JPS60113875A - Pinch valve - Google Patents

Abstract

PURPOSE:To improve mechanical durability of a pinch valve by forming a pair of opposite thin wall portions at the central part if a flexible tube to alternately produce Z-shaped and S-chaped bending seal through initial pressure contact with difference in positin of the thin wall portions on every pressure receiving. CONSTITUTION:A cylindrical body l has a take-in port 2 for pressurized air, and a concentric cylindrical flexible tube 3 is mounted in the interior of the body. Bothe ends of the tube 3 are blocked up airtightly at flange portions, and a pair of thin wall portions 3a, 3a vertically confronting each other are formed in the vicinity of the central poriton of the tube. When pressurized air is pressed into the take-in port 2 of a pinch valve, buckling is caused at thin wall portions having relatively lower strength than the other thick wall portions 3b so that the thin wall portions are pressed to each other. When the thin wall portions are further pressureized, the thin wall portions cause a difference in position to block up the tube all over the surface with the Z-shaped bending seal. After the pressurized air is discharged, on pressing the pressurized air into the take- in port. S-shaped bending seal is caused by redidual stress.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention installs a cylindrical flexible tube inside a cylindrical body having a pressure air intake, and opens the flow path by crushing and restoring the flexible tube. This relates to improvements to pinch valves.

In the pinch valve, the flexible tube 5 is regarded as a kind of cylinder with a constant circular shape at both ends, and the operating air pressure is regarded as external pressure, and the suitability of the valve including its sealing mechanism is evaluated using buckling theory. can be judged.

'rJ, that is, L: length of the cylinder, r: average radius of the cylinder, n: buckling wave number, then A/r is too large (if n=2, if small, n, 3) ．4゜・・・・・・
・This is the result. Note that this buckling wave number n corresponds to the crushing number of the flexible tube in a pinch valve. Therefore, if n=3 or 4, the cross-sectional shape will be three-fold or four-fold as shown in Fig. 6 or 7, and an unusual tangent surface, that is, a dead space 6, will exist in the center. This is undesirable as it becomes the main cause of liquid leakage.

Therefore! , /r needs to be large. However, if the sides are made longer, the amount of air to be operated will increase, piping work will be difficult, and the weight will increase, so it is not suitable in practice. Therefore, L at n = 2
It can be said that the minimum value of /r is theoretically the most preferable. In addition, in order to make L/1゛ the minimum at o-2, α-1/
12(t/r), it is theoretically known that this α should be made as large as possible, and from this point of view, t
It is desirable to increase . Note that t is the wall thickness of the cylinder. However, if this t value is increased, the buckling limit pressure becomes higher, which again leads to an increase in the amount of operating air as described above, and this also poses a problem.

By the way, in a pinch valve, while the opening and closing operations are performed by the above-mentioned flexible tube, in terms of actual sealing performance, it is physically greatly affected by the body that surrounds this flexible tube. It is.

In other words, as shown in Fig. 8, in the case of a pinch valve, which is the most primitive type of valve, in which a coaxial cylindrical flexible tube 5 is attached inside a cylindrical body 7, the body and Due to the minute gap 8 that exists between the flexible tubes, primary buckling of two folds facing each other vertically is initiated when pressure is received, but as shown in FIG. The left and right outer peripheral surfaces 5a and 5b extended by the body inner wall surface 7
After contacting point a, if the pressure is applied even higher, secondary buckling will start, which is different from the above-mentioned primary buckling in which the upper and lower sides face each other, and progresses to the so-called 3-fold or 4-fold buckling mode described above. will be done. (See Figures 6 and 7). Therefore, in order to ensure sealing performance, a higher pressure than necessary is required, and a buckling form is created in which a dead space is present, which is the main cause of liquid leakage, which is extremely unfavorable in terms of valve characteristics.

On the other hand, as a solution to this problem, pinch valves have been widely used in which a flexible tube opens and closes without being affected by the body surrounding it during the buckling process. For example, it is as shown in FIG. That is, it is a pinch valve in which the body 10 at the opening/closing portion 9 of the flexible tube is formed into a spherical shape, and the gap between the flexible tube 5 and the body 10 is made as long as possible. This type of so-called spherical pinch valve has a spherical part in the body as mentioned above, which leads to an increase in internal volume, and even if it is subjected to vertical buckling, , the flexible tube extending in the left and right directions has a degree of freedom and is never pressed against the inner wall surface of the body.
What is shown in Figure 1 is that a completely press-welded state with two folds was obtained.

Therefore, the sealing performance is good in that the entire surface is closed by the primary buckling, and the amount of operating air is also advantageous to be approximately constant. However, on the other hand, this relatively long gap gives the flexible tube 5 a degree of freedom to move outward in the radial direction, so that when it is fully opened, it is strongly influenced by internal pressure, that is, fluid pressure, and expands. This has led to new problems such as permanent deformation of the flexible tube and accelerated mechanical aging. Moreover, over time, this phenomenon becomes the cause of the transition to the three-fold and four-fold buckling forms described above, and there is no tendency for the sealing performance to deteriorate, and the flow path shape is restored to its original shape. However, it has the disadvantage that it does not interfere with the flow of fluid. Furthermore, as the internal volume of the body increased, the overall size of the valve increased by 11 it, which caused handling and economical problems.

In this respect, the so-called U-shaped pinch valve disclosed in Japanese Patent Publication No. 47-3936 has a cylindrical rubber membrane 11 with one semicircumferential portion parallel to the tube axis direction, as shown in FIG. 12. It adopts a configuration in which cords 12 are arranged and buried, and the cylindrical rubber membrane is restrained in the radial direction by an exterior body 13, one semicircular part is restrained in the axial direction by a reinforcing cord 14, and the other half is restrained by a reinforcing cord 14. The semi-circumferential portion of the two semi-circumferential portions can be very easily overlapped with the inner surface of the other semi-circular portion for a tight seal. This is a so-called U-shaped folding seal mechanism as shown in FIG. Therefore, buckling changes such as three-fold or four-fold bending over time are prevented from occurring, and the influence of internal pressure, that is, fluid pressure, is almost eliminated, ensuring valve characteristics with excellent sealing performance.

However, even in this pinch valve, only the other semi-circumferential part undergoes repeated buckling movements with an extremely large amount of displacement, and is pressure-sealed to the one semi-circular part which is in a fixed and stationary state, so from the perspective of aging. Therefore, the durability was not yet satisfactory and the mechanical fatigue resistance was extremely high. Moreover, in order to obtain a good seal, this type of valve needs to be relatively long in the tube axis direction compared to the previous spherical type pinch valve, which is accompanied by unfavorable design regulations. There was a problem with that.

Therefore, the present invention is based on the above-mentioned buckling theory and a series of improvement processes to provide a pinch valve having the most suitable valve characteristics. In other words, the purpose is to always ensure buckling wave number n = 2 without causing changes over time, to provide good sealing performance, and to ensure a stable flow path shape that can be freely designed. It is also an object of the present invention to provide a pinch valve that has a structure that can suppress mechanical fatigue as much as possible, thereby further improving durability.

The feature is that the pinch valve is equipped with a cylindrical flexible tube inside a cylindrical body with a pressurized air intake, and opens and closes the flow path by crushing and restoring the flexible tube. A pair of thin-walled portions facing each other are formed near the center of the flexible tube, and the thin-walled portions are self-varied each time pressure is received, and the thin-walled portions are alternately Z-broken through initial pressure welding with mutual displacement.
This is where the S-resistance seal is repeated and the entire surface is closed by transfer pressure contact between the buckling surfaces.

Specific embodiments will be described below with reference to the drawings.

First, in Fig. 1, reference numeral 1 denotes a cylindrical body having a pressure air intake 2, and a concentric cylindrical flexible tube 3 inside the body.
is installed. Both ends of the flexible tube 3 are tightly sandwiched between flanges, and a pair of thin-walled portions 3a and 13a' are formed near the center of the flexible tube 3, which are vertically opposed to each other. As shown in Fig. 2, the thin-walled portions 3a and 3a' are formed by equally horizontally cutting out the upper and lower surfaces of the flexible tube 3, with the thickness being the minimum at the center and increasing symmetrically toward both sides. The structure is adopted. Note that 3b is a thick portion. Further, 30 is a flexible tube 3 as shown in FIG.
from the thick wall portion 3b at both ends of the thin wall portion 3a, 3a.
' It is a thin sloped part formed towards '.

Inlet 2 for operating air into the pinch valve configured as above.
If it is press-fitted with pressure P from , first as shown in Figure 5A,
A thin wall portion 3a having relatively lower strength than other thick wall portions 3b,
Buckling starts from 3a'.

That is, initial buckling. This initial buckling gradually
It progresses so as to take in the thick interior 3b on both sides centering around a and 3a', and the received pressure is generally absorbed by this buckling. In other words, the thick portion 3b is prevented from elongating to the extent that the left and right end points a and b of the thick portion strongly press against the inner wall surface 1a of the body. Note that 4 is a flow path. Further, BL indicates the progression line of the virtual center points b1 and bl' of the initial buckling, that is, the initial buckling line, and TL indicates the joining line between the virtual center points of the thin portions 3b and 3b', t+'. The center line of the thin straw part is shown. As shown in the figure, it is recognized that the initial buckling progresses along the thin wall center line TL.

Next, the progress of this initial buckling is completed by pressure contact between the pair of upper and lower thin-walled portions 3a and 3a' that face each other, as shown in FIG. 5B. That is, this is initial pressure welding. This initial pressure contact is caused by the initial contact surface ip having a certain width, but as shown in FIG.
, 3a' A mutual shift occurs in a certain direction.

That is, the thin-walled portion center line TL shifts to an angle θ with respect to the initial buckling line BL. Note that this direction of deviation is considered to be based on the quality of the flexible tube, slight errors in deformation, etc. that occur during manufacturing.

Therefore, as shown in the fifth diagram, the left and right balance is lost, and the buckling occurs in the direction of low strength in the thin wall portion 3a, that is, the virtual center points t1, t1' of the thin wall portion with a high wall thickness ratio with the initial buckling line BL as the border. direction, so-called positive deviation direction A
On the other hand, in the thin section 3a', the shift direction B is the opposite direction.
It progresses to So-called secondary buckling begins. It should be noted that this secondary buckling progresses by transition pressure welding of the buckling surface in which the pressure contact state at the initial pressure contact surface ip is roughly maintained and the peak of the peak moves without slipping. (See Figures 5E and 5F).

FIG. 5G is a schematic cross-sectional view showing a state in which the progress of this secondary buckling has been completed and the entire area is closed by a so-called type 2 folded seal. Here, the X mark indicates the location where the flexible tube 3 has the greatest elongation under this condition.

Next, in the case of exhaust operation, the return progresses due to the internal pressure (fluid pressure) or the self-restoring force of the flexible tube in the opposite process to the press-in process described above, and the so-called normal state of excessive progress is caused. The excess expansion of the flexible tube in the radial direction is completely stopped by the body surrounding the flexible tube, and the same normal state when unbuckled as described above is reached and stabilized. (See Figures 5H to 5J.) In this case, please refer to Figure 5J.
As shown in FIG. 2, residual stress R8-Z remains at the location X where the maximum elongation occurred under the completely closed state of the flexible tube 3.

Therefore, when the valve is subsequently fully opened again, this residual stress R3-Z is applied to the thin wall portions 3a, 3a
If the stress is greater than that of the thinnest part of ', it will be pressurized and dented, and buckling will begin from this residual stress part. This buckling is referred to as primary buckling with respect to the above-mentioned initial buckling.

In Figure 5, the primary buckling in FL is the thin wall center line TL.
FIG. 2 is a schematic diagram showing a state in which buckling progresses at an angle δ.

Therefore, as shown in Figure 5, the initial pressure contact surface ip is formed with a deviation completely opposite to that which occurred during the above-mentioned process, and the thin wall center line TL is equivalent to the angle θ mentioned above. Alternatively, it will be tilted in the opposite direction at approximately the same angle θ'. Therefore, secondary buckling progresses in the displacement direction B opposite to the positive displacement direction A mentioned above in the thin wall portion 3a,
It proceeds in the positive deviation direction A at the thin portion 3 a + . Note that the mechanism of this buckling progress is the same as described above.

FIG. 5M is a schematic cross-sectional view showing the progress of this secondary buckling, and FIG. 5N is a schematic cross-sectional view showing the completely closed state after the progress has been completed. This state of complete occlusion is the above-mentioned Z
It has an S-shaped folding seal structure that is completely symmetrical to the folding seal.

Note that under this condition, the maximum elongation X exists at a position completely opposite to the above-mentioned Z-bending seal, and the next time the exhaust operation is performed, it will completely return to the non-buckling state as in the above-mentioned process. However, this time, the residual stress R8-3 is generated at an oppositely symmetrical position corresponding to the elongated position (see FIG. 5O). (See FIG. 5, P) Needless to say, the return to normal state is achieved by internal pressure (fluid pressure) or the self-restoring force of the flexible tube.

Therefore, in the case of a severe press-fitting operation, the seal is completed by a buckling process that is completely opposite to the buckling process for the S-shaped folded seal described above.

Thereafter, as the air is repeatedly injected and exhausted, the buckling cycle of S-shaped bending and the buckling cycle of Z-shaped bending occur alternately.In other words, the memory seal mechanism of two-cycle fluctuation occurs in the flexible tube. Constantly internal fittings (made with pongee.

Note that FIG. 3A is a sectional view showing a state closed with a Z-shaped folding seal, and FIG. 3B is a sectional view showing a state closed with an S-shaped folding seal.

By the way, although the flexible tube 3 in the above embodiment is formed by horizontally cutting out the thin wall portions 3a and 3a', the present invention is not limited to this.

For example, as shown in FIG. 4, it may be formed to have a uniform thickness; in short, it is appropriate to form a thin wall portion that is symmetrical with respect to the longitudinal axis of the flexible tube.

Further, as shown in FIG. 1, the thickness t1 of the thin portions 3a and 3a' is approximately 1/2 of the thickness t2 of the thick portion 3b on average.
Although the degree is appropriate, it is not limited to separate installation. That is, in addition to the width L1 of the thin wall portion and the width A2 of the thin slope portion 3c, buckling can be easily achieved depending on various factors such as the wall thickness t2 of the thick wall portion or the material. There is no problem as long as you specify the scope of gain.

In addition, the above embodiments are Z type-8 type-Z type...
Although a sealing mechanism that repeats the following is adopted, mechanisms such as S-type, Z-type, 8-type, etc. can also be adopted, and the sea fence is not limited to this.

Incidentally, in the above example, the operating pressure was 0 to 4 kg/c+
As a result of repeating the test 20,000 times as n2, it was found that the buckling wave number always remained at n-2 without causing any change over time, and that it had a stable flow path shape and good sealing performance.

As described above, the pinch valve according to the present invention completely restricts the expansion of the flexible tube in the radial direction by installing the cylindrical flexible tube inside the cylindrical body. Due to further acceleration of mechanical aging and permanent deformation mainly caused by internal pressure (fluid pressure), which has been a problem with so-called spherical side pinch valves, buckling changes such as 3-fold or 4-fold bending occur over time. There was no risk of the process progressing, and moreover, a stable flow path shape could be ensured. Furthermore, since a pair of thin-walled parts facing each other is formed near the center of the flexible tube, the initial buckling always starts from these thin-walled parts, and moreover, the flexible tube self-varies every time pressure is received. The Z fold-8 type bending seal was alternately repeated through the initial pressure welding with mutual displacement of the thin wall parts, and the entire surface was closed by the transfer pressure welding between the buckled surfaces. An independent and independent type of buckling regulation has been established that completely eliminates undesirable influences from the surrounding body.

Furthermore, since the structure does not require extremely concentrated displacement in a specific location, the degree of mechanical fatigue is significantly lower than that of conventional so-called U-bending pinch valves, resulting in significantly increased durability. It is. In addition, the pressure contact between the buckled surfaces is completely closed, and the seal structure is such that they engage with each other, so the sealing effect is exceptionally superior compared to conventional ones. As such, its sealing performance does not depend on the dimension in the tube axis direction, and it has the advantage of being flexible in design. In addition, it is naturally lighter in weight than a spherical side pinch valve, and is convenient to handle during piping work.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing one embodiment of the pinch valve according to the present invention, Fig. 2 is a cross-sectional view taken along the line n-n, and Fig. 3 Δ shows the closed state of the Z-fold seal in Fig. 2. Figure 3B is a horizontal cross-sectional view showing the closed state of the S folding seal.
FIG. 4 is a sectional view showing another embodiment of the flexible tube, and FIGS. is the buckling cycle of Z-shaped bending, and J to P are the buckling cycles of S-shaped bending. Note that A is the initial buckling start state, B is the initial pressure welding state,
C is the mutual misalignment state of the thin wall parts, D is the start state of secondary buckling,
E and F are the progress states, G is the Z failure seal state, 1
- (and J is the progress state of return due to exhaust operation, J is the normal state of completion of return, K is the starting state of primary buckling due to residual stress, L is the initial pressure welding state, M is secondary buckling , N is the S-shaped folded seal state, 0 is the progress state of return due to exhaust operation, and P is the normal state of completion of return. Fig. 7 is a schematic sectional view showing a four-fold buckling form, Fig. 8 is a longitudinal sectional view showing an example of a conventional primitive type pinch valve, Fig. 9 is a schematic sectional view taken along the ■-IX line, Fig. 10 is a longitudinal cross-sectional view showing an example of a conventional so-called spherical pinch valve, and Fig. 11 is a cross-sectional view taken along the line XI-X, showing a state in which the flexible tube is folded in two and is occluded. Fig. 12 is a schematic sectional view showing an example of a cylindrical rubber of a pinch valve related to a conventional so-called U-bending seal, and Fig. 13 is a schematic sectional view showing the progress of buckling of the U-bending with the rubber installed. 1...Body 2...Pressure air intake 3...
Flexible tubes 3a, 3a'...thin wall portion 3b...
・Attack Department Attorney Yasushi Oshima Figure 2 2 Figure 3 Figure 4 FG Figure 6 Figure 7 Figure 8 Figure 9 Figure 11 ■ Figure 12 Figure 13 Voluntary procedure amendment form 1. Indication of the case Patent application No. 2184624 filed in 1982 2. Name of the invention Pinch valve 3. Person making the amendment Relationship to the case Patent applicant 1 Co., Ltd., 446 Otani, Hino-cho, Gamo-gun, Shiga Prefecture
Okumura Manufacturing Representative Kiyoshi Okumura - 4, Agent 550 1-25-30 Edobori, Nishi-ku, Osaka-shi Attached drawings subject to amendment. 6. Contents of amendment Figures G and N in Figure 5 will be amended as shown in the attached drawings. Figure 5

Claims (1)

[Claims] (1) In a pinch valve in which a cylindrical flexible tube is installed inside a cylindrical body having pressure air intake [1] and the flow path is opened and closed by crushing and restoring the flexible tube, the above-mentioned A pair of thin-walled portions facing each other are formed near the center of the flexible tube, and the thin-walled portions are self-varied each time pressure is received, and Z-shaped folds and three-shaped folded seals are alternately formed through initial pressure welding with mutual displacement of the thin-walled portions. A pinch valve characterized by being completely closed by repeated displacement pressure contact between buckling surfaces.