Abstract:
The present invention relates to an air dryer cartridge designated for an air dryer of a utility vehicle. The air dryer cartridge comprises a supporting element. At least one spring is interposed between a supporting element and a pressing element for a desiccant. The supporting element is movable with respect to a housing of the air dryer cartridge. The supporting element is freely accessible from the outside of said air dryer cartridge. The present invention in particular provides the option to use the at least one spring both for pressing the desiccant as well as for clamping the air dryer cartridge in an air dryer.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to co-pending German Patent Application No. DE 10 2011 054 329.5 entitled “Lufttrocknungskartusche”, filed Oct. 10, 2011. 
       FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to an air dryer cartridge designated for an air dryer of a utility vehicle. Furthermore, the invention relates to an air dryer for a compressed air system of a utility vehicle, wherein the air dryer is equipped with an air dryer cartridge. 
         [0003]    In pressurized air systems of utility vehicles, air dryer cartridges are used for processing the pressurized air. Usually, the air dryer cartridge is located between a pressurized air source (in particular a compressor and/or a reservoir) and at least one consumer circuit of the utility vehicle. The air dryer cartridge is used for cleaning and drying the pressurized air. This is done by use of at least one filter and/or at least one desiccant wherein the pressurized air is cleaned and dried by streaming through the filter and/or the desiccant. 
       BACKGROUND OF THE INVENTION 
       [0004]    DE 699 08 918 T2 discloses an air dryer wherein the air dryer cartridge is housed in a housing of the air dryer. The housing of the air dryer is built with two housing parts, namely a base element and a top cover element. The top cover element is in a first approximation bell-shaped comprising a side wall in the shape of a hollow cylinder and a dome-shaped top cover wall. The base element is assembled with the top cover element. In the assembled state the base element and the top cover element define a housing with a closed inner chamber being cylindrical with a dome-shaped arching at the top. The air dryer cartridge is located in the inner chamber. The air dryer cartridge comprises a housing which is generally closed but comprises passages, openings or ports for building inlets and outlets for the stream of pressurized air. The air dryer cartridge is housed with a minimal resulting radial gap with respect to the hollow cylindrical side wall of the top cover element. In a radial outer edge region a ring-shaped sealing element is interposed between the top wall of the top cover element of the air dryer and the air dryer cartridge. The sealing element comprises an oversize such that the cartridge and the sealing element are clamped between the base element and the top cover element for fixing the air dryer cartridge. 
         [0005]    An air dryer cartridge according to DE 699 08 918 T2 builds two chambers, wherein one chamber is located radially inside from the other chamber. In the radial outer hollow cylindrical ring chamber, a desiccant and/or a filter is/are located. The outer chamber is separated by a hollow cylindrical intermediate wall from a radial inner cylindrical chamber wherein (another) desiccant is housed. During a load phase of the air dryer, pressurized air streams from an inlet chamber of the base element through passages of a base wall of the air dryer cartridge into the ring chamber. Within the ring chamber, the pressurized air streams parallel to a longitudinal axis of the air dryer cartridge to the top cover region of the air dryer cartridge. In the top cover region of the air dryer cartridge the pressurized air is transferred via an air-permeable textile material and an air-permeable top wall of the air dryer cartridge into an intermediate chamber. The intermediate chamber is build between the top wall of the air dryer cartridge and the top wall of the top cover element of the air dryer. The pressurized air streams from the intermediate chamber through the air-permeable top wall of the air dryer cartridge and through the air-permeable textile material into the radial inner cylindrical chamber. In this chamber the air streams with an orientation parallel to the longitudinal axis towards the base element. The pressurized air is then fed by air passages in the base region of the air dryer cartridge and an outlet chamber of the base element to the pressurized air system, in particular to the consumer circuits. Collected humidity and/or impurities are removed from the desiccant, the filters and the collecting chambers by use of reversed cleaned pressurized air in a regeneration phase of the air dryer cartridge. 
         [0006]    In order to fix the particles of the desiccant in the chambers, in order to compact the desiccant and/or in order to apply a pressing force to the desiccant, the air dryer cartridge of DE 699 08 918 T2 comprises separate pressing elements for each chambers. The pressing elements are (similar to pistons) axially displaceable in the chamber. On the side opposite to the desiccant the pressing elements are supported by springs. These springs bias the pressing element and the desiccant with a predefined pressing force. One base of the springs is supported at the pressing element, whereas the other base of the springs is supported by a supporting element. According to DE 699 08 918 T2, this supporting element is built by a fixed base wall of the air dryer cartridge. 
         [0007]    Air dryer cartridges with a supporting element for supporting a spring biasing the desiccant are also known from U.S. Pat. No. 4,673,419 A, U.S. Pat. No. 5,002,593 A and EP 0 137 909 B1. For these embodiments the supporting element is built by a top cover element building a fixed part of the housing. 
         [0008]    Furthermore, so-called spin-on-cartridges are known. These types of cartridges are not clamped by a spring element between a base element and a top cover element of the air dryer. Instead, for these embodiments the air dryer cartridges comprise a solid and massy base wall with a central bore having an inner thread. The base wall is with its inner thread screwed on a connecting socket of the base element of the air dryer. The connecting socket at the same time serves as an inlet and/or outlet port for pressurized air to and/or from the air dryer cartridge. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention relates to an air dryer cartridge and an air dryer with a modified design. It is in particular an object of the present invention to improve
       the design of an air dryer cartridge with respect to the manufacturing costs,   the options for and the procedure of an exchange of the desiccant,   the conditions of the desiccant during the storage of the air dryer cartridge,   the consumption of material an/or energy and/or   the way of fixing the air dryer cartridge in an air dryer.       
 
         [0015]    One embodiment of the invention relates to an improved fixing of the air dryer cartridge in the air dryer. Furthermore, the invention relates to the force transfer of the pressing forces of the desiccant in the air dryer cartridge (on the one hand side during stock holding of the air dryer cartridge and on the other hand side during the operation of the air dryer cartridge in the air dryer). 
         [0016]    One inventive embodiment provides an air dryer cartridge wherein the supporting element is (freely) accessible from the outside of the air dryer cartridge. Accordingly, the supporting element is at least partially not covered by a fixed wall of the housing of the air dryer cartridge. Due to the fact that the supporting element is accessible from outside, it is possible to apply outer forces and/or to change a position of the supporting element from the outside of the air dryer cartridge. These measures can be taken manually by the user and/or might be taken automatically during the assembly of the air dryer cartridge with the air dryer. This embodiment of the invention covers a one-piece supporting element (e.g. a supporting plate) or a supporting element built with a plurality of linked parts. To name only some non-limiting examples, the supporting element might be built with a type of supporting plate with a protrusion, a pin, plug, collar and/or connecting element or drive element which is freely accessible from the outside. Another option is that a protrusion, pin, bold, collar, connecting element or drive element and the like extends through an opening of the housing of the air dryer cartridge to the outside of the housing for providing the free accessibility (here the other part of the supporting element is not necessarily freely accessible). 
         [0017]    The free access to the supporting element might lead to the following advantages which are only mentioned by way of examples:
       It is possible that before, during or after the use of the air dryer cartridge in an air dryer the supporting element is manipulated from the outside, in particular for temporarily or permanently influencing the pressing of the desiccant.   Furthermore, it is possible that an opening which is used for the accessibility to the supporting element is used for disassembling the supporting element. In subsequent steps of dissembling, also a pressing element and/or a spring might be removed. In this state it is possible to exchange an exhausted desiccant with a fresh desiccant with the subsequent re-assembly of the pressing element, the spring and the supporting element. Accordingly, an exchange of the desiccant is possible, wherein a lot of components of the air dryer cartridge (e.g. the housing) might be used also for the reconditioned air dryer cartridge.   By providing the housing of the air dryer cartridge with an opening for providing the accessibility of the supporting element, it is possible to build the housing with a decreased overall surface, decreased weight and/or decreased material volume.       
 
         [0021]    For another (alternative or cumulative) embodiment of the invention, the supporting element does not (exclusively) support at the housing of the air dryer cartridge (in particular at the hollow cylindrical side wall). Instead, for this embodiment the pressing element and the supporting element are located in the top region of the air dryer cartridge. The supporting element is held at a base wall of the air dryer cartridge which is accomplished by an anchor element extending through the air dryer cartridge. By use of the anchor element, it is possible to keep the side walls of the housing of the air dryer cartridge free from holding forces for the supporting element. This leads to an increased resistance and/or decreased required wall thicknesses of the side walls. Within the frame of the present invention it might also be possible to use a plastic material for the side wall and/or for the housing of the air dryer cartridge. On the other hand, the anchor element extending through the air dryer cartridge might reduce the lever arm and the resulting bending moment caused by the pressing force which is transferred to the base region. For one embodiment of the invention, the anchor element is located centrally and has an orientation coaxial to the longitudinal axis of the air dryer cartridge. This embodiment leads to a minimized bias with a bending moment. By means of the above measures, the massive design of the base element of the housing of the air dryer cartridge might be reduced and/or the use of a plastic material is possible for the base element. Embodiments using a type of anchor extending through the air dryer cartridge might generally also be used for a closed housing according to DE 699 08 918 T2. For this modification of DE 699 08 918 T2 the sealing element no longer needs to be used for fixing the air dryer cartridge in the air dryer. For another embodiment of the invention, it is possible to use the above described anchor element in connection with an air dryer cartridge wherein the supporting element is freely accessible from the outside of the air dryer cartridge. 
         [0022]    Generally, any design of the housing of the air dryer cartridge might be used for providing the free accessibility of the supporting element and for the construction, design and configuration of
       the supporting element,   the at least one spring and   the pressing element.       
 
         [0026]    For one embodiment of the invention, a housing of the air dryer cartridge is built with an opening to an inner chamber of the air dryer cartridge. In the inner chamber the desiccant is housed. The supporting element at least partially closes the opening of the housing. To mention one non-limiting example, the housing of the air dryer cartridge might be built with a hollow cylindrical side wall with a circular opening in the top end region. In a rough approximation a “piston-like” pressing element enters into the hollow cylindrical side wall for pressing the desiccant. In case of a plate-like pressing element, a plate-like supporting element might be positioned parallel to the pressing element, wherein the at least one spring is interposed between the pressing element and the supporting element. 
         [0027]    The supporting element might be located within the hollow cylindrical side wall or above the same and might at least partially close the opening. In case that the supporting element is movable with respect to the housing of the air dryer cartridge, a displacement of the supporting element changes the bias of the at least one spring and changes the pressing force of the desiccant. The movement of the supporting element away from the desiccant is limited by a stop element. The stop element might be held at the housing, might be linked with the housing or might be built by the housing itself. A displacement along the degree of freedom of the supporting element (limited by the stop element) is used for changing the pressing force of the desiccant. On the other hand, the supporting element being movable under a change of the bias of the spring (in contrast to a supporting element being fixed at the housing) builds a spring element which according to the invention might be used for an additional function. The limit of the degree of freedom given by the stop element defines an end position of the supporting element correlating with a minimal pressing of the desiccant. Furthermore, it is possible that by use of the stop element the supporting element without additional measures does not remove from the unit built by the air dryer cartridge. Accordingly, for this embodiment the air dryer cartridge builds a transportable unit also when not assembled with the air dryer. 
         [0028]    The moving degree of freedom of the supporting element and the use of the supporting element as a spring element for clamping the air dryer cartridge in the air dryer might also be used for a compensation of tolerances which in the end leads to a reduction of manufacturing requirements for the air dryer and the air dryer cartridge. 
         [0029]    For one embodiment of the invention, the degree of freedom of the supporting element is used for reducing the pressing force of the desiccant during stocking and transportation whereas it is possible to increase the pressing with a displacement of the supporting element for the use of the air dryer cartridge in the air dryer. An increased pressing during the use of the air dryer cartridge might be of advantage in case of encountering oscillating inner pressures (e.g. up to 13 bar). These oscillating pressures and vibrations of the air dryer for too small pressing forces of the desiccant lead to relative displacements of the particles of the desiccant. These undesired relative displacements might result in increased wear. 
         [0030]    For a preferred embodiment of the invention, the stop element is designed, configurated and positioned such that a dimension of the air dryer cartridge limited by the supporting element and the stop element is larger than the corresponding dimension of a housing of an air dryer for which said air dryer cartridge is designated. This embodiment is now explained by way of a simple (non-limiting) example: In case that
       the above dimension is the longitudinal extension of the air dryer cartridge between the contact region of the supporting element in the position defined by the stop element and the base wall and this longitudinal extension is denoted with L,   the distance between a counter contact region of the top wall of the housing of the air dryer (at which the contact region of the supporting element contacts in the assembled state) from the contact region of the base wall of the air dryer cartridge at a socket element of the air dryer is denoted with A,       
 
         [0033]    L&gt;A or L−A=F holds. An assembly of the air dryer cartridge in the air dryer requires that the supporting element has to be moved away from the stop element along the degree of freedom with a displacement F. This displacement has the consequence that a tension of the spring and the pressing of the desiccant is increased. The increase of the tension of the spring and the pressing of the desiccant results from the product of F with the spring stiffness of the at least one spring. On the other hand, the displacement has the consequence that the tension of the spring is no longer supported by the stop element. Instead, the supporting element (after the displacement over the distance F) is supported with the tension of the spring at the top region of the housing of the air dryer. Accordingly, the air dryer cartridge is clamped in the housing of the air dryer for fixing the air dryer cartridge in the air dryer. An assembly of the air dryer requires that a top cover element is moved towards the socket element with a coinciding displacement F of the supporting element of the air dryer cartridge. With or after the displacement F of the supporting element the top cover element and the socket element of the air dryer are connected with each other and fixed relative to each other. It is also possible that the top cover element of the air dryer is screwed with the socket element of the air dryer, wherein with increasing screwing angle between top cover element and socket element the supporting element moves with an increase of the tension of the spring and of the pressing of the desiccant. 
         [0034]    A lot of measures can be taken for building the stop element. To give only one non-limiting example, the stop element might be built by an upper edge or part of the side wall which might be angled in inner direction. For one embodiment of the inventive air dryer cartridge, the stop element is built with at least one anchor element extending through the air dryer cartridge. The anchor element or pulling element might also extend through the desiccant. It is also possible that the anchor element extends from an upper end region of the air dryer cartridge to the opposite end region of the air dryer cartridge, e.g. built by a base wall of the air dryer cartridge. Furthermore, it is possible that only one single anchor element is used. Besides other options, the invention suggests arranging the anchor element coaxial to the longitudinal axis of the air dryer cartridge. However, it is also possible to use a plurality of anchor elements that might be located centrally or offset from the center. For a non-limiting example two, three, four or more anchor elements are dispersed in circumferential direction with same distances from each other and from the longitudinal axis. For another embodiment of the invention, it is possible to use the anchor element not only for limiting the degree of freedom of the supporting element. Instead, it is also possible that the anchor element comprises an outer surface which is usable as a guiding surface for guiding the supporting element and/or the pressing element in lateral direction. 
         [0035]    There are a lot of options for the design of the anchor element. For one embodiment the anchor element is built by a rod, a wire, a screw or a tube. 
         [0036]    For another embodiment of the invention there is not only one spring interposed between the supporting plate and the pressing element. Instead, a plurality of springs is used. For one non-limiting example, the plurality of springs is uniformly dispersed in circumferential direction around the longitudinal axis. 
         [0037]    Also for the design of the supporting element there are a lot of options covered by the invention. For one particular embodiment, the supporting element comprises an outer contact region which is freely accessible in case that the air dryer cartridge is not assembled with an air dryer. With the assembly of the air dryer cartridge with the housing of the air dryer, the contact region contacts a counter contact region of the housing of the air dryer. Contact forces between the contact region and the counter contact region cause the movement of the supporting element along the degree of freedom of the supporting element. It is possible that the contact region is built with a continuous contact surface (e.g. a ring surface) which might be arranged coaxial to the longitudinal axis of the air dryer cartridge. However, it is also possible that there is a plurality of contact surfaces dispersed uniformly in circumferential direction around the longitudinal axis. By means of the plurality of contact surfaces, a specific design and configuration of the contact region of the supporting element and the counter contact region of the air dryer is also suggested. this might be used for easing a sliding movement between the supporting element and the housing of the air dryer during the screwing process of screwing the top cover element of the housing of the air dryer with the socket element. To name only one non-limiting example, the contact region and/or the counter contact region might be equipped with a sliding layer or a lubricant for easing the screwing process. It is also possible that the contact region is built by a central contact surface which is located at the longitudinal axis of the air dryer cartridge in order to minimize the relative movement between the housing of the air dryer and the contact region of the supporting element during the screwing process of the housing of the air dryer. 
         [0038]    Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0040]      FIGS. 1 to 5  are longitudinal sections of different embodiments of an air dryer with an air dryer cartridge according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Referring now in greater detail to the drawings,  FIG. 1  illustrates an air dryer  1  with an air dryer cartridge  2  located therein. The air dryer  1  is built with a socket element  3  and a cover element  4  which is (in a first approximation) dome-shaped. The socket element  3  builds an inlet chamber  5  which (in the load phase) is connected with a pressurized air source (in particular a compressor). Furthermore, the socket element  4  comprises an outlet chamber  6  which is connected with the pressurized air system, in particular at least one consumer circuit. The socket element  4  comprises a ring-shaped collar  8  which has an orientation coaxial to a longitudinal axis  7 - 7 . The collar  8  comprises an outer thread  9 . At the front the collar  8  comprises a groove  10 . A ring-shaped sealing element  11  is located in the groove  10 . The socket element  4  has a massive design and has in particular been produced by forming or molding. The socket element  4  is e.g. made of metal (in particular aluminium) or a plastic material. 
         [0042]    The cover element  3  is dome-shaped with a domed or curved cover wall  12  and a side wall  13  in the shape of a hollow cylinder. For easing the removal of the cover element  3  from a mold, it is possible that the side wall  13  is slightly conical opening towards the bottom. In the end region facing away from the cover wall  13 , the side wall  13  comprises a radial extension  14  for building a front surface  15  and a hollow cylindrical connecting region  16  equipped with an inner thread  17 . 
         [0043]    The cover element  3  and socket element  4  have a massive design and have in particular been produced by forming or molding. The cover element  3  and the socket element  4  are e.g. made of metal (in particular aluminium) or a plastic material. 
         [0044]    In the assembled state the cover element  3  and the socket element  4  define an inner chamber  18 . The inlet chamber  5  and the outlet chamber  6  are connected with the inner chamber  18 . The air dryer cartridge  2  is located in the inner chamber  18 . 
         [0045]    The air dryer cartridge  2  is built with a housing  19  which (in the shown longitudinal section) is approximately U-shaped and symmetrically to its longitudinal axis. The transverse leg of the U builds a base wall  20 , whereas the two parallel longitudinal legs of the U build the side wall  21 . The base wall  20  comprises passages  22  (in particular bores  23 ) for a transfer of pressurized air between an inner chamber  24  of the housing  19  and the outlet chamber  6 . In the transitional region between the base wall  20  and the side wall  21  the housing  19  comprises wing-like ribs  25  dispersed in circumferential direction. The ribs  25  build radial guiding surfaces  26  having an orientation parallel to the longitudinal axis  7 - 7 . The guiding surfaces  26  interact with a cylindrically guiding surface  27  built by an inner surface of the collar  8  for providing a radial guidance, an exact positioning and orientation. Furthermore, with their front surfaces  28  facing towards the socket element  4  the ribs  25  contact a shoulder  29  of the socket element  4 . By this contact, the position of the air dryer cartridge  2  relative to the socket element  4  in longitudinal direction is defined. A sealing element  30  for blocking a transfer of pressurized air between the inlet chamber  5  and the outlet chamber  6  is interposed between the socket element  4  and the base wall  20 . For the embodiment shown in  FIG. 1 , the sealing element  30  is located in a groove having an orientation in radial inner direction. In the assembled state, a disc  32  is enclosed or trapped between the ring collar  31  and the socket element  4 . With its radial outer surface the sealing element  30  contacts a hollow cylindrical sealing surface of the socket element  4 . It is also possible that radially inside from the sealing element  30  the base wall builds another ring collar  33  for stiffening the base wall and/or for building a support or guidance for the assembly and the centering movement. 
         [0046]    A non-woven fabric, a filter or a textile material  34  is positioned In the inner chamber  24  on the base wall  20  so that the passages  22  are covered. The desiccant  35  is located on this layer or material in the inner chamber  24  (only schematically shown in the figures). On the side opposite to the base wall  20  the end regions of the side wall  21  of housing  19  build an opening  36 . The opening  36  is used for introducing the non-woven fabric  34  and the desiccant  35  into the inner chamber  24  of the housing  19 . A pressing element  37  is inserted into the opening  36  (similar to a piston). The pressing element  37  is biased by at least one spring  38 , here by two or more springs  38   a,    38   b,  towards the base wall  20 . Accordingly, the pressing element  37  is used for producing a pressing force of the desiccant  35  between the pressing element  37  and the base wall  20 , For the embodiment shown in  FIG. 1 , another non-woven fabric, a textile material or a filter  39  is interposed between the desiccant  35  and the pressing element  37 . The pressing element  37  is built by a pressing plate  40  having a hollow cylindrical guiding collar  51 . The guiding collar  51  builds am small gap with the side wall  21  for providing a guidance and to some extent also a kind of sealing. The pressing plate  40  comprises passages  41 , here bores  42 . Pressurized air is transferred through the passages  41  from an outer region  43  of the air dryer cartridge  2  to the inner chamber  24  and the desiccant  35  (and vice versa). A base of the spring  38   a,    38   b  is supported at the pressing element  37 . The other base of the spring  38   a,    38   b  is supported at the supporting element  44 . For the shown embodiment the supporting element  44  is built by a supporting plate  45 . 
         [0047]    At the side facing away from the spring  38   a,    38   b  the supporting element  44  comprises a supporting collar  46 . In the assembled state of the air dryer  1  as shown in  FIG. 1 , a front surface of the supporting collar  46  is pressed with a contact region  58  at a counter contact region  59  of the cover wall  12  of the cover element  3  of the air dryer  1 . In this state the spring  38   a,    38   b  is pretensioned. 
         [0048]    A pulling element or anchor element  47  extends coaxial to the longitudinal axis  7 - 7  through the air dryer cartridge  2  and the desiccant  35 . For the embodiment shown in  FIG. 1 , the anchor element  47  is built by a rod or wire  48 . Both the pressing element  37  and the supporting element  44  comprise a central guiding sleeve  49 ,  50 . The anchor element  47  passes through the guiding sleeves  49 ,  50 . Both the supporting element  44  as well as the pressing element  37  have a degree of freedom with respect to the anchor element  47  along the longitudinal axis  7 - 7 . The pressing element  37  is guided both by a guiding contact between the guiding sleeve  50  and the outer surface of the anchor element  47  as well as by a guiding contact between the guiding collar  51  and the inner surface of the side wall  21 . The supporting element  44  is only guided by the contact of the guiding sleeve  49  with the outer surface of the anchor element  47 . Additional force components with an orientation transverse to the longitudinal axis  7 - 7  might also be produced by the spring  38   a,    38   b.    
         [0049]    The anchor element  47  is (fixedly or with a limited translational degree of freedom along the longitudinal axis  7 - 7 ) linked with the base wall. For the shown embodiment according to  FIG. 1 , for this purpose the anchor element  47  passes through a holding or guiding sleeve  52  located in or built by a central bore of the base wall  20 . On the side facing away from the desiccant  35 , the degree of freedom of the anchor element  47  with respect to the base plate  20  is limited by equipping the anchor element  47  with a stop element or thickening  53 . For the embodiment shown in  FIG. 1 , a disc  54  is interposed between the thickening  53  and the guiding sleeves  52 . 
         [0050]    On the side facing away from the spring  38   a,    38   b  the anchor element  47  protrudes from the supporting element  44 . On this side the anchor element  47  comprises a stop element or thickening  55 . For the embodiment shown in  FIG. 1 , a disc  56  is interposed between the stop element  55  and supporting element  44 . Here, the disc  56  is guided in longitudinal direction by the anchor element  47 . 
         [0051]    In the assembled state shown in  FIG. 1  there is a gap  57  between the supporting element  44  and the stop element  55 . Above, the width of the gap  57  has been denoted with F. For the shown embodiment according to  FIG. 1 , the anchor element  47  is fixed at the base wall  20  such that the gap  57  is built between the stop element  55  and the supporting element  44 . However, in case of using a sliding guidance between the sliding sleeve  57  and the anchor element  47  it is also possible that the gap  57  is built between the base wall  20  and the stop element  53  (in some cases also with a fixation of the anchor element  47  in the sliding sleeve  49 ). 
         [0052]    For disassembled cover element  3  (e.g. during transportation and/or stocking of the air dryer cartridge  2  and at the beginning of the assembly process or at the end of the disassembly process) the supporting element  44  (with interposed disc  56 ) abuts at the stop element  55  without any gap  57  being present. In this state the supporting element  44  has moved relative to the anchor element  47  by the distance F in upper direction from the state shown in  FIG. 1 . Due to the stop element  55 , it is not possible that the supporting element  44  might completely separate from the air dryer cartridge  2 . Instead, the disc  54 , the base wall  20 , the non-woven fabric  34 , the desiccant  35 , the non-woven fabric  39 , the pressing element  37 , the spring  38   a,    38   b,  the supporting element  44  and the disc  56  are trapped with a clamping force between the two stop elements  53 ,  55 . 
         [0053]    For the assembly of the air dryer cartridge  2  in an air dryer, the cover element  3  is removed from the air dryer  1  and the air dryer cartridge  2  is positioned on the socket element  4 . In this state the supporting element  44  (with interposed disc  56 ) contacts the stop element  55 . In the next assembly step the cover element  3  is assembled with the socket element  4 . This might be done by screwing the inner thread  17  of the cover element  3  with the outer thread  9  of the socket element  4 . During the screwing process, a contact region  58  built by the front surface of the supporting collar  64  comes into contact with the counter contact region  59  of the cover wall  12  of the cover element  3 . With further screwing the cover wall  12  moving downwards along the longitudinal axis  7 - 7  moves the supporting element  44  in downward direction. This movement of the supporting element is caused by the contact force at the counter contact region  59 . With the movement the width of the gap  57  increases. With the screwing process also the tension of the spring  38   a  increases. The increasing tension of the spring  38   a  results in an increased clamping force of the air dryer cartridge  2  in the air dryer  1  in the direction of the longitudinal axis  7 - 7  as well as in an increase of the pressing force of the desiccant  35 . For applying a screwing torsional moment, the cover element  3  might be equipped with an inner hexagonal recess  60  at the cover wall  20 . With the screwing process the inner chamber  18  is sealed by pressing the front surface  15  of the cover element  3  at the sealing element  11 . 
         [0054]    The bases of the springs  38   a,    38   b  might be guided in guiding elements of the pressing element  37  and the supporting element  44 . In  FIG. 1  the guiding elements are built by ring collars  61 ,  62 . 
         [0055]    During a load phase of the air dryer cartridge  2  the stream of pressurized air in the air dryer  1  according to  FIG. 1  is as follows: 
         [0056]    Pressurized air passes from the inlet chamber  5  via intermediate spaces between the ribs  25  to an intermediate chamber  63  built between the inner surface of the side wall  13  of the cover element  3  and the outer surface of the side wall  21  of the air dryer cartridge  3 . In the intermediate space  63  the pressurized air streams in upward direction. Below the cover wall  12  of the cover element  3  the streaming direction reverses. Then the pressurized air streams to an outer region  43  via a residual opening  64  built between the upper edge of the side wall  21  and the upper edge of the supporting element  44 . The residual opening  64  has a ring-shape. From the outer region  43  the pressurized air streams via the passages  41 , the non-woven fabric  39 , the desiccant  35 , the non-woven fabric  34  and the passages  22  to the outlet chamber  6 . 
         [0057]    There are a lot of options for building the stop elements  53 ,  55 . For the embodiment shown in  FIG. 1 , the anchor element  47  is built by a rod or wire  48 . The stop elements  53 ,  55  are manufactured by a forming process, namely by deforming the ends of the rod or wire  48  from a small circular cross-section to an increased cross-section with segments of a circle and flattenings. 
         [0058]    The housing  19 , the pressing element  37  and/or the supporting element  44  might be made of metal, a light metal or plastic. It is possible that these elements are built by forming or injection molding. 
         [0059]    For removed cover element  3  the supporting element  44  is freely accessible from the outside so that the supporting element  44  is (at least partially) not covered by a wall of the housing of the air dryer cartridge  2 . 
         [0060]    After the disassembly of the air dryer cartridge  2  from the air dryer and a removal of the stop element  55  (e.g. plastic deformation), it is possible to remove the supporting element  44 , the spring  38  and the pressing element  37 . For an embodiment not shown in the figures, the supporting element  44 , the spring  38  and the pressing element  37  build an assembly unit. In the next step it is possible to remove an exhausted desiccant  35  from the inner chamber  24 . If present and necessary, also other filter elements can be removed. In a next step a fresh desiccant (and fresh filter elements) are inserted into the inner chamber  24  with subsequent assembly of the pressing element  37 , the spring  38  and the supporting element  44 , e.g. with another plastic deformation for building the stop elements  55 . The person with ordinary skill in the art will know that any other design of the stop elements  53 ,  55  might be used, e.g. a nut screwed with the anchor element  47  or any other removable or releasable stop element. 
         [0061]      FIG. 2  shows an air dryer cartridge  2  in an air dryer  1  with a design generally corresponding to the embodiment shown in  FIG. 1 . However, in this case the supporting element  44  is built by a pure plane circular disc (so without a supporting collar  46  and without ring collars  61  for receiving the springs  38   a,    38   b ). In this modified design the contact region  58  is built by the radial outer edge region of the supporting plate  54 . 
         [0062]    Furthermore, in  FIG. 2  the anchor element  47  is not built by a rod or wire  48  but by a tube  65 . For building the stop elements  53 ,  55  the tube  65  in its end region is widened or provided with rivets. In  FIG. 2  a sphere  71  is pressed into the tube  65  for closing a bypass for pressurized air. 
         [0063]    For the embodiment shown in  FIG. 2 , the side wall  21  of the housing  19  of the air dryer cartridge  2  is equipped with ribs. The radial outer front surfaces of the ribs contact at the inner surface of the side wall  13  of the cover element  3  for guiding purposes. 
         [0064]    The base wall  20  for the embodiment shown in  FIG. 2  is built with a plurality of base wall parts  20   a,    20   b.  The transfer of pressurized air from the inner chamber  24  to the outlet chamber  6  is provided by passages  22  in the upper base wall part  20   a  via an additional filter  66  which is held between the two base wall parts  20   a,    20   b.  Here, also the lower disc-like base wall part  20   b  is secured by the stop element  55  as shown in  FIG. 2 . 
         [0065]    For a design generally corresponding to the embodiment shown in  FIG. 1 , according to  FIG. 3  the side wall  21  of the air dryer cartridge  2  in a transitional region to the base wall narrows. In the transitional region a filter  67  is located which is interposed between the inlet chamber  5  and the intermediate chamber  63 . For the shown embodiment the housing  19  is built with two coaxial hollow cylindrical wall parts. The filter  67  is interposed between the two wall parts. As can be seen in  FIG. 3 , different desiccants  35   a,    35   b  and  35   c  are positioned in stacked layers in the inner chamber  24 . Additionally, a filter  66  is used in the region of the base wall  20  (the filter  66  is in further detail described and shown in  FIG. 2 ). 
         [0066]    According to  FIG. 3 , the anchor element  47  built by a rod or wire  48  does not only comprise the end-sided stop elements or thickenings  53 ,  55 . An additional thickening  68  is provided used for trapping the disc  54 , the base wall part  20   b,  the filter  66  and the base wall part  20   a  (with an additional disc). 
         [0067]      FIG. 4  shows an embodiment similar to that of  FIG. 3 . The housing  19  of the air dryer cartridge  2  in the region of the outer surface of the side wall  21  comprises a rib  69  extending spirally around the longitudinal axis  7 - 7 . The rib  69  with its outer surface closely fits to the inner surface of the side wall  13  of the cover element  3 . By means of the rib  69  a type of cyclone is built. The cyclone has the effect that pressurized air is not transferred to the opening  64  from the inlet chamber  5  by a pure vertical movement parallel to the longitudinal axis  7 - 7 , but spirally guided along the outer surface of the side wall  21 . The length of the path of the pressurized air between the inlet chamber  6  to the opening  64  is increased which serves an increased cooling effect. The cooling might be provided by the inner surface of the cover element  3 . For increasing the cooling effect, the cover element  3  might also be equipped with cooling ribs  70 . For this embodiment a first condensation of humidity contained in the pressurized air might occur in the intermediate chamber  63  such that only a reduced remaining humidity passes the desiccant  35 . This leads to extended load cycles before the need of a regeneration. Also the lifetime of the air dryer cartridge  2  without the need for a replacement of the desiccant  35  might be increased. 
         [0068]    For a modified embodiment (not shown in detail) the support of the supporting element  44  by an anchor element  47  held by the base wall  20  might also be used for air dryer cartridges of the closed type as disclosed in DE 699 08 918 T2 (whereas in this case differing from DE 699 08 918 T2 the springs  38   a,    38   b  are not supported at the top wall of the housing of the air dryer). In this way, also for air dryer cartridges according to the type of DE 699 08 918 T2 the stresses of the side wall of the housing of the air dryer cartridge  2  due to the pressing force might be reduced. 
         [0069]    It is also possible that the springs  38   a,    38   b  are used for clamping the air dryer cartridge  2  in the housing of the air dryer  1  without the use of anchor elements  47  extending through the air dryer cartridge  2 . In this case, end regions of the side wall  21  might be plastically deformed in radial inner direction (or might be equipped with additional holding elements) such that the inner side of the plastically deformed regions or a holding element contact the upper side of the supporting element  44 . Accordingly, the supporting element  44  is (similar to the design with the stop element  55 ) held in an upper end position. With the assembly of the air dryer cartridge  2  in the housing of the air dryer  1 , the supporting element  44  moves away from the end regions  73  for clamping the air dryer cartridge  2  (see  FIG. 5 ), 
         [0070]    The person with ordinary skill in the art will know that differing from the shown embodiments any modification of the stream of pressurized air, the paths, the branching of pressurized air streams to different streaming paths, the use of different filters, cyclones or labyrinth filters, the use of coalescing filters and the like might also be possible within the frame of the present invention. 
         [0071]    For one particular embodiment, the housing  19  of the air dryer cartridge  2  is made of plastic. Here, the cover element  3  is made of cast aluminium. 
         [0072]    Many variations and modifications may be made to the preferred embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the present invention, as defined by the following claims.