Patent Publication Number: US-7594652-B2

Title: Separation system

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application is related to co-pending U.S. patent application Ser. No. 11/305,639 filed on Dec. 16, 2005 by Louis C. Barinaga and entitled TORQUE COUPLING, the full disclosure which is hereby incorporated by reference. The present application is further related to copending U.S. patent application Ser. No. 11/669,277 filed on the same day herewith by Raymond C Shermim, Allan G. Olson, Wesley R. Schalk and Juan D. Ramos and entitled MEDIA DRIVE, the full disclosure of which is hereby incorporated by reference. 
     BACKGROUND 
     Sheets of media picked from a stack may sometimes overlap, causing jams in a media handling system. However, extensive gaps between sequential sheets reduces throughput. Mechanisms for controlling gaps between sequential sheets are sometimes complex and expensive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a media interaction system according to an example embodiment. 
         FIG. 2  is a side elevational of another embodiment of the media interaction system of  FIG. 1  according to an example embodiment. 
         FIG. 3  is a top perspective view of a portion of the media interaction system of  FIG. 2  illustrating a transmission in a first output state according to an example embodiment. 
         FIG. 4  is a sectional elevational view of a media lift mechanism of the transmission of  FIG. 3  in a first pick tire state according to an example embodiment. 
         FIG. 5  is a side elevational view of the media lift mechanism of  FIG. 4  and a second pick tire state according to an example embodiment. 
         FIG. 6  is a perspective view of the media interaction system of  FIG. 2  illustrating a shifter in a second output state according to an example embodiment. 
         FIG. 7  is a perspective view of the media interaction system of  FIG. 7  illustrating the shifter with portions omitted for purposes of illustration according to an example embodiment. 
         FIG. 8  is a perspective view of the media interaction system of  FIG. 7  illustrating a shifter in a shifting state according to an example embodiment. 
         FIG. 9  is a top perspective view of the media interaction system of  FIG. 2  illustrating the transmission in a third output state according to an example embodiment. 
         FIG. 10  is a top perspective view of the media interaction system of  FIG. 2  illustrating the transmission in the second output state according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
       FIG. 1  schematically illustrates media interaction system  20  according to one example embodiment. Media interaction system  20  is configured to pick individual sheets of media from a stack and to interact with the sheets in one or more fashions. Such interactions include printing upon one or both sides of the sheets, scanning images upon such sheets, stapling such sheets, folding such sheets and the like. As will be described hereafter, media interaction system  20  reliably separates consecutive or sequential sheets while reducing cost and complexity of system  20 . 
     As shown by  FIG. 1 , media interaction system  20  includes housing  24 , media input  26 , separation system  28 , deskewing system  30 , media interaction device  32 , media interaction device  34 , media paths  36 A,  36 B,  36 C,  36 D and  36 E (collectively referred to as media paths  36 ), diverters and  40 A and  40 B (collectively referred to as diverters  40 ), sensors  42 A,  42 B,  42 C,  42 D,  42 E,  42 F and  42 G (collectively referred to as sensors  42 ) and outputs  44 A and  44 B (collectively referred to as outputs  44 ). Housing  24  comprises an enclosure, framework or other arrangement of panels or structures configured to support and close components and devices of system  20 . Housing  24  may have a variety of sizes, shapes and configurations. Although  FIG. 1  schematically illustrates components in particular locations and relative positions within housing  24 , in other embodiments, such components may be enclosed within housing  24  in other locations and relative positions. 
     Input  26  comprises one or more structures configured to support, hold and store sheets of media  46  prior to such sheets being picked and separated by separation system  28 . Input  26  may comprise a tray, bin or other storage structures. Although input  26  is illustrated as being contained within housing  24 , in other embodiments, input  26  may at least partially project beyond housing  24 . In particular embodiments, input  26  may include a movable plate or floor  48  resiliently biased so as to urge a topmost sheet of media  46  in an upward direction for picking by separation system  28 . In other embodiments, input  26  may alternatively have a fixed or stationary floor  48 . 
     Media separation system  28  picks individual sheets of media  46  and separates consecutive picked sheets while moving such sheets towards media paths  36 . Separation system  28  includes edge abutment surface  50 , pick tire  52 , take away shaft  54 , pinch roller  56 , drive motor  58 , transmission  60 , command interface  61  and controller  62 . Edge abutment surface  50  comprises a surface configured to contact and abut leading edges of sheets of media  46  while such sheets are resting as part of a stack. In the particular embodiment illustrated, surface  50  extends in a plane that is oblique to an axis that is perpendicular to the face of the stack of media  46 . In the particular example illustrated, the stack of media  46  rests in a horizontal orientation upon input  26 . In another embodiment, the stack of media rests in a vertical or an upwardly sloped orientation. Because surface  50  is angled or oblique, surface  50  enhances separation of adjacent sheets in the stack of media  46 . In other embodiments, surface  50  may alternatively extend perpendicular to the faces of the sheets of media  46  or may be omitted. 
     Pick tire  52  comprises one or more members configured to originally engage in contact a topmost sheet of the stack of media  46 , wherein rotation of pick tire  52  moves the topmost sheet towards surface  50 . In one embodiment, pick tire  52  comprises a cylindrical member having an outer circumferential surface having a relatively high coefficient of friction with media  46 . In yet another embodiment, pick tire  52  may have a D-shaped cross-section. In other embodiments, pick tire  52  may be provided by a belt configured to contact the topmost sheet of media. In still other embodiments, pick tire  52  may have other configurations. 
     Take away shaft  54  comprises a shaft, roller or other member configured to be rotationally driven while in frictional contact with a sheet of media  46  so as to drive the sheet of media  46 . Take away shaft  54  cooperates with rotatably supported pinch roller  56  to form a take-away nip  66  through which a sheet is driven into media path  36 A. In other embodiments, other structures opposite to take away shaft  54  may be used in lieu of pinch roller  56  to form a take away nip  66  by which opposite faces of a sheet of media may be contacted and through which a sheet of media may be driven. 
     Drive motor  58  comprises a source of torque for rotationally driving at least pick tire  52  and take away shaft  54 . In one embodiment, drive motor  58  comprises a motor dedicated to supplying torque in a single direction. In other embodiments, a motor  58  may be configured to selectively supply torque in both directions. According to one embodiment, motor  58  comprises a DC motor. In other embodiments, motor  58  may comprise other torque sources. 
     Transmission  60  comprises an arrangement of motion transmitting elements, such as gears, belts and pulleys, chain and sprockets or the like configured to transmit torque from motor  58  to both pick tire  52  and take away shaft  54 . As schematically represented in  FIG. 1 , transmission  60  is selectively actuatable between three output states  70 ,  72  and  74 . In output state  70 , transmission  60  is configured such that torque delivered to pick tire  52  rotationally drives pick tire  52  in a first direction (as indicated by broken line  76 ) while torque delivered to take away shaft  54  rotationally drives shaft  54  in a second opposite direction (as indicated by solid lines  78 ). As a result, in response to control signals from controller  62 , motor  58  may supply torque in a first direction, causing pick tire  52  to be rotationally driven in a forward media advancing or feeding direction (counterclockwise as seen in  FIG. 1 ) while take away shaft is driven in an opposite reverse feeding direction (clockwise as seen in  FIG. 1 ). By controlling motor  58  to supply torque in the first direction, system  20  may pick a topmost sheet of media  46  and urge a topmost sheet against and along surface  50  and into abutment with nip  66 , which serves as a squaring surface, squaring the sheet at nip  66 . In other embodiments, a sheet may be further driven by shaft  54  into abutment with another surface, such as another roller, for squaring or deskewing the sheet. 
     Alternatively, in response to control signals from control  62 , motor  58  may supply torque in a second opposite direction, causing take away shaft  54  to be rotationally driven in a forward media advancing direction (counterclockwise as seen in  FIG. 1 ) while pick tire  52  is out of driving engagement with media  46 .). For purposes of this disclosure, a pick tire is “out of driving engagement” with a sheet or a stack of media when the pick tire is either not rotated or is idling (rotating while not under power) while in contact with media  46  due to a friction clutch (not shown) and/or is lifted or otherwise moved out of engagement with media  46  while being rotationally driven in a reverse feeding direction (clockwise as seen in  FIG. 1 . In particular, according to one embodiment, the supply of torque from drive motor  58  in the second direction results in an arm supporting pick tire  52  to be pivoted so as to lift pick tire  52  out of engagement with media  46 . One example of such an arrangement for utilizing torque to lift pick tire  52  out of engagement with media  46  is shown and described in co-pending U.S. patent application Ser. No. 11/669,277 filed on the same day herewith by Raymond C. Sherman, Allan  0 . Olson, Wesley P. Schalk and Juan D. Ramos and entitled MEDIA DRIVE, a full disclosure of which is hereby incorporated by reference. In other embodiments, other mechanism may be used to disengage pick tire  52  from media  46  as a result of motor  58  supplying torque in the second direction. 
     In output state  72 , transmission  60  is configured such that torque delivered to pick tire  52  rotationally drives pick tire  52  in a forward media advancing direction (counterclockwise as seen in  FIG. 1 ) at a first surface speed (the speed at the outermost surface of pick tire  52 ) and such that torque delivered to take away shaft  54  rotationally drives take away shaft  54  in the forward media advancing direction (counterclockwise as seen in  FIG. 1 ) at a second surface speed greater than the first surface speed. As a result, consecutive or sequential sheets of media  46  are picked and driven to media path  36 A with a substantially controlled and reliable gap therebetween. 
     Because sheets of media  46  are continuously picked by pick tire  52  and are continuously taken away and driven to media paths  36 , media throughput is enhanced. Media throughput is not delayed by reversal of motor  58  to change from picking a sheet to feeding a sheet. Because the tire  52  and take away shaft  54  are both driven using torque supplied by a single motor  58 , separation system  28  and system  20  may be less complex, less expensive and more compact. Moreover, because transmission  60  may be shifted to an output state wherein the pick tire is out of driving engagement with a stack of media, separation system  28  is well suited for use in printers or other media handling systems, wherein the entire stack of media may not be picked and printed or otherwise manipulated. For example, the picking and transport of sheets from a stack may be stopped prior to exhaustion of the stack and without taking and transporting an extra sheet which is blank and not printed upon. 
     At the same time, because transmission  60  provide a controlled and reliable gap between consecutive sheets in output state  72 , separation system  28  is able to support various features such as edge-to-edge printing, skew correction and the sheet diversion to alternative media paths while sheets of media  46  are continuously picked by pick tire  52  and driven by take away shaft  54  without interruption. By reliably and consistently controlling the gap between consecutive sheets, transmission  60  of system  28  further enables the use of less complex and less expensive sensors. For example, since the gap is reliably controlled and since the likelihood of consecutive sheets accidentally overlapping is reduced, the positioning of sheets may be adequately sensed using less complex and less expensive non-transmissive sensors. One example of a non-transmissive sensor is a mechanical flag used in combination with a sensing device such as an optical sensor. 
     According to one embodiment, the difference in the surface speeds of pick tire  52  and take away shaft  54  is such that a trailing edge of a first sheet and a leading edge of a second subsequent sheet are spaced apart from one another by a gap of at least about 30 mm at one location along media path  36 A after moving past nip  66 . At the same time, the separation distance or gap between the trailing edge and the leading edge of consecutive sheets is reliably controlled. Consequently, the controlled gap is sufficiently large for supporting various features such as edge-to-edge printing, skew correction and the sheet diversion to alternative media paths while maintaining media throughput. 
     In output state  74 , transmission  60  is configured such that torque is delivered to take away shaft  54  to rotationally drive take away shaft  54  in a forward media feeding direction (counterclockwise as seen in  FIG. 1 ) while the little or no torque is transmitted to pick tire  52  such that pick tire  52  does not drive sheets of media  46  towards take away shaft  54 . According to one embodiment, transmission  60  operates in output state  74  when a last or final sheet of media  46  from the stack has been removed. Output state  74  permits the final sheet to be transported further along media paths  36  by take away shaft  54  without an additional unwanted blank sheet picked from the stack of media  46 . In other embodiments, output state  74  as well output state  70  may be omitted. 
     Command interface  61  comprises an interface by which instructions or commands are input to controller  62  from a source external to system  20 . In particular, interface  61  facilitates the entry of commands selecting which of output states  70 ,  72  or  74  that transmission  60  two which transmission  60  is to be actuated. In one embodiment, interface  51  may be configured to receive commands or instructions from a person using system  20 . For example, command interface  51  may comprise a keypad, a touchscreen, a mouse, a keyboard, a switch, button, or other means at which a person may manually enter selections. In other embodiments, interface  61  may comprise a microphone and associated voice or speech recognition software. In still other embodiments come interface  61  may comprise an electrical or optical connection with an external electronic control device such as an external computer or processor. In other embodiments, interface  61  may be omitted. 
     Controller  62  comprises a processing unit configured to generate control signals directing operation of drive motor  58  and transmission  60 . For purposes of this application, the term “processing unit” shall mean a presently developed or future developed processing unit that executes sequences of instructions contained in a memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals. The instructions may be loaded in a random access memory (RAM) for execution by the processing unit from a read only memory (ROM), a mass storage device, or some other persistent storage. In other embodiments, hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. For example, controller  62  may be embodied as part of one or more application-specific integrated circuits (ASICs). Unless otherwise specifically noted, the controller is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit. 
     In the particular embodiment illustrated, controller  62  additionally generates control signals directing the operation of media interaction device  32 , media interaction device  34  and one or more actuators (not shown) configured to selectively actuate diverters  40  between different positions or diversion states. In the embodiment illustrated, controller  62  further receives information or signals from various sensors of system  20  including, but not limited to, sensors  42 . Controller  62  is configured to use and analyze such information received from sensors  42  to generate the aforementioned control signals. In other embodiments, separate controllers may be provided for one or more of such components of system  20 . 
     In operation according to one embodiment, in response to receiving input the interface  61 , controller  62  generates control signals actuating transmission  60  to output state  70  and generate control signals causing motor  58  to supply torque in the first direction. As a result, the top most sheet of media  46  is picked by pick tire  52  and squared against take away shaft  54 , rotating in a reverse direction. Thereafter, controller  62  will generate control signals causing drive motor  58  to supply torque in the second direction. This results in take away shaft  54  further driving be picked sheet of media  46  into media path  36 A and results in the pick tire  52  being withdrawn from media  46 . Because pick tire  52  is withdrawn from the stack of media  46 , skewing of the picked sheet being transported by shaft  54  may be less likely. 
     In response to receiving input via interface  61  requesting faster throughput of system  20 , controller  62  generates control signals actuating transmission  60  to output state  72 . As a result, both pick tire  52  and take away shaft  54  are concurrently driven by motor  58  and the media advanced direction, with take away shaft  54  being driven at a slightly faster surface speed as compared to pick tire  52 . This results in a controlled gap between successive sheets of media  46 . In response to the last or final sheet being picked from the stack media  46 , controller  62  generates control signals actuating transmission  60  to output state  74  or output state  70  with motor  58  being driven in the second direction. As a result, the last or final sheet is transported by take away shaft  54  and no additional sheets are picked by pick tire  52 . 
     Deskewing system  30  comprises an arrangement of components configured to square off sheets of media  46  after such sheets have exited nip  66 . In the example embodiment shown, the skewing system  30  is configured to drive a sheet that is passed nip  66  in a reverse direction against a squaring surface. In the example illustrated, a squaring surface is provided by nip  66 . In other embodiments, other surfaces generally perpendicular to media path  36 A may serve as a squaring surface. 
     In the particular about illustrated, deskewing system  30  includes feed shaft  90  and pinch roller  92 . Feed shaft  90  comprises one or more rollers configured to frictionally engage a sheet of media along media path  36 A and to be selectively rotationally driven in one or both directions. Feed shaft  90  cooperates with idler  92  to sandwich a sheet of media therebetween. In one embodiment, idler  92  comprises an idling roller configured to frictionally engage an opposite side of a sheet of media. In other embodiments, other surfaces opposite to the roller  90  which are rotationally driven or which are stationary may be employed. Feed shaft  90  is configured to be rotationally driven in a reverse direction to drive a sheet of media against nip  66  so as to square the sheet of media against a nip  66 . In other embodiments, shaft  54  may alternatively drive a leading edge of a sheet into abutment with roller  90  while roller  90  is being rotated in a reverse direction to square the media sheet. Because separation system  28  provides a controlled and reliable gap between successive sheets with a reduced likelihood of such sheets overlapping, system  30  has time to reverse the direction of movement of a first sheet to square the first sheet against nip  66  prior to arrival of a successive sheet. As a result, squaring may be performed with a reduced risk of sheets becoming overlapped and with a reduced risk of jams or other media handling issues. 
     In one embodiment, feed shaft  90  is additionally configured to be rotationally driven in a forward media advancing direction to move sheets of media towards either of media feed paths  36 B or  36 C. As schematically illustrated in  FIG. 1 , feed shaft  90  is configured to be rotationally driven using output from transmission  60  which receives torque from motor  58 . In other embodiments, feed shaft  90  may be rotationally driven by other sources of torque or other transmissions. In still other embodiments, deskew system  30  may be omitted. 
     Media interaction device  32  comprises and mechanism configured to interact with a sheet of media. In one embodiment, media interaction device  32  is configured to scan or capture an image contained on one or both faces of a sheet of media. In another embodiment, media interaction device  32  is configured to modify a sheet of media. For example, media interaction device  32  may be configured to staple, fold or print upon a sheet of media. In the particular embodiment illustrated, media interaction device  32  comprises a device configured to print along an adjacent to one or both of a trailing edge and a leading edge of the sheet of media. For example, in one embodiment, media interaction device  32  comprises one or more drop-on-demand ink jet print heads which deposit eight or other fluid upon a sheet of media. To print adjacent to either the leading edge of the trailing edge of the sheet of media, media interaction device  32  over sprays the fluid from its nozzles. Because separation system  28  provides a controlled separation distance or gap between consecutive sheets while reducing the likelihood of overlap of such sheets, media interaction device  32  may better print or deposit fluid, such as ink, adjacent to the forward or leading edges with a reduced risk of such fluid being deposited on a successive sheet. At the same time, separation system  28  permits this controlled gap to be maintained while through putting media at a relatively fast rate. 
     Media interaction device  34  comprises a mechanism configured to interact with a sheet of media. In one embodiment, media interaction device  32  is configured to scan or capture an image contained on one or both faces of a sheet of media. In another embodiment, media interaction device  32  is configured to modify a sheet of media. In one embodiment, media interaction device  34  is different from media interaction device  32 , permitting system  20  to provide multiple media treatment functions. 
     Media paths  36  comprise channels, passages or cavities through which sheets of media are guided and driven from nip  66  and ultimately to one of outputs  44 . Media paths  36  are formed by media guiding panels, tabs, or other stationary structures as well as rotationally driven or idling rollers, belts or wheels. In the particular example illustrated, media path  36 A leads from nip  66  to diverter  40 A. Media path  36 B extends from media path  36 A across or through media interaction device  32  to diverter  40 B. Media path  36  extends from diverter  40 A, across or through media interaction device  34  and to output  44 B. Media path  36 D extends from diverter  40 B to output  44 A. Media path  36 E extends from diverter  40 B back to media path  36 A. Media path  36 E permits sheets to be overturned for printing on an opposite face of a sheet of media or for scanning an opposite face of a sheet of media, depending upon the function performed by media interaction device  32 . 
     Diverters  40  comprise structures, such as flaps, configured to move between different positions or states with respect to adjacent media paths  36  so as to selectively channel or direct sheets of media between two or more alternative paths  36 . Diverters  40  are actuated between such different positions by one or more actuators, such as electric solenoids (not shown), which are actuated in response to control signals from controller  62 . In the particular example illustrated, diverter  40 A selectively directs sheets of media to either media path  36 B for interaction by media interaction device  32  or media path  36 C for interaction by media interaction device  34 . Diverter  40 B selectively directs sheets of media to either media path  36 D and output  44 A or media path  36 E for overturning of the sheet and for potential subsequent interaction with either media interaction device  32  or media interaction device  34 . 
     Although system  20  is illustrated as including the aforementioned media paths  36  and aforementioned diverters  40 , in other embodiments, system  20  may include a greater or fewer of such paths were diverters. Because separation system  28  provides a controlled gap between sequential sheets of media  46 , diverters  40  have a greater amount of time to be actuated between different diversion positions. As a result, diverters  40  may more reliably direct sheets of media to a selected media path  36 . 
     Sensors  42  comprise of devices configured to sense or otherwise detect the presence of a sheet of media  46  at a particular point along one of media paths  36 . Sensors  42  provides signals to controller  62  indicating to controller  62  the location of a sheet of media at a particular point in time, permitting controller  62  to generate control signals appropriately directing the operation of media interaction devices  32  and  34  as well as movement of diverters  40 . Although system  20  is illustrated as including the depicted sensors  42 A- 42 E at the noted locations, in other embodiments, system  20  may include a greater or fewer of such sensors  42  and such sensors  42  may be positioned at other locations. 
     Because separation system  28  provides a controlled gap between consecutive sheets of media  46  with a reduced likelihood of inadvertent overlap of such sheets while providing high media throughput, system  20  may employ less complex and less expensive non-transmissive sensors. Non-transmissive sensors are sensors that do not have the additional complexity associated with sensing overlapping sheets or sensing through sheets. 
     One example of a non-transmissive a sensor is a non-transmissive mechanical sensor as depicted in more detail with a sensor  42 C. As shown by  FIG. 1 , sensor  42 C includes a structure, such as a flag  94  pivotally supported about a pivot axis  95  between a first position in which flag  94  extends across or intercepts an adjacent media path  36  (such as when no sheet is present) and a second position in which flag  94  blocks or intercepts light from a light emitter  96  before the light reaches a light detector  97 . In such an embodiment, flag  94  is resiliently biased to a position across the media path  36  such that upon encountering a sheet of media, flag  94  is moved to the second position. 
     By providing a sufficiently sized and controlled gap between consecutive sheets, separation system  28  provides the flags  94  of sensors  42  with a sufficient amount of time to return to their initial media path intercepting position after a trailing edge of a first sheet has passed and before encountering a leading edge of a second consecutive sheet. In one embodiment, the gap between consecutive sheets is sized such a sensor  42  has at least 20 ms to resiliently return to its media path intercepting position after the first sheet has passed sensor  42 . In other embodiments, other mechanical non-transmissive sensors may be employed. 
     Outputs  44 A and  44 B comprise trays, bins or other structures configured to receive and store interact upon sheets of media. Although system  20  is illustrated as including two separate outputs  44 , and other embodiments, system  20  may have a greater or fewer of such outputs  44 . 
       FIGS. 2-10  illustrate media interaction system  120 , another embodiment of system  20 . In the particular embodiment illustrated, media interaction system  120  comprises a printer configured to deposit printing material upon sheets of media. In other embodiments, system  120  may comprise other devices that interact with sheets of media. Like system  20 , media interaction system  120  reliably separates consecutive or sequential sheets while reducing cost and complexity and with reduced likelihood of picking an extra sheet from a stack. 
     As shown by  FIGS. 2-5 , media interaction system  120  includes housing  124 , media input  126 , separation system  128 , media interaction device  132 , media path  136  and output  44 A (shown and described with respect to system  20 ). Housing  124  comprises an enclosure, frame or other arrangement of panels or structures configured to support and enclose components and devices of system  120 . Housing  124  may have a variety of sizes, shapes and configurations. 
     Input  126  comprises one or more structures configured to support, hold and store sheets of media in a stack prior to such sheets being picked and separated by separation system  128 . In the particular embodiment illustrated coming input  126  comprises a tray. In other embodiments, input  126  may be integrally provided as part of the housing  124  or may comprise other stack storage structures such as a bin. Although input  126  is illustrated as having a fixed or stationary floor  148 , in other embodiments, input  126  may include a movable plate or floor resiliently biased so as to urge a top most sheet of media in an upward direction as seen in  FIG. 2  for picking by separation system  128 . 
     Separation system  128  picks individual sheets of media from a stack of media contained within input  126  and separates consecutive picked sheets while moving such sheets towards media path  136 . Separation system  128  includes edge abutment surface  150 , arm  151 , pick tire  152 , take away shaft  154 , feed shaft  155 , roller  156 , drive motor  158  (shown in  FIG. 3 ), transmission  160 , command interface  61  (schematically illustrated in  FIG. 3  and described with respect to  FIG. 1 ) and controller  62  (schematically shown in  FIG. 3  and described with respect to  FIG. 1 ). Edge abutment surface  150  comprises a surface configured to contact and abut leading edges of sheets of media while such sheets are resting as part of a stack. As shown in  FIG. 2 , surface  150  extends in a plane that is oblique to an axis that is perpendicular to floor  148 . Because surface  150  is oblique, surface  150  facilitates the separation of adjacent sheets in a stack. In other embodiments, surface  150  may alternatively extend perpendicular to the faces of the sheets or may be omitted. 
     Arm  151  comprises an elongated member rotationally supporting pick tire  152  and pivotally supported so as to pivot between a lower media engaging position (shown in  FIG. 2 ) and a raised or elevated media disengaged position (shown in  FIG. 5 ). In other embodiments, arm  151  may have a variety of sizes, shapes and configurations. In addition, in other embodiments, system  120  may include multiple arms having multiple pick tires. As shown in  FIGS. 2 and 3 , system  120  includes a bias arm  161  carrying an idling roller  163  which bear against a stack of media in input  126 . In other embodiments, bias arm  161  and roller  163  may be omitted or additional such bias arms may be employed. 
     Pick tire  152  comprises one or more members configured to rotationally engage and contact a top most sheet of a stack of media, wherein rotation of the tire  152  moves the top most sheet towards surface  150 . In the embodiment illustrated, pick tire comprises a cylindrical member having an outer circumferential surface having a relatively high coefficient of friction with the media. In another embodiment, pick tire  152  may have a D-shaped cross-section. In yet other embodiments, pick tire  152  may be provided by a belt configured to contact the top most sheet of a stack. In still other embodiments, pick tire  152  may have other configurations. 
     Take away shaft  154  comprises a shaft, roller or other member configured to be rotationally driven while in frictional contact with a sheet of media so as to drive the sheet of media. Take away shaft  154  cooperates with a rotationally supported idler roller  156  to form a take away nip  166  through which the sheet is driven into media path  136 . In other embodiments, other structures opposite to take away shaft  154  may be used in lieu of roller  156  to form a take away nip  166 . 
     Feed shaft  155  (shown in  FIG. 3 ) extends across media path  136  and is configured to further engage and move sheets of media along media path  136 . Feed shaft  155  is generally located downstream from take away shaft  154  along media path  136 . In one embodiment, feed shaft  155  is also configured to be rotated in the reverse direction while take away shaft  154  is driven in a forward direction, wherein shaft  155  provides a squaring surface for deskewing sheets of media. In the example embodiment illustrated, feed shaft  155  also serves as part of the transmission  160 . 
     Drive motor  158  comprises a source of torque for rotationally driving at least pick tire  152  and take away shaft  154 . In the embodiment illustrated, drive motor  158  comprises a motor configured to supply torque in both directions. In another embodiment, drive motor  158  comprises a motor configured to supply torque in both directions. According to one embodiment, motor  158  comprises a DC motor. In other embodiments, motor  158  may comprise other torque sources. 
     Transmission  160  comprises an arrangement of motion transmitting elements, such as gears, belts and pulleys, chains and sprockets or the like configured to transmit torque from motor  158  to pick tire  152  and to take away shaft  154 . As will be described hereafter, transmission  160  is selectively actuatable between three output states: output state  170  (shown in  FIGS. 2-5 , output state  172  (shown in  FIG. 9  and output state  174  (shown in  FIGS. 6 ,  7  and  10 ). In output state  170 , transmission  160  transmits torque such that pick tire  152  and feed shaft  155  are driven in opposite directions. As a result, motor  158  is reversed to alternate between picking of a sheet and driving a picked sheet to create a gap between consecutive sheets. In output state  172 , both the pick tire  152  and take away shaft  154  are driven in a same direction by the different surface speeds so as to create gap. In output state  174 , transmission  160  stops transmitting torque to pick tire  152  while continuing to transmit torque to take away shaft  154 . Output state  174  permits the last desired sheet to be transported by take away shaft  154  and feed shaft  155  through and along media path  136  while pick tire  152  is out of driving engagement such that an extra sheet is not picked at the end of a job. 
     In the particular example embodiment illustrated, transmission  160  includes power train  202 , feed shaft  155 , power train  206 , power train  208 , power train  210 , power train  212 , media lift mechanism  214  (shown in  FIGS. 4 and 5 ) and shifter  216 . Power train  202  comprises an arrangement of motion transmitting members configured to transmit torque from motor  158  to feed shaft  155 . In the example illustrated, power train  202  includes belt  220  and pulley  222  which is fixed to feed shaft  155 . In other embodiments, power train  202  may comprise a gear train, a chain and sprocket arrangement or combinations thereof. 
     Feed shaft  155  extends from pulley  222  and extends across media path  136  (shown in  FIG. 2 ) to power train  206 . Feed shaft  155  includes gear  224  which is configured to be selectively operably coupled to either power train  208  or power train  210  by shifter  216 . Feed shaft  155  transmits torque to power train  206  and selectively to power train  212  depending upon a state of the shifter  216 . 
     Power train  206  comprises an arrangement of motion transmitting members operably coupled to one another between feed shaft  155  and take away shaft  154 . As shown by  FIG. 3 , power train  206  comprises a gear train operably connected between feed shaft  155  and take away shaft  154 . Power train  206  maintains a forward rotation of shaft  154  independent of the rotation direction of shaft  155 . In other embodiments, power train  206  may alternatively include a belt and pulley arrangement, a chain and sprocket arrangement or combinations of one or more of a gear train, a belt and pulley arrangement or a chain and sprocket arrangement. 
     Power train  208  comprises an arrangement of motion transmitting members operably located between shifter  216  and power train  212 . As shown by  FIGS. 2 and 3 , power train  208  includes gears  230  and  232 . Gear  230  configured to be selectively engage by shifter  216 . Gear  232  a mesh engagement with gear  230  and is connected to power train  212 . Power train  208  configured such that when torque is transmitted to power train  212  by power train  208  in a first direction (rotation of pulley  222  in a clockwise direction as seen in  FIG. 3 ), pick tire  152  is driven in a forward media advancing direction while take away shaft  154  is also driven in a forward direction and while feed roller  204  is driven in a reverse direction. Power train  208  is configured such that when torque is transmitted to power train  212  by power train  208  in a second opposite direction (rotation of pulley  222  in a counterclockwise direction as seen in  FIG. 3 ), pick tire idles while in contact with a sheet as a result of the one way clutch  454  and take away shaft  154  and feed shaft  155  are both driven in a forward media advancing direction. 
     Power train  210  comprises a series of motion transmitting members operably coupled between shifter  216  and power train  212 . In contrast to power train  208 , power train  210  is configured such that when torque is transmitted to power train  212  by power train  210  in the first direction, media lift mechanism  214  lifts pick tire  152  out of engagement with a stack of media while take away shaft  154  is driven in a forward direction and feed shaft  155  is driven in a reverse direction. Powertrain  210  is configured such that when torque is transmitted to powertrain  212  by powertrain  210  in the second direction, pick tire  152  is driven in the same direction as the direction in which take away shaft  154  and feed shaft  155  are driven. In addition, pick tire  152  is rotationally driven at a surface speed less than the surface speed at which take way shaft  154  is driven. As a result, although sheets are continuously picked and transported for enhanced efficiency, separation system  128  provides a controlled gap between consecutive sheets. By reliably and consistently controlling the gap between consecutive sheets, transmission  160  of system  128  further enables the use of less complex and less expensive sensors. For example, since the gap is reliably controlled and since the likelihood of consecutive sheets accidentally overlapping is reduced, the positioning of sheets may be adequately sensed using less complex and less expensive non-transmissive sensors. One example of a non-transmissive sensor is a mechanical flag using combination with a sensing device such as an optical sensor. 
     According to one embodiment, the difference in the surface speeds of pick tire  152  and take away shaft  154  is such that a trailing edge of a first sheet and a leading edge of a second subsequent sheet are spaced apart from one another by a gap of at least about 30 mm at one location along media path  136  after moving past nip  166 . Consequently, the controlled gap is sufficiently large for supporting various features such as edge-to-edge printing, skew correction and the sheet diversion to alternative media paths while maintaining media throughput. 
     In the example illustrated, power train  210  includes gears  236 , gear  238  and a gear  232 . Gear  236  is configured to be operably engaged by shifter  216  and is in meshing engagement with gear  238 . Gear  238  comprises a cluster gear in meshing engagement with gear  236  and also in meshing engagement with gear  232 . As noted above, gear  232  is connected to power train  212 . Although power train  208  and  210  are illustrated as comprising gear trains, in other embodiments, such power trains may additionally or alternatively include belt and pulley arrangements or chain and sprocket arrangements. Such power trains may include a greater or fewer of the noted gears. 
     Power train  212  comprises an arrangement of motion transmitting members operably coupled between gear  232  and pick tire  152 . Power train  212  is further operably connected to lift mechanism  214  (shown in  FIGS. 4 and 5 ). As shown by  FIG. 3 , power train  212  includes gear  300 , shaft  302  and gear train  304 . Gear  300  is fixedly secured to shaft  302 . Shaft  302  is connected to gear train  304 . As noted above, shaft  302  further pivotally supports arm  151  and is pivotally supported by a portion of lift mechanism  214  at one end. Gear train  304  comprises a series of gears extending from shaft  302  to pick tire  152 . Torque transmitted via gear train  304 , drives pick tire  152 . 
       FIGS. 4 and 5  illustrate lift mechanism  214 . Lift mechanism  214  is shown and described in co-pending U.S. patent application Ser. No. 11/669,277 filed on the same day herewith by Raymond C. Sherman, Allan G. Olson, Wesley R. Schalk and Juan D. Ramos and entitled MEDIA DRIVE, the full disclosure of which is hereby incorporated by reference. Lift mechanism  214  comprises a mechanism configured to selectively move pick tire  152  toward or away from floor  148  of input  126  (shown in  FIG. 2 ). In the example illustrated, lift mechanism  214  is configured to selectively pivot arm  151  so as to move pick tire  152  relative to a stack of media in input  126 . As shown by  FIGS. 4 and 5 , lift mechanism  214  includes support  322 , drive train  324  including gears  326 ,  328  and  330 , cam  340 , cam follower  342 , rack  343 , rack gear  344  and disengagement mechanisms  346 ,  348 . 
     Support  322  comprises one or more structures configured to slidably support portions of lift mechanism  214 . In one embodiment, support  322  comprises a bar which is stationarily supported by housing  124  (shown in  FIG. 2 ). In other embodiments, support  322  may have other configurations. For example, in other embodiments, separate structures or different configurations may be utilized to slidably support portions of lift mechanism  214 . 
     Drive train  324  transmits power from shaft  302  of power train  212  to selectively raise or lower arm  151  and pick tire  152 . Gear  326  is fixed to an end of shaft  302  (at the knurled location  349  shown in  FIG. 3 ). Gear  326  is in meshing engagement with gear  328 . Gear  328  is an idler gear rotationally supported by support  322  in meshing engagement with gear  330 . Gear  330  is configured to be selectively engaged with rack gear  344  or one of disengagement mechanisms  346 ,  348 . Gear  330  cooperates with rack gear  343  to move cam  340  relative to cam follower  342 . 
     Cam  340  comprises a collection of surfaces configured to be linearly moved or translated against cam follower  342  which result in control the movement of cam follower  342  and arm  151 . As shown in  FIG. 5 , cam  340  extends from rack  343  and includes a ramp surface  350  and a plateau  352 . Ramp surface  350  is an inclined or sloped surface against which cam follower  342  slides up surface  350  when rack  343  is being linearly moved to the right (as seen in  FIG. 5 ) so as to pivot arm  151  in a clockwise direction (as seen in  FIG. 5 ) about axis  231  away from floor  148  (shown in  FIG. 2 ). When rack  343  is being moved to the left, cam follower  342  slides down surface  350  to pivot arm  151  in a counter-clockwise direction (as seen in  FIG. 3 ) about axis  231  towards floor  148  (shown in  FIG. 2 ). 
     Plateau  352  is a substantially flat or planar surface extending substantially parallel to the direction in which rack  343  linearly translates. Plateau  352  provides a surface against which cam follower  342  rests when arm  151  is in a fully raised position. As a result, when cam follower  342  is against plateau  352 , further movement of cam  340  does not result in further pivoting of arm  151 . As a result, plateau  352  provides a set or predetermined pivotal stop or point for arm  151  which is less sensitive to imprecise positioning of cam  340 . In other embodiments, cam  340  may have other configurations. 
     Cam follower  342  comprises a structure coupled to arm  151  so as to move with arm  151  and so as to engage and follow cam  340 .  FIG. 5  illustrates cam follower  342  extending from arm  151 . As shown in  FIG. 5 , cam follower  342  includes an arcuate surface  354  and a toe  356 . Surface  354  is arcuate so as to facilitate sliding and pivoting of arm  151  as cam  340  is moved against cam follower  342 . Toe  356  is a substantially flat end or tip configured to more stably rest upon plateau  352  when arm  151  has been pivoted to the fully raised position or media disengaging state. In other embodiments, cam follower  342  may have other configurations. 
     Rack  343  comprises a structure configured to linearly slide along support  322  while carrying cam  340 , rack gear  344  and disengagement mechanisms  346  and  348 . In other embodiments, rack  343  may have other configurations and may be slidably supported for linear movement by other structures. 
     As shown by  FIG. 4 , rack gear  344  extends from rack  343  across from or opposite to gear  330 . Rack gear  344  cooperates with gear  330  to linearly move rack gear  344  in response to rotation of gear  330  when gear  330  is in meshing engagement with rack gear  344 . Rack gear  344  has a sufficient length to translate cam  340  a sufficient distance so as to pivot arm  151  and pick tire  152  between the fully lowered and the fully raised positions. 
     Disengagement mechanisms  346  and  348  are located at opposite ends of rack gear  344  and comprise mechanisms configured to selectively disengage gear  330  from rack gear  344  depending upon the direction in which gear  330  is being rotationally driven. Disengagement mechanisms  346  is configured to disengage gear  330  when gear  330  is engaging disengagement mechanisms  346  and is rotating in a clockwise direction as seen in  FIG. 7 . Disengagement mechanisms  346  is further configured to engage gear  330  with rack gear  344  in response to gear  330  rotating in a second direction while in engagement with disengagement mechanisms  346 . Because disengagement mechanisms  346  disengages gear  330  from rack gear  344  when gear  330  is rotating in a first direction and when gear  330  is in engagement with disengagement mechanisms  346  at one end of rack gear  344 , shaft  302  and gear  330  may continue to rotate so as to continue to transmit torque to pick tire  152  without further movement of rack  343  and cam  340 . In other words, media drive member  226  may continue to drive a sheet of media in the media driving state while arm  151  is stationary. 
     In the example embodiment illustrated, disengagement mechanisms  346  includes slot  422 , catch  424  and lost motion element  426 . Slot  422  comprises an elongate channel configured to guide sliding translation as well as rotation of lost motion element  426 . Slot  422  is coupled to and carried by rack  343  and is configured to facilitate movement of lost motion element  426  between a first position (shown in  FIG. 4 ) in which the lost motion element  426  freely rotates within slot  422  at one end of slot  422  and a second position in which lost motion element  426  engages catch  424  such that rotation of element  426  is inhibited. In other embodiments, slot  422  may comprise other guiding mechanisms or structures. 
     Catch  424  comprises one or more structures couple to and carried by rack  343  and configured to engage lost motion element  426  so as to inhibit or stop rotation of lost motion element  426 . In the embodiment illustrated, catch  424  comprises a hook-like structure configured to engage teeth of lost motion element  426 . In other embodiments, catch  424  may comprise other structures or may alternatively or additionally be formed from a material having a high coefficient of friction with lost motion element  426  so as to inhibit relative rotation of lost motion element  426 . 
     Lost motion element  426  comprises a structure configured to be rotated when in engagement with gear  330 , to slide within slot  422  between a substantially freely rotating position and a caught or locked position, and to catch or engage catch  424 . In the example embodiment, lost motion element  426  comprises a gear having an axle  428  slidably and rotationally received within slot  422 . In other embodiments, lost motion element  426  may comprise other lost motion elements. For purposes of this disclosure, the term “lost motion element” is any structure or combination of structures configured to be moved, rotationally or linearly, without transferring motion to an adjacent structure and with insubstantial drag or frictional resistance. 
     Disengagement mechanism  348  is substantially similar to disengagement mechanisms  346  but is alternatively configured to disengage gear  330  from rack gear  344  in response to gear  330  in engagement with disengagement mechanism  348  and when gear  330  rotating in a counter-clockwise direction as seen in  FIG. 7 . Disengagement mechanism  348  is further configured to engage gear  330  with rack gear  344  in response to gear  330  rotating in a clockwise direction with as seen in  FIG. 7  and while in engagement with disengagement mechanism  348 . As a result, motor  158  may continue to drive gear  330  without further movement of rack  343  and cam  340  or further movement of arm  151  when media drive member  226  has been sufficiently moved to the disengaged state and when rack  343  has reached its travel limit. 
     In the particular example illustrated, disengagement mechanism  348  is similar to disengagement mechanisms  346 . Disengagement mechanism  348  includes slot  432 , catch  434  and lost motion element  436 . Slot  432 , catch  434  and lost motion element are each substantially identical to slot  422 , catch  424  and lost motion element  426 , respectively, except that catch  424  is on an opposite side of slot  422  and faces in an opposite direction as compared to catch  424 . Like disengagement mechanisms  346 , disengagement mechanism  348  permits continued rotation of gear  330  without imposition of substantial drag upon the rotation of gear  330  and without substantial noise. 
     Although disengagement mechanisms  346  and  348  are illustrated as being substantially identical to one another, in other embodiments, disengagement mechanisms  346  and  348  may alternatively be different from one another. In other embodiments, one or both of disengagement mechanisms  346 ,  348  may have other configurations. For example, in other embodiments, one or both of disengagement mechanisms  346  and  348  may comprise a one-way clutch. Examples of one-way clutches include, but are not limited to, a ratchet-type one-way clutch, a frictional one-way clutch or a check-ball one-way clutch. 
     Shifter  216  is configured to selectively connect feed shaft  155  with either power train  208  or power train  210  or to disengage feed shaft  155  from both power train  208  and power train  210  so as to shift transmission  160  between output states  170 ,  172  and  174 .  FIGS. 6-8  illustrates shifter  216  in detail, wherein shifter  216  is shown in output state  174  in which feed shaft  155  is disengaged from both power trains  208  and  210 . As shown by  FIGS. 6 and 7 , shifter  216  includes leash  450  (shown in  FIG. 6 ), swing arm  452 , coupling gears  454   a ,  454   b  (collectively referred to as coupling gears  454 ), clutch member  456 , clutch member  458  and bias  460  (shown in  FIG. 7 ). Leash  450  comprises a structure extending about shaft  155  in axial sliding engagement with shaft  155  to guide linear movement of swing arm  452  along an axis  464  of shaft  155  leash  450  further supports swing arm  452 . 
     As shown in  FIG. 6 , leash  450  includes an extension  465  configured to be engaged by media interaction device  132  (shown in  FIG. 2 ). In particular, extension  465  is configured to be engaged and driven by a carriage  466  which itself is driven by a carriage drive  467  (schematically shown). Carriage  466  supports print cartridges C 1  and C 2  which include printheads (not shown) and which contain ink. Carriage drive  467  comprises a device configured to move carriage  466 , carrying print cartridges C 1  and C 2 , parallel to axis  464  as defined by slider rod (not shown). In one embodiment, carriage drive  467  may include an endless belt (not shown) affixed to carriage  466  and driven to linearly translate carriage  466  along axis  464 . In the embodiment illustrated, the carriage drive  467  is used to scan carriage  466  across a medium being printed upon as well as to shift transmission  160 . In other embodiments, other mechanisms may be used to actuate shifter  216 . 
     Swing arm  452  comprises a structure non-rotatably coupled to clutch member  458  and rotatably supporting coupling gears  454 . Although swing arm  452  is illustrated as including a single swing arm, in other embodiments, swing arm  452  may include more than one arm supporting additional coupling gears  454 . 
     Coupling gears  454  comprises gears rotationally supported by arm  452  and matching with gear  224  of feed shaft  155 . Coupling gears  454  are further configured to mesh with either gear  230  of power train  208  or gear  236  of power train  210 , depending upon the orientation of swing arm  452 . Clear  454   a  is in mesh with gear  224  while gear  454   b  has a one-way clutch connecting it to gear  454   a . While driving gear  224  in a clockwise direction in  figure 3 , torque is transmitted to gear  454   b . When gear  224  is driven in a counter clockwise direction, gear  454   b  is idle. Gear  454   a  meshes with gear  236  while in position  172 . Gear  454 b meshes with gear  230  while in position  170 . 
     Clutch member  456  comprises a structure non-rotatably coupled to shaft  155  so as to rotate with shaft  155 . In the embodiment illustrated, clutch member  456  is also axially fixed to shaft  155 . As shown by  FIG. 7 , clutch member  456  includes axially extending castellations  468  configured to mate with corresponding castellations of clutch member  458 . Clutch member  456  may be selectively mated with clutch member  458  to transmit torque. 
     Clutch member  458  comprises a structure non-rotatably coupled to swing arm  452  such that rotation of clutch member  458  results in rotation of swing arm  452 . Clutch member  458  includes castellations  470  configured to intermesh with castellations  468  upon movement of clutch member  458  in the direction indicated by arrow  474  along axis  464 . Clutch member  458  is contained within leash  450  such that axial movement of leash  450  in the direction indicated by arrow  474  compresses bias  460 , which is a compression spring between leash  450  and clutch member  458 , to move clutch member  458  from the disengaged position (shown in  FIG. 7 ) to the engaged position (shown in  FIG. 8 ). When clutch member  458  is in the engaged position, coupling gears  454  are out of engagement with both gear  230  and gear  236 , permitting swing arm  452  to be rotated about axis  464 . When clutch member  458  is in the engaged position, clutch members  456  and  458  are interlocked such that rotation of feed shaft  155  results in the swing arm  452  being rotated to reposition coupling gears  454  to a desired angular orientation about axis  464  to actuate transmission  160  to one of output states  170 ,  172  and  174 . 
       FIG. 3  illustrates transmission  160  in output state  170 . In output state  170 , coupling gears  454  are positioned by swing arm  452  in intermeshing engagement with gear  224  of feed shaft  155  and gear  230  of power train  208 . As a result, torque from motor  158  drives pick tire  152  and take away shaft  154  in the same direction while driving the feed shaft  155  in the opposite direction. When motor  158  supplies torque in a first direction, pick tire  152  is rotationally driven in a counterclockwise direction (as seen in  FIG. 3 ) while feed shaft  155  is driven in a clockwise direction as seen in the  FIG. 3 . As a result, a sheet is driven into abutment with feed shaft  155  and squared. In response to signals from a sensor or based upon encoder signals associated with motor  158 , controller  62  generates control signals reversing the direction of motor  158 . As a result, torque is transmitted by transmission  160  such that feed shaft  155  is subsequently driven in a counterclockwise direction to feed the sheet along media feed path  136  (shown in  FIG. 2 ) while pick tire  152  is idling as a result of a one-way clutch  454 . 
     Should faster feeding of sheets be desired, a person may enter an appropriate command via command interface  61 . In response to such commands, controller  62  generates control signals directing carriage drive  467  to move carriage  466  into engagement with extension  465  of leash  450  (shown in  FIG. 6 ). Carriage  466  is driven along axis  464  until clutch member  458  is moved to the engaged position in which clutch member  458  meshes with clutch member  456  and in which coupling gear  454  is out of engagement with gear  230  of power train  208 . Thereafter, controller  62  may generate control signals directing motor  158  to rotationally drive shaft  155  so as to reposition swing arm  452  and coupling gear  454  across from and in substantial alignment with gear  236  of power train  210 . Once appropriately positioned, controller  62  generates control signals directing carriage drive  467  to move carriage  466  in the direction indicated by arrow  475  in  FIG. 7 , permitting bias  460  to move swing arm  452  and coupling gear  454  in the direction indicated by arrow  475  into meshing engagement with gear  236 . As a result, transmission  160  is shifted to output state  172  (shown in  FIG. 9 ). Controller  62  further generates control signals directing motor  158  to supply torque to feed shaft  155  which now results in transmission  160  rotationally driving pick tire  152 , take away shaft  154  and feed shaft  155  in the same direction, with pick tire  152  and take away shaft  154  being driven at different surface speeds. As noted above, the speeds are chosen such that a reliable and consistent gap is formed between consecutive sheets. As a result, time is not consumed between the picking of consecutive sheets to reverse the motor and sheets may be picked and driven at a faster rate. 
     Upon a final sheet being picked, as determined by controller  62  from print instructions indicating the number of pages to be printed, controller  62  may generate control signals shifting transmission  160  to output state  174  shown in  FIG. 10 . Shifting transmission  160  to output state  174  is substantially similar to the process described above for shifting from output state  170  to output state  172  except that swing arm  452  is rotated such that coupling gears  454  are not in engagement with either of power train  208  nor power train  210  as shown in  FIG. 7 . As a result, torque supplied to feed shaft  155  by motor  158  continues to drive take away shaft  154  and feed shaft  155  to transfer the last sheet along media path  136  (shown in  FIG. 2 ). At the same time, torque is not transmitted to pick tire  152 . Although pick tire  152  may remain in contact with a topmost sheet of the stack, the sheet is not driven. Consequently, an extra sheet is not picked. 
     Although the present disclosure has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.