JPS6316673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a natural convection type heating furnace that heats an article while passing through the furnace.

[Technical background of the invention and its problems]

In a heating furnace, the object to be heated is heated by introducing hot air, such as combustion gas from a gas burner, into the furnace.
Since it is necessary to constantly supply a large amount of hot air, there is an equal amount of exhaust gas, and the thermal efficiency of the heating furnace is determined by how much heat calories are carried out by the exhaust gas. One preferred method is to sequentially introduce hot air into a furnace with an upside-down container.
There is one in which low-temperature gas that has fallen due to natural convection overflows from the bottom of the furnace body. Thermal efficiency is high due to the mechanism in which high-temperature hot air always accumulates in the upper part of the furnace body and is discharged from the cold gas.

Specific heating furnaces using this natural convection method are described in Japanese Patent Publications No. 58-12513 and Japanese Patent Publication No. 42225-1987, both of which were invented by the same applicant.
The latter is shown in FIG. In a heating furnace equipped with a conveyor line d for supporting articles e conveyed to a nearly sealed furnace body a having entrances and exits b and c for articles e, a burner device g is installed in the lower floor f of the furnace body a. In addition, the upper edge positions of the article entrances and exits b and c are set at the same level as the floor level of the lower floor f section or at a slightly higher level than the floor level f. As a result, the gas with the lowest temperature is discharged from the ports b and c, and the furnace is filled with hot air of higher temperature, efficiently heating the articles passing through.

However, although the heating furnace of the above invention is suitable for effectively using the entire cross-sectional area of the furnace body, it is difficult to install burners and belt conveyors on the lower floor surface, and maintenance work may become difficult. Ta.

[Purpose of the invention]

In view of the above points, this invention further improves and streamlines a heating furnace with high thermal efficiency by utilizing natural convection, facilitates the installation of heat sources and conveyance means, provides excellent maintainability, saves fuel, and provides safety. The purpose of this invention is to provide a heating furnace with high performance.

[Summary of the invention]

In order to achieve the above object, a natural convection type heating furnace according to the present invention is configured as follows.

The furnace body is shaped like a straight or arbitrarily curved horizontal tunnel, and the upper half of the inlet and outlet are covered with shielding plates, and a means for conveying the heated material passes through the furnace body, and hot air is supplied to the inside of the furnace. A heat source such as a gas burner is installed, and the conveying means is raised and lowered at the inlet and outlet portions so that the lower end of the heated object to be conveyed passes through the furnace body while being positioned at the same level or above the lower edge of the shield plate. In addition, the upper edge of the air inlet of the heat source is located below the lower edge of the shield plate, and exhaust ports for venting to the atmosphere are arranged at least at the entrance and exit of the furnace body, and the upper edge of each exhaust port is They are all set at the same height so that they are at the same level or above the lower edge of the shield plate and at the same level or below the lower end of the object to be heated as it passes through the furnace body, and below the exhaust port inside the furnace body. It is characterized by forming an air layer on the side, and installing an air collection hood connected to the lower end of the exhaust pipe above the outside of the furnace body at the exhaust port.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed explanation will be given below with reference to figures showing embodiments of the present invention.

FIGS. 1 and 2 show the basic configuration.

The furnace body 1 has a horizontal tunnel shape, and its longitudinal shape is straight or arbitrarily bent. At the inlet 2 and outlet 3 of the furnace body 1, a shielding plate 4 is formed by deeply bending the upper wall downward, and closes the upper halves of both the ports 2 and 3. A conveyance line 5 is installed inside the furnace body 1,
The object to be heated 6 is passed from the inlet 2 to the outlet 3. The conveyance line 5 is formed so that it rises at the inlet 2 part and descends at the outlet 3 part so that the object to be heated 6 passing therethrough passes through the upper half position in the furnace body 1. A layer is formed.

Further, a heat source is installed at the bottom of the furnace body 1. A gas burner 7 or the like is used as a heat source, and the setting is such that hot air is introduced by natural convection without being forced. Further, an exhaust port 8 for opening the inside of the furnace body 1 to the atmosphere is provided at least near the inlet 2 and the outlet 3, and if necessary at a suitable location in the center. An air collection hood 10 connected to the lower end of the exhaust pipe 9 is open above the exhaust port 8 outside the furnace. 9a shows a forced exhaust fan provided in the exhaust pipe 9.

In the above configuration, the height of the upper edge of the air inlet that supplies air to the gas burner 7 is Ha, the height of the lower edge of the shielding plate 4 is Hb, the height of the upper edge of the exhaust port 8 is Hc, and the height of the upper edge of the exhaust port 8 is Hc. Letting Hd be the height of the lower end when passing through the interior, the setting is made to satisfy the condition Ha<Hb≦Hc≦Hd.

As a result, the hot air generated by the gas burner 7 is
It rises and fills the furnace body 1, and due to natural convection, the lower temperature portions successively exceed the exhaust port 8 and overflow into the atmosphere. Since the exhaust port 8 is not directly connected to the exhaust pipe 19, the exhaust port 8 is not given a chimney effect. Therefore, the hot air is not forcibly sucked out from the exhaust port 8, and the high-temperature hot air supplied by the gas burner 7 accumulates in the upper part of the furnace body 1, causing natural convection to flow through the object to be heated. This will allow efficient heating. Therefore, the best value of thermal efficiency can be obtained, and the temperature inside the furnace body 1 can be easily adjusted by controlling the amount of hot air supplied from the gas burner 7. Further, the temperature distribution within the furnace body 1 can be maintained uniformly.

In addition, since an air layer is formed below the exhaust port 8 of the furnace body 1, when the object to be heated is conveyed inside the furnace body 1, hot air containing the solvent escapes to the air layer and can be diffused. The formed air layer forms a barrier layer between the heat source such as the gas burner 7 and the solvent such as thinner contained in the hot air, so there is no risk of explosion and the safety of the furnace can be improved. can.

Next, FIG. 3 shows a practical embodiment.

A shielding plate 14 is provided at the outlet 12 and the outlet 13 of the furnace body 11 to cover the upper half thereof, and an exhaust port 18 is arranged in the center of the furnace body 11 as required. The height Hb of the lower edge of the shielding plate 14 and the height Hc of the upper edge of the exhaust port 18 are set to Hb=Hc. That is, the inlet 12 and outlet 13 are used as one of the exhaust ports. Therefore, entrance 1
2. An exhaust pipe 19 is arranged above the outlet 13, and an air collection hood 20 connected to the lower end thereof is opened. A gas burner 17 is installed on the lower floor of the furnace body 1.

Next, guide rails 21 are arranged along both inner walls of the furnace body 11, and an endless belt conveyor 22 guided by the guide rails 21 is installed. The upper surface of the belt conveyor 22 is guided to rise at the inlet 12 and descend at the outlet 13, and the height He when passing through the furnace body 11 is equal to the lower edge of the shield plate 14 and the upper edge of the exhaust port 18. He≧Hb=Hc is set so that He≧Hb=Hc is located at the same level as or above the heights Hb and Hc.
The belt conveyor 22 slowly moves in the direction of the arrow, and the object to be heated 16 placed on its upper surface passes through the furnace body 11 over a predetermined period of time. Regardless of the size of the heated object 16, the lower end is aligned with the height of the upper surface of the belt conveyor 22, and as described above, Ha<Hb≦Hc≦.
It satisfies HD conditions and is heated effectively. 23 is a drive wheel of the belt conveyor 22, 24 is a driven wheel, and 25 is a tension wheel.

Note that in the above configuration, the exhaust port 18 may be arranged at the inlet 12 and outlet 13 portions.

FIG. 4 shows another embodiment.

The structure in which shielding plates 34 protrude from the inlet 32 and outlet (not shown) of the furnace body 31 is the same. The height Hb of the lower edge of the shielding plate 34 and the height Ha of the upper edge of the air supply port 37a of the gas burner 37 are set to have a relationship of Ha<Hb. An adjustment plate 41 that can be adjusted up and down is attached to the exhaust port 38, and by adjusting the adjustment plate 41, the exhaust port 3
8. The height of the upper edge can be changed. Hb≦Hc at the lowest position. The conveyor line 42 is constructed along the upper wall of the furnace body 1, and the objects to be heated 36a and 36b are suspended and moved by the conveyor line 42. Since the height of the lower end is different when suspending and heating a small heated object 36a and when heating a large heated object 36b, adjust the adjustment plate 41 up and down to adjust the height between the upper edge of the exhaust port 38 and the lower end of the heated object. Match the heights and optimize the relationship Hb≦Hc≦Hd.
Fuel consumption can be reduced to the minimum necessary depending on the size of the object to be heated.

In addition, in the case where the inlet and outlet are exhaust ports, the height of the lower edge of the shielding plate can be adjusted up and down.

The heating furnace described in each example introduces hot air into the furnace body with the container facing down, and uses natural convection to constantly fill the upper part of the furnace body with high-temperature hot air to heat the object to be heated in this high-temperature part. The exhaust port and other parts are rationally arranged so that heating can be carried out effectively using the minimum amount of thermal energy required, and the fuel consumption rate is greatly improved. In this type of heating furnace that uses hot air, circulating hot air furnaces are mainstream in order to effectively utilize heat energy, but compared to these, special burners, blowers, or ducts can be omitted, and the structure is simpler. By using this method, equipment costs and costs can be reduced, and since natural convection is used, metabolism is carried out effectively and impurity molecules are constantly discharged, preventing them from contaminating the paint film of the heated object during baking painting. Moreover, since the flow rate of hot air is gentle, the heating condition is gentle and uniform, which improves the quality of the product.

〔Effect of the invention〕

As described above, the heating furnace according to the present invention is
A natural convection system is adopted, in which the lower end of the object to be heated is guided through the furnace body while being positioned above the lower edge of the shield, while the air intake from the heat source is placed below the lower edge of the shield. The upper edge of the exhaust port for venting to the atmosphere, located at least at the entrance and exit of the furnace body, is located above the lower edge of the shield and below the lower end of the object to be heated, so that natural convection can be utilized. The heated object can be effectively heated by baking and painting, etc., and the heating condition is gentle and uniform, and the quality of the product can be improved.

In addition, since an air layer is formed below the exhaust port inside the furnace body, it is easy to install heat sources such as burners and conveyance means on the bottom surface of the furnace body, improving their maintainability. Since an air barrier is formed between the heat source and the hot air containing solvents such as thinner, it effectively prevents solvents such as thinner from igniting, prevents explosions in the heating furnace, and improves safety. can be improved.

In addition, since the air intake port is located below the lower edge of the shield plate and the upper edge of the exhaust port, backflow of air from the air intake port and exhaust port is prevented during combustion in a heating furnace that uses the natural convection method. Things are heated effectively and stably.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of a heating furnace showing an embodiment of the present invention, FIG. 2 is a longitudinal sectional front view of the heating furnace, and FIG.
FIG. 4 is a side view of a heating furnace showing another embodiment, FIG. 4 is a longitudinal sectional side view of a part of the heating furnace, showing another embodiment, and FIG. 5 is a longitudinal sectional view of an example of a conventional heating furnace. FIG. 1, 11, 31... Furnace body, 2, 12, 32...
Inlet, 3, 13... Outlet, 4, 14, 34... Shield plate, 5... Conveyance line, 6, 16, 36a, 36
b... Heated object, 7, 17, 37... Gas burner, 8, 18, 38... Exhaust port, 10, 20, 4
0...Air collection hood, 22...Belt conveyor, 4
1...adjustment plate, 42...conveyor line.

Claims (1)

[Scope of Claims] 1. A furnace body in the form of a straight or arbitrarily curved horizontal tunnel, the upper half of which is covered with a shield plate at the entrance and exit, and a means for conveying a heated object passing through the furnace body; A heat source such as a gas burner that supplies hot air inside the furnace is installed, and the conveying means is raised and lowered at the inlet and outlet portions so that the lower end of the object to be conveyed is located at the same level or above the lower edge of the shield plate. The heat source is set so that the upper edge of the air intake port is located below the lower edge of the shield plate, and an exhaust port for opening to the atmosphere is provided at least at the entrance and exit portion of the furnace body. The upper edge of each exhaust port is at the same level or above the lower edge of the shield plate, and all are at the same height so that they are at the same level or below the lower edge of the object to be heated as it passes through the furnace body. Set it to
forming an air layer below the exhaust port in the furnace body;
A natural convection heating furnace characterized in that an air collection hood connected to the lower end of the exhaust stack is installed above the outside of the furnace body at the exhaust port. 2. The heating furnace according to claim 1, wherein the inlet and outlet of the furnace body below the shield plate function as exhaust ports. 3. Claims characterized in that a belt-type conveyor for carrying objects is installed as a conveying means, and its top surface height when passing through the furnace body is set at the same level as or above the upper edge of the exhaust port. The heating furnace according to item 1 or 2. 4. The heating furnace according to claim 1 or 2, characterized in that a conveyor line for suspending and transporting objects is installed as a conveyance means, and the upper edge of the exhaust port can be adjusted up and down.