JPH086535Y2 - Pre-purge controller for hot air drying oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a pre-purge control device for a hot air drying oven,
More specifically, it relates to improvement of safety of the device.

(Prior Art) Generally, a hot air drying oven is used for drying painted automobile parts and the like. This equipment successively conveys the coated parts into a drying oven to which hot air is continuously fed and dries the coating film. The drying oven is usually divided into several zones. Hot air is formed by sending hot air generated by gas combustion in a burner directly or by sending warm air that has undergone heat exchange with the air by the operation of a blower, fan, etc. Circulate between each zone of the drying oven.

Thus, in the operation of this hot-air drying oven, in order to prevent the occurrence of an explosion accident of fuel gas, prior to the pre-purge before combustion, that is, gas combustion, there is no residue remaining inside the drying oven and the circulation duct. It is legally obligatory to perform the operation of discharging the combustion gas to the outside with a fan.

The pre-purge operation is generally carried out in a stage prior to gas combustion in which the outside air volume is usually 10 to 20 times the total volume of the drying furnace (the volume of each zone when divided into several zones). It is assumed that the original furnace air has been completely replaced.

On the other hand, the amount of hot air supplied per unit time in the hot air drying furnace is naturally determined by the air supply capacity of the blower, fan, etc.

Therefore, conventionally, as a conventional and convenient method, the time required for pre-purging (hereinafter referred to as pre-purge, which is calculated from the amount of outside air introduced depending on the volume of the drying furnace and the air feeding capacity of the drying furnace) Time) is set by a timer, the air feeding operation of the drying furnace is continued for the set time, and the gas combustion operation is started after the set time has passed.

The pre-purge time has a considerable range up to the time that is considered to be safer than the time that should be absolutely secured under legal regulations, and in actual operation, the pre-purge time considered to be appropriate was selected from the range.

(Problem to be solved by the invention) However, a timer generally used in the conventional pre-purge control can set an arbitrary time within a time range from 0 minute to a fixed time (for example, 30 minutes). Met.

Therefore, if the timer is set to a time shorter than the originally set time due to operator error or the like, the pre-purge will not meet the criteria set as appropriate, and especially if the set time is too short, safety There was a risk that it would cause a serious problem.

The present invention has been made to improve this point, and the purpose thereof is to make sure that the pre-purge necessary for safety can be surely achieved even if the timer time setting operation is mistaken, and the safety is further improved. It is to provide a pre-purge control device for a hot air drying furnace.

(Means for Solving the Problem) The present invention achieves such an object, and a fixed timer unit in which a fixed time required for pre-purge is set invariably in a pre-purge control circuit is provided. A hot-air drying furnace comprising a variable timer unit capable of setting an arbitrary time and incorporating a pre-purge timer in which the timer operation of the other timer unit is started after the set time of one of the timer units has elapsed. Of the pre-purge control device.

"Predetermined time required for prepurge" means one time determined from the range from the minimum time required to comply with the regulations concerning prepurge to the time considered to be appropriate from a safety point of view. Say. In a practically used ordinary drying oven, it is determined within a range of, for example, 3 minutes to 10 minutes.

The pre-purge timer according to the present invention comprises a fixed timer unit and a variable timer unit, and the fixed timer unit is set to have a constant time required for the above-mentioned pre-purge, while the variable timer unit has an arbitrary value within a certain range. You can set different times. In this timer, either the fixed timer unit or the variable timer unit first operates, and then the other timer unit starts operating when the set time of the timer unit has elapsed. Therefore, the sum of the set time of the fixed timer unit and the set time of the variable timer unit becomes the prepurge time.

(Operation) In the present invention, since the pre-purge timer is incorporated in the control circuit, even if the variable timer unit sets the time 0 minutes, the fixed timer unit always operates, so that the pre-purge operation causes the fixed timer unit to operate. The air supply operation of the drying furnace is continued for a preset invariant time, that is, for a fixed time required for the pre-purge. Therefore,
In any situation, the pre-purge time that is longer than the minimum required time for legal regulation or safety can be ensured, and there is no concern about safety.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

The embodiment is applied to a prepurge control device for a conventional hot air drying furnace, and FIG. 1 shows a prepurge timer used for the control device. This timer 1 is switch 2
The operation of the built-in fixed timer section is started at the same time as POWER ON by, and the operation is finished after a predetermined time T _c , and at the same time, the operation of the variable timer section 3 is started,
After that, the operation is continued for a time T _i adjusted before POWER ON.

The time T _c is a fixed time required for the pre-purge, and is set to 3 minutes invariably in this embodiment, while the time T _i
Is a more arbitrarily set time within the range of 0 to 10 minutes.

The operation of the prepurge timer 1 is more clearly understood by the time chart shown in FIG. The sum of the invariable time T _c in the fixed timer section and the arbitrary time T _i in the variable timer section is the prepurge time. After completion of the prepurge time, the operation of the burner ignition operation circuit is started.

FIG. 3 shows the structure of the fuel gas supply pipe in the hot air drying furnace, and FIG. 4 schematically shows the general structure of the hot air drying furnace. As shown in FIG. 3, the fuel gas is supplied from the supply source to each zone of the hot air drying furnace. A zone shutoff valve, a main burner shutoff valve, etc. are provided in the middle of the supply pipe to each zone. Also, as shown in FIG.
In the hot air drying oven to which the present invention is applied, first, hot air generated by gas combustion in the burner 5 is circulated in the direction of arrow a by the operation of the fan 6 to supply hot air into the zone 4 of the drying oven. The air supply damper, the exhaust damper, the switching damper, etc. are provided at appropriate places in the supply duct.

The control device of the embodiment includes a burner, a blower, a fan, a shutoff valve and a damper shown in FIGS. 3 and 4,
The operation of various elements is automatically controlled, and the timer 1 is incorporated in a prepurge control circuit having a conventionally used configuration.

Next, the operation of the apparatus of the embodiment will be described with reference to FIGS.

FIG. 5 shows the operating procedure of the hot-air drying furnace from the start of operation to the pre-purging stage, and FIG. 6 shows the operating procedure of the furnace after pre-purging.

As shown in FIG. 5, from the start of operation, the operation of the circulation fan, the operation of the burner blower, the non-operation of the burner, the opening of the exhaust damper, the closing of the air supply damper, etc. are confirmed, and then the pre-purge stage is entered.

Then, as shown in FIG. 6, the pre-purge timer 1
Is started. Then, the pre-purge time (T _c
+ T _i ), that is, after the pre-purge is completed by the time up, the pilot valve is opened, the flame is detected, and then the main burner is ignited.

In the apparatus of the embodiment, even if the time setting of the variable timer unit 3 was wrong, the pre-purge time was always secured for at least 3 minutes by the operation of the built-in fixed timer unit, and the pre-purge required for safety could be achieved at least.

(Effects of the Invention) As described above, the pre-purge control device for the hot-air drying furnace according to the present invention operates the air supply operation of the drying furnace for at least the fixed time required for the pre-purge operation by the operation of the fixed timer unit. Since it is configured to continue,
Even if the timer setting operation is incorrect, it is possible to always secure a pre-purge time that is longer than the minimum required due to legal regulations, etc., so that the prepurge necessary for safety can be reliably achieved. It is possible to obtain the effect that the safety is further improved.

[Brief description of drawings]

FIG. 1 is a front view showing a pre-purge timer used in the apparatus of the embodiment of the present invention, FIG. 2 is a time chart showing the operation of the timer of FIG. 1, and FIG. 3 is a fuel gas supply pipe in a hot air drying furnace. FIG. 4 is a schematic diagram showing a schematic configuration of a hot air drying furnace, and FIGS. 5 and 6 are flowcharts showing an operating procedure of the hot air drying furnace. In the figure, 1 ... Pre-purge timer 2 ... Fixed timer switch 3 ... Variable timer section 4 ... Drying furnace zone 5 ... Burner 6 ... Fan

Claims (1)

[Scope of utility model registration request] 1. A pre-purge control circuit comprises a fixed timer section in which a fixed time required for the pre-purge is set invariably and a variable timer section capable of setting an arbitrary time within a certain range. A pre-purge control device for a hot-air drying furnace, comprising a pre-purge timer in which the other timer unit starts a timer operation when a preset time of the timer unit has elapsed.