AU2004219971A1

AU2004219971A1 - Device for preventing backflow

Info

Publication number: AU2004219971A1
Application number: AU2004219971A
Authority: AU
Inventors: Robert Nathan
Original assignee: Alfred Kaercher SE and Co KG
Current assignee: Alfred Kaercher SE and Co KG
Priority date: 2003-03-14
Filing date: 2004-03-05
Publication date: 2004-09-23
Anticipated expiration: 2024-03-05
Also published as: CN100547179C; ES2271859T3; EP1604071B1; CN1761792A; AU2004219971B2; EP1604071A1; WO2004081301A1; ATE337443T1; DE10311252B3; DK1604071T3

Abstract

The invention relates to a device for preventing backflow (1), comprising a housing (2) provided with an inlet and an outlet forming a flow path leading from the inlet to the outlet; two return valves (9, 10, 23, 30) which open out into the direction of flow and which are arranged behind each other; a discharge channel (16) which discharges from the intermediate area between the two return valves; a valve body (17) which seals the discharge channel (16) inside the housing and which is sealingly displaceable in relation thereto inside the housing, said valve body being displaced by the effect of a spring in order to occupy an open position in which the discharge channel is released and occupying a closed position when the housing is cross-flown counter to the effect of the spring, receiving therein the return valve, which is arranged downstream. The aim of the invention is to improve the seal between the valve body and the housing. This is achieved by provided a membrane seal (18) which seals the valve body in relation to the housing. The outer edge area of said seal is fixed on the inner wall of the housing such that it is tight and the inner edge area is fixed inside a sealing edge (19) of the valve body making the latter tight. The membrane seal extends above the sealing edge and the valve body, when in a closed position, rests against a sealing seat (21) of the housing with the sealing edge and an intermediate layer of the membrane seal.

Description

VERIFIED CERTIFICATE OF TRANSLATION The undersigned, whose residence and office address is set forth below, states that she is familiar with the English and German languages and that the English-language translation of International Patent Application PCT/EP2004/002234 (International Publication No. WO 2004/081301) is to the best of her knowledge and belief, accurate and fairly reflects the contents and meaning of the said German-language document. Executed on August 24, 2005. Signature Typed Name G' . cLauchlan Residence/ Office Address Johan -Proeschel-Strasse 10 97509 Zeilitzheim Federal Republic of Germany DEVICE FOR PREVENTING BACKFLOW The invention relates to a device for preventing backflow with a housing which has an inlet and an outlet and forms a flow path leading from the inlet to the outlet, two return valves in the flow path which open in the direction of flow and are connected one behind the other, a discharge channel exiting from the intermediate space between the two return valves, a valve member which closes the discharge channel, can be displaced in the housing in a sealed manner in relation to it and is moved into an open position releasing the discharge channel due to the action of a spring and into a closed position contrary to the action of the spring when the housing has liquid flowing through it and which accommodates in it the return valve arranged upstream. Devices for preventing backflow of this type are known, for example, from DE 198 54 951 Al, DE 21 57 363 Al, DE 24 24 978 Al or EP 1 022 398 Al. In the case of these known constructions, a larger number of ring seals must be used in order to seal the valve member in relation to the housing and in order to bring about sealing in relation to the corresponding valve seat in the closed position of the valve member. The object of the invention is to simplify the construction of a generic device for preventing backflow, in particular, in the sealing area.

-2 This object is accomplished in accordance with the invention, in a device for preventing backflow of the type described at the outset, in that a membrane seal is provided for sealing the valve member in relation to the housing, the outer edge area of this membrane seal being secured to the inner wall of the housing in a sealed manner and its inner edge area being secured within a sealing edge of the valve member so as to be sealed against it in such a manner that the membrane seal extends over the sealing edge and the valve member, in its closed position, abuts on a sealing seat of the housing with the sealing edge with the membrane seal interposed between them. Known ring seals are, therefore, replaced by a membrane seal which has a double function. Namely, this membrane seal seals, on the one hand, the valve member in relation to the housing and, on the other hand, it acts as a seal in the valve area since it seals the valve member in relation to the sealing seat when the valve member is moved into the closed position. This second function is achieved in that the membrane covers the sealing edge of the valve member and, therefore, is always located between this sealing edge and the sealing seat in the closed position. It is favorable when the outer edge area of the membrane seal is clamped between two parts of the housing which are connected to one another. In addition, it may be provided for the inner edge area of the membrane seal to be clamped between two parts of the valve member which are connected to one another. In a particularly preferred embodiment it is provided for the discharge channel to be arranged it the sealing area, in which the sealing edge presses the membrane seal against the sealing seat of the housing. As a result, the -3 membrane seal is placed over the sealing channel and pressed against it; this results in a particularly reliable sealing of the discharge channel. It may, in addition, be provided for the membrane seal to have a greater material thickness in the sealing area between sealing edge and sealing seat of the housing than in the remaining areas. A membrane seal is, therefore, used which is particularly thick just in that area, in which the membrane seal comes to rest between sealing edge and sealing seat and, therefore, guarantees an optimum sealing effect, in particular, when production tolerances occur, as well. In principle, the construction described can be used for devices for preventing backflow of different designs. An arrangement is, however, particularly advantageous, with which the device for preventing backflow can be used not only in combination with supply lines under pressure but also in conjunction with pressure-less supply systems, for example, during suction operation from a lake or a store tank. In order to make this possible, it may be provided in accordance with the invention in a particularly preferred embodiment for the device for preventing backflow to have a blocking device which secures both return valves in an open position and the valve member in a closed position. If the device for preventing backflow is equipped with such a blocking device, the device for preventing backflow is then switched to through flow and the discharge channel is closed so that the device for preventing backflow allows liquid entering it to flow through without loss but displays no return action.

-4 If the blocking device is activated, a user device with such a device for preventing backflow is thus equipped for suction operation; if the blocking device is deactivated, on the other hand, a conventional device for preventing backflow with a double return action is obtained. In principle, it is possible for the blocking device to have separate means for opening each of the return valves and keeping them in the open position and, in addition, for moving the valve member into the closed position and keeping it there. It is, however, particularly advantageous when in accordance with a preferred embodiment the return valve in the valve member moves the other return valve into an open position via an actuating element during its displacement into the open position and with the valve member moved into a closed position. It is then sufficient to move the one return valve into an open position and keep it in this position, and a permanent displacement into an open position is obtained at the same time in the case of the second return valve. For example, this may be realized in that the closing members of the two return valves can be displaced axially parallel to one another, in particular, coaxially to one another and that the actuating element is an extension which provides a force-locking connection between the closing members as soon as the valve member is in a closed position and the closing member in the return valve of the valve member is moved into an open position whereas such a force-locking connection is not provided irrespective of the position of the closing member in the valve member when the valve member is in an open position.

- 5 The dimensions may also be selected such that even when the valve member is in a closed position the force-locking connection between the closing members is not generated until the closing member in the valve member is not only lifted away from its valve seat but is also removed a certain distance from the valve seat. As a result, it may be ensured that during normal pressure operation the return valve located downstream can also reach the closed position when the valve member is in a closed position and the return valve arranged therein in an open position. In other words, with this configuration the closing member in the valve member is displaced over a distance which is greater than its normal opening movement in order to move, in addition, the closing member of the return valve located downstream into an open position. The extension can be a push rod which is preferably part of the closing member in the valve member. In a preferred embodiment, it is provided for the actuating device to have a push element which can abut on the closing member of the return valve in the valve member in the direction of displacement and can be moved in the direction of displacement of the closing valve. In this respect, this may be a push rod which is guided in a sealed manner through the wall of the housing. In a particularly preferred embodiment, the push element can be inserted into the housing through the supply. In particular, the push element can be a piece of pipe. This piece of pipe is, in a preferred embodiment, a short connection pipe to the supply which communicates with a supply line. Therefore, when this -6 special piece of pipe is inserted into the supply, it automatically moves the valve member into a closed position and the closing members of the return valves into an open position. The supply line can be a special suction line and bear at its end located opposite the short connection pipe a suction head, as a result of which any connection to a supply system under pressure is precluded. As a result, it can be ensured that such a supply line with a short connection pipe switching the device for preventing backflow to inactive is not inadvertently connected to a supply system which is under pressure and for which the device for preventing backflow must be active. When normal short connection pipes are used, such as those customarily used for the connection to a supply system, no displacement of valve member and closing members of the return valves takes place and so when normal connection pieces are used the device for preventing backflow remains active in the normal way. A bridging of the return valves and, therefore, the setting of the device for preventing backflow for suction operation is brought about only when a special short connection pipe is used which is connected to a suction line and which cannot be connected to a pressure supply system. The closing member in the valve member may have a stop which limits its opening movement in relation to the valve member so that during the advancing of the push element over a distance which is greater than the normal opening stroke of the closing member in the valve member the closing member moves the valve member into its closed position. In a different embodiment it is provided for the push element to abut first of all on the closing member of the return valve arranged in the valve member - 7 and also on the valve member only after its displacement into an open position so that the valve member is likewise moved directly by the push element and not indirectly via the closing member as in the configuration described above. For example, the closing member can bear a projection which protrudes beyond the valve member and on which the push element comes to rest so that the closing member is moved first of all and the valve member only thereafter. The following description of preferred embodiments of the invention serves to explain the invention in greater detail in conjunction with the drawings. These show: Figure 1: a longitudinal sectional view of a device for preventing backflow with two return valves in a rest position; Figure 2: a view of the device for preventing backflow of Figure 1 during connection to a conventional pressure supply system prior to the opening of the return valves and Figure 3: a view of the device for preventing backflow of Figures 1 and 2 with a short connection pipe inserted for the permanent opening of the return valves and for the permanent closing of the discharge channel. The device 1 for preventing backflow illustrated in the drawings is connected to the supply inlet of a user device, for example, a high pressure cleaning device or another apparatus, to which liquid is supplied from a supply line.

-8 The device for preventing backflow illustrated in the drawings has a housing 2 which consists of two housing parts 3, 4. The first housing part includes an inflow branch stub 5 which opens in a bell shape into a cylindrical valve chamber 6 which is open at its end located opposite the inflow branch stub 5 and is closed at this end by a second dome shaped housing part 4. An outflow branch stub 7 is connected in one piece to the dome-shaped housing part 4 and, in the embodiment illustrated, is bent at right angles but could, in principle, also be designed in a straight line. The dome-shaped housing part 4 has a central opening 8 which widens conically towards the outflow branch stub and, as a result, forms a valve seat 9 for a closing member 10 which is mounted in a guide 11 of the outflow branch stub 7 so as to be displaceable in longitudinal direction of the housing part 3 and is moved by means of a pressure spring 13 surrounding a shaft 12 of the closing member 10 into a closed position, in which the closing member 10 abuts on the valve seat 9 by means of a ring seal 15 placed in a circumferential groove 14 and closes the opening 8. The closing member 10 can be lifted away from the valve seat 9 contrary to the action of the pressure spring 13 and, as a result, release the opening 8. The closing member 10 forms together with the valve seat 9 a return valve which opens contrary to the direction of through flow of the device 1 for preventing backflow. The guide 11 is part of a closure stopper 11a which is inserted into the angled part of the outflow branch stub 7 and which closes a corresponding opening in the outflow branch stub 7; the assembly of the individual parts can be carried out through this opening.

-9 A discharge channel 16 is located in the side wall of the dome-shaped housing part 4 and this connects the interior of the housing part 4 with the surroundings and, as in the embodiment illustrated, can be designed as a simple opening in the wall of the housing part 4. A valve member 17 is mounted in the cylindrical valve chamber 6 for displacement in longitudinal direction. This valve member 17 is sealed in relation to the housing 2 by means of a membrane seal 18. The outer edge area of this membrane seal 18 is clamped between the two housing parts 3, 4; these can, for example, be screwed to one another. The inner edge area of the membrane seal 18 is clamped to the inner side of the valve member 17 at its end on the outflow side, namely between an edge area of the valve member 17 designed as a sealing edge 19, on the one hand, and, on the other hand, a clamping ring 20 which is inserted into the valve member 17 and can, for example, be screwed into the valve member 17. In this respect, the membrane seal 18 covers the sealing edge 19; as long as the valve member 17 is in the open position, the membrane seal 18 maintains a distance to the sealing edge 19; however, when the valve member 17 is moved into the closed position, the membrane seal 18 abuts on the sealing edge 19 on the outside. In the closed position, the membrane seal 18 is clamped between this sealing edge 19 and a sealing seat 21 on the inner side of the housing part 4; this sealing seat 21 is a conically narrowing wall area. The membrane seal 18 then forms the sealing element between the sealing edge 19, on the one hand, and this sealing seat 21, on the other hand. The part of the membrane seal arranged in this area forms a thickened area 22, i.e., the membrane seal 18 is of a thicker design in this section than in the remaining areas. As a result, a reliable sealing between sealing edge 19, on the one hand, and sealing seat 21, on the other hand, results. In addition, the thickened area 22 covers the discharge channel 16 when the valve member 17 - 10 is in a closed position (Figures 2 and 3); the membrane seal 18 is, however, lifted away from the discharge channel 16 when the valve member 17 is moved into the open position (Figure 1). The valve member 17 is of a sleeve-like design and has a sealing area 23 widening conically from the inflow side and a circular cylindrical section 24 adjoining this area. A closing member 30 is mounted in the interior space formed as a result so as to be displaceable in longitudinal direction and is essentially of the same construction as the closing member 10; in a disk shaped head part 25, a ring seal 27 is placed in a circumferential groove 26 and a central shaft 28 forming an extension adjoins the head part 25 and this shaft is surrounded by a pressure spring 29 which is supported, on the one hand, on the dome-shaped housing part 4 and, on the other hand, on the plate-like head part 25 and, as a result, presses the closing member 30 sealingly against the sealing area 23; in this respect, the seal is brought about by the abutment of the ring seal 27 on the sealing area 23. The closing member 30 and the sealing area 23 form a second return valve. The pressure spring 29 has not only the effect that the closing member 30 is moved into the closed position in sealing abutment on the sealing area 23 but also the valve member 17 is moved into its open position by the pressure spring 29 via the closing member 30 abutting on the sealing area 23; this open position is illustrated in Figure 1. The shaft 28 is designed to be of such a length that its end 31 located opposite the plate-like head part 25 comes to rest on the closing member 10 when the valve member 17 is in a closed position and when the closing member 30 is moved into an open position. For this purpose, a recess 32 is - 11 provided in the closing member 30, in which the tapered end 31 of the shaft 28 can engage. Several projections 33 which point in the direction towards the inflow branch stub 5 are arranged centrally on the plate-like head part 25 of the closing member 30 and project slightly beyond the edge of the valve member 17 on the inflow side when the closing member 30 is closed. During normal operation, the user device is connected by means of the device for preventing backflow to a supply line, in which liquid with overpressure is made available. The device 1 for preventing backflow then operates like a known device for preventing backflow. The valve member 17 is in an open position and the two return valves in a closed position prior to the supply line system being opened. This position is illustrated in Figure 1. As soon as the supply line is opened, the pressure of the inflowing liquid moves the valve member into the closed position; this position is illustrated in Figure 2. In addition, the liquid then opens the two return valves and the liquid can be supplied to the user device. When pressure peaks occur in the user device, which would cause the liquid to flow back, the return valves close and prevent any such backflow. When an apparatus with the device for preventing backflow connected is intended to be used for suction operation, a special short connection pipe 34 is inserted into the inflow branch stub 5, as illustrated in Figure 3. The short connection pipe 34 has on one side a piece of pipe 35 which engages in the inflow branch stub 5 and on the other side, for example, a tubular nipple 36, onto which a suction hose can be pushed. The depth of insertion may be limited by a circumferential flange 37; in addition, the piece of pipe 35 is provided at its outflow side with transverse ribs 38 which do not substantially - 12 hinder any passage of the liquid but do, however, abut on the projections 33 of the closing member 30 during the insertion of the piece of pipe 35. This abutment takes place before the piece of pipe 35 is completely inserted. When the piece of pipe 35 is inserted further, the closing member 30 is therefore pushed into the housing 2 contrary to the action of the pressure spring 29 and thereby opens the return valve located upstream. When the piece of pipe 35 is inserted further, this abuts on the end edge 39 of the valve member 17 on the inflow side and likewise pushes this into the housing 2 until the valve member 17 closes the discharge channel 16 by means of the membrane seal 18 placed over the discharge channel 16. During this advancing movement, the closing member 30 is, of course, also pushed further into the housing 2 and abuts with its shaft 28 on the closing member 10; this is moved into its open position as a result so that, finally, both return valves are open when the piece of pipe 35 is completely inserted and the discharge channel 16 is closed. This position is illustrated in Figure 3. In this position, liquid drawn in can flow through the device for preventing backflow unhindered; the action of the return valves is, however, nullified so that suction operation is actually possible at all. Therefore, the same device 1 for preventing backflow can be used for operation in a pressure supply system and alternatively in a pressure-less supply system; in the latter, the action of the return valves is nullified due to use of the special short connection pipe 34 and, in addition, the valve member 17 is moved into its closed position by the short connection pipe 34. As soon as the short connection pipe 34 has been removed again from the housing 2, for example, by screwing it out of the housing, all the parts return to the rest position which is illustrated in Figure 1 and so the device 1 for preventing backflow can now be used again in the customary manner with a supply system under pressure, with which no short connection pipe may, of course, - 13 be used which moves the valve member as well as the two closing members as explained on the basis of the short connection pipe 34; this movement must be brought about solely by the pressure of the liquid flowing through in the case of a system under pressure.

Claims

1. Device (1) for preventing backflow with a housing (2) having an inlet and an outlet and forming a flow path leading from the inlet to the outlet, two return valves in the flow path opening in the direction of flow and being connected one behind the other, a discharge channel (16) exiting from the intermediate space between the two return valves, a valve member (17) closing the discharge channel (16) and being displaceable in the housing (2) in a sealed manner in relation to it, said valve member being moved into an open position releasing the discharge channel (16) due to the action of a spring and into a closed position contrary to the action of the spring when the housing (2) has liquid flowing through it and said valve member accommodating in it the return valve arranged upstream, characterized in that a membrane seal (18) is provided for sealing the valve member (17) in relation to the housing (2), the outer edge area of said membrane seal being secured to the inner wall of the housing (2) in a sealed manner and its inner edge area being secured within a sealing edge (19) of the valve member (17) so as to be sealed against it in such a manner that the membrane seal (18) extends over the sealing edge (19) and the valve member (17) in its closed position abuts on a sealing seat (21) of the housing (2) with the sealing edge (19) with the membrane seal (18) interposed between them. - 15

2. Device for preventing backflow as defined in claim 1, characterized in that the outer edge area of the membrane seal (18) is clamped between two parts (3, 4) of the housing (2) connected to one another.

3. Device for preventing backflow as defined in claim 1 or 2, characterized in that the inner edge area of the membrane seal (18) is clamped between two parts (19, 20) of the valve member (17) connected to one another.

4. Device for preventing backflow as defined in any one of the preceding claims, characterized in that the discharge channel (16) is arranged in the sealing area, the sealing edge (19) pressing the membrane seal (18) against the sealing seat (21) of the housing (2) in said sealing area.

5. Device for preventing backflow as defined in any one of the preceding claims, characterized in that the membrane seal (18) has a greater material thickness in the sealing area between sealing edge (19) and sealing seat (21) of the housing (2) than in the remaining areas.

6. Device for preventing backflow as defined in any one of the preceding claims, characterized in that it has a blocking device (34, 35) securing both return valves (9, 20; 23, 30) in an open position and the valve member (17) in a closed position.

7. Device for preventing backflow as defined in claim 6, characterized in that the return valve (23, 30) in the valve member (17) moves the other return valve (9, 10) into an open position via an actuating - 16 element (28) during its displacement into the open position and with the valve member (17) moved into a closed position.

8. Device for preventing backflow as defined in claim 7, characterized in that the closing members (10, 30) of the two return valves are displaceable axially parallel to one another and that the actuating element is an extension (28) providing a force-locking connection between the closing members (10, 30) as soon as the valve member (17) is in a closed position and the closing member (30) in the return valve of the valve member (17) is moved into an open position whereas such a force-locking connection is not provided irrespective of the position of the closing member (30) in the valve member (17) when the valve member (17) is in an open position.

9. Device for preventing backflow as defined in claim 8, characterized in that the closing members (10, 30) of the two return valves are displaceable coaxially to one another.

10. Device for preventing backflow as defined in one of claims 8 or 9, characterized in that the extension is a push rod (28).

11. Device for preventing backflow as defined in any one of claims 8 to 10, characterized in that the extension (28) is part of the closing member (30) in the valve member (17).

12. Device for preventing backflow as defined in any one of claims 6 to 11, characterized in that the actuating device contains a push element (34) adapted to abut on the closing member (30) of the return valve in - 17 the valve member (17) in the direction of displacement and to be moved in the direction of displacement of the closing member (30).

13. Device for preventing backflow as defined in claim 12, characterized in that the push element (34) is insertable into the housing (2) through the supply (5).

14. Device for preventing backflow as defined in claim 13, characterized in that the push element includes a piece of pipe (35).

15. Device for preventing backflow as defined in claim 14, characterized in that the piece of pipe (35) is part of a short connection pipe (34) to the supply (5) communicating with a supply line.

16. Device for preventing backflow as defined in claim 15, characterized in that the supply line is a suction line and bears a suction head at its end located opposite the short connection pipe (34), any connection to a supply line under pressure being precluded by said suction head.

17. Device for preventing backflow as defined in any one of claims 12 to 16, characterized in that the closing member (30) in the valve member (17) has a stop limiting its opening movement in relation to the valve member (17) so that during the advancing of the push element (34, 35) over a distance greater than the stroke of the closing member (30) in the valve member (17) the closing member (30) moves the valve member (17) into its closed position.

18. Device for preventing backflow as defined in any one of claims 12 to 16, characterized in that the push element (34, 35) abuts first of all on - 18 the closing member (30) of the return valve arranged in the valve member (17) and also on the valve member (17) only after its displacement into an open position.

19. Device for preventing backflow as defined in claim 18, characterized in that the closing member (30) bears a projection (33) protruding beyond the valve member (17), the push element (34, 35) coming to rest on said projection.