EP1649112A1

EP1649112A1 - Backflow preventer

Info

Publication number: EP1649112A1
Application number: EP04763543A
Authority: EP
Inventors: Wolfgang Müller
Original assignee: Alfred Kaercher SE and Co KG
Current assignee: Alfred Kaercher SE and Co KG
Priority date: 2003-07-28
Filing date: 2004-07-28
Publication date: 2006-04-26
Also published as: US20060157111A1; WO2005012656A1; DE10335380B3; CN1829846A

Abstract

Disclosed is a backflow preventer comprising a housing which is provided with an inlet port, an outlet port, and at least one leakage opening that is located between said ports. The housing accommodates two first check valves which are arranged one behind the other. The first check valve is movably retained for opening or blocking a flow connection between an intermediate space of the housing and the leakage opening. In order to prevent, in a simple structural manner, the pressure from unduly increasing in the area of the outlet port, the housing encompasses an inner housing and an outer housing. The outer housing is provided with the at least one leakage opening while the inner housing accommodates the two check valves and is retained within the outer housing so as to be movable in the direction of flow. Furthermore, the inner housing comprises an outlet port via which the flow connection between the intermediate space and the leakage opening can be established regardless of the position of the inner housing by displacing the first check valve.

Description

backflow preventer

The invention relates to a backflow preventer, in particular for connecting a high-pressure cleaning device to a drinking water supply line, with a housing which has an inlet opening, an outlet opening and at least one leakage opening arranged in the flow direction between the inlet and outlet openings and which receives a first and a second non-return element , which are arranged one behind the other in the flow direction, the first check valve being held displaceably for releasing or shutting off a flow connection between an intermediate space of the housing arranged between the two check valves and the leakage opening.

Such check valves are also known as "pipe interrupters" and are known from published patent application DE 24 24 978 AI. They are used in cleaning devices, especially high-pressure cleaning devices or washing machines. If such cleaning devices are connected to a drinking water supply line, it must be ensured that contaminated cleaning liquid cannot get back from the cleaning device into the drinking water supply line. For this purpose, a backflow preventer of the type mentioned above is connected between the drinking water supply line and the cleaning device. This has check valves to prevent the return of the dirty cleaning liquid into the drinking water supply line. In this case, two check valves connected in series with identical closing direction are usually used, so that it is ensured that even if one of the two check valves fails, the other check valve can easily take over the protection alone. An intermediate space between the two check valves is usually in flow communication with a leakage opening, through which the intermediate space of the housing can be emptied if the differential pressure (pr-p between the pressure (pi) in the area of the inlet opening and the pressure in the intermediate space (pi For example, it can be provided that the space in the housing between the two check valves can be emptied automatically as soon as the differential pressure between the pressure (pi) in the area of the inlet opening and the pressure in the area of the space ( p falls below the value of 14 kPa (Pι-p, <14 kPa).

In order to be able to empty the space mentioned, if necessary, the first check valve is arranged to be displaceable. Depending on the position of the first check valve, a flow connection between the intermediate space and the leakage opening can be released or blocked. Backflow preventers of this type have proven themselves in practice to the extent that a backflow of contaminated cleaning fluid can be reliably prevented by the check valves assuming their closed position. In this position, however, an increase in pressure in the area of the outlet opening of the non-return valve can damage the same or the cleaning device connected to it. Such pressure increases can, for example, occur briefly in the form of pressure peaks in high-pressure cleaning devices when the high-pressure cleaning devices are switched off. The pressure peaks can be caused by small amounts of water, which when the high-pressure cleaning devices are switched off Pressure get into their suction chamber and cannot escape because of the backflow preventer used.

The object of the present invention is to develop a backflow preventer of the type mentioned at the outset in such a way that an impermissible pressure increase in the region of the outlet opening can be avoided in a structurally simple manner.

This object is achieved according to the invention in a backflow preventer of the generic type in that the housing comprises an inner housing and an outer housing, the outer housing having at least one leakage opening and the inner housing receiving the two check valves and being held in the outer housing so that it can be pushed back and forth in the flow direction, and wherein the inner housing has a passage opening, via which the flow connection between the intermediate space and the leakage opening can be established independently of the position of the inner housing by moving the first check valve relative to the second check valve.

The idea flows into the invention that an impermissible pressure increase in the area of the outlet opening can be avoided in a structurally simple manner in that the housing is designed in two parts with an outer housing and an inner housing slidably held therein, the inner housing accommodating the two check valves , In such a configuration of the backflow preventer, an impermissible pressure increase in the area of the outlet opening of the housing leads to the fact that the inner housing with the two non-return valves is displaced in the direction opposite the flow direction within the outer housing. will. An impermissible pressure increase in the area of the outlet opening can thus be counteracted by moving the inner housing in the direction opposite to the direction of flow.

In spite of the displaceable mounting of the inner check valve accommodating the two check valves, it is ensured according to the invention that by moving the first check valve relative to the second check valve, the space arranged between the two check valves can be emptied via the passage opening of the inner casing and the leakage opening of the outer casing. This ensures regardless of the position of the inner housing that, for example, in the event of a leak in the second non-return valve and an associated inadmissible pressure increase in the area of the space, the space can be reliably emptied and thus a backflow into the area of the inlet opening and any associated with it Drinking water supply line is reliably prevented.

The backflow preventer according to the invention thus has, in addition to its function of preventing a backflow from a connected cleaning device into the drinking water supply line, also the function of a pressure relief without the need for expensive separate components. The volume of the check valve can be kept relatively small, and the check valve can be manufactured inexpensively.

A displacement movement of the inner housing is controlled in the embodiment according to the invention by the difference between the pressures prevailing in the area of the inlet opening and the outlet opening. Additional spring elements for Positioning of the inner housing within the outer housing can be omitted. If the backflow preventer according to the invention is used when connecting a high-pressure cleaning device to a drinking water supply line, an increase in pressure which forms within the outlet opening when the high-pressure cleaning device is switched off can be prevented by the inner housing carrying out a pressure compensation movement counter to the flow direction of the backflow preventer.

The outer housing and the inner housing preferably define between them a sealed leakage space, via which the passage opening of the inner housing is in flow connection with the leakage opening of the outlet housing. The leakage space can be ensured in a structurally particularly simple manner that, regardless of the position of the inner housing relative to the outer housing, the space between the two check valves can be emptied in the event of an impermissible pressure increase in the space. For this purpose, the leakage space provides a flow connection from the passage opening of the inner housing to the leakage opening of the outer housing.

It is particularly favorable if the leakage space surrounds the inner housing in a ring. For example, it can be provided that the leakage space is defined by a circumferential groove of the inner housing, the passage opening opening into the circumferential groove and the latter being sealed off by a region of the outer housing which surrounds the leakage opening.

In the case of a particularly simple design, the leakage space is sealed by means of sealing rings. For example, it can be provided that the inner housing is surrounded by two sealing rings, which are Flow direction are arranged at a distance from each other and limit the leakage space in the flow direction.

It is expedient if the outer housing has a receptacle, on the inner wall of which the inner housing is slidably held by means of sealing rings. The inner housing can, for example, be designed like a piston and slidably arranged in a cylindrical outer housing and accommodate the two check valves.

In a particularly preferred embodiment of the non-return valve according to the invention, the inner housing has a sleeve surrounding the two non-return valves, which is surrounded in the circumferential direction by two sealing rings arranged at an axial distance from one another. The sleeve can be designed as a hollow cylinder and can be connected in one piece to a base and a cover, each of which comprises a through hole through which a liquid, preferably water, can flow when the non-return valve is used.

It is advantageous if the first check valve comprises a closing spring and is supported on the second check valve by means of the closing spring. The closing spring assumes a dual function here, because on the one hand it can be used to apply a restoring force in the direction of an assigned valve seat of the first check valve to a closing body of the first check valve. To open the first check valve, it is therefore necessary to apply an opening force which counteracts the spring force of the closing spring to the closing body. On the other hand, the closing spring supported on the second check valve acts on the closing body and the associated valve seat of the first Check valve also its valve housing. Thus, by means of the closing spring, a restoring force opposite to the direction of flow can be exerted on the first check valve such that the first check valve is biased by the closing spring and, contrary to the action of the closing spring, starting from a position that releases the flow connection between the space between the housing and the leakage opening into a position said flow connection blocking position is displaceable. An additional return spring for the first check valve can be omitted.

In an advantageous embodiment, the first check valve has a valve housing with a valve seat, the valve housing being held displaceably in a valve holder arranged inside the inner housing. The valve holder can simplify the assembly of the backflow preventer according to the invention. Here, the valve holder and the valve housing of the first check valve can have a relatively high dimensional accuracy in order to ensure the displaceability of the valve housing of the first check valve relative to the second check valve. The valve holder can be inserted into the inner housing. It is advantageous here if at least one sealing element is arranged between the valve holder and the inner housing.

In a particularly preferred embodiment, the valve holder forms a guide for the valve housing of the first check valve. For example, it can be provided that the valve holder has a through hole in which the valve housing of the first check valve is slidably held. The through bore is preferably designed in a stepped manner with one between a first bore section and a second one Bore section arranged step, which forms a stop surface for the valve housing of the first check valve and thus specifies a clear end position for the displaceable valve housing of the first check valve.

The valve holder can preferably be releasably connected to the second check valve, for example to its valve housing. As a result, the assembly of the backflow preventer according to the invention can be further simplified.

In order to increase the mechanical strength of the check valve, it is advantageous if the first check valve has a closing body which is guided in a guide held on the second check valve. For example, it can be provided that the closing body is guided via a guide pin in a guide bush, which is preferably held on the valve body of the second check valve. It is particularly advantageous here if the guide bush is integrally connected to the valve body of the second check valve.

It is expedient if the valve holder comprises at least one flow channel via which the intermediate space arranged between the two check valves is in flow connection with the through opening of the inner housing, the flow channel being coverable by the valve housing of the first check valve. The flow channel can be designed, for example, in the form of a radial bore, via which the intermediate space arranged between the two check valves is in flow connection with the through opening of the inner housing. If the flow connection is to be disconnected, it is only necessary to by moving the first check valve into a position covering the flow channel.

In a particularly preferred embodiment of the non-return valve according to the invention it is provided that the valve housing of the first check valve for sealing off the flow connection between the intermediate space and the leakage opening can be sealingly applied to a sealing surface of the second check valve. It is advantageous here if a sealing ring is arranged between the valve housing of the first check valve and the associated sealing surface of the second check valve. The latter can be inserted, for example, into an annular groove surrounding the valve housing of the first check valve.

The following description of a preferred embodiment of the invention serves in conjunction with the drawing for a more detailed explanation. Show it:

Figure 1 is a longitudinal sectional view of a backflow preventer according to the invention with an outer housing and an inner housing, the inner housing assuming a first end position and

Figure 2 is a longitudinal sectional view corresponding to Figure 1, wherein the inner housing assumes a second end position.

In the drawing, a backflow preventer, generally designated by reference numeral 10, is shown, which has a two-part housing 12 with a hollow cylindrical outer housing 14 and an inner housing 16 held displaceably within the outer housing 14. The outer housing 14 has a housing jacket 18 which is connected to a housing cover 19 and a housing base 20. An inlet opening 22 is formed in the housing cover 19 and the housing base 20 has an outlet opening 23. At least one, preferably several, leakage openings 27 distributed over the circumference of the housing casing 20 are introduced into the outer casing 14 in the flow direction 25 approximately centrally between the inlet opening 22 and the outlet opening 23.

The outer housing 14 surrounds a receptacle 29 in which the inner housing 16 is held so that it can be pushed back and forth in the flow direction 25.

The inner housing 16 is also designed as a hollow cylinder and comprises a sleeve 33 which is arranged at a distance from an inner wall 31 of the housing shell 18 and which is connected at the end to an inner housing cover 34 or an inner housing base 35, each of which is coaxial with the inlet opening 22 and the outlet opening 23 have arranged through bore 36 and 37 respectively.

In relation to the direction of flow 25, the sleeve 33 is surrounded at the level of the inner housing cover 34 and at the level of the inner housing base 35 by a radially projecting collar 38 and 39, which projects in the radial direction beyond an outer wall 40 of the sleeve 33 and an annular groove 41 has, in which a sealing ring 42 or 43 is inserted sealingly against the inner wall 31 of the housing shell 18 of the outer housing 14. A double seal between the area of the inlet opening 22 and the area of the outlet opening 23 is ensured by means of the two sealing rings 42, 43. The inner wall 31 of the outer housing 14 and the outer wall 40 of the inner housing 16 define a leakage space 45 between them, which extends in the flow direction 25 between the collar 38 and the collar 39 and is sealed by means of the sealing rings 42 and 43.

The inner housing 16 accommodates a first check valve 47 and a second check valve 49 which adjoins this in the flow direction 25, the closing direction of which in each case is opposite to the flow direction 25 and which define an intermediate space 51 of the housing 12 between them.

The first check valve 47 has an approximately cup-shaped valve housing 53 with a valve housing base 54, to which a valve housing jacket 55 is integrally connected in the flow direction 25 and which carries a guide collar 56 on its side facing away from the valve housing jacket 55.

In the area of the valve housing base 54, the first check valve 57 has a conical sealing surface 57, against which a closing body of the first check valve 47 in the form of a valve piston 59 can be sealingly applied, which carries on its side facing away from the sealing surface 57 a guide pin 61 surrounded by a closing spring 60 ,

The valve housing 53 of the first check valve 47 is slidably held in a stepped, continuous axial bore 63 of a valve holder 65. The valve holder 65 lies flat on a portion of the Inside of the sleeve 63 and on the inner housing cover 64, a sealing ring 66 being arranged between the valve holder 65 and the sleeve 63.

The axial bore 63 has a first bore section 68, which is aligned coaxially to the through bore 36 of the inner housing cover 34 and merges via a radial step 69 into a second bore section 70, to which a connecting sleeve 71 with an internal thread 72 connects in one piece in the flow direction 25. In the transition region between the second bore section 70 and the connecting sleeve 71, at least one, preferably a plurality, flow channels 73, which are advantageously spaced apart from one another in the circumferential direction, are formed in the valve holder 65 and open into aligned passage openings 75, which open the sleeve 33 of the inner housing 16 succeed.

The second bore section 70 of the axial bore 63 receives the valve housing 53 of the first check valve with the exception of its guide collar 56, which is immersed in the first bore section 68 which forms a guide for the valve housing 53.

The valve holder 65 is screwed by means of the connecting sleeve 71 to a valve housing 77 of the second check valve 49, which surrounds a central flow channel 78 and comprises a conical valve seat 80 to which a closing body in the form of a conical valve piston 82 can be sealingly applied, which is closed by means of a closing spring 83 is resiliently biased towards the valve seat 80. On its side facing away from the valve seat 80, the valve piston 82 is connected to a guide pin 84, the free end of which is guided in a guide sleeve 85 which is immovable in the central flow channel 68 by means of a plurality of radially aligned support arms 86. hold, with the support arms 86 forming an abutment for the closing spring 83.

On its face 88 facing the first check valve 47, the valve housing 77 of the second check valve 49 has a sealing surface 90 that tapers conically in the direction of flow 25, against which a free end area 92 of the valve housing jacket 55 of the first check valve 47 can be sealingly fitted with an O-ring 93.

Four webs 95 are integrally formed on the end face 88 of the valve housing 77 in the circumferential direction at a uniform distance from one another and are integrally connected to a guide sleeve 96 aligned coaxially to the sealing surface 57 of the first check valve 47. The guide sleeve 96 receives the free end portion of the guide pin 61 of the first check valve 47, and the closing spring 60 of the first check valve 47 is clamped between the valve piston 59 and the webs 95, so that the first check valve 47 by means of the closing spring 60 on the valve housing 77 of second check valve 49 supports.

The housing 12 of the backflow preventer 10 can be connected, for example, to the suction port of a high-pressure cleaning device. Here, the outer housing 14 can be connected in one piece to a suction nozzle of the high-pressure cleaning device. In the area of the inlet opening 22, the outer housing 14 can be connected to a drinking water supply line, for example, via a screw connection, not shown in the drawing. When connected, the water pressure prevailing in the drinking water supply line can act in the area of the inlet opening 22. As a result, the entire inner housing 16 with the two rear Impact valves 47 and 49 are moved forward in the flow direction 25 until the inner housing 14 bears against a corresponding inner shoulder 98 of the inner housing 16 in the region of the front collar 39 in the flow direction 25. The resultant water pressure has the result that the first check valve 47 is displaced so far forward in the flow direction 25 against the elastic restoring force of the closing spring 60 that the free end region 92 of the valve housing 53 lies sealingly against the sealing surface 90 of the valve housing 77 of the second check valve 49 and consequently, the flow connection between the intermediate space 51 and the flow channel 73 and via this through the passage opening 75 to the leakage space 45 and to the leakage openings 27 is blocked. This is shown in Figure 1.

If the high-pressure cleaning device is started, a negative pressure is established in the area of the outlet opening 23 and both the first check valve 47 and the second check valve 49 open in the usual way. As a result, the backflow preventer 10 can be flowed through by the water.

If the high-pressure cleaning device is switched off, the two check valves 47 and 49 automatically assume their closed position due to the closing forces of the closing springs 60 and 83. When the high-pressure cleaning device is switched off, a pressure increase can form in the region of the outlet opening 23, which has the consequence that the entire inner housing 16 is shifted backwards in the direction opposite to the flow direction 25 while maintaining the relative position of the check valves 47 and 49 until the rear collar 38 of the inner housing 16 abuts a corresponding inner shoulder 100 of the inner housing 16. The inner housing 16 can thus perform an evasive movement counter to the flow Execute direction 25, whereby a pressure increase forming in the region of the outlet opening 23 is reduced. This is shown in Figure 2.

Regardless of the position of the inner housing 16 relative to the outer housing 14, the valve housing 43 of the first check valve 47 can stand out against the flow direction 25 from the sealing surface 90 of the valve housing 77 of the second check valve 49 if the differential pressure (Pi-p,) between that in the area the pressure prevailing in the inlet opening 22 (pi) and the pressure (pi) prevailing in the region of the intermediate space 51 falls below a predetermined value, for example by 14 kPa. Such a pressure can develop in the intermediate space 51, for example, when the second check valve 49 leaks, so that any overpressure which may exist in the area of the outlet opening 23 acts into the intermediate space 51. This would have the consequence that the first check valve 47 releases the flow connection between the intermediate space 51 and the leakage openings 27, so that the intermediate space 51 can be emptied via the flow channel 73, the passage opening 75, the leakage space 45 and the leakage openings 27.

The displaceable mounting of the inner housing 16 with the two check valves 47 and 49 in the receptacle 29 of the outer housing 14 ensures that, for example, when a high-pressure cleaning device connected to the non-return valve 10 is switched off, pressure peaks which form can be reliably intercepted, but at the same time it is ensured that a Sucking back or pushing back liquid into the drinking water supply network is reliably prevented even if the second check valve 49 fails.

Claims

GODFATHER CLAIMS

1. Backflow preventer, in particular for the connection of a high-pressure cleaning device to a drinking water supply line, with a housing which has an inlet opening, an outlet opening and at least one leakage opening arranged in the flow direction between the inlet and outlet openings and which accommodates a first and a second non-return element which are arranged one behind the other in the direction of flow, the first check valve being held displaceably for releasing or separating a flow connection between an intermediate space of the housing arranged between the two check valves and the leakage opening, characterized in that the housing (12) is an inner housing (16) and a Outer housing (14), wherein the outer housing (14) has at least one leakage opening (27) and wherein the inner housing (16) receives the two check valves (47, 49) and in the outer housing (14) in flow Ömungsrichtung (25) is pushed back and forth, and wherein the inner housing (16) has a passage opening (75) through which regardless of the position of the inner housing (16) by moving the first check valve (47) relative to the second check valve (49 ) the flow connection between the intermediate space (51) and the leakage opening (27) can be established.

2. Backflow preventer according to claim 1, characterized in that the outer housing (14) and the inner housing (16) define between them a sealed leakage space (45) through which the passage opening (75) with the leakage opening (27) is in flow connection.

3. Backflow preventer according to claim 2, characterized in that the leakage space (45) surrounds the inner housing (16) in a ring.

4. backflow preventer according to claim 2 or 3, characterized in that the leakage space (45) by means of sealing rings (42, 43) is sealed.

5. Backflow preventer according to one of the preceding claims, characterized in that the outer housing (14) has a receptacle (29), on the inner wall (31) of which the inner housing (16) is slidably held by means of sealing rings (42, 43).

6. Backflow preventer according to one of the preceding claims, characterized in that the inner housing (16) has a sleeve (18) surrounding the two check valves (47, 49), which in the circumferential direction of two sealing rings arranged at an axial distance from one another (42, 43) is surrounded.

7. Backflow preventer according to one of the preceding claims, characterized in that the first check valve (47) comprises a closing spring (60) and is supported by means of the closing spring (60) on the second check valve (49).

8. Backflow preventer according to one of the preceding claims, characterized in that the first check valve (47) has a valve housing (53) with a valve seat (57), the valve housing (53) in a valve holder (65) arranged inside the inner housing (16) ) is held displaceably. 17

8. Backflow preventer according to one of the preceding claims, characterized in that the first check valve (47) has a valve housing (53) with a valve seat (57), the valve housing (53) in a valve holder (65) arranged inside the inner housing (16) ) is held displaceably. 18 -

9. Backflow preventer according to claim 8, characterized in that the valve holder (65) forms a guide for the valve housing (53) of the first check valve (47).

10. Backflow preventer according to claim 8 or 9, characterized in that the valve holder (65) with the second check valve (49) is releasably connectable.

11. Backflow preventer according to claim 8, 9 or 10, characterized in that the first check valve (47) has a closing body (59) which is guided in a guide (96) held on the second check valve (49).

12. Backflow preventer according to one of claims 8 to 11, characterized in that the valve holder (65) comprises at least one flow channel (73) via which the intermediate space (29) is in flow connection with the through opening (75) of the inner housing (16), wherein the flow channel (73) can be covered by the valve housing (53) of the first check valve (47).

13. Backflow preventer according to one of the preceding claims, characterized in that the valve housing (53) of the first check valve (47) for shutting off the flow connection between the intermediate space (51) and the leakage opening (27) sealingly against a sealing surface (90) of the second check valve (49) can be created.