JPS6182934A - Method and press for forming bent membrane used for low temperature tank - Google Patents

Abstract

PURPOSE:To bend a sheet while forming its corrugated part into a good shape by mounting the sheet having a corrugation on a supporting bed for bending it, pressing by means of a flat-sheet press punch having an air cylinder, and forming the corrugated part by pressing successively by means of a press punch. CONSTITUTION:A membrane sheet 1 having a corrugation 2, used for a low temperature tank, is mounted on a supporting bed 7 having a prescribed bending angle. The sheet 1 is bent by lowering a press head 6 to force a flat-sheet press punch 3 having an air cylinder 4 to press the sheet 1 and the corrugated part 2 is simultaneously formed by pressing it by means of a corrugated-part press punch 5. Thus, the sheet 1 is bent and its corrugated part is simultaneously well formed, by this restriction forming.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding a membrane sheet for use in a low-temperature tank, and to improvements in a press for molding the same.

[Conventional technology]

Tanks for low-temperature fluids (about -160°C) such as LNG,
A membrane sheet type tank with corrugation is installed inside the outer concrete tank with a cold insulation material in between, and the tank is heated at temperatures ranging from room temperature to 1160°C, which is the boiling point of LNG.
Near 0°C (The corrugation absorbs the expansion and contraction of the tank material due to temperature changes.

By the way, the membrane tank has corners with various angles, and the side wall surface is usually shaped into a polygonal column shape of 72 or 200 sides rather than a cylinder. It is molded. Figures 4 and 5
The figure is a perspective view showing the intended bending state and the state of buckling wrinkles that occur at the fulgation part (() when attempting to simply bend it. In the figure, 1 is a membrane sheet;
2 is the corrugation part, 11 is the bent part, 12
are buckling wrinkles. During molding, the folded part 11 in Fig. 4
When pressed with a press punch, etc., the membrane sheet is molded as shown in FIG. 4, but buckling wrinkles 12 as shown in FIG. 5 occur at the corrugations.

[Problems to be solved by invention]

The above-mentioned buckling itself is caused by bending the plate, and there is no expansion or contraction of the plate, so it is good that there is little material deterioration, but the shape of the buckling changes each time it is formed and is not stable, so the membrane performance is affected. The problem is that it is not stable. This buckling occurs when a simple bending method is used, so it may be possible to deep draw the material using male and female press dies while applying tension to the material, but this method would cause the plate to expand and contract. As a result, the corrugation becomes martensitic and becomes susceptible to fatigue, so it cannot be used in low-temperature tanks that repeatedly expand and contract due to temperature changes. It also has the problem of generating large strains due to thermal deformation at low temperatures.

In other words, it is generally desirable for membranes used in low-temperature tanks to expand and contract smoothly without generating excessive strain in response to temperature changes of up to 200°C, in order to prevent fatigue failure. ℃・. Therefore, when molding a membrane sheet, avoid press molding that causes thinning and distortion in the deformed part, and avoid the deformation of the corrugated part obtained by molding by creating a so-called developable surface (that can be pulled from two directions) like origami crafts. A method that mainly involves bending and forming will be used, which will return the plate to its original flat shape.

The purpose of the present invention is to angle the membrane sheet so that the deformation that occurs in the corrugations during the molding of the membrane sheet is not accompanied by expansion and contraction of the plate, and that the deformation is stable and takes the same shape every time it is molded. This paper aims to provide a molding method and a press for the molding.

[Means for solving problems]

In order to achieve the above object, when molding the membrane, a flat plate pressing punch and a corrugation pressing punch were installed in the molding press, first, the side of the corrugation was pressed with the flat plate pressing punch, and the full length was pressed into a flat plate by molding. Bend the membrane while preventing it from forming.Then, the corrugation pushing punch is activated and the tip of the corrugation pushing punch presses the peak of the corrugation part to form a recess of a certain shape. It is something to do.

[Made on April 4] The flat plate press punch is attached to the press head via an air cylinder (also an oil cylinder) or a spring. During molding, when the press head is pushed down, the flat plate punch first presses the flat part of the membrane, including the sides of the corrugations, onto the table. At that time, in consideration of springback, there was a V molded on the table at a slightly larger angle than the angle at which the membrane should be bent.
A letter-shaped support is set at t', and the membrane sheet is pressed onto this support using a press spatula. When the press head operates and presses down the flat plate push punch, the air cylinder or spring of the punch is compressed, so the corrugation push punch is activated, the tip of the push punch contacts the peak of the corrugation, and then Press the part to create a depression-like deformation. Since the corrugation is pressed with the same force using a corrugation push-punch of the same shape, the depressions created at the peaks of the corrugations are always the same and stable.

[Embodiments of the invention]

1 and 2 are a side view and a front view of the main parts of a molding machine showing an embodiment of the present invention. In the figure, 1 is a membrane having corrugations 2, 3 is a flat plate push punch, 4 is an air cylinder, 5 is a corrugation push punch, 6 is a press head, 7 is a support stand, and 8 is a press table.

In the figure, a support stand 7 placed on a press table 8
When the press head 6 operates and the membrane 1 placed on top moves downward, the flat plate portion is first pressed downward by the V temporary press punch 6.

As shown in the figure, the punch hits up to the side 2a of the corrugation, thereby preventing the corrugation from opening due to pressure. As shown in FIG. 1, the membrane is supported at both ends of the support base 7, and is pressed by the punch at the center, so it bends and eventually follows the slope of the support base to rli as shown by the dashed line. , Type Sanero. Since the lower plate push punch 3 is attached to the press head 6 via an air cylinder, the air cylinder 4 is compressed by the downward movement of the press head 6.
Eventually, the tip 5a of the corrugation push-in punch 5 comes into contact with the peak portion of the corrugation 2, and further presses this portion to cause a depression-like deformation.

If the displacement of the press head O is made constant each time molding is performed, the force with which the tip of the corrugation pushing punch 5 presses the corrugation 2 of the membrane 1 is constant, and therefore the deformation that occurs in this part will be in the same form.

In the above embodiments, the air cylinder 4 was used as a shock absorber for the flat plate push punch, but the same results could be obtained with an oil cylinder or a spring.

In addition, the support stand 7 used has a square square shape as shown in FIG. 1, but as shown in FIG.
etc. may also be used.

〔Effect of the invention〕

To shape the membrane to be used in the low-temperature tank, we used a press with a flat plate push punch and a corrugation push punch.First, we bent the flat part of the membrane with the flat push punch, then corrugated it with the corrugation push punch By applying pressure to the corrugated part of the membrane molding, it became possible to create a fixed shape deformation that does not involve expansion or contraction of the plate.

[Brief explanation of drawings]

1 and 2 are a side view and a front view of the main parts of a press for molding a membrane sheet showing one embodiment of the present invention, and FIG. 6 is an explanatory diagram showing another embodiment of supporting the membrane sheet,
Figure 4 is an explanatory diagram showing conventional molding of membrane sheets;
FIG. 5 is a perspective view of buckling wrinkles in the corrugated portion that occur at this time. 1 in lfl is membrane sheet, 2 is corrugation,
6 is a flat plate pushing punch, 4 is an air cylinder, 5 is a corrugation pushing punch, 6 is a press head, 7 is a support stand, 8 is a table, 9 is a fulcrum, and 10 is a spring.

Claims (2)

[Claims] (1) When molding a membrane sheet for a low-temperature tank, the molding press is equipped with a flat plate pushing punch and a corrugation pressing punch, and the flat plate part of the membrane sheet is pressed first, and then the corrugation part is pressed. Membrane angulation molding method for low-temperature tanks. (2) A press for forming a membrane for a low-temperature tank, which is equipped with a flat plate pushing punch and a corrugation pushing punch, and presses the flat plate part of the membrane sheet first, and then presses the corrugation part. A flat press punch for a low-temperature tank, characterized in that the tip of the punch is formed to match the shape of the lower end of the corrugation of the membrane, and the punch is attached to a press head via a buffer such as an air cylinder. Press for membrane molding.