EP0709527B1 - Backflow prevention device - Google Patents

Description

The invention relates to a backflow prevention device.
Backflow prevention devices are used for liquid and gaseous media in order to prevent that the medium flowing through the safety device can get from the outlet of the device back to the entrance and from there back into the supply network.

To prevent this from happening, there are known facilities with two in a row in a common housing arranged backflow preventer provided the different Have locking springs and if sufficient Supply pressure of the flow medium overcome can be.

It is also known that between the two non-return valves arranged chamber via a relief valve open to the outside when the pressure difference, specified by the setpoint spring of the input side Backflow preventer by a certain Amount is not reached. This can e.g. B. then occur if on one or both non-return valves a defect occurs, for example due to contamination caused in the flowing medium can, the tight closing of the backflow preventer impaired. Then you can use the setpoint spring predetermined minimum pressure difference no longer formed become. For example, the input side is then transferred Pressure in case of missing withdrawal on the exit side in the chamber between the non-return valves. This has the consequence that the relief valve a removal outside into the atmosphere and so the Pressure difference maintained. A backflow of the This prevents the medium.

The prior art is shown in WO-A-89 11611 and DE-C-42 31 494.

The invention is based, between the two non-return valves Chamber with regard to the structural dimensions in Reduce longitudinal direction of the facility. This is solved in a backflow prevention device according to claim 1. The two seats for relief valve and inlet-side backflow preventer are arranged radially concentrically on the same component, and the guide means for the relief valve and inlet-side backflow preventer are between the seats of the component within the chamber. Furthermore, the actuating means for the relief valve in the area in front of the inlet Backflow preventer placed and preferably provided with a resilient sealing element by the sealing element simultaneously as a spring in the opening direction of the relief valve acts. Even the common one Setpoint spring for check valve on the input side and relief valve as tension spring in the Inflow area of the facility. To redirection losses to decrease the flow in the chamber, is the seat of the non-return valve on the outlet side with respect to its outer diameter equal or larger than the outside diameter of the cone of the input side Backflow preventer. Through these measures the emptying speed of the chamber into the Atmosphere increases and the flow resistance between non-return valve on the inlet and outlet side reduced.

Since there are only the common ones in the chamber Guide means for inlet check valve and relief valve are located, lead small Coefficients of friction for high functional reliability of the facility.

In the following the invention with reference to the drawings explained in detail.

Fig. 1 einen Längsschnitt durch die anmeldungsgemäße Einrichtung in Sicherheitsstellung;

Fig. 2 einen Längsschnitt bei geschlossenem Entlastungsventil und fehlender Entnahme am Ausgang der Einrichtung;

Fig. 3 einen Längsschnitt bei geschlossenem Entlastungsventil und geöffneten Rückflußverhinderern.

Show it:

1 shows a longitudinal section through the device according to the application in the safety position.

2 shows a longitudinal section with the relief valve closed and no removal at the outlet of the device;

Fig. 3 shows a longitudinal section with the relief valve closed and open check valves.

The cylindrical casing (1) has on both sides the stepped holes (2, 3), the different Have lengths. In the area of the drilled holes (2, 3) are with respect to the center line of the Casing (1) the opposite holes (4). Furthermore, the jacket (1) in the area of stepped bore (2) the circular opening (41) on. In the area of the stepped bore (3) is over the threaded screws (5), the holes (4), the input part (6) connected to the jacket (1). In the area of the stepped bore (2) the holes via threaded screws (5) (4), the middle part (8), the output part (7) connected to the jacket (1). The thread of the screws (5) seals in the threaded holes of the parts (6, 7, 8).

The middle part (8) has the stepped through hole (32,33), an enlarged in the middle part (8) Diameter (42) and at the start of the bore (32) has a 45 ° bevel (43). In the area of the slope (43) is the groove (30) for receiving the square seal (31). The output part (7) bumps with the middle part (8) by encircling the square seal (34) on each other and has the bore (44), which is slightly larger than the inner diameter the square seal (34). The Bore (44) widens in the middle part of the output part (7) and carries the hub (37) over the webs (36), which is provided with a through hole (45). The cone (38) is in the through bore (45) his shaft (39) guided and is longitudinally displaceable under the spring preload of a spring (40). The Cone (38) has a 45 ° bevel (46) on which the square sealing element (34) can seal. The Input part (6) is with a stepped through hole (11, 12) provided and points in the outside area the offset part (15, 16). At the remote area (15) of the input part (6) is the resilient Seal (35) welded tight. Also tightly welded is the resilient seal (35) in the area (18) of the closure body (17). The through hole (23) of the closure body (17) merges into the 45 ° slope (20) and has a radial outside diameter opposite the bevel (20) also the 45 ° bevel (25). The closure body (17) is in the stepped Bore (32) over the between the slopes (20, 25) arranged webs (21) guided longitudinally and can with its bevel (25) compared to the square Seal the sealing element (31). Within the Guide webs (21) of the closure body (17) the cone (24) is longitudinally displaceable and in the open position limited by the stop (22) of the guide webs (21), the outer diameter of the cone (24) being equal to or smaller than the diameter of the stepped bore (33). The cone (24) carries the square Seal (19), which is opposite the slope (20) of the Sealing body (17) seals. The one with a cross hole (27) provided scar (26) is connected to the cone (24). The transverse hole (27) is used to hang one Tension spring (28) with its other end on one part (29) is attached. This part (29) is held in the stepped bore (11, 12).

Fig. 1 shows the device in the absence of pressure on Entrance (13) in the safety position. About the traction the spring (28) and the force of the elastic Sealing element (35) lifts the cone (24) with the square Seal (19) the closure body (17) from the square seal (31). The chamber (14) is via the circular opening (41) in the jacket (1) with the atmosphere connected. The closure body (17) is in the open position through the offset part (16) of the input part (6) limited. The cone (38) is over the Spring (40) against the square seal (34) pressed and thereby seals the outlet (47) opposite the chamber (14).

2, the pressure at the inlet (13) shifts the Closure body (17) against the force of the tension spring (28) and the force of the elastic seal (35) until the closure body (17) over its Slant (25) opposite the seal (31) in the middle part (8) seals. The square seal (31) limits thereby a further longitudinal shift. Only after a certain increase in pressure on Entrance (13) is the cone (24) with its square Seal (19) from the slope (20) of the closure body (17) against the force of the tension spring (28) lifted off (Fig. 3). That certain increase the pressure is determined by the spring forces (28, 35) and the two active surfaces on the one hand the resilient seal (35), on the other hand of the cone (24) with the outer diameter of the square Seal (19).

Fig. 3 shows the operation of the device Exceeding a predetermined pressure difference between Entrance (13) and exit (47). When closed Closure body (17) opposite the square Seal (31) is the cone (24) with the square Seal (19) from the slope (20) of the closure body (17) against the force of the tension spring (28) is lifted and is limited by the stop (22) of the guide webs (21). At the same time, too the cone (38) with its shaft (39) in the Through hole (45) of the hub (37) is guided, against the force of the spring (40) from the square Gasket (34) lifted off. The security device is in the flow position.

Claims (5)

1. A backflow prevention device for fluid and gaseous media with two backflow preventers, located one behind the other, forming an intermediate chamber provided with a relief valve which is controlled by the differential pressure between the inlet and the intermediate chamber and opens the intermediate chamber into the atmosphere before the differential pressure is equal to zero, characterized in that the two seats (20, 25) for the relief valve and the backflow preventer on the inlet side are located radially and concentrically on the closing body (17) and the closing body (17) is connected with the concentric seats (20, 25) with an elastic seal (35) and the quadratic seal (19) is under the force of the tension spring (28) and the force of the elastic seal (35) via the cone (24).
2. The backflow prevention device according to claim 1, characterized in that the seats (20, 25) are implemented as 45° diagonals and are located between the diagonals of the guide bars (21) with the stops (22).
3. The backflow prevention device according to claim 1, characterized in that the closing body (17) and the cone (24) are guided by the guide bars (21).
4. The backflow prevention device according to claim 1, characterized in that it has a central part (5) with an offset through boring (33), with the external diameter of the cone (24) being equal to or smaller than the diameter of the offset boring (33).
5. The backflow prevention device according to claim 1,
   characterized in that the tension spring (28) and the elastic seal (35), when viewed in the direction of flow, are located before the closing body (17), and the elastic seal (35) supports the tension spring (28) in the opening direction of the closing body (17).

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