EP3185980A1

EP3185980A1 - Filter cartridge interface

Info

Publication number: EP3185980A1
Application number: EP15821413.0A
Authority: EP
Inventors: Roma FATIMA; Mayur H. HOGADE; Zemin Jiang; Gwynn G. MEDLIN; Deeksha SHUKLA; Sreedevi KASTURI
Original assignee: Cummins Filtration IP Inc
Current assignee: Cummins Filtration IP Inc
Priority date: 2014-07-17
Filing date: 2015-07-14
Publication date: 2017-07-05
Also published as: CA2956397A1; WO2016010973A1; CN106804104A; EP3185980A4

Abstract

A filtration system for a lubrication system is described. The filtration system includes an open full flow filter element and a fine filter element connected by an insert. The full flow filter element provides low restriction and long life. The fine filter element provides high efficiency. The insert connects the full flow filter element and the fine filter element. Additionally, the insert seals the interfaces between the two filter elements. The insert is connected to two endplates - one from each filter element.

Description

FILTER CARTRIDGE INTERFACE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to India Provisional Patent Application No.

3508/CHE/2014, entitled "FILTER CARTRIDGE INTERFACE," filed on July 17, 2014, which is herein incorporated by reference in its entirety and for all purposes.

TECHNICAL FIELD

[0002] The present invention relates generally to lubrication filtration systems having two filter element cartridges.

BACKGROUND

[0003] An internal combustion engine typically includes a lubrication system that circulates a lubricant (e.g., oil) to the various components of the engine. The lubricant is recirculated throughout the engine during use. During recirculation, the lubricant may pick up dirt and debris from the components of the engine. Accordingly, many lubrication systems include a filtration system. The filtration system generally passes the lubricant through a filter element having a filter media. For maximum lubrication system performance, the filter element should provide low flow restriction, long life, and high efficiency. However, these ideal characteristics contradict with each other and are generally not achievable with a single filter element. For example, a high efficiency filter element (e.g., a filter element that captures a high percentage of dirt and debris) generally causes a higher than desired flow restriction. Accordingly, the use of a single filter element may not be able to provide the desired filter characteristics for a lubrication system.

SUMMARY

[0004] One embodiment relates to a filter unit. The filter unit includes a first filter cartridge having a first filter media positioned between a first endcap and a second endcap. The filter unit further includes a second filter cartridge having a second filter media positioned between a third endcap and a fourth endcap. The filter unit includes an insert positioned between the second endcap and the third endcap, thereby connecting the first filter cartridge and the second filter cartridge via a snap-fit connection.

[0005] Another embodiment relates to an insert for connecting two filter cartridges. The insert includes a cylindrical wall defining a central opening, a plurality of circumferential ridges on the cylindrical wall opposite of the central opening, an upper barb, and a lower barb. The insert further includes a first recess positioned between the upper barb and the plurality of

circumferential ridges. The insert includes a second recess positioned between the lower barb and the plurality of circumferential ridges.

[0006] These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0007] FIG. 1 is a perspective view of a filter cartridge is shown according to an exemplary embodiment.

[0008] FIGS. 2 and 3 are cross-sectional views of the filter cartridge of FIG. 1 assembled in a housing are shown.

[0009] FIG. 4 is a perspective view of the insert of FIG. 1. [0010] FIG. 5 is a top perspective view of the insert of FIG. 1. [0011] FIG. 6 is a cross-sectional view of the insert of FIG. 1.

[0012] FIG. 7 is a close-up cross-sectional view of the insert of FIG. 1 at section B as marked in FIG. 6.

[0013] FIG. 8 is a close-up cross-sectional view of the insert of FIG. 1 at section C as marked in FIG. 6.

[0014] FIG. 9 is a cross-sectional view of the insert of FIG. 1 connected to the endcaps. [0015] FIG. 10 is a perspective view of an endcap installed on the insert of FIG. 1.

[0016] FIG. 11 is a perspective view of two endcaps partially installed on the insert of FIG. 1.

[0017] FIGS. 12, 13, and 15-20 are views of specific configurations of inserts according to exemplary embodiments.

[0018] FIG. 14 is a graph of installation force required to install the insert of FIGS. 12 and 13.

[0019] FIG. 21 is a cross-sectional view of an insert according to an exemplary embodiment.

[0020] FIG. 22 is a graph of installation force required to install an insert.

[0021] FIG. 23 is a cross-sectional view of an insert is shown according to an exemplary embodiment.

[0022] FIG. 24 is a cross-sectional view of an insert is shown according to an exemplary embodiment.

DETAILED DESCRIPTION

[0023] Referring to the figures generally, a filtration system for a lubrication system is described. In some arrangements, the filtration system is used for the lubrication system of an internal combustion engine. The filtration system includes an open full flow filter element and a fine filter element connected by an insert. The full flow filter element provides low restriction and long life. The fine filter element provides high efficiency. Although both filter elements arranged in this manner will not filter the lubricant on a single pass, lubricant will ultimately flow through both filter elements due to the recirculation of the lubricant in the lubrication system. The insert connects (e.g., via a snap connection, a threaded spin-on connection, etc.) the full flow filter element and the fine filter element. Additionally, the insert seals the interfaces between the two filter elements. The insert is connected to two endplates - one from each filter element.

[0024] Referring to FIG. 1, a perspective view of a filter cartridge 100 is shown according to an exemplary embodiment. The filter cartridge 100 includes two filter elements: a first filter element 102 and a second filter element 104. The first filter element 102 includes a first filter media 106 positioned between a first endcap 108 and a second endcap 110. The second filter element 104 includes a second filter media 112 positioned between a third endcap 114 and a fourth endcap 116. The endcaps 108, 110, 114, and 116 may be composite endcaps. In some arrangements, the first filter media 106 is an open full flow filter media, and the second filter media 112 is a fine filter media. As shown in FIG. 1, the first filter element 102 has a longer axial length than the second filter element 104. Accordingly, there the first filter media 106 has a larger surface area than the second filter media 112. In alternative arrangements, the first filter element 102 has the same or a shorter axial length as the second filter element 104.

[0025] Referring to FIGS. 2 and 3, cross-sectional views of an assembled filter unit 200 including the filter cartridge 100 received in an installed position within a housing 202 are shown. The first filter element 102 is coupled to the second filter element 104 through an insert 204 positioned between the second endcap 110 and the third endcap 114. The filter cartridge 100 is positioned between a support spring 204 at a closed base of the housing 202 and a nutplate 206 at an open top of the housing 202. The top of the housing 202 includes a receiving channel 208 that retains the nutplate 206 in position. A lower seal 210 is positioned between the nutplate 206 and the first endcap 108. An upper seal 212 is positioned at the top of the housing 202. The upper seal 212 is retained by a lip in the housing 202 that forms the receiving channel 208. The nutplate 206 includes internal threading 214 such that the filter unit 200 can be attached to mating external threading of a filter head (not shown).

[0026] Each of the endcaps 108, 110, 114, and 116 are sealed across the corresponding ends of filter elements 106 and 112 in order to prevent lubricant flow out through the ends of the filter elements 106 and 112. The first endcap 108 is an open endcap such that a portion of the lower seal 210 can wrap around a portion of the first endcap 108. The second endcap 110 and the third endcap 114 are open endcaps and are removably coupled to the insert 204 thereby connecting the first filter element 106 to the second filter element 112. The second endcap 110 and the third endcap 114 each form a snap-fit connection with the insert 204. The snap-fit connection also seals an inner surface of each endcap to an outer surface of the insert 204 as described in further detail below. The second endcap 110 and the third endcap 114 may each have a lip that extends over the insert 204. In an alternative arrangement, the second endcap 110 and the third endcap 114 are internally threaded such that the internal threads mate with external threads on the insert 204. The fourth endcap 204 is a closed endcap.

[0027] When the filter unit 200 is affixed to the filter head, lubricant to be filtered flows along the path designated by the arrows in FIG. 2. Accordingly, lubricant flows through openings in the nutplate 206 into a cavity 216 formed between the housing 202 and the dirty side of the filter elements 106 and 112. The lubricant then passes through the filter elements 106 and 112 and out of the housing through a central opening 218 in the lower seal 210 such that filtered lubricant flows back into the filter head for recirculation.

[0028] Referring to FIGS. 4 through 9, additional views of the insert 204 are shown. FIG. 4 shows a perspective view of the insert 204. FIG. 5 shows a top perspective view of the insert 204. FIG. 6 shows a cross-sectional view of the insert 204. FIG. 7 shows a close-up cross-sectional view of the insert 204 at section B. FIG. 8 shows a close-up cross-sectional view of the insert 204 at section C. FIG. 9 shows a cross-sectional view of the insert 204 when connected to the second endcap 110 and the third endcap 114.

[0029] The insert 204 includes a cylindrical opening 402. The cylindrical opening 402 provides a flow path for clean lubricant between the first filter element 102 and the second filter element 104. The cylindrical opening 402 is formed by a cylindrical wall 404. The cylindrical wall 404 provides column strength for the filter cartridge 100 formed by the coupling of the first filter element 102 and the second filter element 104 by the insert 204. When connected to the first and second filter elements 102 and 104 (e.g., as shown in FIG. 2), the insert aligns the first and second filter elements 102 and 104 for proper positioning within the housing 202. Additionally, the spring force provided by spring 204 assists in keeping the first and second filter elements 102 and 104 compressed (e.g., to keep the filter elements 102 and 104 connected) post assembly onto the insert 204.

[0030] The insert 204 includes a plurality of circumferential ridges 406 formed on the outside of the cylindrical wall 404 (the opposite side of the cylindrical wall 404 than the opening 402). The plurality of circumferential ridges 406 function as sealing rings between the insert 204 and the inner surfaces of the endcaps 110 and 114 (e.g., as shown in FIG. 9). In some arrangements, the plurality of circumferential ridges 406 engage with detents on the inner surfaces of the endcaps 110 and 114 to form the seals and to assist with the snap-fit connections between the insert 204 and the endcaps 110 and 114 to connect and lock together the first and second filter elements 102 and 104. In other arrangements, the ridges 406 are angled to form external threading on the cylindrical wall 404. In such arrangements, the endcaps 110 and 114 may have mating threading such that the endcaps 110 and 114 can be spun-on to the insert 204 to connect and seal the first and second filter elements 102 and 104.

[0031] Still referring to FIGS. 4 through 9, the insert 204 includes opposing circumferential recesses 602 and 604. Each of the recesses 602 and 604 are formed in the cylindrical wall 404 between the plurality of circumferential ridges 406 and upper and lower barbs 606 and 608. The plurality of circumferential ridges 406 extend a greater distance from a surface of the cylindrical wall 404 than the upper and lower barbs 606 and 608. The opposing circumferential recesses 602 and 604 are positioned along opposite ends of the cylindrical wall 404. The plurality of circumferential ridges 406 are positioned between the opposing circumferential recesses 602 and 604. As shown in FIG. 9, the first circumferential recess 602 receives a portion 902 of the second endcap 110 when the second endcap 110 is connected to the insert 204. The second

circumferential recess 604 receives a portion 904 of the third endcap 114 when the third endcap 114 is connected to the insert 204. The portions 902 and 904 of the endcaps 110 and 114 are retained in the circumferential recesses 604 by the barbs 606 and 608. The circumferential recesses 602 and 604 and the barbs 606 and 608 receive the portions 902 and 904 of the endcaps 110 and 114 to form snap-fit connections between the insert 204 and the endcaps 110 and 114.

[0032] The connection formed between the first filter element 102, the second filter element 104, and the insert 204 provides a seal between the first filter element 102 and the second filter element 104 through the circumferential ridges 406. In effect, two seals are formed between the insert 204 and each of the endcaps 110 and 114 through the pairs of circumferential ridges 406. The seal formed eliminates the need for an additional seal member or adhesive (e.g., glue or epoxy) at the interface, thereby avoiding the risk of the adhesive or seal releasing downstream and causing issues within the lubrication system. The seal is achieved through interaction between the circumferential ridges 406 and the endcaps 110 and 114.

[0033] FIG. 10 shows a perspective view of the third endcap 114 at least partially installed on the insert 204. FIG. 11 shows a perspective view of the third endcap 114 and the second endcap 110 partially installed on the insert 204. When the second and third endcaps 110 and 114 are fully installed on the insert 204, the gap between the second and third endcaps 110 and 114 is minimized.

[0034] The above-described insert 204 may be constructed entirely or substantially out of metal, plastic, epoxy, plastisol, or another suitable material. The insert 204 may be manufactured using an existing manufacturing process to avoid new machine and tooling costs. The material of the insert 204 does not deteriorate under fluid conditions during use of the filter unit 200.

Additionally, because the insert 204 connects the first and second filter elements 102 and 104 and forms a seal without additional components, the first and second filter elements 102 and 104 may be produced on the regular spin-on production line, reducing manufacturing costs and tooling time. Alternatively, the first and second filter elements 102 and 104 are modular filter elements.

[0035] The above-described insert 204 can utilize different shaped circumferential ridges 406 to achieve different sealing characteristics against the portions 902 and 904 of the endcaps 110 and 114. As described below with respect to FIGS. 12-20, various specific configurations for the insert 204 are described.

[0036] Referring to FIGS. 12 and 13, a cross-sectional view and a side view of an insert 1200 are shown according to an example embodiment. The insert 1200 is generally of the same shape and configuration of the insert 204. As described above with respect to the insert 204, the insert 1200 can be used to connect the first filter element 102 to the second filter element 104 while providing a flow path for clean lubricant between the first filter element 102 and the second filter element 104. The significant difference between the insert 204 and the insert 1200 is that the insert 1200 has a different circumferential ridge arrangement. The insert 1200 includes four circumferential ridges 1202. Each of the circumferential ridges 1202 has a generally triangular shape (i.e., saw-tooth shape). Each of the circumferential ridges 1202 extends a height 1204 from an outer wall 1206 of the insert 1200. The insert 1200 has a thickness 1208 between a cylindrical opening 1210 (e.g., similar to the cylindrical opening 402 of the insert 204) and the outer wall 1206. Each of the circumferential ridges 1202 has a total ridge height 1212 from a central axis 1214 of the insert 1200. In some arrangements, the uppermost pair of ridges has a total ridge height of 51.69mm, and the lowermost pair of ridges has a total ridge height of 51.8mm. In such arrangements, the distance 1302 between adjacent ridges 1202 is 3mm, and the distance 1304 between the uppermost ridge or the lowermost ridge and the hard stop 1306 is 3mm.

[0037] As noted above, the insert 1200 is manufactured to have an uneven thickness across the circumferential ridges 1202. The circumferential ridges 1202 are designed to sustain a seal under a pressure differential of 200 psi (e.g., 300 psi of clean-side fluid pressure and lOOpsi of dirty-side fluid pressure). However, the relatively short height 1204 of each ridge provides for a high ridge stiffness. The high ridge stiffness requires a high installation force. The high installation force may cause yielding at the portions 902 and 904 of the endcaps 110 and 114 beyond the yield strength of the endcaps 110 and 114 during installation. FIG. 14 shows a graph 1400 of installation force required during installation of the first filter element 102 and second filter element 104 onto the insert 1200. As shown in the graph 1400, an installation force of

approximately 45 ON is needed to install the first and second filter elements 102 and 104 onto the insert 1200, which causes yielding of the endplates 110 and 114 due to the high radial force caused by the circumferential ridges 1202.

[0038] Referring to FIGS. 15 and 16, cross-sectional views of an insert 1500 are shown according to an example embodiment. The insert 1500 is generally of the same shape and configuration of the insert 204 and the insert 1200. As described above with respect to the inserts 204 and 1200, the insert 1500 can be used to connect the first filter element 102 to the second filter element 104 while providing a flow path for clean lubricant between the first filter element 102 and the second filter element 104. The significant difference between the inserts 204 and 1200 and the insert 1500 is that the insert 1500 has a different circumferential ridge arrangement. The insert 1500 includes four circumferential ridges 1502 of a similar shape to the circumferential ridges 1202 of the insert 1200. However, a thickness 1504 of the insert 1500 is smaller than the thickness 1208 of the insert 1200. The smaller thickness 1504 helps to avoid plastic manufacturing defects. In some arrangements, a total ridge height 1602 for the uppermost pair of ridges 1502 is 51mm, and a total ridge height 1604 for the lowermost pair of ridges 1504 is 51.1mm. In such arrangements, the distance 1606 between adjacent ridges 1502 is 3mm, and the distance 1608 between the uppermost ridge or the lowermost ridge and the hard stop 1610 is 3mm. The smaller thickness 1504 results in the insert 1500 having ridges 1502 with a height 1506 greater than the height 1208 of the ridges 1202 of the insert 1200. The larger height 1506 results in the insert 1500 having more flexible circumferential ridges 1502 than the insert 1200, which results in a lower required installation force compared to the insert 1200. However, the more flexible circumferential ridges 1502 create a weaker seal against the endplates 110 and 114 than the circumferential ridges 1202 of the insert 1200.

[0039] Referring to FIGS. 17 and 18, cross-sectional views of an insert 1700 are shown according to another example embodiment. The insert 1700 is generally of the same shape and configuration of the above-described inserts 204, 1200, and 1500. As described above with respect to the inserts 204 1200, and 1500, the insert 1700 can be used to connect the first filter element 102 to the second filter element 104 while providing a flow path for clean lubricant between the first filter element 102 and the second filter element 104. The significant difference between the inserts 204, 1200, and 1500 and the insert 1700 is that the insert 1700 has a different circumferential ridge arrangement. The insert 1700 includes four circumferential ridges 1702 having a trapezoidal shape. The trapezoidal shape provides a better seal between the

circumferential ridges 1702 and the endplates 110 and 114 than the triangular or saw-tooth shape ridges of inserts 1200 and 1500. In some arrangements, a total ridge height 1802 for the uppermost pair of ridges 1702 is 51.15mm, and a total ridge height 1804 for the lowermost pair of ridges 1702 is 51.2mm. In such arrangements, the distance 1806 between adjacent ridges 1702 is 3mm, and the distance 1808 between the uppermost ridge or the lowermost ridge and the hard stop 1810 is 3mm. The described arrangement can provide a seal between the insert 1700 and the endplates 110 and 114 up to 150 psi.

[0040] Referring to FIGS. 19 and 20, cross-sectional views of an insert 1900 are shown according to still another example embodiment. The insert 1900 is generally of the same shape and configuration of the above-described inserts 204, 1200, 1500, and 1700. As described above with respect to the inserts 204 1200, 1500, and 1700, the insert 1900 can be used to connect the first filter element 102 to the second filter element 104 while providing a flow path for clean lubricant between the first filter element 102 and the second filter element 104. The significant difference between the inserts 204, 1200, 1500, and 1700 and the insert 1900 is that the insert 1900 has a different circumferential ridge arrangement. The insert 1900 includes four

circumferential ridges 1902 having a trapezoidal shape. As noted above, the trapezoidal shape provides a better seal between the circumferential ridges 1902 and the endplates 110 and 114 than the triangular or saw-tooth shape ridges of inserts 1200 and 1500. In some arrangements, a total ridge height 2002 for the uppermost pair of ridges 1902 is 51.15mm, and a total ridge height 2004 for the lowermost pair of ridges 1902 is 51.3mm. In such arrangements, the distance 2006 between adjacent ridges 1902 is 3.5mm, and the distance 2008 between the uppermost ridge or the lowermost ridge and the hard stop 2010 is 1.5mm. The described arrangement can provide a seal between the insert 1700 and the endplates 110 and 114 up to 200 psi (e.g., e.g., 500 psi of clean- side fluid pressure and 200 psi of dirty-side fluid pressure).

[0041] Referring to FIG. 21, a cross-sectional view of a representative insert 2100 is shown according to an example embodiment. Insert 2100 is used to describe various insert optimization parameters. Insert 2100 is of a similar arrangement to the above-described inserts 204, 1200, 1500, 1700, and 1900. Accordingly, insert 211 includes four circumferential ridges 2102 and a central cylindrical opening 1204. The circumferential ridges 2102 are arranged in an upper ridge pair 2106 having an outer ridge 2106o and an inner ridge 2106i, and a lower ridge pair 2108 having an inner ridge 2108i and an outer ridge 2108o. In this arrangement, the outer ridges are positioned axially closer to the opening of the cylindrical opening 1204, and the inner ridges are positioned axially further from the opening of the cylindrical opening 1204. LI is the distance between an outer ridge and a corresponding hard stop 2110. L2 is a distance between the outer ridge and the inner ridge of a given pair of ridges. Based on the distance parameters LI and L2, the function of the insert 2100 can be optimized as set forth below in Table 1.

LI (mm) L2 (mm) Diameter difference range (mm)

2.5 1.5 0.1-0.25

2.5 2 0.1-0.25

2.5 2.5 0.1-0.3

2 2.5 0.1-0.35 1.5 2.5 0.1-0.4

Table 1

[0042] As set forth above, the final row of Table 1 corresponds to insert 1900. If the diameter difference of a given insert is not within the specified range of Table 1, the circumferential ridges of the insert will lose contact with the endplates 110 and 114 due to the draft on the endplates 110 and 114. When the circumferential ridges lose contact with the endplates 110 and 114, a leak path is provided for dirty fluid to bypass the filter elements 102 and 104.

[0043] Referring to FIG. 22, a graph 2200 of installation force required is shown for various insert arrangements. As shown in the graph 2200, the larger the circumferential ridge ("tooth") displacement required for installation, the higher the installation force required. Additionally, the larger width circumferential ridges require higher installation forces than narrow width

circumferential ridges.

[0044] Referring to FIG. 23, a cross-sectional view of an insert 2300 is shown according to another exemplary embodiment. The insert 2300 is similar to the insert 204. The insert 2300 an inner wall 2302 forming a central opening 2304. The insert 2300 includes an axial extension 2306 connecting the inner wall 2302 and an outer wall 2308. The spaces between the inner wall 2302 and the outer wall 2308 form two separate channels 2310 and 2312 separated by the axial extension 2306. The upper channel 2310 receives first filter media 2314 and the lower channel 2312 receives second filter media 2316. The first filter media 2314 is an open full flow filter media. The second filter media 2316 is a fine filter media. The first and second filter medias 2314 and 2316 are secured in the respective channels 2310 and 2312 through the use of epoxy.

[0045] Referring to FIG. 24, a cross-sectional view of an insert 2400 is shown according to still another exemplary embodiment. The insert 2400 is similar to the insert 1200. The insert 2400 includes an inner wall 2402 forming a central opening 2404. The insert 2400 includes a plastic bottom endplate 2406 having a skirt forming a channel 2408. A flat seal 2410 is positioned along the plastic bottom endplate 2406 opposite the channel 2408. The flat seal 2410 abuts a bottom endcap 2412 of a first filter element having a first filter media 2414. A second filter media 2416 is received in the channel 2408. The first filter media 2414 is an open full flow filter media. The second filter media 2416 is a fine filter media.

[0046] As utilized herein, the terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0047] It should be noted that the term "exemplary" or "example" as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

[0048] The terms "coupled," "connected," and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0049] References herein to the positions of elements (e.g., "top," "bottom," "above," "below," etc.) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary

embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0050] It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A filter unit comprising:

a first filter cartridge including a first filter media positioned between a first endcap and a second endcap;

a second filter cartridge including a second filter media positioned between a third endcap and a fourth endcap;

an insert positioned between the second endcap and the third endcap, the insert connecting the first filter cartridge and the second filter cartridge via a snap-fit connection.

2. The filter unit of claim 1, wherein the insert includes a plurality of circumferential ridges, at least a first of the plurality of circumferential ridges engaging an inner surface of the second endcap and creating a first seal between the insert and the second endcap, at least a second of the plurality of circumferential ridges engaging, an inner surface of the third endcap and creating a second seal between the insert and the third endcap.

3. The filter unit of claim 2, wherein the insert includes a cylindrical opening that provides a flow path between the first filter cartridge and the second filter cartridge.

4. The filter unit of claim 2, wherein the first plurality of circumferential ridges engage detents on the inner surface of the second endcap.

5. The filter unit of claim 4, wherein the second plurality of circumferential ridges engage detents on the inner surface of the third endcap.

6. The filter unit of claim 2, wherein the insert includes opposing circumferential recesses formed in a cylindrical wall of the insert and positioned between the plurality of circumferential ridges and upper and lower barbs.

7. The filter unit of claim 6, wherein the opposing circumferential recesses and the upper and lower barbs interact with the second and third endcaps to create the snap-fit connection.

8. The filter unit of claim 2, wherein the plurality of circumferential ridges each have a trapezoidal shape.

9. The filter unit of claim 1, wherein the first filter cartridge has a longer axial length than the second filter cartridge.

10. An insert for connecting two filter cartridges, the insert comprising:

a cylindrical wall defining a central opening;

a plurality of circumferential ridges on the cylindrical wall opposite of the central opening;

an upper barb;

a lower barb;

a first recess positioned between the upper barb and the plurality of circumferential ridges; and

a second recess positioned between the lower barb and the plurality of circumferential ridges.

11. The insert of claim 10, wherein the plurality of circumferential ridges extend a greater distance from a surface of the cylindrical wall than the upper barb and the lower barb.

12. The insert of claim 10, wherein the plurality of circumferential ridges each have a trapezoidal shape.

13. The insert of claim 10, wherein the plurality of circumferential ridges are positioned between the first recess and the second recess.

14. The insert of claim 10, wherein a first pair of the circumferential ridges has a greater height than a second pair of the circumferential ridges.