RELATED APPLICATION [0001] The present application claims the benefit of United States provisional application serial number 60/587,124 entitled "Replaceable Filter Element with Integral Annular Trap" filed July 12, 2004 which is incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to replaceable filter elements. Specifically, the present invention relates to an outside-in flow replaceable filter element with integral annular trap.

2. Background Information [0003] Hydraulic systems are frequently used in heavy machinery, including cranes, backhoes, demolition shears, bulldozers, and the like. In such hydraulic systems, it is important to keep the hydraulic fluid free of debris. Consequently, filter units or filter assemblies have been incorporated in the hydraulic systems to filter debris from the hydraulic fluid. Fuel systems and lubrication systems have also incorporated filter assemblies to clean the working fluid (with the fuel system being the only systems that do not typically re-circulate the working fluid).

[0004] It is common to form the filter assembly with a replaceable filter element. One common configuration is a tubular filter media in which the fluid being cleaned flows in a radial direction through the tubular pleated media. The direction of flow in such a structure defines the filter element as an outside-in (flow of fluid being cleaned is inward radial direction) or an inside-out (flow of fluid being cleaned is outward radial direction) filter structure. Examples of the tubular structure type filter elements include the K series element sold by Schroeder Industries, LLC, with the direction of flow for this element being defined by the associated assembly. From an operational standpoint there are certain advantages to outside-in flow and other advantages with inside-out flow. Namely with outside-in flow the pleat structure is more stable at higher pressure when constructed with a traditional fan pleat. This structure also exhibits higher dirt holding capacity as compared to similar inside out designs, since the media pleats are uniformly exposed to the system flow which results in a more uniform distributed deposition pattern. Alternatively with inside-out flow there is an advantage in that larger particles on the up-stream side of the filter remain in the center and are easily removed with the filter element, whereas in the outside in configurations such particles can, in theory, contaminate the system by falling or migrating past the filter location during filter element replacement. This contamination may occur after system flow stops which may allow particles on the outer most media layer to become dislodged and further contaminate the upstream fluid or settle within the filter housing. If this condition occurs and the element is removed from the filter housing (i.e. replacement of the filter element); the dislodged particles in the upstream fluid may contaminate the fluid downstream of the filter assembly.

[0005] There is a need in the industry for a simple, efficient, tubular filter element that combines the advantages of inside out-flow and outside-in flow.

SUMMARY OF THE INVENTION

[0006] The problems set out above are solved by an outside-in, tubular filter element with integral annular trap according to the present invention. The replaceable, outside-in flow filter element with integral annular trap provides a simple, efficient, tubular filter element that combines the advantages of inside out-flow and outside-in flow filters. The element includes an outlet end cap and an inlet end cap with a tubular support tube and pleated filter media extending there between. A solid tube is secured to the outlet end cap in a position spaced from the outer radial position of the pleated media. The annular space between the media and the tube forms an integral, lateral, outer trap for containing filtered out particulate matter. The trap allows the particulate, if any, to be removed with the old used filter element during conventional replacement of the filter element. [0007] These and other advantages of the present invention will be clarified in the description of the preferred embodiment taken together with the attached figures wherein like reference numerals represent like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] Fig. 1 is a sectional view of an outside-in flow, replaceable filter element with an integral annular trap according to a first embodiment of the present invention; [0009] Fig. 2 is a sectional view of an outside-in flow, replaceable filter element with an integral annular trap according to a second embodiment of the present invention; [0010] Fig. 3 is apian view of the inflow end of the filter element of Fig. 2; and [0011] Fig. 4 is an enlarged sectional view of an inflow end cap structure for the filter element of Fig. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0012] Fig. 1 is a schematic view of an outside-in flow, replaceable filter element 10 according to the present invention. The term "outside-in flow", or "outside-in" as well as "inside-out" within the meaning of this application refers to the radial direction of flow of the fluid being cleaned through the tubular media of the subject filter element. The filter element of the present invention is distinguished from a spin on a filter unit, as found in an automotive oil filter. These spin on filter units include the housing structure integral therewith sufficient to take the pressure load and form a closed filter housing. These spin on filter units can present disposal problems in many applications. The filter elements such as the present invention are made to be placed into existing filter housing or filter chamber. The outside-in structure means that the intended flow is from outside the tubular filter media to the inside of the tubular media.

[0013] The filter element 10 includes a solid, annular outlet end cap 12 with a retaining member 14, such as a standard O-ring retainer, attached thereto. The retaining member 14 is sized to seal onto a seating surface 16 of an outlet 18 for the filter assembly 20. The seal between the retaining member 14 and the seating surface 16 of the outlet 18 prevents the fluid to be cleaned from bypassing the filer media of the filter element 10. [0014] A center perforated support tube 22 is attached to and extends from the annular outlet end cap 12. A pleated, annular filter media 24 is bonded to end cap 12 surrounding and supported by the tube 22. The specific structure of the filter media 24 and the support tube 22 are generally known in the art and need no be described in detail herein.

[0015] An annular inlet end cap 26 with a retaining member 28 is attached to the filter media 24 and the support tube 22 at the opposed end of the filter element 10 from the outlet end cap 14. The retaining member 28 is sized to seal onto a seating surface 30 of a spring biased inlet end mount and bypass assembly 32. The spring biased inlet end mount is known in the art and includes a general bypass assembly. The seal between the retaining member 28 and the seating surface 30 of the assembly 32 prevents the fluid to be cleaned from bypassing the filer media 24 of the filter element 10, unless the bypass is activated. The bypass operates in a conventional manner as an emergency bypass. The bypass spring is set to a by-pass pressure. If the filter media 24 is close to reaching its capacity (i.e. it is clogged), the pressure in the upstream or inlet side will increase until it reaches the by-pass pressure of the spring. At the by-pass pressure the spring will be depressed allowing fluid to by-passes the filter media 24, as known in the art. Additionally the remaining elements of the header portion of the filter assembly 20 are known, including conventional inlet ports 33.

[0016] The filter element 10 according to the present invention further includes a solid tube 34 secured to the outlet end cap 14 in a position spaced from the outer radial position of the pleated media 24. The annular space between the media 24 and the tube 34 forms an integral, lateral, outer trap 36 for containing filtered out particulate matter. The tube 34 allows the particulate, if any, to be removed with the old used filter element 10 during conventional replacement of the filter element 10. The spacing between the media 24 and the tube 34 (i.e. the width of the trap 36) should be selected to avoid interference with the flow through the entire length of media 24. For example, for an outer radius of the media 24 of 4.3739 centimeters (1.722 inches), the tube will have an inner radius of about 5.2324 centimeters (2.06 inches), and prototypes of 5.2197 centimeters and 5.2578 centimeters (2.055 inches and 2.07 inches, respectively) have been designed.

[0017] The replaceable, outside-in flow filter element 10 with integral annular trap 36 provides a simple, efficient, tubular filter element that combines the advantages of inside out-flow and outside-in flow filters. In other words it is an outside in flow element which is designed to keep the sludge or particulate matter with the element during replacement thereof. There is no change in the filter operation or maintenance, although the present invention may be allowed to drain after removal to minimize the oil or fluid lost (or which needs to be disposed).

[0018] There are certainly various modifications to the filter element according to the present invention. Figures 2-4 illustrate an outside-in flow, replaceable filter element 110 with an integral annular trap 134 according to a second embodiment of the present invention. The filter element 110 is similar to the filter element 10 with the filter element 110 including a solid, annular outlet end cap 12 with a retaining member 14, a center perforated support tube 22, annular filter media 24, a solid tube 34, and an integral, lateral, outer trap 36 for containing filtered out particulate matter as discussed above in connection with filter element 10. The filter assembly 20 includes outlet 18 with seating surface 16, seating surface 30, assembly 32 and inlet ports 33 as discussed above in connection figure 1.

[0019] The filter element 110 differs from element 10 in that a three piece annular inlet end cap 126 with a retaining member 128 (as shown in Figure 4) is attached to the filter media 24 and the support tube 22 at the opposed end of the filter element 10 from the outlet end cap 14. The retaining member 128 is sized to seal onto a seating surface 30 of a spring biased inlet end mount and bypass assembly 32 as discussed above in connection with figure 1. Further, the end cap 126 is secured to the tube 38 as shown in figure 4. The attachment of the end cap 126 to the tube 38 provides stability to the trap 36 and the entire element 110. Openings or slots 130 are provided in the end cap 126, as shown in figure 3, to allow sufficient flow of fluid to be cleaned through the filter media 24. For example with the radii of the tube 34 and media 24 discussed above, the slots can have an area of 29.03 square centimeters to 32.26 square centimeters (4.5 to 5 square inches) to provide adequate flow.

[0020] The other advantage of the present invention will be apparent to those in the art. The invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the proceeding detailed description. For example, the tube 34 can have openings or holes in the end adjacent the inlet, or the tube may only extend partially toward the inlet end since these modifications would still form a trap for the particulates. It is intended that the invention be construed as including all such modifications and alterations.