Abstract:
Raster Output Scanner (ROS) shutter system capable of blocking and unblocking harmful radiation selectably, semi-automatically or automatically. The system and uses thereof can be applied to various fields including scanners and printers.

Description:
BACKGROUND 
     Disclosed is a Raster Output Scanner (ROS) shutter system for protection against radiation generated in xerographic imaging equipment. 
     In image recording devices utilizing an electrostatographic system, a surface of a photoconductive drum or a photoreceptor is exposed to light (or some form of radiation) to form a latent image on the drum surface. Toner is then applied to the latent image to develop the image, and the developed image is transferred onto a recording sheet and is fixed by a fixing unit. Such an image recording device is employed in a copying machine as well as in a printer for printing output from a computer. It is well known in such machines that the user periodically will have to replace the cartridge containing the photoconductive drum and the toner after its useful life (in terms of the number of sheets) because the toner is used up and/or the photoconductor on the surface of the drum has worn thin or because a change in electrostatic characteristics results in defective charging or transfer as the photoconductive drum is repeatedly used. In some machines, a laser oscillator providing the required radiation may be accidentally actuated while replacing the cartridge, thereby directing a laser beam to the unprotected eyes of the operator, and possibly causing a serious problem. 
     Even though a switch may be provided to stop the operation of the oscillator in such situations, the suspension of the operation is not ensured if the switch is out of order. It is desirable, therefore, to provide an additional safety feature to assure that such a condition will not exist in such machines including the larger, more modern and more powerful printers such as the xerographic printing machines. 
     SUMMARY 
     Aspects disclosed herein include 
     a system comprising a xerographic image receptor; an exposure device directing exposure radiation to the image receptor; an element that selectably blocks and unblocks an aperture of the exposure device; a lever connected to actuate the element; and a spring biased over the element. The element comprises a shutter blade, the exposure device is a Raster Output Scanner (ROS) and the exposure forms a laser beam. 
     a system further comprising a housing that supports the ROS; an extension to the lever; one end of a connector attached to the extension; the opposing end of the connector fixedly connected to the housing; and wherein the connector is capable of moving the extension of the lever semi-automatically to raise the element away from the view of the ROS. 
     a system further comprising a torsion spring biasing the shutter; an actuator arm opposing the torsion spring; a plunger configured to communicate with the actuator arm; wherein the plunger is further configured to communicate with the actuator arm such that when the system moves into a docking position, the actuator arm raises the shutter out of view of the ROS; and wherein when the system moves to undock, the actuator arm retreats and torsion spring automatically forces the shutter blade to a position to block the laser beam. 
     a method providing a system comprising at least one movable station having at least one Raster Output Scanner (ROS) operable with a laser beam, a service position, a xerographic shutter system, the shutter system having an actuator connected to a shutter blade; moving the station to the service position; rotating the actuator selectably in a first direction; performing work on the station; moving the actuator selectably in a second direction opposite the first direction; and moving the station away from the service position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic drawing showing the various components of an electrostatographic printing machine incorporating the present disclosure. 
         FIG. 2  is a perspective drawing of a section of the system of  FIG. 1  showing the relationship between the recording or charging stations and the shutter system of the present disclosure. 
         FIG. 3   a  is a cross-sectional drawing of a charging station of  FIG. 2  showing the position of the shutter blade of the shutter system of the present disclosure not blocking a laser beam issued from a Raster Output Scanner (not shown). 
         FIG. 3   b  is a perspective drawing of the shutter system of the present disclosure showing the position of a selectably operated handle when the shutter system is selectably moved to block the laser beam of  FIG. 3   a.    
         FIG. 4   a  is a cross-sectional drawing of a recording station of  FIG. 3   a  showing an embodiment involving a semi-automatic shutter system utilizing an actuator or a handle to move the shutter blade of the present disclosure into a position where the shutter system does not block a laser beam issued from a Raster Output Scanner, ROS, (not shown). 
         FIG. 4   b  is a perspective drawing of an embodiment of  FIG. 4   a  showing the use of a cable for actuating the shutter blade to a position where it blocks radiation issuing from a ROS. 
         FIG. 5  is a side view drawing of an embodiment showing the use of a torsion spring and a plunger for automatic deployment and retrieval of the shutter system of the present disclosure to positively block and unblock a beam of radiation from a Radiation Emitting Device (RED). 
     
    
    
     DETAILED DESCRIPTION 
     In embodiments there is illustrated: 
     a shutter system that can block the beam of an infra-red (IR) laser from exiting the xerographic cavity of a printer especially when the machine is undocked from an operational mode and is put into a diagnostic or service mode while the beam is still on. The shutter offers a final line of defense in the event that electrical interlocks are bypassed or have failed to block radiation from raster output scanners (ROS) employed in an electrophotographic printing machine such as the Xerox iGen3® shown in  FIG. 1 . 
     The printing machine  100  shown in  FIG. 1  employs a photoconductive belt, sometimes referred to as photoreceptor belt  110  supported by a plurality of rollers or bars,  113 . Photoconductive belt  110  is arranged in a vertical orientation. Photoconductive belt  110  advances in the direction of arrow  125  to move successive portions of the external surface of photoconductive belt  110  sequentially beneath the various processing stations disposed about the path of movement thereof. The photoconductive belt  110  (and its associated module  110 ′ that holds the belt) has a major axis  120  and a minor axis  123 . The major and minor axes  120 ,  123  are perpendicular to one another. Photoconductive belt  110  is elliptically shaped. The major axis  120  is substantially parallel to the gravitational vector and arranged in a substantially vertical orientation. The minor axis  123  is substantially perpendicular to the gravitational vector and arranged in a substantially horizontal direction. The printing machine architecture includes five image recording stations indicated generally by the reference numerals  130 ,  140 ,  150 ,  160 , and  170 , respectively. Initially, photoconductive belt  110  passes through image recording station  130 . Image recording station  130  includes a charging device and an exposure device. The charging device includes a corona generator  133  that charges the exterior surface of photoconductive belt  110  to a relatively high, substantially uniform potential. After the exterior surface of photoconductive belt  110  is charged, the charged portion thereof advances to the exposure device. The exposure device includes a raster output scanner (ROS)  135 , which illuminates the charged portion of the exterior surface of photoconductive belt  110  to record a first electrostatic latent image thereon. Alternatively, a light emitting diode (LED) may be used. 
     This first electrostatic latent image is developed by developer unit  131 . Developer unit  131  deposits toner particles of a selected color on the first electrostatic latent image. After the highlight toner image has been developed on the exterior surface of photoconductive belt  110 , photoconductive belt  110  continues to advance in the direction of arrow  125  to image recording station  140 . 
     Image recording station  140  includes a recharging device and an exposure device. The charging device includes a corona generator  143  which recharges the exterior surface of photoconductive belt  110  to a relatively high, substantially uniform potential. The exposure device includes a ROS  145  which illuminates the charged portion of the exterior surface of photoconductive belt  110  selectively to record a second electrostatic latent image thereon. This second electrostatic latent image corresponds to the regions to be developed with magenta toner particles. This second electrostatic latent image is now advanced to the next successive developer unit  141 . 
     Developer unit  141  deposits magenta toner particles on the electrostatic latent image. In this way, a magenta toner powder image is formed on the exterior surface of photoconductive belt  110 . After the magenta toner powder image has been developed on the exterior surface of photoconductive belt  110 , photoconductive belt  110  continues to advance in the direction of arrow  125  to image recording station  150 . 
     Image recording station  150  includes a charging device and an exposure device. The charging device includes corona generator  153 , which recharges the photoconductive surface to a relatively high, substantially uniform potential. The exposure device includes ROS  155  which illuminates the charged portion of the exterior surface of photoconductive belt  110  to selectively dissipate the charge thereon to record a third electrostatic latent image corresponding to the regions to be developed with yellow toner particles. This third electrostatic latent image is now advanced to the next successive developer unit  153 . 
     Developer unit  153  deposits yellow toner particles on the exterior surface of photoconductive belt  110  to form a yellow toner powder image thereon. After the third electrostatic latent image has been developed with yellow toner, photoconductive belt  110  advances in the direction of arrow  125  to the next image recording station  160 . 
     Image recording station  160  includes a charging device and an exposure device. The charging device includes a corona generator  163 , which charges the exterior surface of photoconductive belt  110  to a relatively high, substantially uniform potential. The exposure device includes ROS  165 , which illuminates the charged portion of the exterior surface of photoconductive belt  110  to selectively dissipate the charge on the exterior surface of photoconductive belt  110  to record a fourth electrostatic latent image for development with cyan toner particles. After the fourth electrostatic latent image is recorded on the exterior surface of photoconductive belt  110 , photoconductive belt  110  advances this electrostatic latent image to the magenta developer unit  161 . 
     Developer unit  161  deposits cyan toner particles on the fourth electrostatic latent image. These toner particles may be partially in superimposed registration with the previously formed yellow powder image. After the cyan toner powder image is formed on the exterior surface of photoconductive belt  110 , photoconductive belt  110  advances to the next image recording station  170 . 
     Image recording station  170  includes a charging device and an exposure device. The charging device includes corona generator  173  which charges the exterior surface of photoconductive belt  110  to a relatively high, substantially uniform potential. The exposure device includes ROS  175 , which illuminates the charged portion of the exterior surface of photoconductive belt  110  to selectively discharge those portions of the charged exterior surface of photoconductive belt  110  which are to be developed with black toner particles. The fifth electrostatic latent image, to be developed with black toner particles, is advanced to black developer unit  171 . 
     At black developer unit  171 , black toner particles are deposited on the exterior surface of photoconductive belt  110 . These black toner particles form a black toner powder image which may be partially or totally in superimposed registration with the previously formed yellow and magenta toner powder images. In this way, a multi-color toner powder image is formed on the exterior surface of photoconductive belt  110 . Thereafter, photoconductive belt  110  advances the multi-color toner powder image to a transfer station, indicated generally by the reference numeral  192 . 
     At transfer station  192 , a receiving medium, i.e., paper, is advanced from stack  190  by sheet feeders and guided to transfer station  192 . At transfer station  192 , a corona generating device  191  sprays ions onto the backside of the paper. This attracts the developed multi-color toner image from the exterior surface of photoconductive belt  110  to the sheet of paper. Stripping assist roller  115  contacts the interior surface of photoconductive belt  110  and provides a sufficiently sharp bend thereat so that the beam strength of the advancing paper strips from photoconductive belt  110 . A vacuum transport moves the sheet of paper in the direction of arrow  193  to fusing station  196 . 
     Fusing station  196  includes a heated fuser roller  195  and a back-up roller  197 . The back-up roller  197  is resiliently urged into engagement with the fuser roller  195  to form a nip through which the sheet of paper passes. In the fusing operation, the toner particles coalesce with one another and bond to the sheet in image configuration, forming a multi-color image thereon. After fusing, the finished-sheet is discharged to a finishing station where the sheets are compiled and formed into sets which may be bound to one another. These sets are then advanced to a catch tray for subsequent removal therefrom by the printing machine operator. 
     After the multi-color toner powder image has been transferred to the sheet of paper, residual toner particles usually remain adhering to the exterior surface of photoconductive belt  110 . The photoconductive belt  110  moves over isolation roller  117  which isolates the cleaning operation at cleaning station  177 . At cleaning station  177 , the residual toner particles are removed from photoconductive belt  110 . Photoconductive belt  110  then moves under spots blade  179  to also remove toner particles therefrom. 
     In an embodiment of the printing machine shown in  FIG. 1 , all the components associated with recording stations  130  and  140 , including the cleaning station  177  and blades  179  to the right of the major axis  120  are housed in a unit hereafter called the right tower (RT), and the components associated with recording stations  150 ,  160  and  170 , including developer unit  141  to the left of the major axis  120  are housed in a unit hereafter called the left tower (LT). The left tower is fixed and not movable. The right tower and the photoreceptor module are both movable such that they can be floatingly docked to the left tower. The towers are shown schematically in phantom outline in  FIG. 1 . It will be apparent to those skilled in the art that the undocking of the right tower and the photoreceptor module and belt  110  provides access to the various components of the system for service and diagnostic purposes. The system also has various electrical interlocks (not shown) to assure safety from laser beams discharging from the raster output scanners  135 ,  145 ,  155 ,  165  and  175  when in the undocked position. However, they are not described in detail here in order not to unnecessarily obscure the present disclosure. Mechanical shutter systems that provide additional safety are described in detail in the embodiments disclosed below. 
     Referring now to  FIG. 2 , a partial perspective view of the printing machine of  FIG. 1  is shown with only a part of recording station  140  of the right tower (RT-not shown), and recording stations  150 ,  160  and  170  of the left tower (LT-not shown).  FIG. 2  also shows laser beams  199  that are projecting from ROS  155 ,  165  and  175 . 
     In an embodiment, laser beams  199  are blocked by mechanical shutters  200  shown in the perspective drawing of  FIG. 2  when the right tower and the photoreceptor module and belt  110  are undocked. The operation of the mechanical shutter system  200  can be better seen in  FIG. 3   a.    
     In  FIG. 3   a , laser beam  199  travels from a ROS (not shown) on the left to the right unimpeded, because mechanical shutter  200  is tucked upwards out of the way of the beam when the system is under operation. The up position is the normal position of shutter  200 . In an aspect of an embodiment, the shutter is selectably actuated to lower it down when the machine is to be serviced or readied for diagnostic testing. This is accomplished by rotating lever  203  up  205  or down  207  positions as shown by the arrows in  FIG. 3   b . In the down  207  position, laser beam  199  is truncated by the blocking action of shutter  200 . The shutter is urged upwards and held in the up position by a detent spring  210 . The spring is a flat spring that operates as an over-the-center holding device. As the shutter is rotated between the service and the run position a portion of the shutter blade pushes over the center of the detent spring  210 . The detent spring thus applies force to hold the shutter into either position once rotated past the center point. The center position is determined by a configuration having two pivot brackets that mount the shutter blade, one outboard and one inboard. The outboard position is located at outboard pivot mount  215  above the spring  210 , while the inboard position is located at  217  not shown in  FIGS. 3   a  and  3   b.    
     It will be noted that while one end  213  of the detent spring  210  is fixed at the outboard pivot mount bracket  215 , the other end  211  is free to float as it presses on the shutter blade so that it can accommodate slip and slide on the blade over a wide range of tolerances. Furthermore, because of the over-the-center cam design of the spring, lever  203  can be turned, but the shutter will only stop in the full down or full up position, and cannot be stopped positively at any angle. Manual rotation of the lever also provides a positive feedback to the operator as to whether the shutter is actually actuated or not. The shutter can be placed into service position at any time. The shutter can be used to block the ROS beam during trouble shooting without having to shut down the machine. Shutter  200  and rotating lever  203  may be machined from, but not limited to, extruded rigid PVC material. Pivot brackets  215  comprise, but not limited to, standard steel, and detent spring  210  comprises standard spring materials. 
     Another embodiment involves a semi-automatic mechanical ROS shutter system shown in  FIGS. 4   a  and  4   b , where similar numerals refer to similar parts. Shutter  200  is actuated by a cable assembly  220  to block the beam  199 . In figure a, shutter  200  is in the up position, leaving the laser beam  199  unblocked and, therefore, in operational mode as was the case in  FIG. 3   a . In  FIG. 4   a , however, cable  220  is attached, for purposes of illustration here, to the corona generator or charge unit  173  of  FIG. 1 . Since the charge unit mount (represented by reference numeral  230  in  FIGS. 4   a  and  4   b)  remains stationary during undocking, the charge unit will move to the right a short distance as the right tower and the photoreceptor are undocked. This movement pulls cable  220 , which in turn rotates the shaft  201  of which lever  203  is a part, thereby causing shutter blade  200  to move clockwise downwardly to block the laser beam  199 , as shown in  FIG. 5   b . This action puts the machine in service mode to service the machine in real time with no shut down without any concern for exposure to radiation from the laser. After service, the photoconductive belt  110  may be docked against the tower (shown in  FIG. 1 ) while at the same time relieving the tension in cable  220 . Since shaft  201  is no longer restrained by cable  220 , the operator or a service technician can selectably rotate lever  203  to up  205  position to unblock beam  199  and proceed with the normal operation of the printing machine. In an aspect, it will be appreciated by those skilled in the art that the turn around time for service is substantially improved in comparison with current state of the art methods where the machine may be first shut down and then turned back on to avoid accidental exposure to harmful radiation. 
     In still another embodiment, a fully automatic mechanical ROS shutter system involves a preloaded torsion spring.  FIG. 5  shows a portion (inverted for clarity) of the printing machine of  FIGS. 1 and 2  in order to illustrate the parts of an automatic shutter system where ROS is not shown so as to not unnecessarily complicate the drawing. Recording station, say  150  in  FIG. 1 , is shown in an undocked state or service position in  FIG. 5  where the laser beam (not shown) is blocked by shutter  200 . The shutter is held in this “up” position (see  FIGS. 3   b  and  4   b ) by means of a preloaded torsion spring  240  applying a counter clockwise rotational force to the shutter (blade)  200 . The shutter is mounted between two pivot brackets providing pivot points  243  and  245 . The shovel blade presses against a “thrust finger”  250  with a rotational force provided by torsion spring  240 . The thrust finger is in its normal or home position as shown in  FIG. 5 . Actuation of the shutter begins as the right tower (RT) and the photoreceptor module move to their operational position. That is, for this illustration, the tower on the right and the photoreceptor module move from right to left. Actuation of the shutter starts as a portion of the photoreceptor module approaching from the right makes contact with a plunger  260 . Plunger  260  is attached to a portion  265  of the charge unit  150 , as shown in  FIG. 5 . A further movement of the tower causes the plunger  260  to contact an extension of actuator arm  270 . As a result, the arm  270  begins to rotate about pivot point  250  causing the thrust finger  250  to rotate clockwise about pivot point  275 . A clockwise motion by the thrust finger also imparts a clockwise rotation on the shutter  200 . The force provided by the thrust finger overcomes the preloaded torsion spring and since the thrust finger is proximate to the shutter pivot point, only a relatively weak force is required to rotate the shutter blade clockwise to rest against the wall  152  of the charge unit  150 . In one aspect, the shutter reaches the wall prior to the thrust finger reaches its final resting position. Consequently, the finger continues moving against a stationary shutter, hence stretching further and straightening out in a wiping motion over the surface of the shutter blade. Once the tower floatingly docks against the photoreceptor module, the shutter positively rests on the wall  152  of the recording station  150 , thus unblocking the laser beam and setting the machine in operational or run mode. During undocking, the process is reversed, allowing the shutter to return to the service or diagnostic mode and block the laser beam from causing any unintended damage. It will be understood that a fully automatic shutter systems shortens machine downtime even further as no manual intervention is required in deploying the shutter either in docking or undocking operations. 
     It will be appreciated that variations of the above-disclosed embodiments and other features and functions, or alternatives thereof, may be desirably combined into many other different devices or applications. For example, the shutter systems disclosed above may be used for blocking radiation from a radiation emitting device (RED) in general with or without practicing all the details disclosed herein. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.