created in the chamberv were it not for the vent openings.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A furnace comprising walls forming a hood, heating means for said hood, a base for said hood provided with a trough for a sealing material, a flange on said hood extending into said trough. a motor for raising and lowering said hood, means providing a ventilating opening for the escape and entrance of gas with respect to said hood when said hood is raised or lowered, valve means biased to close said opening, an operating coil for opening said valve means, and switching means for energizing said coil concurrently with the energization of said motor to raise or to lower said hood.

2. A furnace comprising walls forming a hood, heating means for said hood, a flange surrounding the lower end of said hood and spaced from said hood, said flange including means connecting with said hood at a point above the lower end of said hood to form an open bottom vent chamber around the lower end of said hood, a base for said hood provided with a trough for sealing material and arranged to receive the lower end of said flange when said hood is resting on said base, a vent aperture in said flange for said vent cham-- ber, a closure member for said aperture, means for raising and lowering said hood, and means operated by said raising and lowering means for moving said closure member to open said aperture and maintain said aperture open while said hood is being raised or lowered so as to provide for the free access of air to the interior of said hood during the raising and lowering of said hood.

3. A furnace comprising walls forming a hood, heating means for said hood, a flange surrounding the lower end of said hood and spaced from said hood, said flange including means connecting with said hood at a point above the lower end of said hood to form an open bottom vent chamber around the lower end of said hood, a base for said hood provided with a trough for sealing material and arranged to receive the lower end 01 said flange when said hood is resting on said base, a vent aperture in said flange for said vent chamber, a closure member for said aperture biased to a position to close said aperture, means for raising and lowering said hood, means for moving said closure member to open said aperture, and means for concurrently operating said raising and lowering means and said means for moving said closure member to maintain said aperture open while said hood is being raised and lowered so as to provide for the free access of outside air to the interior of said hood during the raising and lowering of said hood.

FAY E. KEITH.

CIDRON F. LINDS'I'ROM.

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