Backflow preventer for an airflow channel

Description

[0001] The invention relates to a backflow prevention device for a flow channel through which an airflow flows, comprising a housing through which the airflow flows in an outflow direction and which has an outflow opening that can be closed with a locking flap pivotally mounted on the housing, wherein the housing is sleeve-shaped and has an inflow opening opposite the outflow opening, wherein the housing can be arranged in a hollow cylindrical flow channel with a sealing flange extending circumferentially around an outer wall of the housing, so that an airflow flowing through the flow channel in the outflow direction flows into the housing through the inflow opening and out of the housing through the outflow opening.wherein the shut-off flap, in a shut-off position, rests against an opening edge of the outlet opening, closing the outlet opening and preventing unwanted backflow against the outflow direction into the outlet opening, wherein the shut-off flap, in an open position, is pivoted away from the opening edge and releases the outlet opening for an airflow flowing through the housing in the outflow direction, and wherein the opening edge of the outlet opening has a hinge area in which the shut-off flap is pivotably mounted on the housing, which transitions into a shut-off flap stop area arranged opposite in the circumferential direction and which is offset in the outflow direction.

[0002] It is known from practice that such a backflow prevention device can be arranged in a flow channel through which an airflow flows, in order to allow the airflow flowing through the flow channel in the intended outflow direction to pass through the backflow prevention device with as little impairment as possible, but to block the flow channel for a counterflow flow flowing against the outflow direction through the flow channel and thereby prevent a counterflow flow flowing against the outflow direction through the flow channel from passing through the backflow prevention device into an area of ​​the flow channel located behind the backflow prevention device.

[0003] Such backflow preventers can be used, for example, in exhaust systems and arranged or installed in an exhaust duct through which an exhaust gas flow passes. The exhaust gases generated and expelled by a heating system can flow through an exhaust duct in the predetermined outflow direction and pass through the backflow preventer located in the exhaust duct. The exhaust gases flow in the outflow direction through the exhaust duct and through the housing of the backflow preventer located therein, pivoting the shut-off valve into an open position. However, the backflow preventer prevents an unwanted backflow of exhaust gases through this exhaust duct towards the heating system, as the shut-off valve automatically moves from an open position to its closed position and closes the outflow opening as soon as no more airflow passes through the housing in the outflow direction.If a backflow of air against the direction of flow through the exhaust duct reaches the backflow prevention device, the flap is additionally pressed against the edge of the outlet opening in its locking position by the backflow of air against the direction of flow, thus reliably closing the outlet opening.

[0004] Various designs of such backflow preventers are known from practical experience. These designs employ different shapes of the housing and the flap, as well as different bearing mechanisms for the movable flap, to minimize the influence and obstruction of the airflow passing through the backflow preventer in the desired outflow direction, while simultaneously reliably blocking and closing off an airflow approaching the outflow opening of the backflow preventer against the outflow direction.

[0005] The backflow preventers described, for example, in DE 38 06 325 A1, EP 1 544 544 A1, or AT 508 208 A1 each have a sleeve-shaped housing and a movable flap valve with which a flow channel passing through the housing can be shut off. However, these backflow preventers do not allow simple condensate drainage in a direction opposite to the outflow direction, since in this direction the flap valve blocks the outflow opening and prevents condensate from draining through the housing.

[0006] In DE 196 06 403 A1 a backflow prevention device according to the preamble of claim 1 is disclosed, in which condensate drainage is enabled by a siphon passing past the sleeve-shaped housing or by a bore through the housing wall and by a siphon arranged behind the housing.It is therefore considered an object of the present invention to design a backflow prevention device of the type mentioned at the outset in such a way that an airflow flowing through the backflow prevention device in the outflow direction can flow through the backflow prevention device as unhindered as possible, while a counterflow of air flowing in the opposite direction is reliably prevented or prevented from flowing through the backflow prevention device against the outflow direction, while at the same time any condensate that may accumulate on the backflow prevention device against the outflow direction should be able to be drained away in a space-saving and reliable manner.

[0007] This problem is solved according to the invention by the fact that the housing has a circumferential indentation which is arranged next to the outflow opening and is not closed by the shut-off valve, so that the indentation forms a condensate chamber when the housing is inserted into the surrounding flow channel, which is accessible from a direction opposite to the outflow direction, and that a flow opening is arranged in the indentation near the opening edge of the outflow opening, through which a condensate which accumulates in the condensate chamber bounded by the indentation can flow into an interior of the housing, bypassing the shut-off valve.

[0008] According to the invention, a flow opening is provided in the indentation near the edge of the outlet opening, through which condensate accumulating in the condensate chamber bounded by the indentation can flow into an interior space of the housing, bypassing the shut-off valve. Only after a quantity of condensate has accumulated in the condensate chamber and the condensate level in the condensate chamber has risen to the point where it reaches the flow opening, can the condensate flow from the condensate chamber through the flow opening into the interior space of the housing.

[0009] By adjusting the distance between the flow channel opening and the flow opening, a condensate column can be formed. This column, when the condensate chamber is completely full, creates resistance against the counter-flow of air flowing against the outflow direction towards the backflow preventer. The greater the distance between the flow channel opening and the flow opening, the greater the flow pressure of the counter-flowing air must be to force the condensate accumulated in the condensate chamber through the flow channel and the flow opening until a sufficient amount of condensate has drained from the chamber and the flow channel opening is clear for the counter-flow.

[0010] Since the indentation extends axially from the edge of the outlet opening towards the inlet opening and may extend as far as the sealing flange, a siphon can be formed with the flow opening located near the edge of the outlet opening. To prevent the flow opening from being accessible to a counterflow of air flowing against the outflow direction, one embodiment of the invention provides that an airtight flow opening channel extends from the flow opening towards the sealing flange in the condensate chamber, and that a flow opening channel outlet is located at a distance from the flow opening in the condensate chamber. As soon as the condensate level in the condensate chamber rises above the flow opening channel outlet, the flow opening channel is closed by the condensate collected in the condensate chamber.A counterflow of air approaching the backflow preventer against the outflow direction can then no longer bypass the shut-off flap into the interior of the housing and continue flowing in the flow channel against the outflow direction.

[0011] Optionally, it is advantageously provided that the indentation is arranged circumferentially in the hinge area and extends axially from an outer edge of the outlet opening towards the inlet opening, or up to the sealing flange. Since a circumferential edge of the flap in the hinge area should be spaced from the inner wall of the surrounding flow channel to allow for the widest possible opening movement of the flap, this area is particularly suitable for forming an indentation and the resulting condensate chamber.

[0012] Most backflow preventers are designed to be installed in vertically oriented pipe sections where air can flow either vertically upwards or vertically downwards. Because the opening edge of a backflow preventer installed in this way is not horizontally oriented, but rather the flap stop area is offset in the outflow direction, the flap is not horizontally positioned in a vertically oriented pipe section. This prevents liquid droplets from accumulating on the flap, which could impede its movement and the opening of the outflow.Furthermore, the damping flap, which is not horizontal but oriented at an angle of at least a few degrees, allows a portion of the force component directed in the flow direction of the damping flap's weight to be determined largely independently of the damping flap's own weight. This is achieved by the predetermined offset of the damping flap's stop area relative to the hinge area in the direction of airflow. This force component then determines the closing effect that presses the damping flap against the opening edge of the housing. With this closing effect, the damping flap is pressed against the opening edge of the outlet when there is no airflow, thus closing the outlet. This prevents unwanted backflow of air from passing through the non-return valve against the flow direction through an incompletely closed damping flap.For butterfly valves with a high dead weight, for example, the offset of the butterfly valve stop area can be set larger than for butterfly valves with a low dead weight, in order to achieve a comparably high contact pressure of the butterfly valve against the opening edge in both cases. This contact pressure can thus be easily specified, without additional return mechanisms or springs, depending on the butterfly valve used.

[0013] According to a particularly advantageous embodiment of the invention, the shut-off valve is made of an elastic plastic material and is designed and mounted on the housing in such a way that the outlet opening is closed by the elastically prestressed shut-off valve without any airflow passing through it. A shut-off valve made of an elastic plastic material can be formed in one piece and manufactured particularly cost-effectively. For example, a shut-off valve can be produced from a cut piece of plastic film or sheet. In particular, fluoroelastomers such as Viton® are considered a particularly suitable elastic plastic material due to their high temperature and chemical resistance.

[0014] Compared to a force-free flap, a flap made of an elastic plastic material is advantageously arranged such that the flap resting against the opening edge is elastically deformed, and the resulting restoring forces press the elastically deformed flap against the opening edge. In this way, with a flap that has a particularly low weight, a contact pressure against the opening edge of the discharge opening can be generated and controlled by the elasticity and shape of the flap.

[0015] Preferably, the locking flap comprises a fixing section for securing the locking flap to or on the hinge area of ​​the opening edge, and a pivoting flap section connected to the fixing section via a film hinge. The film hinge allows for the locking flap to be formed and manufactured in one piece. The fixing section can be used to fix and attach the locking flap to the housing. For example, the fixing section can be positively engaged or detented in the hinge area of ​​the housing. It is also conceivable that the fixing section is bonded or metallurgically joined to the hinge area of ​​the opening edge, for example, by welding using a conventional friction welding process or ultrasonic welding.It is not necessary to use an elaborate mounting of the locking flap on a pivotably mounted shaft or to use additional spring devices to generate sufficient contact pressure.

[0016] The hinge area of ​​the opening edge can have a contact surface oriented perpendicular to the outflow direction for the fixing section of the flap attached thereto, while the flap stop area is arranged offset in the outflow direction and thereby forces a deformation in the case of a flat-surface flap made of elastic plastic material, the restoring forces of which press the pivot flap section, which is oriented at an angle greater than 0° to the contact surface and the fixing section, against the opening edge.

[0017] According to one embodiment of the invention, a support ridge is arranged upstream of the flap in the outflow direction. The non-pivoting flap rests on this ridge, which extends transversely across the outflow opening. This ridge prevents unwanted pivoting or deformation of the elastic flap against the outflow direction in the event of backflow directed against the outflow opening. In the case of strong, unwanted backflow against the outflow direction, a flap made of an elastic plastic material could be deformed and forced into the housing against the outflow direction. The support ridge prevents such unwanted deformation against the outflow direction. The more elastic the plastic material of the flap, the wider or longer the support ridge can be.It can also be provided that two or more thin support ribs connect spaced areas of the opening edge and extend across the outflow opening in order to provide multiple support surfaces for the elastically deformable shut-off valve within the outflow opening.

[0018] According to a particularly advantageous embodiment of the invention, the flap valve has a dome-shaped bulge with an inner region that protrudes in the outflow direction. This dome-shaped bulge prevents liquid from accumulating on the dome-shaped outer surface of the flap valve, even if the flap valve is only slightly inclined, as this could impede its pivoting movement in the outflow direction.

[0019] It is expediently provided that the edge of the opening has a curved profile not only in the circumferential direction, but also in the outflow direction.

[0020] By designing the flap valve with a dome-shaped curvature and with an inner area that is bulged in the outflow direction, the flap valve, which is pivotably mounted on the housing, can be pivoted into an opening position in which the flap valve can lie close to an inner wall of the surrounding flow channel and protrudes only slightly into a flow cross-section limited by an inner side of the sleeve-shaped housing.

[0021] The opening edge, and consequently a circumferential edge of the flap adapted to it, expediently transitions continuously from the hinge area to the flap stop area, which is located opposite in the circumferential direction and offset in the outflow direction. Since the opening edge does not run perpendicular to the outflow direction, but rather transitions from a hinge area to the flap stop area located opposite in the circumferential direction and offset in the outflow direction, the circumferential edge of the flap is not perpendicular to the outflow direction or to a central axis of the sleeve-shaped housing.Accordingly, the shut-off flap is not mounted perpendicular to the inflow direction in its closed position, but rather at an angle to the outflow direction, resting against the edge of the opening. This angle is determined by the offset between the shut-off flap stop area and the hinge area in the outflow direction. Even a slight pressure difference, generated by an airflow passing through the housing in the outflow direction, lifts the shut-off flap from the edge of the sleeve-shaped housing, thus opening the outlet for the incoming airflow.The weight of the flap causes it to move from the open position to the closed position as soon as there is no sufficient pressure difference, or no airflow in the outflow direction through the housing of the backflow preventer.

[0022] Such a backflow preventer is particularly suitable for installation in a vertical section of an exhaust duct. The cross-sectional area of ​​the sleeve-shaped housing is advantageously adapted to the cross-sectional area of ​​the surrounding exhaust duct, so that the housing, with its circumferential sealing flange extending around its outer wall, can be tightly positioned within the exhaust duct. The sealing flange prevents air from flowing past the backflow preventer in a gap between the outer wall of the housing and the surrounding exhaust duct. The sleeve-shaped housing of the backflow preventer advantageously has a circular cross-sectional area, the diameter of which, in conjunction with the circumferential sealing flange, is adapted to the inner diameter of an exhaust duct that also has a circular cross-sectional area.However, it is also conceivable that the sleeve-shaped housing of the backflow preventer has a shape that deviates from a circular cross-sectional area and, for example, a rectangular or square cross-sectional area.

[0023] A bead-shaped locking flap seal is advantageously arranged along the edge of the opening, which consists of an elastically deformable material and seals the outlet opening airtight when the locking flap is pressed against the edge of the outlet opening.

[0024] An elastically deformable circumferential seal can also be arranged or fixed to the sealing flange that runs circumferentially around the outer wall of the housing. The circumferential seal can, for example, be an O-ring seal that is recessed in a circumferential groove located on the outer side of the sealing flange and projects slightly in the radial direction.

[0025] The sealing flange, which runs circumferentially around the outer wall of the housing, can optionally have a circumferential edge projecting radially outwards beyond a circumferential seal at one of its outer ends opposite the flap. During installation, this circumferential edge can act as a stop for the end of an exhaust duct pipe, thus limiting the depth of the backflow preventer when it is inserted into the pipe. Furthermore, a circumferential stop reliably prevents the backflow preventer from tilting within the surrounding exhaust duct, thereby avoiding unintentional impairment of the functionality of the pivotally mounted flap and, consequently, the backflow preventer itself during installation and maintenance work throughout its often very long service life.

[0026] According to one embodiment of the invention, the flap is pivotably mounted on the housing via a hinge, the hinge being offset radially inwards from an outer circumferential edge of the sealing flange. Due to its dome-shaped curvature, the flap, pivoted into the open position, projects with its convex inner area beyond the circumferential edge of the flap. If the hinge were arranged radially directly adjacent to the outer circumferential edge of the sealing flange, the dome-shaped curvature would limit the pivoting movement of the flap towards the open position by causing the convex inner area of ​​the flap to quickly strike the inner wall of the surrounding flow channel, and the flap would protrude comparatively far inwards into the flow diameter of the sleeve-shaped housing in the open position.The radial offset of the hinge from the outer circumferential edge of the sealing flange to the inside allows a comparatively wide pivoting and opening movement of the locking flap, which is pivotably mounted on the housing via the hinge, until the pre-curved inner area of ​​the locking flap rests against the inner wall of the surrounding flow channel.

[0027] Advantageously, the hinge can also be arranged on the outside of the flap, so that the opening edge of the outflow orifice in the hinge area has an even greater radial offset inwards relative to the outer circumferential edge of the sealing flange than the hinge. This additionally allows for an even greater pivoting movement of the flap into the open position.

[0028] To ensure the most reliable possible mounting of the flap valve in the hinge, the hinge optionally features at least one hinge pin receptacle with a radially outwardly directed hinge pin receptacle opening through which a hinge pin can be inserted and pivotably mounted. The hinge pin receptacle opening is located radially closer to the outer circumferential edge of the sealing flange than one diameter of the hinge pin. Before the backflow preventer is installed in a flow channel surrounding it, the flap valve must be mounted in the hinge on the housing. For this purpose, the hinge pin must be inserted through the radially outwardly directed hinge pin receptacle opening into the at least one hinge pin receptacle.Since, in the assembled state of the backflow preventer in the flow channel, the hinge pin receptacle opening is closer to the surrounding inner wall of the flow channel than the diameter of the hinge pin, the hinge pin cannot be moved out of the hinge pin receptacle after the backflow preventer is installed in the flow channel. In this way, the operational reliability of the backflow preventer located in the surrounding flow channel can be significantly improved with simple means.

[0029] For reliable bearing of the locking flap in the hinge, it is irrelevant whether the hinge pin receiving element with the radially outwardly directed hinge pin receiving opening is formed on the housing as described above, and the hinge pin is formed on the locking flap, or whether the hinge pin receiving element is formed on the locking flap and the hinge pin is formed on the housing. If the hinge pin receiving element is formed on the locking flap, the hinge pin receiving opening advantageously points radially inwards. Even in this configuration, the radial distance of the hinge pin receiving opening relative to the outer circumferential edge of the sealing flange is advantageously less than the diameter of the hinge pin.

[0030] To prevent unwanted tilting of the locking flap transversely to its pivot direction, the hinge expediently has at least two hinge pin receptacles spaced apart along a pivot axis. Either a single, sufficiently long hinge pin can be inserted into the at least two hinge pin receptacles, or a corresponding hinge pin section can be provided for each hinge pin receptacle, which can be inserted into the associated hinge pin receptacle.

[0031] Particularly in the case of a vertically oriented flow channel and an airflow that is warmer than the inner wall of the flow channel, as is regularly the case with exhaust systems and an exhaust flow in an exhaust duct through which it flows, it cannot be ruled out that some of the moisture carried in the airflow will condense on the inner wall of the surrounding flow channel and, following gravity, run down its inner wall. To collect the running condensate at the backflow preventer, which, due to the sealing flange fitting tightly against the inner wall of the flow channel, prevents further runoff of the condensate over the backflow preventer, a condensate chamber is provided by a circumferential indentation in the sleeve-shaped housing, in which the running condensate can be collected.

[0032] According to a particularly advantageous embodiment of the invention, it is provided that a curvature of the locking flap is adapted to an outer circumferential edge of the sealing flange in such a way that the locking flap can be pivoted as far as possible away from the opening edge in the direction of an inner wall of the surrounding flow channel in the open position, without projecting in a radial direction to the outer circumferential edge of the housing, which abuts the inner wall of the surrounding flow channel.In conjunction with the curved course of the opening edge of the outflow opening, which is also curved in the outflow direction, and the circumferential edge of the shut-off valve adapted to it, it can be achieved by suitable adaptation and specification of the curvature of the shut-off valve that the shut-off valve lies close to the inner wall of the surrounding flow channel in an opening position pivoted as far away as possible from the opening edge, whereby in the circumferential direction the course of the inner wall corresponds to the outer circumferential edge of the sealing flange.

[0033] It has been shown that a non-rotationally symmetrical damper exhibits particularly advantageous properties. The center point of the dome-shaped curvature is expediently located between a central axis of the sleeve-shaped housing and the hinge area of ​​the opening edge. The curvature itself is expediently designed such that the damper, when in the open position, obstructs the airflow through the sleeve-shaped housing in the outflow direction as little as possible and forces as little turbulence as possible around the damper when in the open position.

[0034] To ensure the most reliable operation of the backflow preventer even with increasing contamination of the flow channel, an optional outward-projecting stop element is provided on the outer surface of the flap, facing away from the housing. This element, by contacting an inner wall of the surrounding flow channel, limits the flap's pivoting movement into the open position. The outward-projecting stop element prevents the outer surface of the flap from coming into extensive contact with the inner wall of the surrounding flow channel and, in the event of contamination, from adhering to the inner wall of the flow channel.

[0035] An exemplary embodiment of the invention, illustrated in the drawing, is explained in more detail below. It shows: Figure 1a side view of a backflow preventer for a flow channel through which an airflow passes, Figure 2 a perspective side view of the backflow preventer, Figure 3 another side view of the in the Figure 1 and 2 The backflow preventer shown is viewed from another direction, showing a hinge area and a recess with a condensate chamber. Figure 4 a perspective view of the backflow preventer, Figure 5 a view through the backflow preventer in an outflow direction from an inflow opening facing the viewer through a housing of the backflow preventer, wherein a shut-off flap in an open position projects into an outflow opening facing away from the viewer, Figure 6a side view of the backflow prevention device, showing the locking flap in a locking position that blocks the backflow prevention device, Figure 7 a sectional view of the backflow preventer, which is arranged in a schematically represented surrounding flow channel, Figure 8 a side view of the housing of the backflow preventer without the pivotally mounted shut-off flap, Figure 9 a side view of the locking flap Figure 10 Another side view of the locking flap from a different direction, Figure 11 a side view of a variant design of a backflow preventer with a one-piece barrier flap made of an elastic plastic material, Figure 12 a sectional view through the in Figure 11 shown backflow preventer along a section plane XII-XII in Figure 11 , Figure 13A top view of the housing of the backflow preventer against the outflow direction, with the shut-off valve not shown for clarity. Figure 14 a top view of the shut-off valve in the Figures 11 and 12 illustrated backflow prevention device, and Figure 15 a sectional view through the in Figure 14 Shown shut-off valve.

[0036] One in the Figures 1 to 10 The non-return valve 1, shown in various views and in open or closed positions, has a sleeve-shaped housing 2 and a shut-off flap 3 pivotally mounted on the sleeve-shaped housing 2. The housing 2 has an inlet opening 5 at a first end 4 for an airflow passing through the sleeve-shaped housing 2 in an outflow direction. The outflow direction is indicated by two arrows 6. Figure 1indicated. At a second end 7 opposite the first end 4, the sleeve-shaped housing 2 has an outlet opening 8. The outlet opening 8 can be released by the pivotally mounted shut-off valve 3, as is the case, for example, in the Figures 1 to 5 as shown in 7, or be closed, as shown in Figure 6 is shown.

[0037] At the first end 4, adjacent to the inlet opening 5, a sealing flange 10 is formed, extending circumferentially around an outer wall 9 of the housing 2. The sealing flange 10 has an outer circumferential edge 11 projecting radially beyond the outer wall 9 and, immediately adjacent to it, a sealing groove 12, also extending circumferentially around the housing 2, for receiving an O-ring seal. The sealing flange 10 allows the housing 2 of the backflow preventer 1 to be positioned and fixed to an inner wall 13 of a surrounding flow channel 14 in such a way that an airflow passing through the flow channel 14 must flow through an interior space 15 of the housing 2 and cannot flow laterally between the outer wall 9 of the housing 2 and the inner wall 13 of the surrounding flow channel 14, as would occur in Figure 7The radially outwardly projecting circumferential edge 11 forms a stop and defines a depth limit for the inserted backflow preventer 1 when it is installed or inserted into a pipe section of the flow channel 14. This facilitates error-free and reliable quick installation and also prevents unwanted tilting of the backflow preventer 1 within the flow channel 14, which would impede the function of the pivotally mounted shut-off valve 3. The radially measured distance between the sleeve-shaped housing 2 and the surrounding flow channel 14 is shown for clarity in the figure. Figure 7 The image is shown as relatively large, but in practice it can be significantly smaller, or only 0.1 mm or 0.2 mm.

[0038] The outlet opening 8 has an opening edge 16 that limits the outlet opening 8. The opening edge 16 has a hinge area 17 in which the flap 3 is pivotably mounted on the housing 2. From the hinge area 17, the opening edge 16 transitions into a flap stop area 18 arranged opposite it in the circumferential direction. The flap stop area 18 is offset relative to the hinge area 17 in the outflow direction, with the opening edge 16 in the flap stop area 18 having a greater distance to the inflow opening 5 and the sealing flange 10 than the opposite hinge area 17. Consequently, the opening edge 16 has a curved profile not only in the circumferential direction but also in the outflow direction. This curved profile of the opening edge 16 is, for example, Figure 1 clearly visible.

[0039] The shut-off valve 3 has a dome-shaped bulge 19 with an inner area 20 that is protruding in the outflow direction. A circumferential edge 21 of the shut-off valve 3 is adapted to the contour of the opening edge 16 of the outflow opening 8, so that the shut-off valve 3 tightly closes the outflow opening 8 of the sleeve-shaped housing 2 in a shut-off position abutting the opening edge 16, as exemplified in Figure 6 As shown. To increase the sealing effect of the backflow preventer 1 in a shut-off position of the butterfly valve 3, a butterfly valve seal 22 made of an elastic sealing material is arranged along the opening edge 16.

[0040] The shape of the flap 3, and in particular the dome-shaped curvature 19 and the circumferential edge 21, which, like the opening edge 16, has a curved profile both circumferentially and in the outflow direction, is designed such that the flap 3 can be pivoted within the surrounding flow channel 14 as far away as possible from the opening edge 16 into an opening position in which it obstructs as little as possible an airflow flowing through the housing 2 in the outflow direction and provides a flow cross-sectional area available for the flowing airflow, as is the case, for example, in Figure 5The available space in the interior 15 of the housing 2 is restricted as little as possible. Furthermore, the shape of the shut-off flap 3 is adapted and specified in such a way that, when the airflow passes over the shut-off flap 3 in the outflow direction through the backflow preventer 1, it can flow past the shut-off flap 3 in the open position with minimal turbulence.

[0041] The housing 2 has two hinge pin receiving elements 23 spaced apart from each other in the hinge area 17. Each hinge pin receiving element 23 has a radially outwardly directed hinge pin receiving opening 24. Two hinge pin sections 25 are formed on the locking flap 3, by means of which the locking flap 3 can be inserted through the hinge pin receiving opening 24 into the hinge pin receiving element 23. The hinge pin sections 25 are latched and retained in the hinge pin receiving elements 23. In addition, the locking flap 3 is pivotably mounted in the hinge pin receiving elements 23 via the hinge pin sections 25.The distance between the hinge pin receiving openings 24 of the hinge pin receiving elements 23 and the inner wall 13 of the surrounding flow channel 14 is less than the diameter of the hinge pin sections 25, so that the shut-off flap 3 cannot completely detach from the hinge pin receiving elements 23 when the backflow preventer 1 is mounted in the flow channel 14. This increases the operational reliability of the backflow preventer 1.

[0042] According to the invention, the sleeve-shaped housing 2 has a circumferential indentation 26 in the region of the hinge area 17, which is arranged next to the outlet opening 8 and is not closed by the flap 3 in its closed position. When the housing 2 is inserted into the surrounding flow channel 14, the indentation 26 forms a condensate chamber 27, which is accessible from a direction opposite to the outflow direction. The indentation 26 extends axially from an outer edge of the opening 16, or from the outlet opening 8, towards the inlet opening 5 to the immediate vicinity of the sealing flange 10.Liquid condensate can accumulate in the condensate chamber 27, which runs down the inner wall 13 of the surrounding flow channel 14 in the direction of the backflow preventer 1, contrary to the outflow direction, as is often the case with a backflow preventer 1 arranged in a vertically running exhaust duct as part of an exhaust system.

[0043] According to the invention, a flow opening 28 is formed in the indentation 26 near the edge 16 of the outlet opening 8. This opening allows the condensate, which accumulates in the condensate chamber 27 bounded by the indentation 26, to flow through the condensate chamber, bypassing the shut-off valve 3, into the interior 15 of the housing 2 and subsequently out of the housing 2. To prevent the flow opening 28 from being accessible to a counter-flow of air flowing against the direction of outflow towards the blocked backflow preventer 1, and thus prevent an undesirable environment around the closed shut-off valve 3, an airtight flow opening channel 29 is formed in the condensate chamber 27. This channel extends axially from the flow opening 28, which is surrounded by the flow opening channel 29, towards the sealing flange 10 and opens into a flow opening channel opening 30 in the immediate vicinity of the sealing flange 10.As soon as a small amount of condensate accumulates in the condensate chamber 27, the condensate level rises axially from the sealing flange 10 to above the flow opening 30, thus closing the flow opening 29. With an increasing accumulation of condensate in the condensate chamber 27, the condensate level rises in both the condensate chamber 27 and the flow opening 29 until it reaches the flow opening 28. At this point, the condensate accumulating in the condensate chamber 27 can flow through the flow opening 28 into the interior 15 of the housing 2. The flow opening 29 therefore forms a siphon and blocks the flow opening 28 from any counter-flow of air approaching the non-return valve 1, contrary to the outflow direction.

[0044] In the Figures 11 to 15An exemplary and schematic representation of a different embodiment of a backflow prevention device 1, also according to the invention, is shown. The following primarily describes only features of this backflow prevention device 1 that differ from the one shown in the Figures 1 to 10 are designed as shown in the variant.

[0045] The housing 2 has an opening rim 16 of the outflow opening 8, which runs in a plane inclined at an angle of approximately 80 degrees to the outflow direction 6. If the backflow preventer 1 is arranged in a vertically oriented pipe section, the plane in which the opening rim 16 runs is then inclined at approximately 10 degrees to a horizontal plane.

[0046] The butterfly valve 3 is manufactured in one piece from an elastic plastic material, such as a suitable fluoroelastomer. In the Figures 14 and 15The shut-off valve 3 is shown in isolation, without the housing of the backflow shut-off valve 1. The shut-off valve 3 has a fixing section 31 and a pivoting flap section 32. The pivoting flap section 32 is connected to the fixing section 31 via a film hinge 33. A recess 34 is formed in the fixing section 31 to fix the fixing section 31 to the hinge area 17 at the opening edge 16 by means of a clamping lug 35 projecting through this recess 34. The hinge area 17 has a flat contact surface 36, which is oriented at an angle to the plane in which the opening edge 16 runs. By fixing the fixing section 31 of the shut-off valve 3 to the contact surface 36 of the hinge area 17, the pivoting flap section 32 of the pivoting valve 3, which rests against the opening edge 16, is elastically deformed.The resulting restoring force presses the pivot flap section 32 against the opening edge 16 and closes the outflow opening 8.

[0047] The housing 2 further comprises a support rib 37 extending transversely across the outlet opening 8 and between opposing edge regions of the opening rim 16. When the pivot flap section 32 is in contact with the opening rim 16, the shut-off flap 3 rests on the support rib 37 in a strip area running approximately centrally. The support rib 37 prevents undesired deformation of the elastically deformable pivot flap section 32 in the event of a counterflow directed into the housing 2 against the outflow direction 6, and ensures or supports a reliable closure of the outlet opening 8.

Claims

1. Non-return device (1) for a flow channel (14) through which an airflow flows, comprising a housing (2), through which the airflow can flow in an outflow direction, with an outflow opening (8) which can be closed by a check valve (3) that is pivotably mounted on the housing (2), wherein the housing (2) is configured to be sleeve-shaped and comprises an inflow opening (5) opposite the outflow opening (8), wherein the housing (2) can be arranged with a sealing flange (10), extending in a peripheral direction around an outside wall (9) of the housing (2), in a hollow-cylindrical flow channel (14), such that an airflow flowing through the flow channel (14) in the outflow direction (6) flows into the housing (2) through the inflow opening (5) and flows out of the housing (2) through the outflow opening (8), wherein the check valve (3) rests on the outflow opening (8) in a closing manner on an opening edge (16) in a blocking position and prevents an undesired return flow, counter to the outflow direction (6), into the outflow opening (8), wherein the check valve (3) is pivoted away from the opening edge (16) in an opening position and releases the outflow opening (8) for an airflow flowing through the housing (2) in the outflow direction (6), and wherein the opening edge (16) of the outflow opening (8) comprises a hinge region (17) in which the check valve (3) is mounted pivotably on the housing (2), which transitions into a check valve stop region (18) arranged opposite in the peripheral direction, which region is configured to be offset in the outflow direction (6), characterised in that the housing (2) comprises a recess (26) in the peripheral direction, which is arranged beside the outflow opening (8) and is not closed by the check valve (3), such that the recess (26) forms (27) a condensate chamber when a housing (2) is inserted into the surrounding flow channel (14), which chamber is accessible from a direction opposite to the outflow direction (6), and in that a through-flow opening (28) is arranged in the recess (26) in the vicinity of the opening edge (16) of the outflow opening (8), through which through-flow opening a condensate, which collects in the condensate chamber (27) delimited by the recess (26), can flow into an interior of the housing (2), bypassing the check valve (3).

2. Non-return device (1) according to claim 1, characterised in that the check valve (3) is produced from a resilient plastics material and is configured and is arranged on the housing (2) in such a way that the outflow opening (8) is closed with the resiliently preloaded check valve (3) without an airflow flowing through.

3. Non-return device (1) according to claim 2, characterised in that the check valve (3) comprises a fixing portion (31) for fixing the check valve on or at the hinge region (17) of the opening edge (16), and a pivot valve portion (32) which is connected to the fixing portion (31) via a film hinge (33).

4. Non-return device (1) according to claim 2 or claim 3, characterised in that a support rib (37) is arranged in front of the check valve (3) in the outflow direction (6), on which rib the non-pivoted check valve (3) rests, and which extends transversely over the outflow opening (8) and thereby prevents an undesired pivoting or deformation of the resilient check valve (3) counter to the outflow direction (6) in the case of a return flow directed counter to the outflow opening (8).

5. Non-return device (1) according to any of the preceding claims, characterised in that the check valve (3) has a dome-shaped curvature (19) having an inner region (20) that is bulged in the outflow direction (6).

6. Non-return device (1) according to any of the preceding claims, characterised in that the opening edge (16) has a course that is curved not only in the peripheral direction but rather also in the outflow direction (6).

7. Non-return device (1) according to any of the preceding claims, characterised in that the check valve (3) is pivotably mounted on the housing (2) via a hinge, wherein the hinge is arranged so as to be offset towards the inside, in the radial direction, from an outer peripheral edge (11) of the sealing flange (10).

8. Non-return device (1) according to claim 1 and claim 7, characterised in that the hinge comprises at least one on a hinge bolt receiving opening (23) having a radially outwardly directed hinge bolt receiving opening (24), through which a hinge bolt (25) can be inserted and in which the hinge bolt receiving element (23) can be pivotably mounted, wherein the hinge bolt receiving opening (24) is arranged, in the radial direction, closer than a diameter of the hinge bolt (25) to the outer peripheral edge (11) of the sealing flange (10).

9. Non-return device (1) according to any of the preceding claims, characterised in that the recess (26) is arranged in the hinge region (17), in the peripheral direction, and extends in an axial direction from an outer side of the opening edge (16) of the outflow opening (8) in the direction of the inflow opening (5).

10. Non-return device (1) according to any of the preceding claims, characterised in that an airtight through-flow opening channel (29) extends in the condensate chamber (27) from the through-flow opening (28) in the direction of the sealing flange (10), and a through-flow opening channel mouth (30) is arranged in the condensate chamber (27) at a spacing from the through-flow opening (28).

11. Non-return device (1) according to any of the preceding claims, characterised in that a curvature (19) of the check valve (3) is adjusted to an outer peripheral edge (11) of the sealing flange (10) in such a way that the check valve (3) is pivotable as far as possible away from the opening edge (16), in the opening position, without protruding in the radial direction at the outer peripheral edge (11).

12. Non-return device (1) according to any of the preceding claims, characterised I that an outwardly protruding stop limitation element is formed on an outer side of the check valve (3) directed away from the housing (2), which stop limitation element limits a pivot movement of the check valve (3) into the opening position, by a stop on an inside wall (13) of the surrounding flow channel (14).