JP2875971B2 - Tact transfer type baking oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a baking method for baking a metal workpiece (hereinafter referred to as a "work") coated with an electrostatic powder paint or a water-based paint which is tact-conveyed by a power and free type overhead conveyor. About the furnace.

[0002]

2. Description of the Related Art In electrostatic powder coating, a workpiece conveyed by a grounded conveyor is subjected to necessary pretreatments such as degreasing, pickling, and chemical conversion, and then a high voltage is applied using an electrostatic gun. The powder coating is passed between the electrodes and the charged powder coating is sprayed, a powder layer is formed by electrostatic attraction, and this is heated to cause a melting or thermosetting reaction to form a resin film. is there.

In designing such a coating line,
First, since the work size and processing capacity are set in advance,
The hanger pitch and the conveyor speed or tact time are determined based on this. The length of each processing apparatus is determined so as to satisfy the required processing time according to the processing conditions of each process.

[0004] In this case, speaking about the length of the baking furnace, management
When a normal continuous conveyor is used to facilitate the solution
To explain, the conveyor speed in electrostatic powder coating is 1
Assuming that the baking temperature is 180 ° C. and 10 minutes at ２2 m / min, when the workpiece is passed through a furnace in which the atmosphere is set at 190 ° C., the temperature change of the material surface is, for example, as shown in FIG.
The temperature rise curve is as follows. That is, in order to maintain the temperature of the work at 180 ° C. for 10 minutes, it takes 20 to 40 minutes to pass through the furnace including the rise time. Therefore, the length of the furnace is determined if the conveyor speed is 1 m / min. 20-4
0 m. Since the rise time greatly changes depending on the thickness of the work, thick furnaces have a longer furnace length.
As described above, increasing the baking capacity requires a longer furnace length, which is not preferable in terms of space and heat efficiency.

In order to shorten the furnace length as much as possible for the required capacity and to use the furnace effectively, it is conceivable to reduce the hanger pitch and reduce the conveyor speed. FIG. 5 shows the relationship between how the work is hung and the hanger pitch. FIG. 3A shows the outline of the work 1 and shows a rectangular parallelepiped having three sides A, B, and C, where A>B> C. FIGS. 3B, 3C, and 3D respectively show the hanger pitches P1, P2, P3 and the conveyor speed V1, when C, B, and A of the three sides of the work are set as the conveying direction of the conveyor 2. V
2 and V3. Since C <B <A, P1 <P
2 <P3 and V1 <V for the same capacity (heating time)
2 <V3, and the furnace lengths L1, L2, L3 are L1 <L2 <
It turns out that it becomes L3.

As described above, when one side C shown in FIG. 5A is smaller than the other sides A and B, that is, when the work has a flat shape, the flat surface is in the transport direction. If they are densely arranged so as to be perpendicular to the furnace, the furnace length is reduced. on the other hand,
Such an arrangement of workpieces is a very disadvantageous condition for electrostatic coating. In other words, the lines of force of the electric field formed between the electrode of the electrostatic gun and the work are difficult to reach inside the space between the flat surfaces of each work. Occurs. A conveying method for solving this problem is described in Japanese Patent Application Laid-Open No. Hei 4-224461. This means that the work supported and transported by the transport device with the longitudinal direction along the transport direction for the processing step such as painting can be changed by switching the switching device of the transport device just before the entrance of the baking furnace. After changing the direction with respect to the conveyance direction, the work is put into the baking furnace from the entrance, the baking is performed by moving the inside of the furnace at a short pitch, and the work coming out from the exit is transferred to the transfer device switching device. By switching, the direction is returned so that the longitudinal direction is along the transport direction.

[0007]

By using the above-described transfer method, the furnace length can be effectively shortened for a work having a flat shape, but the effect can be reduced for a work having no large difference in the sizes of the three sides A, B, and C. Becomes smaller. Another factor for shortening the furnace length is a temperature rise curve shown in FIG. As shown in the figure, the rise time depends on the thickness of the workpiece, but is usually longer than the required baking temperature holding time. Therefore, FIG.
As shown in (2), if the temperature rise is made faster, the passage time in the furnace, that is, the furnace length can be shortened.

In order to speed up the start-up in an atmosphere furnace, the set temperature of the furnace may be increased, but in the case of paint baking, the difference between the appropriate baking temperature and the heat deterioration temperature is relatively small, so that the setting can be freely performed. I can't raise it. As a method of heating regardless of the ambient temperature, there is radiant heating using infrared rays or far infrared rays. In that case, the radiation directly raises the temperature of the surface of the work rapidly, so that the rise time is shortened.

[0009] From the above, it can be assumed that the effect will be extremely high if the workpiece is transported densely in the furnace with the direction of the workpiece tilted from the transport direction and a radiant heater is provided in front of the furnace body. However, in the case of radiant heating, it is necessary to directly irradiate the surface of the work from a heat source disposed on the side of the furnace body, and in the above-described transfer method, a shadow portion is generated due to the overlap of the works, so that uniform heating cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made for the above-described reason, and an object of the present invention is to use both radiant heating and atmospheric heating in baking such as electrostatic powder coating or spray coating of a water-based paint, and to use a furnace. Another object of the present invention is to provide a coating baking furnace in which the work is densely conveyed by changing the inclination of the work in the longitudinal direction with respect to the conveying direction within the furnace, thereby shortening the furnace length.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a baking furnace for baking a painted workpiece tact-conveyed by a power and free conveyor, and an object of the present invention is to provide a baking furnace. A front door is provided, which has an entrance door which takes in and opens a painted work to be tact-transferred in the longitudinal direction of the work, and arranges far-infrared heaters on both side surfaces in the transfer direction to preheat the work. Preheating zone and changing the inclination of the work in the longitudinal direction with respect to the transfer direction to shorten the hanger pitch in the transfer direction and allow the work to pass through the furnace, and return the longitudinal direction to the transfer direction again just before the exit of the furnace body. And a hot-air circulation heating zone through which an exit door passes.

[0012]

In the preheating zone, the longitudinal direction of the work is the transport direction, and there is no overlap of the work viewed from the side, and the irradiation efficiency is high. In addition, since the temperature of the surface rises quickly, irradiation of one tact of conveyance is often sufficient, and the length of the preheating zone can be short. In addition, since the work that has exited the preheating zone is inclined in the longitudinal direction from the transport direction via the switching device and passes through the hot air circulation heating zone with the pitch shortened,
The total length of the furnace body is shortened in combination with the shortening of the heating time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view for explaining a basic layout configuration. The furnace body 3 includes a preheating zone 4, a switching unit 5, a hot air circulation heating zone 6, and a switching unit 7 from the forefront in the transport direction. At the front of the preheating zone 4 is provided an entrance door 8 which automatically opens and closes in accordance with the cycle of the tact transfer of the work 1. On both sides, a far-infrared heater 41 formed in a planar shape for irradiating the stopped work 1 from both sides. Is provided.
The heater 41 can move the radiation surface back and forth, and can adjust the temperature rising rate according to the shape of the work. In the hot air circulation heating zone 6, a normal gas burner combustion gas circulation type hot air furnace is used.

FIG. 2 shows the configuration of the conveyor of the invention used in the present invention. The conveyor 2 is composed of a power line 10 for driving a drive chain 9 and a free line 12 for guiding a trolley for transporting a hanger 11, and the drive chain 9 has transmission projections 13 suspended at appropriate intervals. . Two hanger arms 1 standing upright on the hanger 11
The trolleys 15A and 15B are rotatably connected to the trolleys 15A and 15B, respectively, and the trolleys 15A and 15B are rotatably connected to the trolley 16A at the front or the trolley 16B at the rear by connecting rods 17A and 17B, respectively. A pair of trolley devices 18A and 18B are configured. The trolley 16A at the forefront end has the transmission projection 1
The passive projection 19 which can swing up and down with respect to 3 and can be disengaged and disengaged.
Is provided.

FIG. 3 shows how the longitudinal direction of the work is changed by using such a conveyor. The work 1 conveyed along the free line 12 in the longitudinal direction is detected just before the branch point 20 of the free line 12, and the switching piece 22 of the switching device 21 at the branch point 20 is moved to the main path 12B side. Trolley device 1 at the front
8A enters the branch path 12A. And the trolley device 18
By detecting that A has completely entered the branch path 12A, the switching piece 22 moves to the branch path side, and the trolley device 18B at the rear enters the main path 12B. In this way, when the front and rear trolley devices 18A and 18B enter the parallel branch path 12A and main path 12B, respectively, the hanger 11 is inclined at a certain angle with respect to the transport direction. In this state, the trolley device 1
8A is transferred to a second drive chain via a transfer device (not shown), and is conveyed at a reduced pitch.

To return the inclination of the work 1 to the original position, the work 1
At the end of the parallel branch path 12A, the hanger 11 is passed to the third drive chain, and when the work 1 is detected just before the merging point 23, the switching device 24 moves the switching piece 25 to the main path 12B side. The trolley device 18A is connected to the main path 12
B, and by detecting that the trolley device 18A has completely entered the main path 12B, the switching piece 25 is switched to the branch path 12B.
Switching to the A side, the trolley device 18B moves on the main path 12B as it is. Thus, the front and rear trolley devices are located on a straight line, and the hanger is in a state where the longitudinal direction is along the transport direction.

In the transfer method described above, another drive chain is used to shorten the pitch of the inclined work 1. However, the hanger pitch of the branch portion is set short in advance, and the traveling hanger is set. The tip trolley 16A may detect the position of the preceding hanger, detach the passive projection 19, and stop.

Next, returning to FIG. 1, the operation of the baking furnace according to the present invention will be described. Work 1 that has finished painting in the previous process
When it reaches a predetermined position in front of the furnace body 3 by the continuous feed conveyor, it is detected by a detector, and its drive unit is transferred to a drive chain 9 that drives the inside of the furnace body 3 to carry out tact transfer. First, after the entrance door 8 on the front of the furnace body 3 is opened, the hanger 11 travels a predetermined distance (time) and enters the preheating zone 4. When the hanger 11 stops at a predetermined position, the entrance door closes and the work 1 is moved for a predetermined time. Receive infrared radiation. Then, the total time of these series of operations is one tact.

The work 1 preheated in the preheating zone 4 enters the switching section 5 at the next tact, stops at the entrance of the hot air circulating heating zone 6 with the longitudinal direction inclined at a predetermined angle with respect to the conveying direction via the branch point 20. In the heating zone 6, the hanger pitch is short and densely arranged in advance. Then, when the work that has finished baking and has stopped outside the furnace body 3 leaves the predetermined stop position, the exit door 26 on the rear surface of the furnace body is opened, and the work stopped at the end stop position of the heating zone 6. Passes through the switching unit 7, is returned in the transport direction in the longitudinal direction at the merging point 23, and is carried out to the stop position outside the exit door 26.
Subsequently, each work in the heating zone 6 advances to the position where the preceding work has stopped, and stops.

An example of shortening the baking furnace by the above operation will be specifically described. 5A, the work size is A: 3 m, B: 1.8 m, C: 0.6 m, the baking conditions are 180 ° C., 10 minutes, and the baking capacity is 2.5 minutes / hanger. I do. In this case, the hanger pitch is set to 3.6 m in the preheating zone 4 and 1.26 m in the heating zone 6 with A being the longitudinal direction. If the furnace passage time required without preheating is 35 minutes and if the far-infrared heater 41 performs preheating for 2 to 2.5 minutes, the furnace passage time can be 25 minutes. , Residence time in preheating zone 4 2.5
The number of hangers retained in the furnace body 3 with one minute as one tact is 10 (9 of them are heating zones), and thus the furnace length is 3.6 m + 1.26 m × 9 = 15 m.

On the other hand, the furnace length without the inclined conveyance is 3.6 m × 10 = 36 m, and the number of stay hangers without the preheating is 35 min / 2.5 min = 14. 3.6 for a normal baking furnace without preheating or tilting
m × 14 = 50.4 m. Although the numbers given in the above examples are of course different depending on the type of work and the baking conditions, it can be understood that the synergistic effect is extremely large due to the preheating by radiant heating and the inclined conveyance.

[0022]

As described above, according to the tact transfer type coating baking furnace of the present invention, for the same baking ability, the baking time by the far-infrared heater can be reduced, and the inclined transfer in the heating zone can be achieved. The furnace length can be remarkably shortened as a synergistic effect with the increase in the density of the furnace. This also reduces the size of the furnace, increases thermal efficiency, increases economy, and saves equipment space.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conveyor used in the present invention.

FIG. 3 is a diagram for explaining the operation of the conveyor.

FIG. 4 is a diagram showing a relationship between a passage time in a furnace and a work temperature.

FIG. 5 is a diagram for explaining a relationship between a work hanging method and a hanger pitch.

FIG. 6 is a diagram showing a relationship between a rise time and a passage time in a furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work 2 Conveyor 3 Furnace body 4 Preheating zone 5, 7 Switching part 6 Hot air circulation heating zone 8 Entrance door 9, 91, 93 Drive chain 10 Power line 11 Hanger 12 Free line 12A Branch path 12B Main path 13 Transmission projection 14A, 14B Hanger arm 15A, 15B, 16A, 16B Trolley 17A, 17B Directly connected rod 18A, 18B Trolley device 19 Passive projection 20 Branch point 21, 24 Switching device 23 Merging point 26 Exit door 41 Far infrared heater

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-100422 (JP, A) JP-A-3-127662 (JP, A) JP-A 5-293422 (JP, A) 47995 (JP, A) JP-A-1-139169 (JP, A) JP-A-4-224461 (JP, A) JP-A-1-95282 (JP, U) JP-A-3-98975 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B05C 7/00-21/00 F27B 9/10 F27B 9/30

Claims (3)

(57) [Claims] An inlet door is provided at a front portion of a furnace body for taking in and opening a painted work to be tact-transferred in a longitudinal direction of the work, and far-infrared heaters are arranged on both side surfaces in the transfer direction. By setting the preheating zone for preheating the work and changing the inclination of the work in the longitudinal direction with respect to the transfer direction, the hanger pitch in the transfer direction is shortened and passed through the furnace, and before the exit of the furnace body, A hot-air circulation heating zone in which the longitudinal direction is returned to the transport direction again and the exit door is passed through the tact transport-type coating baking furnace. 2. The tact transfer type coating baking furnace according to claim 1, wherein the preheating zone preheats one workpiece stopped therein. 3. The tact transfer type paint baking furnace according to claim 1, wherein the far-infrared heater is disposed so as to form a radiation surface facing both side surfaces of the work, and an irradiation distance is variable.