Abstract:
A filter assembly includes a filter body; a central support for the filter body; an opening provided in each of upper and lower ends of the filter body for receiving a respective end of the central support; and a disposable filter cartridge housed within the filter body for receiving a filter member for filtering contaminates. The filter member is arranged for fluid flow in a radial direction from a first side of the filter member to a second side of the filter member. The disposable filter cartridge includes an impermeable wall that extends axially through the filter member adjacent the second side thereof to protect the second side of the filter member during replacement of the disposable filter cartridge. The impermeable wall is defined by a hollow cylinder which is axially aligned with the openings provided in the upper and lower ends of the filter body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/262,352 filed on Sep. 28, 2011 which is a national stage entry under 35 USC §371 of PCT Patent Application No. PCT/EP2010/054528 filed on Apr. 6, 2010 and claiming priority to EP Patent Application No. EP 09157279.2 filed on Apr. 3, 2009, the disclosures of which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD OF INVENTION 
       [0002]    This invention relates to a filter assembly. In particular, but not exclusively, the invention relates a filter assembly for cleaning fuel in a fuel system of a compression ignition internal combustion engine. 
       BACKGROUND OF INVENTION 
       [0003]    A fuel filter of a fuel system of an internal combustion engine is used to remove contaminates from the flow of fuel, thereby avoiding the transmission of the contaminates to, for example, the high pressure fuel pump or the injectors of the fuel system. Unfiltered fuel can contain particulate contaminates, such as dirt or rust, or fluidic contaminates, such as moisture from the fuel tank of the fuel system. The transmission of such contaminates may result in increased wear rates for the components of the fuel system and a less efficient fuel burn. 
         [0004]    A typical filter assembly comprises a filter head including ports that connect the filter assembly to the fuel system, and a filter can secured to the filter head. The filter can contain a filter medium. The filter medium forms part of a filter cartridge located within the filter can. Optionally, the filter assembly can also include a water storage capacity or decantation volume for storing the fluidic contaminates once they have been filtered out of the fuel flow. 
         [0005]    Filter servicing is necessary either when the filter medium becomes obstructed by the accumulation of the particulate contaminates and needs to be replaced, and/or when the water storage capacity is full. When servicing the filter medium, either the filter cartridge alone is replaced or the entire filter assembly. The former type of filter is known as a ‘removable cartridge filter’, and the latter is known as a ‘throw-away filter’. 
         [0006]    The cost of replacement parts of a removable cartridge filter is lower when compared to a throw-away filter because only the removable filter cartridge is replaced. However, a throw-away filter benefits from lower service labour cost due to the ease with which it is replaced. 
         [0007]    Furthermore, when servicing a removable cartridge filter, unless means are provided to protect the clean side of the filter medium, the filter medium will be subject to the possibility of contamination. For example, if a removable filter is constructed so that fuel flows across the filter medium in a radially outwards direction from an inner dirty side to an outer clean side of the filter medium, the clean side of the filter medium will be exposed to the possibility of contamination when being handled during servicing. Conversely, if the fuel flows across the filter medium in a radially inwards direction from an outer dirty side to an inner clean side of the filter medium, the clean side of the filter medium will be subject to the possibility of contamination if the cartridge is handled at upper and lower ends of the filter medium. In both of these configurations, unless measures are taking to protect the clean side of the filter medium, the clean side&#39;s proximity to an outlet of the removable cartridge filer will also expose it to possible contamination. 
         [0008]    Whereas, as a throw-away filter is supplied “ready-to-fit”, the filter cartridge itself is not handled during maintenance and, therefore, is not subject to the possibility of contamination. 
         [0009]    A further issue with some conventional filter assemblies relates to the use of a heater, the heater being arranged to heat the fuel to prevent the formation of wax particles in the fuel prior to filtration, for example. The heat transfer capacity of the heater of a conventional filter assembly is limited by its relatively small heat exchange surface area. In addition, typically the heater is fixed on the periphery of the filter assembly which increases the overall size of the filter assembly and impacts on the limited space available in the engine compartment. 
         [0010]    A further issue with conventional filter assemblies relates to the proximity of the fuel flow to the fluidic contaminates in the decantation volume. For example, if the fuel flows into a heater at the top of the filter assembly and exits the heater into a decantation volume at the bottom of the filter assembly, the fluidic contaminates in the decantation volume become disturbed and entrained into the fuel flow. 
         [0011]    It would be desirable to provide a fuel filter that overcomes or at least alleviates at least one of the above-mentioned problems and disadvantages in the prior art. 
       SUMMARY OF THE INVENTION 
       [0012]    Briefly described, a filter assembly includes a filter body; a central support for the filter body; an opening provided in each of upper and lower ends of the filter body for receiving a respective end of the central support; and a disposable filter cartridge adapted to be housed within the filter body for receiving a filter member in the form of a hollow cylinder for filtering contaminates from a flow of fluid through the filter assembly. The filter member is arranged for fluid flow in a radial direction from a first side of the filter member to a second side of the filter member. The disposable filter cartridge includes an impermeable wall that extends axially through the filter member adjacent the second side thereof to protect the second side of the filter member during replacement of the disposable filter cartridge. The impermeable wall is defined by a hollow cylinder which is axially aligned with the openings provided in the upper and lower ends of the filter body. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1  is a cut-away view of a filter assembly of a first embodiment of the invention with a filter cartridge of the assembly removed; 
           [0015]      FIG. 2  is a cut-away view of a filter cartridge for use in the filter assembly of  FIG. 1 ; 
           [0016]      FIG. 3  is a cut-away view of the filter assembly of  FIG. 1 , with the filter cartridge of  FIG. 2  in situ; 
           [0017]      FIG. 4  is a sectional view of a central support of the filter assembly in  FIGS. 1 and 3 ; and, 
           [0018]      FIG. 5  is a sectional view of the filter assembly in  FIGS. 1 and 3  illustrating the flow passage for fluid through the assembly, in use. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0019]    A filter assembly of an embodiment of the invention generally has three aspects:
       i) a filter body;   ii) a central support for the assembly; and,   iii) a filter cartridge having a filter medium.       
 
         [0023]    With reference to  FIG. 1 , the filter assembly  1  comprises a generally cylindrical central support  3  (referred to as the central support) positioned along the centreline of a generally cylindrical filter body  2  (referred to as the filter body). The cross-sectional area of the filter body  2  is stepped along its length to create a shoulder  5  towards its lower end. The upper and lower ends of the filter body  2  carry a filter cover (or head or lid)  6  and a filter bowl  8  respectively. The filter bowl  8  houses the filter components of the filter assembly  1 . Typically, the filter cover  6  is sealed to the filter body  2  during manufacture. A decantation volume  9  for collecting water is defined by the inner surface of the filter body  2  in the lower or base region of the filter body  2  between the shoulder  5  and the base of the filter bowl  8 . 
         [0024]    In the illustrated embodiment, the filter cover  6  is provided with three integral openings; an inlet opening  10 , an outlet opening  12 , and a central opening  14 . The inlet and outlet openings  10 ,  12  are radially outward of the centre of the filter cover  6 . The filter bowl  8  is provided with only a central opening  16 . The central openings  14 ,  16  of the filter cover  6  and the filter bowl  8  are axially aligned with each other and are arranged to receive a respective end of the central support  3 . An enlarged head  18  of the central support  3  projects through the central opening  14  in the filter cover  6  so that its underside abuts the upper surface of the filter cover  6 . The lower end of the central support  3  extends towards the central opening  16  in the filter bowl  8  and is secured in position by a locking member  20  received, in part, within the opening  16 . The locking member  20  includes a screw-threaded part in the form of an upwardly-standing tubular portion  20   a  carrying a screw thread on its internal surface and a head portion  20   b  located on the outside of the filter bowl  8  so as to be accessible during servicing. The tubular portion  20   a  projects through the central opening  16  in the filter bowl  8  and is fastened to the external surface of the lower end of the central support  3  by means of screw threaded engagement. It will be appreciated that in other embodiments, the central support  3  can be secured in position by an alternative locking means. For example, the screw thread may be on the internal surface of the central support  3  and the external surface of the locking member  20 . 
         [0025]    With reference to  FIGS. 2 and 3 , the filter body  2  and the central support  3  define an annular volume between them within which a filter cartridge  4  is located and supported. At its lower end, the filer cartridge  4  carries a series of projections  21  which rest on the shoulder  5  of the filter body  2  to locate the cartridge  4  in position. The filter cartridge  4  comprises an upper part  22  and a lower part  23  between which a generally cylindrical hydrophobic filter medium  30  (referred to as the filter medium) is located. An inlet port  24  and an outlet port  25  are provided in the upper part  22  of the filter cartridge  4 . The inlet and outlet ports  24 ,  25  are designed for connection to a fuel line or pipe for transferring fuel to or from, respectively, the filter assembly  1 . The inlet port  24  of the filter cartridge  4  is arranged to align with the inlet opening  10  of the filter cover  6  and is connected to an inlet pipe  26  which communicates with, for example, a low-pressure transfer pump (not shown). The inlet pipe  26  is received within the inlet port  24  by means of a press fitting and is securely fixed in the inlet opening  10  of the filter cover  6  during manufacture by way of, for example, a braze weld. The inlet pipe  26  is arranged to communicate with the interior of the central support  3  by way of a first radial opening  27  provided in the central support  3  towards its upper end. Similarly, the outlet port  25  is arranged to align with the outlet opening  12  of the filter cover  6  and is connected to an outlet pipe  28  which communicates with, for example, the inlet of a high pressure fuel pump (not shown). The outlet pipe  28  is secured to the outlet port  25  of the filter cartridge  4  using a press fitting and is fixed in the outlet opening  12  of the filter cover  6  during manufacture. 
         [0026]    The filter medium  30  is used to filter particulate contaminates from the fuel flow. The upper and lower surfaces of the filter medium  30  are bonded to the internal surfaces of the upper and lower parts  22 ,  23  of the filter cartridge  4  respectively. An impermeable wall  32  extends through the filter medium  30 , along its central axis, and is fixed to the upper and lower parts  22 ,  23  of the filter cartridge  4  at its upper and lower ends, respectively. The position of the impermeable wall  32  is such that it is axially aligned with the openings  14 ,  16  in the upper and lower ends  6 ,  8  of the filter body  2 . 
         [0027]    An outer (or first) side  34  (referred to as the “dirty” side) of the filter medium  30  and the inner surface of the filter body  2  together define a first annular volume  36 . The first annular volume  36  is in communication with the interior of the central support  3  by way of a second radial opening  38  in the central support  3  located towards its upper end and closer to the upper end than the first radial opening  27 . An inner (or second) side  40  (referred to as the “clean” side) of the filter medium  30  and the impermeable wall  32  of the filter cartridge  4  together define a second annular volume  42 , radially inward of the first annular volume  36 . The second annular volume  42  is in communication with the outlet port  25  of the filter cartridge  4 . The manner in which the filter medium  30  is bonded to the upper and lower parts  22 ,  23  of the filter cartridge  4  is such that fuel can only flow from the first annular volume  36  (the dirty side  34  of the filter medium  30 ) to the second annular volume  42  (the clean side  40  of the filter medium  30 ) in a radially inward direction through the filter medium  30 . 
         [0028]    With reference to  FIG. 4 , the interior of the central support  3  is provided with a wall in the form of two heat exchange plates  43 ,  44  which serve to divide the interior into first and second chambers  46 ,  48 . The first and second chambers  46 ,  48  are in communication with one another at their lower ends. A series of integral heating elements  49  are located between and spaced along the heat exchange plates  43 ,  44 . One of the heat exchange plates  44  is connected to a thermostatic switch  45  by an electric connection (not shown). 
         [0029]    In another embodiment (not shown), the wall may comprise a single heat exchange plate located along the centre line of the interior of the central support  3  and having a series of integral heating elements located along one of its sides. 
         [0030]    With reference to  FIG. 5 , in use, with the inlet and outlet pipes  26 ,  28  connected to the appropriate fuel lines, operation of the low-pressure transfer pump located upstream of the filter assembly  1  will result in fuel being pumped into the inlet port  24 , through the first radial opening  27  in the central support  3  and, hence, into the central support  3 . The manner in which the heat exchange plates  43 ,  44  are positioned in the central support  3  is such that fuel can only flow from the first radial opening  27  in the central support  3 , along the length of the central support  3  to the bottom of the first and second chambers  46 ,  48 , as indicated by the arrows in  FIG. 5 . The fuel then flows to the top of the second chamber  48 , exits the central support  3  from the second radial opening  38  and flows into the first annular volume  36 . From the first annular volume  36 , some of the fuel flows between the projections  21  into the decantation volume  9 . Once the capacity of the decantation volume  9  is used, the fuel flows in a radially inward direction through the filter medium  30 . 
         [0031]    The heat exchange plates  43 ,  44  therefore increase the fuel passage through the filter assembly  1  and make a significant heat exchange surface area available within the central support  3 , thereby providing ample heat exchange from the integral heating elements  49  to the fuel flow. 
         [0032]    The heating elements  49  heat the fuel on transit through the central support  3  to the first annular volume  36 . If the temperature of the fuel in the low-pressure transfer pump is relatively low, as would occur upon initial engine start-up under certain atmospheric conditions, the fuel may be subject to the formation of wax particles which may cause blockage of the filter medium  30 . Heating the fuel reduces the formation of the wax particles in the fuel and, hence, reduces the possibility of the filter medium  30  becoming blocked. The heat exchange surface area of the heat exchange plates  43 ,  44  ensures that the fuel flow is sufficiently heated during transit through the central support  3 . This arrangement provides a compact filter assembly when compared with conventional fuel filters by removing the need to fix an external heating element to the filter assembly  1 , thereby saving limited space in the engine compartment. 
         [0033]    The filter medium  30  is used to collect the particulate contaminates as the fuel flows in a radially inward direction from the first annular volume  36 , through the filter medium  30  into the second annular volume  42 . The provision of the filter medium  30 , positioned between the first and second annular volumes  36 ,  42 , prevents any particulate contaminates in the fuel flow from exiting the clean side  40  of the filter medium  30  and, in so doing, ensures that no particulate contaminates are transmitted downstream of the filter assembly  1 . 
         [0034]    A compression ignition internal combustion engine relies on the fuel for lubrication. If the lubricating fuel contains fluidic contaminates such as water, the moving parts of the engine would be likely to overheat. Therefore, in addition to removing the particulate contaminates from the fuel flow, it is also considered desirable for the filer assembly  1  to remove any water present in the fuel flow. 
         [0035]    The filter medium  30  extracts the water from the fuel as the fuel flows from the first annular volume  36  to the clean side  40  of the filter medium  30 . From the clean side  40  of the filter medium, the filtered fuel flows into the second annular volume  42  and exits the filter assembly  1  from the outlet port  25  on the upper part  22  of the filter cartridge  4 . The extracted water droplets agglomerate on the dirty side  34  of the filter medium  30  and then flow between the projections  21  on the filter cartridge  4  into the decantation volume  9 . The decantation volume  9  represents a fuel flow “dead zone” meaning that there is substantially no net fuel flow through it. The extracted water migrates to the bottom of the decantation volume  9  due to its density being higher than the density of the fuel, so that fuel is displaced from the decantation volume  9  when it is at capacity. 
         [0036]    In this arrangement, the fuel flow is kept separate from the extracted water in the decantation volume  9 , meaning that the fuel flow does not come into contact with the extracted water at any stage during filtration. This ensures that the extracted water in the decantation volume  9  is not agitated by the fuel flow, thereby eliminating the possibility of the extracted water being entrained into the fuel flow. 
         [0037]    The central support  3  optionally includes a water sensor (not shown) to detect the level of the water in the decantation volume  9  and to signal an operator when the water level reaches a predetermined limit. When the water level reaches the predetermined level, the operator only has to unfasten the locking member  20  from the central support  3  to allow the water to escape from the decantation volume  9 . It will be appreciated that other combinations of sensors and/or actuators can also be housed in the central support  3 , for example, but not limited to, a clogging sensor, a temperature sensor or a pressure sensor. 
         [0038]    The operation which must be performed upon servicing in order to replace the filter medium  30  is relatively simple compared to the operations necessary with conventional removable cartridge filters. All that is required is for the fuel lines to be removed from the inlet and outlet pipes  26 ,  28  and for the locking member  20  to be unfastened from the central support  3 . The central support  3  can then be lifted from the filter body  4 , passing through the central opening  14  in the filter head  6 , and placed into a new filter body and secured in position by the locking member  20 ; the old filter body  2 , together with the filter cartridge  4 , the filter head  6  and the inlet and outlet pipes  26 ,  28  are then disposed of. As the new filter cartridge  4 , filter head  6 , inlet pipe  26  and outlet pipe  28  are secured to one another during manufacture, no steps need to be performed during the servicing procedure to secure these parts to one another and to ensure that appropriate seals are formed. 
         [0039]    The role of the central support  3 , as the primary support component for the filter assembly  1 , permits a reduction in the complexity of the other components. For example, the manner in which the central support  3  is secured in position means that no thread inserts are required in the filter cover  6  or the filter bowl  8 . Instead, the only thread required is at the bottom of the central support  3  for use with the locking member  20 . Furthermore, as any sensors and/or actuators are located within the central support  3 , the need for external fixtures, for fixing a heater on a filter body, for example, is removed. The reduction of features on the filter body  2  and the various components  4 ,  6 ,  26 ,  28  secured to it, which would be necessary for the assembly of a conventional removable cartridge filter, reduces the overall cost of manufacture. Therefore, a considerable proportion of the value of the filter assembly  1  is assigned to the central support  3 , which is retained during servicing. 
         [0040]    A further advantage of the central support  3  is to absorb the net force acting on the filter assembly  1  when pressurised fuel is delivered from the low-pressure transfer pump, thereby improving the robustness of the filter assembly  1  and permitting a lower material specification for the filter body  2 , meaning the cost of manufacturing the filter body  2  is further reduced. 
         [0041]    The present filter assembly  1 , therefore, combines the lower service labour cost of replacing a conventional throw-away filter with the economical advantage of a conventional removable cartridge filter. 
         [0042]    The inclusion of the impermeable wall  32  of the filter cartridge  4  is particularly advantageous during servicing as it protects the clean side  40  of the filter medium  30  from contact with the central support  3  when the central support  3  is inserted into the filter body  2 , thereby removing any possibility of contamination of a clean filter member. This arrangement therefore provides the stringent cleanliness of a throw-away filter. 
         [0043]    It will be appreciated that the above-described filter assembly  1  is not limited for use in a pressurised system having a low-pressure transfer pump located upstream of the filter assembly, and that its advantages over a conventional throw-away filter or removable cartridge filter would still be applicable if it were to be used in a suction system having a lift/transfer pump located downstream of the filter assembly. 
         [0044]    It will also be appreciated that the above-described filter assembly  1  is not limited for use with fuel and that it can be used to process other fluids which are required to be filtered and heated such as, for example, a urea solution. 
         [0045]    Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting and the invention is defined by the scope of the appended claims.