US 1725059 A
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Description (OCR text may contain errors)
Patented Aug. 20, 1929.
UNITED STATES PATENT OFFICE- ORA A. COLBY, OF MANSFIELD, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC & KAN- UFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.
Application filed January 19, 1928. Serial No. 247,893.
My invention relates to furnaces and more particularly to furnaces of the tunnel type having open ends to permit the continuous movement of material undergoing heat-treatment through the same.
In furnaces of the above type, difficulty hasbeen experienced in preventing the loss of heat through their open ends, and, since the ends must be maintained open to'permitthe passage of material therethrough, the expedients usually resorted to, such as doors or bafiles, have been found to be undesirable and ineffective.
It is an object of my invention, therefore, to provide means, in furnaces of the above mentioned type, for minimizing the loss of heat through the open ends thereof and, at the same time, permitting the free movement therethrough of work to be heated.
I'have found, by experiment, that, in a furnace of the tunnel type, there is a definite circulation of air through the heating chamber which results in a considerable loss through the chamber by a plurality of hooks of heat, by convection, through the open ends thereof. Streams of cold air enter the chamber, and streams of heated air leave the chamber, through the open ends thereof. I have found, byexperiment, thatthere is a horizontal line, at approximately two thirdsof the height of the area of the open end, below which the cold air enters, and above which the heated air leaves, the furnace chamber. v
The actual loss of heat through the ends of the chamber depends largely, of course, upon the dimensions of the chamber and the working temperature employed. By experiment, I have found that, in an electrically heated furnace chamber approximately 125 feet in length and operating at a temperature of 1650 F., the heated air leaving the chamber moves at approximately 300 feet per minute and represents a loss of about 100 kw. of electrical energy.
In practicing my invention, I provide, in conjunction with an elongated'furnace chamber having open ends, means for forcing a plu'ralit of streams of air, at high pressure, across t e open ends in such manner that the direction of movement of the stream of heated air therethrough is altered and interrupts the incoming stream of cold air.
In the drawing, Figure 1 is a view, in vertlcal longitudiable heat-insulating refractory material defining an elongated furnace chamber 2. Thestructure is suitably reinforced by channel andangle irons 4 which extend a short distance above the roof of the furnace to support a conveyor, as hereinafter described.
A longitudinally extending slot 6 is provided in the roof of the furnace and is coextensive, in length, with the length of the furnace chamber.
Materialto be heat-treated is conveyed 8 which extend through the slot 6 and have secured, at the upper extremities thereof,
rollers 10 or other suitable antifriction means; The rollers 10 are supported upon a-trackway .12, secured to the horizontally extending portions of the reinforcin structure 4, and are adapted to be move therealong. The hooks are connected above the level of the furnace roof, by a plurality of links-14, constitutin a continuous conveyor chain, whereby the ooks may be moved in .unison through the chamber. The conveyor chain extends somewhat beyond the ends of the furnace and is suitably connected to a drivin means to eiect the movement thereof. T e driving means and the return path for the conveyor chain have been omltted from. the drawing, for the sake of clearness, but, since the'conveyor shown is of a type well known in the art, further illustration thereof is not deemed necessary.
The furnace chambe r is heated by suitable the furnace ad'acent and arallel to the upper e of t eopen en thereof and are operatively associated with an air compressor (not shown) or other suitable source of high-pressure air. A slot is provided in the horizontally extending portions of the conduits, longitudinally thereof, and 'is adapted to receive a block 20, which is apertured, as at 22, to constitute a plurality of nozzles. The free ends of the conduits 18 are closed, and the blocks are fitted tightly in the slots formed in the conduits, so that, Wlth the conduits connected to a source of high-pressure air, a plurality of streams of air are forced, at high velocity, across the furnace opening. The number of jets employed may bevaried at will, but there should be such number that the streams of air formed thereby are close enough to constitute, in effect, an air curtain across the furnace opening.
In "the modification shown in Fig. 3,-one of the conduits 18 is extended, as at 24, to lie along the slot 6 in the furnace roof. Nozzles are also provided in the extended portion, and streams of air are directed thereby across the slot to prevent the loss of heat therethrough.
As above pointed out, in the normal operation of the furnace, a stream of heated air, at relatively high velocity, flows through the upper portion of the open ends of the furnace, and .a stream of cold air enters through the lower portion. The curtain of air movin at high velocity from the nozzles 22 alters t e normal circulation of coldand heated air, however, and-prevents the flow of heated air from the furnace chamber. The velocity of the air from the nozzles is of such a value that the stream of heated air is bent downwardly into the path of the cold incoming air, whereby the velocity of the conveyor slot 6.
Throughout the specification, air has been Y referred'to as the mediumv constituting the furnace chamber atmosphere, and that employed in the conduits 18. Obviously, however, myinvention is applicableto furnaces irrespective of the chemical characteristics of the furnace chamber atmosphere, and any desired fluid may be employed in the conduits 18.
By my invention, I have provided a simple and effective means for preventing the loss of heat from an open-end furnace chamber, which does not interfere with the passage of work through the ends of the furnace, and which increases, to a marked degree, the operating efficiency of the furnace. The moving fluid constitutes a permeable screen or door for reducing the amount of outgoing heated air and the incoming cool air while permitting the free movement of articles through the furnace.
Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitation shall be placed thereon -as are imposed by the prior art and set forth in the appended claims.
I claim as my invention;
1. In a heat-treating furnace, the combination with an elongated heating chamber open at the ends thereof and having a normal efllux of heatedair through said open ends adjacent to the roof of the chamber and an influx of cold airthrough the lower portion of said open ends, of means comprising perforated conduits located above theends for forcing air, at high velocity, downwardly across said ends to prevent said efllux of heated air and to force said heated air into the path of said stream of cold air.
2. A heat treating furnace comprising a plurality of walls including a roof and defining an elongated heating chamber open at both ends and a longitudinally-extending slot in said roof, in combination with means for moving material to be heat treated through said chamber, said means having depending portions to move through said slot, and conduitportions located closely adjacent to the ends of the roofand each extending between a side wall and the slot, a plurality of spaced nozzles in the bottom of each conduit and means for forcing air at high velocity through said conduits and said nozzles to provide air curtains across said open ends.
In testimony whereof, I have hereunto subscribed my name this 12 day of January,
- .oRA A. COLBY.