JPH08304261A - Method for inspecting air ventilating state of device for measuring air permeability of molding sand - Google Patents

Abstract

PURPOSE: To decide whether or not the calculated air permeability of a test tube is accurate by blowing compressed air into the test tube at the same pressure or flow rate as that used when the air permeability of the sample is measured and circulating the air through an orifice for inspection. CONSTITUTION: An orifice 19 for inspection is inserted into a test tube 1 and the pressure of compressed air introduced to a conduit tube 5 from an air supplying source 6 is controlled to a constant value by means of pressure control means 9 and 12-14. The compressed air is blown into a probe head 2 and circulated to the orifice 19 through an air diffuser 4. An arithmetic means 15 calculates the air permeability of the test tube 1 from the flow rate and pressure of the compressed air respectively detected by means of a flow sensor 11 and pressure sensor 8. When the calculated permeability does not fall within an allowable range, air leakage occurs from the connecting section of the tube 5 or due to the blinding of diffuser 4 or deterioration of an O-ring 3. Therefore, the air ventilating state of the tube 1 is adjusted to a normal state by remedying the detective part. For this inspection, two or more orifices 19 having different diameters are used so as to improve the reliability of inspected results.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to put mold sand into a small container, press it, and blow compressed air having a constant pressure or flow rate into the small container to make the mold sand flow through. The present invention relates to a method for verifying a ventilation state in a device that measures air permeability.

[0002]

2. Description of the Related Art As a conventional device for measuring air permeability, a method of adjusting the flow rate of compressed air to be blown in a constant manner (Japanese Patent Publication No. 15825/1990 and Japanese Patent Publication No. 3-76).
No. 710), and a method of adjusting the pressure of the blown compressed air to a constant value (Japanese Utility Model Laid-Open No. 4-104568). In order to calculate the air permeability of the mold sand with these devices, it was performed based on the indicated values of the pressure gauge and the flow meter for measuring the state of the compressed air immediately before being blown (secondary side). By the way, in these devices, the values shown on the pressure gauge and the flowmeter are actually blown in due to the deviation of the pressure control valve or the flow control valve, the air leakage from the piping and the seal, and the displacement of the pressure converter. There are cases where the pressure and flow rate of compressed air may differ, but the method of calibrating this is not known, and it was not known whether the measured air permeability was accurate. The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for verifying a ventilation state in an apparatus for measuring air permeability.

[0003]

In order to achieve the above object, the method for verifying the ventilation state of the apparatus for measuring the permeability of foundry sand according to the present invention is as follows. A method of verifying the ventilation state of a device that allows the mold sand to flow through by blowing compressed air at a constant pressure or flow rate into the test cylinder, and the step of inserting the verification orifice into the test cylinder and And a step of injecting compressed air of the same pressure or flow rate as in the above-mentioned air permeability measurement to allow the air to pass through the verification orifice, and the air permeability of the verification orifice at this time is calculated, and the value is calculated as a normal value of the verification orifice. And a step of comparing with the air permeability of.

[0004]

The present invention will be described in detail below based on an embodiment. In FIG. 1, a blower head 2 for blowing compressed air into the test cylinder 1 is detachably inserted into the lower end of the cylindrical test cylinder 1, and the contact portion between the two is made airtight by an O-ring 3. Has been done. An air diffuser plate 4 is attached to an upper end portion of the blow head 2 having an air blowing port. The inner space of the blow head 2 communicates with the compressed air source 6 via the conduit 5 and also communicates with the first pressure sensor 8 via the conduit 7. An electropneumatic proportional valve 9, a chamber 10, and a flow sensor 1 are provided in the conduit 5 from the upstream side.
1 is provided in this order. The chamber 10 is for stably measuring the pressure of the compressed air flowing through the pipe line, and a branch pipe 12 is connected to the chamber 10 for communication. The second pressure sensor 1 is attached to the branch pipe 12.
The third pressure sensor 13 is electrically connected to the electro-pneumatic proportional valve 9 via the air-electric converter 14. The second pressure sensor 13 detects the pressure of the compressed air flowing through the conduit 5, and the opening of the electropneumatic proportional valve 9 is adjusted based on the detected pressure so that the pressure of the compressed air flowing downstream is kept constant. There is. Further, the first pressure sensor 8 and the flow rate sensor 11 are electrically connected to a calculation means 15, which calculates both sensors 8.
The air permeability is calculated by the air permeability calculation formula stored in advance based on the value measured by. The calculated air permeability is displayed by the output means 16 electrically connected to the calculation means 15.

The following procedure is used to actually check the ventilation state with this device. That is, first, from the upper end side of the test cylinder 1, a stainless steel orifice 17 as shown in FIG. 2 is inserted into a stepped portion of a stepped through hole of a rubber 18, and a verification orifice 19 is inserted. To do. Subsequently, the compressed air introduced from the air supply source 6 into the conduit 5 is adjusted to a constant pressure by the pressure control means 9, 12, 13, 14 and blown into the blower head 2 through the air diffuser plate 4. Flow through the verification orifice 19. At this time, the air permeability is calculated from the values of the flow rate and the pressure detected by the flow rate sensor 11 and the second pressure sensor 8 according to the air permeability formula previously stored in the calculating means 15. If the value deviates from the upper and lower limit values shown in FIG. 3, the trouble is found by checking the air leakage due to the connection of the conduit 5, clogging of the diffuser plate 4 or deterioration of the O-ring 3. Improve and adjust for proper ventilation. The test is performed using at least two kinds of test orifices 19 having different diameters so that the test result is reliable. Insufficiency due to verification is pressure control means 9, 1
2, 13, 14 themselves, or the flow rate sensor 11 or the first pressure sensor 8, it is necessary to repair or replace them with normal ones, but even during that time, the air permeability stored in the calculation means 15 It is also possible to cope with temporarily calculating the correct air permeability by correcting the calculation formula of. In this embodiment, the verification method for the method in which the pressure of the compressed air to be blown is made constant is shown, but the same procedure can be performed when blowing the compressed air at a constant flow rate.

As is apparent from the above description, the present invention provides a ventilation state when measuring the air permeability of the mold sand compacted by inserting the test orifice into the test tube and venting the compressed air. Since it is possible to determine whether or not the calculated air permeability is accurate, it is possible to ensure the reliability of the air permeability measuring device.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a test orifice according to the present invention.

FIG. 3 is a graph showing a relationship between a test orifice diameter and air permeability in the present invention.

[Explanation of symbols]

 1 Test tube 19 Orifice for verification

Claims (1)

[Claims] 1. Ventilation of a device for charging mold sand into a test cylinder 1 and compressing the mold sand, and blowing compressed air of a constant pressure or flow rate into the test cylinder 1 to flow through the mold sand to calculate the air permeability thereof. A method for verifying the condition, which is a verification orifice 1
9 is inserted into the test cylinder 1, compressed air having the same pressure or flow rate as in the air permeability measurement is blown into the test cylinder 1 to allow the verification orifice 19 to flow through, and the verification at this time. Of the air permeation rate of the casting orifice 19 and comparing the value with the regular air permeance of the verification orifice 19.