Abstract:
A filter element for a fluid filtration system, particularly for piston cooling jets used in reciprocating piston engines, is formed from a length of filter material arranged helically in a substantially tubular form. By applying a torque the length of filter material is resiliently expandable to a fitting position in which opposing longitudinal edges of the length are spaced apart from each other. The filter element is then fitted over a fluid chamber of the filtration system and allowed to retract to a rest position in which the opposing longitudinal edges are close or in contact. In the rest position the filter element surrounds the fluid chamber and covers a fluid inlet of the fluid chamber. The filter element of the invention can be used to apply local filtration, and can be readily removed for cleaning or replacement by reversing the fitting process.

Description:
TECHNICAL FIELD  
         [0001]    This disclosure relates to filter elements in fluid filtration systems. It is particularly, but not exclusively, applicable to expandable oil filter elements used within piston cooling jets in reciprocating piston engines.  
         BACKGROUND  
         [0002]    Piston cooling jets are widely used on reciprocating piston engines, particularly diesel cycle engines, as additional cooling means. They work by directing a jet of oil or other fluid on to the pistons during the operation of the engine. The jets are generally located within the crankcase housing and direct a jet of oil to the underside of the piston. To ensure a precisely located jet of oil, the jets have nozzles that are of a relatively small diameter internal bore. The oil used is generally the lubricating oil contained within the sump of the engine. The oil contained within the sump often contains impurities and particulates. To prevent the jets becoming blocked, the oil may be filtered. Over time, the filters degrade and become blocked and consequently require replacement or cleaning. Prior art filtration methods rely to a large extent on a central filter within the engine&#39;s oil circuit or on providing an additional simple paper filter for the cooling jets.  
           [0003]    Known filter elements can be difficult to replace or may not provide adequate filtration if the oil circuit is compromised downstream of a central filter. This can happen, for example, if repairs are undertaken in an environment where the risk of contamination from airborne particulates is significant. The present disclosure seeks to provide a filter element that overcomes one or more of these problems.  
         SUMMARY OF THE DISCLOSURE  
         [0004]    In one aspect, a filter element for a fluid filtration system comprises a length of filter material arranged helically in a substantially tubular form, in which opposing longitudinal edges of the length are in facing relationship. The filter element is resiliently and selectively moveable from a rest position, in which the opposing longitudinal edges are a rest spacing apart from each other, to an expanded fitting position, in which the opposing longitudinal edges are a fitting spacing apart from each other. A fluid filtration system including such a filter element is also disclosed.  
           [0005]    In another aspect, a method of fitting a filter element on a fluid filtration system is disclosed, the filter element comprising a length of filter material arranged helically in a substantially tubular form. The method includes the steps of expanding the filter element to an expanded fitting position in which the opposing longitudinal edges of the length are a fitting spacing apart from each other by applying a torque around a central axis of the tubular form in an opposite direction to the filter material&#39;s helix. The filter element is then fitted over a wall portion of the fluid filtration system, and allowed to retract to a rest position surrounding the wall portion. In this rest position, opposing longitudinal edges of the length are in facing relationship to each other and a rest spacing apart from each other.  
           [0006]    In yet another aspect, a method of manufacturing a filter element comprises the steps of taking a substantially flat piece of filter material having a longitudinal axis and winding it around a central axis to form a substantially tubular filter element. Once wound, the longitudinal axis of the flat piece of filter material is subsequently arranged substantially helically.  
           [0007]    Other features and aspects will be apparent from the following description and the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of a filter element according to a first embodiment in a rest position.  
         [0009]    [0009]FIG. 2 is a side view of the filter element of FIG. 1 in an expanded position.  
         [0010]    [0010]FIG. 3 is a side view of a piston cooling jet including a fluid filtration system utilizing the filter element of FIG. 1.  
         [0011]    [0011]FIG. 4 is a part cross sectional side view of the piston cooling jet of FIG. 3. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to the drawings, one embodiment will now be described, by way of example only. A filter element  10  is shown in detail in FIGS. 1 and 2. The filter element  10  comprises a length of filter material  12 , arranged helically in a tubular form. In this embodiment, the filter material  12  is a metal strip with circular perforations  14  provided through the strip. It is to be understood that the perforations  14  can be of any shape, provided that the dimensions of the perforations are such that particulates having a size greater than the permissible particulate size are prevented from passing through the perforations. It is also to be understood that the metal used may be any suitable for the application, but in this case is steel. Opposing ends  16 , 18  of the length of filter material  12  are shaped so that when arranged in the tubular form the opposing ends  16 , 18  of the filter element  10  form planar ends, perpendicular to the central axis  20  of the tubular form. Overall the filter element  10  is therefore cylindrical.  
         [0013]    Partly due to the elastic properties of the filter material and partly due to the helical tube form, the filter element  10  displays a resilient character. It is therefore possible to apply a torque to the filter element  10 , manually or otherwise, to expand the filter element  10  (see FIG. 2). By doing this the diameter of the filter element  10  can be increased from a rest diameter D 1  to a fitting diameter D 2 . When the torque is released the filter element  10  will return to its rest diameter D 1 .  
         [0014]    The filter element  10  can either be formed by rolling a flat sheet into the helical tube form, or alternatively the filter element  10  may be cut from a tubular section. Other forms of manufacture may also be used to form the filter element  10 .  
         [0015]    Referring now to FIGS. 3 and 4, there is shown a piston cooling jet generally referred to as  22 , including a fluid filtration system  24  utilizing a filter element  10 . The piston cooling jet  22  includes a cooling jet housing  26 . The cooling jet housing  26  has a substantially cylindrical side wall  28 , a first end wall  30  and a second end wall  32  defining therein a fluid chamber  34 . A tapered fluid outlet  36  is located in the first end wall  30 . A jet nozzle  38  extends from the fluid outlet  36 . The jet nozzle  38  has an internal passageway  40  and terminates in an internally tapered jet nozzle outlet  42 . It will be understood that the shapes of the fluid outlet  36 , jet nozzle outlet  38  and jet nozzle  42  may be varied and do not form part of the present invention.  
         [0016]    The interior of the cooling jet housing  26  is hollow and defines a fluid chamber  34 . A fluid inlet  44  is formed in the cylindrical side wall  28  of the cooling jet housing  26  as a generally rectangular aperture. A first abutment  46  is provided on the cylindrical side wall  28  near the first end wall  30 . The first abutment  46  is in the general form of an increase in diameter of the cooling jet housing  26 , to form a flange type formation. A second abutment  48  is provided near the second end wall  32 . The second abutment  48  is similar in general form to the first abutment  46 , being a general increase in diameter of the cooling jet housing  26 , to form a flange type formation.  
         [0017]    Two circumferential grooves  50  are provided on the cylindrical side wall  28 . A mounting bracket  52  extends from one end of the piston cooling jet housing  26  adjacent to the first end wall  30 . The circumferential grooves  50  receive O-rings (not shown). The cooling jets  40  are fitted into a cylinder block (not shown) of a reciprocating piston engine (not shown) in a manner that is known in the art by means of shafts in the cylinder block (not shown). The shafts extend perpendicular to the cylinders of the cylinder block (not shown). The piston cooling jets  22  are positioned in the shafts with the jet nozzles  38  directed toward the cylinders, one cooling jet  22  per shaft/cylinder. The piston cooling jets  22  are attached to the cylinder block by a bolt (not shown) that engages the mounting bracket  52 . The mounting bracket  52  aids in positioning the jet nozzle  38 , so the jet of coolant oil is directed at a desired location onto the underside of the reciprocating piston (not shown).  
         [0018]    The piston cooling jets  40  are fed with coolant oil by a supply cavity (not shown), bored through the cylinder block perpendicular to the shafts (not shown). The supply cavity and individual shafts are in fluid communication. The O-rings (not shown) ensure a seal to impede oil escaping from a circuit defined by the shafts, cavity and cooling jets  40 .  
         [0019]    Industrial Applicability  
         [0020]    One or more piston cooling jets  22  are provided within an internal combustion engine (not shown), generally one per cylinder. A supply of coolant oil is provided to the piston cooling jet  22  by the supply cavity (not shown) described above, the oil entering the fluid chamber  34  via the fluid inlet  44 . As described above, the coolant oil will generally be taken directly from the engine sump and can therefore be contaminated by impurities and particulates. As the fluid passes through the filter element  10 , the contaminants are reduced.  
         [0021]    The filter element  10  requires periodic replacement or cleaning to maintain the efficiency of the system. In order to effect replacement or cracking of the filter element  10 , the piston cooling jet  22  is first removed from the shaft in the cylinder block (not shown). When a filter element  10  is to be fitted onto the cooling jet  22 , the filter element  10  is initially in its unfitted rest position with an associated rest diameter D 1  as measured across its opposing ends (see FIG. 1). The opposing longitudinal edges  54 ,  56  are separated from each other by a rest spacing d 1  in the rest position. The rest position will be understood to include the state in which at least part of the opposing longitudinal edges  54 ,  56  may be in contact such that the rest spacing is zero. Where the opposing longitudinal edges  54 ,  56  are physically spaced apart in the rest position, the rest spacing d 1  will be smaller than the diameter or other minimum dimension of the perforations  14 , so that the filter element does not permit the passage between the opposing longitudinal edges  54 ,  56  of particulates having a size greater than the permissible particulate size.  
         [0022]    A torque is applied about axis  20  in the opposite direction to the direction of the filter element&#39;s helix to fit the filter element  10 . This expands the filter element  10  until its diameter reaches a fitting diameter D 2 , as measured across its opposing ends (see FIG. 2). It is to be understood that the torque in this case is assumed to be applied manually, but the application of torque may also be mechanized or otherwise automated. With the filter element  10  in its expanded fitting position, the opposing longitudinal edges  54 , 56  are spaced apart from each other by a fitting spacing d 2 , which will be understood to be greater than the rest spacing d 1 .  
         [0023]    The filter element  10  can then be placed over the cooling jet since its diameter will be sufficiently greater, and maneuvered between the first abutment  46  and the second abutment  48  over the cylindrical side wall  28 . The torque acting on the filter element  10  is then released and the filter element  10  returns to a fitted rest position with an associated fitted rest diameter D 3 , with the opposing ends  16 , 18  abutting against the first abutment  46  and second abutment  48 .  
         [0024]    It will be understood that the fitted rest position may be the same as the unfitted rest position, such that D 3 =D 1 . However, the diameter of the side wall  28  may be such that D 3  is slightly greater than D 1 , and the rest spacing d 3  in the rest position is greater than the rest spacing d 1  in the unfitted rest position. However, the rest spacing d 3  will be smaller than the diameter or other minimum dimension of the perforations  14 .  
         [0025]    When the filter element  10  is to be replaced or removed for cleaning, torque is once again applied to the filter element  10  to open it to its fitting diameter D 2 . The filter element  10  is then taken off the piston cooling jet  22 , and a new or a cleaned filter element  10  fitted in the manner mentioned above.  
         [0026]    It is to be understood that the invention is not limited to the embodiment described, but may be varied in both construction and detail. For example, it is envisaged that the filter element could be constructed from any suitable filter material and is not limited to a perforated metal strip. The filter material could be of resilient plastic and a woven or non-woven mesh material could be used instead of perforations.  
         [0027]    It is to be understood that even though the embodiments described herein relate particularly to piston cooling jet applications for internal combustion engines, the present invention could be applied to any appropriate fluid filtration system such as for example water filtration or air filtration.  
         [0028]    The fluid flow may also be reversed, the fluid inlet being within the tubular filter and the fluid flowing radially outward and across the filter.  
         [0029]    It is also to be understood that the invention is not limited to the embodiments hereinbefore described but may be modified in both construction and detail.