US2167821A - Continuous heat treating furnace - Google Patents

Description

'Patented Aug. l, 1939 UNITED STATES PATENT oFElcE CONTINUOUS HEAT TBEATING FUBNACE Application November 17, 1937, Serial No. 175,122

5 Claims.

This invention relates to continuous furnaces and, more particularly, to an improved type of over-fired furnace for heat treating articles, such as wire or rod stock, in improved protective containers.

It is customary to place relatively small articles, such as coils or bundles of wire or rod stock, in metallic heating boxes or containers -for the purpose of annealing, normalizing, or otherwise heat treating, so as to protect the surface of such articles from the intense heat in the furnaces.

Heretofore, it was usually the practice to heat by the so called batch method, whereby a plurality of these containers holding the articles to be heat treated were placed in a pit-type furnace and heated.. While the batch method has proven successful and produces excellent results, the rate of productivity of such a furnace is low.

Wire or rod stock has also been heat treated by the so called continuous method, which comprises drawing several strands at a time from coils or bundles through a furnace, or through molten salt, or other heat treating mediums. The continuous method can employ heat treating units which give a greater rate of productivity than obtained by the batch method but the quality of the product is liable to be inferior due to a certain amount of unavoidable exposure to the air, and to the fact that the heating and cooling cycles are of shorter duration.

While each of these heat treating methods have `their advantages and disadvantages, as has been explained, they use an excessive amount of fuel and are, therefore, very inemcient.

It is an object of this invention to provide a heat treating furnace and method wherein the combined advantages of both the batch and continuous methods are obtained; namely, the quality heating characteristics of the batch method and the rate of productivity of the continuous method, and at the same time provide a furnace in which the fuel consumption is at a minimum.

lt is another object of this invention to provide an improved type over-fired continuous furnace for heat treating articles in which the articles move automatically therethrough and which includes means for controlling the movement of said articles therethrough.

lit is a further object of this invention to provide an improved protective heating box or container for use in continuous furnaces in which the articles to be heated are placed.

Various other objects and advantages will more fully appear during the course of the following specication and Will be more particularly pointed out in the appended claims.

In the accompanying drawing we have shown, for-the purpose of illustration, one embodiment which our invention may assume in practice.

In the drawing:

Figure 1 is a longitudinal vertical section through the center of the improved type overflred continuous furnace of our invention.

Figure 2 is a sectional view taken on the line II-II of Figure l;

Figure 3 is a sectional view taken on the line III-Ill of Figure l;

Figure 4 is a sectional view taken on the line lV-IV of Figure l; Y

Figure 5 is a longitudinal section through the center of the improved type protective heating box or container of our invention; and

Figure 6 is an end view thereof.

'The improved over-red continuous type furnace of our invention comprises a preheating chamber t?, a main heating chamber 3, a cooling chamber Land a hearth 5. The main heating chamber is separated from the cooling and preheating chambers by refractory bulkhead walls or bames t and. l, respectively. The outer ends of the cooling and heating chambers are closed by refractory Walls t and- 9, respectively. The end wall and bulkheads are provided with openings, the purpose of which will be described later in the specication.

The hearth h is preferably inclined and provided with a pair of longitudinally extending, spaced-apart guide means, such as shelves or ledges, it having a longitudinally extending air passageway li therebetween centrally of the furnace in the main heating and preheating chambers, and a similar air passageway l2 between the guide ledges in the cooling chamber. The cooling chamber has an entering air-duct lli,` preferably disposed in the side wallthereof,and the preheating chamber has a gas exit duct ld which is connected to the stack or to a recuperator, should one be employed. At one end of the furnace outside of the preheating chamber is 1ocated a loading platform lb and at the opposite end of the furnace outside of the cooling chamber there is provided an unloading platform ll and a Geneva motion-like means lt which is driven at a predetermined rate of speed by a source of power (not shown). v

There is provided adjacent the bulkhead 6 between the cooling chamber and the main heating chamber, a burner or burners I8 for heating the main heating chamber and furnace. Any suitable fuel, such as oil, gas, pulverized fuel or a combination thereof, can be used for heating the furnace. If desired, the burners may be placed in the side walls of the heating chamber, although the end location, as shown, is preferred.

The improved type of protective heating boxes or containers used in connection with this continuous furnace, in which articles such as coils of wire and rod stock are placed for heat treating, comprise an inner cylindrical body I9 having an outer diameter slightly less than the inside diameter of the coils of wire placed therein, and a substantially larger outer cylindrical body spaced from and enclosing the inner cylindrical body. These two cylinders are securely connected together at one end by means of a flanged disklike portion 2I. On the opposite end of the cylinders there is provided a removable similar disklike end portion 22 which is adapted to be held in place on the end of the cylinders by means of the tapered key 23 which passes diametrically through the end of the inner cylinder in engagement therewith. The coils of wire, rod stock or other articles to be heat treated are placed in the container in the space between the walls of the two cylinders. The outer surface of the inner cylinder is preferably provided with ribs or projections 24 to prevent direct contact of the articles or coils of wire with the hot surface of the container.

After the protective containers have been properly filled with the articles to be heat treated they are placed on the loading platform I5 at the end of the furnace and adapted to be progressively moved into the furnace and passedsuccessively through the preheating chamber, the main heating chamber and the cooling chamber and the openings in the bulkheads therebetween by means of gravity at apredetermined speed, which is controlled by the Geneva motion-like member I6 which also transfers them to the unloading platform I1 after they have been .heat treated in the furnace. It is important that the openings in the bulkheads and end walls are just large enough to allow the protective containers to pass therethrough so that the gases will be directed thereby and travel properly through the' furnace. It will be understood that the anged portions of the disks 2I and 22 provide rolling surfaces for the containers which are adapted to cooperate with the ledges I0 in the hearth to rotatably guide the containers through the furnace. It will also be noted that these flanged portions are adapted to space the cylindrical portions of the containers from each other in order that the hot gases or cooling air may circulate around and between the containers in the furnace. When heating the work for bright annealing, the boxes may be packed with some suitable material, such as charcoal or iron filings, to absorb oxygen and other active harmful elements.

The path of the combustion air andgases will now be described. The inductive effect of the burner or burners I3 firing through the burner ports 24 in the bulkheads 6 creates a partial Vacuum in the cooling chamber 4, thereby drawing cool air into thechamber through the duct I3, which is connected to the air passageway I2 in the bottom thereof.` This air passes, as shown by the broken arrowhead lines, into the passageway I2, up through and around the protective containers or hot-boxes inthe cooling chamber, absorbing a considerable amount of heat therefrom. The boxes are thereby cooled and the heat removed is reclaimed by the secondary vcombustion air. Combustion takes place as described in the heating chamber 3 above the charging line, and the combustion gases are forced downwardly by the bulkhead .1 between and around the protectve containers into the hearth flue or passageway II at the bottom of the main heating chamber, from which the gases pass into the preheating chamber 2 upwardly between and around the protective containers and out through the exit gas flue I4 under the influence of the stack draft. It will be understood that the protective heating boxes or containers are subject to a rolling motion through the furnace, thereby expediting the transfer of heat and insuring uniformity of heating. If desired, protective boxes or containers of other forms could be used. and pushed or slid down suitable skid-rails on a hearth by some suitable mechanical means, but it is preferable to use a heating box of the cylindrical type, such as shown.

While we have in this application specically described one embodiment of our invention, it will be understood that this embodiment is merely for the purpose of illustration and description and that various other forms may be devised within the scope of our invention, as dened in the appended claims.

We claim:

1. In a continuous furnace for heat treating wire and rod stock, an inclined hearth, said Yhearth having spaced-apart ledges therein extending longitudinally of said furnace, a series of metallic protective heating containers which are adapted to move rotatably over said hearth and through said furnace by means of gravity, each of said containers comprising an inner cylinder having a larger outer cylinder -spaced therefrom, and having' a flanged disk-like end portion rigidly secured to eachend thereof, a removable portion carried by at least-one of said disks to give access to the space between the cylinders, said space between the cylinders adapted to receive the coils of wire or Idd stock to be treated, the anges of said disks adapted to cooperate with the ledges in said hearth to guide said containers through the furnace, and means associated with said furnace for controlling the gravitational movement of said containers therethrough. f

2. In a continuous furnace for heat treating articles, a cooling chamber, .a main heating chamber and a preheating chamber, means for progressively moving articles to be heated into and through said furnace andv chambers, means for drawing cool air into the furnace up through the articles in said coolingchamber into said heating chamber, means between said main heating chamber and said preheating chamber adapted to direct said air current andv gases down through the articles in said main heating cham-l ber into said preheating chamberand means adapted to direct said air current and gases up through the articles in said preheating chamber and out of the furnace.

3. In a continuous furnace for heat treating articles, an inclined hearth, a cooling chamber, a main heating chamber, and a preheating chamber, means for spacing the articles from each other as they progressively move by gravity over the hearth and through the chambers of the furnace, means for heating said furnace and drawing a cool air current into the furnace up through and around said articles in said cooling chamber into said main heating chamber, means between said heating chamber and said preheating chamber for directing said air current and gases down through said articles in said main heating chamber into said preheating chamber, and means for directing the air current and gases up through and around the articles in the preheating chamber and out of the furnace.

d. In a continuous furnace for heat treating articles, a cooling chamber, a main heating and a preheating chamber, means for progressively moving articles to be heated through the furnace and said chambers, a bulkhead wall positioned between the cooling and main heating chambers, a second bulkhead wall positioned between the main and preheatng chambers, each of said Walls having aligned openings' therein of dimensions slightly larger than the articles to be heated through which the articles are adapted to pass,

means for firing said furnace positioned opposite a port in the upper portion of said rst named bulkhead and directed into said main heating chamber whereby said ring means draws an air current into the furnace up through yand around the articles in the cooling chamber into said main heating chamber, thence down through and around the articles in said main heating chamber into the preheating chamber and, finally up through and around the articles in the preheating chamber and out of the furnace.

5. In a continuous furnace for heat treating articles, a cooling chamber, a main heating chamber and a preheating chamber, means for progressively moving the articles to be heated through said furnace and said chambers, a longitudinally extending air passageway positioned in the hearth below the travel of the articles in saidv cooling chamber, a similar longitudinally extending air passageway positioned in the hearth below the travel of the articles in said heating and preheating chambers and extending continuously therebetween the combined length thereof, means positioned between the cooling and main heating chambers for drawing a cool air current into the furnace through an air passageway in the cooling chamber and up through and around the articles positioned therein, into said main heating chamber, means positioned between the main heating and preheating chambers for directing said air current down through and around the articles in the main heating chamber into said air passageway located therein and into the preheating chamber, and means for directing said air current up through and around the articles in the preheating chamber and out of the furnace.

GUY O. ACKERMAN, JR. PETER STEWART.

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