Patent Publication Number: US-8121521-B2

Title: Support structure for a photoconductive drum of a production printing system

Description:
BACKGROUND 
     1. Field of the Invention 
     The invention relates to the field of production printing systems and, in particular, to a support structure for a photoconductive drum of a printing system. 
     2. Statement of the Problem 
     Businesses or other entities having a need for volume printing typically purchase a production printing system. A production printing system comprises a high-speed printer used for volume printing, such as 100 pages per minute or more. The production printing systems are typically continuous-forms printers that print on paper or some other printable medium that is stored on large rolls. Some continuous-forms printers are able to print on paper up to 20 inches wide or more. 
     One type of high-speed printer is a laser printer. The core component of a laser printer is the photoreceptor, which is typically a revolving drum or cylinder. The photoreceptor is made out of highly photoconductive material that is discharged by light photons, and is often referred to as a “photoconductive drum” or simply a “drum”. Depending on the throughput of a laser printer, the photoconductive drum may have to be replaced quite often, such as every couple weeks. Unfortunately in many production-type laser printers, the task of replacing the drum is quite burdensome. First, tools are needed to replace the drum, such as a drum extension rod and wrenches. Secondly, the process of removing the old drum and installing a new drum requires some skill and time. The availability of the tools and the time and skill involved in replacing the drum typically does not allow a customer to replace the drum. Thus, a service engineer may have to be called to the customer&#39;s site to replace the drum, which may be costly to the customer. 
     SUMMARY 
     Embodiments described herein allow for easier and faster replacement of a drum in a laser production printing system. One embodiment comprises a drum support structure that secures a photoconductive drum within a printing system during operation. The drum support structure includes a plurality of ring members spaced in parallel along a longitudinal axis. The ring members have an outside diameter that corresponds with an inside diameter of the photoconductive drum so that the ring members fit within the photoconductive drum. The drum support structure also includes a plurality of connecting members that affix the ring members to one another. The drum support structure also includes an inner end cap that connects to an inner-most ring member through one or more connecting members and is adapted to contact one end of the drum. The drum support structure also includes an outer end cap that is adapted to fasten to an outer-most ring member and is further adapted to contact another end of the drum. When the outer end cap is fastened to the outer ring member, and the photoconductive drum is pressed between the inner end cap and the outer end cap and secured. 
     If the drum support structure described above is used to secure a photoconductive drum in a printing system, the photoconductive drum may be replaced more efficiently than in prior printing systems. Due to the configuration of the drum support structure, the drum support structure may be partially cantilevered out of the printing system on a drum axle. Even while cantilevered, the drum support structure stays on its original longitudinal axis on the drum axle so that it does not contact other components within the printing system. The photoconductive drum may then be removed by detaching the outer end cap from the outer ring member, and pulling the photoconductive drum from the drum support structure. This may be done without having to remove the drum support structure from the printing system. A new photoconductive drum may then be slid onto the drum support structure while it is cantilevered out, and the outer end cap may again be fastened to the outer ring member. The fastening of the outer end cap to the outer ring member secures the new photoconductive drum between the inner end cap and the outer end cap. The drum support structure with the new photoconductive drum may then be slid back into to the printing system. Thus, no tools are needed to replace the photoconductive drum, which saves time and means that most customers will be able to change the photoconductive drums themselves. There may be no need for a service engineer to come out to the customer site to replace the photoconductive drum, which saves the customer on service costs. All of this results in the customer having less down time in replacing a photoconductive drum within a printing system. 
     Other exemplary embodiments may be described below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings. 
         FIG. 1  illustrates a production printing system. 
         FIG. 2  illustrates a drum extension rod connected to a drum axle. 
         FIG. 3  illustrates a drum assembly slid out onto a drum extension rod. 
         FIG. 4  illustrates the printing system with a drum assembly removed. 
         FIG. 5  illustrates a drum assembly as removed from the printing system. 
         FIG. 6  illustrates an exploded view of a drum assembly. 
         FIG. 7  illustrates an exploded view of a drum assembly in an exemplary embodiment. 
         FIGS. 8A-E  illustrate a side view of end caps and ring members of a drum assembly in an exemplary embodiment. 
         FIG. 9  illustrates a drum slid onto a drum support structure in an exemplary embodiment. 
         FIG. 10  illustrates a drum attached to a drum support structure in an exemplary embodiment. 
         FIG. 11  illustrates an outer end cap in an exemplary embodiment. 
         FIG. 12  illustrates an inner end cap in an exemplary embodiment. 
         FIG. 13  illustrates a printing system with a drum assembly installed in an exemplary embodiment. 
         FIG. 14  illustrates a drum assembly slid out of a printing system a threshold distance in an exemplary embodiment. 
         FIGS. 15-16  illustrate an outer end cap removed from a drum assembly in an exemplary embodiment. 
         FIG. 17  illustrates a drum partially removed from a drum support structure in an exemplary embodiment. 
         FIG. 18  illustrates a drum removed from a drum support structure in an exemplary embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The figures and the following description illustrate specific exemplary embodiments of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope of the invention. Furthermore, any examples described herein are intended aid in understanding the principles of the invention, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the invention is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. 
       FIG. 1  illustrates a production printing system  100 . Printing system  100  includes many parts that are used for printing on a medium that are known to those skilled in the art. For the sake of brevity, the components in printing system  100  that are relevant for this discussion are drum assembly  101  and developer  104 . Drum assembly  101  includes an outer cylindrical member referred to as a photoconductive drum (not visible in  FIG. 1 ). The photoconductive drum is the member that has a photoconductive outer surface. Drum assembly  101  also includes a drum support structure  110 . Drum support structure  110  contacts the ends of the photoconductive drum to support the drum within printing system  100 . A more clear illustration of drum assembly  101  may be seen in  FIG. 6 . Developer  104  is in a fixed position with respect to drum assembly  101 , meaning that it does not drop down in printing system  100 . There is a very small spacing between drum assembly  101  and developer  104 . 
     Drum assembly  101  is mounted on a drum axle  106  (or drum shaft) and is operable to rotate along with drum axle  106  when in operation. Some portion of drum assembly  101  mates with a drive mechanism (not visible) within printing system  100  that is able to rotate drum assembly  101  at a desired rotation speed. The mounting of drum assembly  101  on drum axle  106  keeps drum assembly  101  on an axis so that it doesn&#39;t contact and damage other components proximate to drum assembly  101 , such as developer  104 . 
     As stated in the Background, the photoconductive drum will wear out with continued use and frequently requires replacing.  FIGS. 2-6  illustrate how the photoconductive drum is traditionally replaced. To start, a drum extension rod is connected to drum axle  106 .  FIG. 2  illustrates drum extension rod  202  connected to drum axle  106  (drum axle  106  is not visible in  FIG. 2 ). Drum extension rod  202  has a diameter that corresponds with the diameter of drum axle  106 , and is able to screw into or otherwise couple with drum axle  106 . Drum extension rod  202  also has a length about as long as drum assembly  101 . With drum extension rod  202  connected to drum axle  106 , drum assembly  101  may be slid off of drum axle  106  and out of printing system  100 .  FIG. 3  illustrates drum assembly  101  slid out onto drum extension rod  202 . In this figure, photoconductive drum  302  is visible as part of drum assembly  101 . By sliding drum assembly  101  out onto drum extension rod  202 , drum assembly  101  is not allowed to move from its axis and to contact other proximate components. For example, drum assembly  101  is not allowed to contact developer  104  while it is being removed, as developer  104  is at a fixed position in printing system  100 .  FIG. 4  illustrates printing system  100  with drum assembly  101  removed. 
     With drum assembly  101  removed from printing system  100 , drum  302  may be replaced in drum assembly  101 .  FIG. 5  illustrates drum assembly  101  as removed from printing system  100 .  FIG. 6  illustrates an exploded view of drum assembly  101 . Drum assembly  101  includes drum support structure  110  comprised of an inner support member  602  and an outer end cap  604 . Inner support member  602  slides onto drum axle  106  (see  FIG. 4 ), and mates with a drive mechanism within printing system  100  that rotates drum assembly  101  at a desired rotational speed. Inner support member  602  has a lip  610  that contacts one end of drum  302 . Similarly, outer end cap  604  has a lip  612  that contacts the other end of drum  302 . Outer end cap  604  is secured to inner support member  602  by bolts  620 . When outer end cap  604  is affixed to inner support member  602 , drum  302  is held securely in place. 
     To remove drum  302  from drum support structure  110 , bolts  620  are removed, and outer end cap  604  is disconnected from one end of drum  302 . Then, drum  302  may be disconnected from inner support member  602 . Next, a new drum  302  may be slid over inner support member  602  to contact lip  610 . Outer end cap  604  may again be affixed to inner support member  602 , which secures the new drum  302  between inner support member  602  and outer end cap  604 . At this point, drum assembly  101  is again assembled with a new drum  302  (see  FIG. 5 ). Drum assembly  101  may then be slid onto drum extension rod  202  (see  FIG. 3 ), and slid into printing system  100  (see  FIG. 2 ). After drum assembly  101  is slid into the proper position within printing system  100 , drum extension rod  202  may be removed (see  FIG. 1 ). 
     The process illustrated in  FIGS. 1-6  of replacing drum  302  may be burdensome. First, drum extension rod  202  is needed to properly align drum assembly  101  while it is being slid out of or into printing system  100 . Proper alignment is needed so that drum assembly  101  does not contact developer  104  or other delicate components when being slid out of or into printing system  100 . Secondly, drum assembly  101  needs to be completely removed from printing system  100  in order to replace drum  302 , which takes time and requires lifting of drum assembly  101  which can be quite heavy. Third, wrenches are needed to remove outer end cap  604  from inner support member  602 . Fourth, outer end cap  604  and inner support member  602  can get stuck onto the ends of drum  302 , and it can be difficult to separate drum  302  from outer end cap  604  and/or inner support member  602 . The difficulty of replacing drum  302  unfortunately does not allow a customer to replace drum  302  in an efficient manner. Thus, a service engineer may have to be called to the customer&#39;s site to replace drum  302 , which may be costly to the customer. 
     The following embodiments illustrate an improved drum support structure that allows for easier replacement of drum  302 . 
       FIG. 7  illustrates an exploded view of drum assembly  701  in an exemplary embodiment. Drum assembly  701  includes a drum support structure  710  comprised of an inner end cap  702 , one or more ring members  704 - 706 , and an outer end cap  708 . To orient the reader, the term “outer” used herein refers to an area or direction towards the outside of printing system  100  where drum assembly  701  may be removed. The term “inner” used herein refers to an area or direction towards the inside of printing system  100 . 
       FIGS. 8A-E  illustrate a side view of end caps  702  and  708 , and ring members  704 - 706  in an exemplary embodiment. An end cap comprises any circular structure having an outside diameter that fits within a photoconductive drum, and also having a lip, one or more tabs, or some other extension beyond the outside diameter that is able to contact an end of the photoconductive drum. As is shown in  FIG. 8A , inner end cap  702  has an outside diameter that fits within drum  302  (see also  FIG. 7 ). Inner end cap  702  also has a lip  720  that extends radially beyond the inside diameter of drum  302  and is adapted to engage with an end of drum  302 . As is shown in  FIG. 8B , outer end cap  708  has an outside diameter that fits within drum  302  (see also  FIG. 7 ). Outer end cap  708  also has a lip  722  that extends radially beyond the inside diameter of drum  302  and is adapted to engage with another end of drum  302 . 
     A ring member comprises any circular structure having an outside diameter that fits within a photoconductive drum and substantially contacts the inside surface of the drum. The circular structure of a ring member may also have an inside diameter (also referred to as a shaft diameter or bore diameter) that fits over a drum axle within a printing system. In  FIGS. 8C-E , each ring member  704 - 706  has an outside diameter that fits within drum  302  (see also  FIG. 7 ). An outside diameter may also be referred to as a circumference or an outer surface. Ring members  704 - 706  also have an inside diameter that fits over drum axle  106  of printing system  100  (see also  FIG. 4 ). 
     The structure of ring members  704 - 706  shown in FIGS.  7  and  8 A-E illustrate just one embodiment, and the structure of ring members  704 - 706  may be different in other embodiments. For example, ring member  704  may be a solid member between the outside diameter and the inside diameter instead of having the three arms illustrated in  FIGS. 7 and 8C . Additionally, ring members  704 - 706  may have two arms, four arms, five arms, etc, instead of having three as illustrated in FIGS.  7  and  8 C-E. 
     Ring members  704 - 706  may also include one or more voids  802  along its outside diameter. Voids  802  allow an operator of printing system  100  to be able to grab the inside surface of drum  302  when it is being removed from drum support structure  710 . 
     In  FIG. 7 , inner end cap  702  and ring members  704 - 706  are affixed to one another by connecting members  712 . Connecting members  712  affix inner end cap  702  and ring members  704 - 706  so that they are spaced apart along a longitudinal axis, where inner end cap  702  and ring members  704 - 706  are oriented transversely with respect to the longitudinal axis so that they are aligned in parallel. With inner end cap  702  and ring members  704 - 706  aligned in parallel along the longitudinal axis, the outside diameters of the inner end cap  702  and ring members  704 - 706  are also aligned to form a cylindrical skeleton that is able to fit within drum  302  which is also cylindrical on its inside surface. Although the spacing between inner end cap  702  and ring members  704 - 706  appears uniform in  FIG. 7 , other desired spacing may be used. 
     Connecting members  712  may be affixed to various positions of ring members  704 - 706 . Preferably, connecting members  712  are affixed in such a way that a surface of connecting members  712  is substantially flush with the outside diameter of ring members  704 - 706 . Thus, when drum  302  is slid onto or off of drum support structure  710 , the surface of connecting members  712  may also contact the inside surface of drum  302  to keep drum  302  on its axis. Although four connecting members  712  are used to connect each ring member  704 - 706  to another in this embodiment, more or less connecting members  712  may be used to connect ring members  704 - 706  to one another in other embodiments. 
     As can been seen in  FIG. 7 , ring member  705  may include one or more set screws  730 . Set screws  730  may have a knurled top, T-top, or other tool-less configuration so that they may be tightened or loosened by hand. When tightened, set screws  730  protrude into the inside diameter of ring member  705  and contact the drum axle  106  of printing system  100  (see also  FIG. 4 ). The purpose of set screws  730  is described later in relation to  FIG. 13 . 
     Drum support structure  710  may also include a sleeve  740  that connects between ring members  704 - 706 . Sleeve  740  comprises a tubular member that fits over drum axle  106  within printing system  100  (see also  FIG. 4 ). Sleeve  740  prevents toner from contaminating drum axle  106  during removal of drum  302 . If toner drops onto drum axle  106 , then drum support structure  710  might not be slid easily in the longitudinal direction and could seize on drum axle  106 . 
     To place drum  302  onto drum support structure  710 , drum  302  slides over the outside diameter of ring members  704 - 706 . Drum  302  also slides over the outside diameter of inner end cap  702  until the end of drum  302  contacts or abuts lip  720  that extends beyond the outside diameter of inner end cap  702 .  FIG. 9  illustrates drum  302  slid onto drum support structure  710  in an exemplary embodiment. 
     Outer end cap  708  is adapted to connect to the outer-most ring member  706 . Outer end cap  708  includes one or more screws  904  or other fastening devices that connect outer end cap  708  to outer ring member  706 . Screws  904  may have a knurled top, T-top, or other tool-less configuration so that they may be tightened or loosened by hand. When screws  904  are tightened, outer end cap  708  is pulled towards outer ring member  706 . The outside diameter of outer end cap  708  slides into drum  302  until the other end of drum  302  contacts or abuts lip  722  that extends beyond the outside diameter of outer end cap  708 . This causes drum  302  to be pressed between lip  720  of inner end cap  702  and lip  722  of outer end cap  708 , which secures drum  302  onto drum support structure  710 .  FIG. 10  illustrates drum  302  attached to drum support structure  710  in an exemplary embodiment, which comprises a completed drum assembly  701 . 
     In one embodiment, screws  904  in outer end cap  708  not only fasten outer end cap  708  to outer ring member  706 , but may also act to pry outer end cap  708  from outer ring member  706  when screws  904  are turned the opposite direction.  FIG. 1I  illustrates outer end cap  708  in an exemplary embodiment. As can be seen in  FIG. 11 , a fastener  1102  (also referred to as a locknut, E-clip, or C-clip) is attached behind the threads of screws  904 . When screws  904  are turned one direction (presumably clockwise), the threads of screws  904  will screw into a corresponding threaded hole in outer ring member  706 . Fasteners  1102  do not interfere with screws  904  being turned into outer ring member  706 , as they are attached behind the threads. When screws  904  are turned the opposite direction (presumably counter-clockwise), the threads of screws  904  will screw out of the corresponding threaded hole in outer ring member  706 . While screws  904  are screwed out, fasteners  1102  push against outer end cap  708  which acts to pry outer end cap  708  away from outer ring member  706 . This assists in separating outer end cap  708  from outer ring member  706  and drum  302 . 
     Also shown in  FIG. 11  is that outer end cap  708  has one or more beveled edges  1110 - 1111  on its outside diameter. The outside diameter of outer end cap  708  is illustrated as reference number  1120 . Outside diameter  1120  fits within the inside surface of drum  302 , and lip  722  extends beyond outside diameter  1120  so that it may contact one end of drum  302 . The edges  1110 - 1111  are beveled at any desired angle, such as 45 degrees. 
       FIG. 12  illustrates inner end cap  702  in an exemplary embodiment. As with outer end cap  708 , inner end cap  702  has one or more beveled edges  1210 - 1211  on its outside diameter. The outside diameter of inner end cap  702  is illustrated as reference number  1220 . Outside diameter  1220  fits within the inside surface of drum  302 , and lip  720  extends beyond outside diameter  1220  so that it may contact one end of drum  302 . The edges  1210 - 1211  are beveled at any desired angle, such as 45 degrees. The advantages of the beveled edges will be described later. 
     Drum support structure  710  as shown in  FIGS. 7-12  allows for drum  302  to be replaced in a more efficient manner within printing system  100 .  FIGS. 13-18  illustrate how drum  302  may be replaced using drum support structure  710 . Assume that drum  302  has been secured onto drum support structure  710  as shown in  FIG. 10 . Also assume that the resulting drum assembly  701  has been inserted into printing system  100 .  FIG. 13  illustrates printing system  100  with drum assembly  701  installed in an exemplary embodiment. Assume at this point that an operator of printing system  100  wants or needs to replace drum  302  in drum assembly  701  (see also  FIG. 10 ). 
     To start, the operator slides drum assembly  701  out of printing system  100  a threshold distance. In one embodiment, the operator slides drum assembly  701  until ring member  705  is proximate to the end of drum axle  106 . Depending on the size of drum assembly  701 , this may be in the range of 7-10 inches.  FIG. 14  illustrates drum assembly  701  slid out of printing system  100  a threshold distance in an exemplary embodiment. At this point, outer ring member  706  and outer end cap  708  are no longer contacting drum axle  106 , and drum assembly  701  is cantilevered out off of drum axle  106 . 
     With drum assembly  701  slid out the threshold distance, the operator may tighten one or more of the set screws  730  in ring member  705  (see also  FIG. 7 ). The set screws  730  hold drum assembly  701  from sliding along drum axle  106 . The operator may then turn screws  904  in outer end cap  708  to separate outer end cap  708  from outer ring member  706 . Outer end cap  708  may then be removed.  FIGS. 15-16  illustrate outer end cap  708  removed from drum assembly  701  in an exemplary embodiment. 
     With outer end cap  708  removed, the operator may slide drum  302  off of drum support structure  710  (see also  FIG. 7 ). To do so, the operator may reach through void  802  in outer ring member  706  to touch the inside surface of drum  302 . The operator may then pull drum  302  off of drum support structure  710  (see also  FIG. 7 ).  FIG. 17  illustrates drum  302  partially removed from drum support structure  710  in an exemplary embodiment. The operator may then completely remove drum  302 .  FIG. 18  illustrates drum  302  removed from drum support structure  710  in an exemplary embodiment. 
     At this point, the operator may obtain a new drum  302 , and slide the new drum  302  onto drum support structure  710  as is illustrated in  FIG. 17 . The operator slides the new drum  302  onto drum support structure  710  until one end of drum  302  contacts lip  720  of inner end cap  702  (see also  FIG. 7 ). This is illustrated in  FIG. 16 . The operator may then attach outer end cap  708  to outer ring member  706  using screws  904 , as is illustrated in  FIGS. 14-15 . Lip  722  of outer end cap  708  contacts the other end of the new drum  302  to secure the new drum  302  on drum support structure  710 . With outer end cap  708  installed, the drum assembly  701  is again complete. The operator may then loosen the set screws  730  in ring member  705  (see also  FIG. 7 ) so that drum assembly  701  is free to slide on drum axle  106 . The operator may then slide drum assembly  701  back into place within printing system  100 , which is illustrated in  FIG. 13 . 
     Drum support structure  710  advantageously allows the operator of printing system  100  to efficiently replace drum  302 . Due to the configuration of drum support structure  710 , drum assembly  701  may be partially cantilevered out on drum axle  106  (see  FIG. 14 ). Even while cantilevered, drum support structure  710  stays on its original longitudinal axis on drum axle  106  so that it does not contact other components within printing system  100 , such as developer  104 . Also, because the ring members  704 - 706  have an outside diameter that corresponds with the inside diameter of drum  302 , the overall shape of drum support structure  710  resembles the shape inside of drum  302 . Thus, drum  302  can be slid off of drum support structure  710  without tipping or otherwise going off-axis. If connecting members  712  are affixed to ring members  704 - 706  flush to the outer diameter of ring members  704 - 706 , then connecting members  712  also assist in keeping drum  302  on axis as it is slid off of drum support structure  710 . 
     Drum  302  may thus be removed from drum support structure  710  without having to remove drum support structure  710  from printing system  100 . As shown in  FIGS. 3-4 , the entire drum assembly  101  had to be removed in order to replace drum  302 . With the drum support structure  710  described in the above embodiments, the drum support structure  710  may remain cantilevered on drum axle  106  while the drum  302  is removed and a new drum is inserted, which saves time and alleviates the need to lift an entire drum assembly  701  from printing system  100 . Also, no tools are needed to replace a drum  302  on drum support structure  710 , which again saves time and means that most customers will be able to change the drums themselves. Thus, there may be no need for a service engineer to come out to the customer site to replace drum  302 , which saves the customer on service costs. All of this results in the customer having less down time in replacing a drum  302  within printing system  100 . 
     An additional advantage of drum support structure  710  is provided by the beveled edges on inner end cap  702  and outer end cap  708  as shown in  FIGS. 11 and 12 . When a new drum  302  is slid onto drum support structure  710  as in  FIG. 17 , the end of the new drum  302  slides very close to developer  104 . Thus, some of the toner stored in developer  104  may collect on the end of the new drum  302  while it is being slid across developer  104 . If this happens, the toner is scraped off of the end of the new drum  302  by the beveled edges  1210 - 1211  of inner end cap  702 . This means that it is less likely that toner will get stuck between the end of the new drum  302  and the outside diameter  1220  and/or lip  720  of inner end cap  702 . When the new drum  302  subsequently has to be removed from printing system  100 , the new drum  302  will be easily separated from inner end cap  702  because little or no toner will be in the connection points of the new drum  302  and inner end cap  702 . 
     Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. The scope of the invention is defined by the following claims and any equivalents thereof.