JP3040642B2 - heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace for drying and baking coating of an object to be heated, and more particularly to a natural convection type heating which can improve the start-up characteristics at the time of starting and stabilize the heating chamber at an early stage. About the furnace.

[0001]

2. Description of the Related Art Heating efficiency, stability,
An appropriate heating source is selected in consideration of uniformity, safety, etc. Products that burn liquid or gaseous fuel using a burner device as the heating source and directly introduce the combustion gas into the heating furnace to heat the articles have economic advantages such as high heat calories, simple equipment, and easy use. There is.

However, since a large amount of combustion gas must be supplied at all times, the same amount of exhaust gas as the supply is required. The quality of the thermal efficiency of the heating furnace is determined by how much the heat calorie taken out by this exhaust is reduced. As one preferable heating furnace, hot air as a combustion gas is sequentially introduced into a chevron-shaped furnace body with a container lying down, and a low-temperature gas whose temperature has dropped due to article heating in the furnace body overflows from the lower part of the furnace body. There is a heating furnace of the natural convection type. This heating furnace is disclosed in JP-B-58-12513, JP-B-59-42225 and JP-B-63-16673. All of these heating furnaces are based on the present applicant's invention.

[0003] This natural convection type heating furnace utilizes a natural convection mechanism in which hot air having a high temperature stays in the upper part of the furnace body, and a gas whose temperature has dropped due to article heating falls due to a density difference and is discharged from below. High thermal efficiency,
It has the advantage of being economical.

[0004]

The conventional natural convection type heating furnace has a relatively small degree of freedom in design because a burner device is installed below the furnace body, and a belt conveyor is installed on the lower floor surface. In addition, it is difficult to effectively use radiant heat generated by combustion in the burner device.

On the other hand, there is a hot air circulating furnace in which the combustion gas combusted by the burner device is forcibly introduced into the heating furnace through an introduction duct by a circulation pump and circulated, but in this hot air circulating furnace, the inside of the heating furnace is made uniform. There has been a problem that the rise time until the heating temperature is maintained at a high level is long, and the stability of the rise is low when the heating furnace is started.

The present invention has been made in view of the above-described circumstances, and provides a natural convection type heating furnace capable of improving the startup characteristics at the time of starting, stabilizing the heating chamber at an early stage, and maintaining a uniform temperature. The purpose is to:

Another object of the present invention is to improve the heating efficiency by effectively utilizing not only the radiant heat from the heating source but also the radiant heat, without causing large fluctuations on the heating surface in the furnace. Another object of the present invention is to provide a natural convection type heating furnace capable of obtaining a stable and uniform heating space.

Still another object of the present invention is to provide a natural convection type heating furnace in which a heating source is concentratedly arranged on a side or top of a furnace body to facilitate maintenance work.

[0009]

According to a first aspect of the present invention, there is provided a heating furnace to be heated which is conveyed in a heating chamber of a furnace body having an article inlet / outlet. In a heating furnace of a natural convection type provided with a conveyor line for supporting an object, a heating source is provided on at least one of a side portion and a top portion of the furnace body so as to be exposed in a heating chamber above an air inlet, and the heating chamber is provided. An exhaust port is formed at a position below the heating source and at a required distance in the longitudinal direction of the furnace from the heating source, and the upper edge of the exhaust port and the article entrance are lower ends of the object to be heated conveyed in the heating chamber of the furnace body. At least the upper edge of the air inlet corresponding to the heating source is provided below and below the upper edge of the exhaust port and the article entrance.

[0010] In order to solve the above-mentioned problems, a heating furnace according to the present invention has the following features.
As described in claim 2, the heating source is intensively disposed between the exhaust ports provided in the furnace longitudinal direction on the way from the article inlet to the article outlet. As described, the furnace body is one in which the lower part of the furnace body is open.

[0011]

The heating furnace according to the present invention is constructed as described above, and a heating source is provided on at least one of the side and the top of the furnace body so as to be exposed in the heating chamber above the air inlet. Not only direct heating such as radiant heat from the source, but also indirect heating using radiant heat, heating efficiency can be improved by effectively using radiant heat and radiant heat, The rising characteristics can be improved, and the heating chamber can be stabilized early.

Further, even if the furnace body is directly heated by the heating source, since the heating action is a gentle heating effect using radiant heat and radiant heat effectively, a large fluctuation does not occur on the heating surface in the furnace body. A stable heating chamber with a uniform temperature can be obtained.

Further, since the heating sources are arranged intensively between the exhaust ports provided apart from each other in the longitudinal direction of the furnace, the maintenance work of the heating sources can be managed collectively, and the workability at the time of maintenance and inspection is improved. On the other hand, a belt conveyor can be provided on the lower floor surface, and the degree of freedom in design can be increased. Further, by opening the lower part of the furnace body, access to the inside of the heating furnace from below is facilitated, so that maintenance work can be performed more efficiently and efficiently.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heating furnace according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a principle view showing a natural convection type heating furnace according to the present invention. The heating furnace has a mountain-shaped furnace body 1 whose both ends are inclined downward toward the outside. The furnace body 1 has an article inlet 2 and an article outlet 3 open at both ends, and a heating chamber 4 is formed inside. In the furnace body 1, a conveyor line 5 is laid along the top wall from the article inlet 2 to the article outlet 3, and an object 6 to be dried or baked by the conveyor line 5 is conveyed in a suspended state. You.

The upper edges of the article inlet 2 and the article outlet 3 are set to be substantially the same height as the floor level of the lower floor 1a of the furnace body 1, preferably slightly above the floor level. In this case, it is not necessary to provide the lower furnace floor 1a in the furnace body 1, and the lower furnace body may be opened instead of providing the lower furnace floor.

Further, both sides of the furnace body 1 from the article inlet 2 to the article outlet 3 are locally recessed so as to bulge outward to form pits 7, and the heating means 8 is concentrated on the pits 7. Is provided in a standard manner. The heating means 8 is formed by an infrared lamp 9, a nichrome wire heater, a gas infrared ray or the like, and constitutes a heating source. The heating means 8 includes, for example, infrared lamps 9 arranged at predetermined vertical and horizontal intervals so as to be exposed in the heating chamber 4 in a plurality of rows.

Below the furnace body 1 corresponding to the heating means 8 as a heating source, an air inlet 10 which opens in a horizontal plane as shown in FIG. 1 is formed. An air filter 11 is provided. This air inlet 10
Are formed at least below the upper edges of the article inlet 2 and the article outlet 3 as shown in FIG.
By providing the air inlet 10 below the upper edges of the article inlet 2 and the article outlet 3 also serving as the exhaust port, it is possible to prevent the hot air heated by the heating means 8 from flowing backward and flowing out of the air inlet 10. I have.

On the other hand, hoods 13 and 13 are placed near the article inlet 2 and the article outlet 3 of the furnace body 1, and an exhaust pipe 14 is connected to the hoods 13 and 13. Exhaust stack 14
Is provided with an exhaust fan 15 as necessary. In this case, the article inlet 2 and the article outlet 3 also serve as exhaust ports provided apart from the heating means 8 in the furnace longitudinal direction. As shown in FIG. 1, the upper edges of the exhaust ports (article inlet 2 and article outlet 3) are located below the lower end of the heated object 6 conveyed in the heating chamber 4 of the furnace body 1.

Next, the heating operation of the heating furnace will be described.

When the conveyor line 5 is driven, the objects 6 to be heated are carried into the furnace 1 one after another from the article inlet 2 and are heated.
It is conveyed toward the article outlet 3 through the inside.

The heating furnace is heated by the operation of the heating means 8. The inside of the furnace is directly or indirectly heated by radiant heat or radiant heat from the heating means 8, and the temperature rises to a desired temperature, for example, 80 ° C. to 230 ° C. The hot air heated by the heating means 8 rises due to the natural convection action and collides with the top wall of the furnace body 1 and spreads laterally, thereby making the heating temperature in the heating chamber 4 substantially uniform in the horizontal direction.

On the other hand, the air whose temperature has dropped due to article heating in the furnace body 1 descends by being pushed by natural convection action or heated hot air caused by the density difference, and passes through the article inlet 2 and the article outlet 3 to each exhaust pipe. It is discharged from 14.

Further, with the rising action of the heated air by the heating means 8, an amount of air corresponding to the flow rate flowing out of the article inlet 2 and the article outlet 3 is introduced from the air inlet 10 into the furnace. The introduced air is heated by the heating means 8, and the heated hot air repeats the natural convection action described above, so that the heating chamber 4 of the furnace body 1 is heated to a substantially uniform temperature.

Therefore, the furnace body 1 through which the object to be heated 6 passes
The effective heating area (area above the line connecting the upper edges of the article inlet 2 and the article outlet 3) is filled with high-temperature hot air, and when the high-temperature hot air is cooled by the article 6 to be heated, the temperature drops and falls. Since the material is discharged from the article entrances 2 and 3, the inside of the furnace is constantly metabolized, and the effective heating space can obtain a substantially uniform heat distribution throughout.

In this heating furnace, a heating source is provided on the side (or top) in the furnace body 1, and since this heating source is exposed in the heating chamber 4, radiant heat from the heating source is provided. In addition, the heating can be performed without using the radiant heat to leak the heat to the outside, and the heating efficiency can be improved. Therefore, the start-up characteristics at the time of starting the heating furnace can be improved, the rising time can be reduced by almost half as compared with the conventional hot air circulating furnace, and the inside of the heating chamber 4 is maintained at a stable and uniform temperature early in the longitudinal direction of the furnace. can do.

FIG. 2 shows a practical embodiment of the heating furnace according to the present invention.

This heating furnace has a substantially horizontal and tunnel-shaped furnace body 1, and the longitudinal shape of the furnace body 1 is linear or arbitrarily bent. A shield plate 20 having an upper wall deeply bent downward at the article inlet 2 and the article outlet 3 of the furnace body 1.
Is formed, and the upper half of the article inlet 2 and the article outlet 3 is closed by the shield plate 20, so that a mountain furnace is substantially constituted.

In the furnace body 1, a conveyor line 5 is provided along a top wall from the article inlet 2 to the article outlet 3, and the conveyor line 5 guides the article 6 to be heated from the article inlet 2 to the article outlet 3. doing. The conveyor line 5 rises at the article entrance, descends at the article exit, and passes through the object 6 to be heated.
Are guided so as to pass through the upper half in the furnace body 1, and an air layer is formed in a lower portion inside the furnace body 1.

Further, pits 7 which are locally recessed so as to bulge outward are provided on both sides in the furnace body 1, and heating means 8 is exposed in the heating chamber 4 in the pits 7. Is installed as follows. The heating means 8 is formed of an infrared lamp 9, a nichrome wire heater, or the like, and is intensively disposed between the exhaust ports 21 and 21 provided apart from each other in the furnace longitudinal direction, taking into consideration the convenience of wiring and maintenance work. ing. The heating means 8 may be provided at the top of the furnace body instead of being provided at the side of the furnace body 1,
It may be provided on both the side and the top.

The exhaust port 21 is provided on the side of the furnace body near the article inlet 2 and the article outlet 3 and, if necessary, at an intermediate position in the furnace longitudinal direction. The heating chamber 4 formed in 1 is open to the atmosphere.
Air collecting hoods 13 are respectively installed above the exhaust ports 21 and 21 of the furnace body 1.
4 is connected to the lower end. A forced exhaust fan 15 is provided in the exhaust pipe 14 as needed.

In this heating furnace, the furnace body 1
The height of the upper edge of the air inlet 10 for supplying air into the inside is defined as Ha,
The lower edge height of the shielding plate 20 is Hb, and the upper edge height of the exhaust port 21 is H.
c, when the height at which the object 6 passes through the furnace is Hd,

## EQU1 ## It is set so as to satisfy the condition of Ha <Hb ≦ Hc ≦ Hd. In the furnace body 1 shown in FIG. 2 as well, since the air inlet 10 is open in the horizontal plane, the opening height level of the air inlet 10 is Ha over the entire opening. Upper edge height Ha of the air inlet 10
Is a concept equivalent to the opening height level in FIG. When the air inlet 10 is open in the horizontal plane, the upper and lower edges of the opening are at the same height level (in the same plane). The opening height level of the inflow port 10 may be the same, but when the air inflow port 10 is not open in the horizontal plane as described later, the upper edge height Ha of the air inflow port 10 is equal to the exhaust port 21.
Is a reference for comparison with the upper edge height Ha.

With the arrangement satisfying this condition, the air flowing in from the air inlet 10 is heated by the radiant heat and the radiant heat from the heating means 8 to rise in temperature and become hot air. This hot air rises due to natural convection, and collides with the top wall of the furnace body and spreads in the lateral direction. On the other hand, the gas cooled by heating the object to be heated 6 descends due to natural convection, and is exhausted in ascending order of temperature. It overflows into the atmosphere beyond the mouth 21. Since the exhaust port 21 is not directly connected to the exhaust stack 14, the exhaust port 21 does not have a chimney effect (suction effect). In addition, you may form as shown in FIG. 3 outside the furnace body 1, and may provide the wind guide duct 22 as shown in FIG.

Since the exhaust port 21 is not directly connected to the exhaust pipe 14, high-temperature hot air is not forcibly sucked from the exhaust port 21. The high-temperature hot air heated by the heating means 8 stays in the upper portion of the heating chamber 4 in the furnace body 1 and efficiently heats the object 6 passing through the heating chamber 4 by utilizing natural convection. In addition, since all the hot air heated by the heating means 8 is effectively used for heating the object 6 to be heated in the furnace body 1, the thermal efficiency is improved. Further, by adjusting the amount of heating in the heating means 8, the temperature of the heating chamber in the furnace body 1 is set to, for example, 80 ° C to 2 ° C.
It can be easily adjusted to a desired temperature of about 30 ° C. The temperature distribution in the heating chamber 4 in the furnace body 1 can also be kept uniform. Various temperatures are selected for the temperature in the heating chamber 4 according to drying, painting, baking, and the like. However, if the temperature in the heating chamber 4 exceeds 230 ° C., the conveyor runs out of oil, which is not preferable.

Since an air layer is formed below the exhaust port 21 of the furnace body 1, when the object 6 to be heated is conveyed in the furnace body 1, hot air containing a solvent escapes to the air layer and diffusion occurs. Plan,
Since it can be diluted, it is possible to effectively prevent ignition of a solvent such as thinner, prevent explosion of a heating furnace, and improve safety.

The heating furnace employs a natural convection method, in which the lower end of the conveyed object is guided inside the furnace body 1 while being positioned above the lower edge of the shielding plate 20. The air inlet 10 of the heating means 8 is provided below the lower edge of the shield plate 20, and the air outlet 21 for opening the atmosphere, which is arranged at least at the furnace body inlet / outlet portion, has its upper edge at least equal to the lower edge of the shield plate 20. And since it is located below the lower end of the object 6 to be heated,
The object to be heated 6 can be effectively heated, such as by baking, using the natural convection, and the heating state is easy and uniform, and the quality of the product can be improved.

Further, since the air inlet 10 is disposed below the lower edge of the shield 20 and the upper edge of the exhaust port 21, the air inlet 10 and the exhaust port 21 are used when a natural convection heating furnace is used. The backflow of air is prevented, and the article to be heated 6 is effectively and stably heated.

FIG. 5 illustrates a first modification of the heating furnace according to the present invention.

The heating furnace shown in this modification has the same structure as that of the furnace 1 in which the shielding plate 20 extends over the article inlet 2 and the article outlet (not shown). The height Hb of the lower edge of the shielding plate 20 and the height Ha of the upper edge of the air inlet 10 to the heating means 8 are H
a <Hb is set.

The exhaust port 21 has an adjustable plate 2 that can be adjusted up and down.
5 is added, and the height Hc of the upper edge of the exhaust port 21 is changed by the adjustment. Even at the lowest position, Hb ≦ Hc.

The conveyor line 5 is erected along the upper wall of the furnace body 1, and the objects 6a and 6b to be heated are suspended by the conveyor line 5 and move. Since the height of the lower end of the object to be heated is different between the case where the small object to be heated 6a is hung and the case where the large object to be heated 6b is heated, the adjusting plate 25 is vertically adjusted to adjust the upper edge of the exhaust port 21 and the object to be heated. Hb ≦ H
Optimize the relationship of c ≦ Hd. The required minimum combustion consumption can be achieved according to the size of the objects to be heated 6a, 6b.

The article inlet 2 and the article outlet 3 are connected to the exhaust port 2
In the case of 1, the height of the lower edge of the shielding plate 20 may be adjusted up and down.

FIG. 6 shows a second modification of the heating furnace according to the present invention.

The heating furnace shown in this modification is a furnace
a, an exhaust port 21 is formed in the exhaust guide 21, and the exhaust from the exhaust port 21 is guided laterally through an exhaust guide 27.
7 is opened to the outside air.

Also in this case,

## EQU2 ## It is desirable that the following relationship is satisfied: Ha ≦ Hb <Hc ≦ Hd.

Further, a burner device 28 may be installed in the duct 27 of the air inlet 10 and the inflowing air may be heated by the burner device 28.

FIG. 7 shows a third modification of the heating furnace according to the present invention. The heating furnace shown in this modification is
An air curtain device 30 is provided at the article inlet 2 and the article outlet (not shown), and the air curtain device 30 allows the heating furnace to be straight, without being formed in a chevron shape. They have substantially the same function.

The air curtain device 30 is provided with a blowing duct 31 on one side wall of the article inlet portion of the furnace body 1 and a suction duct (not shown) on the other side wall in a longitudinally opposed manner. Are arranged in parallel, a plurality of pairs of blowout ducts are connected to an air supply source via an adjustment valve 32, and a suction duct is connected to a suction device (not shown).

The other configuration is not substantially different from the heating furnace shown in FIG.

FIG. 8 shows a fourth modification of the heating furnace according to the present invention.

The heating furnace shown in this modification has a heating furnace exhaust structure shown in FIG. 5 and an air curtain device 3 shown in FIG.
0 is combined.

In the heating furnace shown in each of the modifications, the air inlet 1 is heated by heating means 8 provided on both sides or the top of the furnace body 1.
The temperature of the heated air is increased by heating the air taken in from 0, and the upper portion of the furnace body 1 is always filled with high-temperature hot air by natural convection, and the object to be heated is heated in this high-temperature portion. In addition, the exhaust ports 21 and the like are rationally arranged so that heating can be effectively performed with the minimum necessary thermal energy, and the fuel consumption rate is greatly improved.

In a heating furnace of this type using hot air, a circulating hot stove is mainly used in order to effectively utilize heat energy, but a special burner, a blower or a duct can be omitted. The simple structure can reduce equipment costs and costs, and also uses natural convection, so that metabolism is effectively performed and impurity molecules are constantly discharged, contaminating the coating film of the object to be heated in baking coating. Since the flow rate of hot air is gentle, the heating state is easy and uniform, and the quality of the product can be improved.

FIG. 9 shows another practical embodiment of the heating furnace according to the present invention.

The heating furnace shown in this embodiment has a shielding plate 20 for covering the upper half of the article inlet 2 and the article outlet 3 of the furnace body 1, and exhausting gas as needed at the center of the furnace body 1. The mouth 21 is arranged. The height Hb of the lower edge of the shielding plate 20 and the height Hc of the upper edge of the exhaust port 21 are set to Hb = Hc. Then, the article inlet 2 and the article outlet 3 are used as one of the exhaust ports. Therefore, the exhaust pipe 14 is disposed above the article inlet 2 and the article outlet 3, and the air collecting hood 13 connected to the lower end thereof is opened.

On both sides of the furnace 1, pits 7 are formed so as to bulge outward, and infrared lamps 9 and nichrome wire heaters as heating means 8 are intensively arranged in the pits 7. The air flowing in from the air inlet 10 is heated by the radiant heat or radiant heat from the heating means 8 to increase the temperature.

On the other hand, guide rails 35 are arranged along the inner walls on both sides of the furnace body 1 and these guided endless belt conveyors 36 are laid.

The upper surface of the belt conveyor 36 is located at the article entrance 2
And is guided to descend at the article exit 33,
The height He when passing through the furnace body 1 is set to He ≧ Hb = Hc so as to be at the same level or higher than the heights Hb and Hc of the lower edge of the shield plate 20 and the upper edge of the exhaust port 21. is there.

The belt conveyor 36 moves slowly in the direction of arrow A, and the object 6 to be heated placed on the upper surface passes through the furnace body 1 for a predetermined time. Regardless of the size of the object 6 to be heated, the lower end thereof is adjusted to the height of the upper surface of the belt conveyor 36, and as described above, the condition of Ha <Hb ≦ Hc ≦ Hd is satisfied and the object 6 is effectively heated. 37 is a drive wheel of the belt conveyor 36, 38 is a driven wheel, and 39 is a tension wheel.

In this case, as shown in FIG. 9, since the air inlet 10 is opened on the lower side surface of the furnace body 1, the upper edge height Ha of the air inlet 10 is equal to the upper edge height Hc of the exhaust port 21. It is provided below. When the air inlet 10 opens on the side surface of the furnace body 1, the height comparison with the exhaust port 21 is based on the upper edges of the openings.

This heating furnace also has the same operation and effect as the heating furnace shown in FIG.

[0062]

As described above, in the heating furnace according to the present invention, a heating source is provided on at least one of the side and the top of the furnace body of the natural convection heating furnace, and the heating chamber is provided above the air inlet. The heating chamber can be heated effectively and aggressively using the radiant heat and radiant heat from the heating source, and the heating efficiency is improved by natural convection in the heating chamber. Energy can be quickly obtained over the entire longitudinal direction of the furnace, the start-up heating characteristics at start-up can be improved, the heating chamber can be stabilized at an early stage, and the energy used for the heating source (fuel and electricity costs) Can be saved. The heating source is provided above the air inlet, and new air flows smoothly and smoothly from the air inlet into the heating chamber by the upward flow of the air heated by the heating source. Since there is no need to separately install a heating source below or below the furnace body, the lower part of the furnace body is free, and the degree of freedom in design is improved.

Even if the inside of the furnace is directly heated by a heating source, since the heating is a gentle heating effect based on natural convection and effectively using radiant heat or radiant heat, a large fluctuation is generated on the heating surface in the furnace. No streaks occur along the furnace longitudinal direction, and a stable and uniform temperature heating chamber can be rapidly obtained. Further, since the upper edge of the air inlet corresponding to the heating source is formed below the upper edge of the air outlet and the article inlet / outlet, it is effective for the hot air heated by the heating source to flow backward and flow out of the air inlet. Can be prevented. The hot air heated by the heating source rises in temperature and spreads laterally (furnace longitudinal direction or width direction) from the top of the heating chamber of the furnace body, and is filled in the heating chamber,
When this hot air is cooled by the object to be heated, the temperature drops and drops due to natural convection, and is discharged from the exhaust port (including the article entrance and exit). Therefore, the heating chamber in the furnace is constantly metabolized, and In the effective heating space, a uniform heat distribution without fluctuation of the heating surface can be obtained throughout.

Further, since the heating source is arranged intensively between the exhaust ports provided apart from each other in the longitudinal direction of the furnace, the maintenance work of the heating source can be managed collectively, and the workability of the maintenance check is improved. On the other hand, a belt conveyor can be provided on the lower floor surface, and the degree of freedom in design can be increased.

When the lower part of the furnace body is opened, access to the inside of the heating furnace from the lower part of the furnace body becomes easy, and the maintenance work can be performed more efficiently and efficiently. The lower portion is opened, so that the degree of freedom in design can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a basic principle of a heating furnace according to the present invention.

FIG. 2 is a sectional view showing a practical embodiment of the heating furnace according to the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line III-III of FIG. 2 and showing another example.

FIG. 5 is a sectional view showing a first modification of the heating furnace according to the present invention.

FIG. 6 is a sectional view showing a second modification of the heating furnace according to the present invention.

FIG. 7 is a sectional view showing a third modification of the heating furnace according to the present invention.

FIG. 8 is a sectional view showing a fourth modification of the heating furnace according to the present invention.

FIG. 9 is a sectional view showing another practical example of the heating furnace according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace body 2 Article inlet 3 Article outlet 4 Heating chamber 5 Conveyor line 6 Heated object 7 Pit 8 Heating means 9 Infrared lamp 10 Air inlet 13 Air collecting hood 14 Exhaust cylinder 20 Shield 21 Exhaust port 25 Adjustment plate 29 Burner device Reference Signs List 30 air curtain device 31 blow-out duct 35 guide rail 36 belt conveyor

Claims (3)

(57) [Claims] In a natural convection type heating furnace provided with a conveyor line for supporting an object to be heated conveyed in a heating chamber of a furnace body having an article entrance, heating is performed on at least one of a side part and a top part of the furnace body. A source is provided above the air inlet so as to be exposed in the heating chamber, and an exhaust port is formed in a lower portion of the heating chamber and at a position away from the heating source by a required distance in the furnace longitudinal direction. The entrance is located below the lower end of the object to be heated which is conveyed in the heating chamber of the furnace body, and the entrance is below the exhaust port and the upper edge of the article entrance, at least the air inlet corresponding to the heating source. A heating furnace having an upper edge. 2. The heating furnace according to claim 1, wherein the heating source is intensively arranged between the exhaust ports provided apart from each other in the furnace longitudinal direction on the way from the article inlet to the article outlet. 3. The heating furnace according to claim 1, wherein a lower portion of the furnace body is opened.