Patent Publication Number: US-6991392-B2

Title: Door assembly having a print media delivery system

Description:
BACKGROUND 
     The present application relates to a door assembly having a print media delivery system. More particularly, the present application relates to a simplified door assembly with a print media delivery system that is pivotally connected to an associated frame such as found on a printing device and will be described with particular reference thereto. However, it is to be appreciated that the door assembly may be used in other similar environments and applications. 
     Missing teeth gear applications are frequently used in gear drive trains on printing devices. They commonly consist of a gear with a section of its teeth missing, a biased spring and a solenoid with a pawl to hold the gear in the missing teeth section. Missing teeth gear applications are common because they are an inexpensive way to implement adding another function to a gear drive train without having to add another expensive motor or an electric clutch with a position sensor. They are ideal for use in applications where only a single revolution is needed. 
     In printers, missing tooth gear systems are known to be used on multipurpose tray D-roller pick systems which are often provided on an openable door structure of the printer device to allow access into the printer device, as might be necessary to remove a jammed sheet of print media. However, in many (if not all) prior art implementations, the components of the D-roller pick system, i.e., the pick roller, missing tooth gear, solenoid and bias spring, are all housed in the same structure, the openable front door. When housed in the openable front door, the manufacturing costs of the printer device may be unnecessarily high and the likelihood of cable routing problems and safety issues may increase. When solenoids are required in an openable front door, longer cables are often required that may require special insulation which further increases costs. Thus, there is a need for a pick system that is relatively inexpensive and simple and can be used in areas of a printer device that render housing of all components in one structure impractical due to excessive costs or other problems. 
     BRIEF SUMMARY 
     A print media delivery system on a door assembly that is connected to an associated frame is provided. The door assembly includes a door body openable to provide access into an associated frame. A tray is pivotally connected to the door body for receiving associated print media thereon. A pick roller is rotatably mounted to the door body for contacting the associated print media and advancing the associated print media into the associated frame. A gear has a missing teeth section and is connected to the pick roller for corotation therewith. A gear bias system urges the gear to rotate in a first direction when the door body is closed and said tray is open to selectively advance the missing teeth section past an associated drive gear and allow teeth of the gear to engage the associated drive gear when the door body is closed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printer device having a door assembly; 
         FIG. 2  is a cross-sectional view of the printer device of  FIG. 1  showing a multipurpose tray of the door assembly in a tray open position; 
         FIG. 3  is an enlarged partial cross-sectional view of the printer device of  FIG. 1 ; 
         FIG. 4  is a partial perspective view of the door assembly of  FIG. 1  showing a pick roller shaft having a cam and a pick roller and showing a lift plate of the multipurpose tray having a cam follower; 
         FIG. 5  is a partial perspective view of the lift plate and the pick roller shaft shown with most components of the printer device removed to reveal lift plate springs; 
         FIG. 6  is a partial perspective view of the lift plate and the pick roller shaft having a missing teeth gear adjacent an associated drive gear shown with most components of the printer device removed; 
         FIG. 7  is an elevational view of the pick roller, the lift plate and a friction pad mounted to the frame of the printer device; 
         FIG. 8  is a side elevational schematic view of a missing teeth gear, a drive gear and a solenoid actuated latch pawl; 
         FIG. 9  is a partial perspective view of the missing teeth gear showing a resilient arm formed on the missing teeth gear engaged in a notch defined in a notch structure of the door assembly; 
         FIG. 10  is an elevational view of the missing teeth gear and the solenoid actuated latch pawl showing a tooth on a rib of the missing teeth gear, a rolled armature distal end, and pads on the solenoid; and 
         FIG. 11  is a graph comparing a conventional cam profile to a cam profile according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating one embodiment and not for purposes of limiting the same, with reference to  FIGS. 1 and 2 , a printer device is shown and generally designated by reference numeral  10 . As will be described in more detail below, the printer device  10  includes a door assembly  12  having a door body  14  that is pivotally connected to a frame  16  of the printer device  10 . The door body  14  is moveable relative to the frame  16  between a door closed position and a door open position for providing access into the frame  16  such as might be necessary to clear a jam in the printer device or for servicing one or more internal components of the printer device. 
     A print media delivery system  18  is provided on the door assembly  12  for receiving a relatively small stack of print media sheets, such as various grades and sizes of paper, transparencies, other print media or the like, and for separating and sequentially feeding individual print media sheets from the stack into the printer device  10  for further processing and/or printing on the fed sheets. More particularly, the print media delivery system  18  is disposed on the door body  14  or formed in conjunction therewith and, with additional reference to  FIG. 3 , includes a multipurpose tray  20  that is pivotally connected to the door body  14 . The tray  20  is moveable relative to the door body  14  between a tray closed position (shown in  FIG. 1 ) and a tray open position (shown in  FIGS. 2 and 3 ). In the tray open position, the tray  20  is able to receive print media sheets thereon in a conventional manner for delivering the media sheets into the printer device  10 . 
     With additional reference to  FIG. 4 , the delivery system  18  further includes a pick roller shaft  22  rotatably mounted or connected to the door body  14  adjacent the tray  20 . A pick roller  24  is also rotatably mounted or connected to the door body  14 . More specifically, the pick roller  24  is rotatably fixed to the pick roller shaft  22  for corotation therewith. The pick roller  24  is positioned to selectively contact the top one of any number of print media sheets held in the tray  20  and to advance the top of the contacted sheets into the frame  16  for further print processing. Spaced apart from the pick roller  24 , with reference to  FIGS. 4 and 5 , first and second cams  26 , 28  are rotatably fixed on or to the pick roller shaft  22 , also for corotation with the pick roller shaft  22 . 
     The tray  20  includes a lift plate  30  that operates to lift print media sheets held in the tray  20  toward and/or into contact with the pick roller  24 . More particularly, the lift plate  30  is moveable between a lowered positioned wherein print media sheets held in the tray  20  are allowed to be spaced from the pick roller  24  which facilitates relatively easier loading of the print media sheets into the tray  20  and a raised position wherein the sheets are urged into or toward the pick roller  24 . As will be discussed in more detail below, the tray  20  includes first and second cam followers  36 , 38  positioned to engage the cams  26 , 28  of the pick roller shaft  22  and selectively move the lift plate  30  between the lowered and raised positions. 
     The tray  20  further includes a separator or friction pad  40  positioned to be adjacent the pick roller  24  at least when the tray  20  is in the tray open position and the door body  14  is in the door closed position. When the pick roller  24  is in the appropriate position, a D-shaped section  42  of the pick roller  24  and the separator pad  40  together form a nip for receiving and feeding a single sheet of print media into the printer device  10  while retarding all sheets other than the top single sheet. More particularly, with additional reference to  FIG. 7 , the separator pad  40  forms a nip with a rounded portion  44  of the D-shaped pick roller section  42  when adjacent the rounded portion  44 . A gap is formed between the D-shaped pick roller section  42  and the pad  40  when a flat portion  46  of the D-shaped section  42  is adjacent or aligned with the pad  40 . 
     With continued reference to  FIG. 7 , the D-shaped pick roller section  42  is particularly suitable for paper picking, i.e., removing and advancing only a top sheet from a stack of print media, because only a single revolution is needed from the D-shaped section  42 . The D-shaped section  42  is in a pick roller home position (shown in  FIG. 7 ) when the flat portion  46  is aligned or positioned adjacent the separator pad  40 . To pick a sheet of print media, the pick roller  24  is rotated in a first direction (counterclockwise in  FIG. 7 ) so that the rounded portion  44  can contact the top sheet of print media as the lift plate  30  moves toward the raised position. The rounded portion  44  advances the top contacted sheet into the printer device  10  for further processing. Typically, when the pick roller  24  has made a complete revolution, the advanced sheet of print media will be in contact with an upstream set of rollers (not shown). As will be discussed in further detail below, once the D-shaped section  42  has made a complete revolution and has returned to the home position, the D-shaped section  42  will stop moving in the first direction. An idler wheel section  48  of the pick roller  24 , which flanks each side of the D-shaped section  42 , will continue to rotate as the picked sheet of media is advanced into the printer device. The idler wheel section  48  is able to freely rotate on the pick roller shaft  22  and continue to contact the print media sheet, lift plate  30  and/or the separator pad  40 . 
     With reference to  FIG. 6 , a pick roller gear  54  is rotatably fixed or mounted to the pick roller shaft  22 . The pick roller gear  54  includes a missing teeth section  56  that is aligned with a drive gear  58  of the printer device  10  when the pick roller gear is in a gear home position. The pick roller gear  54  is angularly oriented on the pick roller shaft  22  relative to the D-shaped pick roller section  42  such that the gear  54  is in the gear home position when the D-shaped pick roller section is in the pick roller home position. The drive gear  58  is powered through conventional means, such as an electric motor, and is able to rotate the pick roller gear  54  when teeth  60  of the drive gear  58  mesh with teeth  62  of the pick roller gear  54 , i.e., when the pick roller gear  54  is not in the gear home position. With additional reference to  FIGS. 8 and 10 , the pick roller gear  54  includes a rib  64  having a tooth  66  adjacent an outer radial end thereof. 
     With continued reference to  FIGS. 8 and 10 , the print media delivery system  18  further includes a stopping mechanism or means for maintaining the pick roller gear  54  and the pick roller section  42  in their respective home positions. In the illustrated embodiment, the stopping means includes a clutch mechanism  70  that selectively locks the pick roller gear  54  in the gear home position. More specifically, the clutch mechanism  70  includes a solenoid  72  mounted to the frame  16  and including a pawl or armature  74  that extends toward the pick roller gear  54 . The pawl  74  is movable between a first pawl position (shown in  FIGS. 8 and 10 ) wherein the pawl  74  is positioned to engage the rib  64  of the pick roller gear  54  when in the gear home position and a second pawl position wherein the pawl  74  is spaced from the gear  54  and does not obstruct rotation of the gear  54 . A distal end  76  of the pawl  74  is rolled in the illustrated embodiment to reduce the likelihood of the pawl  74  catching on the rib  64  when the pawl is selectively moved from the pawl first position to the pawl second position whereas the tooth  66  of the rib  64  prevents the rolled end  76  from slipping off the rib  64  prior to selective movement of the pawl. The solenoid  72  optionally includes pads  78  that engage the pawl  74  when moved from the first position to the second position to reduce any noise associated with the pawl moving into the second position. The pads can be made of a resilient or cushioning material such as Poron®, other microporous polyurethane foams or the like. 
     With reference to  FIGS. 5–8 , the print media and delivery system  18  also includes a gear bias system  80  that urges the pick roller gear  54  to rotate in the first direction (counterclockwise in  FIG. 6 ; clockwise in  FIG. 8 ) when the door body  14  is in the door closed position and the tray  20  is in the tray open position. The urging of the pick roller gear  54  in the first direction is selectively used to advance the missing teeth section  56  past the drive gear  58  to allow the teeth  60  of the pick roller gear  54  to mesh with and engage the teeth  62  of the drive gear  58 . The gear bias system  80  includes a bias mechanism or means, which in the illustrated embodiment is a pair of springs: first spring  82  and second spring  84 ; the clutch mechanism  70  including the selectively movable armature or pawl  74 ; the cams  26 , 28 ; and the cam followers  36 , 38  of the lift plate  30 . 
     More specifically, with specific reference to  FIG. 5 , the first and second springs  82 , 84  extend between the lift plate  30  and the door body  14 . The springs  82 , 84  urge the cam followers  36 , 38  against or into the cams  26 , 28 . The profile of the cams  26 , 28  and the orientation of the cam followers  36 , 38  relative to the cams urge the shaft  22  and the gear  54  fixed thereon to rotate in the first direction when the missing teeth section  56  is aligned with the drive gear  58 . The springs  82 , 84  maintain engagement between the cams  26 , 28  and the cam followers  36 , 38  and also urge the lift plate  30  toward the raised position when the tray  20  is in the tray open position. The cams  26 , 28  maintain the lift plate  30  in the lower position when the gear  54  is in the home position but allow the urging of the lift plate  30  toward the raised position to move the lift plate into the raised position as the gear  54  is rotated which raises any print media sheets on the lift plate  30  toward the pick roller  24 . Thus, the force exerted by the springs  82 , 84  acts through the engagement between the cams  26 , 28  and the cam followers  36 , 38 . In the illustrated embodiment, the forces exerted by the springs  82 , 84  are the only forces urging the shaft  22  to rotate in the first direction. 
     More specifically, the cams  26 , 28  have profiles that covert the force exerted by the springs  82 , 84  to provide a moment to rotate the pick roller  24 . With additional reference to  FIG. 11 , in a conventional cam, there is often a flat area or an area of a substantially constant radius A. When the pick roller  24  is in the home position, with a conventional cam profile, the cam followers  36 , 38  would rest against the cam in about the middle B of the flat spot A and no or very little moment would be created. In the embodiment described herein, the cams  26 , 28  can have a profile C that converts the force exerted by the springs  82 , 84  to provide a moment to the pick roller  24 . More particularly, when the pick roller  24  is in the home position, the cam followers  36 , 38  contact portions D of the cams  26 , 28  that are reducing in radius which provides the moment to urge rotation of the pick roller  24  in the first direction. 
     The urging of the shaft  22  in the first direction when the gear  54  is in the gear home position works in conjunction with the clutch mechanism  70  to selectively rotate the pick roller  24 . More particularly, with reference to  FIG. 8 , when the gear  54  is in the gear home position, the springs  82 , 84  acting through the cams and cam followers urge the gear to rotate in the first direction (illustrated by Arrow A in  FIG. 8 ). Despite the urging, the pawl  74  of the clutch mechanism  70  in the pawl first position engaged with the rib  64  of the gear  54  prevents the gear  54  from rotating which prevents the gear  54  from engaging and being driven by the drive gear  58 . When the solenoid  72  is actuated, the pawl moves to the pawl second position and the urging of the gear  54  is allowed to rotate the gear into engagement with the drive gear  58 . Thus, the pawl  74  limits rotation of the gear  54  in the first direction when the pawl  74  is in the pawl first position and the gear  54  is in the gear home position and allows rotation of the gear  54  in the first direction when in the pawl second position. As already mentioned, when the gear  54  rotates, the cams  26 , 28  also permit the lift plate  30  to be moved toward the raised position. 
     Because the solenoid  72  is attached to the frame  16  and the pick roller gear  54  is attached to the door body  14 , the pawl  74  does not maintain the gear  54  in the gear home position when the door body  14  is in the door open position. More specifically, when the door body  14  is in the door open position, the pawl  74  is disengaged from the gear  54  irrespective of which position, the pawl first position or the pawl second position, that the pawl is in. To prevent the pick roller gear  54  from moving from the gear home position when the door body  14  is open, the stopping means includes a locking mechanism that locks the pick roller gear  54  in the home position even when the door body  14  is in the door open position. More specifically, with reference to  FIG. 9 , the pick roller gear  54  includes a resilient arm  90  and the door body  14  includes a notch structure  92  having a distal edge  94  including a V-shaped notch  96 . 
     When the pick roller gear  54  is in the gear home position, the resilient arm  90  rests in the notch  96  (as shown in  FIG. 9 ) thereby maintaining the missing teeth section  56  in alignment with the drive gear  58 , even when the door body  14  is in the door open position. The V-shape of the notch  96  urges the pick roller gear  54  toward the gear home position, particularly when the pick roller gear is initially rotated away from the home position, and maintains the pick roller gear in the gear home position. The resilient arm  90  can be moved out of the notch  96  and beyond the notch structure when a sufficient force is applied to the pick roller gear  54 . For example, when the door body  14  is in the door closed position and the springs  82 , 84  urge the gear  54  to rotate in the first direction, provided the pawl  74  is in the pawl second position, the urging caused by the springs is sufficient to move the resilient arm  90  from the notch  96  past the notch structure  92  and to cause engagement between the teeth of the pick roller and the drive shaft. Generally, no force is applied to the resilient arm  90  except that of the springs  82 , 84  when the solenoid  72  is actuated which increases the useful life of the arm. 
     Having a stopping means that maintains the pick roller  24  in the pick roller home position without requiring a solenoid to be mounted on the door body reduces the overall manufacturing cost of the printer device  10 , reduces the complexity of the design and improves the overall safety. Moreover, using the same springs  82 , 84  for urging the lift plate  30  and for urging rotation of the pick roller shaft further reduces manufacturing costs. If a print media jam occurs, the door body  14  is opened which separates the pick roller  24  from the separator  40  allowing for relatively easy access for jam removal without allowing the pick roller  24  to move from its home position. 
     In operation, when the pick roller  24  is in the pick roller home position and held in that position, a drive shaft (not shown) associated with the drive gear  58  can be used for other, unrelated functions. When desirable to pick a sheet from the tray  20 , the solenoid is actuated which moves the pawl  74  to the pawl second position. The bias force acting from the springs  82 , 84  and through the cams  26 , 28  and cam followers  36 , 38  rotates the shaft  22  and allows the drive gear  58  to engage the pick roller gear  54 . The D-section  42  rotates once and is caught by the pawl  74  on its way around (the pawl is generally urged toward the pawl first position so immediately after actuation it moves back toward the pawl first position). Thus, the pick roller  24  is selectively maintained in its home position until desirable to actuate, even when the door body  14  is in the door open position. 
     The exemplary embodiment has been described with reference to the embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.