JPS629836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement in a baking drying oven for painted or printed containers such as cans.

When a container such as a can is painted or decoratively printed and then dried and baked, it has conventionally been common to use a baking drying oven known as a "pin open" oven. Painted and printed cans move through the high-temperature atmosphere of this furnace while being hung on pins. This type of furnace had drawbacks such as poor heating efficiency as the can was heated only from the surface, and the pins came into contact with the inner surface of the can, making it unusable for drying and baking paint on the inner surface.

On the other hand, recently, an inlet hole has been placed in a part of the opening of the can that is placed with the opening facing downward in the furnace with the high temperature atmosphere. A type of baking drying furnace was put into practical use in which the liquid flows into the can body from the inside and is then sucked in through the intake hole.
(For example, Japanese Patent Application Laid-Open No. 52-143548.) In this type of furnace, the cans are heated from both the inside and outside by a high-temperature atmosphere, so the heating efficiency is extremely high, and during drying and baking, there is no contact with the conveyor belt. It has many advantages, such as being able to paint and dry and bake the inside and outside surfaces at the same time, since it only covers the opening edge of the can.

However, the only thing that holds the can body on the conveyor belt during dry baking is the pressing force due to the difference between the atmospheric pressure inside the furnace and the atmospheric pressure inside the can, which is lowered by suction. For this reason, cans often fall over during transportation due to bending or vibration of the conveyor belt, which is often made of stainless steel or other metal belts. A can that is taller than its diameter has a higher center of gravity, making this type of failure more likely.

On the other hand, if you try to increase the pressing force by lowering the pressure inside the can, the suction force will naturally increase, causing the airflow to become turbulent and blowing the can over, or the paint on the can surface to be washed away and unpainted. This can cause problems such as unevenness in the film and, in some cases, the paint may run down and the droplets are sucked up and adhere to the inside of the can, so it is not possible to solve the problem by simply increasing the suction power. Ta.

This invention was devised to solve the above-mentioned problems of the prior art, and it prevents cans from falling over while being transported in a baking drying oven, and prevents the paint on the can surface from dripping due to hot air. The object of the present invention is to provide a baking drying oven which can prevent the droplets from adhering to the inner surface of the can, and which bakes and dries the can body container by efficiently circulating hot air between the inside and outside of the can. be.

This invention employs the following technical means to solve the above problems.

That is, the baking and drying oven for can bodies and containers of the present invention comprises a hot air supply chamber, a can body passage chamber, and a hot air recovery chamber,
In the baking drying furnace, the suction nozzle of the hot air recovery chamber sucks and recovers hot air from the can body to be baked and dried, and accordingly, the hot air supplied from the hot air supply chamber flows into the can body. An outer suction nozzle row opening into the can body passage chamber is provided on the outside of the suction nozzle, and the outer suction nozzle row is arranged wider than the can body opening end, and the opening diameter of the suction nozzle of the hot air recovery chamber is equal to the width of the outer suction nozzle row. Larger than the opening diameter of the nozzle, and 1/10 to 1/1/2 of the diameter of the opening end of the can body.
It is characterized by being in the range of 2.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of the baking drying oven of the present invention, taken perpendicular to the conveyor belt. The hot air for heating the can placed on the can body 7 and passing through the furnace is heated by the burner 1, is sent to the hot air supply chamber 3 by the circulation blower 6, and is sent from the hot air blowing nozzle 8. The hot air is ejected to heat the can body, and is sucked through the hot air suction nozzle 9 and circulated. In the figure, 2 is a heating control device, and 15 is an auxiliary recovery nozzle for making the air flow in the can body passage chamber steady.

FIG. 2 is a partially cutaway perspective view of the can body 13 being conveyed over the hot air suction nozzle 9 by the can conveyor belt 7. The can body 13 is conveyed over the hot air suction nozzle 9 by the can body conveyor belt 7, and is a perspective view with a part cut away. The body 13 is connected to the conveyor belt 7
It is placed on top with the opening facing down and transported.

In conventional equipment, it is considered rational to arrange the hot air suction nozzle holes as uniformly and densely distributed as possible facing the can body passage in order to apply uniform treatment to the entire circumference of the can body. Therefore, as shown in FIG. 3, the opening diameter of each nozzle 9 was generally made small, less than 1/10 of the diameter of the opening end of the can.

However, as a result of various experiments, the inventor of the present invention discovered that it is preferable that the aperture diameter of these nozzles be larger as shown in FIG.

The reason for this is thought to be as follows. The operating principle of this type of baking drying oven will be explained with reference to FIG. That is, as described above, the hot air blown out from the hot air supply chamber 3 through the nozzle 8 is sucked through the suction nozzle 9 and circulated. At this time, in the part where the suction nozzle 9 is covered with the can body 13 as shown in the figure,
Due to the negative pressure generated by the circulation blower 6, hot air in the internal volume of the can is sucked into the recovery chamber 5. For this reason, the air pressure inside the can body decreases and the outer suction nozzle 9
The hot air in the can body passage chamber 4 is sucked into the can body through A. At this time, the pressure inside the hot air supply chamber 3 is
P ₁ , the pressure in the can body passage chamber 4 is P ₂ , the pressure inside the can body is
If P ₃ and the pressure in the hot air recovery chamber 5 are P ₄ , then there is a relationship of P ₄ <P ₃ <P ₂ <P ₁ .

If the resistance of the suction nozzle 9 is large, the suction pressure Ps = P ₃ - P ₄ will be large, and even though the negative pressure in the recovery chamber 5 is large, the holding force Ph = P ₂ - P ₃ of the can body 13 will be small. I become confused. Furthermore, as already mentioned, the large suction pressure increases the suction flow velocity, causing problems such as dripping of the coating material.

On the other hand, if the suction nozzle diameter is increased, the suction resistance due to the nozzle decreases, Ps = P ₃ - P ₄ becomes smaller, Ph = P ₂ - _{P 3} becomes larger, and the small collection chamber 5 This negative pressure creates a large holding force for the can body. Experimental results regarding this are shown in FIGS. 6 and 7.

Figure 6 shows the rate of can collapse with respect to the nozzle diameter d when the suction pressure of the nozzle 9 is changed.
In this experimental example, if the conventionally used nozzle diameter d was less than 1/10 of the can diameter, the can collapse rate could not be reduced to zero unless the suction negative pressure was -100 mmAg or more.
If it is set to 0.5D, the collapse rate can be reduced to almost zero with a negative pressure of only -20mmAg.

On the other hand, if we look at the incidence of paint dripping, as shown in Figure 7, when the dry coating amount is 150mg/ ^dm2 ,
If the nozzle diameter d is 0.1D relative to the can diameter D, the occurrence rate will be zero when the suction negative pressure is -65mmAg or less.
At d=0.08D, there is already a point at which it is impossible to measure the dripping rate due to the occurrence of collapsed cans (X in the figure).
(marked), the sag flow occurrence rate never reached zero.

Figure 8 summarizes the above Figures 6 and 7 in one figure, and as is clear from this figure, when the nozzle diameter d = 0.1D or less, which has been conventionally used,
This means that there is no negative pressure region where both the incidence of can collapse and the incidence of paint dripping can be reduced to zero.

The nozzle diameter d is preferably larger than the can diameter D, but as shown in FIG.
It is necessary to cover the conveyor belt 7 and the outer suction nozzle 9A, and if the outer suction nozzle 9A becomes too small, less hot air will flow into the can, and the heating effect from inside the can will decrease.

Therefore, the maximum diameter of the nozzle 9 is 0.5D. Further, for the above-mentioned reasons, it is desirable that the diameter of the outer suction nozzle 9A is also within the range of d=1/10D to 1/3D.

Since the present invention is configured as described above,
It has the following remarkable effects.

(b) By setting the aperture diameter of the central hot air suction nozzle and the outside suction nozzle to a range of 1/10 to 1/2 of the diameter of the opening end of the can, even if the amount of air passing through the can increases slightly, Since the suction flow of hot air passing through the outside suction nozzle is slowed down, it is possible to prevent paint from dripping near the lower end (opening end) of the outer surface of the can, and to prevent the droplets from being sucked and attached to the inner surface of the can. In addition, sufficient hot air is supplied into the can, improving thermal efficiency.

(b) By making the aperture diameter of the hot air suction nozzle larger than the aperture diameter of the outer suction nozzle, the hot air supplied from the outer nozzle into the can can be exhausted from the central hot air suction nozzle, which has a larger aperture diameter. , the exhaust efficiency is large, and the reduced pressure inside the can, that is, the holding force Ph=P ₂ - P ₃ of the can body becomes large, resulting in a large holding force of the can body.

(c) Since the outer suction nozzle is not covered by the can body, the hot air along the outer surface of the can is blown down to the opening end, preventing turbulence and preventing the can from being blown over.

(d) Furthermore, as a result of supplying sufficient hot air into the can, the can can be heated more uniformly.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the baking drying furnace of the present invention, Figure 2 is a schematic diagram of the baking drying oven of the present invention;
The figure is a perspective view showing the nozzle arrangement of the can body transfer section.
4 is a plan view showing a known nozzle arrangement, FIG. 4 is a plan view showing a nozzle arrangement according to the present invention, FIG. 5 is an explanatory diagram of the operation of a baking drying oven, and FIG. 6 is a diagram showing the incidence of collapsed cans and the nozzle diameter. Figure 7 is a graph showing the relationship between paint dripping rate and nozzle diameter.
The figure is a graph showing the relationship between nozzle diameter and available suction negative pressure. DESCRIPTION OF SYMBOLS 1... Burner, 3... Hot air supply chamber, 4... Can body passage chamber, 5... Hot air recovery chamber, 8... Hot air blowing nozzle, 9... Hot air suction nozzle, 12... Nozzle component, 13... ...Can body.

Claims (1)

[Scope of Claims] 1. Consisting of a hot air supply chamber, a can body passage chamber, and a hot air recovery chamber, a suction nozzle of the hot air recovery chamber sucks and recovers hot air from the can body to be baked and dried, and as a result, the hot air supply chamber In a baking drying furnace configured to allow hot air supplied from the can to flow into the can, an outer suction nozzle row that opens into the can body passage chamber is provided outside the suction nozzle, and the outer suction nozzle row opens into the can body opening. The opening diameter of the suction nozzle of the hot air recovery chamber is larger than the opening diameter of the outer suction nozzle, and is 1/10 of the diameter of the opening end of the can body.
A baking drying oven for can bodies and containers, characterized in that the drying temperature ranges from 1 to 1/2. 2 The opening diameter of the outer suction nozzle for hot air to flow into the can is 1/10 to 1/3 of the diameter of the opening end of the can.
A baking drying furnace for can bodies and containers according to claim 1, characterized in that the range is as follows.