JPS6110156Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a tunnel furnace that promotes temperature rise by utilizing the principle of air conveyance through an air jet flow.

BACKGROUND OF THE INVENTION In various product manufacturing lines, articles to be treated are continuously or batchwise passed through or charged into a tunnel furnace maintained at a high or medium-high temperature, and then subjected to drying or heat treatment. In such a tunnel furnace, an upward flow of high-temperature air occurs, resulting in a temperature difference between the upper and lower parts of the furnace. For this reason, there was a tendency for uneven drying to occur at the top and bottom of the product in the oven.

Conventionally, in order to reduce the difference in the temperature inside the furnace, a measure has been taken to blow hot air from below the furnace to the lower part of the product 1, as shown in FIG. That is, a hot air blowing duct 3 is provided on both sides of the lower part of the tunnel furnace 2, and hot air is blown downward from the blowing outlet 4 attached to the blowing duct 3 toward the product 1 passing through the furnace. We tried to minimize the difference in surface temperature between the top and bottom. However, in this case, an extra amount of heat is consumed and the extra heat collects in the upper part of the furnace, which is uneconomical.

The present invention was developed with the aim of solving this problem, and is an extremely economical system that moves high-temperature air from above downward by means of air conveyance using a high-speed air jet flow as an air conveyance means. As shown in the embodiment of the drawings, the temperature accelerator is built into the furnace, and in the tunnel furnace 2 for drying or heating articles, the blowing direction is directed downward or diagonally downward on both sides of the upper part of the furnace. Small-diameter nozzles 5 are arranged in a row in the tunnel direction, and ducts 6 and blowers 7 are installed to supply hot air to each small-diameter nozzle 5. at least 5
The feature is that the ambient air (the air existing above the furnace) is transported below the tunnel furnace at an air volume greater than 100 ml.

FIG. 2 is a sectional view of the tunnel furnace of the present invention, in which ducts 6 for supplying hot air are installed in the tunnel direction on both sides above the furnace.
2 shows an embodiment in which a small-diameter nozzle 5 is installed diagonally downward. By force-feeding hot air into this duct 6, a small-diameter nozzle 5 blows out a high-speed air jet flow with a small amount of air. This low-volume, high-speed air jet flow moves downward while attracting the surrounding air, and as it moves downward, the wind speed decreases, but as it combines with the attracted air, the air flow increases and descends, causing the air to reach the floor. When the wind reaches the surface, the wind speed decreases to about 0.7m/s. This air jet flow transports the induced air below the tunnel furnace in an amount more than 5 times, or in some cases about 10 times, the amount of air blown out. As a result, the high-temperature air in the upper layer of the tunnel furnace can be conveyed to the lower layer, reducing the difference in surface temperature of objects placed in or passing through the furnace, resulting in uneven drying, etc. This inconvenience can be avoided.

Figure 3 shows a specific example in which the present invention is applied to a tunnel drying furnace for drying painted products.
The air is sent to the dark red furnace C and then to the air seal section D, and the airflow conveyance according to the present invention is carried out in the zone of the dark red furnace C. That is, in this dark red furnace C, a duct 6 similar to that shown in FIG. 2 is arranged along the tunnel direction on both sides of the upper part of the furnace, and downward small-diameter nozzles 5 are arranged in a row at approximately equal intervals in this duct 6. . Hot air is forced into this duct 6 by a blower 7. In this example, a part of the hot air manufactured for use in the hot air stove B is used as the hot air. That is, the hot air produced by the burner furnace body 8 is sent to the blow-off duct 9 of the hot-blast stove B, but a part of it is sent to the blower 7 and further pressurized by the blower 7 before being sent to the duct 6. The high temperature air existing in the upper layer of the dark red furnace C is turned into a dark red by blowing it out downward from the small diameter nozzle 5 as a small air volume and high speed air jet, in the same way as explained in FIG. 2. Transfer to the lower part of furnace C. In addition, in FIG. 3, 10 is a suction duct provided at the upper position of hot air stove B, and 11 is
12 is a circulation fan, 12 is a burner fan, and 13 is an exhaust port.In the air seal portions A and D, air curtains (not shown) are formed to circulate and utilize the air in the furnace.

When the tunnel drying oven shown in Fig. 3 is applied to dry painted automobile bodies, there are two cases in which the upper air is transported to the lower layer by the high-speed air jet flow according to the present invention in a dark red oven. FIG. 4 plots the change in the surface temperature of the lower part of the automobile body in the case of no damage. As seen in FIG. 4, it is clear that by applying the small diameter nozzle of the present invention in the dark red furnace, the surface temperature of the lower part of the product increased and the temperature increase was accelerated.

As described above, according to the present invention, the equipment is simple and inexpensive because air is used as a means for conveying high-temperature air staying in the upper part of the furnace to the lower part. Moreover, it is easy to apply to existing furnaces, and the conventional problem of temperature differences between the top and bottom of products inside the furnace can be easily and economically solved.
The overall rise in product temperature can be accelerated. In addition, if the furnace is equipped with a hot air stove, as in the example shown in Figure 3, the air volume of the circulation fan can be lowered by this invention if the rise in product temperature is allowed as before. There are also advantages.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional tunnel furnace, FIG. 2 is a sectional view of a tunnel furnace according to an embodiment of the present invention, FIG. 3 is an overall view of a tunnel drying furnace according to an embodiment of the present invention, and FIG.
The figure is a drying temperature change diagram comparing the drying conditions of the tunnel furnace according to the present invention and a conventional furnace. 2...Tunnel furnace, 5...Small diameter nozzle, 6...
...Duct, 7...Blower, 8...Burner furnace body.

Claims (1)

[Scope of utility model registration request] In a tunnel furnace for drying or heating articles, small-diameter nozzles with blowing directions directed downward or diagonally downward are arranged in a row in the tunnel direction on both sides of the upper part of the furnace, and hot air is supplied to each small-diameter nozzle. A tunnel furnace equipped with a duct and a blower, and configured to transport ambient air in an amount at least five times the amount of air blown out below the tunnel furnace by high-speed airflow from each small-diameter nozzle.