Reproduction machine having a safe tiltable paper tray

Information

  • Patent Grant
  • 6460846
  • Patent Number
    6,460,846
  • Date Filed
    Monday, December 18, 2000
    24 years ago
  • Date Issued
    Tuesday, October 8, 2002
    22 years ago
Abstract
A safe tiltable sheet feeding apparatus including a tiltable sheet support tray having a lead edge and a trail edge, for supporting a stack of sheets to be fed lead edge first from the stack. The tiltable sheet feeding apparatus also includes a feed head adjacent the sheet support tray for feeding a top sheet of the stack from the stack and an elevator assembly for independently raising, lowering and tilting the trail edge of the sheet support tray. The elevator assembly includes elevator drive motors, a controller, side frames defining lead edge elevator slots, and trail edge elevator slots. Importantly, the tiltable sheet feeding apparatus includes an overtilt safety sensor device mounted within the trail edge elevator slots and connected to the controller, for sensing overtilt of the trail edge of the sheet support tray, and for preventing resulting damage to the tiltable sheet feeding apparatus.
Description




BACKGROUND OF THE INVENTION




This invention relates generally to toner image reproduction machines, and more particularly to such a machine including a high capacity feeder having a safe tiltable paper tray.




In a typical toner image reproduction machine, for example an electrostatographic printing process machine, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document.




After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are heated to permanently affix the powder image to the copy sheet.




The foregoing generally describes a typical black and white electrostatographic printing machine. With the advent of multicolor electrophotography, it is desirable to use an architecture which comprises a plurality of image forming stations. One example of the plural image forming station architecture utilizes an image-on-image (IOI) system in which the photoreceptive member is recharged, re-imaged and developed for each color separation. This charging, imaging, developing and recharging, re-imaging and developing, all followed by transfer to paper, is done in a single revolution of the photoreceptor in so-called single pass machines, while multi-pass architectures form each color separation with a single charge, image and develop, with separate transfer operations for each color.




In single pass color machines and other high-speed printers it is desirable to feed a wide variety of media for printing thereon. A large variety or latitude of sheet sizes and sheet weights, in addition to various coated and other specialty papers must be fed at high speed to the printer by sheet feeding apparatus that may involve tray tilting.




In the event of a system failure severe damage to the entire system is likely to occur unless the tray tilting drives are stopped.




SUMMARY OF THE INVENTION




In accordance with the present invention, there is provided a safe tiltable sheet feeding apparatus that includes a tiltable sheet support tray, having a lead edge and a trail edge, for supporting a stack of sheets to be fed lead edge first from the stack. The tiltable sheet feeding apparatus also includes a feed head adjacent the sheet support tray for feeding a top sheet of the stack from the stack and an elevator assembly for independently raising, lowering and tilting the trail edge of the sheet support tray. The elevator assembly includes elevator drive motors, a controller, side frames defining lead edge elevator slots, and trail edge elevator slots. Importantly, the tiltable sheet feeding apparatus includes an overtilt safety sensor device mounted within the trail edge elevator slots and connected to the controller, for sensing overtilt of the trail edge of the sheet support tray, and for preventing resulting damage to the tiltable sheet feeding apparatus











BRIEF DESCRIPTION OF THE DRAWING




Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings, in which:





FIG. 1

is a schematic elevational view of a full color image-on-image single-pass electrostatographic printing machine including the safe tiltable sheet stack support and paper supply tray in accordance with the present invention;





FIG. 2

is a side view illustrating the safe tiltable sheet stack support and paper supply tray in accordance with the present invention;





FIG. 3

is a detailed side view of the elevator drives for the safe tiltable sheet stack support and paper supply tray in accordance with the present invention;





FIG. 4

is a plan view of a portion of the membrane sensor device of the safe tiltable sheet stack support and paper supply tray in accordance with the present invention; and





FIG. 5

is a sectional view (along view plane


5





5



FIG. 4

) of the portion of the membrane sensor device in accordance with the present invention.











DETAILED DESCRIPTION OF THE INVENTION




Turning now to

FIG. 1

, the printing machine of the present invention uses a charge retentive surface in the form of an Active Matrix (AMAT) photoreceptor belt


10


supported for movement in the direction indicated by arrow


12


, for advancing sequentially through the various xerographic process stations. The belt is entrained about a drive roller


14


, tension rollers


16


and fixed roller


18


and the roller


14


is operatively connected to a drive motor


20


for effecting movement of the belt through the xerographic stations.




With continued reference to

FIG. 1

, a portion of belt


10


passes through charging station A where a corona generating device, indicated generally by the reference numeral


22


, charges the photoconductive surface of belt


10


to a relatively high, substantially uniform, preferably negative potential.




Next, the charged portion of photoconductive surface is advanced through an imaging/exposure station B. At imaging/exposure station B, a controller


90


receives the image signals representing the desired output image and processes these signals to convert them to the various color separations of the image to be reproduced. The color separations are then transmitted to a laser based output scanning device


24


causing the charge retentive surface to be discharged in accordance with the output from the scanning device. Preferably the scanning device is a laser Raster Output Scanner (ROS). Alternatively, the ROS could be replaced by other xerographic exposure devices such as LED arrays.




The photoreceptor, which is initially charged to a voltage V


0


, undergoes dark decay to a level V


ddp


equal to about −500 volts. When exposed at the exposure station B it is discharged to V


expose


equal to about −50 volts. Thus after exposure, the photoreceptor contains a monopolar voltage profile of high and low voltages, the former corresponding to charged areas and the latter corresponding to discharged or background areas.




At a first development station C, developer structure, indicated generally by the reference numeral


32


utilizing a hybrid jumping development (HJD) system, the development roll, better known as the donor roll, is powered by two development fields (potentials across an air gap). The first field is the ac jumping field which is used for toner cloud generation. The second field is the dc development field which is used to control the amount of developed toner mass on the photoreceptor. The toner cloud causes charged toner particles


26


to be attracted to the electrostatic latent image. Appropriate developer biasing is accomplished via a power supply. This type of system is a noncontact type in which only toner particles (black, for example) are attracted to the latent image and there is no mechanical contact between the photoreceptor and a toner delivery device to disturb a previously developed, but unfixed, image.




The developed but unfixed image is then transported past a second charging device


36


where the photoreceptor and previously developed toner image areas are recharged to a predetermined level.




A second exposure/imaging is performed by device


24


which comprises a laser based output structure is utilized for selectively discharging the photoreceptor on toned areas and/or bare areas, pursuant to the image to be developed with the second color toner. At this point, the photoreceptor contains toned and untoned areas at relatively high voltage levels and toned and untoned areas at relatively low voltage levels. These low voltage areas represent image areas which are developed using discharged area development (DAD). To this end, a negatively charged, developer material


40


comprising color toner is employed. The toner, which by way of example may be yellow, is contained in a developer housing structure


42


disposed at a second developer station D and is presented to the latent images on the photoreceptor by way of a second HSD developer system. A power supply (not shown) serves to electrically bias the developer structure to a level effective to develop the discharged image areas with negatively charged yellow toner particles


40


.




The above procedure is repeated for a third image for a third suitable color toner such as magenta and for a fourth image and suitable color toner such as cyan. The exposure control scheme described below may be utilized for these subsequent imaging steps. In this manner a full color composite toner image is developed on the photoreceptor belt.




Since some toner charge may not be totally neutralized, or the polarity thereof may be reversed, (thereby causing the composite image developed on the photoreceptor to consist of both positive and negative toner), a negative pre-transfer dicorotron member


50


is provided for conditioning the composite image in order to facilitate its effective transfer to a substrate.




Subsequent to image development a sheet of support material


52


is moved into contact with the toner images at transfer station G. The sheet of support material is advanced to transfer station G by the sheet feeding apparatus of the present invention, described in detail below. The sheet of support material is then brought into contact with photoconductive surface of belt


10


in a timed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station G.




Transfer station G includes a transfer dicorotron


54


which sprays positive ions onto the backside of sheet


52


. This attracts the negatively charged toner powder images from the belt


10


to sheet


52


. A detack dicorotron


56


is provided for facilitating stripping of the sheets from the belt


10


.




After transfer, the sheet continues to move, in the direction of arrow


58


, onto a conveyor (not shown) which advances the sheet to fusing station H. Fusing station H includes a fuser assembly, indicated generally by the reference numeral


60


, which permanently affixes the transferred powder image to sheet


52


. Preferably, fuser assembly


60


comprises a heated fuser roller


62


and a backup or pressure roller


64


. Sheet


52


passes between fuser roller


62


and backup roller


64


with the toner powder image contacting fuser roller


62


. In this manner, the toner powder images are permanently affixed to sheet


52


. After fusing, a chute, not shown, guides the advancing sheets


52


to a catch tray, stacker, finisher or other output device (not shown), for subsequent removal from the printing machine by the operator.




After the sheet of support material is separated from photoconductive surface of belt


10


, the residual toner particles carried by the non-image areas on the photoconductive surface are removed therefrom. These particles are removed at cleaning station I using a cleaning brush or plural brush structure contained in a housing


66


. The cleaning brush


68


or brushes


68


are engaged after the composite toner image is transferred to a sheet. Once the photoreceptor is cleaned the brushes are retracted utilizing a device.




It is desirable in high speed color printers such as those described above to be able to feed a wide variety of sheet types for various printing jobs. Customers demand multiple sized stock, a wide range of paper weights, paper appearance characteristics ranging from rough flat appearing sheets to very high gloss coated paper stock. Each of these sheet types and size has its own unique characteristics and in many instances very different problems associated therewith to accomplish high speed feeding.




There is shown schematically in

FIG. 2

, a side elevational view of the safe tiltable paper tray or feeder of the present invention, generally indicated by reference numeral


200


. As shown, the safe tiltable paper tray or feeder


200


includes a sheet support tray


210


which is tiltable and self adjusting to in order to accommodate various sheet types and characteristics; multiple tray elevator slots


220


,


230


defined by side frames


219


(only one of which is shown), and elevator drives


222


,


232


for raising, lowering and tilting a stack


53


of sheets supported on the tray


210


; a vacuum shuttle feedhead


300


; a lead edge multiple range sheet height sensor


340


; a multiple position stack height sensor


350


; a variable acceleration take away roll (TAR)


400


; sheet fluffers


360


, and an overtilt safety sensor device


600


of the present invention.




Turning to

FIG. 3

, there is illustrated the general configuration of a multi-position stack height (contact) sensor (can detect


2


or more specific stack heights) in conjunction with a second sensor


340


near the stack lead edge which also senses distance to the top sheet (without sheet contact). The two sensors together enable the paper supply to position the stack


53


with respect to the acquisition surface


302


both vertically and angularly in the process direction. This height and attitude control greatly improves the capability of the feeder to cope with a wide range of paper basis weight, type, and curl.




Proper feeding with a top vacuum corrugation feeder (VCF) feedhead


300


requires correct distance control of the top sheets in the stack


53


from the acquisition surface and fluffer jets


360


. The acquisition surface


302


is the functional surface on the feed head


300


or vacuum plenum.




Proper stack orientation requires the tray


210


to be tilted with the stack leading edge


152


being higher or lower than the stack trailing edge


153


thereof depending on whether there is down-curl or up-curl in the sheets in the stack


53


thereon. This tilting of the tray


210


brings the leading edge


152


of the top sheets of the stack


53


into proper location relative to the acquisition surface


302


of the feed head


300


and the fluffing jets. In order to institute the corrective tilting action, the height of the top sheet


52


near its leading edge


152


must be sensed, relative to the feed head


300


, prior to acquisition and with the air system on and the stack “fluffed”.




As seen in

FIGS. 2-3

, in the safe tiltable paper tray or feeder


200


, the lead edge


212


and trail edge


213


of the support tray


210


are independently controlled by elevator drives


232


,


222


respectively, which operate to raise, lower and/or tilt each such edge


212


,


213


. As illustrated, an elevator assembly (which include cross shafts


217


and


218


,

FIG. 3

, and a belt not shown) are mounted for movement up and down through elevator slots


220


,


230


. The elevator assembly as such is driven by means of the two motors


222


,


232


for independently controlling and tilting the LE


212


, and TE


213


of the support tray


210


. By tilting the tray


210


at an incline/upcline or decline/downcline respectively, the elevator drives


222


,


232


can effectively compensate for severe up-curl/down-curl in the sheets on the stack. Tilting the tray in the manner illustrated also significantly reduces the number of multi-feeds for light weight media, and decreases the acquisition time for heavy weight papers.




The support tray


210


is initially tilted up on the lead edge


212


side, approximately 1.4° when paper is loaded. The initial angle is set at the maximum allowable angle while still maintaining stack capacity. If the paper was loaded in a flat tray and the tray


210


had to compensate for downcurl, the LE would be tilted up. By tilting up after the paper is loaded, the LE


152


of the stack


53


will be pulled away from the LE registration wall


214


. Therefore, it is necessary to have an initial degree of tilt in the tray


210


. By using a combination of sensors in the feedhead to detect proximity of the sheet stack, which can reflect the curl, the elevator is sent a signal to compensate for curl. Depending on the state of curl the elevator will tilt up/down for downcurl/upcurl, respectively. Tilting up to compensate for down curl will be limited to a maximum to prevent a large gap between the LE


152


of the paper and the LE registration wall


214


.




Referring now to

FIGS. 2-5

, the pivot point


216


of the support tray


210


is located at the lead edge


212


thereof. A bearing (not shown) mounted on a lead edge cross shaft


217


which supports the tray


210


, is located within an opening


234


in the tray


210


, and within the lead edge elevator slot


230


as defined by side frames


219


. The trail edge


213


of the support tray


210


has a trail edge cross shaft


218


that moves with the trail edge


213


, and both are not constrained. Thus the trail edge


213


, and trail edge shaft


218


are free to tilt or move pivotably up and down from a center position CP to an allowed lower limit position LL or to an allowed upper limit position UL within the trail edge elevator slot


220


defined by side frames


219


(only one of which is shown).




Thus as shown above, the tiltable paper tray or feeder


200


uses two stepper motors


222


,


232


in an open loop


226


,


236


with the controller


90


to control the attitude of the sheet stack support tray


210


. In the event of a system failure, for example, where one of the motors


222


,


232


stalls and the other continues to drive, severe damage to the entire system is likely to occur unless the other motor is stopped. Since no feedback is available in the open loop


226


,


236


of the motors and controller, a cost effective and environmentally safe means is necessary for determining and counteracting support tray overtilt. A mercury switch could be used, however, a mercury switch poses an environmental problem, as well as being twenty times more expensive than using the preferred embodiment of a membrane sensor for the overtilt safety sensor device


600


of the present invention.




During tilting movements of the support tray


210


, the trail edge motor


222


for example will index to a certain position and then the lead edge motor


232


will index either up or down in order to compensate for sheet curl as described above. All of this is of course accomplished through software and programming of the controller


90


. If however there is any failure in the control system of either of the motors


222


,


232


, it is more than likely that severe hardware damage will result if the support tray


210


is allowed to overtilt or tilt too far out of specification. Therefore, in accordance with the present invention, an overtilt safety sensor device, preferably in the form of a membrane sensor,


600


is provided and located at strategic and desired positions for preventing such undesirable support tray overtilt.




As shown, the overtilt safety sensor device or membrane sensor


600


is mounted within the trail edge elevator slot


220


, defined by side frames


219


, and strategically where the trail edge cross shaft


218


(at the trail edge


213


of the support tray


210


) will make contact therewith when at the allowed lower limit LL, or at the allowed upper limit UL, when being tilted as above. As the support tray


210


tilts in the LE-TE direction, the trail edge shaft


218


is pulled closer to the lead side


221


of the trial edge elevator slot


220


. If the trail edge shaft


218


is pulled too close to the lead side


221


of the trail edge elevator slot


220


, the membrane sensor device


600


will be actuated, and will send an output signal along means


610


to the controller


90


. The controller


90


then declares a system fault and takes appropriate action, thereby preventing serious damage to the paper supply subsystem.




For example, if the support tray


210


overtilts either up or down, its trail edge


213


, specifically the trail edge shaft


218


, will contact and actuate the overtilt safety sensor device


600


, and for example, cause the sensor device


600


to send out a signal


610


that enables the controller


90


to cut power to the elevator motors


222


,


232


, thus preventing severe hardware damage and failure. As such, the overtilt safety sensor device


600


provides a cost effective and environmentally safe way for preventing the support tray


210


from tilting out of specification if there is a system failure.




Referring now to

FIGS. 4 and 5

, an exemplary embodiment of a membrane or pressure sensor device


600


is shown and is suitable for use as the overtilt safety sensor in accordance with the invention. As illustrated, the pressure sensor


600


as shown includes a conductive sensor membrane


612


spaced from a sensing assembly


614


by a spacer layer


628


. The sensing assembly


614


includes an electrode substrate


616


having an electrode surface


618


and an electrode set


622


including a plurality of electrodes


620


. The pressure sensor


600


also includes a sensing area


634


. Each of the electrodes


620


is connected by means


610


to a signal processor, such as the controller


90


as shown in FIG.


1


. As shown in

FIG. 5

, the electrode substrate


616


and the spacer layer


628


may be integrally formed.




Each of the plurality of electrodes


620


in the pressure sensor


600


may be, and preferably are linearly arranged parallel to each other. As pressure is applied to the sensor membrane


612


to deform the sensor membrane


612


toward the linear electrodes


620


, the sensor membrane


612


will make both mechanical and electrical contact with selected ones of the electrodes


620


. The specific ones of the electrodes


620


contacted by the sensor membrane


612


will depend on the particular point LL, UL, (

FIGS. 2 and 3

) at which the pressure is applied to the sensor membrane


612


.




Since the electrodes


620


are connected (


610


) to the signal processor or controller


90


, when any of the electrodes


620


are contacted by the sensor membrane


612


this condition may be sensed by the controller


90


, which then outputs an appropriate output signal indicative of this condition.




Ordinarily, the sensor membrane


612


will be in an undeformed rest position when no pressure is applied to the sensor membrane


612


. The sensor membrane


612


is shown in such a rest position in FIG.


5


. Due to the resilient nature of the sensor membrane


612


, and to the manner in which the sensor membrane


612


is supported by the spacer layer


628


, as pressure is gradually applied to the sensor membrane


612


, the first electrode to be contacted will be the center electrode


624


.




As can be seen, there has been provided a safe tiltable sheet feeding apparatus is provided and includes a tiltable sheet support tray having a lead edge and a trail edge, for supporting a stack of sheets to be fed lead edge first from the stack. The tiltable sheet feeding apparatus also includes a feed head adjacent the sheet support tray for feeding a top sheet of the stack from the stack and an elevator assembly for independently raising, lowering and tilting the trail edge of the sheet support tray. The elevator assembly includes elevator drive motors, a controller, side frames defining lead edge elevator slots, and trail edge elevator slots. Importantly, the tiltable sheet feeding apparatus includes an overtilt safety sensor device mounted within the trail edge elevator slots and connected to the controller, for sensing overtilt of the trail edge of the sheet support tray, and for preventing resulting damage to the tiltable sheet feeding apparatus.




While the present invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.



Claims
  • 1. A safe tiltable sheet feeding apparatus comprising:(a) a tiltable sheet support tray for supporting a stack of sheets to be fed lead edge first from the stack, said tiltable sheet support tray having a lead edge and a trail edge; (b) a feed head adjacent said sheet support tray for feeding a top sheet of the stack from the stack; (c) an elevator assembly for independently raising, lowering and tilting said trail edge of said sheet support tray, said elevator assembly including elevator drive motors, a controller, side frames defining lead edge elevator slots, and trail edge elevator slots; and (d) an overtilt safety sensor device mounted within said trail edge elevator slots and connected to said controller, for sensing overtilt of said trail edge of said sheet support tray, and for preventing resulting damage to the tiltable sheet feeding apparatus.
  • 2. The safe tiltable sheet feeding apparatus of claim 1, wherein said sheet support tray includes a lead edge support shaft forming a pivot for tilting movement of said sheet support tray.
  • 3. The safe tiltable sheet feeding apparatus of claim 2, wherein said lead edge support shaft is mounted within said side frames defining lead edge elevator slots.
  • 4. The safe tiltable sheet feeding apparatus of claim 1, wherein said elevator assembly includes a lead edge elevator drive motor and a trail edge elevator drive motor.
  • 5. The safe tiltable sheet feeding apparatus of claim 1, wherein said overtilt safety sensor device comprises a membrane sensor device.
  • 6. The safe tiltable sheet feeding apparatus of claim 5, wherein said membrane sensor device comprises a conductive membrane, a spacer layer and an electrode substrate including a plurality of electrodes connected to said controller.
  • 7. An electrostatographic reproduction machine for producing toner images on copy sheets, the electrostatographic reproduction machine comprising:(a) a moveable image bearing member having an image bearing surface; (b) means for forming a toner image on said image bearing surface and for transferring said toner image onto a copy sheet of paper; and (c) a safe tiltable sheet feeding apparatus for holding and feeding copy sheets to receive said toner image, said safe tiltable sheet feeding apparatus including: (i) a tiltable sheet support tray for supporting a stack of sheets to be fed lead edge first from the stack into toner image receiving relationship with said image bearing member, said tiltable sheet support tray having a lead edge and a trail edge; (ii) a feed head adjacent said sheet support tray for feeding a top sheet of the stack from the stack; (iii) an elevator assembly for independently raising, lowering and tilting said trail edge of said sheet support tray, said elevator assembly including elevator drive motors, a controller, side frames defining lead edge elevator slots and trail edge elevator slots; and (iv) an overtilt safety sensor device mounted within said trail edge elevator slots and connected to said controller, for sensing overtilt of said trail edge of said sheet support tray, and for preventing resulting damage to the tiltable sheet feeding apparatus.
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