JPS6148858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the moisture content of granular materials, particularly foundry sand.

In foundries, controlling the moisture content of foundry sand is extremely important. For this purpose, it is necessary to accurately measure the water content of the foundry sand before and after kneading, and to adjust the appropriate water addition during kneading accordingly.

Conventional methods of measuring moisture content include measuring the electrical resistance value from the moisture attached to the foundry sand, measuring the apparent density by weighing, and measuring the moldability of the foundry sand by providing multiple slits in the transport trough. There are various methods, such as a method that uses a sensor to detect whether the layer thickness of molding sand flowing out from each slit has reached a certain level. Among these, the first
As shown in the figure, it is well known that a method of measuring moisture by bringing an electrode into contact with foundry sand and detecting the electrical resistance value of the foundry sand has been put into practical use.

In FIG. 1, a pair of electrodes 4 and 5 supported by an electrode support 3 are inserted to a certain depth H into molding sand 2 which is conveyed by a conveyor 1 as indicated by an arrow A. Moisture is measured by detecting the resistance value. In this case, a scraper 6 is provided in front of the electrodes 4 and 5 to level the surface of the molding sand 2.

However, the conventional moisture measuring device described above had the following drawbacks.

1 A characteristic of foundry sand is that when it contains moisture, it separates into small lumps, forming voids between the lumps, and the contact state of the molding sand to the electrode becomes dense in some parts of the electrode, and It becomes sparse in some parts and becomes uneven. Furthermore, the higher the moisture content of molding sand, the worse the surface condition becomes. Even if you smooth it with a scraper, for example, if the moisture content reaches about 4.5%, the surface will be extremely rough and cannot be conveyed uniformly. It disappears.

2. It is difficult to always keep the amount of molding sand 2 conveyed on the conveyor 1 constant. For this reason, the layer thickness (surface level) of the foundry sand changes, and the contact state of the foundry sand to the electrode becomes uneven, making accurate moisture measurement impossible.

For the reasons mentioned above, conventional electrical resistance moisture measuring devices can accurately measure the actual moisture value of foundry sand up to about 3.5%, but if the actual moisture value exceeds 3.5%, the measurement will fail. The scale of the vessel varied widely regardless of the true fluctuations in moisture content, and had the drawback of not being able to maintain an orderly correlation.

Therefore, the moisture value of the foundry sand before kneading was measured using an electrical resistance type moisture measuring device, and based on this measurement value,
Moisture adjusting devices that adjust to a target moisture value have a drawback in that the accuracy of the adjustment decreases.

An object of the present invention is to provide an electrical resistance method for measuring and adjusting the moisture content of powder or granular material, which improves the above-mentioned conventional drawbacks.

In the present invention, when the moisture value of the granular material was kept constant, an experiment was conducted on the relationship between the layer thickness and the current value flowing between the electrodes, and it was found that when the layer thickness of the granular material exceeds a certain level, the current value becomes constant. This was done with this in mind.

The present invention will be explained below based on examples. Second
The figure shows an example of an electrical resistance type moisture measuring device for carrying out the present invention. In the figure, 7 is foundry sand conveyed in the direction of arrow A by a belt conveyor 8 or the like. An electrode support 9 is provided on the conveyor 8 so as to press the molding sand 7 from the surface thereof. The electrode support 9 is provided with a streamlined portion 9a facing the traveling direction A of the molding sand 7, and has a flat bottom surface 9b, and electrodes 10 and 11 are provided so as to be in contact with the molding sand 7. A support plate 12 is provided upright on the electrode support 9 . and,
The support plate 12 and the support plate 13 fixed to a frame (not shown) or the like are connected by link members 18, 19 via pins 14, 15, 16, 17. Therefore, the electrode support 9 presses the surface of the molding sand 7 by its own weight, and also moves freely in the vertical direction according to changes in the layer thickness (surface level) of the molding sand 7 conveyed on the conveyor 8. It is now possible to move to Reference numeral 20 denotes a dog provided on the support 12, and when the vertical level of this dog 20 reaches a preset reference level, the dog 20 comes into contact with a limit switch 22 installed on the support 21.

23 is a heater connected to a power source (not shown). The heater 23 is used to appropriately heat the bottom surface of the electrode support 9 where it contacts the molding sand 7, thereby preventing molding sand from adhering to the electrode support 9. 24 is a scraper for scraping the surface of the foundry sand 7 uniformly. In addition to the detection means using the dog 20 and limit switch 22, it is also possible to employ detection means using other sensors.

Next, the operation of the present invention will be explained based on FIG. FIG. 3 shows an example of a moisture adjustment system for powder and granular materials such as foundry sand using the present invention. In FIG. 3, 25 is a conveyor device for feeding the foundry sand before moisture adjustment into a kneading device 26, for example, a continuous sand mill, a multi-mixer, etc., and 27 is a conveyor device for adding water to the foundry sand in the kneading device 26. The water tank 28 is an automatically operated valve such as a solenoid valve installed in the piping 29. 30 is a belt conveyor for conveying the foundry sand whose moisture content has been adjusted to a target moisture value by the kneading device 26 to the next process (for example, a sand hopper of a mold making machine). 31a, 31
b is a moisture measuring device shown in FIG. 2, which measures the moisture value of the foundry sand flowing through the conveyors 25 and 30 before and after moisture adjustment, respectively. The moisture measuring device 31b may be provided as necessary. 31
Numerals a and 31b are thermometers, for example, thermocouple thermometers, which measure the temperature of the foundry sand before and after moisture adjustment. 33 is a device such as a microcomputer that performs calculation, storage, and control. The microcomputer 33 controls the automatic valve 2
8. Moisture measuring device 31a, 31b, thermometer 32
It is electrically connected to the terminals a and 32b so that signals can be input and output.

Next, the operation of the moisture adjustment system shown in FIG. 3 will be explained. First, the belt conveyor 25 is driven to continuously feed foundry sand (returned sand) before moisture adjustment into the kneading device 26 . At this time, the kneading device 26 is also driven. The kneading device 26 is configured to knead a predetermined amount of foundry sand and deliver a predetermined amount with controlled moisture to the conveyor 30. After a certain period of time has elapsed since a certain amount of foundry sand was put into the kneading device 26, the moisture value and temperature of the foundry sand flowing through the belt conveyor 25 before moisture adjustment are determined, and furthermore, the moisture value and temperature of the foundry sand discharged from the kneading device 26 are determined. The moisture value and temperature are measured by moisture measuring devices 31a, 31b and thermometers 32a, 32b and input into the microcomputer 33. The moisture value and temperature are measured at preset time intervals (for example, at 0.1 second intervals). microcomputer 3
3, moisture measuring devices 31a, 31b, thermometer 32
Input signals from a and 32b as numerical values (moisture %, °C)
Convert to

Next, the microcomputer 33 uses a predetermined calculation formula to determine the amount of insufficient moisture to adjust to the target moisture value from the above-mentioned measured values, the amount of sand processed by the kneading device 26, and the like. The microcomputer 33 then controls the automatic valve 28 to add the insufficient amount of moisture to the kneading device 26, thereby uniformly adjusting the moisture value of the foundry sand to the target value.

However, as mentioned above, the belt conveyor 2
The layer thickness (surface level) of the foundry sand flowing through the molding sands 5 and 30 is not uniform, and when the layer thickness falls below a certain level, the measurement accuracy of the electrical resistance moisture measuring device 31a decreases. In the present invention, as shown in FIG. 2, a limit switch 22 is activated when the thickness of the foundry sand layer falls below a certain level. When the limit switch 22 is activated, the current value flowing through the electrodes 10, 11 is not used as an input to the microcomputer 33, and instead, the previously measured value (when the limit switch is activated) is used as an input to the microcomputer 33. Determine the amount of water shortage using the current value measured when the water is not in use.

In addition, as a method for determining the water shortage amount using the microcomputer 33, the average value of a plurality of moisture values and temperature measurements set in advance in time series is determined, and the water shortage amount is determined from these average values. Adding this insufficient amount of moisture to the kneading device further improves the accuracy of adjusting the moisture value.

The present invention described above has the following effects when used in a moisture regulating device for foundry sand and the like.

In other words, when the surface level of the foundry sand falls below a certain level, the moisture measurement value at that time is not input into the microcomputer, but the previously measured value is input, which improves the accuracy of adjustment to the target moisture value of the foundry sand. Improve more. In particular, the effect is great if the time intervals for measuring moisture values and temperatures are shortened. The reason for this is that the moisture value of the foundry sand flowing through the belt conveyors 25, 30 is unlikely to change significantly in a short period of time.

Further, in the present invention, when the surface level of the molding sand decreases and the limit switch 22 is activated, it is preferable to activate an alarm device (alarm bell, lamp, etc.).

In the above description of the embodiments of the present invention, the method for controlling the moisture content of foundry sand has been described, but the present invention
Of course, the present invention can also be applied to a general moisture measuring device for powder or granular materials.

[Brief explanation of the drawing]

Figure 1 is a side view showing an example of a conventional device; Figure 2 is a side view showing an example of a conventional device;
The figure is a side view showing an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a moisture adjustment system for powder or granular material using the apparatus of the present invention. 7: Foundry sand, 8: Belt conveyor, 9: Electrode support, 10, 11: Electrode, 20: Dog, 22:
Limit switch.

Claims (1)

[Claims] 1 Press an electrode against the powder or granule material conveyed by a belt conveyor, etc., input the current value to a control device at specified time intervals to obtain the moisture value of the powder or granule material, and the control device determines the moisture content of the powder or granule material. An electrode support in which an electrode is embedded and is movable up and down as if pressing the powder, in a method for adjusting the moisture content of a powder or granule, in which the moisture content is calculated and the insufficient moisture is added to a powder or granule kneading device. is provided with a detection means for detecting the lower limit level in the vertical direction, and when the detection means is in operation, the control device detects the insufficient water amount using the latest current value when the detection means is not in operation. A method for adjusting the moisture content of a powder or granular material, characterized by calculating the moisture content of a powder or granular material.