JPH01307567A - Fluororesin bellows and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily obtain belows excellent in durability and strength by interposingly pressing a cylindrical fluororesin sheet by means of a projecting roll and a recessed roll from the inside and the outside for each certain interval, and forming the ridge line portion of a projecting portion to be thinner than other portions. CONSTITUTION:A recessed roll 14 on the outside and a projecting roll 13 on the inside are rotatingly brought close to a cylindrical fluororesin sheet S1, which is interposedly pressed by a projecting portion 13a and a recessed portion 14a to be partially rolled out. At this time, the inside of the sheet S1 is subjected to a flow phenomenon in which the surplus thickness thereof is shifted in the axial direction due to the pressing action of the projecting portion 13a while the outside being curled by the recessed portion 14a, and the sheet S1 is curved in a semicircular form due to the permanent deformation and curling, simply forming a thin-walled ridge portion. By repeating this for each defined interval, a plurality of ridge portions and valley portions are formed, thereby forming bellows expanding/contracting in the axial direction. Hence, bellows can be easily formed only by the use of rolls 13, 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluororesin bellows used in valves, pumps, or other fluid control devices, and a method for manufacturing the same.

Metal bellows have been known for a long time, but these metal bellows require precise welding equipment during production and are more expensive than synthetic resin bellows. For this reason, synthetic resin B bellows are used in general-purpose fluid control devices.

Among these synthetic resin bellows, fluororesin bellows, such as polytetrafluoroethylene (PTF)
Resin bellows (referred to as E) have not only excellent thermal properties and surface properties, but also mechanical, electrical, and chemical properties, so they have recently been widely used in various fields. It has become.

However, since the conventional PTFE resin bellows is molded by the following manufacturing method, it has the following disadvantages.

First, as a first manufacturing method of the PTFE resin bellows, there is a method of molding by machining.

In this method, a pipe or cylindrical body made of PTFBVA resin is cut using a lathe, and the cross-sectional shape is finished as shown in FIG. 6.7.

However, in the PTFE resin bellows 1.2 molded by this method, when it is desired to make the outer diameter of the joint flange portion 3 larger than that of the bellows body 4, an outer diameter corresponding to the outer diameter of the joint flange portion 6 is required. Since cutting is performed from a round bar or cylindrical sleeve 5 having a diameter dimension, a large part is created to be cut, resulting in wasted material, and there is a risk that the cutting process takes a long time and increases manufacturing costs.

Further, there is a possibility that such a bellows 1-12 made of PTFE resin may have insufficient strength. Furthermore, in order to form large-diameter bellows, not only a large-diameter sleeve is required, but also expensive large-scale mechanical equipment must be prepared separately, which is a significant cost disadvantage. It has become.

Therefore, in practice, it has been considered impossible to mold bellows having an outer diameter of 1000 mm or more.

A second manufacturing method for the PTFEgd bellows is a method in which a PTFEhd pipe is plastically deformed by rolling using a mold jig and processed into a bellows shape;
There is a method of applying pressure fluid (usually liquid pressure) inside a pipe made of FEI resin to cause it to undergo rolling plastic deformation toward the outer diameter side, thereby processing it into a bellows shape.

However, even with this method, large mold jigs, etc. are required to mold large-diameter bellows, which makes handling difficult, and in practice, it is impossible to mold bellows with an outer diameter of 1000 m+ or more. there were.

The present invention has been made to solve the drawbacks and problems associated with the above-mentioned prior art.When a fluororesin sheet is rolled, the fluororesin itself undergoes phenomena such as permanent deformation and flow, and The first object of the present invention is to provide a PTFE resin bellows that is simple, inexpensive, and excellent in durability and strength by focusing on the curling property and utilizing these phenomena.

A second object of the present invention is to provide a manufacturing method that allows not only small-diameter PTFE resin bellows but also large-diameter bellows to be obtained easily and inexpensively.

In order to achieve the first object, the present invention provides a fluororesin bellows having an accordion-shaped bellows body in which peaks and valleys are alternately formed and expands and contracts in the axial direction. It is characterized by a fluororesin bellows constructed so that the ridgeline part of the mountain part is thinner than the other parts.

The fluororesin bellows with this structure has a thinner wall at the ridgeline than the other parts, so the hinge action of this thin section provides excellent elasticity. , it can be formed without cutting by taking advantage of its flow phenomenon, property of permanent deformation, or property of curling, so it has excellent mechanical strength,
Moreover, the bellows are made of durable fluororesin.

Furthermore, if a corrosion-resistant ring is interposed inside the crest of the fluororesin bellows, the crest can be reliably formed and held.

In order to achieve the second object, the present invention provides a method for manufacturing a fluororesin bellows having an accordion-shaped bellows body in which peaks and valleys are alternately formed and expands and contracts in the axial direction. By pinching the fluororesin sheet from the inside and outside with convex rolls and concave rolls, the fluororesin sheet is rolled at predetermined intervals, so that the ridgeline portions of the mountain portions are more flat than other portions. It is also characterized by having a thin wall.

According to this method, a bellows-shaped part can be formed by compressing the fluororesin sheet with rolls and rolling it partially, so it is possible to form a bellows-shaped part from small to large dimensions. It can be made cheaply and easily.

In particular, if a flat fluororesin sheet is molded and then both ends of the fluororesin sheet are joined, even extremely large products can be easily manufactured.

Dear friend! ” U11 Anti-Homo Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a cross-sectional view of a main part showing an embodiment of the present invention, and Fig. 2 (
A) and (B) are cross-sectional views showing the main parts of the method of the present invention, Fig. 3 is a cross-sectional view showing the usage state of the same embodiment, and Fig. 4.5 is a main part showing other examples of the present invention, respectively. FIG.

As shown in FIG. 1, the fluororesin bellows 10 includes a bellows body 11 in the shape of a bellows that expands and contracts in the axial direction and has peaks Y and valleys T formed alternately, and a bellows body 11 that protrudes from both ends of the bellows body 11. The cylindrical portion 12 is made entirely of fluororesin, for example, PTFE resin.

In particular, this fluororesin rosette 10 is made such that the ridgeline portion Ya of the crest Y (which marks the crest and its vicinity) has a wall thickness ta that is thinner than the wall thickness t of the other bellows body 11. There is. .

This peak Y is a part that is subjected to a so-called bending action during use, but if such a peak Y is made to have a thin wall thickness ta, this part will serve as a hinge, so to speak, and the wall thickness ta will be thin. Therefore, it has excellent elasticity.

To mold such a fluororesin bellows 10,
This is done by the following method.

First, as shown in FIG. 2(A), a convex roll 13 and a concave roll 14 whose respective axes are arranged parallel to each other are formed from the inside and outside of the cylindrical fluororesin sheet S1. Pressure is applied. In this case, the pinching is started from a position that takes into account the length O of the cylindrical portion 12. Note that the cylindrical fluororesin sheet S1 is made by joining (welding) both ends of a flat fluororesin sheet to form a cylindrical shape. It may be molded by forming it.

The pinching is performed by rotating the convex roll 13 and the concave roll 14 and bringing them close to each other. Since the convex portion 13a and the concave portion 14a cooperate with each other,
The fluororesin sheet S is partially rolled by both of them.

In this case, the inner side of the fluororesin sheet S is the convex portion 13a.
Under the pressure action of This means that the curved peak Y can be simply formed. Incidentally, such pinching pressure can be applied to a half-split convex roll 13- as shown in FIG. 2(B).
It can also be carried out using a concave roll 14-.

After performing one rolling in this way, next, this cylindrical fluororesin sheet S is slightly shifted in the axial direction, and the next rolling is performed at a predetermined distance from the formed peak Y.
When a plurality of locations are rolled in this manner, peaks Y are inevitably formed, and valleys T can be formed between the peaks Y without processing the valleys T.

Then, by performing rolling one after another to form peaks and valleys alternately, it is possible to form the bellows body 11 in the form of a bellows that expands and contracts in the axial direction.

In this way, in this embodiment, the bellows can be formed only by using two rolls 13 and 14 without using large mechanical equipment, so it is not only advantageous in terms of cost, but also easy to use. This also makes the manufacturing process more efficient.

When using the fluororesin bellows 10 molded in this way, the bellows brush 10 as shown in FIG.
It is well known that flange parts 15 are formed on the cylindrical part 12 at both ends of the cylindrical part 1, and the flange part 15 is attached to the flange 17 on the side of the pipe 16 through which the fluid flows, covered by an outer cylinder 18, and a control ring 19 is attached. The control ring 19 is often attached to the outer periphery of the bellows body 11 in this manner when the fluid flowing inside is particularly a vacuum fluid.

In the embodiment described above, there is no intervening material inside the bellows main body 11, but the present invention is not limited to such an embodiment.As shown in FIG.
If a corrosion-resistant ring 20, for example, a metal ring coated with fluororesin, is inserted inside, the shape of the semicircular peak Y can be reliably formed and maintained.

Further, as shown in FIG. 5, the entire outer circumferential surface of the fluororesin bellows 10 may be covered with a metal layer 21 to form a double-structured bellows. If this is done, the elasticity and strength will be improved. You can get something excellent.

Furthermore, the method for molding the fluororesin bellows 10 may also be carried out by the following method.

In the method described above, a cylindrical fluororesin sheet S was used, but the sheet S may be a flat fluororesin sheet (not shown) instead of a cylinder. As in the previous embodiment, by pinching the sheet from both sides with the convex rolls 13 and the concave rolls 14 and partially rolling the fluororesin sheet at predetermined intervals, the ends can be released. A bellows body having a C-shaped cross section can be formed. Therefore, after the above-mentioned rolling process is completed, by joining both ends of the fluororesin sheet by a method such as heat fusion, a bellows-like body with alternating peaks and valleys that expands and contracts in the axial direction is formed. can do.

It goes without saying that when molded in this way, a fluororesin bellows with excellent strength and durability similar to that of the above-mentioned example can be obtained, but in this case, the outer diameter is even larger. It becomes possible to mold a bead with

In addition, in the above-mentioned embodiment, PTFE is used as the fluororesin.
However, the present invention is not limited to this, and PFA, which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, FEP, which is a copolymer of tetrafluoroethylene and hexafluoropropylene, or tetrafluoro Fluororesins such as EPE, which is a copolymer of ethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether, can be widely used.

Lord 1! 1. As described above, according to the present invention, the ridgeline part of the peak part of the fluororesin bellows is made thinner by rolling than the other bellows bodies, so it has excellent strength, It is durable, and if a corrosion-resistant ring is inserted inside the peak of this fluororesin bellows, the peak can be reliably formed and maintained.

The present invention also provides a bellows body by compressing a cylindrical fluororesin sheet from the inside and outside with a convex roll and a concave roll, and rolling the fluororesin sheet at predetermined intervals. Because it is molded, it is possible to make products of any size from small to large at a low cost and easily.Furthermore, if it is molded using a flat fluororesin sheet, it does not require the use of large machines. This makes it possible to easily make extremely large items.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below using more specific examples, but the present invention is not limited to these examples.

As a PTFE sheet, formed by cutting from a PTFB block, thickness 1.5zwm, dimensions 1000x550
Use a sheet with a diameter of 0 mm and 100 m in the long direction of this sheet.
Rolling was performed using rolling rolls at intervals of m.

In this case, the pressure is 501qr/aa, the temperature is room temperature,
Thickness variation is 10%.

Through this processing, the PTFE sheet was formed into a bellows shape, and by heat welding both ends of this sheet with PFA interposed, a fluororesin bellows could be obtained.

[Brief Description of the Drawings] Fig. 1 is a sectional view of a main part showing an embodiment of the present invention, and Fig. 2 (
A) and (B) are cross-sectional views showing an example of the method of the present invention, FIG. 3 is a cross-sectional view showing how the same embodiment is used, and FIG. 4.5 is a cross-sectional view of essential parts showing other examples of the present invention. Figure 6.7 shows
FIG. 2 is a sectional view of a main part of a conventional synthetic resin bellows. 10... Fluororesin bellows, 11... Bellows body, 13... Convex roll,
14... Concave roll, 22... Corrosion resistant ring,
S...Fluororesin sheet, T...Tanibe, Y...
...Yamabe. Agent Patent Attorney Toshibe Meki Figure 1 Figure 3 Figure 2 (A) Figure 2 (B) 14'' Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1) In a fluororesin bellows having a bellows body in the shape of an accordion that expands and contracts in the axial direction and in which peaks and valleys are formed alternately, the ridgeline part of the peak is thinner than other parts. A fluororesin bellows configured to. 2) The fluororesin bellows according to claim 1, characterized in that a corrosion-resistant ring is interposed inside the peak. 3) In a method for manufacturing a fluororesin bellows having a bellows body that expands and contracts in the axial direction and has alternating peaks and troughs, a cylindrical fluororesin sheet is rolled from the inside and outside into a convex roll. and a concave roll, the fluororesin sheet is rolled at predetermined intervals so that the ridgeline portion of the mountain portion is thinner than other portions. Method for manufacturing resin bellows. 4) In a method for manufacturing a fluororesin bellows having an accordion-shaped bellows body that expands and contracts in the axial direction and in which peaks and valleys are formed alternately, a flat fluororesin sheet is rolled from both sides into a convex roll and a concave roll. By applying pressure by
The fluororesin sheet is rolled at predetermined intervals, and then both ends of the fluororesin sheet are joined, so that the ridgeline portion of the mountain portion is thinner than other portions. Method for manufacturing fluororesin bellows.