RETARD ROLLER

BACKGROUND

During picking of sheets of media from a stack, multiple sheets sometimes stick together, resulting in a multi-pick. Mechanisms for separating the sheets that are stuck together may occupy valuable space, may be complex or may be ineffective at reducing the occurrence of multi-picks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a printing system according to an example embodiment.

FIG. 2 is a schematic illustration of a media feed system of the printing system of FIG. 1 illustrating initial picking of a sheet according to an example embodiment.

FIG. 3 illustrates the media, feed system of FIG. 2 during picking of a single sheet according to an example embodiment.

FIG. 4 illustrates the media, feed system of FIG. 2 during picking of multiple sheets according to an example embodiment.

FIG. 5 is an enlarged view of the media feed system of Figure numeral for according to an example embodiment.

FIG. 6 is a fragmentary perspective view of another embodiment of the printing system of FIG. 1 according to an example embodiment.

FIG. 7 is a fragmentary perspective view of a door, retard rollers and their retainers of the printing system of FIG. 6 according to an example embodiment.

FIG. 8 is another perspective view of the retard rollers and their retainers of FIG. 7 according to an example embodiment.

FIG. 9 is a sectional view of a retard roller of the printing system of FIG. 6 according to an example embodiment.

FIG. 10 is an exploded view of the retard roller of FIG. 9 with portions shown in section according to an example embodiment.

FIG. 11 is a schematic illustration of another embodiment of the printing system of FIG. 1 according to an example embodiment.

FIG. 12 is a sectional view of a retard roller of the printing system of FIG. 11 according to an example embodiment.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 schematically illustrates media interaction system 20 including media feed system 30 according to an example embodiment. As will be described hereafter, media feed system 30 of media interaction system 20 is a relatively low cost and less complex mechanism that reduces multi-picking of sheets.

Media interaction system 20 includes media input 24, media output 26, media interaction device 28, media feed system 30, actuator 32 and controller 34. Media input 24 comprises one or more structures configured for storing and positioning a stack 36 of media sheets 38 waiting to be fed to media interaction device 28 by media feed system 30. Media input 24 may comprise a tray, bin or other structure. In the example illustrated, media input 24 comprises a substantially horizontal support surface having portion that extend opposite to portions of media feed system 30. In other embodiments, media input 24 may comprise an inclined support surface.

Media output 26 comprises one or more structures for storing and containing sheets 38 after such sheets 38 have been interacted upon by media interaction device 28. Media output 26 provides access to such sheets. In one embodiment, maybe output 26 may comprise a tray, been or the like. In yet other embodiments, media output 26 may alternatively be configured to redirect such interacted upon sheets 38 to other devices for further interaction.

Media interaction device 28 comprises a device configured to interact with sheets 38. For purposes of this disclosure, the term “interact” with respect to media interaction vice 28 means a modification of sheets 38 or the reading or sensing of printing or images on such sheets. Examples of such interactions include the sheets being printed upon, folded, creased, stapled or scanned. In embodiments where media interaction device 28 is configured to print upon sheets 38, media interaction device 28 may comprise a drop-on-demand ink jet printer, an electrophotographic printer or other device is configured to form an image upon a sheet of media.

Media feed system 30 comprises an arrangement of components configured to pick individual sheets 38 from stack 36 and to initiate the transfer of such picked sheets to media interaction device 28. Media feed system 30 includes friction pad 42, pick tire 44, separation surface 46, driven roller 48, retard roller 50, feedroller 52 and idling roller 54. Friction pad 42 comprises an area configured to have a higher coefficient of friction with sheets 38 as compared to the media support surface of media input 24. Friction pad 42 extends along the media support surface provides by media input 24 and extends substantially opposite to pick tire 44. Friction pad 42 assists in separating sheets 38 from stack 36. In one embodiment, friction pad 42 comprises a pad of compressive or material such as cork. In other embodiments, friction pad 42 may comprise other materials having higher coefficient of friction with sheets 38 as compared to media input 24. In other embodiments, friction pad 42 may be omitted.

Pick tire 44 comprises a cylindrical or substantially D-shaped roller that is configured to frictionally engage a topmost sheet 38 of stack 36 while being rotationally driven to move the sheet in the direction indicated by arrow 60. In one embodiment, pick tire 44 is configured to be selectively moved into engagement or moved out of engagement with the top most sheet 38. In other embodiments, pick tire 44 may be cylindrical or may have other shapes. Although system 30 is illustrated as including a single pick tire 44, in other embodiments, system 30 may include additional pick tire 44 space along a top surface of the top of sheet 38.

Separation surface 46 comprises a vertically inclined surface configured to abut leading edges 62 of sheets 38 that are driven by pick tire 44 prior to such sheets 38 being engaged in driven by driven roller 48. In one embodiment, separation surface 46 has a coefficient of friction with such leading edges 62 such that frictional forces exerted by separation surface 46 upon the topmost sheet 38 are less than the driving four supply by pick tire 44 to the topmost sheet and such that frictional forces applied by separation surface 46 to underlying sheets 38 or greater than the driving force apply to such underlying sheets by pick tire 44 as a result of friction between the topmost sheet 38 and such underlying sheets. In such an embodiment, separation surface 46 further assists in separating the top most sheet 38 of stack 36 from underlying sheets 38 to reduce occurrences of a multi-pick. As indicated by arrow 66, sheets driven by pick tire 44 are moved up a long separation surface 46 to a downwardly facing at 68 formed by driven roller 48 and retard roller 50.

Driven roller 48 and retard roller 50 cooperate to further move the topmost sheet 38 being driven by pick tire 44 towards media interaction device 28. At the same time, driven roller 48 and retard roller 50 increase the effectiveness of system 30 at reducing the occurrence of multi-picks. Driven roller 48 comprises a roller rotationally driven by actuator 32 to drive sheets 38 along a media path. Although system 30 is illustrated as including a single driven roller 48, in other embodiments, system 30 may include multiple spaced driven rollers 48.

Retard roller 50 comprises a roller rotationally supported opposite to driven roller 48. Retard roller 50 is configured to be urged into contact with driven roller 48 in the absence of a sheet 38 between roller 48 and roller 50. Retard roller 50 is configured to frictionally engage or grip a sheet 3P, in contact with roller 50. Retard roller 50 is resiliently biased against rotation. In one embodiment, the bias applied to retard roller 50 is such that torque transmitted to retard roller 50 during rotation of driven roller 48, when driven roller 48 is in direct contact with retard roller 50 or when a single sheet 38 is positioned between and in mutual contact with both driven roller 48 and retard roller 50, is sufficient to overcome the bias. As a result, rotation of driven roller 48 in a counterclockwise direction as seen in FIG. 1 also results in rotation of retard roller 50 in a clockwise direction as seen in FIG. 1. At the same time, the bias applied to retard roller 50 is such that when a multi-pick is occurring (when two or more sheets 38 are positioned between driven roller 48 and retard roller 50), the forced transmitted from driven roller 48 to retard roller 50 through the two or more intervening sheets 38 is insufficient to overcome the bias applied to retard roller 50. The torque applied to retard roller 50 during a multi-pick is much less than the torque applied to retard roller when a single sheet 38 is being picked because of the multiple intervening sheets 38 that transmit only a small portion of the friction force from driven roller 48 due to their relative smaller media to media coefficients of friction compared with rubber roller to media coefficients of friction. In one embodiment, retard roller 50 is resiliently biased against rotation by one or more torsion springs (not shown).

Because retard roller 50 is resiliently biased against rotation, retard roller 50 applies a drag to the second sheet that is being multiple picked and that is not in contact with driven roller 48. Because retard roller 50 is in contact with controller 34 and the absence of any intervening sheets 38 and because such bias is overcome by the torque applied to driven roller 50 by driven roller 48, retard roller 50 is torsionally loaded or wound up. Upon being torsionally loaded, retard roller 50 further configured to further rotate or slip (such as with a clutch or other mechanism) without further torsional loading. As a result, single sheets 38 may be driven by driven roller 48 onward along a media path towards media interaction device 28. However, during a multi-pick, the forces exerted against retard roller 50 are insufficient to overcome the bias such that retard roller 50 torsionally unloads while in contact with the second sheet (i.e., the sheet that is not in contact with driven roller 48) to drive or kick the second sheet away from nip 68 and back towards separation surface 46. Because the leading edge 62 of the second sheet is propelled away from nip 68 and back towards separation surface 46 and media input 24, the occurrence of multi-picks may be reduced.

Feedroller 52 and idling roller 54 cooperate to further move picked sheets 38 along a media path at least partially defined by roller 52 and 54. Feedroller 52 is operably coupled to actuator 32 and is rotationally driven by actuator 32. Idling roller 54 extends opposite to feedroller 52 and is urged towards and against roller 52 to form a nip 72. Idling roller 54 is configured to freely rotate without imposing substantial drag upon a sheet 38 being driven by feedroller 52. In other embodiments, the roller 52 and idling roller 54 may be omitted.

Actuator 32 comprises a device configured to rotationally drive pick tire 44, driven roller 48 and feedroller 52. In one embodiment, actuator 32 may comprise a motor operably coupled to pick tire 44, driven roller 48 and feedroller 52 by a drive train or transmission 55 (schematically shown). Although actuator 32 is illustrated as driving each of pick tire 44, driven roller 48 and feedroller 52, in other embodiments, separate actuators may alternatively be provided.

Controller 34 comprises one or more processing units configured to generate control signals directing the operation of at least actuator 32 and of media interaction device 28. 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 34 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, or to any particular source for the instructions executed by the processing unit.

FIGS. 2-5 schematically illustrate operation of media feed system 30. FIG. 2 schematically illustrates the initiation of picking of one or more sheets 38. As shown by FIG. 2, pick tire 44 is rotationally driven in the direction indicated by arrow 76 to drive the top most sheet 38 against and upwards along separation surface 46. Prior to engagement with the top most sheet 38, driven roller 48 is also rotationally driven in a counterclockwise direction as indicated by arrow 78 while in engagement with retard roller 50. As a result, retard roller 50 is also rotationally driven in a clockwise direction as indicated by arrow 80. During such rotation, retard roller 50 is torsionally loaded or wound up until retard roller 50 begins to rotationally slip with respect to a clutch or other mechanism.

FIG. 3 schematically illustrates a first scenario in which a single top most sheet 38 is picked by pick tire 44 and is driven between nip 68. Because a single sheet 38 is in simultaneous contact with both driven roller 48 and retard roller 50, sufficient torque is transmitted from driven roller 48 to retard roller 50 by the intervening sheets 38 to continue to drive retard roller 50 against its torsional bias such that retard roller 50 continues to rotate in the clockwise direction as indicated by arrow 80. The single sheet is subsequently transferred to a nip 72 formed between feedroller 52, driven in a counterclockwise direction as indicated by arrow 82, and idling roller 54.

FIGS. 4 and 5 illustrate a second alternative scenario in which a multi-pick is taking place. As a result, both a top most sheet 38 and an underlying sheet 38 extend into nip 68 and between driven roller 48 and retard roller 50. Because the two sheets 38 between rollers 48 and 50 have lower coefficients of friction with respect to one another as compared to the coefficient of friction of such sheets with rollers 48 and 50, a lesser amount of torque is transmitted from driven roller 48 across the intervening sheets 38 to retard roller 50. This lesser force is insufficient to overcome the bias of retard roller 50. As a result, retard roller 50 torsionally unloads or unwinds by rotating in a counterclockwise direction as indicated by arrow 84. Consequently, as seen in FIG. 5 and as indicated by arrow 86, retard roller 50 drives or propels the leading edge 62 of the underlying sheet 38 in contact with retard roller 50 back towards separation surface 46 (shown in FIG. 4) and out of nip 68. Meanwhile, driven roller 48 continues to drive the top most sheet 38 along the media path as indicated by arrow 88. Once the underlying sheet 38 has been driven out of nip 68 and retard roller 50 has moved into contact with the top most sheet 38, a greater amount of torque is once again transmitted from driven roller 48 to retard roller 50 through the single intervening sheet 38. This larger amount of torque is once again sufficient to overcome the bias of retard roller 50 just to rotate retard roller 50 and a clockwise direction and to torsionally load retard roller 50 once again as described above with respect to FIG. 3.

Overall, media feed system 30 provides a relatively low-cost and less complex system for effectively separating sheets of a multi-pick. Because system 30 includes an inclined separation surface 46 in conjunction with retard roller 50, separation of sheets is enhanced. For example, underlying sheets driven out of nip 68 by retard roller 50 during a first pick that still underlie another top most sheet 38 during a subsequent pick may once again have to overcome the separation force provided by separation surface 46 prior to even reaching nip 68 during a subsequent pick. In addition, because nip 68 opens or faces in a substantially downward or declined direction, retard roller 50 additionally uses the assistance of gravity in expelling the underlying multi-pick sheet from nip 68. As a result, the multi-picked underlying sheet 38 may be driven a farther distance from nip 68 reducing the likelihood of a subsequent multi-pick with the same sheet.

FIG. 6 illustrates media interaction system 120, another embodiment of media interaction system 20. Media interaction system 120 is similar to media interaction system 20 in that media interaction system 120 includes media feed system 130, a particular example of media feed system 30. In addition to media feed system 130, media interaction system 20 includes media input 24, housing 125, a portion of which is shown in FIG. 6, media output 26 (schematically shown in FIG. 1), media interaction device 28, actuator 32 and controller 34, each of which is schematically shown and described with respect to FIG. 1.

Housing 125 at least partially encloses remaining components of media interaction 120. As shown by FIG. 6, housing 125 includes an exterior wall 126 in which is disposed a removable door 127. Door 127 is configured to be removed from wall 126 to provide access to the media feed path adjacent to media feed system 130. Removal of door 127 facilitates clearing of media jams or other issues. In one embodiment, door 127 is fastened to wall 126, wherein removal of the fasteners from its door 127 to be withdrawn. In another embodiment, door 127 may be pivoted between an open state and a closed state. As will be described in more detail hereafter, door 127 carries portions of media feed system 130, and enhancing compactness of media interaction system 120.

Media feed system 130 includes friction pad 142, pick tires 144, separation surfaces 146 (one of which is shown), driven roller 148, retard roller retainers 149, retard rollers 150, feedroller 52 (shown in FIG. 1) and idling roller 54 (shown in FIG. 1). Feedroller 52 and idling roller 54 are omitted from FIG. 6 for purposes of illustrating retard roller 50. Friction pad 142 is similar to friction pad 42 of system 30 shown in FIG. 1. Friction pad 142 comprises an area configured to have a higher coefficient of friction with sheets 38 (shown in FIG. 1) as compared to the media support surface of media input 124. Friction pad 142 extends along the media support surface provides by media input 124 and extends substantially opposite to pick tires 144. Friction pad 142 assists in separating sheets 38 from stack 36 (shown in FIG. 1). In one embodiment, friction pad 142 comprises a pad of compressive or material such as cork. In other embodiments, friction pad 142 may comprise other materials having higher coefficient of friction with sheets 38 as compared to media input 124. In other embodiments, friction pad 142 may be omitted.

Pick tires 144 comprises cylindrical or substantially D-shaped rollers that are configured to frictionally engage a top most sheet 38 of stack 36 while being rotationally driven to move the sheet towards separation surface 146. In the embodiment illustrated, pick tires 144 are supported by an arm 153 that is pivotally supported by housing 125 and may be pivoted by an actuator (not shown) to selectively move tires 144 into engagement or out of engagement with the top most sheet 38. Although system 130 is illustrated as including a pair of pick tires 144, in other embodiments, system 130 may include greater or fewer pick tires 44 spaced along a top surface of the top of sheet 38.

Separation surface 146 comprises a vertically inclined surface configured to abut leading edges of sheets 38 that are driven by pick tires 144 prior to such sheets 38 being engaged in driven by driven roller 48. In one embodiment, separation surface 146 has a coefficient of friction with such leading edges 62 such that frictional forces exerted by separation surface 46 upon the topmost sheet 38 are less than the driving force supplied by pick tire 44 to the topmost sheet and such that frictional forces applied by separation surface 146 to underlying sheets 38 are greater than the driving force apply to such underlying sheets by pick tires 144 as a result of friction between the topmost sheet 38 and such underlying sheets. In such an embodiment, separation surface 146 further assists in separating the top most sheet 38 of stack 36 from underlying sheets 38 to reduce occurrences of a multi-pick. According to one embodiment, separation surface 146 includes a multitude of teeth configured to resist movement of another line multi-pick sheet. In other embodiments, separation surface146 may have other configurations.

Driven roller 148 comprises a plurality of rollers supported by a shaft opposite to retard rollers 150. Driven roller 48 is configured to be rotationally driven by actuator 32 (shown in FIG. 1) to drive and turn a sheet of media further along a media feed path. In one embodiment, driven roller 48 includes four spaced rollers, each roller positioned opposite to the corresponding four retard rollers 150. In other embodiments, driven roller 48 may comprise a single roller, against which each of retard rollers 150 are urged.

Retard roller retainers 149 pivotally support retard rollers 150 with respect to driven roller 148 and resiliently bias each of retard rollers 150 towards driven roller 148. FIGS. 6 and 7 illustrate retainers 149 in more detail. As shown by FIGS. 6 and 7, retainers 149 each include an arm 157 and a resilient bias 159. As shown by FIG. 6, each support arm supports a retard roller 150 and is pivotally connected to door 127 at another end. In the example illustrated, each arm 157 includes an opening 161 rotationally receiving a pin, shaft or axle 163 projecting from door 127. In the particular example illustrated, each arm 157 is at least partially received within a corresponding cavity 165 provided by door 127. As a result, arms 157 do not substantially increase the volume of media interaction system 120.

Biases 159 comprise spring mechanisms configured to resiliently bias arms 157 and retard rollers 150 towards driven roller 148. In the particular example illustrated, biases 159 comprise compression springs captured between arms 157 and door 127. In other embodiments, biases 159 may comprise other spring mechanism such as torsion springs, tension springs or leaf springs arranged to cooperate between arms 157 and door 127 to resiliently bias arms 157 and rollers 150 towards driven roller 148. Because retard rollers or 150 are supported and carried by door 127, retard rollers 150 may be mounted in the door 127 in place of idling rollers, reducing an extent to which an existing printing system architecture or housing would be modified to accommodate retard rollers 150. In addition, the provision of retard rollers 150 does not add significant cost, space or complexity to media interaction system 120.

Retard rollers 150 cooperate with driven roller 148 to reduce multi-picks. Each retard roller 150 comprises a roller rotationally supported opposite to driven roller 148 by a corresponding support arm 157. Retard rollers 150 are configured to frictionally engage or grip a sheet 38 in contact with roller 50. Retard rollers 50 are resiliently biased against rotation. In one embodiment, the bias applied to retard rollers 50 is such that torque transmitted to retard rollers 50 during rotation of driven roller 148, when driven roller 148 is in direct contact with retard roller 150 or when a single sheet 38 is positioned between any mutual contact with both driven roller 148 and retard rollers 50, is sufficient to overcome the bias. As a result, rotation of driven roller 148 in a counterclockwise direction as seen in FIG. 1 also results in rotation of retard rollers 150 in a clockwise direction as seen in FIG. 1. At the same time, the bias applied to retard rollers 150 is such that when a multi-pick is occurring (when two or more sheets 38 are positioned between driven roller 148 and retard rollers 150), the forced transmitted from driven roller 148 to retard rollers 150 through the two or more intervening sheets 38 is insufficient to overcome the bias applied to retard roller 150. The torque applied to retard roller 150 during a multi-pick is less than the torque applied to retard roller when a single sheet 38 is being picked because of the multiple intervening sheets 38 that transmit only as portion of the force from driven roller 48 due to their relative lower coefficient of friction. In one embodiment, each of retard rollers 150 is resiliently biased against rotation by one or more torsion springs (not shown).

Because retard rollers 150 are resiliently biased against rotation, retard rollers 150 apply a drag to the second sheet that is being picked and that is not in contact with driven roller 148. Because retard roller 150 are in contact with roller 148 in the absence of any intervening sheets 38 and because such bias is overcome by the torque applied to retard rollers 150 by driven roller 148, retard rollers 150 are torsionally loaded or wound up. Upon being torsionally loaded to a predetermined amount, retard rollers 150 are further configured to further rotate or slip (such as with a clutch or other mechanism) without further torsional loading. As a result, single sheets 38 may be driven by driven roller 148 onward along a media path towards media interaction device 28. However, during a multi-pick, the forces exerted against retard roller 50 are insufficient to overcome the bias such that retard rollers 150 torsionally unload or unwind while in contact with the second sheet (i.e., the sheet that is not in contact with driven roller 148) to drive or kick the second sheet away from nip 168 and back towards separation surface 146. Because the leading edge 62 of the second sheet is propelled away from nip 168 and back towards separation surface 146 and media input 24, the occurrence of multi-picks may be reduced.

FIGS. 9 and 10 illustrate one of retard rollers 150 in detail. Retard roller 150 includes shaft 200, interior clutch member 204, clutch spring 206, hub 208, tire 210 and spring 212. Shaft 200 extends through clutch member 204 and hub 208 and has ends secured to arm 157 (shown in FIG. 6). In the particular example illustrated, shaft 200 has at least one noncircular end 214 received within arm 157 (as shown in FIGS. 7 and 8) to inhibit rotation of shaft 200. Shaft 200 rotationally supports clutch member 204 and hub 208 about axis 218. In other embodiments, shaft 200 may be connected to arm 157 in other fashions such that shaft 200 is secured against rotation.

Interior clutch member 204 comprises a structure rotationally positioned about shaft 200 within hub 208. As shown by FIG. 10, member 204 includes a key 220 axially projecting on one end of member 204. As will be described hereafter, key 220 cooperates with hub 208 to limit an extent to which hub 208 may rotate with respect to member 204 without also rotating member 204 so as to provide a preset limit to which spring 212 may be torsionally loaded to potentially extend the useful life of spring 212. Although illustrated as a tab, key 220 may have other configurations.

Clutch spring 206 comprises a torsion spring encircling shaft 200 and having an end 226 connected to clutch member 204 and the other end is free. Spring 206, when in a relaxed state, has an inner diameter less than or equal to an outer diameter of shaft 200. When in a relaxed state, spring 206 constricts about shaft 200 such that friction between spring 206 and shaft 200 inhibit relative rotation of spring 206 and shaft 200 about axis 218. When in a relaxed state, spring 206 also restricts rotation of clutch member 204 about axis 218. Spring 206 is further configured such that transmission of a sufficient torque to clutch member 204 and to spring 206 results in unwinding or expansion of spring 206 (increase its inner diameter), permitting spring 206 and clutch member 204 to rotate relative to shaft 200 with certain drag torque. In the particular example illustrated, spring 206 is provided with a spring constant greater than the spring constant of spring 212, spring 212 may be wound or unwound with respect to its relaxed state with a force less than a force that would wind or unwind spring 206.

Hub 208 comprises a structure rotationally supported about axis 218 and configured to rigidify and support tire 210. Hub 208 further includes an interior cavity 224 receiving clutch member 204 and spring 212, enhancing compactness of retard roller 150. As shown by FIG. 10, hub 208 includes a pair of shoulders or steps 228 separated by an intermediate circumferential gap 230. Gap 230 receives key 220. Steps 228 are configured to abut key 220 so as to limit rotation of key 220 past such steps 228. Steps 228 cooperate with key 220 to limit the extent to which hub 208 and tire 210 may be additionally rotated about axis 218 relative to clutch member 204 during torsional loading of spring 212. Once clutch member 204 begins to rotate with hub 208 upon engagement of key 220 and one of the steps 228, torsional loading of spring 212 is stopped. As a result, steps 228 provide a preset limit to which spring 212 may be torsionally loaded, providing greater control over the operation of retard roller 150.

In one embodiment, steps 228 are angularly spaced from one another by about 141 degrees which will give 102 degree of relative rotation between clutch member 204 and hub 208 because of the width of key 220. In other embodiments, the spacing may be varied depending upon specific characteristics of spring 212. In still other embodiments, the relationship between steps 228 and key 220 may be reversed. In particular, hub 208 may alternatively include key 220 while clutch member 204 alternatively includes steps 228 and gap 230.

Tire 210 comprises one or more layers of one or more materials configured to frictionally engage a sheet of media. Tire 210 is supported about axis 218 by hub 208. In one embodiment, tire 210 comprises a layer of a resiliently compressible material, such as rubber. In other embodiments, tire 210 may comprise other compressible materials. In some embodiments, tire 210 may additionally include surface texturing, ridges, grooves, dimples or the like to enhance a coefficient of friction between an outer surface of tire 210 and a sheet of media being contacted and gripped by tire 210. In yet other embodiments, tire 210 may be omitted, wherein hub and 208 is configured to frictionally engage and contact a sheet of media.

Spring 212 comprises a torsion spring extending about shaft 200 within cavity 224. Spring 212 has a first end 232 connected to hub 208 and a second end 234 connected to clutch member 204. In the particular embodiment illustrated, spring 212 is configured to be wound up when being rotated in a first direction during torsional loading of spring 212, whereas spring 206 is configured to be unwound when rotated in the same first direction. As a result, cavity 224 may be reduced in size, decreasing the size of retard roller 150. In other embodiments, spring 212 may alternatively be unwound during torsional loading. In the particular embodiment illustrated, spring 212 is configured so as to experience minimal or no frictional resistance from either shaft 200 or hub 208. Spring 212 is provided with a spring constant less than a spring constant of spring 206. As a result, spring 212 may be torsionally loaded while clutch member 204 is held against rotation by spring 206.

In operation, in the absence of a sheet between retard roller 150 and driven roller 148 such that driven roller 148 is in engagement with tire 210 or wherein a single sheet is in concurrent contact with both driven roller 148 and tire 210 retard roller 150 is driven by torque provided by driven roller 148. During such rotation, hub 208 rotate about axis 218 relative to clutch member 204 which is held against rotation by clutch spring 206. At the same time, rotation of hub 208 further winds spring 212 to torsionally load spring 212. Once step 228 is rotated into abutment with key 220, hub 208 the longer rotates relative to clutch member 204 such that torsional loading of spring 212 is stopped. Thereafter, rotation of hub 208 transmits torque to clutch member 204 to a sufficient extent such that clutch member 204 overcomes the resistance provided by clutch spring 206 to unwind clutch spring 206. Unwinding of clutch spring 206 decreases frictional engagement between clutch spring 206 and shaft 200, permitting clutch member 204 and a remainder of retard roller or 152 more freely rotate about shaft 200 and axis 218.

When a multi-pick is occurring such that two or more sheets are positioned between driven roller 148 and retard roller 150, torque transmitted to retard roller 150 is dependent upon a coefficient of friction between each of the multiple intervening sheets. As a result, torque received by retard roller 150 from driven roller 148 is substantially reduced. Spring 212 is configured such that the force transmitted to retard roller 150 is less than the counter rotational force provided by spring 212. As a result, spring 212 torsionally unloads to hub 208 and tire 210 in a direction so as to drive the sheet in contact with tire 210 in a backwards direction towards separation surface 146 (shown in FIG. 6) and out of the nip between driven roller 148 and retard roller 150.

FIG. 11 illustrates portions of media interaction system 320, another embodiment of printing system 20. Media interaction system 320 is similar to printing system 20 except that media interaction system 320 includes retard roller 350 in lieu of retard roller 50 and additionally includes brake 351. Those remaining elements of media interaction system 320 which correspond to elements of printing system 20 are numbered similarly.

Retard roller 350 comprises one or more rollers resiliently biased against rotation. FIG. 12 illustrates the retard roller 350 in detail. As shown by FIG. 12, retard roller 350 is similar to retard roller 150 except that retard roller 350 omits clutch spring 206 and includes shaft 400 and key support 404 in lieu of shaft 200 and clutch member 204, respectively. Those remaining elements of retard roller 350 which correspond to end are substantially similar to elements of retard roller 150 are numbered similarly.

Shaft 400 comprises an elongate shaft extending through hub 208 and configured to rotationally support hub 208. Shaft 400 is rotationally supported for rotation about axis 418. One end of shaft 400 is operably coupled to brake 351.

Key support 404 comprises a structure connected to shaft 400 so as to rotate with shaft 400. In one embodiment, key support 404 may be fastened, bonded, welded or otherwise affixed to shaft 400. In other embodiments, support 404 may be integrally formed as a single unitary body with shaft 400. Key support 404 includes key 220 shown and described above with respect to FIG. 8. Key 220 of key support 404 functions identical to key 220 of clutch member 204. In particular, key 220 cooperates with steps 228 and 230 (shown in FIG. 8) of hub 208 to limit the extent to which spring 212 is loaded.

Brake 351 comprises an adjustable and controllable braking mechanism operably coupled to shaft 400. Brake 351 brakes or retards rotation of shaft 400. Brake 351 applies an adjustable braking force to shaft 400 based upon control signals received from controller 34 (shown in FIG. 9). According to one embodiment, controller 34 generates control signals such that brake 351 brakes rotation of shaft 400 such that shaft 400 does not rotate or rotates slower as compared to rotation of hub 208 when retard roller 350 is being driven by driven roller 48 until key 220 engages one of steps 228 (shown in FIG. 10). Brake 351 is controlled such that further transmission of torque to shaft through tire 210, hub 208 and key support 404 is sufficient to overcome the braking resistance provided by brake 351 when driven roller 48 is in direct contact with tire 210 or when a single sheet is between driven roller 48 and tire 210.

In one embodiment, media interaction system 320 additionally includes a sensor 421 operably coupled to brake 351 or shaft 400 to detect when shaft 400 starts to rotate. In response to receiving signals indicating that shaft 400 has begun to rotate, controller 34 may be additionally configured to generate control signals decreasing the braking force supplied by brake 351 at an enhanced rate to quickly reduce the amount of braking resistance provided by brake 351. As a result, driven roller 48 experiences a controlled and substantially smaller resistance, reducing an amount of torque used to drive driven roller 48. In such an embodiment, controller 34 may additionally be configured to generate control signals directing brake 351 to increase the braking resistance applied by brake 351 to shaft 400 upon receiving signals from one or more sensors (not shown) indicating that a sheet has left the nip between driven roller 48 and retard roller 350. In other embodiments, sensor 421 may be omitted.

According to one embodiment, brake 351 may comprise a magnetic brake. In other embodiments, brake 351 may comprise other brakes which provide an adjustable or controllable braking force in response to control signals from controller 34.

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.

RETARD ROLLER

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