Abstract:
Method for producing a firm, motion-resistant connection between mating surfaces of a male member, such as a shaft or hub, and a female member such as a bore. One or more thin ribs of pressure-deformable composition, such as integral soft metal or plastic, are formed on one of the mating surfaces, which ribs deform and spread between the surfaces when the male member is forced into the bore to connect the members. According to a preferred embodiment, the shaft is the fixed core shaft of a xerographic toner developer roller within a toner cartridge and/or the hub of a bearing support member for the shaft, and the bore is a central core shaft-engaging bore in the hub and/or a hub-engaging bore in the cartridge housing, and the connection is an electroconducting connection providing near-zero capacitance.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to providing a firm interlock between a journal end, such as of a core or hub or shaft, and the bore on an element to be fixed to the journal end in a manner which prevents relative rotation therebetween. Known systems include the use of one or more mating flats ribs or other features on the outer surface of the journal end and on the inner surface of the bore, which prevent relative rotation and provide positive alignment. However such known systems are unsatisfactory for use in some precision apparatus systems which require a firm interlock between a journal end such as a shaft having a flat and an element having a bore having a flat which mates with the flat on the shaft, where any degree of “sloppiness” or relative movement is detrimental to the operation of the apparatus, resulting in extensive failures. 
     Reference is made to our U.S. Pat. No. 5,822,654, the entire disclosure of which is hereby incorporated herein by reference thereto. U.S. Pat. No. 5,822,654 discloses an electrostatographic reproduction machine which incorporates a customer-replaceable developer unit (CRU) or developer cartridge. Said unit has a fixed housing, an opposed pair of bearing support elements and a developer roll sleeve which is supported by the bearing support elements for rotation about a non-rotating central core member containing magnetic poles which are angularly positioned to provide an optimum magnetic field array for the proper development of toner images formed on the developer roll. The bearing support elements each have an end sleeve portion having an outer surface provided with a flat for mating with a flat in a receiving bore on the housing, and also having an inner bore surface having a flat for mating with a flat on the journal end of the central magnet core of the developer roll. The bearing support elements rotatably support the developer roll sleeve while the central core is fixed to the bearing support elements which are fixed to the housing. An electrical bias must be applied to the outer surface of the rotating developer sleeve to provide for proper development and control of the charged surface, and therefore the bearing support elements are electrically conductive and in contact with a power source through their connection with the housing/with near zero capacitance. 
     The central core of the fixed magnetic developer roll contains a plurality of spaced and aligned magnets having developer transport poles and trim poles which are angularly positioned to impart optimum magnetic field properties to the rotating developer roll sleeve, spaced therefrom for the proper development of the marking particles formed on the developer sleeve for transfer to the charged areas of the photoreceptor roll. Any relative movement between the fixed location or position of the magnet-containing core and the housing of the developer cartridge will change the location of the magnetic field imparted or induced to the surface of the developer sleeve and will result in improper development of the marking particles, which contain magnetic carrier particles and fusible toner particles, and external damage to the apparatus. It has been found that the use of mating flats on the central core shaft and the inner bore of the bearing support member, and mating flats on the outer hub of the bearing support member and on the supporting bore of the housing do not provide complete resistance to relative movement of either the central core or the bearing support element, i.e., they provide “sloppy” connections which reduce the quality of the electrostatic copies by producing prints which are light and non-uniform. 
     Firm motion-resistant connections between shafts and hub bores having rotation-resisting mating flats is also desirable in numerous devices, particularly scientific measurement or indexing devices, where even the slightest degree of “sloppiness” resulting in the slightest degree of “give” or relative movement can be detrimental to the accurate operation of the device. It is known to provide a hub with a radial locking screw, through its flat, which engages the mating flat on the shaft in order to tighten the connection therebetween but this is not always completely effective, nor is it possible with all assemblies such as that of U.S. Pat. No. 5,822,654. 
     SUMMARY OF THE INVENTION 
     The present invention relates to providing a firm, motion-resistant interlock between a mating journal end or shaft and a bore, each having one or more flats which mate with a corresponding number of flats on the other to prevent relative rotation therebetween. The invention is characterized by forming on the inner surface of the bore or on the outer surface of the journal end or shaft a plurality of axial “crush ribs” or thin, spaced elevations of relatively soft metal or plastic composition, which ribs are crushable or spreadable over their supporting surface under the pressure applied when the shaft is forced into the bore. The soft metal or plastic which is displaced from the crushed ribs spreads in all directions to fill any airspace between the shaft and the bore as the shaft is seated within the bore, to form a firm interlock which resists any degree of relative rotation or “sloppiness” between the parts, while any excess displaced material is ejected. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an end of a magnetic roll assembly and a bearing support member or end cap, with the latter shown in spaced and inverted position for purposes of illustration; 
     FIG. 2 is a perspective view of an end of a cartridge housing and a bearing support member or end cap, with the latter shown outside the housing for purposes of illustration. 
     FIG. 3 is a partial perspective view of a developer cartridge, developer roll and bearing support incorporating crush ribs according to the present invention, and 
     FIG. 4 is a cross sectional view of FIG. 3 along the line  4 — 4  thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the bearing or cap element  10  and the journal or shaft element  22  of the magnetic roll assembly  20  are provided with single mating flats  11  and  21 , respectively, which serve as locating members and fix the orientation of elements  10  and  20  relative to each other. This is critically important for certain assemblies such as the bearing supports and developer roll core shafts of U.S. Pat. No. 5,822,654, the disclosure of which is incorporated herein. 
     The inner central hub of the bearing element  10  has a bore surface  12  containing the location flat  11  and a plurality of spaced crush ribs  13  of relatively soft, spreadable metal or plastic composition which preferably is integral with the material of which the hub element is formed. For ease of manufacture, the ribs  13  are axial in direction and are formed when the bore surface  12  is molded or otherwise formed on the hub. However if the hub element  10  is formed by molding, the ribs  13  may be slightly spiral along the bore surface  12  so that they spread uniformly over the surface of the bore as they are pressure-crushed. Also the ribs  13 , if molded, preferably are gradually tapered from adjacent the inlet end of the bore surface  12 , or inwardly therefrom, for ease of insertion or introduction of the leading end of the shaft  20 . It should be understood that, while the crush ribs  13  generally are located on the inner surface  12  of the bore since a shaft  20  is commonly formed of a hard steel alloy for strength purposes, the crush ribs can be present on the outer surface of the shaft  20  rather than on the bore surface if the hub and shaft are formed of the same material, or where the hub element is formed of harder, less crushable or deformable material. Since the hub bore  12  and the shaft  20 , are usually machined and cut or molded to the closest possible tolerances, the dimensions of the crush ribs  13 , and their number, are usually as small as possible, while producing the desired result of spreading between the mating surfaces to fill any airspace between the assembled hub and shaft and produce a tight connection which prevents any slight relative movement therebetween. Thus, the crush ribs  13  generally are very thin, with a maximum height which varies between about 0.0001 and 0.001 inch, depending upon the mating diameters of the bore  12  and the shaft  20 . The thickness or width of the ribs  13  is less critical since they spread over surfaces of the bore and the shaft. 
     A critical use of the present crush ribs is in connection with the support of a magnetic developer roll within a user-replaceable toner cartridge of an electrostatic reproduction machine, where the magnetic developer roll comprises a non-rotatable magnetic core and a rotatable developer sleeve, as disclosed in U.S. Pat. No. 5,822,654 and illustrated by FIGS. 3 and 4 of the present application. 
     As illustrated by FIG. 2, the bearing element  10  also has an outer male cap member  14  having a surface  15  containing a location flat  16  and a plurality of spaced crush ribs  17  of relatively soft, spreadable metal or plastic composition which preferably is integral with the material of which the bearing element  10  is formed. 
     As shown by FIG. 4, the bearing element  10  of FIG. 1 is inverted and the inner central hub bore surface  12  is forced over the shaft  22  to mate the flats  11  and  21  and spread the crush ribs  13  to produce a magnetic roll assembly having a firm, motion-resistant connection between the magnetic roll member  20  and the bearing support element  10 . 
     Next, the assembly is inserted within the cartridge housing  30  having a bore  31  with a surface  32  having a locating flat  33  designed to mate with the flat  16  on the surface  15  of the outer male cap member  14  of the bearing element when the cap member  14  is forced into the housing bore  31 . This causes the crush ribs  17  to spread between the surfaces  15  and  32  to form a tight, movement-resistant connection between the magnetic roll assembly and the housing  30  of the cartridge. 
     For clarity and ease of discussion, present FIGS. 3 and 4 use the same reference numbers for the same elements shown in corresponding FIGS. 8 and 9 of U.S. Pat. No. 5,822,650, the disclosure of which is incorporated herein by reference. 
     Referring to present FIGS. 3 and 4, the developer subassembly  78  of the customer-replaceable toner cartridge unit (CRU) comprises a housing  174 , a developer roll  92  having a stationary magnetic core  312  and a rotatable developer sleeve  314  both supported by a bearing support member  300  which is non-rotatably attached to the cartridge housing  174  and which non-rotatably supports the magnetic core  312 . The core  312  contains magnet assemblies  316  having pickup poles which are aligned to cause the developer sleeve  314  to attract toner and carrier beads thereto, transport poles which are aligned to maintain the carrier beads adhered to the roll sleeve  314 , and trim poles which are aligned to cause a trim blade to trim and regulate the amount of developer passing to the development zone. The precise locations of the magnetic assemblies  316  on the stationary core  312 , relative to the developer sleeve  314  control the magnetic fields at the surface of the sleeve and the attraction, trim, and transfer of the developer composition, which determine the quality of the developed images which are transferred to a copy sheet and fused. 
     Therefore it is important to the quality of copies produced by means of the CRU cartridges of U.S. Pat. No. 5,822,654 that there is no relative movement, or sloppiness, between the stationary developer core  312  and the bearing support member  300 , as shown by FIG. 1, or between the latter and the cartridge housing  174  as shown by FIG.  2 . To this end, the present invention involves providing the bearing support member  300  with a plurality of spaced crush ribs  341  extending axially along the bore  340  of the bearing support member  300  which engages the mating end  317  of the developer core  312 . Core end  317  also includes a flat  344  which mates with a flat  346  within the bore  340  which prevents relative rotation therebetween. The forcing of the bearing support member bore  340  over the end  317  of the core shaft, during initial assembly of the parts, deforms, crushes and spreads the crush ribs  341  within the bore  340  to form a tight, motion-resistant connection between the developer core  312  and the bearing support member  300 . The connection between the bearing support member  300  and the cartridge housing  174  is similarly tightened by providing a spaced plurality of crush ribs  351  on the outer hub surface  350  the bearing support member  300  which is engaged within a bore  175  in the housing  174 . The outer surface  350  of the bearing support member  300  also includes a flat  356  which mates with a corresponding flat  360  in the housing bore  175  to fix the bearing support member  300  to the cartridge housing  174 . When the bearing support member  300 , and attached developer core  312 , is forced into the housing bore  175  the crush ribs  351  on the outer hub surface  350  of the bearing support  300  are crushed, flattened and spread into the housing bore  175  to form a tight motion-resistant connection therebetween along both axial and angular axes. 
     The development roll  92 , as shown in FIG. 4 includes a fixedly mounted core  312  and a sleeve  314  which is rotatably mounted around core  312  and a sleeve  314  which is rotatably mounted around core  312 . The core  312  may be made of any suitable durable material which is magnetically conductive, for example, a metal or a magnetically conductive plastic. The core  312  includes magnetic poles  316  which are angularly positioned with respect to roll centerline  320 . The poles  316  are so angularly positioned to provide an optimum magnetic field for the proper development of the marking particles. 
     The sleeve  314  is spaced from and rotatably mounted with respect to core  312 . The sleeve  314  is made of preferably a magnetically non-conductive and an electrically conductive material. For example, the sleeve  314  may be made of aluminum. The development roll  92  also preferably includes an end cap  322  which is fixedly secured to sleeve  314  and rotates therewith. The sleeve end cap  322  may be made of any suitable durable electrically conductive material. For example, the end cap  322  may be made of conductive plastic. 
     To provide proper spacing between the developer roll  92  and the photoconductive surface of the photoreceptor (not shown), the developer roll  92  preferably further includes a development roll sleeve or (DSR) sleeve  324 . The DSR sleeve  324  has a thickness which sets the gap between the developer roll  92  and the photoconductive surface. The DSR sleeve  324  is fixedly secured to the sleeve  314  and rotates therewith. Thus, the DSR sleeve  324  is in rolling contact with the photoconductor surface of the photoconductive drum. 
     The conductive bearing support  300  includes a first feature  326  which cooperates with the development roll  92 . The first feature  326  may be in any form capable of providing support to the development roll  92 . For example, the first feature  326  may be in the form of a journal or a bore cooperating with a mating feature on the development roll  92 . 
     While the development roll may be in the form of a single rotating component, preferably, as shown in FIG. 3 the development roll includes the stationary core  312  as well as the rotating sleeve  314 . The first feature  326  provides for the rotation of the sleeve end cap  322  which is a part of the development roll  92 . The sleeve end cap  322  rotates relative to the conductive bearing support  300 . 
     As shown in FIG. 4, the sleeve end cap  322  includes an inner hub  330  which mates with middle bore  332  of conductive bearing support  300 . Further, as shown in FIG. 4, the sleeve end cap  322  may include a lager hub  334  which matingly fits with large bore  336  of conductive bearing support  300 . 
     The core  312  is positioned fixedly to housing  174  by small bore  340  of the support  300  which matingly fits with journal diameter  342  of the core  312 . Preferably, to angularly orient the poles  316  in the core  312  of the development roll  92 , the journal  342  of the core  312  of the development roll  92  includes a flat  344  which mates with flat  346  within bore  340  of the support bearing  300 . 
     According to the present invention, a firm motion-resistant interlock is provided between the magnetic core  312  and the inner central bore  340  of the support bearing  300  by providing the inner surface of the bore  340  with a spaced plurality of axial crush ribs  341 , such as thin raised plastic ribs which are integral with the plastic support bearing  300  and are formed when the bore  340  is formed in the bearing  300 . The ribs  341  are crushed and spread when the journal end of the core shaft  312  is forced into the bore  340 , resulting in a tight, motion-resistant interlock therebetween. 
     The conductive bearing support  300  also is fixedly secured to the development housing  174 . For example, as shown in FIG. 4, the bearing support  300  includes small OD  350 , medium OD  352 , and large OD  354  which mate with corresponding bores in the housing  174 . It should be appreciated that the middle OD  352 , and large OD  354  may be either in clearance or matingly fitted to the respective bore of the housing. 
     Referring again to FIG. 3 to angularly orient the conductive bearing support  300  with respect to the housing  174 , preferably, the bearing support  300  includes a locating feature in the form of a flat  356  formed from small OD  350 . Correspondingly the bore in housing  174  includes a flat  360  which mates with flat  356  of the conductive bearing support  300 . The flat  360  on the bore of housing  174 , the flat  356  on the exterior of the support  300 , the flat  344  on the interior bore of the support  300 , and the flat  332  on core  312  cooperate to angularly orient the poles of the core  312 . 
     As between the core shaft  312  and the bearing support  300 , another tight motion-resistant interlock is provided between the bearing support  300  and the cartridge housing  174 , according to the present invention, by forming a spaced plurality of raised axial crush ribs  351  on the OD surface  350  of the central outer hub  372  of the bearing support  300 , which ribs are crushed and spread when the central hub of support  300  is forced into the housing bore  174 . Ribs  351  preferably are plastic ribs integral with the support  300 . 
     Referring again to FIG. 4, preferably, the bearing support  300  further includes an outer end face  370  which contacts and restrains the development roll spacing sleeve  324  between the sleeve  314  of the development roll  92  and the housing  300 . 
     The conductive bearing support  300  further serves an important function by providing an electrical path from the power supply to the electrically conductive sleeve  314  of the roll  92 . As shown in FIG. 4, the conductive bearing support  300  is in contact at large bore  336  and middle bore  332  with sleeve endcap  322 . The sleeve endcap  322  is in electrical contact with the sleeve  314 . The sleeve endcap  322  thus provides an electrical connection between the conductive bearing support  300  and the sleeve  314 . 
     The conductive support  300  is made of any suitable durable material which is electrically conductive. The support thus can be made of a durable metal or, as shown in FIG. 4, be made of an electrically conductive plastic. For example, the support  300  may be made of a polycarbonate with carbon fibers or other conductive fiber. 
     The support  300  includes a feature  372  which extend outwardly from the development housing  174  and serves to provide an electrical path from the power source (not shown) to the development roll  92 . For example, as shown in FIG. 4, the conductive bearing support  300  includes the central hub  372 . The central hub  372  includes an outer face  374  which provides for the electrical contact for the development roll  92 . The outer face  374  may be contacted with the power supply in any suitable fashion. 
     It should be understood that the above description is merely illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from this invention.