NL2003996C2

NL2003996C2 - FILTER ASSEMBLY.

Info

Publication number: NL2003996C2
Application number: NL2003996A
Authority: NL
Inventors: Henk Savooijen; Hendrikus Bernardus Dijkhuis; Pieter Gisbergen
Original assignee: Parker Filtration B V
Priority date: 2008-06-20
Filing date: 2009-12-21
Publication date: 2010-11-22
Also published as: ZA201009105B; NL2001709C2; NL2003996A1

Description

P29414NL01

Title: Filter assembly 5

FIELD OF THE INVENTION

The present invention relates to a filter assembly comprising, a filter element and a filter housing for accommodating the filter element. The assembly further comprises an end cap 10 assembly at a first end of said filter element, the end cap comprising a tubular portion open at its axial ends and forming with the filter element a first fluid flow passage. Further, the assembly comprises a filter head that is removably attachable to said filter housing and comprises an inlet port, an outlet port and an annular passage, whereby the annular passage forming with the tubular portion a second fluid flow passage. Such filters are used 15 for removing material that is entrained in a fluid stream. In relation to the present invention fluids can comprise liquids, gasses or gaseous media, liquids containing gas etc.

BACKGROUND OF THE INVENTION

20

Filter assemblies have for example been employed in a variety of applications including hydraulic systems, fuel systems and engine lubrication systems. Application of filter systems for filtering gaseous media are also known. Such assemblies for example use replaceable filter elements that can be installed on a filter head for filtering fluid flowing 25 between inlet and outlet ports in the filter head. The filter element typically is contained within a filter housing such as a can that can be screwed onto or off of the filter head. In a so-called spin-on filter, the can is discarded along with the filter element. In other arrangements, only the filter element is replaced and the filter housing is reused. During use the filter element may become clogged to the point that is causes a problem in the system, 30 such as inadequate flow to components downstream of the filter, excessive pressure upstream of the filter element, and/or damage to the filter element allowing the accumulated contaminants to flow to components downstream of the filter element. Normally this is avoided by scheduled replacement of the filter element. It is thus necessary to replace the filter element from time to time.

35 2

Filter elements commonly have a wall of a filtration medium and an end cap with an inlet (or outlet) which can be sealed to the head part of the housing to provide a flow path for a fluid stream to be supplied to the interior or space (or to be extracted from the space) within the filter element. The inlet (or outlet) is provided by a port or passage on an end cap 5 of the element. The port may e.g. have an O-ring seal on its external surface which is received in a bore within the housing end cap, in which it is compressed to form a seal. Often, such a filter element has a cylindrical shape. The fluid to be filtered enters the filter assembly via the inlet, the inlet being arranged in such manner that the fluid can distribute along the outer surface of the filter element. The fluid is then forced through the filter 10 element whereby contaminants in the fluid remain captured in the filter element and the filtered fluid is forced to an outlet of the filter assembly. As an alternative, the flow may be in opposite direction; the contaminated fluid entering the filter element axially and then being forced through the filter element thereby flowing substantially radially outward.

15 Filter assemblies as described can e.g. be applied to filter oil of a lubrication system or an hydraulic system of e.g. a crane. In order to maintain the fluid flowing through the system (i.e. comprising tubing and a filter assembly), a pump is required. This is due to the fact that both the tubing and the filter assembly represent a resistance for the fluid flow. In general, the pump can be driven by an electrical motor or a combustion engine such as 20 diesel engine for example.

In order to gain access to the filter element when it has to be replaced, the head and body parts of the housing can be separated. A problem with the known filter assemblies when replacing the filter element is, that some fluid such as for example hydraulic oil or free 25 fluid content in gasses remains in the conduit that is attached to the outlet port of the filter assembly. In case of a filter used for filtering gaseous media, the fluid content could drain out when replacing the filter element. By separating the filter housing from the filter head, this fluid may be spilled, as the filter housing is often still (partly) filled with fluid. Even if the filter housing is drained before removing it from the filter head, some fluid will flow out of the 30 conduit attached to the outlet port due to gravitation. Spilling of fluid, in particular hydraulic fluid, constitutes on the one hand a safety hazard when it is spilled on floors, on the other hand it constitutes an environmental hazard.

A filter assembly according to the preamble of claim 1 is known from JP-2000-35 225305-A. The leaf spring of JP-2000-225305-A is supported on the bottom of the can shaped filter housing containing the filter element. This leaf spring serves to keep the filter 3 element under upward pressure in order to keep it in place. This leaf spring has a smaller diameter than the filter housing.

OBJECT OF THE INVENTION 5

The present invention aims to solve the problem of unwanted spilling of fluid when separating the filter housing and the filter head when the filter element needs to be replaced.

10 SUMMARY OF THE INVENTION

The present invention solves this problem by providing a filter assembly comprising, a filter element and a filter housing for accommodating the filter element. The assembly further comprises an end cap assembly at a first end of said filter element, the end cap comprising 15 a tubular portion open at its axial ends and forming with the filter element a first fluid flow passage. Further, the assembly comprises a filter head that is removably attachable to said filter housing and comprises an inlet port, an outlet port and an annular passage in fluid communication with the outlet port, wherein the annular passage forms with the tubular portion a second fluid flow passage. The assembly further comprises a coupling assembly 20 provided in the filter housing for detachably coupling the filter element and/or the core element to the filter housing.

This coupling assembly only allows coupling with a dedicated filter element and/or core element and assures that pirated filter elements cannot be used. Furthermore, 25 coupling the filter element to the filter housing has the advantage that when the filter housing is separated from the filter head, that the filter element and/or core element will remain attached to the filter housing upon separation so that the risk of spilling fluid by dripping from the filter element and/or core element is eliminated as the filter element and/or core element are still in the housing. The leaf spring has a number of radially extending 30 resilient elements contacting the inner surface of the filter housing and allowing a resilient deformation upon insertion of the leaf spring into the filter housing. This provides a strong coupling between the coupling assembly and the filter housing.

In a further embodiment of the invention, the leaf spring is aresilient lock ring having 35 a peripheral edge that closely corresponds to an inner surface of the filter housing.

4

According to a further embodiment a valve assembly is provided in the filter head and is operable between the annular passage and the outlet port. The valve assembly comprises a valve which is axially movable within the valve assembly between a first position allowing fluid to flow through the annular passage to the outlet port and a second 5 position blocking flow through the annular passage.

By providing a valve assembly in the filter head which valve assembly has a valve which can close and open the annular passage in the filter head, any fluid remaining in the filter head and/or in a conduit attached to the outlet port is blocked from flowing out of the 10 filter head. Hence, separating the filter housing from the filter head can be done without the risk of spilling fluid which is present downstream of the filter.

In a further aspect of the invention, the tubular portion comprises an annular wall having a radial flow passage for allowing fluid to bypass the filter element, and a bypass 15 flow valve axially movable within the tubular portion between a first position blocking flow through the radial flow passage and a second position allowing flow through the radial flow passage. This allows for the filter element to be bypassed in case the filter element is clogged or obstructed. As a consequence thereof the pressure difference over the filter element increases and the pressure upstream of the filter element also increases. This 20 increased pressure difference acts on the bypass flow valve and opens the valve when a certain threshold is exceeded. This means that (part of) the fluid flow will bypass the filter element.

In a further aspect of the invention the valve comprises a first valve element and a 25 second valve element, the first and second valve element being axially movable with respect to each other, the first valve element being open toward the second valve element. The second valve element is movable between a first position abutting the first valve element so as to form a unitary valve, and a second position axially distanced from the first valve element and sealing against the tubular wall portion, blocking flow through the first 30 fluid flow passage. The first and second valve element, because of their axial movement with respect to each other can close access to the interior of the filter element and at the same time allow fluid to flow through the first valve element. In this situation a so-called reverse flow situation is established in which fluid flows from the outlet towards the inlet without flowing through the filter element. The latter is highly unwanted as this would 35 remove the filtered material or debris from the filter element. It is noted that the bypass valve in such a situation must allow flow through the radial flow passage. Both the 5 movement of the valve elements and the bypass flow valve are occasioned by a change in pressure difference over the respective valves.

Another aspect of the above embodiment of the invention is that the valve assembly 5 can only successfully prohibit a reverse flow situation in case the end cap with the annular wall portion is sealed by the second valve element. This means that the filter assembly only operates correctly when the filter element is provided with an end cap having the features as mentioned above. In turn this means, that it is not possible to use so-called pirated filter elements that do not have the required features. This is beneficial as the use of pirated or 10 copied filter elements will endanger the proper working of the filter assembly and eventually the proper and safe working of the system the filter assembly is part of.

A solution to the problem of pirated filter elements and in view thereof the problem these pirated filter elements can cause with respect to the rest of the system, such as a hydraulic 15 system, is another object of the invention and is solved by the afore-mentioned embodiment, and for example also with an embodiment according a further aspect of the invention in which, the filter assembly comprises a resilient member for biasing the bypass flow valve in its first position and comprising a further end cap assembly at an opposite end of said filter element, a perforated core element extending between said end caps in an 20 interior of the filter element and attached to said housing, said core element supporting the resilient member. In this manner any filter element that does not comprise the end cap according to the invention will not be able to work with the resilient member, which is fixed to the housing and hence always present, which will in turn interfere with the proper working of the valve element.

25

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the filter assembly according to the invention are described in the claims and in the following description with reference to the drawing, in 30 which:

Fig. 1 schematically depicts a cross-sectional view of an exemplary filter assembly according to the invention;

Fig. 2A in a sectional perspective view depicts an end cap assembly in a first closed 35 position; 6

Fig. 2B in a sectional perspective view depicts the end cap assembly in a first open position;

Fig. 3A in a sectional perspective view depicts the end cap assembly in a second closed position; 5 Fig. 3B in a sectional perspective view depicts the end cap assembly in a second open position;

Fig. 4 in a sectional perspective view depicts an alternative filter head employing the end cap assembly of figure 3A;

Fig. 5A schematically depicts in sectional view a filter head with a valve 10 assembly in no-flow-condition;

Fig. 5B schematically depicts in sectional view the filter head with the valve assembly in normal-flow-condition;

Fig. 5C schematically depicts in sectional view the filter head with the valve assembly in bypass-flow-condition; 15 Fig. 5D schematically depicts in sectional view the filter head with the valve assembly in reverse-flow-condition;

Fig. 5E schematically depicts in sectional view the filter head with the valve assembly in no-element-condition;

Fig. 6 depicts in an exploded view a part of a filter housing with a coupling 20 assembly;

Fig. 7 schematically depicts in sectional view a part of the filter housing with a lockring, and

Fig. 8 schematically depicts in sectional view a part of the filter housing with the lockring, coupling ring and end cap assembly mounted.

25

DETAILED DESCRIPTION OF EXAMPLES

Referring to Figure 1 an example of a filter assembly according to the present 30 invention is depicted. A filter assembly according to the invention is generally indicated by reference numeral 20. The filter assembly 20 comprises a filter element 21, a filter housing or body 23 and a filter head 22. The filter housing 23 may also be referred to as a bowl or can.

35 In a manner which is known per se, the filter housing 23 may be removably attached to the filter head 22 to form an interior or interior chamber arranged to contain the filter 7 element 21. The filter element 21 generally comprises a filter medium 25 which preferably is the form of a loop of filter medium of any suitable type. The filter element 21 is provided with an end cap assembly 26 at one end of the filter media and a further end cap assembly 27 at the opposite end of the filter media or filter element 21. The end cap assemblies 26 5 and 27 preferably are fixedly attached to the ends of the filter media, as by bonding with a suitable adhesive, this being a well known technique in the art.

As will be explained in more detail with respect to Figures 2A-3B, the end cap assembly 26 is located and mounted at a first end of said filter element 21. The end cap 26 10 comprises a tubular portion 28 open at its axial ends and forms with the filter element 21 a first fluid flow passage for the fluid to flow through. The end cap assembly 26 further comprises a bypass flow valve (see Figures 2A-3B) that allows the fluid to bypass the filter element 21 if circumstances so require.

15 In the illustrated embodiment, the filter housing or body 23 is removably attached to the filter head 22 by screwing the body onto the filter head. To this end, the body 23 and filter head 22 are provided with correspondingly threaded portions. The threaded portions are coaxial with the body and filter element which preferably are generally cylindrical in cross-section, as shown. The body 23, however, may be removably secured to the filter 20 head by other suitable means, such as by clamps, fasteners, etc. Other cross-sectional shapes of the filter element and/or housing are also contemplated. The filter head 22 includes inlet and outlet ports 44 and 45 respectively that may have threaded portions for connection to other system components, such as fluid inlet and outlet lines. In most cases, the port 44 will function as an inlet since it communicates with an annular space 49 in the 25 housing that is present between the filter element 21 and the inner surface of the filter housing 23. The annular space 49 surrounds the filter element 21.

This set up results in a fluid flow from the inlet port 44 to the annular space 49 and through the filter element 21, i.e. a so-called outside-to-inside flow (also referred to as out-30 to-in flow). Consequently, the port 45 will function as an outlet passage. The opposite flow configuration is also contemplated, with the hereinafter components being configured to function under such opposite flow configuration.

In the filter head 22 a valve assembly 100 is provided, which will be explained in 35 more detail referring to Figures 5A-5E. However, it is already mentioned here, that the valve assembly 100 can close an annular passage 31 provided in the filter head 22. The valve 8 assembly 100 is operable between the annular passage 31 and the outlet port 45 and is arranged to open and close the annular passage 31. In particular the valve assembly 100 can close the annular passage 31 of the filter head 22 when the filter housing 23 is removed from the filter head 22 by blocking flow from the outlet port 45 towards the annular 5 passage 31 and consequently out of the filter head 22.

Now referring to Figures 2A to 3B, the end cap assembly 26 is shown in more detail. The end cap assembly 26 comprises a flange part 32 having a generally U-shaped cross-section and is arranged to accommodate a distal end of the filter element 21 (see Figure 1). 10 The distal end of the filter element 21 can be permanently attached to the end cap 26. The end cap assembly 26 comprises a tubular portion 28 open at its axial ends and forming with the filter element 21 a first fluid flow passage, which is generally indicated with arrow A. The tubular portion 28 comprises an annular wall 29 in which a radial flow passage 34 is provided. The radial flow passage 33 preferably comprises a number of separate flow 15 passages that substantially cover the circumference of the annular wall 29.

Inside the end cap assembly 26, in particular telescopically movable within the tubular portion 28 and sealing against an inner surface of the annular wall 29, a bypass flow valve 35 is provided. The bypass flow valve 35 is arranged to be axially or telescopically movable within the tubular portion 28 between a first position blocking flow through the 20 radial flow passage 34 as is depicted in Figure 2A and a second position allowing flow through the radial flow passage 34 as is depicted in Figure 2B by arrow B. In this position of the bypass flow valve 35 part or all of the fluid flowing through the filter assembly will bypass the filter element 21. Such situations may arise when the filter media is clogged with material that has to be filtered out of the fluid and consequently that the pressure drop over 25 the filter element becomes to great. In such a situation the pressure outside the end cap assembly 26 increases, or at least the pressure difference between the interior of the end cap assembly 26 (and thus the interior of the filter element) increases, and the pressure will urge the bypass flow valve 35 in a downward direction as indicated with arrow C in Figure 2B. To achieve this, the bypass flow valve 35 comprises a pressure ridge 36 which is 30 exposed to the fluid pressure in the inlet port 44 or upstream of the filter element 21.

To allow the bypass flow valve 35 to move from its closed to its open position, the tubular portion 28 comprises a stop member 43, shaped as an inwardly extending ridge, that limits movement in the direction of arrow A, i.e. an upward movement of the bypass 35 flow valve 35. As can be seen in Figure 2A, further upward movement of the bypass flow valve 35 is limited when an axially extending lip 46 abuts the stop member 43. To allow 9 downward movement, i.e. movement of the bypass flow valve 35 to its second or open position, the tubular portion 28 has a recess 47 which can guide a second axially extending lip 48 of the bypass flow valve 35.

5 It is to be understood that the bypass flow valve 35 should only move to its second position of Figure 2B in case the circumstances require so. Hence, unwanted movement of the bypass flow valve 35 should be avoided and the bypass flow valve 35 should be kept in its first and closed position of Figure 2A during normal use, i.e. the fluid flows through the filter element 21. In order to achieve this, a resilient member or bypass spring element 37 is 10 provided with reference to Figure 1, which exerts a force on the bypass flow valve 35 such that the bypass flow valve 35 is biased towards its first or closed position.

The bypass spring element 37 is in the example of Figure 1 with its lower end supported by a core element 38 by means of a support ridge 41. With its upper end the 15 spring element 37 abuts against a retention ridge 42 (see Figure 2A, 2B) which has a smaller diameter than the (preferably) circular bypass spring element 37.

The core element 38 is designed to support the filter medium of the filter element 21 and is arranged inside the filter element 21 against the inner surface thereof. The core 20 element 38 as shown in Figure 1 comprises a tubular structure and houses a flow conduit 39 which is not part of the present invention, but which serves to reduce turbulence inside the filter element 21 to reduce power consumption of the filter assembly. The core element 38 can be a cylindrical tube of stainless steel. In the arrangement as shown the tubular structure is arranged along an inner surface of the filter medium. By doing so, the core 25 element 38 provides support to the filter medium when an out-to-in flow (indicated by the arrows 40) occurs through the filter element 21. As such, the core element 38 substantially prevents the filter medium from deforming under the pressure difference that exists across it. Without the provision of the core element 38, the filter element 21 could buckle under the pressure load and the filter assembly 20 would not function properly.

30

With reference to Figures 2A and 2B, it is noted that the configuration of the bypass flow valve 35 shown is used when the filter assembly 20 is used in the earlier mentioned out-to-in flow, i.e. the fluid flows from the inlet port 44 through the annular space 49 through the filter element 21 and the core element 38 towards the annular passage 31 and out of 35 the filter head 22 through the outlet port 45. It is also possible however that the filter assembly works according to the in-to-out principle in which the fluid substantially flows in 10 an opposite direction. Turning to Figure 3A, this is indicated with arrow D. This means however that the bypass flow valve 35 as shown in Figures 2A and 2B is no longer working correctly as the higher pressure in the filter assembly 20 will be found in the interior of the end cap assembly 26 which would urge the bypass flow valve downwards (see Figure 2B) 5 in its open position.

To this end the end cap assembly 26 and in particular the axially movable bypass flow valve 35 can be adjusted such that the bypass flow valve 35 moves upwards in Figure 3A, i.e. in a direction as indicated with arrow E in Figure 3B, thus opening the radial flow 10 passage 34 when the filter element 21 gets clogged and a bypass flow condition is required.

To achieve this double working feature of the bypass flow valve 35, the bypass flow valve 35 can be turned inside the tubular portion 28 in a clockwise direction (arrow F) 15 starting from the position as shown in Figure 2A to arrive at the position shown in Figure 3A. In this position the axially extending lip 46 is aligned with a recess 50, which allows the lip 46 to move beyond the stop member 43. It is noted that several lips and recesses can be provided.

20 While turning the bypass flow valve 35 as described above, the second lip 48 is rotated also and is positioned over a second stop member 51 which is shaped as an inwardly extending ridge. The second stop member 51 prohibits any downward movement of the bypass flow valve 35.

25 As mentioned with reference to Figures 2A and 2B, the bypass flow valve 35 should in normal use be biased in its closed position. To achieve this with the embodiment of the bypass flow valve 35 as shown in Figure 3A and 3B, the bypass flow valve 35 should be biased downward. Hence, an alternative bypass spring member is required which acts in an opposite direction as the bypass spring element 37 of Figure 1. This is shown in Figure 4.

30

Referring now to Figure 4, the filter head 22 is shown in a spatial cut-away view in a situation wherein the filter assembly is working according to the in-to-out flow principle. This is schematically indicated with arrows 60. Figure 4 again shows the end cap assembly 26 and the filter element 21. Figure 4 further shows the bypass spring element 37 which is 35 mounted inside the filter head 22 and is arranged to exert a force on the bypass flow valve 35 that biases is in its closed position.

11

Referring now to Figure 5A, the filter head 22 of the filter assembly is shown in a cross-sectional view. The filter element 21 and the filter housing 23 are not shown to improve clarity of the drawing. In the filter head 22 a valve assembly 100 is provided which 5 is mainly seated in the annular passage 31 provided in the filter head 22. The annular passage 31 is located between the inlet port 44 and the outlet port 45 and accommodates the upper part of the end cap assembly 26, more in particular the upper part of the tubular portion 28. The annular passage 31 comprises an annular wall section 52 which encloses the upper part of the tubular portion 28. Between the tubular portion 28 and the annular wall 10 section 52 a seal 53 is provided, which may be an O-ring for example.

The valve assembly 100 is operable between the annular passage 31 and the outlet port 45 and is arranged to open and close the annular passage 31. In particular the valve assembly 100 can close the annular passage 31 of the filter head 22 when the filter housing 15 23 is removed from the filter head 22 by blocking flow from the outlet port 45 towards the annular passage 31 and consequently out of the filter head 22.

The valve assembly 100 comprises a valve housing or gage 101. The gage 101 is tubular in design and has a radial flow passage 102 which is open towards the outlet port 45. The radial flow passage 102 spans about a quarter to about half of the circumference of 20 the gage 101 to allow the fluid to flow through the valve assembly 100 and towards the outlet port 45 with as low a flow resistance as possible. The gage 101 comprises a tubular guide 103 for telescopically guiding a stem 104 of a first valve element 105. The stem 104 in turn is a tubular element which telescopically guides a second stem 106 of a second valve element 107. Hence, the first valve element 105 and the second valve element 107 25 are axially movable with respect to each other.

Between the gage 101 and the first valve element 105 and located around the tubular guide 103, a first compression spring 108 is provided which rests on a flange 109 of the first valve element 105, thus biasing the first valve element 105 downwards in Figure 5A 30 such that an upper annular rim 110 the first valve element 105 seats on an annular seal ring 118 (see Figure 5E). As can be seen in Figure 5A, the second stem 106 of the second valve element 107 is located inside the tubular stem 104 of the first valve element 105 and a second compression spring 111 is provided between an end part 112 of the second stem 106 and an inner portion of the flange 109. The second compression spring 111 biases the 35 second valve element 107 upwards in Figure 5A such that a rim 113 of the second valve element 107 seats against a lower edge 114 of the first valve element 105.

12

The first valve element 105 and the second valve element 107 substantially form a single valve in the situation shown in Figure 5A because of the force exerted by the second compression spring 111. Furthermore, in the situation of Figure 5A, the rim 113 of the 5 second valve element 107 seats on a inner rim 115 of the bypass flow valve 35 such that the annular passage 31 is closed and no fluid can flow through the valve assembly 100 in either direction. Furthermore, the bypass flow valve 35 is in its closed or first position, blocking flow through the radial flow passage 34 as was explained with reference to Figures 2A-3B. Hence, the position of the valve element 100 and the bypass flow valve 35 of Figure 10 5A can be denoted as no-flow-condition.

During normal use of the filter element, which can be denoted as normal-flow-condition, the fluid to be filtered will flow through the filter element (out-to-in flow) and through the valve assembly 100 towards the outlet port 45. This situation is shown in Figure 15 5B.

In comparison with the no-flow-condition of Figure 5A, the first valve element 105 and the second valve element 107 have moved upward in Figure 5B (indicated with arrow Y) as a single valve under the influence of an increased fluid pressure, wherein said 20 increased fluid pressure must be large enough to overcome the force exerted by the first compression spring 108. In the normal-flow-condition of Figure 5B, the fluid will flowthrough the tubular portion 28, pass the closed bypass flow valve 35 and along a profiled flow guide surface 116 of the second valve element 107 towards the outlet port 45.

25 When the first valve element 105 and the second valve element 107 move upwards as indicated in Figure 5B, fluid that will be present in the tubular guide 103, which is open at its distal end, can be pushed out via said open distal end by the provision of a radially extending flow channel 119, causing a damping function of the valve (see Figure 5A).

30 As explained with reference to Figures 2A-3B, in certain circumstances it is required that the fluid flow may bypass the filter element. This situation is denoted as bypass-flow-condition and is shown in Figure 5C.

In comparison with the normal-flow-condition shown in Figure 5B, the bypass flow 35 valve 35 has been moved in a downward direction in Figure 5C (indicated with arrow Z) due to an increased pressure outside of the end cap assembly 26 and against the bias force of 13 bypass spring element 37. The fluid is now able to bypass the filter element as is indicated with arrow G. It is noted here, that the length of the bypass spring element 37 can be adjusted by changing the position of the retention ridge 41 (see Figure 1). By increasing the length of the bypass spring element 37, the hysteresis of the spring element 37 can be 5 reduced and a better and more accurate control of the opening and closing of the bypass flow valve 35 can be achieved.

In certain exceptional circumstances a flow condition denoted as reverse-flow-condition is present in the filter assembly according to the invention. This reverse-flow-10 condition is shown in Figure 5D. In this situation the fluid flows from the outlet port 45 towards the inlet port 44 and should do so without flowing through the filter element. The latter is highly unwanted as this would remove the filtered material or debris from the filter element. In the reverse-flow-condition the radial flow passage 34 must hence be open, but the fluid must not be able to reach the interior of the filter element.

15

To achieve this, the increased pressure in the outlet port 45 will move the first valve element 105 and the second valve element 107 in a downward direction (indicated with arrow Z). Downward movement of the first valve element 105 is limited by a stop member 117 on which the upper rim 110 of the first valve element 105 seats. The lower part of the 20 first valve element 105 is designed as a spider case and comprises axial flow passages that allow fluid to flow through the lower part of the first valve element 105. Hence, in the reverse-flow-condition the increased fluid pressure will push against the second valve element 107 such that it is also moved in a downward direction against the force exerted by the second compression spring 111. In its downward movement, the second valve element 25 107 will push the bypass flow valve 35 via its inner rim 115 downward also, opening the radial flow passage 34 while at the same time blocking flow through the annular passage 31. It is noted that the pressure that is required to push both the second valve element 107 and the bypass flow valve 35 downwards will be lower that the pressure required to only move the bypass flow valve 35 into its second position (opening the radial flow passage 30 34), because the combined area of the second valve element 107 and the bypass flow valve 35 is larger than the area of the inner rim 115 of the bypass valve element 35.

As has been explained above, the filter element 21 needs to be periodically replaced and the filter head 22 and filter housing 23 can be separated. To avoid unwanted spilling of 35 fluid when separating the filter housing 23 and the filter head 22 when the filter element 21 needs to be replaced the valve assembly 100 is arranged to close the annular passage 31 14 such that any fluid remaining in the filter head 22 and/or in a conduit attached to the outlet port 45 is blocked from flowing out of the filter head 22. Hence, separating the filter housing 23 from the filter head 22 can be done without the risk of spilling fluid which is present downstream of the filter assembly 20. The condition in which the filter housing 23 and with it 5 the filter element 21 has been separated from the filter head 22 is denoted as no-element-condition and is shown in Figure 5E.

The no-element-condition is shown in Figure 5E, which condition mainly corresponds to the no-flow-condition as explained with reference to Figure 5A except that the end cap 10 assembly 26 is no longer present. As can be seen in Figure 5E the annular passage 31 is closed as the first valve element 105 and the second valve element 107 form a single or unitary valve under the influence of compression spring 111. The actual closing of the annular passage 31 is achieved by pushing the upper rim 110 of the first valve element 105 by means of the compression spring 108 onto an annular seal ring 118 which is fixedly 15 mounted to the wall section 52.

In the example of a filter head 22 shown in Figures 5A-5E, the inlet port 44 and the outlet port 45 are located on opposite sides of the filter head 22, or in other words, the inlet port 44 and the outlet port 45 are substantially co-axial. It is however also possible to 20 arrange the inlet port 44 and the outlet port 45 differently in the filter head 22, depending on for example the availability of space in a hydraulic system or a specific layout of flow lines. As an example it can be contemplated to arrange the inlet port 44 and the outlet port 45 on one side of the filter head 22, in particular the outlet port 45 may be arranged above the inlet port 44. This would mean, that the valve assembly 100 does not have to divert the flow 25 direction of the fluid flowing through the valve assembly 100, but the fluid follows a generally straight line through the valve assembly 100. This can be achieved, for example, by providing the valve housing (or cage) 101 with an open structure, e.g. by providing the valve housing 101 with axial flow passages.

30 To further improve the filter assembly according to the invention it is convenient that upon separation of the filter housing and the filter head, the filter element is detached from the filter head at the same time and remains in the filter housing, so that the filter can be replaced at a convenient location and/or to eliminate the risk of fluid coming out of the filter element while it is still attached to the filter head, i.e. dripping of the filter element while the 35 filter housing is gone to collect the dripping fluid. To achieve this further improvement a way 15 of detachably coupling the filter element to the filter housing is provided and explained in more detail with reference to Figure 6 and 7.

Figure 6 shows in an exploded spatial view part of the filter housing 23 and in 5 particular its bottom part. In the example of Figure 6 (and of Figure 1) the filter assembly is arranged to be connected to a conduit system while the filter assembly extends in a downward direction. For that reason the filter housing 23 is provided with a discharge opening 120 in the bottom part of the filter housing 23 that allows draining of the fluid from the filter housing 23. Normally the discharge opening 120 would be provided with a plug, 10 which is not shown in the drawing.

As mentioned above, the filter element comprises and end cap assembly 27 located opposite the end cap assembly 26 that comprises the bypass flow valve. In Figure 6 the end cap assembly 27 is shown without the filter element. Similarly to the design of the other 15 end cap assembly, the end cap assembly 27 comprises a generally U-shaped flange part 121 for attaching the filter element thereto. Further, the end cap assembly 27 comprises a tubular portion 122 which encloses the core element 38.

A coupling assembly 200 is provided in the filter housing 23 for detachably coupling 20 the filter element and/or the core element 38 to the filter housing 23. The coupling assembly 200 comprises a coupling member 201 which is preferably designed as a leaf spring, in particular a resilient lock ring 201, having a peripheral edge that closely corresponds to an inner surface of the filter housing 23. The leaf spring 201 comprises a number of radially extending resilient elements 202 contacting the inner surface of the filter housing 23 and 25 allowing a resilient deformation upon insertion of the leaf spring into the filter housing 23. The lock ring 201 has a concave cross-section that does allow introduction into the filter housing 23 because the resilient elements 202 can flex upward while pushing the lock ring 201 downward in Figure 6, but extraction will cause the lock ring 201 to bend in the opposite direction which urges the resilient elements 202 against the inner surface of the 30 filter housing 23, locking it in place. When the lock ring 201 is fully inserted into the filter housing 23, a number of support legs 205 support the lock ring 201. This is shown in more detail in Figure 7.

The coupling assembly 200 and in particular the lock ring 201 comprises a number 35 of grip members 203 or latches that can grip an intermediate coupling ring 204 that is part of the coupling assembly 200 and which comprises recesses 206 (see Figure 8) into which 16 the latches 203 can be inserted. The latches 203 are angled upwardly and are resilient, such that the intermediate coupling ring 204 and therewith the filter element and/or the core element 38 are biased in an upward direction in Figure 8. An alternative solution to bias the intermediate coupling ring 204 in an upward direction is shown with reference to Figure 9, 5 wherein a compression spring 220 is shown that is operable between the filter housing 23 and the intermediate coupling ring 204. Further, the intermediate coupling ring 204 can be provided with additional coupling means, such as coupling fingers 225 (see Figure 8) that extend through coupling openings 226 in the coupling member 201 However, other solutions for coupling the intermediate coupling ring 204 .

10

The intermediate coupling ring 204 has a peripheral wall portion 207 which extends in a longitudinal direction of the filter housing 23. The wall portion 207 has a guide surface 208 which lies in a plane which is non-perpendicular, i.e. angled, with respect to said longitudinal direction. The wall portion 207 comprises a recess 209 in that part that is 15 closest to the coupling member 201.

The guide surface 208 is designed to co-operate with a notch 210 provided on the end cap assembly 27 and extending radially outwards from the flange part 121. The notch 210, upon introduction of the filter element into the filter housing 23 will have an arbitrary 20 rotational position with respect to the intermediate coupling ring 204. To assure and simplify coupling of the end cap assembly 27 to the coupling ring 204, the notch 210 will be guided along the guide surface 208 until the notch 210 engages the recess 209. Furthermore, to ensure an even better coupling a further notch 211 provided on the end cap assembly 27 is provided to engage a further recess 212. This is also shown in Figure 8, wherein it is shown 25 how the coupling assembly 200 is coupled with the filter housing 23.

As can be further seen in Figures 6 and 8, the core element 38 is clamped between the annular portion 122 of the end cap assembly 27 and an upwardly directed flow guide means 213 provided on the coupling ring 204. The flow guide means 213 is arranged to 30 guide the fluid in an upward direction and reduces turbulence in the lower part of the filter assembly. It is noted that it is also possible to permanently couple the core element 38 to the coupling ring 204, such that it is not possible to discard the core element 38 by accident or on purpose such that pirated filter elements can be used.

35 Separation of the filter housing 23 from the filter head 22 with the embodiment shown in Figure 8 will result in the combined separation of the filter housing 23 and the filter 17 element as the filter element is (detachably) coupled with the filter housing. This thus results in a very clean way of removing the filter element as housing that encloses the filter element is the only part of the filter assembly that is physically handled.

5 The end cap assembly 27 and the intermediate coupling ring 204 are sealed against each other to assure that dirty or contaminant-loaded fluid cannot reach the clean side of the filter element. This is particularly true as the contaminant-loaded fluid is able to reach that part of the filter housing 23 that contains the discharge opening 120. For the conytaminant-loaded fluid to be able to reach the discharge opening 120, the peripheral 10 wall portion 207 is at its tallest part provided with flow passages 221. For the same reason the intermediate coupling ring 204 has an open structure to allow fluid to reach the discharge opening 120.The problem associated with the possibility that dirty fluid can reach the discharge opening 120 is, that in principle that fluid is able to squeeze between the end cap assembly 27 and the intermediate coupling ring 204 (out-to-in flow as shown in Figure 15 8, but the same is true for the in-to-out flow configuration). Hence, a seal is provided between the end cap assembly 27 and the intermediate coupling ring 204.

In the example of Figure 8 such a seal comprises an annular groove 222 in which an O-ring 223 is housed. The annular groove 222 is provided on an inner surface of the end 20 cap assembly 27. The annular groove 222 with the O-ring 223 seals against a peripheral rim 224 provided on an outer surface of the intermediate coupling ring 204. The peripheral rim 224 is also inclined with respect to the longitudinal axis H-H and the inclination of the annular groove 222 and the peripheral rim 224 correspond. One advantage of providing both the annular groove 222 and the peripheral rim 224 with the shown inclination is, that 25 when the filter element is placed in the housing 23 a smooth lead-in to create the O-ring seal is guaranteed. Another advantage is that it is not possible to use pirated filter elements in the filter assembly according to the invention. Such pirated filter elements will not have the proper inclined annular groove 222 and consequently as such pirated filter elements will not provide a proper seal and contaminated fluid will be able to flow from the contaminant-30 loaded side of the filter element towards the contaminant-free side of the filter element.

It is noted here that the arrangement of the inclined annular groove 222 comprising the O-ring 223 is not limited to the combination with an inclined guide surface 208. The inclined annular groove 222 requires the presence of an inclined peripheral rim 224 on the 35 intermediate coupling ring 204 that among others couples the core element 38, to make sure that only dedicated filter elements comprising an end cap assembly that is provide with 18 the inclined annular groove can be used in the filter assembly according to the invention. As explained earlier, the reason for not allowing non-dedicated filter elements is necessary to avoid possible problems with the performance of the filter assembly.

5 In an alternative embodiment shown in Figure 9, the annular groove 222 comprising the O-ring 223 is provided on an outer surface of the end cap assembly 27 and seals against an inner surface of the peripheral wall 204.

It is to be understood, that the manner of coupling the intermediate coupling ring 204 10 with the end cap assembly 27 is not limited to the examples shown. In particular, coupling arrangements not comprising the inclined guide surface 208 can also be used. However, the use of an inclined guide surface is advantageous, as this will always ensure a correct (radial) positioning of the end cap assembly 27 with respect to the intermediate coupling ring 204, which in turn ensures proper working of the seal between the end cap assembly 15 27 and the intermediate coupling ring 204. However, other means of establishing a coupling that achieve a proper coupling between the end cap assembly 27 and the intermediate coupling ring 204 are possible, such as a bayonet locking or the use of threading.

It is noted that the above Invention is not limited to the above-described examples of 20 filter assemblies. In particular it is noted that the invention is also applicable to filter assemblies which are used for filtering gaseous media in which particles are entrained. In such applications it is also relevant that when the filter element needs to be exchanged, that flow of the gaseous media is prohibited when separating the filter housing from the filter head. Furthermore, easy separation of the filter element from the filter head is also relevant 25 for gaseous media, as the filter may be contaminated with particles that are for example greasy. However, other reasons why the filter element should be removed from the filter head together with the filter housing are equally applicable.

It is further noted that the filter housing, filter element or other elements of the filter 30 assembly that have been described as having a circular or tubular cross-section, do not necessarily have to be circular or tubular. Any other convenient and suitable cross-section can be used, such as for example a non-circular filter element or non-circular filter housing.

Claims

1] A filter assembly, comprising: 5. a filter element; - a filter housing for accommodating the filter element; - an end cap assembly at a first end of the filter element, wherein the end cap comprises a tubular part which is open at its axial ends and which forms a first fluid flow passage with the filter element; 10. a filter head which is removably attachable to the filter housing and which comprises an inlet port, an outlet port and an annular passage in connection with the outlet port, the annular passage with the tubular part forming a second fluid flow passage; - a perforated core element which extends into the filter housing and substantially covers the inside of the filter element; characterized in that the filter assembly further comprises a coupling assembly provided in the filter housing for releasably coupling the filter element and / or the core element to the filter housing, the coupling assembly comprising said leaf spring, said leaf spring extending from a central portion of the leaf spring comprises radially extending resilient elements which contact the inner surface of the filter housing with their radial ends to allow resilient deformation upon insertion of the leaf spring into the filter housing such that the resilient elements on the one hand bend upwards when the central portion of the leaf spring enters downwardly into the filter housing and, on the other hand, are pressed with their radial ends against the inner surface of the filter housing when the central portion of the leaf spring is pulled upwardly from the filter housing.

Filter assembly as claimed in claim 1, wherein the leaf spring is a resilient washer with a peripheral edge adapted to grip an inside of the filter housing.

3. A filter assembly according to any one of the preceding claims, further comprising a valve assembly provided in the filter head and operable between the annular passage and the outlet port, the valve assembly comprising a valve that is axially displaceable in the valve assembly between a first position in which fluid can flow through the annular passage and a second position where flow through the annular passage is blocked.

Filter assembly according to any one of the preceding claims, wherein the central part of the leaf spring is provided with a number of support legs adapted to support the coupling assembly on a bottom part of the filter housing while leaving a gap between the leaf spring and the bottom part of the filter housing.

Filter assembly according to any one of the preceding claims, wherein the coupling assembly further comprises an intermediate coupling member adapted to be coupled on the one hand to the leaf spring and on the other hand to be releasably coupled to the further end cap of the filter element and / or the core element.

6. Filter assembly according to claim 5, wherein the intermediate coupling member has a circumferential wall part, which extends in a longitudinal direction of the filter housing, wherein the wall part has an inclined guide surface with respect to the longitudinal direction.

Filter assembly according to claim 6, wherein the wall part further has a notch in that part thereof which is closest to the coupling member and which is adapted to cooperate with a cam provided on the further end cap assembly.

A filter assembly according to any one of the preceding claims, wherein the further end cap assembly comprises an annular groove for accommodating a sealing member for sealing against the coupling assembly. 25

A filter assembly according to claim 8, wherein said annular groove is inclined with respect to the longitudinal direction.

Filter assembly according to any of claims 5 to 7, wherein the further end cap assembly comprises an annular groove for accommodating a sealing member for sealing against the intermediate coupling member. A filter assembly according to claim 10, wherein the intermediate coupling member comprises an inclined peripheral edge against which the sealing member seals. 12. A filter assembly according to any one of the preceding claims, wherein the coupling assembly comprises gripping means for gripping the further end cap assembly and / or the core element.