Patent Publication Number: US-6212342-B1

Title: Weighted noise reducing device for photosensitive drum of an image forming apparatus

Description:
TECHNICAL FIELD 
     The invention relates to an image forming apparatus, and particularly to photosensitive drums in which an insert is provided for reducing noise and/or vibration. 
     BACKGROUND OF THE INVENTION 
     Discussion of Background 
     Image forming apparatuses, such as printers or photocopiers, include a photosensitive member, typically in the form of a photosensitive drum. The performance of the photosensitive drum is of critical importance, since the image being produced (or reproduced) is formed and developed on the drum surface. The developed image is then transferred from the drum to, for example, a sheet of paper. Typically, the drum is formed of metal, such as aluminum, and the metal is anodized or coated with a thin dielectric layer. Normally, the drum is then coated with photogeneration and photoconduction layers over the dielectric layer. 
     In forming an image, the drum is rotated, and a given location on the outer surface of the drum is thereby rotated past a charging device, an exposure location, a developing location (at which toner is applied), a transfer location (at which the toner image is transferred from the drum to paper), and a cleaning location at which a cleaning blade removes excess toner from the drum so that the process can be repeated. During an image forming operation, as a result of the rotation of the photosensitive drum and its interaction with the various other components of the image forming apparatus, noise and vibration can occur. This is particularly true since the photosensitive drum is a thin-walled metal drum, and thus has a characteristic harmonic sound spectrum which is easily driven by any mechanical resonance. 
     For example, vibration (and associated noise) can occur from the rotation of the drum, and any imperfections of the drum, the gear flanges attached to the drum, and/or the drive which interacts with the gear flanges of the drum. Further, an alternating current (AC) electric field is applied to the charge roller, and the alternating current can also cause noise and/or vibration of the drum or between the drum and other components. In addition, as the drum rotates past the cleaning blade (which is in contact with the drum), noise is often generated, particularly if the drum surface is roughened by use. This interaction between the drum and cleaning blade is also known as chatter vibration or “stick-slip” vibration. (See, e.g., Chatter Vibration of a Cleaner Blade in Electrophotography, by Kawamoto, in the January/February 1996 issue of Journal of Imaging Science and Technology.) The noise and vibration associated with operation of a photoconductive drum not only presents an annoyance to workers using (or in the vicinity of) the image forming apparatus, but also, the noise/vibration can lead to image deterioration or damage to the apparatus. In particular, the vibration can result in poor performance or interaction between the photosensitive drum and one or more of the components with which the drum interacts, including the cleaning blade, the charge roller, the developer device, etc. 
     Vibration may also cause image blurring especially with the current trend to higher resolution devices (evolution from 300 to greater than 1200 dots per inch). For example, if the cleaning blade does not properly remove residual toner, undesirable resolution of character images can occur in subsequent images. Further, if the drum is not charged or developed properly, the resulting image can have white spaces where the image has not been properly formed, developed or transferred, or black spots where undesired toner has been transferred to the sheet of paper. Noise problems can also occur as a result of the generation of gases (ozone) which occurs during an image forming operation, however this noise is typically relatively small. 
     To eliminate noise and/or vibration, the physical characteristics of the drum can be modified, for example, by increasing the thickness of the drum. Thus, the drum can be designed so that its natural frequency differs from that of other components of the apparatus and/or that of the process cartridge (the unit within which the drum is disposed). As a result, the vibrations are eliminated or reduced, or the frequency of the noise which might occur can be shifted so that it is outside of the audible range. However, increasing the thickness of the drum can make the drum more expensive to manufacture, particularly if the tooling utilized to manufacture a drum must be replaced. Moreover, when photosensitive drums are manufactured as replacement parts, they will often be inserted into process cartridges of another manufacturer. The process cartridge could be refurbished or a newly manufactured replacement process cartridge of a different manufacturer than that of the photosensitive drum, and the manufacturer/refurbisher of the process cartridge could change (or the design of a given manufacturer/refurbisher could change). Thus, it can be difficult to simply select a thickness of the drum which will be suitable for avoiding noise problems, since even if a thickness is selected for a certain process cartridge, that thickness could be unsuitable for another process cartridge. As a result, noise problems can be particularly problematic with photosensitive drums manufactured as replacement parts. 
     A further difficultly which can arise with photosensitive drums is that the roundness or circularity of the drum can vary over time, which can also lead to image deterioration. The roundness or circularity of the drum can more rapidly deteriorate if the drum is vibrating and contacting other components disposed about the drum. This problem can also be reduced by providing a thicker drum, however as discussed above, increasing the thickness of the drum can increase the cost, from a materials standpoint and/or the requirement for new tooling. 
     An alternate solution which has been utilized in the past for solving noise and/or vibration problems has been to insert plugs within the photosensitive drum. U.S. Pat. No. 5,488,459 to Tsuda et al. discloses an example of such an approach. With this solution, a disk or cylindrical object is inserted into the drum, and the insert provides additional weighting to the drum to alter the mass/frequency characteristics of the drum. However, the use of plug-type inserts is undesirable for a number of reasons. First, the plug is often required to be positioned at a precise location within the drum, which can complicate the manufacturing process. Further, the plug must be secured in place, which can require the use of an adhesive, thus further complicating the manufacture/assembly process. Further, the plug must be precisely manufactured. If it is too large, it could cause deformation of the drum, or require a high insertion force, which complicates the assembly process. 
     For example, it is ideal to use expanding chucks to hold a photoconductive drum by its inner surface during certain manufacturing processes, since damage to the outer surface of the drum is prevented. However, expanding chucks have limited holding ability. Therefore, if a high insertion force is required to insert a plug into a photoconductive drum, it may not be possible to use an expanding chuck to hold the drum during insertion without distorting the shape of the drum. On the other hand, if the plug is too small, it can be difficult to position the plug within the drum and secure the plug in place. Thus, the use of a plug or weight which is inserted inside of the drum has been less than optimal. 
     Another problem that has arisen with respect to inserts that are bonded to the inside of a photoconductive drum, is that in recycling such equipment, dissimilar materials must be separated from each other. For example, photoconductive drums are typically made from aluminum, while inserts are typically made of rubbers, plastics or foams, etc. Therefore, in order to recycle the drum, the drum must be separated from the insert. If, however, the insert has been bonded to the inside of the photoconductive drum with an adhesive, extreme measures must be taken to remove the insert from the drum. 
     Similar problems arise with respect to the mounting of end pieces to a photosensitive drum, such as gears and/or flanges. For example, if a gear is attached to the end of a photosensitive drum, to provide an interface with a toothed gear of a motor, and thereby transmit rotational forces to the drum, the gear must be anchored with sufficient strength to withstand such rotational forces over its useful life span. It has been well-known to use adhesives, or to cut an end of the drum to provide a keyway, or other mechanical interlacing techiniques to attach a gear to a drum. However, the use of adhesives causes problems discussed above with respect to drum inserts. Furthermore, specialized machining of the drum ends may require special tooling. 
     In view of the foregoing, a device and method are needed for reducing noise and/or vibration in image forming apparatus, particularly noise and/or vibration associated with operation of a photosensitive drum. Such a device and method are preferably suitable for use in both original equipment and for replacement parts. 
     SUMMARY OF THF INVENTION 
     It is an object of the present invention to provide a device and method for reducing noise and/or vibration in an image forming apparatus. 
     It is another object of the invention to provide a device and method for eliminating or reducing noise or vibration which can occur during operation of a photosensitive drum in original equipment of an image forming apparatus, or during operation of replaced or refurbished parts of an image forming apparatus. 
     It is a further object of the invention to provide a device and method which will provide for more reliable and consistent performance of a photosensitive drum in an image forming apparatus. 
     It is a further object of the invention to provide an insert device for a photosensitive drum which can be easily installed inside of a photosensitive drum, without requiring the insert to be bonded within the drum. 
     It is yet another object of the invention to provide a drum with an insert and an end piece such as a gear and/or flange which does not require adhesive or special machining of the drum to anchor the end pieces or the insert to the drum. 
     Another object of the invention is to provide an insert for a photoconductive drum which can be inserted and removed without damaging the photoconductive drum. 
     The above and other objects and advantages are achieved in accordance with the present invention by providing a noise prevention device inserted into a photosensitive drum and which is constructed of an elastic member having, in a relaxed state, an outer diameter which is larger than an inner diameter of the inner surface of the photosensitive drum. According to the invention, the insert is configured such that when the elastic member is elongated in a longitudinal direction, the outer diameter of the elastic member may be elastically reduced to a diameter equal to or less than the inner diameter of the photosensitive drum. Therefore, the insert may be installed to the interior of a photosensitive drum by elongating the insert then releasing the insert so that it expands in to contact with the inner surface of the drum such that a pressure contact between the insert and the drum increases, since the outer diameter of the insert, in a relaxed state, is larger than the inner diameter of the drum. The inner diameter, outer diameter and material used for constructing the insert are chosen such that, in a relaxed state, and after being inserted into the photoconductive drum, the insert provides sufficient force or pressure contact against the inner surface of the drum such that the insert is anchored to the inside of the drum. Therefore, the complications associated with using adhesive to bond an insert to the interior of a photosensitive drum are avoided and recycling of the drum is simplified since the insert may be removed relatively easily. Furthermore, since the insert can be inserted with little or no insertion force, the drum is rendered more durable and less susceptible to deformation or deviation in roundness about the circumference of the drum. 
     In a presently preferred form of the invention, the insert is made from an elastomeric material and is structured such that when it is elongated in a longitudinal direction, the outer diameter can be reduced within the elastic range of deformation of the insert such that the outer diameter of the insert can be made smaller than the inner diameter of the drum. Furthermore, the outer diameter of the insert in a relaxed state, is such that a frictional force between the outer surface of the insert and the inner surface of the drum, maintains the radially outward force necessary for anchoring the insert within the photosensitive member. The present invention therefore avoids the need for adhesive and provides an insert that is relatively simple to insert into and remove from a photosensitive member, with little or no insertion force. 
     Preferably, the elastic member is in the form of a corrugated sleeve, where the outer diameter of the sleeve is larger than the inner diameter of the photosensitive drum. By constructing the insert as such, upon elongation, the folds forming the corrugated sleeve are easily flattened, thereby allowing the outer diameter of the sleeve to be easily reduced, which simplifies insertion and reduces forces necessary for insertion. Additionally, the corrugated sleeve may include at least one closed end. By providing the sleeve with at least one closed end, the insert can be elongated by inserting a tool into an end of the insert opposite the closed end, then pressing the tool against the closed end, so as to elongate the insert. Since the insert is configured such that the outer diameter of the insert can be elastically reduced to be smaller than the inner diameter of the drum, at least a portion of the elastic member can be elongated such that the inner diameter of the elastic member is constricted, thereby allowing the elastic member to be inserted into the drum with little or no insertion force. Once the pressure from the tool is released, the outer surface of the elastic member is pushed against the inner surface of the drum, thereby anchoring the insert within the drum. Similarly, in order to remove the insert, the tool can be inserted into the same position as during insertion, and pushed until the insert is completely removed from the drum. Therefore, insertion and removal can be performed by inserting a tool into the same end of the drum, thereby simplifying insertion and removal procedures. 
     According to a further aspect of the present invention, a method for inserting an elastic insert into a photosensitive drum includes the steps of elastically elongating an insert which has an outer diameter that is greater than an inner diameter of a photosensitive drum, such that an outer diameter of the insert is contracted to a diameter that is less than an inner diameter of the photosensitive drum. The insert is then inserted into the drum and released so as to allow the insert to return to a relaxed state, and thereby increase a contact pressure between the insert and the inner surface of the drum. 
     According to another aspect of the present invention, a tool includes first and second engaging devices which are commonly connected to a controlling device. The controlling device is configured to move the first and second engaging devices relative to each other. In a presently preferred embodiment, the engaging devices are configured to engage first and second ends of an inner surface of an elastic insert for a photoconductive member, and the controlling device is configured to move the first and second engaging devices relative to each other along a first direction, so that the elastic insert can be stretched. With such a tool, an elastic insert, such as the inserts described with respect to the above aspects and embodiments of the present invention, can be inserted into a photoconductive member, such as a photoconductive drum. Preferably, the controlling device is configured to move the first and second engaging devices with sufficient force so as to elongate an elastic insert such that an outer diameter of the insert is reduced to a diameter less than the inner diameter of the drum. 
     The arrangement of the present invention is advantageous in a number of respects. First, since the outer surface of the insert is in contact with the inner surface of the photosensitive drum, the insert can vary the mass/frequency characteristics of the drum, to thereby ensure that the resonance frequency of the drum is outside of the audible range, or does not match the resonance frequency of other components of the apparatus. Further, since the elastic member of the noise prevention device can be elongated so as to have a diameter less than that of the inner surface of the drum, the noise prevention device can be inserted with little or no insertion force, thereby preventing damage during the assembly of the drum with the noise prevention device. A further advantage is that the drum and insert material can be easily recycled, since it is not necessary to use an adhesive to bond the insert with the interior of the drum. 
     Additionally, during transportation of photosensitive drums from a manufacturer to a downstream user, assembled photosensitive drums may be exposed to temperatures between −20° C. and 40° C. or even temperatures as extreme as −40° C. to 80° C. The exposure of drums to such thermal cycling has caused photosensitive drum inserts to become dislodged from the inner surface of the drum, thereby changing the characteristics of noise suppression in the image forming apparatus during use. For example, such thermal cycling has caused an insert to drop completely out of a photosensitive drum if the end of the drum is not closed with a gear for example. If the drum includes a gear or flange attached to the end thereof, the insert may move within the drum thereby changing the noise dampening effect of the insert. Additionally, the movement of the insert may damage the gear and/or flanges provided at the ends of the drum. Although adhesives have been used in the past to ensure the positioning of an insert within a drum, differences in the coefficients of thermal expansion between the adhesives, the insert, and the drum have caused adhesives to rupture during cyclic thermal encountered during transportation of drums. Therefore, by removing the need for adhesives to maintain the position of the insert within a photoconductive drum, the present invention is not affected by problems caused by adhesive that has been ruptured by thermal cycling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent as the same becomes better understood with reference to the following detailed description, particularly when considered in conjunction with the drawings in which: 
     FIG. 1 schematically represents a photocopier to which the present invention is applicable. 
     FIG. 2 schematically represents a printer to which the present invention is applicable. 
     FIG. 3 includes a side and an end view of an insert according to the present invention. 
     FIG. 4 is a side and an end view of a photoconductive drum of the present invention. 
     FIGS. 5 and 6 are side views of an insert according to the present invention positioned within a photoconductive drum. 
     FIG. 7 is an alternative embodiment of an insert according to the present invention. 
     FIG. 8 is a sectional view of a further preferred embodiment of an insert according to the present invention. 
     FIG. 9 is a sectional view of the insert shown in FIG. 8, during insertion into a photosensitive drum. 
     FIG. 10 is a sectional view of a further embodiment of the insert shown in FIG.  8 . 
     FIGS. 11 and 12 illustrate a method for inserting an insert into a photoconductive drum according to a further aspect of the present invention. 
     FIG. 13 is an enlarged side view of one end of an insert according to the present invention. 
     FIGS. 14 and 15 illustrate a method of inserting an insert into a photoconductive drum according to a further embodiment of the present invention. 
     FIGS. 16 and 17 show a method for inserting an insert into a photoconductive drum according to a further embodiment of the present invention. 
     FIG. 18 is a side view of a further embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 schematically represents an image forming apparatus in the form of a photocopier to which the present invention is applicable. In such an arrangement, an original document is placed upon the photocopier glass  10 , and is illuminated by a lamp  12 . The resulting light is then projected onto a photosensitive drum  1  by way of an optical system  14 , and the drum has been previously charged utilizing a charge roller  16 . As a result, an electrostatic latent image is formed on the drum  1 , and a developing unit  18  then supplies toner to the drum  1  to develop the electrostatic latent image. Paper is fed from a source  20  by various rollers to a location between the drum  1  and a backup roller  22 , so that the toner image of the drum is transferred to the paper. The paper is then fed to a fixing device  24  which, typically utilizing heat, fixes the toner image to the paper and the paper is then conveyed out of the apparatus. A cleaning blade  17  is provided downstream from the backup roller  22  (i.e., downstream with respect to the direction of rotation of the drum  1 ), so that any residual toner remaining on the drum after the image is transferred to the paper is removed by the cleaning blade  17 . The toner removed by the blade then falls into a container (not shown) provided for collecting residual toner. The drum is then provided with an initial charge by the charge roller  16 , and the process is repeated for the next image. 
     FIG. 2 schematically represents a printer device to which the present invention is also applicable. As shown in FIG. 2, in contrast with the photocopier device, the printer provides an image by way of a control unit which provides a video signal, for example, by a laser scanning unit  30 . The laser scanning unit  30  thus provides a latent image onto the photosensitive drum  32 , which has been uniformly charged with a charge roller  34 . The image is developed by a developing device  36 , and is transferred to paper, which is fed from a source  38 , as the paper passes between the photosensitive drum  32  and a backup roller  40 . The paper then travels past a fixing device  42  and out of the printer by various conveying rollers and guides. Residual toner can be removed by a cleaning blade  37 . 
     As should be apparent from the foregoing, the photosensitive drum is critical to the image forming process, and for each cycle of operation, the photosensitive drum is required to cooperate and interact with a number of components, including the charge roller, the optical image forming system, the developer device, the backup roller and the cleaning blade. As the drum rotates, it can also vibrate as a result of the drive utilized in rotating the drum, imperfections in the drum and/or the gear flanges of the drum, etc. Further, where an AC current is applied to the charge roller  16 ,  34 , the alternating charge can also have a tendency to cause vibration and/or noise during operation of the drum, as can the frictional contact of the drum with the various components including the cleaning blade, charge roller and developing device. The operation of a charge roller has also been found to generate ozone gas by localized electric discharge (known as the Paschen discharge effect), and this discharge is also believed to be a potential cause for noise and/or vibration of the drum. 
     The generation of noise and/or vibration is often accompanied by a deterioration in the image quality, since the drum is not smoothly and consistently interacting with the other components of the image forming apparatus. As a result, toner may appear in areas in which it is not desired (undesirable black spots), and/or toner will not appear in areas required for forming the image (undesirable white spots). Less than optimal images can also occur over a period of use as the circularity of the drum diminishes. In particular, after the drum has operated for a number of cycles, certain locations of the drum can become deformed so that the cylindrical shape of the drum becomes more imperfect. This loss of circularity also contributes to degradation of the image quality, and the loss of circularity can occur more rapidly if the drum vibrates, since the drum can be exposed to more concentrated forces or forces of a larger magnitude than would be the case if the drum were smoothly rotated. Of course, the generation of undesirable noise and vibration can also be an annoyance to the operator of the apparatus, or those in the vicinity of the apparatus. 
     In order to avoid or reduce noise, some equipment manufacturers have designed the drum so that the natural resonance frequency of the drum does not match that of any of the surrounding components, and also so that the natural resonance frequency of the drum is not in the audible range. As a result, if vibration should occur, it is less destructive, since the frequency does not match that of the surrounding components. In addition, the noise is not audible (or is less likely to be audible) to the operator or those in the vicinity of operation of the apparatus. However, if a noise problem is found to occur in existing equipment, it can be quite costly to redesign tooling necessary to change the dimensions (e.g., the tube thickness) of the drum. Further, even if the tube thickness is modified, such a solution might not be satisfactory in addressing noise and/or vibration in all replacement parts situations, since the process cartridge (within which the drum is disposed) can vary with different manufacturers and models, and the manufacturer or refurbisher of process cartridges (or other components) is not always the same as that of the photosensitive drum. 
     Another approach to minimizing noise and/or vibration in photosensitive drums has been to insert a plug or weight at a predetermined location within the drum. However, the use of a plug-type insert can be undesirable in that the plug is typically required to be inserted at a particular axial location within the drum, and if improperly placed, the plug will not perform properly, and could even worsen the noise or vibration problems. In addition, the plug must be either adhered in place, or an interference fit can be utilized so that the plug is secured in place once inserted. Fixing the plug with an adhesive can be cumbersome, and could result in the adhesive being inadvertently disposed at locations other than desired, or the plug could shift if the drum is transported prior to curing of the adhesive. Bonding the insert to the drum also complicates recycling of the drum. If an interference fit is utilized, the drum could be deformed upon insertion. Further, since the drum is supported at the location of the plug, but not in other areas, the performance and response of the drum at the location of the plug might not be consistent with that of locations of the drum other than that where the plug is disposed. 
     Another problem that has arisen is that the photosensitive coatings on the outer surface of the drums can be damaged when they are engaged by tools used to hold the drum during a manufacturing process. Therefore, it has been known to use an expanding chuck to hold the drum while a process is being performed on it by expanding the expanding chuck against the inner surface of the drum. However, if a high insertion force is required for a particular insert, the expanding chuck must exert a correspondingly large radially outward force in order to overcome the insertion force, to thereby hold the drum in a proper orientation. Furthermore, if an insert requires a high insertion force because its outer diameter is larger than that of the inner diameter of the drum, the circularity of the drum can be distorted during insertion. Therefore, ideally, an insert is inserted with little or no insertion force, i.e., the insert only slightly touches or does not contact the inner surface of the drum during insertion. 
     Referring now to FIGS. 3-6, insert  50 , in accordance with the present invention, is shown therein. As shown in FIG. 3, insert  50  is preferably formed as a tubular member  59  having an outer diameter  52  and an inner diameter  54 . As shown in FIG. 3, outer diameter  52  is the outer diameter of insert  50  in a relaxed state. Preferably, outer diameter  52  is larger than an inner diameter  62  of photosensitive drum  60 , as shown in FIG.  4 . 
     According to the invention, insert  50  is configured such that outer diameter  52  of insert  50  can be reduced to a diameter  56  which is less than or equal to inner diameter  62  of photosensitive drum  60 , when insert  50  is elongated along its longitudinal axis  58 . For example, referring now to FIG. 5, when insert  50  is elongated along its longitudinal axis  58  in the direction of arrows A, the outer diameter of insert  50  reduces to an outer diameter  56  which is less than or equal to inner diameter  62  of the photosensitive drum  60 . Preferably, insert  50  is made from an elastic material which allows the outer diameter of insert  50  to reduce to diameter  56 , which is less than or equal to inner diameter  62 , when insert  50  is elongated in its longitudinal direction, within its elastic limits of distortion. 
     For example, it is well known in the art of solid mechanics that when an elastic member is stretched in a first direction, the elastic member will contract in a direction perpendicular to the first direction, so as to generally maintain a constant volume. As shown in FIG. 5, for example, when insert  50  is elongated in the direction of arrows A, the diameter of insert  50  shrinks in the direction of arrows B. As shown in FIG. 6, when insert  50  is released so as to allow insert  50  to return to a relaxed state, insert  50  contracts in the direction of arrows C, which thereby causes an expansion of its outer diameter in the direction of arrows D. Preferably, outer diameter  52  of insert  50  in a relaxed state, is chosen such that when insert  50  is provided within a photosensitive drum  60  as shown in FIG. 6, the outward radial force in the direction of arrows D is sufficient to anchor insert  50  within drum  60  so that it is not necessary to use an adhesive to ensure the immobilization of insert  50  with respect to drum  60 . 
     Insert  50  may be formed of any elastic material. However, in a presently preferred embodiment, insert  50  is made from an elastomeric material such as neoprene. Preferably, the material used for insert  50  has an elastic elongation limit between 100%-500% and a yield strength between 10,000 to 100,000 psi. Insert  50  may also be constructed from a “filled” material, such as resin with carbon black added. By constructing an insert with such a material, a single insert can be sized to fit various sizes of photoconductive drums, thereby reducing the burden of stocking different sized inserts for different sized drums. Furthermore, such material is readily available and relatively easy to obtain in various sizes. 
     As an illustrative example of insert  50 , neoprene tubing was formed with an outer diameter of approximately 30 mm in a relaxed state, a wall thickness of approximately 8 mm, and a weight of approximately 200 gm/ft. The tubing was stretched until the outer diameter was reduced to approximately 26 mm, and was then inserted into a photosensitive drum having an inner diameter of approximately 28 mm, thereby providing approximately 1 mm of clearance between the outer surface of the tubing and the inner surface of the drum. Once the tubing was moved to a desired position within the drum, the tubing was released and thereby allowed to expand and increase a pressure contact between the outer surface of the tubing and the inner surface of the drum. Since the outer diameter of the tubing in a relaxed state was 30 mm, and the inner diameter of the drum was 28 mm, the tubing provided an ample radially outward force for anchoring the tubing into the drum without the need for adhesive. Furthermore, since the tubing was elongated until there was a 2 mm difference between the outer diameter of the tubing and the inner diameter of the drum, the tubing could be inserted with zero insertion force. 
     An alternative embodiment of insert  50  is shown in FIG. 7, wherein insert  50  is constructed with a first longitudinal member  70  and a plurality of longitudinally extending members  72  provided around the periphery of member  70 . In this embodiment, as in the previous embodiment, it is preferable that an outer diameter  52  of insert  50  is greater than an inner diameter  62  of a photosensitive drum into which insert  50  is provided. In this embodiment, first longitudal member  70  may be in the form of a tubular member constructed of an elastic material. Similarly, longitudinally extending members  72  may be in the form of tubular or rod shaped members, not necessarily made of the same material as first longitudinal member  70 . By constructing insert  50  as a tubular member, a shaft may be installed through the center  74  of insert  50  which is commonly used in image forming apparatuses. 
     A further embodiment of the insert is shown in FIGS. 8-10. As shown in the FIGS. insert  50  is constructed in the form of a corrugated sleeve  75 . In the presently preferred embodiment, corrugated sleeve  75  has a corrugated shape defining a plurality of annular corrugations  76  formed along the longitudinal axis  58  of the insert  50 . The corrugations  76  define inner folds  77  and outer folds  78 . As illustrated in FIGS. 8 and 9, sleeve  75  has an outer diameter  52  that is greater than the inner diameter  62  of drum  60 . By constructing sleeve  75  with corrugations as such, the outer diameter  52  of sleeve  75  is easily reduced upon elongation, as shown in FIG.  9 . Furthermore, the corrugations provide a structure which is sufficiently elastic to generate a radially outward force for anchoring the insert  50  to the inner surface  64  of drum  60 . 
     Preferably, a stiffness of sleeve  75  at the inner folds  77  is larger than a stiffness of the sleeve  75  at the outer folds  78 . By constructing sleeve  75  as such, the degree of reduction of the outer diameter  52  of sleeve  75  achieved when sleeve  75  is elongated, is enhanced. For example, since the stiffness of sleeve  75  at the inner folds  77  is larger than that at the outer folds, the inner folds  77  resist expansion more than the outer folds  78 . For example, as sleeve  75  is elongated, the inner folds  77  and outer folds  78  are expanded such that the inner folds move outwardly, and the outer folds move inwardly. Therefore, where the stiffness of the inner folds is larger than that of the outer folds, the outer folds are forced to deflect inwardly more than they would if the stiffness of the inner and outer folds were equal. Therefore, the overall radial contraction of sleeve  75  is enhanced when sleeve  75  is elongated along longitudinal axis  58 . Preferably, in order to form inner folds  77  with a higher stiffness than outer folds  78 , a thickness  77 A of inner folds  77  is greater than a thickness  78 A of outer folds  78 A. For example, in a presently preferred embodiment, corrugated sleeve  75  may be made out of a widely available synthetic rubber, such as polybutadiene, with thickness  77 A of approximately 1.0 mm and a thickness  78 A of approximately 0.9 mm 
     Also preferably, sleeve  75  has at least one closed end  79 A. However, it is not necessary for closed end  79 A to form a gas-tight closure. Rather, closed end  79 A is preferably configured to serve as a stop for a tool used for elongating sleeve  75 . For example, as shown in FIG. 9, a rod  81  may be used to elongate sleeve  75 , by inserting rod  81  through open end  79 B, until rod  81  abuts closed end  79 A. In this position, rod  81  can be is pushed against closed end  79 A to thereby elongate sleeve  75  such that the outer diameter  52  of sleeve  75  is sufficiently reduced to allow sleeve  75  to pass into drum  60 . As shown in FIG. 9, since annular corrugations  76  allow sleeve  75  to be easily elongated, and thereby easily reduced in outer diameter, it is not necessary to anchor open end  79 B of sleeve  75  during insertion. Rather, the natural resistance generated between the outer surface of sleeve  75  and the inner surface  64  of drum  60  is sufficient to cause elongation of sleeve  75  when closed end  79 A is pushed through drum  60 . 
     Alternatively, closed end  79 A of sleeve  75  can be formed with an end plate which may be flat or in the form of a receptacle  79 C, as shown in FIG.  10 . By forming closed end  79 A with receptacle  79 C, the proper orientation of rod  81  during insertion is ensured. 
     Referring now to FIGS. 9,  11  and  12 , a method for inserting insert  50  into a photosensitive drum  60  will be described hereinbelow. 
     As shown in FIGS. 11 and 12, a method for inserting insert  50  into a photosensitive drum  60  includes elastically elongating insert  50  in a longitudinal direction, from a relaxed state wherein the insert has an outer diameter larger than an inner diameter of the photosensitive drum, such that an outer diameter of the insert is elastically reduced to a diameter equal to or less than the inner diameter of the photosensitive drum  60 . Insert  50  is then inserted into the drum  60 , wherein after insert  50  is released, and allowed to return to a relaxed state, a pressure contact of the outer surface of insert  50  with the inner surface of the photosensitive drum  60  increases. In the present embodiment, apertures  80  are formed in the first and second ends of insert  50 , and engaging means  90  such as a wire cables  92  and  94  are interfaced with first end  82  and second end  84  of insert  50 . Wire cable  92  is then threaded through photosensitive drum  60  and wire cable  94  is immobilized, with a vise, or the like (not shown). Tension is then applied to wire cable  92  in the direction of arrow E, as shown in FIG. 12, so as to cause insert  50  to elastically elongate such that the outer diameter of insert  50  reduces to an outer diameter  56  which is equal to or less than inner diameter  62  of photosensitive drum  60 . Once insert  50  has been elongated as Such, drum  60  can be moved over insert  50  until insert  50  is inside drum  60 . Once insert  50  is positioned as desired, wire cables  92  and  94  can then be released such that the outer diameter of insert  50  expands in the direction of arrows D, shown in FIG. 6, and thereby increases a pressure contact between the inner surface  64  of drum  60  and outer surface  59  of insert  50 . 
     When drum  60  is moved over insert  50 , as shown in FIG. 12, a misalignment between photosensitive drum  60  and insert  50  may cause first end  82  of insert  50  to lock against an end of drum  60 , thereby preventing drum  60  from sliding over insert  50 . Therefore, as shown in FIG. 13, first end  82  of insert  50  is preferably rounded so that the insertion of insert  50  into drum  60  is simplified. 
     Referring now to FIG. 9, as discussed above, sleeve  75  can be elongated by inserting a tool such as rod  81  through open end  79 B, and against closed end  79 A. As shown in FIG. 9, the friction generated by contact between the outer surface of sleeve  75  and the inner surface  64  of photosensitive drum is sufficient for causing, when rod  81  is pressed against closed end  79 A, the elongation of sleeve  75  such that the outer diameter  52  of sleeve  75  is reduced such that sleeve  75  can slide into drum  60 . Alternatively, open end  79 B of sleeve  75  could be anchored by hand or machine, such that sleeve  75  is elongated to such an extent that the outer diameter  52  of sleeve  75  is reduced to a diameter smaller than that of the inner surface  64  of drum  60 . By performing the method of inserting as Such, sleeve  75  can be inserted without generating any substantial friction with the inner surface  64  of drum  60 . 
     Referring now to FIGS. 14 and 15, a further embodiment of the method for inserting an insert  50  into photosensitive drum  60  is shown therein. As shown in FIG. 14, a tool  100  for elongating insert  50  may include engaging means  90  for engaging first end  82  and second end  84  of insert  50 . In this embodiment, engaging means  90  may be constructed of expanding chucks  102  and  104 . Each of expanding chucks  102  and  104  may be constructed with three way (or more) expanding chucks which are configured to engage with the inner surface  106  of insert  50 . Expanding chuck  102  may be attached to first arm  108  and expanding chuck  104  may be attached to second arm  110 . In this embodiment, arms  108  and  110  are attached to device  112  which is configured to move arms  108  and  110  relative to each other in a longitudinal direction and to control the expansion of chucks  102  and  104 . In operation, with expanding chuck  102  engaged with the inner surface  106  of first end  82  of insert  50  and expanding chuck  104  engaged with inner surface  106  of second end  84  of insert  50 , first arm  108  of tool  100  can be moved in the direction of arrow F while second arm  110  may be moved in the direction of arrow G so as to elongate insert  50 . By using device  110  constructed as such, there are no components to interfere with the insertion of drum  60  over insert  50 . Therefore, drum  60  may be held from a first end  61  of drum  60  with an expanding chuck  114 , for example, while tool  100  can be used to elongate insert  50  and insert insert  50  into drum  60  from second end  63  of drum  60 . Using this method, insert  50  may be inserted into drum  60  without the need to contact any portion of the outer surface of drum  60 , thereby preventing damage to the outer surface of drum  60 . 
     Similarly, as shown in FIG. 9, expanding chuck  114  can be used to maintain the position of drum  60  while sleeve  75  is inserted therein. Since sleeve  75  requires little or no insertion force, an expanding chuck is sufficient for overcoming the forces generated during insertion of sleeve  75 . 
     Referring now to FIGS. 16 and 17, a further embodiment of a method for inserting an insert into a photosensitive drum is shown. As shown in FIG. 16, engaging means  90 , such as expanding jigs  120  and  122  may be provided on arms  124  and  126  so as to elongate insert  50  in direction of arrows H so that insert  50  can be inserted into drum  60 , as shown in FIG.  14 . In this embodiment, drum  60  must be threaded over arm  124 , similarly to the embodiment shown in FIGS. 11 and 12 wherein drum  60  is threaded over wire cable  92 . Also as shown in FIG. 17, once insert  50  has been positioned within drum  60 , arms  124  and  126  can be moved towards each other in the direction of arrows I so that insert  50  can expand and thereby increase a pressure contact between inner surface  64  of drum  60  and outer surface  59  of insert  50 . In this embodiment, it is also preferable to provide first end  82  with a rounded shape, such as that shown in FIG. 13, so that insert  50  can be inserted into drum  60  with reduced risk that first end  82  may impact an end of drum  60  during insertion. 
     Referring now to FIG.  18 . once insert  50  has been inserted into drum  60 , first and second ends  61  and  63  of drum  60  can be provided with end pieces  130  and/or  132 . End pieces  130  and/or  132  may be in the form of a gear  134  and/or flange  136 . Typically, gear  134  is provided to a drum  60  so as to provide an interface to a motor (not shown) for driving drum  60 . Flange  136 , is typically provided so as to provide a bearing surface for supporting drum  60 . Alternatively, end  61  of drum  60  could be provided with a gear  134  which may be used for driving other rollers or gears. In any event, typically gears  134  and/or flanges  136  must be bonded to the inner surface  64  of drum  60  with an adhesive. However, use of an adhesive raises a number of problems in the manufacture of photosensitive drums. 
     For example, if adhesive must be used during the manufacture of photosensitive drum  60 , the risk that adhesive may be splashed onto the outer surface  65  of drum  60 , is increased, which may require that drum  60  be immediately discarded. Furthermore, adhesives on the outer surface may affect the photosensitivity and/or performance of drum  60  in operation. Furthermore, when an adhesive is used to bond a component to a drum such as drum  60 , it is difficult to remove such components when a drum  60  is to be recycled. Therefore, it is desirable to avoid the use of adhesives. 
     In light of the problems of using adhesives for bonding end pieces to photosensitive drums, in one embodiment of the present invention, gears  134  and/or flanges  136  may be bonded directly to insert  50 , after insert  50  has been inserted into drum  60 . For example, as shown in FIG. 18, gear  134  and flange  136  may include connecting member  138  which is engaged with inner surface  106  of insert  50 . Therefore, by attaching end pieces  130  and/or  132  with insert  50 , gear  134  and/or flange  136  can be attached to drum  60  without the use of adhesives directly bonded to a surface of drum  60 . 
     After insert  50  is disposed within drum  60 , and end pieces  130  and  132  such as gear  134  and/or flange  136  are mounted to each end of the drum  60 , drum  60  can then be rotatably mounted upon a shaft (if a shaft is utilized, and disposed within a process cartridge to be utilized in a photocopier or printer). 
     As discussed above, the present invention provides several important advantages over noise reducing inserts of the prior art. Firstly, by constructing a noise prevention device for a photosensitive drum from an elastic member which has an outer diameter greater than the inner diameter of the drum in a relaxed state, and which is configured such that it can be elastically elongated and thereby reduced in outer diameter to be smaller than the inner diameter of the drum, the present invention achieves the dual goals of providing a noise reducing insert that can be inserted with little or no insertion force, while generating the relatively high radially outward force produced by an interference fit. Furthermore, since the outer diameter of the insert in a relaxed state is larger than the inner diameter of the drum, and since materials which can be elastically distorted as described above tend to possess good noise dampening properties, the insert provides numerous points of contact between the insert and the inner surface of the drum, thereby achieving a strong noise dampening effect. 
     Additionally, since the insert according to the present invention can be used to absorb the vibrations and noises generated during operation of an image forming apparatus which uses the insert, there is no need to increase the thickness of the drum. Therefore, the present invention also allows the drum to be manufactured with virtually any thickness currently used for image forming apparatuses. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise and as specifically described herein.