Patent Description:
<CIT> suggests a filter cartridge with a filter element between a front-end cap and a rear-end cap. The filter element forms a fluid channel which is protected against collapsing by a support structure inside the fluid channel. The front-end cap has a through hole enabling a fluid communication of the fluid channel with an inlet tube of a fluid filter socket. The filter cartridge enables a flow of an unfiltered fluid radially inwardly through the filter element, which is filtered while flowing through the filter element. The filtered fluid flows through the fluid channel and the through hole out of the filter cartridge. At the rear end facing side of the front-end cap is a cylindrical ring being unitary with the support structure and being aligned with the through hole and the filter element. Two pins protrude from the inner surface of the ring radially towards the ring axis. These two pins each have a forward-facing surface being both located in a first plane. Further, these two pins each have a rear-end cap facing surface being both located in a second plane. Both planes are perpendicular to the ring axis. The socket of the housing has a tube with a free distal end for being inserted into the ring of the filter cartridge. The rear-end cap facing end surface of the tube has two recesses. Between these recesses are helical surface portions configured to support a rotation of the filter cartridge around the tube axis until the pins engage into their respective recesses in the rear-end cap facing frontal surface of the tube.

<CIT> suggests a keyed filter cartridge being configured to be received by filter cartridge holder. The filter filter cartridge has a top portion with a peripheral surface protrusions being configured to engage in mating recesses of the filter cartridge holder.

<CIT> discloses a hollow filter element of a fluid filter. Associated to the filter element is retention/carrier device of a retention/carrier system retaining the filter element in a first housing section of a filter housing during installation and removal in or from a second housing section by rotation and insertion movement, respectively. The filter element-associated retention/carrier device has a retention/carrier part extending radially and circumferentially and has through holes adjacent thereto extending circumferentially so as to enable a filter housing-associated retention/carrier part of the retention/carrier system to pass through axially.

The problem to be solved by the invention is to provide a first article and a second article which are simple and hence cheap to manufacture while at the same time being configured to be mounted to each other in a predefined azimuthal orientation. Another problem to be solved is to provide a filter cartridge and a filter housing, as well being simple to manufacture and being configured to receive the filter cartridge in a predefined azimuthal orientation.

A solution of the problem is the first article as defined by claim <NUM>. Advantageous embodiments are subjects of the dependent claims. The first article has a first cylindrical surface and is hence a conduit like structure (conduit, for short). The first cylindrical surface of the conduit like structure may be a peripheral surface of the article, hence the conduit is not necessarily hollow, but it may be. Alternatively, the cylindrical surface may delimit a hollow space of the article, in this case, the conduit is hollow and may preferably have at least an open front end. The other end may be open or closed. In case the first surface delimits a hollow space, there are no restrictions to the shape of the peripheral surface, it can be designed to meet any requirement, be they technical and/or aesthetical. Thus, the term conduit or conduit like structure is a synonym for "a first article having a first cylindrical surface", in this sense the article resembles a straight conduit, and we use the term conduit only for simplicity and because it is more vivid than "a first article having a first cylindrical surface". In this sense "a/the conduit" may be considered as pars pro toto for "a/the first article having a first cylindrical surface", regardless of whether the surface a peripheral surface or faces towards a longitudinal axis of the conduit.

As will be explained in more detail below, the conduit of one of claims <NUM> to <NUM> may be mounted to a tube. The tube and/or the conduit may be integrated into and/or comprised by a filter cartridge of claim <NUM> or <NUM> and/or a filter housing of claim <NUM>. Like the term conduit can be replaced by "first article", throughout the entire description, the term tube can be replaced herein by "second article with a second cylindrical surface". In this sense, conduit and tube are each a pars pro toto of the respective superordinate terms. None of these is necessarily hollow or necessarily fluid tight or necessarily configured to enable a fluid flow, but as the usage of the terms conduit and tube implies, the conduit and/or tube may be.

The fluid filter cartridge may have a filter element forming a fluid channel with a longitudinal axis. These filter elements are well known and have of a porous material, enabling fluid molecules to pass the filter element, while particles above a given size are held back. These filter elements are widely used and commercially available, while often being made from plied filter paper. A front-end cap and a rear-end cap may be sealingly attached to a front side and to a rear side, respectively of the filter element. Fluid being filtered may thus pass between the front-end cap and the rear-end through the filter element, e.g. radial inward (from the outside into the fluid channel). Filtered fluid may leave the fluid channel via a at least one through hole in the front-end cap and/or the rear end cap.

In an example, the conduit may have a conduit wall with the first cylindrical surface enclosing a through hole of the conduit. The conduit wall may be attached for example to the front-end cap and may be in fluid communication with the fluid channel via the through hole in the front-end cap. Hence, the conduit may have a front end facing away from the rear-end cap and the rear end of the conduit may face towards the rear-end cap. Filtered oil (being an example fluid herein) may thus flow from the fluid channel through the through hole of the conduit to wherever it is needed.

The conduit has a number of n pins attached to it, n being an integer, e.g. greater that <NUM> and/or greater than <NUM> and/or greater than <NUM> and/or greater than <NUM>, and/or greater than <NUM>. These n-pins may each extend from an inner surface of the conduit wall towards the conduit axis and/or from the outer peripheral surface of the conduit wall away from the conduit axis. Each of the pins spans an azimuthal angle <MAT>, as well referred to herein as azimuthal span <MAT>, wherein the index i identifies the pins, i.e. <NUM> ≤ i ≤ n. For example, <MAT> is the azimuthal span of the first pin, <MAT> is the azimuthal span of the second pin and so forth. Generalizing, <MAT> denotes the azimuthal span of the ith pin.

The azimuthal span <MAT> can be considered as an azimuthal extension. In other words, a rotation of the conduit by an azimuthal span <MAT> around the conduits longitudinal axis shifts a first azimuthal boundary of a pin i to the azimuthal position of the other azimuthal boundary of the same pin i prior to the rotation. Thus prior to the rotation, each ith pin extends ('spans') in azimuthal direction from a first azimuthal position ϕi to a second azimuthal position <MAT>. Again, it is noted that the index i indicates the number of the corresponding pin, i.e., <NUM> ≤ i ≤ n. Herein, we assume that the pins are numbered in an ascending order in the azimuthal direction. Hence the ith-pin is an azimuthal neighbor of the (i + <NUM>)th-pin for all <NUM> ≤ i < n and the nth-pin is an azimuthal neighbor of the first (i = <NUM>) pin (and of course of the (n - <NUM>)th pin). The azimuthal distance between two pins i, i' is referred to as <MAT>. Accordingly, the azimuthal position ϕi+<NUM> of the (i + <NUM>)th-pin is given by <MAT>, ∀<NUM> ≤ i < n-<NUM>. It comes without saying that the azimuthal position ϕ<NUM> of the first pin is ϕ<NUM> = <MAT>. Of course, once per turn, one has to subtract <NUM>° = <NUM>π, i.e. assuming ϕ<NUM> = <NUM>°, then <MAT>.

As usual in the field of mechanical engineering, the azimuthal distance is the distance between two points in azimuthal direction which can be determined easily as the difference of the azimuthal component of their coordinates (assuming cylinder coordinates).

In a preferred example <MAT>, ∀<NUM> ≤ i ≤ n, a being a constant and αa is an error margin selected from the set A, with A = {<NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>}, i.e. αa ∈ A, αa is preferably small, particularly preferred αa = <NUM>. In addition or alternatively, <MAT> b, ∀<NUM> ≤ i < n, b being a constant, αb ∈ A, preferably αb ≤ <NUM>, particularly preferred αb = <NUM>. Again, as usual in the field of mechanical engineering x = y ± δ is a short form for |y| - | δ| ≤ |x| ≤ |y| + |δ| and hence <MAT> means <MAT>, or in other words within a relative error margin of ±ab, <MAT> equals b, so to speak <MAT>.

Particularly preferred are the azimuthal spans and the azimuthal distances of at least approximately the same size, hence preferably <MAT> <MAT> and αϕ ∈ A, wherein smaller αϕ are preferred.

The n pins each have a forward facing surface, i.e. a surface facing away from the rear-end cap. Preferably, the distances di in axial direction between the forward facing surfaces and a reference plane either increase or decrease with the respective azimuthal position ϕi of each ith-pin by Δdi-<NUM>,i from the (i - <NUM>)th-pin to each ith-pin for all <NUM> < i ≤ n, thus, di+<NUM> = di + (<NUM> ± αd) · Δdi,i+<NUM> , Δdi,i+<NUM> ≠ <NUM>, ∀<NUM> ≤ i < n and αd ∈ A wherein Δdi: = Δdi-<NUM>,i ∀<NUM> < i ≤ n and Δd<NUM>: = Δdn,<NUM>. An increase of the axial distances di implies that Δdi,i+<NUM> > <NUM>, ∀<NUM> ≤ i < n and correspondingly a decrease Δdi,i+<NUM> < <NUM>, ∀<NUM> ≤ i < n. Thus, the distance di strictly monotonically increases or decrease as a function of the azimuthal position ϕi. Only to allow simple referencing and to explain the concept Δdi,i, is the distance between the front facing surfaces of the ith pin and the i'th pin, where <NUM> < i ≤ n and <NUM> < i' ≤ n, i.e. Δdi,i = <NUM> ∀i. The distance Δdn,<NUM> in axial direction between the front facing surface of the nth-pin to the front facing surface of the first pin is preferably given by <MAT>, αdn ∈ A, wherein smaller αdn are preferred.

The reference plane is perpendicular to the longitudinal axis and preferably either at the front or at rear side of all n pins. The axial position of the reference plane is selected only for conceptual simplicity. Generally, the reference plane could as well be in between of the first and the nth-pin, but then the meaning of the signs indicating the direction of the distances di and the axial shift Δdi,i+<NUM> alters when transitioning the reference plane). As already apparent, αdn is an error margin and an element that can be selected from A = {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM> }, i.e. α ∈ A. The symbol " ± " denotes as usual that Δd<NUM> is in between <MAT> and <MAT>, thus <MAT>. This axial shift Δdi has the effect that the filter cartridge can be rotated relative to a tube extending at least partially in the conduit or in which the conduit at least partially extends while being shifted in the forward direction until the first or the nth-pin (depending on the sign of Δdn) abuts in azimuthal direction against a protrusion on the peripheral surface and/or on the inner surface, respectively of the tube. However, a rotation in the opposite direction is blocked. Thus, when mounting the tube and conduit by inserting one into the other, these can be rotated towards an intended azimuthal orientation, but not in the opposite direction. Installation of parts requiring a predefined azimuthal orientation, like for example a filter cartridge is simplified. In the example of a filter cartridge having a front-end cap with the conduit, manufacturing of the conduit and thus of the front-end cap is vastly simplified because the front-end cap including the conduit can be manufactured by injection molding while obliviating the need for additional sliders in the mold. Further, installation of the filter cartridge is fail safe as the filter cartridge, if not rotated to the intended position, prevents the filter housing from being fully closed.

As already apparent from the above, the pins and the protrusions preferably extend at least essentially into opposite directions from opposed surfaces of the conduit and the tube towards their respective counterpart, if the tube is at least partially inserted into the conduit or the conduit is at least partially inserted into the tube. For example, if the conduit is configured to receive the tube, the pins may extend at least essentially radially inwards from the inner surface of the conduit wall. In another example the conduit may be configured to be received at least partially by the tube and in this another example, the pins may extend at least essentially radially outwards from the peripheral surface of the conduit wall. Similarly, if the tube is configured to receive at least a portion of the conduit, the protrusions extend preferably from the inner side of the tube wall at least essentially towards tube axis. If the tube is configured to be received at least partially by the conduit, the protrusions are preferably on the peripheral surface of the tube and extend at least essentially radially outwards.

In a preferred example, the azimuthal distance <MAT> between the nth-pin and the first pin is greater (>) than the maximum azimuthal distance <MAT> between any other pair of neighbored pins i, i + <NUM>, <NUM> ≤ i < n. Thus <MAT> <MAT>. Thereby, it can be assured that the conduit can be further advanced towards the tube only in the intended azimuthal orientation. This is further enhanced, if the optional complementary protrusion blocking the further rotation has an azimuthal span <MAT> being greater than <MAT> and smaller <MAT>. During the rotation, the pins may so to speak slide over the read-end cap facing surface of the protrusion, assuming the conduit is attached to or integrated in a front end cap.

If at least a portion of the front-end facing surfaces of the pins are inclined in the azimuthal direction this sliding is enhanced. The inclination preferably has as a slope <MAT>, ∀ <NUM> < i ≤ n wherein αs ∈ A, particularly preferred is αs = <NUM>.

As already apparent, the pins have side surfaces facing in the two opposed azimuthal directions. Preferably, the first pin and the nth-pin each have an azimuthal abutment wherein the two abutments face towards each other. These abutments can for example be formed by at least a portion of the opposed side surfaces of two respective pins. These abutments enable to center a protrusion with an azimuthal span smaller or equal than the azimuthal distance between the two pins, being explained below in more detail. The protrusion may, e.g. be located on a peripheral surface of a tube configured to be inserted into the conduit as explained above.

In a preferred example, the axial distances Δdi between the ith- and the (i + <NUM>)th-pin may be at least essentially constant (within a relative error margin αc, αc ∈ A ) for all pins except of course for the distance between the last (nth-) pin to the first (i = <NUM>) pin. In a more concise manner one may reformulate this as Δdi = (<NUM> ± αc) · cd, ∀<NUM> ≤ i < n, cd being a constant.

Another aspect of the invention is a tube of a filter socket to which a filter cartridge, e.g. a filter cartridge with at least one of the above described features may be attached to. In practice these filter sockets are often a part of a filter housing, and they may even be integrated in a filter housing for a filter cartridge, in particular for a filter cartridge as described above.

The filter housing has a housing bottom and a housing cover. The housing cover is preferably removably attached to the bottom. The housing cover and the housing bottom enclose a space configure to receive the filter cartridge. In practice, one may open the filter housing, may (if present) remove a previously inserted filter cartridge, insert another or the same filter cartridge and close the housing cover again. As indicated, the removing step is optional, for example, it is necessarily omitted if the filter housing is already empty.

The filter socket may be located inside the filter housing and may have a tube with a free end. The tube has a peripheral surface and a fluid opening configured for receiving fluid from the filter cartridge. Of course, the fluid flow may be reversed. Herein, only for a more vivid presentation we assume the fluid to flow through the filter element into the fluid channel and from there into fluid inlet of the tube. If the fluid flow is reversed, the fluid inlet becomes a fluid outlet, hence the term "fluid inlet" is only a vivid example of the term "fluid opening", the latter term leaving the flow direction open. The tube has a tube axis and at least a first protrusion extending from the peripheral surface in an outward direction or from an inner surface at least essentially towards the tube axis. As already apparent from the above, the tube can as well be used in other applications and the described integration into a filter housing is only an example for a practical application of the invention.

The first protrusion may have an azimuthal span <MAT> and a rear end of the corresponding conduit facing surface. In a preferred example, the azimuthal span <MAT> is greater or equal (≥) than the azimuthal distance <MAT> between the pins of the conduit for all i + <NUM> ≤ n and in that the azimuthal span <MAT> is smaller (or equal) than (or to) the azimuthal distance between the nth- and the first pin, i.e., <MAT>. Accordingly, the first protrusion fits only in the azimuthal spacing between of the nth-pin and the first pin of the conduit. The axial dimension of the protrusion is preferably configured to abut the two mutually opposing azimuthal surfaces of the nth-pin and the first pin. Hence, the axial dimension l<NUM>of the first protrusion (as well referred to as the first length l<NUM>) is preferably in the order of |Δdn,<NUM>|, wherein in the order of may be understood as (<NUM> - αl ) · |Δdn,<NUM>| ≤ l<NUM> ≤ (<NUM> + αa ) · |Δdn,<NUM>| or briefly l<NUM> = (<NUM> ± αl) · |Δdn,<NUM> | wherein αl ∈A.

In a particularly preferred example, the first length l<NUM> is greater than |Δdn,<NUM> | minus the axial length of the first pin or of the nth-pin, depending on which of these is further away from the rear-end, i.e. minus the axial length of those of these two pins being farther to the rear end cap. If lf is the axial length of that pin of these two pins being farther from the rear end, than l<NUM> obeys preferably l<NUM> > |Δdn,<NUM> I - lf or preferably at least l<NUM> ≥ |Δdn,<NUM> I - lf.

Preferably, tube has a number of m - <NUM> further protrusions, which protrude from the peripheral surface of the tube and/or from the inner surface of the tube, wherein each of the protrusions has a set of associated azimuthal angles <MAT> and in that <MAT>, ∀<NUM> ≤ i < n, <NUM> ≤ j ≤ m, if the tube axis and the conduit axis are aligned and if the tube and the conduit are oriented to obey the condition <MAT>. In other words, there a number of m protrusions, if the first protrusion is counted as well and the azimuthal spans <MAT> of each of these protrusions as well as their locations φj are selected to ensure that the cartridge can be advances if (and only if) the space between the nth-pin and the first pin is azimuthally positioned to match the azimuthal position of the first protrusion. The ranges βj over which the protrusions span can be considered as a code which has to be matched by the azimuthal positions and azimuthal spans of the pins. As already apparent, the index j indicates the jth protrusion to which the value (range, position span, etc.) is associated.

Particularly preferred, the distally facing surfaces of the protrusions, i.e. the surfaces facing towards the rear-end of the conduit (if the tube is mounted) each have a distance δj from the position of the reference plane and a slope of the protrusions st, with <MAT> is at least essentially (i.e. with a percentage αst ∈ A ) the slope sc of the pins of the conduit, being sc = <MAT>, ∀i > i', <NUM> ≤ i ≤ n, or briefly (<NUM> ± αst) · sp = sc.

There may be a second reference plane being orthogonal to the tube axis. Thus, if the conduit and/or the filter cartridge is attached to the tube and/or the socket, the first and the second reference planes may be oriented at least essentially parallel to each other (which shall include that both planes become identical in case the filter cartridge reaches its axial end position). At least essentially parallel means that parallelism is preferred, but small deviations can be accepted, e.g. deviations smaller than <NUM>°, smaller than <NUM>°, smaller than <NUM>°, smaller than <NUM>° or deviations smaller than <NUM>° may be accepted.

Particularly preferred, the axial positions of the distally facing surfaces of the protrusions are spaced from each other such that at least two distally facing surfaces each abut at least a front facing surface of a pin, if the condition ϕn + Δϕn ≤ β<NUM> ≤ ϕ<NUM> is not met. Thereby, during adjustment of the azimuthal orientation of the filter cartridge, the longitudinal axis of the conduit may be at least essentially aligned to the tube axis, thereby reducing the risk that the pins and the protrusions are jammed, which may result in blocking the filter cartridge from being properly oriented and/or axially advanced towards its intended position.

As already apparent, the filter housing and the filter cartridge may be combined to form a liquid filter system. The corresponding method may comprise at least one of the following steps.

Subsequently one may close the housing cover. Prior to the inserting step one may, if required remove or open the housing cover and remove an already installed filter cartridge, if one is installed.

Once a further rotation of the cartridge is blocked one may push the cartridge axially until the cartridge abuts an axial block.

Above, the invention has been described assuming that the pins are on a surface of the conduit and that the protrusions are on a surface of the tube. But the pins could as well be on surface of the tube and the protrusions on a pin facing surface of the conduit. The interaction of the pins and the protrusions would not be altered. The terms first surface of the conduit and second surface of the tube have only be chosen to be able to verbally distinguish these preferably cylindrical surfaces.

A cylindrical surface is as usual a surface resembling a cylinder surface. Generally, one may say that a cylindrical surface is at least in part congruent to at least a part of a cylinder surface. Further, it is noted that it is preferred but not required that cylindrical surfaces herein are circular cylindrical surfaces, i.e. at least a portion of the respective circular cylindrical surface is congruent to at least a part of a circular cylinder surface. For a commonly accepted definition of a cylinder, please see<NPL>).

In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

The filter cartridge <NUM> in <FIG> comprises a filter element <NUM> enclosing a fluid channel <NUM> having a longitudinal axis <NUM>. Herein this longitudinal axis is considered as the filter axis <NUM>. The filter element <NUM> can be for example of plied filter paper as commonly used, e.g. for oil filter cartridges or any other suitable filter material. The filter element <NUM> has e rear end side, which is attached to the forward-facing surface of a rear end cap <NUM>. The frontal side of the rear-end cap <NUM> facing away from the front-end side is hence referred to as rearward facing side <NUM> of the rear-end cap <NUM>. In this example, the rear-end cap <NUM> is represented by a simple disk, but it may as well have through holes, valves, attachment means or the like as known in the art. The front-end side of the filter element <NUM> is attached to a rearward facing side <NUM> of a front-end cap <NUM>. The front-end cap <NUM> has a through hole <NUM> enabling filtered fluid to leave the fluid channel <NUM>. A conduit <NUM> being defined by a conduit wall <NUM> is attached to the front-end cap <NUM> and encircles the through hole <NUM>. In other words, the inner surface of the conduit <NUM> defines the through hole <NUM>. Similar to the front-end cap <NUM>, the conduit <NUM> has a front facing surface <NUM> and a rearward facing surface <NUM>.

At this point it is noted that in this example the tube axis <NUM> and the filter axis <NUM> coincide, but this not necessarily the case as explained in detail in <CIT> and in the depicted example this alignment has been chosen only because of its conceptual simplicity.

A number of n pins <NUM><NUM>, <NUM><NUM>, <NUM><NUM>,. , <NUM>n may protrude from the inner surface <NUM> of the conduit wall <NUM> into the free space being enclosed by the conduit wall <NUM> (see as well <FIG> and <FIG>). Each pin <NUM>i (<NUM> ≤ i ≤ n) has a forward-facing surface <NUM>i and at its opposite side a rear-end facing surface <NUM>i. As shown, the front end facing surfaces <NUM>i, <NUM>i+<NUM> of two neighbored pins <NUM>i and <NUM>i+<NUM> (∀<NUM> ≤ i < n) are spaced from each other by a distance Δdi (see <FIG>). Thus, relative to a reference plane <NUM>, the distances di of the front facing surfaces <NUM>idecrease with increasing index i. Generally, the reference plane may be placed on the other side of the pins <NUM>i, in this case the distances di would increase. The position of the reference plane is not relevant, but regardless of the choice, the distances should all increase or all decrease when increasing i from <NUM> to n, assuming the first pin to be either the one closest to the front end or the closest to the rear end of the conduit.

In addition, the pins <NUM>i are azimuthally spaced as can bee seen in <FIG> and <FIG> the conduit <NUM> from the front and aligned with the longitudinal axis <NUM>. ϕ<NUM> is the angle at which the first protrusion (i = <NUM>) starts. The first protrusion <NUM><NUM> then extends or spans azimuthally by a 'span' <MAT>. After an azimuthal distance <MAT> the next pin <NUM><NUM> protrudes out of the inner surface <NUM> or the conduit wall <NUM>, i.e. at an angle ϕ<NUM>. Generalizing, at each azimuthal position ϕi extends a pin <NUM>i having an azimuthal thickness ('span') <MAT>. In this example in the clockwise direction, this pin <NUM>i is followed by a pin20i+<NUM>(, but of course the direction could be inverted) and the azimuthal spacing (the azimuthal gap) between the ith-pin <NUM>i and its subsequent (i + <NUM>)st-pin <NUM>i+<NUM> is the gap <MAT>, hence the (i + <NUM>)st-pin 'starts' (or ends, depending on the preferential direction) at ϕi+<NUM> = ϕi + <MAT>, ∀<NUM> ≤ i < n. As can be seen in <FIG>, <MAT> is much bigger than all <MAT>. Preferably, <MAT>. This azimuthal gap <MAT> between the nth- pin <NUM>n and the first pin <NUM><NUM> ensures that when inserting the conduit (which may be a part of a filter cartridge <NUM>) it may slide with the front facing surfaces <NUM>i on any protrusion having an azimuthal span <MAT> greater than <MAT> and preferably smaller than the gap <MAT>, thereby being guided into a defined azimuthal orientation. Preferably, the protrusion <NUM><NUM> (see <FIG>) has an axial span <MAT> greater than the axial distance <MAT> between the first and the nth-pin <NUM>n and the first pin <NUM><NUM> and/or has an azimuthal abutment closing the axial gap between the first pin <NUM><NUM> and the nth-pin <NUM>n. The abutment may be a separate part, only for conceptual simplicity, we attributed the abutment to the first pin, as the abutment delimits a rotation in the direction from ϕn to ϕi beyond ϕi.

This mechanism of azimuthally orienting the conduit <NUM> and hence any part comprising the conduit (e.g., the filter cartridge <NUM> of <FIG>) relative to the tube <NUM> another part is visualized in <FIG>: In <FIG> there is the tube <NUM> having a tube axis <NUM> being aligned with conduit axis <NUM>. The tube <NUM> has a peripheral surface <NUM> with a radius smaller or equal to the free radiuses ri of the conduit <NUM>. Thus, when inserting the tube <NUM> into the conduit <NUM>, the tube <NUM> has a rearward facing side <NUM> and is at least approximately centered in the conduit <NUM> by the radially inwardly facing surfaces of the pins <NUM>i. In <FIG> only the pins <NUM>i of the conduit are depicted to visualize their interaction with protrusions <NUM>j extending radially outwardly over the free radius ri of the conduit from the peripheral surface of the tube <NUM>.

<FIG> shows a situation, when a conduit <NUM> (which may be a part of a filter cartridge <NUM>) with the pins <NUM>i extending into the through hole <NUM> is positioned over the tube <NUM>, which may be part of a socket of a filter housing. As shown in <FIG>, the conduit <NUM> may be advanced in the forward direction <NUM> (see arrow in <FIG>) until the at least one front-end side <NUM>i of a pin <NUM>i, i.e. the forward facing surface <NUM>i of a pin <NUM>i, abuts the rear end facing side <NUM>j of an jth-protrusion <NUM>jhaving an azimuthal span <MAT> being greater than <MAT> i < n}). In the depicted example, by chance, an axial movement of the conduit <NUM> in the forward direction is blocked by the rear end facing side <NUM><NUM> of the first protrusion <NUM><NUM> abutting the forward-facing surface <NUM><NUM> of the first pin <NUM><NUM>. While applying a slight force in the forward direction <NUM>, one may rotate the filter conduit <NUM> relative to the tube <NUM> in the direction being indicated by a bent arrow. As can be seen in <FIG>, the pins <NUM>i slide over the first protrusion <NUM><NUM>. After a given rotation, the forward-facing side of the first pin <NUM><NUM> may slides on the rear-end facing side <NUM><NUM> of an optional second protrusion <NUM><NUM>. In this preferred example, the second protrusion <NUM><NUM> optionally has an axial offset corresponding to the slope <MAT> of the pins <NUM>i, Further, if optional protrusions <NUM>jare positioned accordingly (, as shown in <FIG> as protrusions <NUM><NUM>,<NUM><NUM>), the front facing sides <NUM>i of the pins <NUM>i, may slide on or over the rear-end facing surfaces <NUM>j of the protrusions <NUM>j.

The conduit <NUM> may slide on the protrusions <NUM>j, until a side face of the first pin <NUM><NUM> abuts a side face of the first protrusion <NUM><NUM>. So to speak, the sides faces mutually limit a further rotation of the conduit as depicted in <FIG>.

Claim 1:
A conduit (<NUM>) for a fluid filter cartridge and/or a filter cartridge housing, wherein the conduit (<NUM>) has a first cylindrical surface (<NUM>, <NUM>) defining a first longitudinal axis (<NUM>), wherein
- the first cylindrical surface (<NUM>, <NUM>) has a front end and a rear end,
- a natural number of n pins (<NUM>i, <NUM> ≤ i ≤ n) extends from the first cylindrical surface (<NUM>, <NUM>) at azimuthal positions ϕi, to <MAT>, ∀ i E {<NUM>, <NUM>, ... , n}, wherein <MAT> is the azimuthal span of the ith-pin (<NUM>i)
- each pin (<NUM>i) has a forward-facing surface (<NUM>i), facing away from the rear-end,
- the ith-pin (<NUM>i) and the (i + <NUM>) th-pin (<NUM>i+<NUM>) are spaced from each other in the azimuthal direction by a distance <MAT> ∀i ≤ n - <NUM> and wherein the nth-pin (<NUM>n) is azimuthally neighbored to the first pin (<NUM><NUM>), and,
characterized in that
distances (di) between the forward facing surfaces (<NUM>i) and a reference plane (<NUM>) increase or decrease with the respective azimuthal positions (ϕi) of the ith-pin (<NUM>i) by a change in distance Δdi,i+<NUM> from the first pin (<NUM><NUM>) towards the nth-pin (<NUM>n) and by a value of <MAT> from the nth-pin (<NUM>n) to the first pin (<NUM><NUM>), wherein the reference plane (<NUM>) is perpendicular to the first longitudinal axis (<NUM>) and either at the front or at rear side of all n pins (<NUM>i) and α ∈ {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM> } and in that the absolute value of the azimuthal distance ( <MAT> ) between the nth-pin (<NUM>n) and the first pin (<NUM><NUM>) is greater or equal than the maximum azimuthal distance ( <MAT> ) of any other pair of neighbored pins (<NUM>i, <NUM>i+<NUM>), i.e. <MAT> i < n}).