Device and method for backflushing a filter, and system for filtering

Abstract

The present invention relates to a possibility for backflushing a filter (12), which has less disadvantages associated with it than previously. Above all, the activation of backflushing without external power supply is possible and corresponding devices (10) and systems can have a very robust, modularly expandable and simple design, wherein the components necessary for this purpose have only a low weight and are cost-effective and easy to maintain.

Description

[0001] Device and method for backwashing a filter and system for filtering

[0002] The present invention relates to a device for backwashing a filter according to the preamble of claim 1, a method for backwashing a filter according to the preamble of claim 11 and a system for filtering according to the preamble of claim 13.

[0003] Filter systems, especially those used for water filtration, are available in a wide variety of designs. Such filter systems can improve the quality of the filtered medium and, above all, reduce its contamination with contaminants.

[0004] In this context, it is also known that filters used in such filter systems become clogged after a certain period of use, causing the filter performance to decrease or even collapse completely.

[0005] To clean these filters, it is also known to perform a backwash, in which the filter is flushed in the opposite direction. This removes the particles clogging the filter and can be discharged via a drain along with the backwash.

[0006] To perform backwashing, the pump pumping the medium must be turned off, a multi-way valve must be switched to reverse the flow direction of the medium, and then the pump must be turned back on. After backwashing is complete, the pump must be turned off again, the multi-way valve must be switched to reverse the flow direction of the medium, and then the pump must be turned back on.

[0007] When the medium to be filtered then flows through the filter again in the working direction, it regains its full performance and the medium can be filtered in sufficient quantities.

[0008] The disadvantage of this type of filter cleaning is that the backwashing process is not automatic, but must be initiated manually. Alternatively, the backwashing can also be automatic, for which a corresponding electronic control unit is available. However, this type of filter cleaning is difficult to use in crisis areas, as such control units usually require electricity and are difficult to repair.

[0009] The object of the present invention is therefore to propose a method for backwashing a filter that overcomes at least one of the disadvantages described above. In particular, the backwash activation should be possible without an external power supply and should be very robust and simple in design, with the necessary components being lightweight, cost-effective, and easy to maintain.

[0010] This object is achieved with the device according to the invention for backwashing a filter according to claim 1, the method according to the invention for backwashing a filter according to claim 11 and the system for filtering according to the invention according to claim 13. Advantageous further developments are specified in the dependent claims and in the following description together with the figures.

[0011] The inventors realized that this problem can be solved in a surprising way and particularly easily if the backwashing is carried out by compressed air, because then an automatic backwashing can take place, which is also possible without electrical control devices.

[0012] The device according to the invention for backwashing a filter, wherein the device has a filter feed and a filter post-flow, wherein the filter feed can be connected to a filter feed connection of the filter and the filter post-flow can be connected to a filter post-flow connection of the filter such that a medium to be filtered which is guided through the filter feed is filtered in the filter and is released as filtered medium from the filter into the filter post-flow, is characterized in that the device has a compressed gas connection and a switching device which connects the compressed gas connection to the filter post-flow when the pressure of the medium to be filtered in the filter feed rises to a specific first value, or which connects the compressed gas connection to the filter post-flow when the pressure of the filtered medium in the filter post-flow falls to a specific second value.In an advantageous development, the switching device comprises an initiator configured to block the compressed gas connection and open it only when the specified first value or the specified second value is reached. The initiator preferably comprises a spring element that preloads a pressure sensor arranged in the filter upstream or downstream. Such an initiator can be designed purely mechanically and is therefore very robust and easy to maintain.

[0013] In an advantageous development, the initiator has a ball valve in the compressed gas connection, which is actuated by a piston. The piston is preferably preloaded and, in particular, is coupled to the pressure sensor. This makes the initiator particularly simple.

[0014] In an advantageous development, the switching device comprises an injector which is designed such that incoming compressed gas is fed to the filter downstream flow and the inlet of the medium to be filtered is connected to an outflow. Such an injector can also be designed purely mechanically and is therefore very robust and easy to maintain. Because the inlet of the medium to be filtered is connected to the outflow, this inlet does not have to be blocked, meaning that the feed pump for the inlet does not have to be switched off, but can run without interruption. Preferably, the connection between the filter downstream flow and the outflow for the filtered medium is blocked so that the compressed gas cannot escape in the direction of the outflow for the filtered medium and does not have to take the entire path through the filter for backflushing.

[0015] In an advantageous development, the injector comprises an inlet for the medium to be filtered, a connected outlet for the medium to be filtered, and an outlet. A valve is provided that, in a first position, blocks both the inlet for the medium to be filtered and the outlet for the medium to be filtered from the outlet, and, in a second position, opens both the inlet for the medium to be filtered and the outlet for the medium to be filtered from the outlet. This makes the injector particularly simple, reliable, and robust.In an advantageous development, the injector has an inlet for the filtered medium, an outlet for the filtered medium, and an inlet for the compressed gas, wherein there is a changeover valve which, in a first switching position, connects the inlet for the filtered medium with the outlet for the filtered medium and blocks the inlet for the compressed gas from the inlet for the filtered medium, and which, in a second switching position, blocks the inlet for the filtered medium from the outlet for the filtered medium and connects the inlet for the compressed gas to the inlet for the filtered medium, wherein the changeover valve is designed such that it is switched from the first switching position to the second switching position by the inflow of compressed gas into the inlet for the compressed gas. This also makes the injector particularly simple, reliable, and robust.

[0016] In an advantageous development, the switching valve is coupled to the valve, so that switching the switching valve to the first switching position results in the first position of the valve, and switching the switching valve to the second switching position results in the second position of the valve. This gives the injector a particularly simple and compact design.

[0017] In an advantageous development, the compressed gas is held in a reservoir fed by a compressor, with the compressor preferably configured to shut off when a certain pressure in the reservoir is exceeded. This makes the device particularly energy-efficient.

[0018] In an advantageous development, the accumulator is separated from the compressor when the compressed gas connection is connected to the filter downstream flow. Preferably, the initiator is designed such that the accumulator is separated from the compressor when the compressed gas connection is opened, and that the accumulator is connected to the compressor when the compressed gas connection is closed. This also makes the device particularly energy-efficient.

[0019] In an advantageous development, it is provided that no electrical or electronic means are required for determining the first specific pressure and the second specific pressure. This makes the device particularly fail-safe and usable even under conditions where no power is available. In an advantageous development, it is provided that the switching device does not have any electrical or electronic means. This makes the device particularly fail-safe and usable even under conditions where no power is available.

[0020] In an advantageous further development, the device, independent of a pump drive, contains no electrical or electronic means. This makes the device particularly fail-safe and suitable for use even under conditions where no power is available.

[0021] In an advantageous development, the device includes means for manually initiating the cleaning process. This allows cleaning to be carried out manually as needed. The means for manual activation are preferably designed as a button valve, manual switch, or manually operated 2 / 2-way valve.

[0022] In an advantageous development, a pressure relief valve is provided in a feedback line of the initiator, which is preferably adjustable. This allows for precise adjustment of the minimum cleaning pressure, since this valve only allows pressures above a certain value to pass through.

[0023] In an advantageous further development, it is provided that a throttle silencer is provided in a feedback line of the initiator, which is preferably designed to be adjustable.

[0024] This ensures a constant, throttled release of residual pressure in the feedback line, resetting the initiator and thus completing the cleaning process. The throttle silencer preferably has a hole with an adjustable diameter or a screw in front of a hole that allows the hole to be gradually closed.

[0025] In an advantageous development, a check valve is provided in a feedback line of the initiator. This prevents the flow of control air from the feedback line to other filter units. In the event of a filter unit failure or a break in the control line, the filter can still be cleaned manually while the supply air is still present. In an advantageous development, the initiator is designed to be mechanically separated from a pressure switch, wherein the pressure switch is preferably designed to switch the initiator pneumatically, wherein the pressure switch is designed in particular as a 2 / 2-way valve. This makes the device more cost-effective and fail-safe. Furthermore, manual deactivation of the cleaning function is also permitted.

[0026] In an advantageous development, a control line is provided for triggering the initiator. A switching valve is connected to the control line and is designed to interrupt the flow of the medium to be filtered to the filter when a predetermined pressure in the control line is exceeded. This relieves the load on the device, as it now only has to discharge backwash medium from the filter through the drain and no longer also has to discharge the inflowing medium to be filtered. This allows the chamber to be designed smaller, in principle, without the size of the pump having an impact on cleaning.

[0027] Independent protection is claimed for the method according to the invention for backwashing a filter, wherein the device has a filter feed and a filter post-flow, wherein the filter feed is connectable to a filter feed connection of the filter and the filter post-flow is connectable to a filter post-flow connection of the filter such that a medium to be filtered which is guided through the filter feed is filtered in the filter and is discharged as filtered medium from the filter into the filter post-flow, which is characterized in that the device has a compressed gas connection and a switching device which connects the compressed gas connection to the filter post-flow when the pressure of the medium to be filtered in the filter feed rises to a specific first value, or which connects the compressed gas connection to the filter post-flow when the pressure of the filtered medium in the filter post-flow falls to a specific second value.

[0028] In an advantageous further development, it is provided that the device according to the invention is used.

[0029] In an advantageous development, the determination of the first determined pressure and the second determined pressure takes place without electrical or electronic means. This makes the method particularly fail-safe and can be carried out even under conditions in which no power is available. In an advantageous development, the switching device performs the switching without electrical or electronic means. This makes the method particularly fail-safe and can be carried out even under conditions in which no power is available.

[0030] In an advantageous development, the method is carried out independently of a pump drive, without the use of electrical or electronic means. This makes the method particularly fail-safe and can also be carried out under conditions where no power is available.

[0031] Furthermore, independent protection is claimed for the system according to the invention for filtering medium to be filtered, which is characterized in that there is at least one device according to the invention for backwashing.

[0032] In an advantageous development, at least two filters are connected in series and / or at least two filters are connected in parallel with respect to the medium to be filtered, with each filter having its own backflushing device. This allows the medium to be filtered particularly finely or with high capacity. The system operates particularly effectively if there is a central compressed gas supply, which is connected to the individual devices, in particular via a check valve.

[0033] In an advantageous further development, it is provided that the backwashing device assigned to the filter furthest upstream in the flow direction of the medium to be filtered is adapted to supply compressed gas to the backwashing devices assigned downstream in the flow direction of the medium to be filtered in order to control these downstream backwashing devices, wherein the compressed gas can be supplied to the downstream backwashing devices in series or in parallel. The system then works particularly well with backwashing that responds to overpressure. In particular, if the downstream backwashing devices do not have their own pressure switches for detecting overpressure, there is a high level of reliability. For this purpose, there is preferably a pressure switch unit that is designed independently of the backwashing device assigned to the filter furthest upstream in the flow direction of the medium to be filtered.The backwashing devices can then be designed identically, supporting a modular system structure. Alternatively, the pressure switch unit could also be designed as part of the backwashing device assigned to the filter furthest upstream in the flow direction of the medium to be filtered.

[0034] In an advantageous development, the backwashing device associated with the filter furthest downstream in the flow direction of the medium to be filtered is adapted to supply compressed gas to the backwashing devices associated with the upstream filters in the flow direction of the medium to be filtered, in order to control these upstream backwashing devices. The compressed gas can be supplied to the upstream devices in series or in parallel. The system then works particularly well with negative pressure-responsive backwashing. In particular, if the upstream backwashing devices do not have their own pressure switches for detecting negative pressure, a high degree of reliability is ensured.

[0035] In an advantageous development, a pressure switch unit is provided that is adapted to measure the pressure from the media flow of the medium to be filtered and, at a predetermined pressure, to activate at least one, preferably at least two, backwashing devices simultaneously. This allows multiple filter devices to be controlled simultaneously. Furthermore, modularity is increased.

[0036] The features and further advantages of the present invention will become clear below from the description of preferred embodiments in conjunction with the figures. These show, purely schematically:

[0037] Fig. 1a shows the device according to the invention for backwashing a filter in a first preferred embodiment in a schematic diagram for a first operating state,

[0038] Fig. lb the device according to the invention according to Fig. la in a schematic representation for a second operating state,

[0039] Fig. 2 shows the device according to the invention according to Fig. 1 in a detailed representation for the first operating state, Fig. 3 shows the device according to the invention according to Fig. 1 in a detailed representation for the second operating state,

[0040] Fig. 4a, b, c, d the structure of the initiator according to the invention of the device according to the invention according to Fig. 1 in different states,

[0041] Fig. 5a, b the structure of the injector according to the invention of the device according to the invention according to Fig. 1 in different states,

[0042] Fig. 6 shows the device according to the invention for backwashing a filter in a second preferred embodiment in a schematic diagram for a first operating state,

[0043] Fig. 7 the system according to the invention with the device according to the invention in a first preferred embodiment,

[0044] Fig. 8 the system according to the invention with the device according to the invention in a second preferred embodiment,

[0045] Fig. 9 shows the device according to the invention for backwashing a filter in a third preferred embodiment in a schematic diagram for a first operating state,

[0046] Fig. 10 shows the device according to the invention according to Fig. 9 in a schematic diagram for a second operating state,

[0047] Fig. 11 the system according to the invention according to Fig. 7 or 8 in a further

[0048] Principle representation,

[0049] Fig. 12 the system according to the invention with the device according to the invention in a third preferred embodiment,

[0050] Fig. 13 the system according to the invention according to Fig. 12 in a further schematic representation,

[0051] Fig. 14 the system according to the invention with the device according to the invention in a fourth preferred embodiment,

[0052] Fig. 15 the system according to the invention according to Fig. 14 in a further schematic representation,

[0053] Fig. 16 shows the device according to the invention for backwashing a filter in a fourth preferred embodiment in a schematic diagram for a first operating state,

[0054] Fig. 17 shows the structure of the initiator according to the invention of the device according to the invention according to Fig. 16 in one state, Fig. 18 shows the system according to the invention with the device according to the invention in a fifth preferred embodiment,

[0055] Fig. 19 the system according to the invention according to Fig. 18 in a further schematic representation,

[0056] Fig. 20 the system according to the invention with the device according to the invention in a sixth preferred embodiment,

[0057] Fig. 21 the system according to the invention according to Fig. 20 in a further schematic representation,

[0058] Fig. 22 the system according to the invention with the device according to the invention in a seventh preferred embodiment and

[0059] Fig. 23 the system according to the invention according to Fig. 22 in a further schematic representation.

[0060] In Figs. 1a and 1b, the device 10 according to the invention for backwashing a filter 12 is shown purely schematically for two different operating states, with Fig. 1a showing normal operation and Fig. 1b showing backwash operation. Check valves required for safe operation are not shown for the sake of clarity, but are present.

[0061] It can be seen that the filter 12 has a filter feed connection 14 which is connected to a filter feed 16 of the device 10, and a filter post-flow connection 18 which is connected to a filter post-flow 20 of the device 10.

[0062] Furthermore, the device 10 has an initiator 22, an injector 24 and a compressed gas device 26 as well as a media inlet 28 for the supply of the medium to be filtered (in the embodiment water) and a media outlet 30 for the removal of the filtered medium.

[0063] With regard to the compressed gas flow, the initiator 22 is a 2 / 2-way valve with a spring 32 whose preload is adjustable (explained below) for a valve 33 connected to the filter supply line 16. In fact, the initiator 22 is integrated between the media inlet 28 and the filter supply line 16 and is flowed through by the medium to be filtered. The injector 24 is a 6 / 2-way valve and has an inlet 34 for the medium to be filtered, an outlet 36 for the medium to be filtered, and an outlet 38. There is also an inlet 40 for the filtered medium and an outlet 42 for the filtered medium. Furthermore, there is a spring preload 44 for a changeover valve 46. Finally, the injector 24 has an inlet 48 for compressed gas, with the compressed gas also controlling the changeover valve 46.

[0064] The compressed gas device 26 has a compressor 52, which is driven by a motor 54 (for example, an electric or gasoline engine) and is connected to a compressed gas reservoir 58 via a control valve 56. The compressed gas reservoir 58, in turn, is connected to the compressed gas connection 60 of the initiator 22, while the compressed gas outlet 62 of the initiator 22 is connected to the compressed gas inlet 48 of the injector 24. The control valve 56 is designed such that the compressor 52 operates against air pressure when sufficient pressure for the compressed gas (air in the exemplary embodiment) has built up in the reservoir 58.

[0065] In the normal operating state shown in Fig. 1a, the compressed gas connection 60 is closed off from the compressed gas outlet 62, so that no compressed gas is supplied to the injector 24. As a result, the switching valve 46 of the injector 24 is positioned such that the inlet 34 for the medium to be filtered is connected to the outlet 36 for the medium to be filtered, the inlet 40 for the filtered medium is connected to the outlet 42 for the filtered medium, and both the outlet 38 and the inlet 48 for compressed gas are closed.

[0066] As a result, the medium to be filtered, which is supplied through the media inlet 28, can be cleaned by the filter 12 and removed again as filtered medium through the media outlet 30.

[0067] In the backwash operating state shown in Fig. 1b, the compressed gas connection 60 is not blocked from the compressed gas outlet 62, so that compressed gas is supplied to the injector 24. As a result, the changeover valve 46 of the injector 24 is positioned such that the inlet 40 for the filtered medium is connected to the inlet 48 for compressed gas, and both the inlet 34 for the medium to be filtered and the outlet 36 for the medium to be filtered are connected to the outlet 38. In this case, the outlet 42 for the filtered medium is blocked. This allows the filter 12 to be backwashed, with the filtered medium being forced back through the filter 20 by the compressed gas, thereby loosening contaminants that are fed to the outlet 38 together with the filtered medium and the medium to be filtered.

[0068] In Figs. 2 and 3, the device 10 according to the invention is shown in detailed views for the two operating states.

[0069] It can be seen that the initiator 22 has an inlet 64 for the medium 66 to be filtered, which comes from the media inlet 28, and an outlet 68 for the medium 66 to be filtered. A pressure sensor 70 in the form of a piston is arranged between the inlet 64 and the outlet 68. The pressure sensor 70 is preloaded in the direction of the flowing medium 66 by the spring 72, which extends around a plunger 74 of the piston 70 and is supported against a ceiling 76 of the first chamber 78 of the initiator 22, in which the piston 70 runs. The chamber 78 is ventilated via an opening 80 and, together with the piston 70, is sealed off from the medium 66 to be filtered.

[0070] The plunger 74 penetrates the cover 76 and extends into a second chamber 82, where it acts against the actuator 84. The plunger 74 is guided in a sealed manner in the opening 86.

[0071] The second chamber 82 is connected to the compressed gas connection 60, wherein the compressed gas connection 60 has a valve 88 formed by a ball 92 acting against a valve seat 90, which is biased against the valve seat 90 by a spring 94. The valve 88 blocks the compressed gas connection 60 so that no compressed gas can enter the chamber 82 when the ball 92 is on the valve seat 90.

[0072] The second chamber 84 is connected to the compressed gas outlet 62. Furthermore, a spring 32 biases the actuator 84 toward the plunger 74, with the spring strength being adjustable by an adjusting screw 96.

[0073] The actuating body 84 has an actuating surface 98 which does not act against the ball 92 when the actuating body 84 is in its lowest position, as shown in Fig. 2. The actuating body 84, in interaction with the ball valve 88, forms the valve 33. Since the actuating surface 98 is inclined relative to the vertical V, when the actuating body 84 is moved upwards it comes into contact with the ball 92 and displaces it against the spring 94, whereby the valve seat 90 is released, as shown in Fig.

[0074] 3 is shown.

[0075] The vertical displacement of the adjusting body 84 is effected by the plunger 74, which pushes the adjusting body 84 upward when the piston 70 is pushed upward by a pressure of the medium 66 to be filtered that exceeds the force of the spring 72. This occurs when the filter 12 becomes clogged, causing the pressure in the filter supply line 16 to rise above a predetermined value.

[0076] By opening valve 88, compressed gas 100 flows into chamber 82 and initially passes beneath actuator 84, causing the compressed gas to act on the bottom 99 of actuator 84, thereby further raising actuator 84, so that both valve 88 and compressed gas outlet 62, which would otherwise be completely blocked by actuator 84, are fully opened. The compressed gas 100 flowing out of compressed gas outlet 62 is fed to inlet 48 for compressed gas 100.

[0077] The injector 24 has two separate chambers 102, 104, wherein in one chamber 102 there is the valve 106, which is formed by a piston 108 with a tappet 110, which is surrounded by a spring 112, which is supported on a ceiling 113 of the chamber 102, and the sealing seat 114, against which the piston 108 acts.

[0078] By means of the valve 106, the inlet 34 for the medium 66 to be filtered and the filter flow 16 can be connected to each other alone (cf. Fig. 2) or the inlet 34 for the medium 66 to be filtered and the filter flow 16 can be connected together with the outlet 38 (cf. Fig. 3).

[0079] The plunger 110 extends sealed through the ceiling 113 of the chamber 102 into the chamber 104, with the plunger 110 being firmly connected to the piston 116. This piston 116 cooperates with a first sealing seat 118 and a second sealing seat 120 to either close off the chamber 104 from the inlet 48 for the compressed gas 100 (see Fig. 2) or close off the chamber 104 from the outlet 42 for the filtered medium 121 (see Fig. 3). More precisely, the force of the spring 112 presses the piston 116 against the sealing seat 118, thereby closing off the chamber 104 from the inlet 48 for the compressed gas 100 (see Fig. 2).

[0080] Conversely, when compressed gas 100 flows through inlet 48, piston 116 is raised against the force of spring 112 and pressed against sealing seat 120, thereby blocking chamber 104 from outlet 42 for the filtered medium 121 (see Fig. 3). At the same time, inlet 48 for compressed gas 100 is connected to filter downstream 20, and inlet 34 for the medium to be filtered and filter upstream 16 are jointly connected to outlet 38 (see Fig. 3).

[0081] Thus, if the initiator 22 does not detect any overpressure in the filter feed line 16, the pressure gas connection 60 remains closed, so that the chamber 104 remains closed with respect to the outlet 42 for the filtered medium 121 and the inlet 34 for the medium to be filtered is directly connected to the filter feed line 16 and the outlet 38 is closed.

[0082] As a result, the medium 66 to be filtered flows from the media inlet 28 into the filter 12 and is filtered from there to the media outlet.

[0083] If, however, an overpressure is detected in the filter feed line 16, the medium 66 to be filtered is transferred from the media inlet 28 to the outlet 38, and the compressed gas 100 pushes the filtered medium located in the chamber 104 and the filter downstream 20 back into the filter 12, thereby backflushing the filter 12 and clearing it again. The particles thus removed from the filter 12 are transferred as backflushing medium 122 through the filter feed line connection 14 into the filter feed line 16 and the chamber 102 and discharged through the outlet 38.

[0084] It is essential that the valve 88 of the initiator 22 is self-opening: As soon as it has been opened via the pressure sensor 70 and the tappet 74, it remains open due to the compressed gas 100 acting on its base 99 until the reservoir 58 is emptied or the pressure of the compressed gas 100 is no longer able to overcome the force of the spring 32. In addition, the injector 24 automatically remains in the switching position shown in Fig. 3 as long as sufficient compressed gas 100 flows into the injector 24. The force of the spring 32 is adjustable. If the spring force is increased, a higher compressed air pressure is required to keep the valve 88 open. To a first approximation, the pressure of the compressed air reservoir 58 decreases linearly as it is emptied. With a higher spring force, the compressed air introduction and thus the cleaning is shorter and with a lower spring force, the cleaning can last until the compressed air reservoir 58 is almost completely emptied.This is particularly relevant due to filter housings differing in volume, whereby smaller filter housings are cleaned more quickly and it is therefore not necessary to empty the entire compressed air reservoir 58.

[0085] At the same time, the force of spring 32 also acts on piston 70 via body 84, so that the spring preload with respect to piston 70 is also adjustable. This allows the activation of valve 22 to be adjusted for different pressures. For example, by varying spring preloads 32, activation can occur at 1 bar or 3 bar. This allows adaptation to different filters (with different natural resistances. For example, a 5 pm filter has a base resistance of 1.5 bar, so the initiator 22 should ideally be set to 3 bar. A 200 pm filter, on the other hand, has a base resistance of 0.5 bar, so the initiator 22 should be set to 1.5 bar), but also to filter cascades that increase the base resistance.

[0086] As an alternative to the illustrated embodiment, the force of spring 72 can also be directly adjustable. This would allow the forces of springs 32 and 72 to be adjusted independently of each other.

[0087] Thus, in the event of a drop in filter performance, which is determined by a pressure increase in the filter feed line 16, further filtering is automatically and abruptly stopped and backflushing is carried out until the compressed gas 100 in the reservoir 58 is used up or no longer has sufficient pressure, after which the filtering of the medium 66 to be filtered is continued again.

[0088] 4a to 4d, the initiator 22 is shown in a specific embodiment in various states. It can be seen that the initiator 22 has an actuating body 84 which runs in a sealed manner in the chamber 82. In Fig. 4a, the actuating body 84 is shown in a state corresponding to Fig. 2, wherein the valve 88 is blocked because the pressure in the filter supply line 16 is not yet too high. Fig. 4b shows a transitional state when the compressed gas is just acting on the bottom 99 of the actuating body 84, which was raised by the plunger 74. Fig. 4c shows the state of Fig. 3, wherein the pressure in the filter supply line 16 is no longer high enough to raise the piston 70, but the inflowing compressed gas 100 continues to push the actuating body 84 upwards. Finally, Fig. 4c shows the state corresponding to Fig.2, when no more compressed gas is available or the pressure of the compressed gas is too low, the actuator 84 is pushed downward by the spring 32, thereby automatically closing the valve 88. This also closes the compressed gas connection 60, allowing the reservoir 58 to be refilled with compressed gas.

[0089] In Fig. 5a and 5b, the injector 24 is shown in a concrete embodiment in two states corresponding to Figs. 2 and 3. For the injector 24, it can also be seen that the piston 116 is designed as a long cylinder.

[0090] By flowing in compressed gas 100 via the inlet 48, the piston 116 is lifted, thereby lifting it from the valve seat 118 and pressing it against the valve seat 120. This allows the compressed gas 100 to flow past the piston 116 into the filter downstream section 20.

[0091] It can also be seen that the plunger 110 extends upwards beyond the piston 116 and ends in a knob 124. By pulling this knob 124 upwards, the drain 38 can be activated in the event of a possible malfunction, thereby depressurizing the filter 12.

[0092] The feedback line 126 shows (cf. Fig. 1a) that the initiator 22 is designed to be self-opening, as already described above.

[0093] Fig. 6 shows a first alternative embodiment of the device 200 compared to Fig. 1, in which the pressure switch 202 is not part of the initiator 204, but exists independently of it. The initiator 204 therefore only has the compressed gas guide with the corresponding valve (not shown), but not the guide for the medium to be filtered. This pressure switch 202 is also adjustable with respect to the spring force 205. Furthermore, the knob 124 can also be seen here, which is not shown in Fig. 1 but is also present.

[0094] In addition, a check valve 206 is arranged in the pressure gas line to prevent the medium to be filtered from entering the pressure gas line.

[0095] In Fig. 7, a first preferred application of the device according to the invention in the form of a cascade system 250 is shown purely schematically.

[0096] It can be seen that there are three different devices 252, 254, 256, which are connected in series with respect to the flow direction of the medium to be filtered 258. The three devices 252, 254, 256 each have different filters 12, where device 252 has a coarse filter, device 254 has a medium filter, and device 256 has a fine filter (each not shown), so that the medium to be filtered can be filtered particularly cleanly and is output as filtered medium 260 with high purity.

[0097] For all devices 252, 254, 256 there is a uniform compressed gas generation 262, which in turn has a compressor 264 which is driven by a motor 266 and is connected via a control valve 268 to the respective compressed gas reservoirs (not shown) of the devices 252, 254, 256.

[0098] To prevent air from one compressed gas storage tank from being released into another compressed gas storage tank using the path of least resistance and not contributing to the cleaning, check valves 270, 272, 274 are provided.

[0099] All facilities 252, 254, 256 are connected to a single drain 276.

[0100] In Fig. 8, a second preferred application of the device according to the invention in the form of a parallel system 300 is shown purely schematically.

[0101] It can be seen that here, too, there are three devices 302, 304, 306, but, compared to Fig. 7, these are connected in parallel with respect to the flow direction of the medium 308 to be filtered. The three devices 302, 304, 306 each have identical filters (not shown), so that the filter capacities of the individual devices 302, 304, 306 add up.

[0102] If it becomes apparent in the cascade system 250 shown in Fig. 7 that certain devices 252, 254, 256 become clogged more frequently than others and therefore backwashing must be performed more frequently for these devices 252, 254, 256, these devices can be configured with two or more devices in parallel, similar to the parallel system 300 shown in Fig. 8. Due to the modular design, such an expansion is very simple and quick.

[0103] In Figs. 9 and 10, a second alternative embodiment of the device 350 to Fig. 1 is shown in that here the initiator 352 is not designed as a 2 / 2-way valve, but as a 3 / 2-way valve.

[0104] In contrast to the device 200 according to Fig. 6, here the compressed gas reservoir 354 is designed to be separable from the compressor 356. More precisely, in the normal operating state shown in Fig. 9, the compressed gas reservoir 354 is connected to the compressor 356 via the initiator 252 and is separated from the injector 358, while in the backflushing operating state shown in Fig. 10, the compressed gas reservoir 354 is separated from the compressor 356 and connected to the injector 358 via the initiator 352.

[0105] This prevents the compressed gas reservoir 354 from charging during backflushing operation, allowing the compressed gas reservoir to be completely discharged during backflushing operation. This is advantageous in the case of low pressures of the medium to be filtered, because in this case, the charging pressure from the compressor can lead to the initiator's self-opening function not being interrupted, thus making a return to normal operation impossible. This separation in device 350 ensures that the self-opening function is always interrupted, at the latest when the compressed gas reservoir 354 is completely emptied.

[0106] Fig. 11 shows how the systems 250 and 300 can be implemented using the device 350 according to Fig. 10, wherein for the sake of clarity only two such devices 350', 350" are shown here, but any number could be combined with one another. To implement the cascade system 250 according to Fig. 7, the medium to be filtered would be fed to the media inlet 370 of the first device 350' and the medium filtered by the first device 350' would be removed from the media outlet 372 and fed to the media inlet 374 of the second device 350" and the medium filtered by the second device 350" would be removed from the media outlet 376, and so on.

[0107] In order to implement the parallel system 300 according to Fig. 8, the medium to be filtered would be fed simultaneously to the media inlet 370 of the first device 350' and to the media inlet 374 of the second device 350", and simultaneously the medium filtered by the first device 350' would be removed from the media outlet 372 and the medium filtered by the second device 350" would be removed from the media outlet 376, and so on.

[0108] In Fig. 12, a third preferred application of the device according to the invention in the form of a cascade system 400 is shown purely schematically.

[0109] It can be seen that this cascade system 400 differs from the cascade system 250 according to Fig. 7 in that the individual devices 402, 404, 406 are each connected via control lines 408, 410, wherein check valves 412, 414 exist in these control lines 408, 410.

[0110] Fig. 13 shows an implementation of this cascade system 400 by means of the inventive devices 350a, 350b according to Fig. 10.

[0111] It can be seen that the control line 408 is connected to the compressed gas outlet 416 of the initiator 352 of the first device 350a and to the self-opening device 418 of the initiator 352 of the second device 350b.

[0112] Thus, if a device 350a upstream in the flow direction switches to backwash operation, all devices 350b downstream in the flow direction are simultaneously switched to backwash operation.

[0113] In contrast, the switching of a downstream device 350b in the flow direction does not result in the upstream device 350a being switched to backwash mode due to the check valve 412. This prevents unnecessary backwashing.

[0114] In Fig. 14, a fourth preferred application of the device according to the invention in the form of a cascade system 450 is shown purely schematically.

[0115] This cascade system 450 differs from the cascade system 400 according to Fig. 12 only in that only the device 452 furthest upstream in the flow direction has, in addition to the initiator 470, its own pressure switch 472, while the devices 454, 456 downstream in the flow direction only have their own initiators 470 but no pressure switches of their own.

[0116] Fig. 15 shows an implementation of this cascade system 450 by means of the devices 350a according to the invention and devices 350b' modified therefrom according to Fig. 10, wherein the device 350b', as previously described, does not have a pressure switch but only its own initiator 470.

[0117] Thus, when the device 350a furthest upstream in the flow direction switches to backwash operation, all devices 350b downstream in the flow direction are simultaneously switched to backwash operation.

[0118] In contrast, the downstream devices 350b' cannot switch to backwash mode due to the lack of pressure switches. This allows for component savings and thus reduces costs. However, this is not a disadvantage, as it prevents unnecessary backwashing.

[0119] Fig. 16 shows a third alternative embodiment of device 500 compared to device 10 shown in Fig. 1, in which the initiator 502 does not react to an overpressure in the media inlet 504, but rather to a negative pressure in the media outlet 506. Such a negative pressure occurs when the filter 12 becomes clogged. Otherwise, this device 500 is identical to the device 10 shown in Fig. 1.

[0120] In Fig. 17, the initiator 502 corresponding to Fig. 4 is shown in more detail. It can be seen that the initiator 502 differs from the initiator 22 according to Fig. 4 only in that a chamber 514 is arranged below the inlet 510 and outlet 512 for the medium to be filtered, in which chamber a pressure sensor 516 in the form of a piston is arranged, which is prestressed by the spring 518 against the direction of the flowing medium.

[0121] This spring extends around a plunger 520 of the piston 516 and rests against a circular projection 522. The piston 516 runs in the chamber 514, sealed from the medium to be filtered.

[0122] The plunger 520 again penetrates the cover 524 and extends into a second chamber 526, where it acts against the actuating body 528. The plunger 520 is guided in a sealed manner in the opening 530.

[0123] A vertical displacement of the actuator 528 is effected by the plunger 530, which pushes the actuator 528 upward when the piston 516 is pulled upward by a negative pressure of the medium to be filtered that exceeds the force of the spring 518. This occurs when the filter 12 becomes clogged and, as a result, the pressure in the filter supply line drops below a predetermined value.

[0124] Fig. 18 shows an alternative embodiment of the cascade system 550 according to the invention to the cascade system 400 according to Fig. 12.

[0125] Here, the unit 552, which is furthest upstream in the flow direction, consists of a pressure switch, an initiator, and a compressed gas reservoir, while the remaining downstream devices 554, 556, and 558 each have only initiators, injectors, and compressed gas reservoirs, but no pressure switches of their own. Consequently, device 552 also has no injector, filter, or drain of its own.

[0126] It can be seen that this cascade system 550 also differs from the cascade system 400 in that the control lines 560 here are routed parallel from the unit 552 to all downstream devices 554, 556, 558. This achieves a particularly high level of reliability because downstream devices 554, 556, 558 perform backflushing even if devices 554, 556 located intermediate to the triggering unit 552 experience a failure in the compressed gas area, which could occur, for example, due to a line break.

[0127] Fig. 19 again shows a concrete implementation of this cascade system 550.

[0128] It can be seen that the upstream unit 552 is the actual pressure switch unit and has a pressure switch 564 that reacts to overpressure, an initiator 566 and its own compressed gas reservoir 568 that only serves to supply the control line 560.

[0129] In the example shown, unit 552 exists independently of devices 554, 556, and 558, with devices 554, 556, and 558 being identical, which supports a modular design. Alternatively, unit 552 could also be configured as part of device 554.

[0130] During operation, the pressure sensor input 570 of the pressure switch 564 is connected to the connection for the medium to be filtered. The pressure sensor output 572 is connected to the media inlet 574 of the device 554, the media outlet 576 of the device 554 is connected to the media inlet 578 of the device 556, and the media outlet 580 of the device 556 is connected to the media inlet of the device 558, and so on.

[0131] Figs. 20 and 21 show an alternative embodiment of the cascade system 600 to the cascade system 550 shown in Figs. 18 and 19 in that here the pressure switch 602 does not react to overpressure, but to negative pressure.

[0132] Therefore, the pressure switch 602, with its pressure sensor input 604, is also connected to the media outlet 606 of the most downstream device 608, while the pressure sensor output 610 is connected to the media outlet 612 for the filtered medium. Here, too, the control line 614 is connected in parallel to all upstream devices 616, 618, and 620.

[0133] The media inlet 622 of the most downstream device 608 is here connected to the

[0134] Media output 624 of the directly upstream device 616 is connected and the media input of this device 616 is in turn connected to the media output of the directly upstream device 618, and so on.

[0135] Finally, Figs. 22 and 23 show an alternative embodiment of the cascade system 700 according to the invention to the cascade system 500 according to Figs. 18 and 19, wherein the basic structure is essentially the same, which is why Fig. 22 does not differ from Fig. 18.

[0136] Here, the unit 702, which is furthest upstream in the flow direction, again contains a pressure switch, an initiator, and a compressed gas reservoir, while the remaining downstream devices 704, 706, and 708 each have only initiators, injectors, and compressed gas reservoirs, but no pressure switches of their own. Consequently, device 702 also has no injector, filter, or drain of its own.

[0137] It can be seen that in this cascade system 700, the control lines 710 are routed from the unit 702 in parallel to all downstream devices 704, 706, 708.

[0138] This in turn provides a special level of reliability because downstream devices 704, 706, 708 carry out backflushing even if devices 704, 706 located intermediate to the triggering unit 702 experience a failure in the compressed gas area, which could occur, for example, due to a line break.

[0139] Fig. 23 again shows a concrete implementation of this cascade system 700, with the following mainly focusing on the differences to the cascade system according to Fig. 19.

[0140] It can be seen that the upstream unit 702 is the actual pressure switch unit and has a pressure switch 714 that reacts to overpressure, an initiator 716 and its own compressed gas reservoir 718 that only serves to supply the control line 710.

[0141] In the example shown, unit 702 again exists independently of devices 704, 706, 708, with devices 704, 706, 708 again being identically designed, which supports a modular structure. Alternatively, unit 702 could also be designed as part of device 704.

[0142] During operation, the pressure sensor input 720 of the pressure switch 714 is connected to the connection for the medium to be filtered. The pressure sensor output 722 is connected to the media inlet 724 of the device 704, the media outlet 726 of the device 704 is connected to the media inlet 728 of the device 706, and the media outlet 730 of the device 706 is connected to the media inlet of the device 708, and so on.

[0143] Compared to the cascade system 550 according to Fig. 19, the following changes now exist both in the individual devices 704, 706, 708 and in the unit 702.

[0144] The following changes apply to facilities 704, 706, 708:

[0145] A pressure relief valve 732 is located in the feedback line 734 of the pneumatically triggered control valve 736. This allows for precise adjustment of the minimum cleaning pressure, as this valve 732 only allows pressures above a certain value to pass through. As soon as the pressure in the compressed gas reservoir 738 drops to the level previously set on the pressure relief valve 732, no more pressure flows in. This regulates both the pressure used for filter cleaning and the duration of the cleaning.

[0146] An adjustable throttle silencer 740 ensures a constant, throttled residual pressure release in the feedback line 734, so that the valve 736 closes due to the spring return. This safely completes the cleaning process. The throttle silencer 740 could be implemented by providing a small hole with an adjustable diameter or by installing a screw in front of a hole, allowing the hole to be gradually closed.

[0147] An additional button valve 742 (which could alternatively be configured as a manual switch or manually operated 2 / 2-way valve) allows the manual initiation of the cleaning of an individual filter of a device 704, 706, 708 by introducing compressed gas from the compressed gas reservoir 738 into the feedback line 734 of the control valve 736, thereby switching the valve. An additional check valve 744 prevents the outflow of control air from the feedback line 736 of a device 704 to other devices 706, 708. In the event of a failure of a device 704, 706, 708 or a break in the control line 710, the filter of a device 704, 706, 708 can thus still be cleaned manually, provided the supply air 745 is still present.

[0148] Regarding unit 702, the following changes apply:

[0149] The initiator 716 has been mechanically separated from the pressure switch 714. The pressure switch 714 now actuates a pneumatic 2 / 2-way valve 746, which opens the line from the compressed gas reservoir 718 to the pneumatic circuit of the initiator 716. This initiator 716 can now also be switched with a button valve 748 (which could alternatively be designed as a manual switch or manually operated 2 / 2-way valve). Once the initiator 716 is switched, the control line 710 is pressurized. Part of this pressure is fed back to the pneumatic circuit of the initiator 716 via an adjustable pressure relief valve 750. As soon as the pressure in the compressed gas reservoir 718 has dropped to the level previously set on the pressure relief valve 750, no more pressure flows in. The initiator 716 switches back and the control line 710 is vented through the adjustable throttle silencer 740 of the devices 704, 706, 708.Another adjustable throttle silencer 752 ensures a constant limited venting of the pneumatic circuit of the initiator 716.

[0150] Independently of this, a pneumatically actuated hydraulic switching valve 754 is connected to the control line 710. This is inserted into the media flow upstream of the media inlet 720 of the pressure switch 714 and is connected between the media inlet 720 and the media outlet 722 without any pressurized gas load through the control line 710. With a pressure increase in the control line 710, the media flow from the pressure sensor inlet 720 of the pressure switch 714 to the pressure sensor outlet 722 is blocked by the switching valve 754 or, if necessary, diverted to an outlet without pressure acting on the media inlet 720. This relieves the load on the first device 704, since this device 704 now only has to discharge the backwash medium 122 from the filter 12 through the outlet 38 and no longer also has to discharge the inflowing medium 66 to be filtered. As a result, the chamber 38 can in principle be made smaller without the size of the pump having an influence on the cleaning.

[0151] Independently of this, there is a latching lever valve 756 that allows the interruption of the compressed gas supply to the pneumatic 2 / 2-way valve 746 on the pressure switch 714, so that the automatic triggering of the cleaning can be deactivated.

[0152] Finally, a pressure gauge 758 may be provided to monitor the pressure in the compressed gas reservoir 718.

[0153] It can be seen that the device 704, 706, 708 is more cost-effective and fail-safe due to the decoupling of pressure switch 714 and initiator 716. Furthermore, manual deactivation of the cleaning process is also permitted.

[0154] From the above description, it has become clear that the present invention proposes a method for backwashing a filter that is associated with fewer disadvantages than previously. Above all, backwashing can be activated without an external power supply, and corresponding devices and systems can be very robust, modularly expandable, and simply constructed. The necessary components are lightweight, cost-effective, and easy to maintain.

[0155] All features presented in the general description of the invention, the description of the exemplary embodiments, the following claims and in the figures can be essential to the invention both individually and in any combination. These features or combinations of features can each form the basis of an independent invention, the right to claim which is expressly reserved. Individual features from the description of an exemplary embodiment do not necessarily have to be combined with one or more or all of the other features specified in the description of this exemplary embodiment; in this regard, each sub-combination is expressly disclosed. Furthermore, physical features of a device or system can be reformulated and used as process features, and process features can be reformulated and used as physical features of a device or system.Such a reformulation is therefore automatically disclosed.

[0156] List of reference symbols device according to the invention

[0157] filter

[0158] Filter flow connection

[0159] Filter flow

[0160] Filter afterflow connection

[0161] Filter run-on

[0162] initiator

[0163] Injector

[0164] Compressed gas device

[0165] Media entrance

[0166] Media output

[0167] Feather

[0168] 33 Valve

[0169] Inlet for the medium to be filtered

[0170] Process for the medium to be filtered

[0171] drain

[0172] Inlet for the filtered medium

[0173] 42 Outlet for the filtered medium

[0174] Spring preload for the changeover valve 46

[0175] changeover valve

[0176] Inlet for compressed gas

[0177] 50 Control of the switching valve 46 by the compressed gas

[0178] compressor

[0179] 54 Engine, electric or petrol engine

[0180] 56 Control valve

[0181] 58 compressed gas storage tanks

[0182] 60 compressed gas connection

[0183] 62 Compressed gas outlet

[0184] 64 Inlet for the medium to be filtered coming from the media inlet 28 66 medium to be filtered 68 Outlet for the medium to be filtered 66

[0185] 70 pressure sensor, piston

[0186] 72 spring

[0187] 74 Piston tappet 70

[0188] 76 ceiling

[0189] 78 First Chamber

[0190] 80 opening

[0191] 82 second chamber

[0192] 84 actuators

[0193] 86 Opening

[0194] 88 valve

[0195] 90 valve seat

[0196] 92 ball

[0197] 94 spring

[0198] 96 Adjusting screw

[0199] 98 footprint

[0200] 99 Bottom of the actuator 84

[0201] 100 compressed gas

[0202] 102, 104 two separate chambers of the injector 24

[0203] 106 Valve

[0204] 108 pistons

[0205] 110 tappets

[0206] 112 spring

[0207] 113 Ceiling of chamber 102 supports

[0208] 114 Sealing seat

[0209] 116 pistons

[0210] 118 first sealing seat

[0211] 120 second sealing seat

[0212] 121 filtered media

[0213] 122 Backwash medium

[0214] 124 knob on plunger 110

[0215] 126 Feedback line 200 second preferred embodiment of the device according to the invention

[0216] 202 pressure switch

[0217] 204 Initiator

[0218] 205 spring force

[0219] 206 Check valve

[0220] 250 system according to the invention in a first preferred

[0221] Design, cascade system

[0222] 252, 254, 256 devices according to the invention

[0223] 258 medium to be filtered

[0224] 260 filtered medium

[0225] 262 Compressed gas generation

[0226] 264 Compressor

[0227] 266 engine

[0228] 268 control valve

[0229] 270, 272, 274 Check valves

[0230] 276 drain

[0231] 300 system according to the invention in second preferred

[0232] Design, parallel system

[0233] 302, 304, 306 devices according to the invention

[0234] 308 medium to be filtered

[0235] 350, 350', 350", 350a, 350b, 350b' third preferred embodiment of the device according to the invention

[0236] 352 Initiator

[0237] 354 compressed gas storage tanks

[0238] 356 Compressor

[0239] 358 Injector

[0240] 370 Media entrance of the first facility 350'

[0241] 372 Media exit of the first facility 350'

[0242] 374 Media entrance of the second facility 350"

[0243] 376 Media output of the second device 350"

[0244] 400 inventive system in third preferred

[0245] Design, cascade system

[0246] 402, 404, 406 devices according to the invention 408, 410 control lines

[0247] 412, 414 check valves

[0248] 416 compressed gas outlet

[0249] 450 inventive system in fourth preferred

[0250] Design, cascade system

[0251] 452 most upstream in the direction of flow

[0252] Furnishings

[0253] 454, 456 downstream devices

[0254] 470 Initiator

[0255] 472 pressure switch

[0256] 500 fourth preferred embodiment of the device according to the invention

[0257] 502 Initiator

[0258] 504 Media Entrance

[0259] 506 Media output

[0260] 510 Inlet

[0261] 512 Outlet

[0262] 514 first chamber

[0263] 516 Pressure sensor, piston

[0264] 518 spring

[0265] 520 tappets

[0266] 522 circular projection

[0267] 524 ceiling

[0268] 526 second chamber

[0269] 528 actuators

[0270] 530 Opening

[0271] 550 inventive system in fifth preferred

[0272] Design, cascade system

[0273] 552 most upstream in the direction of flow

[0274] Unit, pressure switch unit

[0275] 554, 556, 558 downstream facilities

[0276] 560 control lines

[0277] 564 pressure switch

[0278] 566 Initiator 568 Pressure gas storage

[0279] 570 Pressure sensor input of pressure switch 564

[0280] 572 Pressure sensor output

[0281] 574 Media entrance of the facility 552

[0282] 576 Media exit of the facility 552

[0283] 578 Media entrance of the facility 554

[0284] 580 Media exit of the facility 554

[0285] 600 inventive system in sixth preferred

[0286] Design, cascade system

[0287] 602 Pressure switch 602

[0288] 604 Pressure sensor input

[0289] 606 Media output

[0290] 608 most downstream facility

[0291] 610 Pressure sensor output

[0292] 612 Media output for the filtered medium

[0293] 614 Control line

[0294] 616, 618, 620 upstream facilities

[0295] 622 Media input of the most downstream

[0296] Facility 608

[0297] 624 Media output of the directly upstream facility 616

[0298] 700 inventive system in sixth preferred

[0299] Design, cascade system

[0300] 702 most upstream unit

[0301] 704, 706, 708 downstream facilities

[0302] 710 Control lines 710

[0303] 714 pressure switch

[0304] 716 Initiator

[0305] 718 compressed gas storage

[0306] 720 Pressure sensor input of pressure switch 714

[0307] 722 Pressure sensor output

[0308] 724 Media entrance of facility 704

[0309] 726 Media exit of facility 704

[0310] 728 Media input of facility 706 730 Media output of facility 706

[0311] 732 pressure relief valve

[0312] 734 Feedback line

[0313] 736 Control valve 738 Pressure gas accumulator

[0314] 740 throttle silencer

[0315] 742 button valve

[0316] 744 Check valve

[0317] 745 supply air 746 pneumatic 2 / 2-way valve

[0318] 748 button valve

[0319] 750 adjustable pressure relief valve

[0320] 752 throttle silencer

[0321] 754 Switching valve 756 Lever valve

[0322] 758 Pressure Gauge V Vertical

Claims

Patent claims 1. Device for backwashing a filter, wherein the device has a filter inlet and a filter outlet, wherein the filter inlet can be connected to a filter inlet port of the filter and the filter outlet can be connected to a filter outlet port of the filter such that a medium to be filtered, passed through the filter inlet, is filtered in the filter and discharged as filtered medium from the filter into the filter outlet, characterized in that the device has a pressurized gas port and a switching device which connects the pressurized gas port to the filter outlet when the pressure of the medium to be filtered in the filter inlet rises to a certain first value, or which connects the pressurized gas port to the filter outlet when the pressure of the filtered medium in the filter outlet falls to a certain second value.

2. Device according to claim 1, characterized in that the switching device has an initiator which is designed to block the pressurized gas connection and only opens it when the specified first value is reached or when the specified second value is reached, wherein the initiator preferably has a spring element which pre-tensions a pressure sensor which is arranged in the filter upstream or in the filter downstream.

3. Device according to claim 1 or 2, characterized in that the switching device has an injector which is designed such that incoming pressurized gas is supplied to the filter after-flow and the inlet of medium to be filtered is connected to an outlet, wherein the injector is preferably designed such that the connection between the filter after-flow and the outlet for the filtered medium is blocked.

4. Device according to claim 3, characterized in that the injector has an inlet for medium to be filtered, an outlet for medium to be filtered connected thereto, and a drain, wherein a valve is provided which, in a first position, blocks both the inlet for medium to be filtered and the outlet for medium to be filtered relative to the drain, and in a second position opens both the inlet for medium to be filtered and the outlet for medium to be filtered relative to the drain.

5. Device according to claim 3 or 4, characterized in that the injector has an inlet for the filtered medium, an outlet for the filtered medium and a The device has an inlet for the compressed gas, comprising a switching valve which, in a first switching position, connects the inlet for the filtered medium to the outlet for the filtered medium and blocks the inlet for the compressed gas relative to the inlet for the filtered medium, and which, in a second switching position, blocks the inlet for the filtered medium relative to the outlet for the filtered medium and connects the inlet for the compressed gas to the inlet for the filtered medium, wherein the switching valve is designed such that it is switched from the first switching position to the second switching position by the inflow of compressed gas into the inlet for the compressed gas.

6. Device according to one of claims 3 to 5 in conjunction with claim 2, characterized in that the switching valve is coupled to the valve, such that switching the switching valve into the first switching position causes the first position of the valve and switching the switching valve into the second switching position causes the second position of the valve.

7. Device according to one of the preceding claims, characterized in that the pressurized gas is held in a reservoir which is supplied by a compressor, wherein the compressor is preferably configured to switch off when a certain pressure in the reservoir is exceeded, and / or that no electrically or electronically designed means exist for determining the first certain pressure and the second certain pressure, and / or that the switching device has no electrical or electronic means, and / or that the device has no electrical or electronic means independent of a drive for a pump, and / or that the device has means for manually triggering the cleaning.

8. Device according to the first alternative of claim 7, characterized in that the storage tank is separated from the compressor when the compressed gas connection is connected to the filter after-run, wherein preferably in conjunction with claim 2 it is provided that the initiator is designed such that when the compressed gas connection is opened the storage tank is separated from the compressor and that the storage tank is connected to the compressor when the compressed gas connection is closed.

9. Device according to one of the preceding claims in conjunction with claim 2, characterized in that a pressure relief valve is provided in a feedback line of the initiator, which is preferably adjustable, and / or that a throttle silencer is provided in a feedback line of the initiator, which is preferably adjustable, and / or that a check valve is provided in a feedback line of the initiator, and / or that the initiator is mechanically separated from a pressure switch, wherein the pressure switch is preferably configured to pneumatically switch the initiator, wherein the pressure switch is in particular configured as a 2 / 2-way valve.

10. Device according to one of the preceding claims in conjunction with claim 2, characterized in that a control line is provided which serves to trigger the initiator, wherein a switching valve is connected to the control line which is configured to interrupt the flow of the medium to be filtered to the filter when a predetermined pressure in the control line is exceeded.

11. A method for backflushing a filter, wherein the device has a filter inlet and a filter outlet, wherein the filter inlet can be connected to a filter inlet port of the filter and the filter outlet can be connected to a filter outlet port of the filter such that a medium to be filtered, passed through the filter inlet, is filtered in the filter and discharged as a filtered medium from the filter into the filter outlet, characterized in that the device has a pressurized gas port and a switching device that connects the pressurized gas port to the filter outlet when the pressure of the medium to be filtered in the filter inlet rises to a certain first value, or that connects the pressurized gas port to the filter outlet when the pressure of the filtered medium in the filter outlet falls to a certain second value.

12. Method according to claim 11, characterized in that the device according to one of claims 1 to 10 is used and / or that the determination of the first determined pressure and the second determined pressure is carried out without electrical or electronic means and / or that the switching by the switching device is carried out without electrical or electronic means and / or that the process is carried out independently of a drive for a pump without the use of electrical or electronic means.

13. System for filtering medium to be filtered, characterized in that at least one device for backwashing according to one of claims 1 to 8 is provided.

14. System according to claim 13, characterized in that at least two filters are connected in series and / or at least two filters are connected in parallel with respect to the medium to be filtered, wherein each filter has its own backwashing device, wherein preferably a central pressurized gas supply is provided which is connected to the individual devices in particular via a non-return valve.

15. System according to claim 13 or 14, characterized in that the backwashing device associated with the filter furthest upstream in the flow direction of the medium to be filtered is adapted to supply compressed gas to the backwashing devices associated with the filters downstream in the flow direction of the medium to be filtered for controlling these downstream backwashing devices, wherein the compressed gas can be supplied to the downstream backwashing devices in series or in parallel, wherein the downstream backwashing devices in particular do not have their own pressure switches for determining an overpressure, and / or that the backwashing device associated with the filter furthest downstream in the flow direction of the medium to be filtered is adapted,to supply compressed gas to the backwashing devices assigned to the upstream filters in the flow direction of the medium to be filtered, for controlling these upstream backwashing devices, wherein the compressed gas can be supplied to the upstream devices in series or in parallel, wherein the upstream backwashing devices in particular do not have their own pressure switches for determining a vacuum, and / or that a pressure switch unit exists which is adapted to take the pressure from the medium flow of the medium to be filtered and, at a predetermined pressure, to activate at least one, preferably at least two, backwashing devices simultaneously for backwashing.

Images