Patent Publication Number: US-10307704-B2

Title: Air cleaner; replaceable filter cartridges; and, methods

Description:
REFERENCE TO RELATED FILINGS 
     This application is a continuing application of U.S. Ser. No. 14/257,539, filed Apr. 21, 2014, now U.S. Pat. No. 9,039,802. U.S. Ser. No. 14/257,539 is a continuation of U.S. Ser. No. 13/793,006, filed Mar. 11, 2013, which issued as U.S. Pat. No. 8,702,831. U.S. Ser. No. 13/793,006 is a continuation of U.S. Ser. No. 13/544,118, filed Jul. 9, 2012, which has issued as U.S. Pat. No. 8,394,166. U.S. Ser. No. 13/544,118 was a continuing filing of U.S. Ser. No. 11/661,011, filed Feb. 22, 2007 as a US National Stage of PCT/US2005/029830, filed on Aug. 24, 2005 and having a claim of priority to U.S. Ser. No. 60/604,554, filed Aug. 25, 2004 and U.S. Ser. No. 60/677,031, filed May 3, 2005. The complete disclosures of U.S. Ser. Nos. 14/257,539; 13/793,006; U.S. Ser. No. 13/544,118; U.S. Ser. No. 11/661,011; PCT/US2005/029830; U.S. Ser. No. 60/604,554 and U.S. Ser. No. 60/677,031 are incorporated herein by reference. A claim of priority is made to each of U.S. Ser. Nos. 14/257,539; 13/793,006; U.S. Ser. No. 13/544,118; U.S. Ser. No. 11/661,011; PCT/US2005/029830; U.S. 60/604,554; and, U.S. 60/677,031 to the extent appropriate. 
     Selected portions of the following descriptions are found in one or both of the following two documents filed in the United States: Provisional Application No. 60/421,882 filed Oct. 28, 2002; and U.S. Provisional Application No. 60/453,737 filed Mar. 6, 2003. Each of these two identified provisional applications, is incorporated herein by reference. 
     Also, selected portions of the following descriptions are contained in U.S. application Ser. No. 10/691,856, filed Oct. 23, 2003 and published Jul. 15, 2004 as US 2004/0314171; and PCT Application US 03/33952, filed Oct. 23, 2003 and published May 13, 2004 as WO 04/039476. The complete disclosures of each of these is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure concerns air cleaners with removable and replaceable (i.e., serviceable) filter cartridges. The particular arrangements disclosed use a first stage separator or precleaner, to facilitate operation. Methods of assembly and use are also provided. 
     BACKGROUND 
     Air filtering is used in a variety of arrangements. A typical application is as an air cleaner for intake air to internal combustion engines. After a period of use, filter media within the cleaner requires servicing, either through cleaning or complete replacement. Typically, for an air cleaner used with an internal combustion engine such as on a vehicle, filter media is contained in a removable or replaceable (i.e., serviceable) component, element or cartridge. Examples are shown in U.S. Pat. Nos. 4,211,543; 4,135,899; 3,672,130; B1 5,445,241; 5,700,304; 6,051,042; 6,039,778; 5,547,480; 5,755,842; and U.S. Pat. No. 5,800,581; and PCT publication WO 89/01818; the complete disclosures of all of these references being incorporated herein by reference. U.S. application Ser. No. 09/729,033 filed Dec. 4, 2000 also shows such an element, with a unique interaction shown between the element and an end cover. The disclosure of the Ser. No. 09/729,033 application is also incorporated herein by reference. 
     Improvements in filter arrangements relating to assembly and use, are desirable. 
     SUMMARY 
     The present disclosure concerns features of air cleaners. The techniques described are particularly developed for use with air cleaners for cleaning engine air intake for an internal combustion engine, such as used with a vehicle such as a bus, truck or mobile equipment such as a tractor or construction equipment, or a stationary generator. The features generally relate to air cleaners in which filter media is part of a removable and replaceable (i.e., serviceable) component. 
     A number of improvements were brought forward in earlier U.S. application Ser. No. 10/691,856 filed Oct. 23, 2003 and PCT Application US 03/33952, filed Oct. 23, 2003 and figures and embodiments depicting examples of the various arrangements described in those filings, are provided herein. The present disclosure relates to application certain of the techniques and features described in U.S. application Ser. No. 10/691,856 and US application Ser. No. 03/33,952, in alternate specific, advantageous, forms for certain uses. It is noted that it is not necessary that all of the possible features described herein for an air cleaner system or component, be used in arrangements obtaining advantage according to the present descriptions. 
     SUMMARY OF THE RELATED PATENT FILINGS 
     Many of the improvements described in U.S. application Ser. No. 10/691,856 and PCT US 03/33952 relate to unique possible constructions of primary filter element cartridges. Examples of these optional improvements, described in detail below, include:
         1a. An improved construction that, among other things, allows optional use of an outer support in the primary filter cartridge; and, no inner support that extends the entire length of the element, for pleated media;   2a. Improved constructions relating to a manner in which the primary filter cartridge is secured to, and is sealed to, an air cleaner housing;   3a. An improvement in an outer support framework of such a cartridge, relating to: (a) a shielded area for use in connection with a dust evacuator; and, (b) a porous area, for permitting air flow to the media in a preferred manner;   4a. An improved shape, to accommodate certain housing features;   5a. An improved interlock at a closed end of the filter, to inhibit rotational movement of the filter during use; and   6a. Improvement in an outer framework structure to facilitate cartridge manufacture and assembly.       

     Optional improvements provided in U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952 also relate to structure circumscribed by the primary filter cartridge during use. Some of these optional improvements relate, for example, to the following:
         1b. A preferred support, separately mountable within the air cleaner assembly from the primary filter cartridge, to operate as an inner support for pleated media;   2b. Optional incorporation of the support identified at 1b above, as a support, for example as an outer support, for a preferred safety filter cartridge;   3b. Improved and advantageous arrangements for securing the support and/or secondary filter cartridge to an air cleaner housing;   4b. An improved optional interaction between inner and outer liners of a safety element cartridge; and,   5b. An optional improved shape/fit relation between a safety element or inner support, and a primary filter cartridge.       

     In addition, improvements described in U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952 were provided with respect to an air cleaner housing. Some of the improvements, for example, relate to the following:
         1c. Features in the housing to facilitate preferred independent mounting of a primary filter cartridge and inner support (or optional safety filter cartridge);   2c. An optional jointed housing sidewall, to permit change in orientation of housing components, such as an inlet angular orientation relative to a dust flow outlet;   3c. Preferred locations of inlet, outlet and dust ejector tubes;   4c. An improved optional end cover mountable through a non-rotational lock fit arrangement that does not necessarily require added latches or similar constructions;   5c. An improved precleaner arrangement optionally secured to an end cover;   6c. An improved, optional, cover which is mounted circumscribed by a portion of the housing, as opposed to having a portion of the cover overlapping a portion of the housing;   7c. An improved, optional, rotational, indexing between the cover and the housing; and,   8c. A cover which can include an improved member of a projection/receiver mechanism, to inhibit undesired rotation of an associated primary filter cartridge, during use.       

     In U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952, improvements in a housing end cover, associated with an air cleaner housing sidewall, were also provided. Some of these optional improvements, for example, related to the following:
         1d. Provision of a closed end cover which optionally includes a precleaner permanently mounted thereon;   2d. A closed end cover with an optional integrally molded latch mechanism for non-rotational engagement with a housing sidewall, during use;   3d. A particular optional flexible tab/latch mechanism engageable with an end cover through a tongue/slot interference fit;   4d. An improved, optional, indexing arrangement for securing an end cover to a housing sidewall;   5d. An improved, optional, mounting arrangement in which an end cover is mounted with a portion of the housing sidewall circumscribing the end cover and without a portion of the end cover circumscribing the housing sidewall; and   6d. An improved, optional, interlock arrangement on the end cover, for engaging a portion of an associated primary filter cartridge, in use.       

     Also provided in U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952 were improvements in use. 
     From the detailed discussion of U.S. application Ser. No. 10/691,856 and PCT Application US 03/39952, it would be apparent that the preferred components can be configured to facilitate manufacture and assembly. Examples of some of these optional improvements include the following:
         1e. An improved, optional, outer support for a primary filter cartridge that facilitates manufacture;   2e Preferred optional housing components, including features as described above, in configurations that can be readily manufactured using plastics molding techniques;   3e. Preferred optional techniques of mounting and sealing a primary filter cartridge in a housing;   4e. Preferred optional techniques of mounting and sealing a secondary filter or safety filter cartridge, in a housing; and,   5e. Improved and preferred, optional, techniques for supporting media in a primary filter cartridge.   6e. Improved and preferred (optional) techniques for supporting media in a secondary or safety filter cartridge.       

     Specific examples of features that provide for the above, are shown in certain of the drawings and are described in the detailed description below. In general, individual ones are usable, to provide improvement. In the arrangements depicted, selected one of the various features are coordinated together, in a unique, improved, air cleaners and in unique air cleaner componentry arrangements. 
     In this application,  FIGS. 34-47  depict new air cleaner, primary filter cartridge and safety filter cartridge options, distinguishable from, and in part using certain of the principles characterized in, U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952, applied in a different specific combination and arrangement, for different specific advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS.  1 - 33 , from U.S. Application Ser. No. 10/691,856, Filed Oct. 23, 2003 and PCT Application US 03/39952, Filed Oct. 23, 2003 
         FIG. 1  is a side perspective view of a filter assembly according to the present identified disclosures; 
         FIG. 2  is an exploded perspective view showing removable componentry, from the assembly of  FIG. 1 ; 
         FIG. 3  is a side cross-sectional view of the assembly of  FIGS. 1-2  depicted without a removable dust evacuator valve; 
         FIG. 4  is an enlarged, exploded, fragmentary outside perspective view of an end cover component and a primary filter cartridge, of the assembly of  FIG. 1 ; 
         FIG. 5  is an enlarged, exploded inside perspective view of the components depicted in  FIG. 4 ; 
         FIG. 6  is a side elevational view of a primary filter cartridge component of the assembly of  FIG. 1 ; 
         FIG. 7  is an end view of the filter cartridge depicted in  FIG. 6  looking toward end  58 ; 
         FIG. 8  is a perspective view of a component of the filter cartridge depicted in  FIGS. 6-7 ; 
         FIG. 9  is an end elevational view of a housing component of the assembly depicted in  FIG. 1 , shown with an end cover component removed and with certain internal componentry viewable; 
         FIG. 10  is a side cross-sectional view of the housing component of  FIG. 9  taken generally along line  10 - 10 ,  FIG. 9 ; 
         FIG. 11  is a side elevational view of a safety element component of the assembly of  FIG. 1 ; 
         FIG. 12  is a side cross-sectional view of the safety element component of  FIG. 11  taken along line  12 - 12 ,  FIG. 11 ; 
         FIG. 13  is an exploded view of the safety element component of  FIG. 11 ; 
         FIG. 14  is a side perspective view of an alternate embodiment of an air cleaner according to the identified disclosures; 
         FIG. 15  is a fragmentary, perspective, view of a second alternate embodiment of an air cleaner according to the identified disclosures; 
         FIG. 16  is an end view of a portion of a third alternate embodiment of an air cleaner according to the identified disclosures; 
         FIG. 17  is a side, cross-sectional view taken generally along line  17 - 17 ,  FIG. 16 ; 
         FIG. 18  is an enlarged, fragmentary view of a portion of the arrangement shown in  FIG. 17 , with a safety element mounted therein; 
         FIG. 19  is a perspective view of a fourth alternate embodiment of an air cleaner according to the identified disclosures; 
         FIG. 20  is a fragmentary, perspective view of a portion of an alternate primary element usable in an air cleaner according to the identified disclosures; 
         FIG. 21  is a fragmentary, cross-sectional view of an alternate primary filter element according to the identified disclosures; 
         FIG. 22  is a perspective view of a further alternate air cleaner housing according to the identified disclosures; and, 
         FIG. 23  is a fragmentary, cross-sectional view of a portion of  FIG. 22 . 
         FIG. 24  is a schematic, perspective view of a further alternate air cleaner according to the identified disclosures. 
         FIG. 25  is an exploded, schematic, perspective view depicting a cover member and a primary air filter element cartridge of the assembly of  FIG. 24 . 
         FIG. 26  is a side elevational view of the primary filter element cartridge depicted in  FIG. 25 . 
         FIG. 27  is a side, cross-sectional view of the assembly depicted in  FIG. 24 . 
         FIG. 28  is an inlet end perspective view of further embodiment of an air cleaner according to the identified disclosures. 
         FIG. 29  is an exploded perspective view of the arrangement depicted in  FIG. 28 . 
         FIG. 30  is a perspective view of two of the components depicted in  FIG. 29 , from a view point toward an inside surface of an inlet end cover. 
         FIG. 31  is a side, cross-sectional view of the assembly depicted in  FIG. 28 . 
         FIG. 32  is a side elevational view of primary filter element component usable in the assembly of  FIGS. 28-31 . 
         FIG. 33  is a perspective view of an outer framework component useable in the primary filter element depicted in  FIG. 32 . 
       FIGS.  34 - 38  from U.S. Provisional 60/604,554 Filed Aug. 25, 2004 
         FIG. 34  is a cross-sectional view of an air cleaner arrangement having a main filter element and secondary filter element mounted therein, according to the present disclosure. 
         FIG. 35  is a side elevational, partially cross-sectional, view of the main filter cartridge used in the air cleaner of  FIG. 34 . 
         FIG. 36  is an end view of a closed end cap of the filter cartridge of  FIG. 35 ;  FIG. 36  the cross-section lines indicating the portion sectioned in  FIG. 35 . 
         FIG. 37  is a side elevational view of the safety element depicted in the air cleaner of  FIG. 34 ; in  FIG. 37  a portion being shown in sectional view. 
         FIG. 38  is an end view of the open end of the filter cartridge of  FIG. 37 ; the cross-section line indicating the section of  FIG. 37 . 
       New FIGS.  39 - 47   
         FIG. 39  is a cross-sectional view of an air cleaner arrangement having a main filter element and secondary filter element therein, according to a further embodiment of the present disclosure. 
         FIG. 39A  is an enlarged fragmentary view of a portion of  FIG. 39 . 
         FIG. 40  is an enlarged end view of the air cleaner arrangement depicted in  FIG. 39 . 
         FIG. 41  is a cross-sectional view of a main filter cartridge used in the air cleaner arrangement of  FIG. 39 . 
         FIG. 41A  is an enlarged side elevational view of the filter cartridge depicted in  FIG. 41 , useable in the air cleaner arrangement of  FIG. 39 . 
         FIG. 42  is an end view of the filter cartridge depicted in  FIG. 41 . 
         FIG. 43  is a cross-sectional view of a secondary or safety filter cartridge used in the air cleaner arrangement of  FIG. 39 . 
         FIG. 43A  is a side elevational view of the filter cartridge depicted in  FIG. 43 . 
         FIG. 44  is an end view of the secondary filter cartridge depicted in  FIG. 43 . 
         FIG. 45  is a schematic isometric view toward an outlet end of the filter cartridge depicted in  FIG. 41 . 
         FIG. 46  is a side elevational view of a preform component useable in the cartridge of  FIG. 41A . 
         FIG. 47  is an isometric view of the preform component of  FIG. 46 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure concerns an air cleaner configuration, and component features, as disclosed in  FIGS. 34-47  and described in connection with those drawings. Various ones, or selected ones, of the enhancements described in connection with those drawings, can be used to provide a useful air cleaner. 
       FIGS. 1-33 , and the description below relating to them, provides background. The systems features described in connection with these figures, are found in U.S. patent application Ser. No. 10/691,856, filed Oct. 23, 2003, and certain provisional applications from which that application claims priority. U.S. application Ser. No. 10/691,856, published Jul. 15, 2004, as US 2004/0134171 A1. They are also found in a corresponding PCT application US 03/33952 filed Oct. 23, 2003 and published as WO 04/039476 on May 13, 2004. 
     The description of  FIGS. 1-33 , as included herein as background, to provide for an understanding of features now shown and described in connection with  FIGS. 34-47 . Thus, the description of  FIGS. 1-33  provide background definition for the characterization of certain features in  FIGS. 34-47 . 
     I. Background Information from U.S. Application Ser. No. 10/691,856 and PCT Application US 03/33952 
     A. General Air Cleaner Configuration and Operation. 
     The reference numeral  1 ,  FIG. 1 , generally represents an air cleaner assembly according to U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952. The particular air cleaner assembly  1  depicted, is an engine combustion air intake air cleaner assembly  2 . Many of the techniques described can be applied in the filtering or cleaning of a variety of gases. However, the details disclosed were particularly developed for application in an air cleaner assembly, for example for use to clean engine intake air for an internal combustion engine, such as the engine of a vehicle such as a truck, bus, tractor or construction equipment; or for a generator. 
     Referring to  FIG. 1 , air cleaner assembly  2  generally comprises a housing  3  having: an air inlet  5 ; an air outlet  6 ; and, a dust ejector or drop tube  7 . The air cleaner assembly  2  also includes optional mounting legs or supports  8  thereon to facilitate mounting. (Alternatively, the assembly  2  could be mounted with a separate mounting band or bracket.) It is anticipated that the typical orientation for the housing  2  depicted in  FIG. 1 , in use, will be generally horizontal (i.e., with tube  6  extending horizontally, as generally shown in  FIG. 1 , with drop tube  7  pointing down). However, many of the principles and techniques described can be applied to air cleaner assemblies mounted in other orientations. 
     The particular housing  2  depicted has a generally cylindrically shaped outer housing sidewall  9 ; i.e., sidewall  9  is generally circular in cross-section. The air inlet  5  for the embodiment shown is a side entry  5   a , i.e., entry  5   a  goes through sidewall  9 . Specifically, inlet  5  is a circular, tangential, inlet  10 . The term “tangential” in this context is meant to indicate that a center line  11  of the circular inlet  10  is not directed toward a center axis  12 ,  FIG. 3 , of the housing  3 , but rather, center line  11  is directed more tangentially. This will cause the air entering through tangential inlet  10  (and thus directed into region  14 ,  FIG. 3 ), to begin movement in a swirling pattern. The swirling pattern is facilitated by the preferred, generally cylindrical, shape to sidewall  9 . 
     Still referring to  FIG. 1 , air outlet  6  is a circular, axial, outlet  15 . By “axial” in this context, it is meant that a center line of outlet  15 ,  FIG. 3 , extends parallel to a center line or axis  12 ,  FIG. 3 , of housing  3 . In the particular instance shown, the center line of outlet  15  is coaxial with the center line  12  of housing  3 , because the preferred housing sidewall  9  has a circular cross-section and the outlet  6  is not eccentrically positioned. Of course, alternate configurations are feasible, but this particular one is convenient. The reference to outlet  15  being circular, is a reference to the general shape of the interior air flow conduit. 
     Referring to  FIG. 3 , the sidewall  9  has first and second opposite ends  16  and  17  respectively. First end  16  is closed by cover  18  having outlet  6  projecting therefrom. Referring to  FIG. 3 , cover  18  is integral with, and is not separable from, end  16 , and, in the preferred configuration shown cover  18  has at least two, in this instance at least three, regions or steps of different diameter, indicated at  18   a ,  18   b  and  18   c . The corresponding internal diameters or steps decrease with  18   a &gt; 18   b &gt; 18   c . The function of these steps will be understood from further discussions. 
     Tap  6   a , in outlet tube  6 , is for attachment of optional pressure or restriction indicators or other equipment. 
     For the particular embodiment shown, dust drop tube  7  is adjacent first end  16 . 
     End  17 ,  FIG. 1 , defines an open end, and air cleaner  2  includes inlet  5  adjacent thereto. The open end  17  in the sidewall  19  is closed to passage of air therethrough by cover  20 . 
     In general, cover  20  has no aperture therethrough in the end region  20   a , and is a removable access or service cover  21  mounted on sidewall  9  to close end  17 . Service cover  21  is periodically opened or removed, to provide service access to an interior  23 ,  FIG. 3 , of housing  3 , for inspection, service or mounting of componentry contained therein. For the particular embodiment depicted, the service cover  21  is completely removable from sidewall  9 , for service access to interior  23 . The cover  21  can be secured to a remainder  25  ( FIG. 10 ) of housing  3 , in a variety of ways, for example through the use of latches, bolts or other constructions. Several, convenient, mounting mechanisms are shown and are discussed in detail below. 
     Attention is now directed to  FIG. 2 . In  FIG. 2 , air cleaner assembly  2  is depicted in exploded perspective view, so that certain separable componentry is viewable. Referring to  FIG. 2 , the componentry depicted includes: housing section  25  (i.e., the housing  3  without the cover  20 ); service cover  21 ; a removable and replaceable primary filter element or filter cartridge  30 ; optional removable and replaceable secondary safety filter element or cartridge  31 ; and, dust evacuator valve  32  (shown in phantom and not shown removed). Primary cartridge  30  is depicted in side elevational view in  FIG. 6 ; and, safety cartridge  31  is depicted in side elevational view in  FIG. 11 . The dust evacuator valve  32  is removable, but in normal use of air cleaner  2 , once installed valve  32  is not removed unless it becomes damaged. 
     Still referring to  FIG. 2 , the air cleaner assembly  2  further includes a precleaner  35 . In general, a precleaner such as precleaner  35 , operates to remove certain particulate material from an air stream, before the air stream is passed into media of the primary air filter element or cartridge  30 . An advantage from this, is that it provides for longer operational life of the primary filter cartridge  30 . For the particular arrangement depicted, the precleaner  35  is secured to the service cover  21 , and in normal, preferred, operation is never separated and indeed is not separable without causing damage to the cover  20 . In an alternate embodiment, discussed below in connection with  FIG. 21 , the precleaner is mounted on, and is secured to, the primary filter element or cartridge. 
     Referring to  FIG. 5 , the precleaner  35  includes: a cyclonic ramp component  36 ; and, a generally cylindrical shield component  37 ; with the ramp  36  positioned on an outer surface  42  of the shield  37 . In the embodiment shown, ramp  36  and shield  37  are integral with one another, the two being molded together as a single plastic piece. At end  36   a , region  36   b  behind ramp  36  (i.e., between ramp  36  and end  20   a  of cover  20 ) ramp  36  is closed by end  38 . Operation of components  36 ,  37  (and thus precleaner  35 ) will in part be understood by reference to general operation of the air cleaner assembly  2 . 
     During normal operation, air to be filtered enters air cleaner assembly  2  through tangential inlet  10 ,  FIG. 1  into space  14 ,  FIG. 3 . The space  14  is generally defined as being between inside surface  41  (of housing sidewall  9 ), and outside surface  42  (of shield  37 ). The entrance into space  14  is preferably into one of regions  43   a ,  43   b ,  FIG. 5 , where ramp  36  has not progressed away from end  20   a  substantially. Because of the preferred tangential entry, the air flow directed into space  14  is generally directed into a circular, circumferential or cyclonic flow. For the particular embodiment shown, and referring to the general view point of  FIG. 1 , when looking toward cover  20  from the outside of air cleaner  2 , this flow would be clockwise. Of course the air cleaner assembly  2  could be configured for an opposite direction of flow. 
     Referring again to  FIG. 3 , upon entering space  14 , the air is directed into the precleaner  35 . Cyclonic ramp  36  is positioned to help impart a spiral or cyclonic moment to the air and dust carried therein spiraling toward end  16 , as the air circles around shield  37 . In general the ramp  36  coils around shield  37  less than one full turn, preferably no more than 340°, typically less than 320°, for example an amount within the range of 150° to 280°. A typical shield  37  would project at least 35 mm. (millimeters) and typically 44 mm. to 170 mm. along the side of the element cartridge  30 . A typical ramp  36  would project at least 5 mm. and typically 7 mm.-20 mm. outwardly from shield  37 . 
     The shield  37  prevents the air, carrying particles, from immediately impacting the media in cartridge  30 , before spiraling (and thus precleaning) occurs. In general, as a result of the cyclonic spin, a substantial portion of the dust particles carried within the air stream will be directed toward inside wall  41  of housing  15 , eventually to be ejected through dust drop tube  7 . In a typical arrangement, dust drop tube  7  would be covered by an ejector valve  32 , shown in phantom in  FIGS. 1 and 2 . Such ejector valves are well known. Some examples are described in U.S. Pat. No. 3,429,108, the complete disclosure of which is incorporated herein by reference. 
     In a typical embodiment, the ramp  36  spirals at a rate providing about 2 mm. to 4 mm. linear movement or distance away from end  43 , per 10° of turn. 
     Referring to  FIGS. 3 and 5 , in general the primary element or cartridge  30  comprises an extension of media  55  which circumscribes and defines a central clean air volume  56 . For the particular embodiment depicted, the media  55  is arranged in pleats  55   a  which extend longitudinally between ends  57 ,  58  of the cartridge  30 . 
     Referring again to  FIG. 3 , after exiting precleaner  35  the air passes through primary cartridge  30  from upstream side  59  to downstream side  60 , and then enters clean air region  56 . The air at this point is typically sufficiently clean to be passed on through outlet tube  6 , to the engine/air intake of an internal combustion engine. 
     As mentioned above, the particular air cleaner assembly  2  depicted, includes an optional secondary or safety element or cartridge  31 ,  FIG. 2 . The safety element or cartridge  31  comprises media  65  positioned in region  56 ,  FIG. 3 , such that air exiting media  55  must pass through media  65  on the way to outlet  6 . Media  65  for a typical application, is not pleated, but rather comprises a sheet of non-woven fibrous media which circumscribes open central area  66 ,  FIG. 3 . 
     From the above description, general operation of the air cleaner assembly  2  will be understood to be as follows:
         1. Air to be filtered first enters the assembly  2  through inlet  5 .   2. Through a combination of tangential entry, the circular housing sidewall  9 , shield  37  and the precleaner ramp  36 , the air stream is directed into a cyclonic or spiral flow pattern. This drives some of the dust material against the inside surface  41  of the housing sidewall  9 , providing a precleaning effect. The precleaned dust is eventually ejected through down tube  7 .   3. The air passes through the media  55  of the primary filter cartridge  30 , and is filtered thereby.   4. If the optional safety or secondary filter cartridge is used, the filtered air then passes through media  65  of the safety or secondary filter cartridge  31 , into clean air region  66 .   5. The air is then directed axially outwardly from air cleaner  2 , through end cover  18 , i.e., through outlet duct  6 .       

     Also, certain general structural features of the preferred air cleaner assembly  2  are as follows:
         1. The access cover  20  is located at opposite end  17  of the housing  3  from the air flow outlet tube  6 .   2. The inlet  5  is a side entry inlet, and the outlet  6  is an axial airflow outlet.   3. The inlet  5  is located adjacent end  17  of the housing, and the outlet tube  6  is located adjacent opposite end  16  of the housing  3 .   4. The down tube  7  for the dust is located adjacent outlet tube  6  and end  16  of the housing.   5. Precleaner  35  is located adjacent inlet tube  5  at end  17  of the housing, and thus adjacent cover  20 .   6. For the particular embodiment of  FIG. 3 , the precleaner  35  is permanently mounted on cover  20 .
 
B. Sealing of the Primary Filter Cartridge  30  Within Air Cleaner  2 .
       

     As discussed above, primary filter cartridge  30  is a removable and replaceable (i.e., serviceable) component. That is, primary filter cartridge  30  is constructed to be removable for servicing (for example by replacement). In order to ensure proper operation of air cleaner assembly  2 , it is thus necessary that the primary cartridge  30  be constructed for appropriate sealing within housing  3 , once installed, so that air does not bypass the media  55  during operation. The air cleaner assembly  2  can be configured to provide for this seal in a variety of manners. 
     For example, a radial seal between either an internal portion or external portion of the primary element  30 , around its outlet end, and another portion of the assembly, could be used. Various types of radial seal systems, adaptable for air cleaners which include componentry having certain features as described herein, are shown for example in PCT Publication WO 89/01818 at 259 and in U.S. Pat. No. 5,938,804, FIG. 6 at 75; these two references being incorporated herein by reference. The types of radial seals depicted in those arrangements, could be adapted for use in a system as described herein, with appropriate modification. One radial seal is shown in the alternate embodiment of  FIG. 20 , discussed below. 
     The particular air cleaner assembly  2  depicted, however, uses a preferred axial seal between the primary filter cartridge  30  and the remainder of the air cleaner  2 , to advantage. The term “axial” in this context, is meant to refer to a seal which operates upon sealing pressure in the direction of arrow  68 ,  FIG. 3 , i.e., generally in a direction parallel to the element and housing central axis  12 . 
     More specifically, and referring to  FIG. 3 , end  16  of housing sidewall  9  is closed by end cover  18 , with outlet  6  herein. Interior surface  69  of end cover  18 , around air flow exit aperture  69   a , is configured as a sealing surface. That is, it is at this surface  69  that an axial seal is formed between the primary cartridge  30  and the housing  3 . 
     Referring to  FIGS. 5 and 6 , end  57  of primary filter cartridge  30  includes an end cap  57   a  having circular ridge, projection or rib  70  of seal material thereon, generally surrounding open central airflow exit aperture  71 . Seal rib  70 ,  FIG. 3 , is pressed against surface  69 , circumscribing aperture  69   a , to form the axial seal. The preferred rib  70  has a somewhat triangular cross-section before the compression shown in  FIG. 3 . 
     The particular arrangement depicted in  FIGS. 1-13 , uses an advantageous arrangement to press the rib  70  against surface  69 , forming the axial seal of the primary element  30 . This is discussed in detail in Section IV below, in which a detailed discussion of the primary filter cartridge  30  is provided. 
     In general, because an inside radial seal of the type described in PCT Publication WO 89/01818 is not used in the preferred air cleaner assembly  2 , housing  3  can be made free of any internally, axially, projecting radial seal tubes or cylindrical constructions, at end  16 , if desired. Also, because primary filter cartridge  30  is free of any outer radial seals of the type described in U.S. Pat. No. 5,938,804 at 75, the housing sidewall  9  for the preferred embodiment of  FIG. 3  can be made free of any otherwise necessary annular sealing surface for an outer perimeter radial seal. 
     C. Sealing of the Optional Safety Cartridge  31 . 
     Referring to  FIG. 2 , safety element or cartridge  31  includes first and second opposite ends,  80 - 81 . First end  80  is the end inserted toward outlet  6 , during assembly. End  80  includes mounted adjacent thereto and spaced therefrom, o-Ring  84 . Referring to  FIG. 3 , when mounted in assembly  2 , end  80  is pushed into annular cylindrical projection  85  of end cover  18  with o-Ring  84  providing a seal between the cartridge  31  and an annular, inside surface of end  18 , specifically section  18   c . The seal provided by o-ring  84  ensures that an undesired level of air does not go through outlet  6  without passage through safety element cartridge  31 . It is noted that the seal provided by o-ring  84  is typically not critical, since the seal of primary filter cartridge  30  primarily protects the engine from undesired (unfiltered) air flow. 
     The particular mechanism by which secondary or safety cartridge  31  is secured in position, and other features of secondary cartridge  31 , are described below in Section VI. 
     D. Primary Filter Cartridge  30 . 
     Attention is now directed to  FIG. 6 , in which primary filter cartridge  30  is depicted in side elevational view. In general, the filter cartridge  30  comprises: a media and seal support structure  90 ; media  55 ; and, first and second opposite end caps  92  and  93 . In general, end cap  92  is positioned at end  57  of primary element  30 ; and, end cap  93  is positioned at end  58 . The media  55  extends completely between the end caps  92 ,  93 . For the particular embodiment shown support  90  also extends completely between the end caps  92 ,  93 , although in some alternate embodiments, such extension might not be complete. 
     The particular preferred primary filter element or cartridge  30  depicted in  FIG. 6 , and generally used in air cleaner  2 , does not have an inner filter liner or support, extending completely between ends  57 ,  58 , mounted as an inseparable part of cartridge  30 . Rather, inner support along substantially the complete length of media  55  (except, for example, at one or both of the potted ends), is provided, optionally, by structure not mounted on and not provided as an inseparable part of, the primary cartridge  30 , as described below. It will be preferred that some inner support to the media is provided, either as part of cartridge  30  or as a separate component, preferably as a separate component. 
     In general, end  57  is an open end, including aperture  71  therein for exit flow of air during a filtering operation. On the other hand, end  58  is a closed end, meaning that air cannot pass through end  58  covered by end cap  93 , during normal operation. Features which provide for this in a preferred manner will be understood from the following discussions. 
     The media and seal support structure  90  is depicted in  FIG. 8 . The support structure  90  is shown in  FIG. 8 , without media or end caps thereon. Thus, support structure  90  depicted in  FIG. 8  is a component used to make cartridge  30 ,  FIG. 6 . In the cartridge  30 , the support structure  90  is generally not separable or removable, without causing damage to the cartridge  30 . 
     From a review of  FIGS. 1-3 and 8 , it will be apparent that the preferred cartridge  30  is a “non-continuously threaded” cartridge. By this it is meant that in the preferred embodiments there are no continuous threads on any portion of the cartridge  30 , for threadably mounting, securing or attaching the cartridge (for example upon continuous rotation or through 360° or more of required rotation) to any portion of the air cleaner  2 . 
     Referring to  FIG. 8 , the support structure  90  includes a first end  100  and a second end  101 . First end  100  generally defines a circular opening  102  free of framework therein. The circular opening  102  (in the completed element  30  as aperture  71 ), provides for an exit region (or outlet) for filtered air. In general, end cap  92  ( FIG. 6 ), is molded onto end  100  to provide closure to media  55  at this end. In a typical preferred embodiment, the end cap  92  also forms seal rib  70  and air outlet aperture  71 . Typically, to accomplish this, end cap  92  is formed from an appropriately compressible polymeric material, such as a foamed polyurethane as described below. 
     Referring to  FIG. 3 , preferably seal rib  70  is positioned either axially aligned with edge  100   a  of support  90 , or is positioned radially internally from overlap with edge  100   a . Typically it will be positioned radially inwardly from edge  100   a , with its peak no more than about 10 mm. internally of edge  100   a . As a result, rib  70  is generally driven against surface  69 , to form a seal, by either end  100   a  of support  90 , or pleat ends of media  55 , or both. 
     Referring to  FIG. 8 , support structure  90  includes, adjacent end  100 , shield  105 . Shield  105  is generally a portion of support structure  90  which is imperforate or impermeable to air flow therethrough. The shield  105  is generally sized,  FIG. 3 , to overlap aperture  7   a  where dust drop tube  7  encounters a remainder of sidewall  9 . This inhibits dust, as it flows to the tube  7   a , from directly impinging the media  55  in an undesirable manner, in this region. Air can get under shield  105  at edge  105   a , to encounter media  55  in this region ( FIG. 3 ). 
     Attention is now directed to  FIG. 6 . In  FIG. 6 , in phantom, an optional axially projecting ring or rib  105   b  is depicted. Such a ring  105   b  would be a continuous ring projecting axially outwardly, as it circumscribes shield  105 . Typically and preferably ring  105   b  is integral with a remainder of shield  105 . The optional ring  105   b  would preferably be positioned adjacent to, but spaced from, portions of mounting structure  129  described below, to inhibit undesired levels of dust transport into that mounting structure  129 . This will be described in greater detail below. 
     For the particular embodiment shown, the support  90  extends completely between ends  100  and  101 ; and, between shield  105  and end  101 ,  FIG. 8 , support  90  includes a perforate or open section  106 . By this it is meant that in region  106 , support  90  includes framework  107  that leaves substantial open areas  108  for passage of air there through, to encounter media. Preferably in this region  106 , the framework  107  is at least 50% open, and more preferably at least 70% open. By this, it is meant that of the total area of region  106 , at least 50% and more preferably at least 70% is occupied by aperture or opening, as opposed to solid framework. Preferably the imperforate shield  105  occupies at least 10% but does not occupy more than 40% percent, of the total extension (length) of support  90  between end  100  and end  101 . Preferably the perforate section  106  occupies at least 20%, more preferably at least 60%, of a total axial length of support  90 . 
     Still referring to  FIG. 8 , the preferred framework  107  depicted comprises a plurality of radially spaced, axial ribs  109 , in this instance 10 equally radially spaced such ribs, typically 6-14 such ribs, cross connected by a circumferentially, spiral, radial rib structure  109   a , in this instance two continuous spirals  109   b  extending from approximately points  109   c  (separated radially by about 180°) adjacent end  101 , to points  109   d  (separated radially by about 180°) adjacent shield  105 , each with a total radial extension of about 720°. Advantages from a spiral rib structure  109   a , as opposed to a series of parallel radial ribs, relate to provision of resistance to distortion of framework  107  when placed under radial stress during sealing an unsealing of cartridge  30 . An alternate way to describe the spiral turn of radial ribs  109 , is that they angle, from being perpendicular to central axis  12 ,  FIG. 3 , by at least about 10°, and typically an angle within the range of 15° to 45°. This can alternatively be stated to be the acute angle B,  FIG. 6 . 
     Attention is now directed toward end  101 ,  FIG. 8 . In general, end  101  includes end framework  110  extending there across, in contrast to opening  102  at end  100 . Framework  110  does not completely close end  101 , but rather includes the following general features: central, impermeable region  111 ; and, annular open framework  112 . 
     Still referring to  FIG. 8 , annular open framework  112  generally includes spokes  113  (in this instance 8 spokes, typically 3-11 spokes) extending between impermeable region  111  and end  101 ; and, structural, circular, rib  114  interconnecting the spokes  113 . Openings  115  defined by structure  112 , help provide for preferred manufacture of primary element  30 , as next described. 
     During a preferred manufacture of primary element  30 , a pre-made, molded plastic, component comprising support  90  would be provided. Pleated media would be put into support  90 , through opening  102 . The pleated media would be inserted sufficiently far, for an end of the media to rest upon framework  112 . Recessed surface  111   a  in region  111  projects with the media around it, toward end  102  to define an annular media receiving trough  116  therearound, to help keep the inserted end of the media in a round shape. 
     End  101  of the framework  90  could then be placed into a mold, including a curable polymeric material. The polymeric material will flow through the framework  112 , into the ends of the media pleats, to form a potting, as shown at end cap  93 ,  FIG. 6 . This will seal ends of the pleats closed, secure the media in place, and close openings  115 . In general, the potting material and mold depth will have been selected so as to not to have the potting material reach surface  111   a  of recessed region  111 . A typical depth of recess for surface  111   a  from end  101  would be at least about 3 mm. and usually not more than 7 mm., for example 4-5 mm. 
     Attention is directed to  FIG. 4 , in which an end cap  93  formed by such a process is depicted. The potting material is generally indicated at  120 . It can be seen that although region  111  has not been covered by the potting material  120 , the remaining framework  112  has been. For the particular arrangements shown in  FIG. 4 , the molded potting material  120  is shown with annular, radially spaced, depressions  121  resulting from mold standoffs. 
     End cap  93 , then, is a composite, closed, end cap  58 , with the composite generally comprising: potting material  120  forming an annular, imperforate, ring; and, exposed surface  111  which forms a central imperforate surface in the end cap  93 . 
     Manufacture of the element  30  could be completed, by inserting end  100  into a second mold, and molding end cap  92  thereon. The media  55  would be prevented from dropping through aperture  102 , during insertion into the second mold, since it would have been anchored in place to framework  112  by the first molding process. 
     The primary filter cartridge  30  of the preferred embodiment includes thereon structure to provide for securement of the cartridge  30  in place and assembly  2 , during use. For the particular preferred construction illustrated, the mounting structure is provided as an integral part of support  90 ; however alternatives are possible. The structure can be understood, in part, by review of the support  90 ,  FIG. 8 . 
     In  FIG. 8 , mounting structure  129  providing for securing cartridge  30  with seal material  70 , ( FIG. 3 ) compressed against surface  69 ,  FIG. 3 , is depicted. The particular mounting structure  129  depicted, is part of a non-continuously threaded, rotation engagement mechanism  129   a , which is operated to press seal material  70  against surface  69  in part upon a rotational moment imparted filter cartridge  30 . It is this operation of providing radial twist to the cartridge  30 , during locking and mounting, which is facilitated by providing support  90  with spiral construction  109   a . The preferred arrangement shown is configured so that a rotational motion of no more than 50°, preferably no more than 30°, most preferably 20° or less, is all that is necessary to go from an unlocked position to a locked position. This will be apparent from the following descriptions. 
     The engagement structure  129   a  in general operates with a portion of cartridge  30  engaging, upon rotation, a portion on the housing section  25 . An example of a particular interaction will be understood by reviewing  FIG. 8 , specifically radially outwardly projecting ring  130 , which operates as mounting structure  129  on cartridge  30 . 
     Radially projecting ring  130 , in the embodiment shown, is a segmented ring  131 . The particular embodiment shown comprises four identical, evenly spaced, segments  131   a ; however alternatives are possible. In  FIG. 5 , three of the segments  132 ,  133  and  134  are viewable. The fourth segment  135  would be positioned as shown in  FIG. 5 . All four are viewable in  FIG. 7 . Each segment  131   a  projects radially outwardly, from an immediately adjacent portion of support  90 , by at least 2.5 mm., typically at least 3.5 mm. 
     Referring to  FIG. 8 , segmented ring  131 , has a series of radially spaced gaps  136  therein. The gaps  136  are positioned between the segments  132 - 135  of the segmented ring  131 . The gaps  136  are appropriately sized to allow at least selected portions of ring  131  to be pushed (axially) past structural features in the housing  9 , for rotational engagement as discussed below. Each gap  136  is preferably at least 6 mm. wide, typically at least 7 mm. wide. Gaps on the order of 20 mm.-40 mm. are useable, for example. 
     Referring to  FIG. 8 , each ring segment  131   a  (such as segment  133 ), includes first and second opposite ends  140  and  141 . End  141  is typically a blunt end; and, end  140  comprises a short segment at  142  axially offset (from a remainder  143  of the segment  131 ) toward end  100 . A result is formation of a receiving area  145  along a surface  146  of segment  142  facing toward end  101  (or away from end  100 ). Receiving area  145  is positioned to engage (upon radial receipt) structure in the housing  9 , discussed below, to ensure appropriate sealing between the primary element  30  and the housing  9 , during operation. It is noted that tip  147  of section  140  comes to a rounded point, with surface  145  being a cam surface and recessing from tip  147  toward end  101  in extension toward section  143 . It is also noted that each of the ring segments  132 - 135  is oriented with its offset section corresponding to section  142 ,  FIG. 8 , on one side of a gap  136 , and with a blunt end, corresponding to end  141  of the next adjacent ring segment, positioned on the other side of the corresponding gap  136 . In the instance shown, and from the end view from end  101 , each segment  131  “points” in clockwise arc, with end  141  being considered the front end. 
     Attention is now directed to  FIG. 10 . In  FIG. 10  a cross-sectional view of portion  25  of the housing  9  is depicted. In  FIG. 10 , holder structure  150  is shown. From  FIGS. 9 and 10 , it will be apparent that for the particular embodiment shown there are four, evenly spaced, holder structures  150 , one corresponding to each gap  136 , in ring  130 . 
     Each holder structure  150  is positioned adjacent an inside surface  41  of housing  9  at region adjacent section  18   b  (at a joint area between sections  18   a  and  18   b ) of the housing sidewall  9 . Each holder structure  150  is sized to pass through a gap  136 ,  FIG. 8 ; further, surface  151 , which is directed toward outlet  6 , is shaped as a cam to slant toward outlet  6  in recess from tip  150   a . Finally, holder  150  includes end stop  152  thereon at an end opposite tip  150   a.    
     From the viewpoint of  FIG. 9 , i.e., looking toward end  17 , each of the holders “points” counter-clockwise, if it is assumed that the tip  150   a  is the front of each holder and that the stop  152  is the back end. Pointing this direction facilitates engagement with ring segment  131 , which, as characterized above, points in an opposite direction. It is noted that if the ring segments  131  are configured to point counter-clockwise, then the holders  150  could be directed to point clockwise. (These and other alternative arrangements will be understood from the following description of operation.) 
     Although alternatives are possible, in the particular arrangement shown, the housing  3  would include four holders corresponding to holder  150 , evenly radially spaced around an interior of surface section  18   b , each pointing in the same direction. Again, the four holders  150  would generally correspond with the four gaps  136  between the four ring segments,  132 - 135 . 
     Operational engagement between the primary filter cartridge  30  and the housing  3 , to cause sealing between gasket  70  and surface  69  should now be apparent. In general, cartridge  30  would be inserted into the open housing  25  through open end  17 ,  FIG. 10 . The end of the element  30  inserted first, would be end  57   FIG. 6 . The cartridge  30  would continue to be pushed in, with an appropriate radial orientation such that holders  150  can pass through gaps  136 . This will allow gasket  70  to encounter and be pressed against surface  69 ,  FIGS. 3 and 10 . Once this extent of insertion is reached, the cartridge  30  would be rotated, (for the particular arrangement depicted clockwise), so that portions  142  of each ring segment would be aligned over surface  151  of each holder  150 . The surface  145  of each section  142  and surface  151  of each holder  150 , i.e., the engaging surfaces, would be shaped and sized to cause a further biasing or camming to drive cartridge  30  against surface  69  preferably with compression of rib  70 , to ensure appropriate compression of the gasket material  70  to form a seal. Rotation would preferably be designed to occur until tip  147  engages stop  152 . 
     As a result of the rotational interlock, the cartridge  30  cannot back away from surface  69  without being rotated, due to the holders  150  being positioned against surfaces  146 . 
     Referring to  FIG. 10 , in general the arc length between tip  150   a  and stop  152 , represents the rotational arc between full locking and fully unlocking of the cartridge  30 . Typically, the construction will be such that the arc is no more than 70°, typically no more than 50°, and for the particular arrangement of  FIG. 10 , preferably no more than 40°. Most preferably, for the arrangement of  FIG. 10 , it is no more than 30°. Indeed, for the particular arrangement shown, this arc is on the order of only about 10° to 25°. 
     From the above, it will be apparent for the particular preferred arrangement shown, the primary filter cartridge  30  includes no inner support structure extending between ends  57 ,  58 , along an inside surface of the media  55 . This is advantageous, for manufacture and assembly. When the cartridge  30  is positioned for use, in an air cleaner, inner support to the media  55  is provided by structure already positioned within the housing  3 . 
     More specifically, internal support for the media  55  is provided by a separate support structure  160 ,  FIG. 2  for example a portion of the secondary or safety element or cartridge  31 . In the event that an optional secondary or safety element  31  is not used with the system, a support structure similar to structure  160 , but not having media associated therewith as a secondary filter, can be used to support media  55  along its inside. 
     Attention is again directed to the optional rib  105   b  shown in  FIG. 6 . Such a rib  105   b , in use, would generally be positioned spaced axially toward end  93  from mounting structure  129 , specifically axially toward end  93  from segment and ring  131 . Preferably the spacing the optional rib  105   b  from the segmented ring  131 , in this direction, would be by no more than 10 mm., and preferably substantially less. The continuous ring  105   b  would generally protect segmented ring  131  from being undesirably exposed to dust, during use. 
     In some alternate application of the described principles, it may be desirable to have framework  90  not extend continuously from end  100  to end  101 ; but rather to have the support  90  include shield  105 , without framework from end  101 ; and, to have at opposite end  101  appropriate structure (such as impermeable region  111  and annual open framework  112 ), for forming a preferred composite end cap. 
     E. The End Cover  20 . 
     As indicated previously, the end cover  20  is a service cover  21  that can be removed from the remainder of the housing  25  to allow service access to the interior  23  of the housing. 
     For the particular arrangement shown, the end cover  20  has no air flow aperture extending therethrough. That is, it has an outside surface  20   a ,  FIG. 1  and an inside center surface  20   b ,  FIG. 5 , with no aperture or air flow tube extending therethrough. For this reason, it can be referred to as a “closed” or “completely closed” end cover  20 . 
     Referring to  FIGS. 1, 2 and 4 , assembly  2  includes a mounting and locking mechanism  170 , to secure the cover  21  onto the remainder  25  of the housing sidewall  9 . In general the mounting and locking mechanism  170  comprises a plurality of flexible tabs mounted on one of the housing sidewall  9  and cover  20 , and a plurality of engageable recesses mounted on the other one of the housing sidewall  9  and cover  20 . For the particular arrangement shown, the mounting and locking mechanism  170  generally comprises a plurality of flexible tabs  171 , on end cover  21 , each of which includes a radially projecting tongue  172 ,  FIG. 4 , thereon. For the particular arrangement shown, the mounting mechanism  170  comprises two tabs  171   a ,  171   b , radially spaced 180° apart, around the circumference of cover  21 . The housing and  17  includes a pair of recesses or slots  175 ,  FIG. 1 , therein, for receipt of tongues  172 , when the service cover  21  is mounted. 
     Operation, then, is as follows: referring to  FIG. 1 , in order to remove service cover  21  from the remainder of housing  3 , tabs  171  would be biased toward one another. This would move the projecting tongues  172  ( FIG. 4 ) out of slots  175 , releasing the cover  21  for movement relative to the housing sidewall  9 . Insertion would be a reverse operation. Particular useable materials for formation of the cover  21 , to provide flexible tabs  171 , are discussed below. If the tongues  172  are provided with appropriately cammed surfaces on an end directed toward remainder  25  of the housing, when the cover  20  is pressed in place, it will not be necessary to bias the tabs  171  by hand during mounting, but rather the cams would cause the biasing or snap fit mounting as the cover  20  is pressed in place. 
     An advantage to the particular mounting and locking mechanism  170  described, it is that it comprises features integral with cover  20  and housing  9 , and does not require the attachment of any additional mechanisms such as latches, hooks, etc., for operation, after cover  20  is molded. 
     For the particular mounting system involved, only two tabs  171  and slots  175  are used; and, each tab  171  can engage each one of slots  175 . As a result, as thus far described the cover  21  could be mounted in two rotational orientations relative to sidewall  9 . However, if this were possible for the particular embodiment depicted, the cover  20  could be mounted such that the orientation between the inlet  5  and the ramp  36  is not appropriate. To ensure that the cover  20  is only mountable in a single rotational position, relative to a remainder of the housing  25 , an indexing arrangement can be provided. Specifically a slot and key arrangement can be used, in which one member (slot or key) is positioned on the cover; and another member (key or slot) is on the housing sidewall  9 . The two members would be positioned so that the cover can only fit (slot engage key) when it is rotated to a specific pre-set orientation. 
     An example as illustrated in the embodiment of  FIG. 15 , in which a cover  700  is shown mounted on a sidewall  701 , with a key or pin  702  on the cover  100  received within a slot  703  on the sidewall  701 . Cover  700  could only be properly mounted, if the key or pin  702  is aligned with the slot  703 . Thus, the slot and key arrangement  705  depicted in  FIG. 15  ensures that the cover  700  is appropriately rotationally mounted relative to the housing sidewall  701 , for proper operation. 
     Referring again to  FIG. 1 , an optional handle construction  710  is shown, in phantom, on cover  20 . If desired, the tabs  171  and slots  175  could be configured such that under a hand (pulling) force applied to handle  710 , (i.e., under pulling of the handle  710 ), the cover  20  could be released from its secure position without the need to manually press tabs  171  toward one another. The handle  710  could be configured in a variety of forms. The particular handle  710  shown includes a removable or replaceable cross piece  711  extending between two mounting ears  712 ,  713 . The ears  712 ,  713  could be molded integrally with a remainder of cover  20 . 
     Attention is now directed to  FIG. 5 , for detail within shield  37  on cover  20 . In particular, in a portion  178  inside of shield  37  which will be adjacent end  58  in use, cover  20  includes an internal ring  179  of smaller inside diameter than a remainder  179   a  of shield  37 . The ring  179   a ,  FIG. 3 , is sized to receive end  58  therein with little or no space therebetween in use. This will help securely support the end  58  of primary cartridge  30 , along end cap  93 , i.e., at an end of cartridge  30  remote from outlet  6 . 
     Referring to  FIG. 6 , the primary filter cartridge  30  is supported at end  57 , within the housing  3  ( FIG. 3 ), by a combination of: the mounting structure  129 ; and, end cap  92 . 
     Referring to  FIG. 4 , attention is now directed to an engagement arrangement, for providing a preferred engagement between primary element  30  and cover  20 . In particular, and referring to  FIG. 4 , impermeable region  111 , in primary filter cartridge  30 , includes recessed surface  111   a  in the pre-form comprising a portion of framework  90 , and includes centrally positioned in surface  111   a , a first member  183  of a projection/receiver arrangement  184 . In particular, surface  111   a  includes receiver  185 . Preferably, the receiver  185  is non-circular, for reasons discussed below. The particular receiver  185  depicted for the embodiment shown in  FIG. 4 , is an X-shaped (or “+” shaped) receiver  186  with a 90° angle between center lines of each pair of adjacent arms of the X-shape, although a variety of alternate shapes can be used. A particular advantage resulting from the X-shape to the receiver  186 , is discussed below with respect to indexing and symmetry. The term “pre-form” in the context of this paragraph, refers to a structural component of the end cap made prior to potting into the end cap material. 
     Further, as shown at  FIG. 5 , cover  20  includes, along the inside surface  190  thereof, a second member  187  of the projection/receiver arrangement  184 , in this instance a centrally positioned projection  191 . Again, preferably projection  191  is non-round and in this instance is an X-shaped projection  192 , with a 90° angle between a center line of each pair of adjacent arms of the X-shape. The projection  192  is sized and configured to project, when appropriately aligned, into receiver  185 . When the air cleaner  2  is assembled,  FIG. 3 , projection  191  will protrude into receiver  185 . In part because the projection  192  and receiver  186  are both non-round, the cartridge  30  is prevented from rotating, in use, by the projection/receiver arrangement  184 , when the air cleaner end cover  20  is locked in position on housing  3 . 
     In particular, it is important that during use, the element  30  not inadvertently rotate relative to the housing  3 , to ensure that the seal between gasket material  70  and surface  69  is maintained. That is, relative rotation between element  30  and surface  69  would tend to disengage the interaction between holders  150  and ring segments  131 . To inhibit rotational movement of the element  30  relative to the remainder of the housing  3 , during assembly and use, projection  191  and receiver  185  are shaped, to engage upon rotation and inhibit a sufficient relative rotational movement between the cartridge  30  and a remainder of air cleaner  25 , to allow the cartridge to unseal. The particular shape shown for each is an X-shape. However, with respect to this general function, all that is generally required is that the projection  191  and the receiver  185  not be circular, but rather each be non-circular and have a portion that interacts with the other and inhibits rotational movement of one relative to the other. 
     The particular use of a four armed cross or X-shape (or +-shape; i.e., “plus shape”) for each member, relates to an indexing and symmetry function. In particular, ring  131  of primary filter cartridge  30  includes a specific number (N) of radially spaced gaps  136 . As a result of this configuration, and also the same number (N) of holders  150  and the same number (N) of segments  131 , cartridge  30  can be positioned within housing  3 , at N specific radial orientations. When N is the number 4, and the four positions are 90° apart, each one of these N radial orientations corresponds to an arm  193  of projection  191 . Since there are a total of four gaps  136 , four holders  150  and four sections  131 , the particular projection  191  depicted is an X-shape  192  with four arms  193  each extending at 90° relative to adjacent arms. Of course, receiver  185 ,  FIG. 4 , is similarly constructed. Thus, the element can be mounted in four rotational positions. 
     Such a symmetry between a number of possible rotational positions and engagements, between the primary cartridge  30  and the remainder of the housing  3 , will generally be referred to as a primary cartridge/housing rotational symmetry. For the particular embodiment shown, the primary cartridge/housing rotational symmetry is four fold, meaning four rotational orientations, but not more, are possible. Of course, alternatives are possible; however, preferably at least two possible rotational positions are provided. 
     The extent to which the projection member  191  extends into the recess or receiver  185  (of the preform), of the projection/receiver interlock arrangement  184 , is not critical, as long as the extent of projection is enough to inhibit rotation. It is anticipated that in general constructions will be made such that the amount of projection into the receiver  185  from surface  111   a  will be at least 3 mm., typically at least 5 mm., and generally on the order of 6 mm. to 10 mm. 
     Of course the first member of the projection receiver arrangement  183 , could be a projection as opposed to a receiver, with the second member being the receiver instead of the projection. That is, the projection/receiver arrangement  184  could be configured with a projection extending axially outwardly from surface  111   a , toward cover  20 , to be received within a receiver on end cover  20 . The particular arrangement depicted, however, with receiver  185  on the cartridge  30 , and the projection  191  on the cover  20 , is preferred. 
     Again, it is noted that impermeable end  111  and framework  112  ( FIG. 8 ) are preferably formed as a pre-form, before a remainder of end cap  93 ,  FIG. 6 , is molded. 
     Referring to  FIG. 3 , it is also noted that the preferred cover  20  is circumscribed by end  17  of housing sidewall  9 , when the cover  20  is properly mounted; and, the cover  20  includes no portion which slides over (or around) region  17   a  on an outside surface of end  17  of sidewall  9 . A cover  20  configured in this manner, will sometimes be referred to by the following characterizations: “cover  20  is positioned circumscribed by a portion of housing  9 , when mounted, and cover  20  includes no portion which circumscribes housing  9 , when mounted,” or by variants thereof. Alternative arrangements for mounting the cover  20 , are described below. 
     F. The Optional Safety Element  31 . 
     Attention is directed to  FIGS. 11-13 , with respect to the optional safety element  31 . In general the safety element  31 ,  FIG. 13 , comprises: support  160 ; inner support  201 ; media  65 ; and, o-ring  84 . The support  160  generally extends between first end  80  and second end  81 . The first end  80  is the end first inserted into the housing interior  23 , during mounting. End  80  includes o-ring  84  mounted spaced therefrom but adjacent thereto, and positioned in o-ring receiver  203 . For the particular embodiment shown, end  80  includes, immediately adjacent thereto, impermeable ring surface  205  with mounting slots  206  therein. The mounting slots  206  are generally L-shaped (or J or hook shaped),  FIG. 12 , and are positioned to engage posts  210  within housing  3 ,  FIG. 9 , upon an appropriate engagement and twist. The posts  210  project radially inwardly. (An alternate embodiment is described below which does not use a slot  206 /post  210  engagement mechanism.) 
     For the particular arrangement shown in  FIGS. 11-13 , there are two slots  206  and two posts  210 , each member of each pair being positioned rotated 180° from the other around an inside of housing  3 . The posts  210  are on surface  18   c . Thus, outer support  160  is configured to have two rotational positions relative to the housing  3 , during installation. The symmetry between support  160  and the housing  3  will generally be referred to as support  160 /housing symmetry or by variants thereof. Symmetry with two possible positions, but not more, will be referred to as two-fold support  160 /housing symmetry. 
     Referring again to  FIG. 13 , support  160  comprises framework  211  with apertures  212  therein. Preferably support  160  is at least 50% open and more preferably at least 70% open, in extension between end  80  and end  81 . In general use, safety cartridge  31  does not have a substantial twisting and pressure applied thereto, simply to operate interaction between slots  206  and posts  210 . That is, the rotation to operate interaction between posts  210  and slots  206  is relatively easy. Thus, the support framework  211  does not have spiral radial extensions, but rather uses parallel hoops  213  (in this instance five hoops) interconnecting axial extensions  214 . 
     End  80  generally defines an open circular interior  80   a , through which air can pass during use. End  81 , on the other hand, is closed by cover  215 . For the particular embodiment shown, cover  215  includes a recessed center  216 , configured as described below. 
     For the particular safety element depicted in  FIGS. 11-13 , the media  65  comprises a wrap or similar construction of non-pleated, non-woven, material. It is positioned generally between inner support  201  and support  160 . Referring to  FIG. 13 , the inner support  201  is generally framework having first and second opposite ends  222 ,  223 , with an open or porous support structure  229  extending therebetween. Preferably the porous structure  229  is at least 50% open and more preferably at least 70% open, over this extension. For the particular arrangement shown the support structure  229  is a series of radially spaced axial extensions  229   a  supported by parallel, spaced, hoops  229   b , in this instance five hoops, not counting end  229   c.    
     For the particular arrangement shown, end  222  of inner support  201  defines an open circular opening  222   a , for passage of air therethrough during use; whereas end  223  is closed by end cover  225 . The preferred end cover  225  depicted, includes a recessed center portion  226 . 
     The particular components  160 ,  201  depicted in  FIG. 13 , are configured for engagement. In particular, media  65  can be positioned around an outer surface  201   a  of inner support  201 . This assembly could then be projected into an interior  160   a  of support  160 , until end cover  225  engages end cover  215 ,  FIG. 12 . 
     For the particular arrangement shown, cover  215  includes a pair of apertures  230  therein, sized and shaped to receive posts  231 , on cover  225 , for an interlocking engagement. Interference (snap) fit, heat staking or other construction methods can alternatively be used. Preferably in the immediate area where the components  160 ,  701  directly engage for interlock, there is no media  65  positioned between them. 
     It is noted that cover  215  is sized and recessed for a telescoping fit or projecting fit, into a recess  225   a  defined by cover  225 . This, in part, accommodates recess  216   a  in support  60  which in turn accommodates the projection/receiver arrangement  184 , when air cleaner  2  is assembled,  FIG. 3 . 
     Attention is still directed to  FIG. 3 , with respect to complete assembly. It is noted that recess  185  of the primary filter cartridge  30  projects (in the preferred arrangement shown) partially into recess  216   a  defined by the cover  215 . As a result, each of the primary element  30  and the safety element  31  are inhibited from coming loose and moving in a direction toward cover  20 , during assembly and use. 
     In those instances in which it is desirable not to utilize optional secondary or safety filter  31 , it may be desirable simply to install support  160  with no media  65  or support  201  associated therewith, into housing  3 . The support  160  would still operate, then, as inner support for the primary filter cartridge  30 . 
     In general, the apertures  230  and posts  231 ,  FIG. 13 , can be viewed as a projection/receiver arrangement  233 ,  FIG. 12 , for the safety element cartridge  31 . The projection/receiver arrangement  233  could be configured, alternatively, with the projection on the outer support  160  received within receivers on the inner support  201 , or in further alternate arrangements, if desired. In general terms, then, the inner support  160  includes a first member of projection/receiver arrangement  233 , and the inner support  201  includes a second member of such an arrangement. 
     G. The Outer Surface Shape of the Components  30 ,  31 . 
     Referring to  FIG. 6 , it is noted that the primary element  30  has an outer surface shape, which is generally conical. More specifically, region  240 ,  FIG. 6 , of outer support  90  is a wide end and has a first diameter D 1 , and region  241  is a narrow end and has second diameter D 2  with:
         (a) D 1  greater than D 2 ; and   (b) a dimensional decrease in cross-sectional diameter being generally even in extension between points  240  and  241 .       

     Typically and preferably diameter D 1 , a largest diameter adjacent end  57 , is at least 10% larger than diameter D 2 , a diameter adjacent a smallest end  58 . Typically and preferably the diameter D 1  is at least 10 mm. larger than the diameter D 2 . Such a shape may sometimes be referred to as frusto-conical, since the conical shape does not taper to a point. 
     This generally conical shape, which includes shield region  105  and open region  106 , provides for advantage. First, the narrow end at  241 , allows for an outside diameter that accommodates some of the space taken by the ramp  36  and shield  37  of the precleaner  35 , without a larger diameter being needed for air cleaner housing sidewall  9 . On the other hand, the larger diameter D 1  at region  240  allows for a relatively large exit aperture  102  and thus reduction in restriction to exit air flow while maintaining a relatively large amount of media  55 . Also, referring to  FIG. 3 , the increase in diameter of shield section  105  in extension between points  242  and  243 , helps direct dust or other particles into aperture  7   a  of down tube  7 . 
     In general, referring to  FIG. 12 , the particular preferred safety filter cartridge  31  depicted has an analogous conical shape with a diameter D 3  at region  250  greater than diameter D 4  at region  251  and an even taper and decrease in diameter therebetween. This will ensure that support member  160  of the safety filter cartridge  31  is positioned adjacent internal pleat tips of media  55  in cartridge  30 , for support there along. 
     H. Jointed Housing Construction. 
     Attention is directed to  FIG. 1 . In particular, the housing  3  depicted has a sidewall  9  which is a segmented sidewall  260 . By “segmented” in this context, it is meant that the sidewall  9  includes at least two sections  261 ,  262  which are not formed integrally with one another, in a single molding, but rather which are separately made and are mechanically secured along a joint or seam  263 , to form sidewall  9 . 
     For the particular arrangement shown, the segmented housing  260  includes, in first section  261 , the following: end  16 ; outlet tube  6 ; and, down tube  7 . In segment  262 , the housing  260  includes: inlet tube  5 ; and, end  17  for mounting cover  20 . 
     Engagement between segments  261  and  262 , at joint  263 , is provided through an interlock mechanism  270 . In general the interlock mechanism  270  includes a plurality of projections  271 ; and, a plurality of receivers  272 , in this instance flexible latches or u-shaped hoops  273 . The hoops  273  are sized to snugly snap fit over the posts  271 , when section  262  is pressed toward section  261 . For the particular arrangement shown, each of the posts or projections  271  is generally rectangularly shaped and each of the latches or hoops  273  has a similarly shaped aperture therein, to facilitate snug fit. 
     For the particular arrangement shown, the projections  271  are evenly radially spaced around outer surface  272  of segment  261 ; and, the flexible latches or hoops  273  are evenly radially spaced around outer surface  274  of section  262 . Alternate constructions are of course possible. For example, the specific locations could be reversed. The particular arrangement shown, however, is preferred. 
     For the arrangement shown, the central aperture of each latch or hoop  273  has a perimeter size of about 12 mm. wide, with the post or projections  271  having a similar width. Each post  271  has a length of about 11 mm., with a cam shape from tip  271   a  to sharp edge  271   b ,  FIG. 10 . 
     Referring to  FIG. 1 , for the particular arrangement depicted, section  261  includes an enlarged (in diameter) rim section  280  adjacent end  281 , to receive a portion of surface  274  therein, and to circumscribe that portion, during assembly. This is also shown in  FIG. 10 . 
     In a preferred arrangement, at least six radially spaced posts  271 , and six radially spaced latches  273 , are used. Typically and preferably the number of each will be about eight to fourteen. 
     Advantages from the segmented housing construction will be understood by reference to  FIG. 1 . In particular, segment  261  will be mounted or oriented, on a vehicle, such that drop tube  7  is pointed generally downwardly. This facilitates operation of dust evacuation through evacuator valve  32 . 
     The inlet tube  5  will generally need to be directed, for various equipment, toward a preferred location for an inlet tube to be connected. For different vehicles, it may be desirable to have a different orientation (radially) between the center line  11  or direction of tube  5 , and tube  7  from that shown in  FIG. 1 . The segmented housing allows for section  262  to be mounted on section  261 , in at least 2 and preferably more selected rotational orientations. 
     The particular segmented housing  260  depicted in  FIG. 1 , is organized to permit four possible rotational orientations, each 90° spaced from one another. Indexing between the four arrangements is provided by indexing arrangement  290 . In general, the indexing arrangement  290  comprises a rib/detent arrangement in which ribs are used in one member of the two housing pieces, and detents are used on another member of the two housing pieces, to index line for joining. 
     The indexing arrangement  290  for the arrangement shown, comprises four ribs  291  which extend axially and project radially outwardly from surface  274 , each of which engage an associated detent or receiver  292  in section  272  of segment  261 . Four evenly spaced interference fitting ribs and detents, index four possible rotational orientations of the segment  262  relative to segment  261 , for sliding engagement and activation of the snap fit locking mechanism  270 . 
     In general, the snap fit locking mechanism  270  should be selected so as to make disconnection relatively difficult. This is because it is not anticipated that, typically, once assembled and installed, air cleaner  2  would be reconfigured for a different rotational relationship between segment  262  and segment  261 . 
     Another possibility allowed or accommodated by a segmented housing  260 , is having a single mold for segment  261 , while having alternate molds for segment  262 , for example to vary overall housing axial length or to accommodate, in a custom manner, a different cartridge  30 . 
     Of course the segmented housing is optional. In  FIG. 14 , there is depicted a housing  300  which is not segmented. The housing  300  may be in accord with the description given about for  FIGS. 1-13 , except for the absence of the segmented housing. 
     I. Selected Alternate Arrangements. 
     1. An alternate mounting approach for the safety element,  FIGS. 16-19 . 
     For the arrangement of  FIGS. 1-13 , the safety element  31  was mounted by a twist mount involving interaction between slots  206  and posts  210 . An alternate arrangement is shown, in  FIGS. 16-18 . 
     In  FIG. 16 , an end view in air cleaner  400  according to the alternate arrangement is shown. The end view of  FIG. 16  is generally analogous to the end view of  FIG. 9 . The parts used in air cleaner assembly  400  may be generally as described above the arrangement of  FIGS. 1-13 , or even as characterized in alternate arrangements, except as described herein in connection with the mounting of the safety element. 
     In general, the air cleaner assembly  400  includes a housing  401  having an outer sidewall  402 . In  FIG. 16 , the air cleaner assembly  400  is shown with an end cover removed. However, the end cover may be generally analogous to end cover  20 ,  FIG. 1 . 
     Attention is now directed to  FIG. 17 , which is a cross-section taken along line  17 - 17 ,  FIG. 16 . Referring to  FIG. 17 , the sidewall  402  is a jointed sidewall having segments  405  and  406 . The segments  405  and  406  may be generally as described above in connection with segments  261 ,  262 ,  FIG. 1 . It is noted that end  410  of the sidewall  402  is closed by a stepped cover  411  having outlet  412  projecting therefrom. The outlet  412  includes a tap  413  for a pressure sensor or similar arrangement. 
     More specifically, cover  411  is stepped at first step  415  and second step  416 . In use, the safety element is sealed to second step  416 . 
     Unlike the arrangement of  FIGS. 1-13 , there are no posts positioned in the step  416 , for securing a safety element in place. Rather adjacent region  416 , immediately between step  416  and  415 , are provided several space protrusions  420 . For the arrangement shown, there would be four protrusions  420 , equally radially spaced around an inner most edge of step  416 . The operation of these protrusions  420  will be understood from further description below. 
     Attention is now directed to  FIG. 18  which depicts a fragmentary view of a portion of the housing  401  depicted in  FIG. 17 , but with the safety element  430  mounted therein. The safety element  430  may be generally as characterized above for safety element  31 , except for mounting mechanism thereon, described herein. In particular, safety element  430  does not include any slots analogous to slots  206 . Rather safety element  430  only includes an o-ring receiver  431  with  432  therein. 
     During assembly, safety element  430  would be pressed toward step  416  in the general direction of arrow  440 , as the safety element is inserted into open end  445 ,  FIG. 17 , of the housing  401 . The safety element would continued to be pushed in the direction of arrow  440  until the o-ring  432  is sealed against an inner surface  416   a  of step  416 . In order to accomplish this sealing, the o-ring  32  would need to be pushed passed protrusions  420 . The protrusions, then, will act to cause an interference fit, prohibiting the likelihood that the safety element  430  would not intentionally become dislodged from its mounting,  FIG. 18 , by movement of the safety element in the direction of arrow  450 . The protrusions  420 , then, in combination with the outside diameter of the o-ring  43 , causes a lock fit of the safety element  430  in place, without requiring a twist motion. 
     Of course the mounting approach described with respect to  FIG. 16-18  could be applied with a non-jointed housing, if desired. 
     2. A first alternate cover mount. 
     An alternate cover mount is shown in  FIG. 19 . Referring to  FIG. 19  air cleaner assembly  500  is depicted, comprising a housing  501 , having an outer sidewall  502  and a cover  503  mounted thereon. Except for the approach of mounting, the cover  503  may be generally similar to cover  20 ,  FIG. 1 , including options described. 
     In particular, cover  503  is mounted onto end  505  of housing sidewall  502 , by over center wire latches  506 . This is opposed to using a latch mechanism such as the integral latch mechanism described for the embodiment of  FIGS. 1-13 . 
     It is noted that the arrangement of  FIG. 19  includes a pin or key  530  positioned on the cover, to be received within a slot  531  at end  505  of sidewall  502 , to ensure appropriate radial orientation of cover  503  relative to sidewall  502  during mounting. That is, cover  503  for the arrangement shown, can be mounted in only one radial orientation. 
     3. An alternate mounting arrangement for the primary element,  FIG. 20 . 
     In the arrangement of  FIGS. 1-13 , the primary element  30 , is mounted using a rotation lock mechanism  129 , as described. As a result, the primary element  30 , is sealed with an axial seal as described. 
     An alternate approach, which utilizes a radial seal mechanism, is possible, as previously indicated. One such arrangement is shown in  FIG. 20 . 
     Referring to  FIG. 20 , a fragmentary perspective view of an alternate primary element  600 , is shown. In  FIG. 20 , the portion of the element  600  viewable, is the end cap  601  that would correspond to the end cap that is inserted furthest into the housing, during use. In particular, end cap  601  is the exit end for filtered air. 
     End cap  601  is provided with a central axial protrusion  602  thereon, that projects axially away from a remainder  603  of the primary element  600 . The axial protrusion  602  includes an o-ring mount  605  with an o-ring  606  positioned thereon. With such an arrangement, the primary element  600  could be mounted by insertion past the protrusions  420 ,  FIG. 18 , in place of the safety element. That is, primary element  600  could be mounted analogously to safety element  430 ,  FIG. 18 . That result would be a radial seal formed by o-ring  606 , as opposed to an axial seal arrangement. 
     During normal mounting, the filter element  600  of  FIG. 20 , would not be twisted or rotated. Thus it may be preferable to manufacture primary element  600  without outside framework extending completely between the opposite ends. Rather, while shields may be at positions adjacent each end (or at least the outlet end) to facilitate use, it may be desirable to leave cross hatch open framework extending between the ends out, since it would not be needed to translate rotational motion and provide for support. This is a matter of choice, depending upon other features in the construction. 
     A safety element could be mounted in association with arrangement such as  FIG. 20 , by providing a structural location in region  610 , to allow for the safety element to be mounted. It is noted that for the particular arrangement of  FIG. 20 , internal (optional) open framework  612  is shown extending axially along inside  613  of the element  600 . The open framework  612  could extend from end to end, of the element  600 . 
     4. An alternate primary element with a precleaner mounted directly thereon. 
     For the embodiment of  FIGS. 1-13 , the precleaner  35  was mounted directly on the cover  20 . As indicated previously, alternate embodiments are shown. In particular, attention is directed to  FIG. 21 , in which a primary filter element  800  is depicted, in fragmentary, cross-sectional view. In particular, a closed end  801  of the primary filter element  800  is depicted. Closed end  801  is shown having framework  802  extending there across, with the receiver  803 , for engagement with the cover. The framework  802  is shown secured in place by end potting  805 . This closes the end of media  806 . As thus far described, the arrangement is generally analogous to the primary element  30  of  FIGS. 1-13 . However, for element  801 , shield  810  and ramp  813  are shown non-permanently as part of the primary filter element  800 , thus are not mounted on the cover.  FIG. 21  is presented simply to indicate an alternate arrangement in which a precleaner  815 , comprising of shield  810  and ramp  813  are used. In this alternate embodiment, the precleaner  815  is mounted directly onto the primary element  800 , as opposed to the cover. 
     The remainder of the assembly utilized with respect to precleaner  800  may be generally analogous to that described for the embodiment of  FIGS. 1-13 , or for the alternate embodiments described. 
     Of course as a still further alternate, the cover  20 , precleaner ( 135 ,  815 ) and element ( 30 ,  200 ) could be made permanently connected to one another. Possible modifications to accomplish this will be apparent from the general teachings herein. 
     5. A further alternate mounting arrangement for the cover,  FIGS. 22 and 23 . 
     Attention is now directed to  FIG. 22  in which an air cleaner assembly  900 , comprising a housing  901  with a side wall  902  having a cover  920  mounted thereon, as shown. The air cleaner  900  may be generally described for the arrangements above, except as characterized in this section. In particular, cover  920  includes, molded thereon, wire latch mounts  921 . Cover  920  further includes wire latches  922 , snap fit mounted to the mounts  921 . As a result, when disengaged, the latches  922  remain secured to the cover  920 , when the cover  920  is removed from the remainder of the housing  901 . When this function is conducted, the wire latches  922  double as handles, to facilitate handling the cover  920 . 
     The wire latches  922  shown, are configured to engage over a lip or similar structure of the housing  901 , to project through slots  925 ,  926  in the housing sidewall  902  and cover  920  respectively,  FIG. 23 , to provide for a secure engagement. 
     Referring to  FIG. 22 , it is noted that analogously to the arrangement of  FIG. 1 , the arrangement of  FIG. 22  is a jointed housing  930 , having two sections  931  and  932 . The connection between the sections  931  and  932  is a modification, from the arrangement of  FIG. 1 , but uses the same general principles. In particular, section  932  includes a skirt  933  thereon, which overlaps and circumscribes a portion of section  931 . The skirt  933  includes apertures  934  therein radially spaced. Each aperture  934  is sized to engage a projection  935  on section  931 , for lock engagement. Thus, an interlock mechanism  936  is provided comprising a projection ( 935 ) and receiver ( 934 ) arrangement. 
     A radial locater or indexed jointed mechanism arrangement using receiver  938  in skirt  933 , which overlaps a pin  939  on segment  931 , is also provided, similarly to the arrangement of  FIG. 1 . 
     It is also noted that the mounting mechanism  940  for the arrangement  900  of  FIG. 22 , differs in detail from the analogous arrangement for the embodiment of  FIG. 1 . However, its overall operation is similar. 
     J. The Arrangement of  FIGS. 24-27 . 
     An improved arrangement is depicted in  FIGS. 24-27 . In  FIG. 24 , air cleaner assembly  1100  is depicted comprising a housing  1101 . The housing  1101  is generally analogous to housing  901 ,  FIG. 22 , except as characterized in this section. It is noted that the housing  1101  of  FIG. 24  is schematic. 
     Referring to  FIG. 24 , access or service cover  1110  differs from cover  920 , in that no central recess is present. Further, access or service cover  1110  includes a notch  1111  associated with a key or pin  1112 , at a different location, than the arrangement of  FIG. 22 . Also, underneath latch  1120  access or service cover  1110  includes a notch or slot  1121 , in outer rim  1122  for receipt of pin, key or projection  1123  on the remainder of the housing  1101 . Thus, slot  1121 /key  1123 , along with slot  1111 /key  1112 , provide for preferred rotational indexing between the cover  1110  and the remainder of the housing  1101 . 
     Still referring to  FIG. 24 , mounting arrangement  1130 , for securing the housing  1101  to a vehicle or the equipment, is also modified from the arrangement of  FIG. 22 . 
     Attention is now directed to  FIG. 25 . Here the inside surface  1140  of cover  1110  is viewable. It is noted that instead of having an “X” or plus-shaped (“+” shaped) projection, as shown for previous arrangements, the cover  1110  includes, along internal surface  1140 , a projection arrangement comprising four posts  1141  arranged as the corners of an “X” or plus-shape, to be received within a non-circular, preferably “X” or plus shaped recess, not shown, in the primary or main filter cartridge  1145 . With respect to this feature, cartridge  1145  may have an “X” or plus shaped receiver analogous to the cartridge depicted in  FIG. 4 . The posts  1141  each have curved outside surfaces, approximately as half of a cylinder, or cone to facilitate engagement. The four posts  1141  allow for four possible rotational positions of the cartridge  1145 . Of course fewer posts (1, 2 or 3) could be used to accomplish the same type of effect, if properly positioned. 
     Still referring to  FIG. 25 , primary cartridge  1145  also includes central circular rib  1146  thereon. The rib  1146 , as seen in  FIG. 26 , would preferably extend completely around cartridge  1145  at a central location, and in a direction generally orthogonal to a central axis of the cartridge  1145 . The rib  1146  provides a projection that can be engaged by equipment, during manufacture. It is not expected that rib  1146  will provide significant function, in the assembled and operating air cleaner. However, it will add some strength to the open frame work around the outside of primary cartridge  1145 . 
     In  FIG. 27 , a cross-sectional view of the air cleaner assembly  1100  is shown. From a review of  FIG. 27 , it can be seen that a secondary or safety filter  1150  for the assembly  1100  is constructed shorter than the safety filter depicted in  FIG. 2  at  31 . Thus, at end  1151  filter  1150  does not include a receiver, to engage protection  1152  in the primary filter cartridge  1145 . 
     In  FIG. 27 , an improved alternative for securing the media in a secondary or safety filter  1150  is also provided. In particular, in safety filter  1150 , the media  1155  is secured within the framework  1156 , during molding. That is, the media  1155  is positioned in the mold, and the plastic framework  1156  is molded but with the media  1155  in place. Thus, as shown, the spaced axial ribs  1157  of the safety filter  1150  each have central portion where the conical media  1155  passes through them to extend between them over the openings  1158 . Of course, if it desired to use the framework of the safety filter  1150  without the media  1155 , the same molded configuration can be used, but without the media present. 
     Referring to  FIG. 24 , it is noted that the housing  1101  does not include a rotational joint at seam  1160 . It has been determined that during manufacture, the mold for housing  1101  can be constructed such that the portion in which region  1162  is molded, can be made rotatable relative to the portion in which region  1163  is molded. Thus, variations in rotational orientation between the air inlet and the dust ejector outlet can be accommodated during the molding process, by using a method involving a mold which has two parts rotatably moveably relative to one another. Seam  1160  is positioned with a joint between the two mold segments would be located. 
     Referring to the cross section of  FIG. 27 , it is noted that the safety element  1150  includes o-ring seal  1170 ; and, an extension  1171  positioned axially toward outlet  1175  for a remainder of the safety element  1150 . Extension  1171  can facilitate mounting and engagement. 
     In other manners, the assembly  1100  may be constructed in accord with the descriptions and variations presented herein, in association with other embodiments. Also, the improvements described for assembly  1100  can be applied in the other embodiments. 
     K. The Arrangement of  FIGS. 28-33 . 
     A further improved arrangement is depicted in  FIGS. 28-33 . The air cleaner assembly  1100  depicted in these FIGS., and the subcomponents thereof, may be generally analogous to the arrangements depicted in  FIGS. 24-27  and in other previous FIGS., discussed above. Focus in this section will be with respect to certain specific preferred features. It will be understood, that, in general, components similarly positioned and depicted in the figures provide for analogous operation to those of previously described figures. 
     In  FIG. 28  an assembly  1500  is depicted, including a housing  1503  having an air inlet  1505 , an air outlet  1506 , and dust ejector drop tube  1507 . The assembly  1500  also includes optional mounting structure, legs or supports  1508  thereon, to facilitate mounting. As with other arrangements described above, the assembly could alternatively be mounted by a separate mounting band or bracket. 
     Referring to  FIG. 28 , the housing  1503  has first and second opposite ends  1516  and  1517 . End  1516  is closed by a cover portion  1518  having outlet tube  1506 , in this instance an axial outlet tube, projecting therefrom. Referring to  FIG. 28 , for the arrangement shown cover  1518  is integral with (i.e., is not separable from), end  1516 . 
     End  1517 , the other end, is generally an open, service, end closed by openable cover  1520 . The cover  1520  is removable, for service access to an interior of housing  1503 . 
     The cover  1520  is secured in place by latches  1523  and  1524 , mounted on mounts  1523   a  and  1524   a , respectively. The cover  1520  is rotationally indexed, by a rotational index or indexing arrangement, so that it can only be secured in place at one orientation. For the cover  1520 , indicia  1525  is provided, to indicate a convenient orientation of the cover  1520  during servicing. In particular, the indicia  1525  chosen, is an arrow that points in the direction of the inlet  1505 . 
     For the particular assembly  1500  depicted, portion  1500   a  of the housing is secured to portion  1500   b , at seam  1500   c . Portion  1500   a  is non-rotatable relative to portion  1500   b . However the mold from which the two portions are formed, can be provided with a rotatable joint at a portion corresponding to  1500   c , so that the two pieces  1500   a  and  1500   b  can be molded as a single unit, with any preferred rotational orientation of section  1500   a  relative to section  1500   b , that is desired. Rotation is generally selected so that the inlet tube  1505  has an orientation preferred for particular equipment which the air cleaner  1500  is to be used. For the particular example shown in  FIG. 28 , the inlet tube  1505  projects in a direction parallel to the arrow of indicia  1525 , and in a general direction parallel to the direction of dust drop tube  1507 , although alternatives are possible. 
     Rotational indexing of the cover  1520  on the housing  1528 , can be provided by a variety of structures. Referring, for example, to  FIG. 29 , at open end  1517  housing  1503  is provided with outer key or projection  1530  which, during assembly, is received within receiver or slot  1531  on cover  1520 . Also, on cover  1520  a key or projection  1533  is provided, which is received within receiver or slot  1534  on housing  1503 . Further the cover  1520  includes thereon keys or projections  1536  and  1537 ,  FIG. 30 , received within slots or receivers  1538  and  1539 , respectively,  FIG. 29 , during assembly. Finally receiver or slot  1540  is shown,  FIG. 29 , to receive a similar key or projection to projections  1533 ,  1537 , and  1536 , appropriately rotationally positioned on cover  1520 ,  FIG. 29 , but not viewable. 
     Attention is directed to  FIG. 30 , which shows an inside surface  1540  of cover  1520 . Projecting centrally, internally, cover  1520  includes a plus (or “+”) shaped projection  1541 , which, in use, is received within a plus (or “+”) shaped receiver,  1550  on a primary filter element  1551 , in use. 
     Referring to  FIG. 30 , the plus (or “+”) shaped projection  1541  depicted, has a generally hollow interior  1541   a  and is open in direction toward an interior of air cleaner  1500 . 
     Of course engagement between the plus (or “+”) shaped projection  1541  and the plus (or “+”) shaped receiver  1550 , prevents rotation of primary element  1551 , after assembly and in operation. The plus (or “+”) shape allows for four possible rotational orientations between the cover  1520  and the primary element  1551 , although alternatives are possible. 
     As indicated previously for other arrangements described, preferably a projection analogous to projection  1541  is provided on an inside surface  1540  of the cover  1520 , to engage an appropriately shaped receiver on an end of the primary filter element  1551 . The particular “+” shape chosen, is an example. Preferably the shape chosen will be one that does not allow rotation of the element  1551  relative to the cover  1520 , once engagement occurs. Thus, preferably the projection is not round, and the receiver is not round. 
     Attention is directed to  FIG. 29 . For the particular arrangement shown, positioned to be received projecting inside of primary element  1551 , is support structure  1560 . The support structure may be a component of a secondary filter element, or it may simply comprise framework to support an interior of media contained within primary filter element  1551 . Thus, support structure  1560  may be analogous to structure of safety element  1150 , described above in connection with  FIGS. 24-27 . 
     A difference between support structure  1560  and the previously depicted support structure, is provided at closed end  1561 ,  FIG. 29 . In particular, at closed end  1561 , central recess  1563  is depicted, in extension across end  1561 . 
     In general, it is anticipated that structure  1560  will be injection molded. A convenient location for introduction of plastic into the injection mold, is in center  1564  of end piece  1561 . Such a molding operation will leave a small projection or burr of plastic at center  1564 . Shaping the mold to form recess  1563 , ensures that the burr or projection of plastic at center  1564  is contained within the recess  1563 . This means that as an operator&#39;s hand is pressed against end  1561 , burr  1564  is recessed, and provides less discomfort to the operator during installation. 
     Attention is now directed to  FIG. 32 , in which the serviceable primary filter element of  1551  is depicted in side elevation. In general, it has componentry similar to the embodiment described above in connection with  FIGS. 24-27 . That is, it includes an outer support structure  1580 , preferably having an imperforate shield region  1581  and a porous, perforated or open region  1582 , around which framework  1583  is provided. The element includes open end  1590 , closed end  1591 , and media  1592  extending therebetween. Optional central circular projection  1593  is to facilitate machine handling, during certain manufacturing steps. 
     The media  1592  may comprise a variety of types of media. For the example shown the media  1592  is pleated media  1594 . 
     The particular primary filter element  1551  depicted, has a conical shaped portion, thus at region  1595 , the media  1592  is provided with a slightly larger outside diameter, than at end region  1596 , analogously to previously described embodiments. The conical shape may be as previously described, for other embodiments. 
     At end  1590 , a compressible axial seal gasket ring  1600  is depicted. The ring  1600  may be similar to ring or rib  70 ,  FIG. 5 , preferably comprising a compressible polyurethane foam and preferably having a hardness of no greater than 30 Shore A. 
     Primary filter element  1551  also includes optional dust shield  1610  thereon, as a circular outwardly projecting ring spaced from end  1590 . This is analogous to structure shown in the embodiment of  FIGS. 24-27 . 
     Mounting structure  1620  is positioned on framework  1580  at a location between shield  1610  and end  1600 . 
     The mounting structure  1620  comprises spaced projections  1621 , configured to operate analogously to spaced projections in the previous embodiments. Projections  1621 , however, have a somewhat different shape, as viewable in  FIG. 32 , from the arrangement of  FIG. 26 . 
     In particular, projection  1621  includes opposite surfaces  1623 ,  1624  extending between ends  1625  and  1626 . 
     Surface  624  is configured to engage a projection or holder structure in a housing, during a twist lock operation to secure element  1551  in place, analogously to the operation described above for other embodiments. 
     Surface  1624 , then, is preferably provided with a cam surface  1630 , which recesses (in extension from tip  1625 ) toward dust ring  1610  or end  1591 , from end  1590 . The cam surface  1630  ends at surface portion  1631  which itself terminates at stop  1632 . Thus, during operation, element  1551  will be pushed into the housing, until tip  1625  passes a holder, lug or projection analogous to projections  140 ,  FIG. 9 . Rotation of element  1551  will bring tip  1625  around the projection, for engagement between cam surface  1630  and the projection. Continued rotation will bring the projection along surface  1631  until stop  1632  is encountered by the holder, lug or projection in the housing. 
     Unlike the arrangement of  FIG. 26 , projections  1620  do not have tails extending radially around surface  1640 , toward a next adjacent projection. This leaves a larger (relative) gap between end  1626  and a tip  1625  of a next adjacent projection  1620 . Preferably at an angular spacing of at least 20°, more preferably at least 35°-70°, is provided, for convenient assembly. 
     In  FIG. 33 , framework  1583 , for forming primary filter element  1551  is depicted. The framework  1583  of  FIG. 33  could be analogous to the framework depicted in  FIG. 26 . 
     Still referring to  FIG. 32 , in general mounting structure  1620 , then, comprises a portion of a non-continuously treaded rotational interlocking arrangement, when used in association with appropriate projection or holder arrangement on a housing. Further, the mounting structure  1620  comprises a segmented ring of projections or segments  1621 , each of which is radially spaced from a next adjacent one; and, each of which is preferably integral with (i.e., molded as part of) framework  1580 . The number of projections, generally indicate the number of rotational orientations possible for the primary element  1551 , in a housing  1503 ,  FIG. 28 . 
     In  FIG. 33 , outer framework or outer support structure  1580  usable to form primary filter element analogous to element  1551 ,  FIG. 32 , is depicted. The framework  1580  may be used, in assembly, analogously to the discussed above for  FIG. 8 . 
     With respect to  FIG. 33 , attention is directed to end  1640 , to be covered by an end cap, in use. End  1640  has an open (or perforate) portion  1641  generated by framework  1642 , in particular radial pieces  1643  and central piece  1644 . 
     In a central region end  1640  includes closed (imperforate) portion  1650  having central receiver or recess  1645  therein. The particular central recess  1645  depicted, has a plus (or “+”) shape, for receiving a projection on the cover in use. 
     In use of framework  1580 , to manufacture an element, pleated media would be positioned inside the framework  1580 , with an end engaging framework  1642 . Potted end caps would be formed at the opposite ends  1640 ,  1670 , with the end cap or potting at end  1670  being open, and defining the axial seal  1600 ,  FIG. 32 . The media will be supported along an inside adjacent framework  1642 , by surrounding central portion  1650 , which projects into the open center of the framework  1580 . 
     At end  1640 , the material will be potted into end cap material (or potting), to cover the opened area  1641 , without covering the central portion  1650  and recess  1645 . The result would be structure analogous to that shown and discussed above, for example with respect to  FIG. 4 . 
     For convenience, in  FIG. 31  a cross-sectional view of assembly  1500 ,  FIG. 28 , is depicted. This view is analogous to the view of  FIG. 3 . In it, primary element  1551 , support  1560 , housing  1503  and cover  1520  are viewable. 
     Above it was mentioned that the inner support  1560 , could comprise a support of a secondary filter, for example as described above for other embodiments. 
     Attention is now directed to  FIG. 31 . In  FIG. 31 , it can be seen that when latched, the latches  1523  each include a projection  1523   b , which extends through both a portion of the housing  1503  and a portion of the cover  1520 , during latching. This is analogous to the arrangement shown above, in  FIG. 27 . 
     Referring to  FIG. 29 , it is noted that inner support  1540  includes o-ring  1700  thereon, for sealing, radially, in the housing, during use. This sealing is depicted in  FIG. 32 . 
     L. Materials and Construction. 
     Principles according to U.S. application Ser. No. 10/691,856 and PCT Application US 03/33952 can be implemented in a variety of sizes, shapes and configurations of equipment, and using a variety of materials. However, the principles were developed for application in preferred arrangements and configurations, and with certain preferred materials. 
     For example, in general the configurations shown will be particularly advantageous for use as an air cleaner for a vehicle having an air flow demand, at rated operation, the order of about 1,500 cubic feet per minute (cfm) or less, typically about 300 cfm or less; i.e., on the order of 43 cubic meters or less, typically about 9 cubic meters or less. These types of air cleaners are generally found on equipment that uses small gas or small diesel engines. 
     The typical air cleaners used in such applications, would have an overall outside diameter of the housing, on the order of at least 130 mm., typically 130-170 mm.; and a housing sidewall length of at least 300 mm. typically from 300 mm. to 600 mm. (i.e., distance between ends  16  and  17 ),  FIG. 1 . The outer support  90  of primary filter cartridge  30 , would have a largest outside diameter D 1 , of at least 120 mm., and smallest outside diameter D 2  on the order of about 110 mm. or less, with a conical angle or taper (i.e., angle A,  FIG. 6 , where dotted line  950  is parallel to central axis  12 ,  FIG. 3 ) between the ends, extending at an angle on an order of at least 1° typically within the range of 2° to 4°, and with an overall length of at least 100 mm. and typically 110-150 mm. The aperture  102 ,  FIG. 8 , would have a diameter of at least 115 mm., typically 118 mm. to 125 mm. 
     In general, dimension materials for the rib  70  and the interlock arrangement  129 , should be selected to provide for a compression of rib  70  of at least 0.5 mm., typically 1-2 mm., in use. The desirable material for rib  70 , and indeed end cap  92 , is a foamed polyurethane preferably to be selected to have a hardness, Shore A, of no greater than about 30, and preferably no greater than about 22, most preferably below 20. 
     Preferably with such arrangements, the polyurethane formulation chosen provides for a high foam, very soft, molded end cap. 
     Preferably the formula chosen will be such as to provide end caps (parts molded from the polyurethane) having an as molded density of no greater than 28 lbs./cubic foot (about 450 kilograms/cubic meter), more preferably no more than 22 lbs./cubic foot (355 kilograms/cubic meter), typically no greater than 18 lbs/cubic foot (290 kilograms/cubic meter) and preferably within the range of 13 to 17 lbs/cubic foot (208-275 kilograms/cubic meter). 
     Herein the term “as molded density” is meant to refer to its normal definition of weight divided by volume. A water displacement test or similar test can be utilized to determine volume of a sample of the molded foam. It is not necessary when applying the volume test, to pursue water absorption into the pores of the porous material, and to displace the air the pores represent. Thus, the water volume displacement test used, to determine sample volume, would be an immediate displacement, without waiting for a long period to displace air within the material pores. Alternately stated, only the volume represented by the outer perimeter of the sample need be used for the as molded density calculation. 
     In general, compression load deflection is a physical characteristic that indicates firmness, i.e. resistance to compression. In general, it is measured in terms of the amount of pressure required to deflect a given sample of 25% of its thickness. Compression load deflection tests can be conducted in accord with ASTM 3574, incorporated herein by reference. In general, compression load deflection may be evaluated in connection with aged samples. A typical technique is to measure the compression load deflection on samples that have been fully cured for 72 hours at 75° F. or forced cured at 190° F. for 5 hours. 
     Preferred materials will be ones which when molded, show a compression load deflection, in accord with ASTM 3574, on a sample measured after heat aging at 158° F. for seven days, on average, of 14 psi or less, typically within the range of 6-14 psi, and preferably within the range of 7-10 psi. 
     Compression set is an evaluation of the extent to which a sample of the material (that is subjected to compression of the defined type and under defined conditions), returns to its previous thickness or height when the compression forces are removed. Conditions for evaluating compression set on urethane materials are also provided in ASTM 3574. 
     Typical desirable materials will be ones which, upon cure, provide a material that has a compression set of no more than about 18%, and typically about 8-13%, when measured on a sample compressed to 50% of its height and held at that compression at a temperature of 180° F. for 22 hours. 
     In general, the compression load deflection and compression set characteristics can be measured on sample plugs prepared from the same resin as used to form the end cap, or on sample cut from the end cap. Typically, industrial processing methods will involve regularly making test sample plugs made from the resin material, rather than direct testing on portions cut from molded end caps. 
     Urethane resin systems useable to provide materials having physical properties within the as molded density, compression set and compression load deflection definition as provided above, can be readily obtained from a variety of polyurethane resin formulators, including such suppliers as BASF Corp., Wyandotte Mich., 48192. 
     One example usable material includes the following polyurethane, processed to an end product having an “as molded” density of 14-22 pounds per cubic foot (224-353 kilograms/cubic meter). The polyurethane comprises a material made with I36070R resin and I3050U isocyanate, which are sold exclusively to the assignee Donaldson by BASF Corporation, Wyandotte, Mich. 48192. 
     The materials would typically be mixed in a mix ratio of 100 parts I36070R resin to 45.5 parts I3050U isocyanate (by weight). The specific gravity of the resin is 1.04 (8.7 lbs/gallon) and for the isocyanate it is 1.20 (10 lbs/gallon). The materials are typically mixed with a high dynamic shear mixer. The component temperatures should be 70-95° F. The mold temperatures should be 115-135° F. 
     The resin material I36070R has the following description: 
     (a) Average molecular weight
         1) Base polyether polyol=500-15,000   2) Diols=0-10,000   3) Triols=500-15,000       

     (b) Average functionality
         1) total system=1.5-3.2       

     (c) Hydroxyl number
         1) total systems=100-300       

     (d) Catalysts
         1) amine=Air Products 0.1-3.0 PPH       

     (e) Surfactants
         1) total system=0.1-2.0 PPH       

     (f) Water
         1) total system=0.2-0.5%       

     (g) Pigments/dyes
         1) total system=1-5% carbon black       

     (h) Blowing agent
         1) water.       

     The I3050U isocyanate description is as follows: 
     (a) NCO content-22.4-23.4 wt % 
     (b) Viscosity, cps at 25° C.=600-800 
     (c) Density=1.21 g/cm 3  at 25° C. 
     (d) Initial boiling pt.-190° C. at 5 mm Hg 
     (e) Vapor pressure=0.0002 Hg at 25° C. 
     (f) Appearance-colorless liquid 
     (g) Flash point (Densky-Martins closed cup)=200° C. 
     The material selected for the media may be varied, depending on the anticipated environment of use and availability of various pleatable substrates. 
     Conventional media available from such suppliers as Hollingsworth and Vose of East Walpole, Mass. can be utilized. It is anticipated that in typical arrangements, pleats  85  in the order of ⅜ inch to 3 inches (0.9 cm to 7.6 cm) in depth, with a pleat population, around the inner diameter, of about 10 to 14 per inch at the larger diameter end (15 to 20 per inch at the smaller diameter end) with a conical unit being used. 
     The principal structural component of the primary filter cartridge  30 , i.e., support  90 , will generally be made from a rigid plastic such as a glass filled nylon (for example 33% glass filled nylon 6/6, 1.5 mm. thick). Such a component could generally be made by a plastic molding operation, for example injection molding. 
     Support structure  160 , which operates as either an inner support for the primary filter cartridge  30  or as both an inner support for the primary filter cartridge  30  and an outer support for a optional safety cartridge  31 , will generally be formed from a rigid plastic similar to that used for support  90  formed using a similar molding process. The media  65  or the safety filter cartridge  31  is a matter of preference for the particular application, and it would typically be non-pleated media with a side coated with a selected surface modifier, such as a tackifier. 
     Preferably both the primary filter cartridge and the secondary filter cartridge at least 98%, by weight, metal free, most preferably 100% metal free. 
     The housing sidewall segments  261  and  262  (or for the embodiment  300  of  FIG. 14 , sidewall segment  301 ), are preferably molded from plastic materials such as a glass filled nylon (for example 33% glass filled nylon 6/6, 2 mm. thick). For these components an injection molding process could be used. Preferably each of the components (except where possibly reinforced by a metal grommet to receive bolts for connection to other components such as a truck frame and/or the latches) is at least 98%, by weight, metal free, preferably 100% metal free. Metal grommets might be utilized, for example, inside of mounting legs  8  or tap  6   a.    
     Cover  20  for the particular preferred embodiment shown, is sized and shaped so that it can be molded from plastic materials. It is anticipated that in general the precleaner  35 , comprising shield  37  and ramp  36 , would be premolded for example from glass filled nylon or polypropylene by an injection molding process, and would then be attached to a remainder of the cover  20 , for example by heat staking, with an adhesive or with a snap (mechanical) fit. 
     The remainder of the cover  20 , would preferably be molded from the same material as used for housing segments  261 ,  262 , in an injection molding process. The latches  171  could be molded integrally with cover  20  in such a process. The cover  20  is preferably at least 98% metal free, most preferably 100% metal free. 
     The inlet tube  5  would typically have an inside diameter on the order of about 50 to 200 mm., for example about 60 mm., and the outlet tube  6  would have an inside diameter of about the same. The down tube  7  would have an inside diameter on the order of about 45 to 55 mm., for example about 51 mm. 
     Typically and preferably the ramp  36  would extend through a rotation of about 150°-280° from end  400  to end  401 ,  FIG. 5 , and would extend longitudinally along sidewall  9  over a distance of at least as wide as the diameter of the entrance to tube  5 , preferably slightly more. 
     The above dimensions, materials and specific described shapes, are meant to be exemplary only, and are not intended to be limiting unless specifically characterized as such. It will be apparent from the above, however, how the various techniques and improvements described in U.S. application Ser. No. 10/691,856 and PCT Application US 03/39952 can be applied in a wide variety of contexts and specific applications. 
     II. Air Cleaner and Componentry Configuration, FIGS.  34 - 38   
     The reference number  2000 ,  FIG. 34 , depicts an air cleaner according to the present disclosure, in cross-sectional view. The air cleaner  2000  comprises a housing  2001  having a body section or body  2002  with an open end  2002   a  closed by a removable access cover  2003 . Although alternatives are possible, analogously to the cover disclosed in previous descriptions relating to  FIGS. 1-33 , cover  2003  is secured in place on body  2002  by latches, an example latch being shown at  2004 . Cover  2003  would preferably be provided with a rotational indexing arrangement (such as a slot and key arrangement) similar to those described for previous figures. Cover  2003  preferably includes a precleaner arrangement similar to those previously described and comprising: shield  2005 , projecting into interior  2002   b  of body  2002  from end  2002   a . Shield  2005  includes an air flow ramp arrangement  2006  thereon, to impart a cyclonic or circular motion around shield  2005 , from air passing into interior  2002   b  through air flow inlet  2010 . Inlet  2010  is preferably a tangential flow inlet. 
     Still referring to  FIG. 34 , air cleaner  2000  includes, secured therein, a primary filter element or cartridge  2020 . The primary filter element  2020  comprises filter media  2021  secured in extension between opposite end caps  2022  and  2023 . End cap  2022  is a closed end cap. End cap  2023  is an open end cap. Thus air flow which passes through media  2021  into interior  2025 , defined by filter cartridge  2020 , can eventually pass outwardly from region  2025  through axial clean air outlet  2028  of air cleaner body  2002 . 
     Although alternatives are possible, for the particular example shown, media  2021  is pleated media  2029  positioned in extension between an outer liner  2030  and an inner liner  2031 . Expandable metal liners can be used for liners  2030  and  2031 , although alternatives are possible. In some applications, one or both of the liners may be avoided. However, liners are preferred, for providing structural integrity, especially for larger elements. 
     Although alternatives are possible in some applications, for the particular arrangement shown in  FIG. 34 , closed end cap  2022  comprises: (a) molded-in-place ring  2034 ; and, (b) central, preformed, bowl or projection arrangement  2036 . The central projection is generally preformed and is then partially embedded within ring  2034 ; during molding of ring  2034 . A preform with features of this general type is described in U.S. application Ser. No. 10/721,934, filed Nov. 24, 2003, published as 2004/0103787 A1 on Jun. 3, 2004, incorporated herein by reference. Referring to  FIG. 34 , it is noted that projection  2036  extends axially, inwardly from a location near end  2038  of media  2021 , toward opposite end  2039 . In a central region  2040 , projection  2036  includes a reverse frusto-conical section  2041 , which projects, axially, back toward cover  2003 . Projection  2036  can be, thus, viewed as a bowl, with a central conical projection  2041 . 
     In a central region, cover  2003  includes a projection  2045  extending axially inwardly of cartridge  2020 , in particular into the bowl  2036 ; with a central portion including a reverse, axial, frusto-conical projection (with matching recess)  2046 , sized to receive projection  2041 . Such a mating projection arrangement between projections  2036  and  2045 , can help ensure that cover  2003  is appropriately positioned, and cartridge  2020  is appropriately positioned. Preferably, projection  2045  has a non-circular outer perimeter (for example pentagonal, hexagonal, heptagonal or octagonal). Preferably projection  2036  has a circular perimeter in cross-section (i.e., conical shape) in region  2036   a , adjacent media  2021 . 
     For the particular air cleaner  2000  depicted, primary filter element or cartridge  2020  is generally conical (or frusto-conical) in shape, having the media  2021  defining a larger outer perimeter, diameter or dimension at end  2039  than at end  2038 . Thus a narrow end  2038  of the conical cartridge  2020  is projected into shield  2005 , to be surrounded thereby. 
     Preferably, shield  2005  extends axially along cartridge  2020  at least 10% of its axial length, preferably at least 20% of its axial length and most preferably at least 25% of its axial length. 
     Still referring to  FIG. 34 , end cap  2023  preferably comprises a molded (typically polyurethane) end cap, forming an outer, annular, radial seal at  2060 , for sealing within annular surface  2061  in housing body  2002 . The annular sealing surface or region  2060  in end cap  2023  could be provided with a tapered shape, for example a stepped shape as shown in  FIG. 35 , to a narrow size near tip  2060   a  to facilitate sealing. A soft compressible urethane as previously characterized herein could be used for end cap  2023 , although alternatives are possible. 
     End cap  2023  includes radially spaced axial bumpers or projections  2065  thereon, to provide for tolerance take up at length. Bumpers  2065  can be segments of a ring, as shown, although alternatives are possible. Similarly end cap  2022  has humps or projections at  2070 . The projections  2065  and  2070  need not have the same size or shape. 
     Although alternatives are possible, in the particular example shown, end cap  2023 , when installed, does not form an axial seal with any portion of the housing  2001 , nor does it form an internal radial seal with any portion of the housing  2001 . Thus, it (and the associated cartridge) can be said to be “axial seal free” and “inside radial seal free,” when in the preferred form of  FIG. 34 . 
     Still referring to  FIG. 34 , positioned within interior space  2025 , for the particular air cleaner  2000  depicted, is a secondary or safety filter  2080 ; the filter  2080  comprising media  2081  extending between opposite end caps  2082  and  2083 . End cap  2083  is a closed end cap, with no aperture therethrough. It includes an axial projection  2084  having a generally frusto-conical shape, in this instance of circular cross-section, positioned to extend axially into projection  2040 , of the main element  2020 , and away from end cap  2082 . This will help center the main element  2020 , and support the safety element  2080 . 
     Although alternatives are possible, the media  2081  can be positioned between inner and outer support liners  2080   a ,  2080   b , as shown. Expanded metal liners, or alternatives, can be used. Pleated media for media  2081  can be used, but alternate media types can also, in some instances. 
     End cap  2082  is an open end cap, having an air flow aperture  2088  therein. Surrounding aperture  2088  end cap  2082  provides for an outer annular radial seal surface at portion  2089 , for radially sealing on housing axial flange  2090 , in housing body  2002 , via an outside or annular radial seal. Although alternatives are possible, preferably end cap  2082  is configured to only form the outside radial seal shown, and to form no axial seal or inside radial seal with any portion of the air cleaner  2000 , although alternatives are possible. Thus, for the preferred arrangement shown, safety or secondary cartridge (element)  2080  and end cap  2082 , are both “axial seal free” and “inside radial seal free.” 
     Still referring to  FIG. 34 , a dust drop tube is shown at  2095 . In operation, air would enter through inlet  2010 , which could, in some applications, be positioned at a different rotational location from where located. The dust would be directed into the cyclonic precleaner arrangement including ramp  2006 , to be directed in a cyclonic flow, similarly to the descriptions with respect to previous figures. Again, the cover  2003  can be provided with rotational indexing, to provide a proper orientation for the ramp  2006  relative to the inlet  2010 . The dust would in part be driven through region  2097 , toward dust drop tube  2095 , for ejection. Air would be filtered by passage through filter cartridge  2020 . It would then pass through safety cartridge  2080 , and outwardly through outlet tube  2028 . 
     Still referring to  FIG. 34 , main cartridge  2020  includes, adjacent end  2050 , a preform shield construction  2100  comprising: (i) an axial extension or shield  2101 , which in the arrangement shown generally has a circular cross-section and a somewhat frusto-conical shape; and, (ii) an outwardly (radially) projecting ring or flange  2102 , which, in the example shown, is a circular ring. The ring or flange  2102  is generally positioned to stop dust from entering the seal region  2104  of the main element  2020 , adjacent a region of body  2001 , where dust ejector  2095  is located. The flange preferably extends outwardly at least 5 mm, for example 5-15 mm, from the axial shield or extension  2101 . 
     Axial extension  2101  operates as a shield or axial shield portion, extending around cartridge  2020 , at this location. The preform  2100  would generally have an end portion embedded within end cap  2023 , during assembly, as shown. Typically, the preform  2100  does not extend completely between the opposite end caps  2022 ,  2023 . 
     Preferably axial extension  2101  extends, axially, a distance at least 5% of the axial length of cartridge  2020 , typically and preferably at least 15% of that length, from flange  2102  away from end cap  2082  and toward an opposite end of cartridge  2080 , i.e., toward end cap  2083 . 
     The end cap materials for end caps  2065  and ring  2022 , may, in many instances, comprise a soft, compressible, foamed polyurethane such as previously described herein. End cap preform  2036  generally will be formed from a more rigid plastic such as a polypropylene, nylon or similar material. 
     Similarly, end cap  2082  could be formed from a soft, foamed, polyurethane as characterized herein, with end cap  2083  typically being formed from a harder molded material, an example being a harder form of polyurethane. 
     In  FIG. 35 , filter cartridge  2020  is depicted, with a portion broken away for sectioning. In  FIG. 36  an end view of end cap  2022  is depicted. 
     It is noted that no twist-lock connection, or rotationally actuated connection, is provided between cartridge  2020  and housing  2001 . Thus the preferred cartridge  2020  can be said to be free of such components, or can be characterized by similar terms. 
     In  FIG. 37  a side view of safety element  2080  is depicted, with a portion sectioned away. In  FIG. 38 , an end view directed toward end cap  2083 , is depicted. 
     It is noted that in  FIG. 34 , certain portions of the deformable polyurethane of end caps  2023  and  2082  are depicted as if they are not deformed. These show, by the drawn overlap with the associated housing portions, where the end cap deformation during sealing can be made to occur, and to what extent, for the example embodiment shown. 
     Although alternatives are possible, the following dimensions are indicative of an example application of the principles described herein in connection with  FIGS. 34-38 . For the main filter element or cartridge  2020 , an overall length of 511.4 mm, not counting axial bumps on the outer surfaces of the end cap; each of the bumps being about 6-8 mm high, providing for a total length including the bumps of about 525-528 mm. The largest outside dimension, of the radial seal end cap  2023 , would be about 298 mm. The largest outside diameter of the closed end cap  2022 , would be about 244 mm. From this, the taper of the cone shape, for the example shown can be determined, although it can also be measured from the drawings. 
     Other example dimensions would include 70-80 mm, for a distance of shield section  2101  axially toward end cap  2022 , from ring  2102 ; a depth of at least 15 mm, typically at least 20 mm and usually about 40-45 mm, for a deepest extension inwardly of projection  2036 , from an outside surface of end cap  2022 ; an axial extension of about 10-20 mm, for axial projection of region  2041  back toward cover  2003 , from a deepest point of projection inwardly of region or bowl  2036 . For the safety element  2080 , an example dimension for projection  2084  axially, for a remainder of end cap  2083 , at an outer surface thereof, would be about 15-25 mm. 
     The extent of projection of portion  2045  into cartridge  2020 , i.e., into bowl  236  would typically be at least 15 mm, often at least 20 mm. Projection  2041 , on the main cartridge  2020 , would extend axially outwardly at least about 10 mm, with a similar amount of projection (at least 10 mm) a portion  2084  of end cap  2083 . 
     An example of a conical angle for an outside surface of the main filter cartridge  2020  would be tapering inwardly, from end cap  2023  toward end cap  2021  at an angle of at least 1°, typically about 1-10°, for example about 2-7°. A similar angle could be used for the safety element  2081 . 
     It is noted that for the primary filter cartridge  2020  depicted, shield structure  2100  is a preformed piece separately made from liner  2030 , both being embedded in end cap  2022 , to be secured in the filter cartridge. 
     Other relative dimensions of the preform and end caps, for the main filter element as well as other dimensions of the housing can be evaluated from  FIGS. 34 and 35 , using scale based on the above described dimensions. 
     With respect to the safety element, an overall length of about 475 mm, not counting projection  2084 , with projection  2084  extending about an additional 21 mm. The largest outside diameter of the open, outside radial seal, end cap  2082  would be about 150.9 mm. Other example dimensions can be drawn from the drawing, based on the scale stated, for an example. 
     Of course alternatives to these dimension are possible, the example dimensions merely provide an example. 
     Although alternatives are possible, it should be understood that these example dimensions indicate the present features are adapted for application, if desired, in relatively large air cleaners, for example in which the primary filter element or cartridge  202  has an axial length of at least 450 mm, and a largest outside diameter (dimension) of at least 250 mm. 
     III. Additional Air Cleaner and Componentry Configuration, FIGS.  39 - 47   
     The reference numeral  2500 ,  FIG. 39 , depicts another embodiment of an air cleaner according to the present disclosure, in cross-sectional view. The air cleaner  2500  comprises a housing  2501  having a body section or body  2502  with an open end  2502   a  closed by a removable access cover  2503 . Although alternatives are possible, analogously to the cover disclosed in previous descriptions relating to other embodiments, cover  2503  is secured in place on body  2502  by latches  2504 . Referring to  FIG. 40 , an end view of assembly  2500  taken toward cover  2053 , for the particular air cleaner  2500  depicted, three evenly radially spaced latches  2504  are used to secure cover  2503  in place, although alternatives are possible. As shown in  FIG. 39 , for the assembly depicted, each latch  2504 , when secured, extends through both the body  2502  and the cover  2503 , although alternatives are possible. 
     Cover  2503  is typically and preferably provided with a rotational indexing arrangement (such as a slot and key arrangement) similar to those described for previous embodiments. Referring to  FIG. 40 , one slot and key arrangement is depicted at  2504   a  comprising slot  2504   b  on cover  2504  and projection or key  2504   c  on body  2502 . 
     Referring to  FIG. 39 , cover  2503  preferably includes a precleaner arrangement similar to those previously described and comprising shield  2505 , secured on cover  2503  and projecting into interior  2502   b  of body  2502  from end  2502   a . Shield  2505  includes an air flow ramp arrangement  2506  thereon, configured to provide a cyclonic or circular motion around shield  2505 , to air passing into interior  2502   b  through air flow inlet  2510 . Typically, inlet  2510  would be configured as a tangential flow inlet. 
     Still referring to  FIG. 39 , air cleaner  2500  includes, secured therein, a primary filter element or cartridge  2520 . The primary filter cartridge  2520  comprises filter media  2521  secured in extension between opposite end caps  2522  and  2523 . End cap  2522  is a closed end cap. End cap  2523  is an open end cap. Thus, air flow which passes through media  2521  into interior  2525 , defined by filter cartridge  2520 , can eventually pass outwardly from region  2525  through axial clean air outlet  2528  of air cleaner body  2502 . 
     Although alternatives are possible, for the particular example shown, media  2521  is pleated media  2529 ; and, the cartridge  2520  has a conical shape. 
     In  FIG. 41 , cartridge  2520  is depicted in cross-sectional view. Referring to  FIG. 41 , the cartridge  2520  depicted includes a preform having an outer extension  2530  configured to extend between end cap  2522  and end cap  2523 . It is noted that the cartridge  2500  depicted in  FIG. 41  is inner liner free; i.e., it has no inner liner adjacent the media  2520 , in extension between end caps  2522  and  2523 . Inner support at this location, is provided by other structure discussed below. 
     Although alternatives are possible in some applications, for the particular cartridge  2520  depicted in  FIG. 41 , closed end cap  2522  comprises: (a) molded-in-place ring  2534 ; and, (b) preform section  2536 . The preform section  2536  comprises a portion integral with the outer structure  2530 , to form a single preform  2530   x . The preform section  2536  includes: central imperforate region  2536   a  and outer, perforate, ring region  2536   b . The outer ring region  2536   b  would generally be a grid or other perforate structure that allows flow (rise) of resin therethrough, during element construction. In this manner preform section  2536  is generally analogous to end  101  a framework  110 ,  FIG. 8 . 
     Also, unlike the preform  2100  of the embodiment of  FIG. 35 , preform  2536   x  extends completely between opposite end caps  2522  and  2523 . 
     Still referring to  FIG. 41 , preform section  2536  further includes flange  2536   c , at the closed end of the cartridge  2520 , positioned along an inside surface of the media  2520 . The media  2520 , then, becomes positioned between flange  2536   c  and outer support  2530 . 
     Spaced radially inwardly from flange  2536   c , is positioned central, end, imperforate region  2536   a . The central imperforate region  2536   a  includes projection  2536   d , which is spaced from flange  2536   c , inwardly, and projects into interior region  2525  of cartridge  2500 . The amount of projection is typically at least 5 mm, usually at least 10 mm and in some instances at least 15 mm. 
     Central imperforate region  2536   a  further includes end  2536   e  which includes central recess  2536   f  therein, defining a frusto-conical recess projecting in an axial direction (i.e., axially) away from end cap  2523 . Alternately stated, central imperforate region  2536   e  include frusto-conical projection  2536   g  thereon, which projects axially away from end cap  2523 . Of course an inside surface of projection  2536   g , defines frusto-conical recess  2536   f.    
     The central imperforate region  2536   e , and the frusto-conical recess  2536   f , are features similar to those discussed hereinabove in connection with  FIGS. 34 and 35 . However for the cartridge  2500  of  FIG. 41 , projection ring or flange  2536   d  begins at a location spaced from the media pack, not adjacent the media pack and, a central flange  2536  is positioned between the media pack and the projection  2536   d.    
     Referring to  FIG. 39 , in a central region, cover  2503  includes projection  2545  extending axially inwardly of cartridge  2520 , in particular into a bowl defined by central imperforate region  2536 , with a central portion including reverse axial frusto-conical projection  2536   g  received in a central frusto-conical recess  2545   a  of the cover  2503 . Preferably projection  2545  has a non-circular outer perimeter (for example pentagonal, hexagonal, heptagonal or octagonal), although alternatives are possible. In some instances, projection  2536   d  can be provided with a circular side definition, for receipt of the projection  2545  on cover  2503 , although again alternatives are possible. 
     Referring then to  FIG. 41A , preform  2530  includes: imperforate axial shield region  2530   a  and perforate support region  2530   b . Imperforate shield region  2530   a  preferably is positioned adjacent end cap  2523  and extends axially, along an outside of cartridge  2500  therefrom, around the media  2520 ,  FIG. 39 , a distance corresponding preferably to no more than 50% of the axial length of the cartridge  2500 , typically and preferably no more than 30% of that distance and often no more than 25% of that length. 
     The perforate region  2530   b  typically and preferably is at least 50% open, and extends over an axial distance of at least 50% of the axial length of the cartridge, and typically at least 60% (often at least 70%) of the axial length of the cartridge. 
     The particular outer preform support  2530  depicted, includes central projection  2531 , analogous to projection  1146 ,  FIG. 26 . 
     Referring to  FIG. 39 , for the particular air cleaner  2500  depicted, primary filter element or cartridge  2520  is generally conical (or frusto-conical) in shape, having the media  2521  defining a larger outer perimeter, diameter or dimension at end  2539  than at end  2538 . Thus a narrow end  2538  of the conical cartridge  2520  is projected into shield  2505 ,  FIG. 39 , during installation, to be surrounded thereby. 
     Shield  2505 ,  FIG. 39 , extends axially along cartridge  2520  at least 10% of the axial length of the cartridge  2520 , often at least 15% of this axial length typically at least 20% of this axial length and in many instances at least 25% of this axial length. 
     Referring to  FIG. 41A , end cap  2523  typically comprises a molded (typically polyurethane) end cap, sufficiently soft and compressible to form an outer, annular, radial seal at  2560 , for sealing within an annular surface  2561 ,  FIG. 39 , of housing body  2502 . The annular sealing surface at region  2560  and end cap  2523  can be provided with a tapered shape, for example a stepped shape as shown in  FIG. 41  to a narrow size near tip  2560   a , to facilitate sealing. A soft compressible urethane as previously characterized herein can be used for end cap  2523 , although alternatives are possible. 
     It is noted that in  FIG. 39 , overlap between region  2560  and housing step  2561  is shown, to depict the amount of compression that would be typical. 
     Although alternatives are possible, in the particular example shown, end cap  2523 , when installed, does not form a compressed axial seal with any portion of the housing  2501 , nor does it form an internal radial seal with any portion of the housing  2501 . 
     Referring to  FIGS. 39-42 , it is noted that cartridge  2500  does not contain any rotational engagement arrangement, for interaction with the housing. Rather secure positioning within the housing is provided by the compression of the seal in region  2560 , during installation. Thus, the cartridge  2500  can be said to be “rotational engagement arrangement free.” 
     The cartridge  2500 , which is a removable and replaceable service component, is secured within the housing  2501 , by cover  2503 . 
     Referring to  FIG. 39 , positioned in interior space  2525 , for the particular air cleaner  2500  depicted, is a secondary or safety filter  2580 . Referring to  FIGS. 43, 43A and 44 , the secondary or safety filter  2580  comprises media  2581  extending between opposite end structures  2582 ,  2583 . The media  2581  is supported within framework  2584 , in particular within rib structures  2584   a . Cartridge  2581  may be generally constructed in by positioning media  2581  in a mold, and injection molding the rib structures  2584   a ; along with a remainder of framework  2584 . 
     At end structure  2582 ,  FIG. 43 , is provided end cap  2582   a , which is a closed end cap. End cap  2582  preferably includes an axially outwardly projecting frusto-conical projection  2582   b  positioned to extend away from end cap  2583  and sized to be received within an interior projection  2536   f  on cartridge  2520 ,  FIG. 41 , during installation, see  FIG. 39 . This helps center the main element  2520  and provides support for the safety element  2580 . 
     In  FIG. 43 , safety cartridge  2580  is depicted in cross-sectional view. End  2583  comprises a seal arrangement  2594  positioned around an open aperture  2594   a  to define an inner radial seal, when installed, against flange  2585  in housing  2501 . The seal arrangement  2594  can, for example, be a molded-in-place seal arrangement comprising molded polyurethane, although alternatives are possible. 
     Referring to  FIG. 43 , it is noted that safety cartridge  2580  includes a framework  2586  comprising axial ribs  2584   a , and a radial flange  2586   a , with an axial support  2586   b , for supporting a seal formed by arrangement  2594 . 
     Referring to  FIG. 39 , framework  2584  provides downstream support or interior support for the media  2521  of cartridge  2520 . Referring to  FIG. 43A , safety cartridge  2580  is depicted with framework  2584  including radial hoops or supports  2584   b , to facilitate the support. 
     It is noted that in some applications, a safety cartridge may not be needed. In such instances, framework  2584  may be installed, without media, for example to support pleated media  2529  of cartridge  2520 , during use. 
     Referring again to  FIG. 39 , a dust drop tube is shown at  2595 . In operation, air would enter through inlet  2510 , which could, in some applications, be positioned at a different rotational location from where depicted. The dust would be directed into the cyclonic precleaner arrangement including ramp  2506 , to be directed in a cyclonic flow, similarly to descriptions with respect to previous figures. Again, the cover  2503  can be provided with a rotational indexing, to provide for proper orientation of the ramp  2506  relative to the inlet  2510 . The dust would in part be driven through region  2597 , toward dust drop tube  2595  for ejection. Air would be filtered by passage through filter  2520 . It would then pass through the safety cartridge  2580  if present, and outwardly through outlet tube  2528 . 
     Still referring to  FIG. 39 , main cartridge  2520  includes, adjacent end  2550 , a preformed shield construction  2600  comprising: (i) an axial extension  2530   b  of shield  2530   a , which in the arrangement shown generally has a circular cross-section and a conical shape; and, (ii) an outwardly (radially) projecting ring or flange  2602  which, in the example shown, is a circular ring. The ring or flange  2602  is generally positioned to stop dust from entering the region  2604  of the main cartridge  2520 , adjacent a region of body  2501 , where dust ejector  2595  is located. The flange usually extends outwardly at least 5 mm, typically at least 10 mm, for example 10 mm-20 mm from a remainder of the axial shield or extension  2601 . 
     The end cap materials for end cap  2523  and ring  2522  may, in many instances, comprise a soft, compressible, foamed polyurethane as previously mentioned and described herein. End cap preform  2536  (and a remainder of framework  2530 ) generally will be formed from a more rigid plastic such as polypropylene, nylon or a similar material. End cap  2582  of the safety element, would also be typically be formed from a more rigid plastic material such as a rigid polyurethane, polypropylene, nylon, or a similar material. Seal  2584  of the safety element (for support) would typically comprise a soft, compressible, foamed polyurethane as described. 
     Referring to  FIGS. 39 and 39A , it is noted that when the main filter cartridge  2520  and the safety filter cartridge  2580  (or support) are both installed, the main cartridge  2520  is positioned with portion of end cap  2523  axially overlapping a portion of the end cap  2583  of the safety element  2520 . In particular, referring to  FIG. 39A , radial projection  2586   a  of the safety element  2580 , projects sufficiently radially, so that when installed, it is positioned axially overlapped by a radially upper most portion of end cap  2523  (of the main element  2520 ). This overlap is for convenience, to allow both elements to be positioned within a confined and desirably defined space. The overlap is typically not utilized, for retention of the safety element  2580 . Typically, the safety element positioning and retentioning would be secured at the opposite end, involving projection  2582   b ,  FIG. 39 , of the safety element (or support)  2520  being received within recess  2536   f  of the main cartridge. (Again, the framework of the safety element  2580  can be used without media, as a support for the main cartridge  2520 .) 
     Attention is again directed to  FIG. 39A  which is an enlarged fragmentary view of a portion of  FIG. 39 . In  FIG. 39A , groove  2620  and end cap  2523  is shown. The groove  2620  extends inwardly from outer axial surface  2621  of end cap  2523 , toward media  2521 , of cartridge  2520 . The groove  2620  is an artifact, from a mold used to mold end cap  2523 . The groove  2620  generally extends inwardly from surface  2621 , an axial distance of at least 1.5 mm, typically 1.5-5.0 mm. As seen in  FIG. 45 , schematic end view of cartridge  2520  taken toward end  2523 , groove  2620  is preferably continuous and circular. 
     The groove  2620  is typically positioned inwardly, from outer surface  2560  of the radial seal region of the end cap, a distance of at least 1.5 mm, typically at least 3 mm and usually 5-10 mm. Although in some instances alternatives are possible, groove  2620  is typically either with inner most part  2620   i  axially aligned with end  2530   y  of support  2530 , or the inner most part  2620   i  of groove  2620  is radially off-set from such axial alignment by no more than 3 mm. (It is noted that surface  2523   x  is not at the same height as surface  2560 , usually it is about the same or within the range of 0.2-1.5 mm less, as shown.) 
     A molding process used to form groove  2620 , can be used to conveniently form the radial seal region  2560   b , between radial seal surface  2560  and support  2530   b . In particular liquid can be poured into a mold region corresponding to region  2560   b ,  FIG. 39A , and flash can be controlled, as the amount of resin is controlled by the size of a mold ring useable to form groove  2620 . Excess resin could then flow into a region of the mold corresponding to molded end cap portion  2622 ,  FIG. 39A , where excess material or flash is less of a concern. 
     In  FIGS. 46 and 47 , a side elevational view and perspective view of the preform  2530  are shown. 
     In selected ones of  FIGS. 39-47 , example dimensions are shown. Although alternatives are possible, the dimensions are indicative of a useable example. Example dimensions would be as follows: 
     AA=375-475 mm, for example 425 mm (16.73 inch); BB=19.9 mm (0.78 inch); CC=101.6 mm (4.0 inch); DD=165 mm (6.5 inch); EE=140 mm (5.51 inch); FF=50.8 mm (2.0 inch); GG=259 mm (10.2 inch); HH=98 mm (3.86 inch); II=227.3 mm (8.95 inch); JJ=109.0 mm (4.29 inch); KK=101.6 mm (4.0 inch); LL=300-400 mm, for example 358.9 mm (14.13 inch); MM=at least 1°, typically 1°-5° for example 1.8°; NN=130-190 mm, for example 161.5 mm (6.36 inch); OO=160-225 mm, for example 194.5 mm (7.66 inch); TT=210.9 mm (8.3 inch); UU and WW=366.3 mm (14.42 inch); VV=at least 1°, typically 1°-5° for example 1.8°; YY=95.9 mm (3.78 inch); ZZ=129.0 mm (5.08 inch); A1=25.0 mm (0.98 inch); A2=12.3 mm (0.48 inch); A3=7.3 mm (0.29 inch); A4=1.2 mm (0.05 inch); A5=12.0 mm (0.47 inch); A6=11.6 mm (0.46 inch); A7=0.4 mm (0.02 inch); A8=0.3 mm (0.01 inch); A9=7.1 mm (0.28 inch); A10=6.1 mm (0.24 inch); A11=1.2 mm (0.05 inch); A12=0.5 mm (0.02 inch); A13=7.8 mm (0.31 inch); and A14=13.3 mm (0.53 inch). 
     Although alternatives are possible, it should be noted that these example dimensions indicate the present features are adapted for application, if desired, in air cleaners of an intermediate size between the largest of the large air cleaner examples of  FIGS. 34-38 , and the smallest examples corresponding to the features of  FIGS. 1-33 .