DE2406530A1 - Restrictor valve with elastic valve tube - has varying wall thickness of tube to produce uniform bending stress - Google Patents

Abstract

A restrictor valve has an elastic valve tube held inside a rigid sleeve by two flanged rings. By pressurizing the space between the sleeve and the valve tube, the tube is deflated towards its axis, thus closing the valve. Since the areas where the tube is held by the flanged rings experience the highest bending moment, it is the region where the tube fails first. To prevent this weakness, the tube wall is tapered with increasing thickness towards the ends. This produces an approximately equal bending stress over the whole tube length, thus increasing its useful life.

Description

Dipl.-Ing. L. Uiisrt

Patent engineer February 11, 1974

6 9 01 nut jJLCJi

Odenwaldstrasse 4 2A06530

Apparate-Spezial-Technik GmbH & Co. 69OO Heidelberg

Pinch valve

The invention relates to a pinch valve. as Pinch valve is the name given to valves whose flow opening is locked by pressing the andung together. Such valves usually consist of an outer jacket made of steel or another metal and an insert tube made of rubber or a similar elastic material. That Insert tube is inserted into the outer jacket in such a way that a cavity remains between the two. This cavity is through a Line in which a shut-off valve is installed, with a compressed air source tied together. The shut-off valve is designed as a three-way valve, so that the cavity between the outer casing and the seed zrohr is connected to the outside air or to the compressed air source, depending on the position of the tap. Instead of compressed air can pressurized oil or water can also be used as a pressure medium. Pinch valves are mainly used in the chemical industry and related in the food industry, where there is a touch of the flowing liquid want to avoid having complicated fittings.

To a tight and at the same time, firm connection of the elastic To obtain insert tube with the rigid outer jacket, the inside of the end flanges of the outer jacket is gradually expanded and grooved. A mating flange is placed on the end flange with one facing the inside of the valve projecting pipe socket, the outer jacket of which is tapered inwards. This design of the insert tube and its connection with the outer jacket proved to be completely sufficient at pressures of up to about two to three atmospheres. at However, the insert tube was at higher pressures

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relatively sharp edge of the pipe socket of the counter flange pushed around and sheared off.

The invention was based on the task of the end pieces of the elastic insert tube and its connection with the rigid outer jacket of the valve in such a way that the insert tube can also be used at higher pressures, e.g. 4 to 6 atmospheres, does not tear off and the tight connection with the outer jacket is maintained even at these pressures.

According to the invention is in a pinch valve, which consists of a rigid outer jacket and an insert tube made of rubber or an equivalent material, the insert tube is designed so, that it is increasingly thickened at both ends.

Due to the thickening of the ends of the elastic insert tube, the inwardly occurring when the wall is bent Elasticity stresses so great that even higher compressed air pressures are not sufficient to cause dangerous deformation of the end piece to effect. Even when using a counterflange similar to the one that has been customary since then with an internal pipe attachment, there is therefore no There is a risk of squeezing or tearing off the elastic insert tube.

The transition from the cylindrical, inner part of the insert tube to the end face can take place in various ways. That's the way it is For example, it is possible, with the internal diameter remaining the same, to gradually increase the external diameter of the insert tube after the end to enlarge. The transition from one level to the next is appropriately rounded off so that no cracks can occur at these points.

A shape in which the end piece assumes the shape of a hollow cone should be even more favorable. Here the cross section takes of the thickened part steadily and adapts to the bending moment that increases after the clamped end,

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thereby reducing the bending stresses in all cross-sections assume an approximately constant value perpendicular to the axis.

You can also use these values for individual cross-sections from Calculate the beginning of the thickening to the end and then get roughly the shape for the outer surface line of the thickening of a parabola section.

The strength of the thickening at the extreme end depends on the bending stress that is to be allowed in the thickened end. Three to four times the wall thickness in the middle is suggested as a favorable value.

Towards the inside of the valve, the thickening should extend so far that the stretched cylindrical part can be bent over to a groove is not possible. According to the inventor's proposal, this condition can be met if the Thickening of an end piece extends over at least a third of half the length of the jacket.

In the case of a hollow cone-shaped thickening, this condition can also be met if the surface line of the thickening coincides with the extended surface line of the cylindrical part forms an angle of about .15 °.

The connection of the elastic insert tube to the rigid outer casing of the valve can be carried out in the conventional manner will. The turning of the end flange of the outer jacket is adapted to the outside of the thickening and with it Provided with grooves. A counter-flange is then pushed over the thickening, which receives the end of the thickening in a recess and at the same time grips behind the inside of the thickening with a pipe attachment. In this way, the one hand the end of the thickening in the recess of the counter flange, on the other hand, the thickening itself against the grooves of the end flange pressed, when designing it is important to that caused by the pipe socket of the counter flange

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" K -

Reduction in cross-section of the thickening is compensated for by adding an appropriate amount on the outside.

A simpler and very durable connection of the thickening of the insert tube with the end flange of the outer jacket is obtained one, according to a further idea of the invention, when the insert tube is formed in longitudinal section so that the Thickening runs out into an annular flange. Slipping out of the thickening from its holder is practically impossible here, especially when a steel ring is embedded in the ring flange.

A particular advantage of the pinch valves can be seen in the fact that that approaches that are deposited on the inner wall of the valve body, due to the deformation of the insert tube The opening and closing are made to flake off and then washed away by the liquid flowing through. This Advantage can, however, also have a detrimental effect if liquids are to be conveyed through the valve which the elastic inner body made of rubber or a rubber-like one Attack the fabric, and the inner body should therefore be provided with a protective layer. As a very good tool for one Teflon has proven to be a coating to protect against various acids.

Several exemplary embodiments of the invention are shown in the figures. Show it:

Figure 1 is a longitudinal section through a pinch valve

with the currently usual connection between insert tube and housing;

Figure 2 is a longitudinal section through an end piece of the

Insert tube with gradual enlargement of the cross section and its connection with the housing;

FIG. 3 shows a longitudinal section through the end piece of an insert tube with a conical thickening and subsequent housing part;

Figure h shows a longitudinal section through an end piece of the insert tube with a parabolic course of the outer surface lines and subsequent housing part.

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The valve consists essentially of a housing 1 made of steel or a similar rigid material and an elastic insert tube 2. The insert tube is made of rubber or an equivalent material. Housing and insert tube are designed so that they leave a cavity 3 between them. This cavity is connected to a compressed air source by a compressed air line k. The insert tube terminates at its ends in end pieces 12 and 22, the design of which essentially forms the content of the invention. The housing is provided with ring flanges 11, 21 at both ends. The connection of the pipe insert to the housing is effected by counter flanges 5 and 6, which are pressed against the end flanges 11 and 21 by connecting screws 7 and 17 and thereby clamp the end pieces 12 and 22 of the insert pipe 2 between them.

In order to prevent the end pieces 12 and 22 from slipping out of their holders, the end flange of the housing and the counter flange in the embodiment according to FIG. 2 and the transition from the housing to the end flange in the embodiment according to FIG. K are grooved. The pipe attachments 15 and 16 on the mating flanges serve the same purpose and press the end pieces of the insert pipe into the flange recesses 25, 26 (Fig. 1 and 3) or against the inner wall of the housing (Fig. K) .

Another form of connection is shown in FIGS reproduced. In both cases, the thickened end piece merges into an end flange 8. The flange 8 lies in recesses of the end flange 21 on the one hand and the counter flange on the other hand and is there by pressing the two together Flanges held. In both cases, the evasion inward is made practically impossible by the fact that at the flange ring connects to the inside to form a ring of great thickness, which is not compressed under the usual pressures can be. The moment of resistance is increased in Figure 3 by a steel ring insert 18 and by the pipe attachment of the counter flange against which the end piece is supported.

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The end piece 22 of the insert tube i.e. the transition from the thin cylindrical part 13 in the end flange 8 or in the The end face can be designed in various ways. Thus, in FIG. 2, the ring cross-section of the end piece 22 increases in steps to. The stages are labeled 9. The transition from one step to the next is rounded to avoid tearing To prevent bending of the upper part of the end piece inward. In the embodiment according to FIG. 3, the ring cross-section increases steadily, i.e. the end piece is designed in the form of a hollow cone. The surface line of the conical part 22 forms Here, with the extended surface line of the cylindrical piece 13, an angle 14, of about 15 · Again another Figure 4 shows the shape, in which the surface lines of the end piece run approximately in the form of a parabola.

With all cross-sectional shapes of the end piece, the section modulus increases after the end too. This reduces the deflection and you get a steady transition to that central cylindrical part on which the walls of the insert tube are supported against each other when the valve is closed.

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Claims (12)

• τ * Patent claims (1J A pinch valve consisting of a rigid outer jacket and an insert tube made of rubber or an equivalent material, characterized in that the insert tube (2) is increasingly thickened at both ends (12, 22). 2. Pinch valve according to claim 1, characterized in that the thickening (22) is step-shaped, 3. Pinch valve according to claim 1, characterized in that the thickening (22) has the shape of a hollow cone. 4. pinch valve according to claim 1, characterized in that that the outer surface lines of the thickening (22) are parabolic. 5. Quetseh valve according to claims 1 to k _t, characterized in 'that the width of the thickening (22) at the outermost end is about three to four times the ¥ and thickness of the middle part (13). 6. Pinch valve according to one or more of claims · 1 to 5 », characterized in that the thickening of an end piece (22) extends at least over a third of half the jacket length. 7. pinch valve according to claims 1 and 3 » characterized in that the surface lines of the thickenings (12, 22) form an angle (14) of about 15 with the extended surface line of the cylindrical part (13). j 8. pinch valve according to claims 1 to 6, characterized in that the thickening ends in an annular flange (8). 509335/0027 V * 240653Ό 9. squeeze valve according to claims 1 to 8, characterized in that in the annular flange (8) is a steel ring (18) is embedded. 10. Pinch valve according to one or more of claims 1 to 9, characterized in that the mating flanges (5 »6) have a wide annular groove (26) on their front side, which on the outside by a concentric to the valve axis running cylindrical ¥ and (27 ) »Is limited inside by a conical ¥ and (28), which is also concentric to the valve axis, of a pipe extension (16) protruding over the front of the flange. 11. Pinch valve according to Claims 1 to 8, characterized in that the annular flange (8) is provided with grooves on both sides in a manner known per se, into the toothed rings (19) of the flange (21) of the outer jacket and toothed rings (20 ) of the counter flange (6) engage, 12. Pinch valve according to one or more of claims 1 to 11, characterized in that the inner wall of the insert tube is coated with Teflon. 509835/0027 1 . Blank page