Abstract:
A scan unit for an imaging device having a movable mirror and one or more light sources. A light beam generated by each light source is directed towards the movable mirror, movement of the mirror causing each light beam that is reflected by the mirror to follow a distinct scan pattern. An optical assembly is associated with each reflected light beam to form an optical path for each reflected light beam from the mirror. A housing in which the movable mirror, the one or more light sources and the optical assembly are secured has at least a portion made from electrically conductive material for shielding an interior of the housing from electromagnetic fields external to the housing. A light drive circuitry card is disposed in the interior of the housing and communicatively coupled to the one or more light sources for driving the one or more light sources.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is related to U.S. patent application Ser. No. 13/250,157, filed Sep. 30, 2011, and entitled, “Laser scan unit housing for an imaging device,” the content of which is incorporated by reference herein in its entirety. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     REFERENCE TO SEQUENTIAL LISTING, ETC. 
     None. 
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates generally to a laser scan unit (LSU) of an electrophotographic imaging device, and particularly to a housing for the LSU of the electrophotographic imaging device. 
     2. Description of the Related Art 
     In laser imaging devices, toner is transferred to sheets of media using electrophotographic techniques involving a photoconductive drum as well as an LSU which scans an image on the photoconductive drum in order for toner to temporarily adhere for subsequent transfer to a sheet of media. The electrophotographic techniques typically produce unwanted electromagnetic interference (EMI). The risk of EMC-related problems affects internal components of the laser imaging device, particularly the LSU. Toroids, which have been used to at least partly reduce EMI problems, are expensive and thus in many instances cost prohibitive. 
     SUMMARY 
     Example embodiments of the present disclosure overcome shortcomings of prior laser scan units and thereby satisfy a need for an LSU for an imaging device having improved EMI protection. According to an example embodiment, the LSU includes a movable mirror, one or more light sources and an optical assembly. A light beam generated by each light source is directed towards the movable mirror such that movement of the mirror causes each light beam that is reflected by the mirror to follow a distinct scan pattern. The optical assembly forms an optical path for each light beam reflected by the mirror. The LSU also includes a housing in which the movable mirror, the one or more light sources and the optical assembly are secured. At least a portion of the housing is made from electrically conductive material for shielding an interior of the housing from electromagnetic fields external thereto. The LSU also includes a light drive circuitry card which provides video drive signals for driving the one or more light sources. In the example embodiment, the light drive circuitry card is disposed in the interior of the housing and communicatively coupled to the one or more light sources therein. 
     The housing may include a metal housing. The metal housing may be constructed from dead soft steel. The housing may be constructed from one of a metal and a metal-coated plastic. The housing may include a metallic mesh disposed about the interior or exterior of the housing. The housing thus forms a Faraday shield so as to at least lessen EMI effects on the LSU components contained within the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of the disclosed embodiments, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of the disclosed embodiments in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a side schematic view of an image forming device according to one example embodiment. 
         FIG. 2  is a simplified plan view of a laser scan unit (LSU) of the image forming device of  FIG. 1 . 
         FIG. 3  is an interior perspective view of the LSU of  FIG. 2 . 
         FIG. 4  is a side cross sectional view of the LSU of  FIG. 3 . 
         FIGS. 5 and 6  are exterior perspective views of the LSU housing of  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
     Spatially relative terms such as “top,” “bottom,” “front,” “back” and “side,” “above,” “under,” “below,” “lower,” “over,” “upper,” and the like, are used for ease of description to explain the positioning of one element relative to a second element. Terms such as “first,” “second,” and the like, are used to describe various elements, regions, sections, etc. and are not intended to be limiting. Further, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 
     Furthermore, and as described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the disclosure and that other alternative configurations are possible. 
     Reference will now be made in detail to the example embodiments, as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  illustrates an image forming device  10  according to an example embodiment. Image forming device  10  includes a first toner transfer area  15  having four developer units  20 , including developer rolls  25 , that substantially extend from one end of image forming device  10  to an opposed end thereof. Developer units  20  are disposed along an intermediate transfer member (ITM)  30 . Each developer unit  20  holds a different color toner. The developer units  20  may be aligned in order relative to the direction of the ITM  30  indicated by the arrows in  FIG. 1 , with the yellow developer unit  20 Y being the most upstream, followed by cyan developer unit  20 C, magenta developer unit  20 M, and black developer unit  20 K being the most downstream along ITM  30 . 
     Each developer unit  20  is operably connected to a toner reservoir  35  (i.e., toner reservoirs  35 Y,  35 C,  35 M,  35 K) for receiving toner for use in a printing operation. Each toner reservoir  35  is controlled to supply toner as needed to its corresponding developer unit  20 . Each developer unit  20  is associated with a photoconductive member  40  (i.e., photoconductive memebers  40 Y,  40 C,  40 M,  40 K) that receives toner therefrom during toner development to form a toned image thereon. Each photoconductive member  40  is paired with a transfer member  45  (i.e., transfer memebers  45 Y,  45 C,  45 M,  45 K) to define a transfer nip  50  for use in transferring toner to ITM  30  at first transfer area  15 . 
     Image forming device  10  further includes LSU  70 . During color image formation, the surface of each photoconductive member  40  is charged to a specified voltage by a charge roller  55 . At least one laser beam LB from LSU  70  is directed to the surface of each photoconductive member  40  and discharges those areas it contacts to form a latent image thereon. In one embodiment, areas on the photoconductive member  40  illuminated by the laser beam LB are discharged. The developer unit  20  then transfers toner to photoconductive member  40  to form a toner image thereon. The toner is attracted to the areas of the surface of photoconductive member  40  that are discharged by the laser beam LB from LSU  70 . 
     ITM  30  is disposed adjacent to each of developer unit  20 . In this embodiment, ITM  30  is formed as an endless belt disposed about a drive roller and other rollers. During image forming operations, ITM  30  moves past photoconductive members  40  in a clockwise direction as viewed in  FIG. 1 . One or more of photoconductive members  40  applies its toner image in its respective color to ITM  30 . For mono-color images, a toner image is applied from a single photoconductive member  40 K. For multi-color images, toner images are applied from two or more photoconductive members  40 . In one embodiment, a positive voltage field formed in part by transfer member  45  attracts the toner image from the associated photoconductive member  40  to the surface of moving ITM  30 . 
     ITM  30  rotates and collects the one or more toner images from the one or more photoconductive members  40  and then conveys the one or more toner images to a media sheet at a second transfer area  65 . Second transfer area  65  includes a second transfer nip formed between a back-up roller  71  and a second transfer member  75 . 
     A fuser assembly  80  is disposed downstream of second transfer area  65  and receives media sheets with the unfused toner images superposed thereon. In general terms, fuser assembly  80  applies heat and pressure to the media sheets in order to fuse toner thereto. After leaving fuser assembly  80 , a media sheet is either deposited into an output media area  85  or enters duplex media path  90  for transport to second transfer area  65  for imaging on a second surface of the media sheet. 
     Image forming device  10  is depicted in  FIG. 1  as a color laser printer in which toner is transferred to a media sheet in a two step operation. Alternatively, image forming device  10  may be a color laser printer in which toner is transferred to a media sheet in a single step process—from photoconductive members  40  directly to a media sheet. In another alternative embodiment, image forming device  10  may be a monochrome laser printer which utilizes only a single developer unit  20  and photoconductive member  40  for depositing black toner directly to media sheets. Further, image forming device  10  may be part of a multi-function product having, among other things, an image scanner for scanning printed sheets. Still further, image forming device  10  may utilize other processes and/or architectures for transferring toner to media sheets, such as a dual component based architecture. 
     Image forming device  10  further includes a controller  95  and an associated memory  97 . Though not shown in  FIG. 1 , controller  95  may be coupled to components and modules in image forming device  10  for controlling same. For instance, controller  95  may be coupled to toner reservoirs  35 , developer units  20 , photoconductive members  40 , fuser assembly  80  and/or LSU  70  as well as to associated motors (not shown) for imparting motion thereto. It is understood that controller  95  may be implemented as any number of controllers and/or processors for suitably controlling image forming device  10  to perform, among other functions, printing operations. 
     With reference now to  FIGS. 2-4 , LSU  70  includes a single rotatable polygonal mirror  310  that is powered by a motor  371 , and a pre-scan optical assembly  307 . Polygonal mirror  310  is supported for rotation about a rotational axis and includes a plurality of facets  372 . It is understood that mirrors other than a rotatable, polygonal mirror may be utilized in LSU  70 . In an alternative embodiment, LSU  70  may include an oscillating mirror, such as a galvanometric mirror (not shown), instead of polygonal mirror  310 . 
     Pre-scan optical assembly  307  includes first laser diode  311  generating laser beam  311 A, second laser diode  312  generating laser beam  312 A, third laser diode  313  generating laser beam  313 A, and fourth laser diode  314  generating laser beam  314 A. It is understood that other light sources may be employed instead of laser diodes. Pre-scan optical assembly  307  also includes one or more lenses, such as collimation lenses  320 A- 320 D associated with each laser diode  311 - 314 , respectively, and first and second pre-scan lens assemblies  308  and  309 . 
     Pre-scan optical assembly  307  further includes drive circuitry card  300  ( FIGS. 2 and 3 ) onto which laser diodes  311 - 314  are mounted. Laser diode driver components (not shown) are also mounted onto drive circuitry card  300  which provide the necessary drive for powering laser diodes  311 - 314 . Each of laser beams  311 A,  312 A,  313 A and  314 A is modulated by a video signal from controller  95  (via cable  100 ) so as to write pixels or pels as the beam scans along a corresponding scan path. For example, laser beam  311 A is modulated according to a video signal corresponding to the cyan image plane. 
     Generally, each laser beam  311 A,  312 A,  313 A, and  314 A is reflected off the rotating polygonal mirror  310  and is then directed towards a corresponding one of the photoconductive drums  40  by select mirrors and lenses in a post-scan optical assembly  317 , as shown in  FIGS. 2-4 . In particular, beam  311 A, after being reflected off the rotating polygonal mirror  310 , passes through collimation lens  319 , is reflected by fixed mirrors  302 A and  304 A before passing through focus lens  309 A and exiting LSU  70 . Second beam  312 A, after reflecting from rotating polygonal mirror  310  and passing through lens  319 , is reflected by reflection mirrors  302 B and  304 B and passes through focus lens  309 B before exiting LSU  70 . Third beam  313 A, after being reflected by rotating polygonal mirror  310  and passing through lens  319 , is reflected by mirrors  302 C and  304 C and then passes through focus lens  309 C before exiting LSU  70 . Fourth beams  314 A, after reflecting from rotating polygonal mirror  310  and passing through lens  319 , is reflected by reflection mirror  302 D and then passes through focus lens  309 D before exiting LSU  70 . After leaving LSU  70 , each beam  311 A- 314 A strikes a corresponding photoconductive drum  40  to create the latent image thereon. In particular, the rotation of polygonal mirror  310  and positioning of mirrors  302  and  304  of post-scan optical assembly  317  causes each laser beam  311 A- 314 A to repeatedly sweep across its corresponding photoconductive drum  40  so as to form a latent image on the drum. It is understood that pre-scan assembly  307  and post-scan assembly  317  may use a different number and arrangement of mirrors and lens in creating scan patterns on photoconductive drums  40 . 
     LSU  70  includes LSU housing  500  in which pre-scan assembly  307  and post-scan assembly  317  are disposed. With reference to  FIGS. 3-5 , LSU housing  500  includes a first portion  80  that is substantially bowl-shaped, having a concave inner surface to which components of assembly  307  and most of assembly  317  are connected. LSU housing  500  further includes a second portion  90  ( FIG. 6 ) which serves as a cover or lid and to which lenses  309  are mounted. First portion  80  and second portion  90  define a substantially fully contained interior in which pre-scan assembly  307  and post-scan assembly  317  are disposed. In one example embodiment, LSU housing  500  is a metal housing and is constructed from dead soft steel. Alternatively, LSU housing  500  may be constructed from one of a metal and a metal-coated plastic. In another example embodiment, LSU housing  500  is formed from a non-metallic material that is encased in or otherwise combined with a conductive mesh  502  (see  FIG. 5 ). LSU housing  500 , in this way, serves to shield the components within LSU housing  500  from electromagnetic interference. It is understood that LSU housing  500  may have other shapes or otherwise be formed from differently sized and shaped portions. For instance, first portion  80  may itself be formed from multiple sub-portions permanently or removably connected together. In particular, an upper part of first portion  80 , as viewed from  FIGS. 4 and 5 , may be removable from the remaining part of first portion  80 , thereby resulting in LSU housing  500  having two covers or lids. It is also understood that a second cover or lid may be located elsewhere along first portion  80 . It is further understood that second portion  90  may itself be formed from multiple sub-portions permanently or removably connected together. 
       FIGS. 2 and 3  illustrate drive circuitry card  300  disposed within LSU housing  500  and cable  100 , which communicates with and provides video signals to drive circuitry card  300  for controlling laser diodes  311 - 314 . A first end of cable  100  is communicatively coupled to drive circuitry card  300  and disposed in the interior of first portion  80  of LSU housing  500 . Cable  100  also includes a second end extending from LSU  70  through a space  4  defined between a first portion  80  second portion  90  of LSU housing  500  (see  FIG. 5 ). Cable  100  may be an unshielded cable, such as a ribbon cable. In an example embodiment, an entire portion of cable  100  is unassociated with an electromagnetic filter or other components, such as a toroid, for diminishing the effects of electromagnetic radiation. 
     The foregoing description of several methods and an embodiment of the invention have been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.