The invention relates to a filtering device for fluids , in particular lubricating oils or fuels , with a filter housing having a fluid inlet , with a main filter unit provided with a rotatable back-flushing element arranged in the filter housing, with a filtrate outlet for filtrate that is filtered with a main filter surface of the main filter unit and that is generated in that respect , and with a secondary filter unit for processing a back-flushing fluid accumulating during the back-flushing of the main filter surface of the main filter unit , wherein the main filter surface of the main filter unit can be cleaned partially by back-flushing by means of the back-flushing element and the back-flushing element enables a continuous partial back-flushing of the main filter surface . The invention further also relates to a filter circuit with at least one consumer that can be supplied with fluid as fuel or lubricant , with a fluid tank and with a filtering device arranged in the circuit between the fluid tank and the consumer .

Filtering devices for fuels or lubricants are used in engines for vehicles and in many machines . In order to improve the service life of corresponding filtering devices , it is known to provide the filtering devices with at least one unit designed as an automatic filter that can be back-flushed . The filter surface of the filter unit can then be partially cleaned by back-flushing by means of a back-flushing element , while the filter surface of the filter unit that is not subj ect to back-flushing is available for the filtering process , so that the consumer is permanently supplied with fuel or lubricant .

It is also known to connect several filter units in series or in parallel , whereby one unit forms a main filter and another unit a secondary filter . Furthermore , it is known to process the back- flushing fluid occurring during back-flushing , in order to continue to make available a portion of the back-flushing fluid that has been processed by means of a filter process as a fuel or lubricant . For example , it is known for the processing to connect a centrifuge to the outlet for the back-flushing fluid, in which centrifuge only solids remain .

In particular on vehicles , the available installation space is limited . This applies not only to land vehicles or agricultural machines , but also in particular to ships ; on ships there also exists the fact that on the one hand the filtered out dirt particles have to be stored on the ship until a port has been reached where they can be disposed of , and on the other hand, a supply of further lubricants or fuels can only be covered in the next port .

It is the obj ect of the invention to create a filtering device that has a simple structure and ensures good cleaning of the fluid with a small amount of fluid loss occurring .

To solve this problem, it is suggested with the invention that the secondary filter unit is arranged in the filter housing of the main filter unit and is provided with a back-flushing device that preferably is operable or is operated at intervals for cleaning a filter surface of the secondary filter unit preferably at intervals , and that the back-flushing device has a processing unit connected downstream for processing the dirt fluid accumulating during back- flushing of the filter surface of the secondary filter unit . The solution according to the invention therefore provides a multiple , at least 2 -fold flushing oil processing integrated in the housing of the main filter unit , and namely on the one hand with a secondary filter unit that can again be back-flushed and additionally with a further processing unit connected downstream of the secondary filter unit . Hereby, the dirt particles are concentrated in ( at least ) two stages .

In the particularly preferred design of a filter device according to the invention, the processing unit is arranged in the filter housing together with the main filter unit and the secondary filter unit . All 3 units are thus located in the same housing; this enables an optimized compact structure and thereby a minimal size of the housing with very short and therefore low-loss flow paths for the fluid at the same time . According to an advantageous design, the back-flushing element for the main filter unit is connected to a flushing fluid line within the filter housing which opens into the entry of the secondary filter unit .

Further preferably, the back-flushing devices of the secondary filter unit can have a back-flushing member that can be rotated at intervals , wherein the back-flushing member is preferably connected to a fluid line in the filter housing, which opens into the entry of the processing unit . As has already been mentioned, this enables extremely short flow paths for the fluid . An operation at intervals of the secondary filter unit ensures among others that a sufficient input pressure is available for the secondary filter unit ; this is ensured in a particularly advantageous manner when the main filter unit is designed as a permanent flusher .

For numerous possible applications it is particularly advantageous if the filter housing has a connection flange with which the filtering device can be connected as an add-on part directly to a consumer as for example a ship engine , an engine of a land vehicle , a machine or a tank . The flange can form the inlet connection for the fluid to be filtered, but it can preferably also form the filtrate outlet . At the same time , it can be ensured via the flange that the entire filtering device is favourably aligned to the horizontal .

The processing unit is again preferably constructed in a particularly simple manner and can particularly preferably have an exchangeable single filter insert or a double filter with filter inserts that cannot be back-flushed for this ; alternatively, or preferably additionally, the processing unit can have or form a sedimentation space with a closed base and a filter surface that is arranged above the base and that can be flown through from the inside to the outside . Advantageously, a filtration of the highly concentrated dirt fluid via sedimentation is thus effected with the processing unit . For this , it is particularly advantageous if the processing unit enables an inflow into the sedimentation space from above , wherein the filter insert forming the sedimentation space is exchangeable . The functionality of the processing unit also as a sedimentation chamber is particularly effective if the secondary filter unit connected upstream of this is only operated at intervals , as this allows longer periods for sedimentation without subsequent flowing fluid to be processed .

In order to ensure that a fluid flow to the consumer is guaranteed at all times , regardless of the functionalities of the individual filter units within the housing, it is particularly convenient if the main filter unit is provided with an overflow valve as bypass secured by a separate filter element . Alternatively or additionally, a valve that can be switched by means of a control device can be connected between the secondary filter unit and the processing unit , wherein the back- flushing device for the secondary filter unit is only active when the valve is open . By switching the valve , the functionality of the secondary filter unit at intervals is simultaneously effected and controlled .

A filtering device according to the invention with the aforementioned structure can be used particularly advantageously in a filter circuit with at least one consumer that can be supplied with fluid as fuel or lubricant and with a fluid tank, wherein the filtering device is then arranged in the circuit between the fluid tank and the consumer . In a filtering device with the 3 different units of main filter unit , secondary filter unit and processing unit integrated in the same housing , according to one design of the circuit , the filtrate outlet behind the main filter unit , a clean fluid outlet behind the secondary filter unit and/or a fluid outlet behind the processing unit can be connected to the same consumer, such as in particular an engine ; alternatively, a common outlet for cleaned f luid/f iltrate/clean fluid could even be provided on the housing . In this design, in particular if the secondary filter unit has a filter surface with a filter medium whose filter fineness is at least as good as that of the main filter unit , the entire filtered portion of the back-flushing fluid accumulating at the secondary filter unit can be supplied directly to the consumer, whereby some resources are saved . Alternatively, the filtrate outlet behind the main filter unit could be connectable or connected to a consumer such as in particular an engine , whereas a clean fluid outlet behind the secondary filter unit and a fluid outlet behind the processing unit are connected to a storage tank for fluid, wherein the consumer is preferably also connected to the fluid tank with a discharge line for the fluid . This mode of operation permanently improves the degree of fineness of the lubricant , as dirt particles that have been filtered out are permanently withdrawn from the circuit .

Basically, the fluid pressure in the fluid tank can be sufficient , so that a filtration can take place in the filtering device with the 3 units . In most applications , however, it is advantageous if a main pump is connected between the fluid tank and the filtering device .

Further advantages and designs of a filtering device according to the invention and a circuit having this result from the following description of advantageous exemplary embodiments shown in the drawing . In the drawing are shown :

Fig . 1 schematically, in a diagram, the basic structure of a filtering device according to the invention with three integrated units for multi-stage filtration of fluid;

Fig . 2 schematically, by means of a circuit diagram, the structure of a circuit with the integrated filter device according to the invention;

Fig. 3 schematically, by means of a circuit diagram, the structure of a circuit with an integrated, slightly modified filtering device according to the invention together with a pump between the fluid tank and the filtering device ; and

Fig . 4 schematically a simplified sectional view through a housing with the three units integrated into the housing of the main filter unit .

Figure 1 shows , by means of a highly simplified block diagram the basic structure of a filtering device according to the invention, designated altogeher by reference numeral 10 , for filtering a wing, such as a lubricant or fuel , before a consumer 1 such as a ship ' s engine . It goes without saying that several consumers , possibly also different ones , could be supplied with the same filtering device 10 , in particular if the fluid flowing through the filtering device is a lubricant . The filtering device 10 has three units integrated in a housing 11 , which is indicated here only schematically, namely a main filter unit 20 , a secondary filter unit 30 and a processing unit 40 . The main filter unit 20 is designed as an automatic filter that can be back-flushed . Fluid enters the main filter unit 20 from a fluid tank 2 via an inlet at the housing 11 . The largest partial flow of the fluid is filtered with the main filter unit 20 and is then supplied to the consumer ( s ) 1 as filtrate , as indicated by the flow arrow 29 . The portion of back-flushing fluid accumulating in the main filter unit 20 due to the back-flushing process is , as indicated by the flow arrow 28 , supplied to the secondary filter unit 30 that is arranged in the housing 11 . The portion of clean fluid that has been filtered or freed from dirt particles in the secondary filter unit 30 is , as indicated by the flow arrow 39 , supplied to the fluid tank 2 . As the secondary filter unit 30 can also be back-flushed according to the invention, a portion of again concentrated dirt liquid results at the same time , as indicated by the flow arrow 38 , which is again supplied to the third processing unit 40 arranged in the housing 11 . A fluid flow of processed fluid also results at the processing unit 40 and is supplied to the fluid tank 2 , as indicated by the flow arrow 49 ; in addition, a portion of comparatively highly concentrated dirt particles results , which in the exemplary embodiment shown are supplied to a dirt fluid storage tank 50 , as indicated by the flow arrow 48 . However , this is only schematic, because the processing unit preferably consists of an exchangeable filter insert , in which all dirt particles are retained, and which is then exchanged for another filter insert when a filling level with dirt particles or degree of contamination of the filter medium is reached, wherein all dirt particles remain in the filter insert . The processing filter thus generally does not have an outlet for dirt fluid, but only an exit for cleaned or processed fluid .

The illustration in figure 2 transfers the basic structure of the filtering device according to figure 1 to a circuit ; the same reference numbers are therefore used; in the illustration according to figure 2 , the fluid tank 2 is integrated into the base of a consumer 1 such as an engine . A supply line 3 leads from the fluid tank 2 into a fluid inlet 12 at the housing 11 of the filtering device 10 . The fluid then flows , here with a very short flow path, into the entry of the main filter unit 20 and is filtered on a main filter surface 21 of the main filter unit 20 with the degree of fineness of the filter medium of the main filter surface 21 . The correspondingly filtered portion of the fluid flow exits the housing behind the main filter surface 21 of the main filter unit 20 via a filtrate outlet 13 on the housing 11 and can be supplied to the consumer as filtered fluid via a filtrate supply line 14 . As the main filter unit 20 can be back-flushed and for this , as will be explained with reference to figure 4 , is preferably provided with a back-flushing element for permanent , partial back- flushing of a partial surface of the main filter surface 21 , a fluid flow of back-flushing fluid results at the main filter unit 20 during the back-flushing , which takes place in the opposite direction to the filtering device , preferably by back-flowing filtrate , preferably permanently, which fluid flow exits the main filter unit 20 at an internal flushing fluid exit 22 and enters the secondary filter unit

30 via an internal fluid line 25 ; for this purpose , it has an entry indicated with reference numeral 32 . On the secondary filter surface

31 of the secondary filter unit 30 , the actual fluid flow of back- flushing fluid is filtered again, whereby, on the one hand, a fluid flow of filtered clean fluid results , which exits at a clean fluid outlet 15 from the housing 11 of the filtering device 10 and also , via a separate line 16 , is also supplied to the consumer 1 . As , according to the invention, the secondary filter unit 30 can also be back- flushed and has a back-flushing member for this , as will be explained with reference to figure 4 , a partial flow with a more highly concentrated dirt content results again, which is supplied via an internal line 61 to the third processing unit 40 arranged in the housing 11 . The secondary filter unit 30 is preferably operated at intervals , for which a controllable valve 60 is arranged in the internal line 61 . A preferably partial back-flushing of the secondary filter surface 31 only takes place when the valve 60 is open . Behind the valve 60 , the line 61 opens into the entry of the processing unit 40 . This also has a filter surface 41 , but it is preferably a single filter, in particular a filter insert that can be flown through from the inside to the outside , as will be explained with reference to figure 4 . The fluid flow passing through the filter surface 41 of the processing unit 40 exits the housing 11 as processed clean fluid via the fluid outlet 18 and can also be supplied to the consumer 1 via a further separate line 19 . All dirt particles filtered out on the filter surface 41 remain in the processing filter 40 which, for this , as already mentioned, is preferably provided with a completely exchangeable filter insert and which can be replaced with a new filter insert .

If the 3 units in the housing 11 should be completely clogged and not enable a sufficient fluid flow of filtrate , an overflow unit 70 with an overflow valve 71 and a filter element 72 connected downstream thereof as a bypass is assigned to protect the circuit and the consumer 1 . The valve 71 preferably opens when a preset differential pressure is exceeded, but it can also be controllable .

Figure 3 shows a slightly modified circuit . Compared to the previous exemplary embodiment , components that are functionally identical are provided with reference numerals increased by 100 . The consumer 101 and the fluid tank 102 are designed separately and are connected to each another via a line 180 . A pump 190 for increasing the pressure for the consumer and the filtering device 110 connected upstream of this is arranged in the supply line 103 between the fluid tank 102 and the inlet 112 on the housing 111 of the filtering device 110 . The fluid then first flows into the main filter unit 120 that can be back- flushed, which is provided with a back-flushing element , wherein the filtrate obtained on the main filter surface 121 is supplied to the consumer, while the back-flushing fluid is supplied to the secondary filter unit 130 operating at intervals , which, as already explained, can also be back-flushed, however only at intervals by activating a valve 160 arranged in the housing 111 via the present external control device 195 . Here , the clean fluid obtained on the secondary filter surface 131 of the secondary filter unit 130 flows into the fluid tank 102 via the line 116 . However , when the valve 160 is open, the dirt fluid that occurs during the back-flushing of the secondary filter surface 131 enters the processing unit 140 , wherein the dirt particles are retained in the processing unit 140 , and only the outflowing fluid flow flows back into the fluid tank 102 as processed ( clean ) fluid via the line 119 .

Figure 4 illustrates the structure and dimensioning of the individual units within the filtering device 210 , wherein reference numerals increased by 100 are used here too for functionally identical components compared to the two previous exemplary embodiments . As can be seen clearly, a main filter unit 220 with the largest dimensions and a secondary filter unit 230 with significantly smaller dimensions as well as a processing unit 240 with dimensions similar to this are arranged within the same housing 211 . The housing 211 has a flange 291 as a connecting piece , via which the entire filtering device 210 can be flanged to an engine and via which, for example , the filtrate obtained with the filtering device 210 can be supplied to the engine . The main filter unit 220 has a support body 225 , which is cylindrical here and is provided with slit-shaped passages or suitably shaped recesses , with a pleated filter medium 226 surrounding it as the main filter surface 221 , and inside the support body 225 , a back-flushing element 227 is arranged that can be rotated about an axis of a central flushing line 224 , which back-flushing element is moved past the inside of the support body 225 with a flushing head 223 and partially cleans the filter surface 221 only in the area of the flushing head 229 . In the case of a pleated filter medium having numerous folds , one of the folds can respectively be assigned to a corresponding breakthrough in the support body in order to respectively clean individual folds of the filter mean in a targeted manner . A pleated filter medium ensures an enlarged filter surface with respect to the diameter of the support body 225 . More than 90% of the total filter surface is therefore permanently available for the filtration, and at the same time a relatively high back-flushing flow results in the area of the flushing head 223 , as is basically known to the person s killed in the art for the structure of a corresponding automatic filter, which is why the structure is not explained further here . The central back-flushing line 224 of the back-flushing element 227 opens via an internal line guide , not shown, into the interior of the secondary filter unit 230 , which basically has a very similar structure to the main filter unit 220 , but is significantly smaller in its dimensions and has a correspondingly smaller volume and also a correspondingly smaller dimensioned filter surface . The secondary filter unit also has a support body 235 and a pleated filter medium 236 supported on the circumference of the support body 235 , which is provided with recesses , as a secondary filter surface 221 , wherein, for back- flushing the filter medium 236 in the interior of the support body 235 , a back-flushing element 237 is provided that can be rotated around a central dirt line 234 and that has a flushing head 233 . Here , too , the flushing head 233 acts only partially on a partial surface of the filter medium 236 , which is why a large part of the secondary filter surface 231 is available for filtration at all times .

The dirt fluid accumulating via the flushing head 233 and the flushing line 234 in the secondary filter unit 230 , which is more concentrated than the back-flushing fluid in the main filter unit 220 , flows preferably from above into the processing unit 240 via an internal line , again not shown . This has a filter insert with a cylindrical support body 245 provided with recesses , which is again surrounded by a pleated filter medium 246 here , which forms the actual filter surface 241 of the processing unit 240 . The filter medium 246 preferably extends in a cylindrical manner above a closed base 242 , so that an exchangeable filter insert is present within the processing unit 240 , which can be completely exchanged . If the inflow from above is only temporary, the processing unit 240 can form a sedimentation space with the filter insert , whereby the individual dirt particles are deposited above the base 242 , whereas fluid which passes through the filter medium 246 can again be returned to the actual circuit as filtered fluid .

The invention is not limited to the previously described embodiments of filtration systems . Individual characteristics of the respective embodiments could also be combined with one another , even if this is not expressly mentioned with reference to the figures . Individual elements , as far as they do not have a direct functional connection with other individual elements , can also be omitted without departing from the scope of protection and the disclosure content of the application . The back-flushing elements or back-flushing members shown in the drawings are only exemplary designs . Other designs and modes of operation for filter elements that can be back-flushed within the housing could also be used . The processing unit 240 could also have a larger volume than the secondary filter unit , in order to make better use of the sedimentation . The use of pleated filter media to form the filter surface in all three units forms a preferred design, but individual or all the units could also have other filter media or filter surfaces .