WO2017099741A1

WO2017099741A1 - Eject a stack of media sheets

Info

Publication number: WO2017099741A1
Application number: PCT/US2015/064650
Authority: WO
Inventors: Bruce G. Johnson; Anthony W. Ebersole; Elliott DOWNING; Steve O. Rasmussen
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2015-12-09
Filing date: 2015-12-09
Publication date: 2017-06-15

Abstract

A printing system for ejecting a stack of media sheets to an output tray includes a shelf to receive a leading edge of the stack of media sheets. The printing system also includes a clamp module to secure the leading edge of the stack of media sheets between a number of fingers of the clamp module and the shelf to retain the media sheets of the stack of media sheets in a registered state.

Description

EJECT A STACK OF MEDIA SHEETS

BACKGROUND

[0001] Printing and copying devices are used to produce physical copies of documents. The printing or copying device produces images and text on media sheets based on data input to the printing or copying device. In some examples, the printing and copying devices output the printed media sheets to an output tray so that a user may obtain the printed media sheets from a common output area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are a part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

[0003] Fig. 1 is a block diagram of a printing device including an output tray, according to one example of the principles described herein.

[0004] Fig. 2 is a top view of the output tray of Fig. 1 , according to one example of the principles described herein.

[0005] Fig. 3 is an isometric view of the output tray of Fig. 2, according to one example of the principles described herein.

[0006] Fig. 4 is an isometric view of a clamp module of the output tray of Fig. 2, according to one example of the principles described herein.

[0007] Fig. 5 is a front view of the clamp module of the output tray of Fig. 2, according to one example of the principles described herein. [0008] Fig. 6 is a side view of the output tray of Fig. 2, according to one example of the principles described herein.

[0009] Fig. 7 is a flowchart showing a method of ejecting a stack of media sheets from a printing device, according to one example of the principles described herein.

[0010] Fig. 8 is a flowchart showing a method of ejecting a number of media sheets from a printing device, according to another example of the principles described herein.

[0011] Fig. 9 is a front view of the shelf and fingers of the clamp module of the output tray of Fig. 2, according to one example of the principles described herein.

[0012] Fig. 10 is a front view of the fingers of the clamp module of the output tray of Fig. 2, according to another example of the principles described herein.

[0013] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.

DETAILED DESCRIPTION

[0014] As mentioned above, printing and copying devices, collectively referred to herein as printing devices, output printed media sheets to a common output tray or other output area. However, in many instances, the printing device outputs the media sheets in a non-registered or non-aligned manner. A user who receives the printed media sheets from the output tray in such a non- registered state is then forced to either register the media sheets himself by hand, or present the non-registered media sheets as an arguably less professional and unpresentable finished product.

[0015] Further, in some printing devices such as, for example, inkjet printing devices, where a deposited ink or other fluid creates curl in the print media, registering of the print media and finishing of the stacks may prove difficult. This may be due to a finishing tray's inability to align print media that is not flat. Further, performing a finishing process on the print media such as a stapling process is difficult due to the curling of the print media at, for example, the corners of the print media where a staple is stapled into the print media.

[0016] Registration of the media sheets before presentation to a user in an output tray of the printing device produces a superior, more professional finished product. In the examples described herein, a printing device registers media sheets as they are output from the printing device, and maintains the registration of the media sheets before, during, and after a finishing process. A finishing process may include, for example, a stapling process, a hole punching process, a binding process, offset stacking of both stapled and unstapled stacks, other finishing processes, or combinations thereof.

[0017] Therefore, examples described herein provide a printing system for ejecting a stack of media sheets to an output tray includes a shelf to receive a leading edge of the stack of media sheets. The printing system also includes a clamp module to secure the leading edge of the stack of media sheets between a number of fingers of the clamp module and the shelf to retain the media sheets of the stack of media sheets in a registered state. The printing system includes a number of mezzanines to support the stack of media sheets. The mezzanines are moveable out of underneath the stack of media sheets to allow a first end of the stack of media sheets to fall to an output floor. The clamp maintains pressure on the stack of media sheets when a trailing end of the stack of media sheets reaches the output floor. Pressure may be exerted by the clamp on the stack of media sheets to secure the leading edge of the stack of media sheets. The pressure may be based at least partially on a height of the stack of media sheets.

[0018] The printing system may further include a number of articulating extension bars coupled to the mezzanines, and a number of extension arms coupled to the extension bars to articulate the extension bars away from the mezzanines, the extension bars supporting the stack of media sheets. The extension arms retract the extension bars towards the mezzanines as the mezzanines move out of underneath the stack of media sheets to allow a first end of the stack of media sheets to fall to an output floor. Extension bars may be included to provide additional support between the mezzanines [0019] Further, examples described herein also provide a clamp for ejecting a stack of media sheets from a printing device. The clamp includes a shelf on which a number of media sheets are accumulated. The accumulated media sheets form a stack of media sheets. A number of clamp fingers secure the stack of media sheets against the shelf. The shelf tilts or pivots away from the clamp fingers independent of the movement of the fingers during a drop of the stack of media sheets to a floor of the output tray. In one example, at least one finger is included in the clamp. In another example, the fingers may include two fingers that operate with lost motion to exert an approximately identical pressure on different areas of the stack of media sheets. In another example, lost motion is not used. In still another example, lost motion may be used to utilize air trapped between successive media sheets to push the media sheets toward a number of X registration devices by closing a plurality of fingers of a clamp module in a sequential manner.

[0020] Still further examples described herein provide a method of ejecting a stack of media sheets from a printing device. The method includes engaging a clamp to grab a number of registered media sheets comprising a print job, the media sheets forming a stack, and evaluating a height of the stack of media sheets to determine a pinch force. The stack of media sheets may be pinched using the clamp based on the determined pinch force. Further, the method may include moving a number of support mezzanines from under the stack of media sheets to allow a first end of the stack of media sheets to fall to an output floor, and disengaging the clamp to allow a second end of the stack of media sheets to fall to the output floor.

[0021] The method may further include determining if a finishing process has been requested. In response to a determination that a finishing process has been requested, the method may include performing the finishing process, and maintaining registration of the media sheets within the stack of media sheets. The finishing processes may include, stapling, hole punching, binding, saddle stitching, folding, offsetting of stapled stacks, offsetting of unstapled stacks, other finishing processes, or combinations thereof. Performing the finishing process, and maintaining registration of the media sheets within the stack of media sheets includes lifting a number of fingers of the clamps a partial amount based on the height of the stack of media sheets to maintain the registration of the media sheets. The performance of the finishing process, and the maintaining of the registration of the media sheets within the stack of media sheets may also include aligning the stack of media sheets with a finishing device, performing the finishing process, and opening the clamp to allow the finished media sheets to be moved to a drop position.

[0022] In one example, aligning the stack of media sheets with the finishing device includes moving the stack of media sheets with the mezzanines to align with the finishing device. In another example, aligning the stack of media sheets with the finishing device includes moving the finishing device to align with the stack of media sheets on the mezzanines.

[0023] As used in the present specification and in the appended claims, the terms "register" or "registration" are meant to be understood broadly as adjustment to a plurality of media sheets so as to secure exact correspondence among the plurality of media sheets. In one example, a number of media sheets may be accumulated in connection with a print job processed by a printing or copying device. The accumulated media sheets may be registered in preparation for a stapling process, a hole punching process, a binding process, other finishing processes, or combinations thereof. Further, in another example the media sheets may simply be accumulated and registered in order to present the media sheets to a user of the printing or copying device in an orderly and aligned state. In this example, an unfinished stack of print media such as an unstapled stack may be presented in an aligned manner. In still another example, the media sheets may include a number of physical elements such as punched holes that a user may wish to be aligned in order to place the media sheets in, for example, a three-ring binder. Registration of the media sheets performed by the printing or copying device assists in these processes.

[0024] As used in the present specification and in the appended claims, the terms "finish" or "finishing process" are meant to be understood broadly as any process applied to an accumulated number of media sheets. Examples of finishing processes may include stapling, hole punching, binding, saddle stitching, folding, offsetting of stapled stacks, offsetting of unstapled stacks, other finishing processes, or combinations thereof.

[0025] Even still further, as used in the present specification and in the appended claims, the term "a number of" or similar language is meant to be understood broadly as any positive number comprising 1 to infinity; zero not being a number, but the absence of a number.

[0026] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present systems and methods. The present apparatus, systems, and methods may be practiced without these specific details. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described in connection with that example is included as described, but may not be included in other examples.

[0027] Turning now to the figures, Fig. 1 is a block diagram of a printing device (100) including an output tray (121 ), according to one example of the principles described herein. The printing device (100) may include a print bar (105) that, in one example, spans the width of a print media (1 10). In another example, the printing device (100) may include non-page wide array printheads. The printer (100) may further include flow regulators (1 15) associated with the print bar (105), a media transport mechanism (120), ink or other ejection fluid supplies (125), and a printer controller (130).

[0028] The controller (130) may represent the programming,

processor(s), associated data storage device(s), and the electronic circuitry and components used to control the operative elements of a printer (100) including the firing and operation of the printheads (135) included in the print bar (105). Further, the controller (130) controls the media transport mechanism (120) used to transport media through the printing device (100) during printing and to transport the media sheets to the output tray (121 ). In one example, the controller (130) may control a number of functions of the output tray (121 ) as will be described in more detail below. The media transport mechanism (120) may transport media sheets from the printing device to the output tray (121 ) for collection, registration, and, in some examples, finishing of the media sheets. In one example, the media sheets collected in the output tray (121 ) include at least one media sheet on which the printing device has produced text and/or images. In one example, a completed collection of media sheets may represent a print job that the printing device processes.

[0029] The output tray (121 ) as depicted in Fig. 1 will now be described in connection with Figs. 2 through 6. Fig. 2 is a top view of the output tray (121 ) of Fig. 1 , according to one example of the principles described herein. Fig. 3 is an isometric view of the output tray (121 ) of Fig. 2, according to one example of the principles described herein. Fig. 4 is an isometric view of a clamp module (201 ) of the output tray (121 ) of Fig. 2, according to one example of the principles described herein. Further, Fig. 5 is a front view of the clamp module (201 ) of the output tray (121 ) of Fig. 2, according to one example of the principles described herein. Fig. 6 is a side view of the output tray (121 ) of Fig. 2, according to one example of the principles described herein. Throughout Figs. 2 through 6, a three-dimensional Cartesian coordinate indicator (280) shown in Figs. 2-6 is provided to orient the reader as to directions of movement and forces placed on and interaction between the various elements within the output tray (121 ) of the printing device (100). Throughout the figures, a circle located at the origin of the coordinate indicator indicates that the positive direction is moving or coming out of the page toward the reader. Conversely, a square indicates that the positive direction is moving away from the reader or, in other words, moving into the page away from the reader.

[0030] As depicted in Figs. 2 through 6, the output tray (121 ) includes a housing (255) used to house a number of elements and to support those elements within the housing (255). The housing (255) supports a shelf (203) and a number of mezzanines (204). In the examples described herein, two mezzanines (204) are included. However, the output tray (121 ) may include any number of mezzanines (204). The shelf (203) and mezzanines (204) form a mezzanine level located above an output floor (207) in the positive Z direction as indicated by the Cartesian coordinate indicator (280). The mezzanine level serves as a preliminary media sheet accumulation area within the output tray (121 ). [0031] In one example, after a number of sheets of media are

accumulated at the mezzanine level on the shelf (203) and mezzanines (204) and, once a desired finishing process such as a stapling process has completed, the mezzanines (204) separate from one another in the positive and negative X directions. In other words, the mezzanines (204) move away from the center of the output tray (121 ) allowing for the accumulated media sheets to drop to the output floor (207). Other elements within the output tray (121 ) are used to maintain registration of the accumulated media sheets and finish the accumulated media sheets. These elements will now be described in more detail.

[0032] In the examples described herein, the media sheets that are accumulated on the shelf (203) and mezzanines (204) of the mezzanine level may be referred to as a stack (250) or a stack of media sheets. A stack (250) of media sheets may include at least one media sheet. In another example, a stack (250) of media sheets includes at least two media sheets. In one example, a completed stack (250) of media sheets represents a print job that has been completed by the printing device (100) and output to the output tray (121 ) a media sheet at a time. Once completed, the print job may be subjected to a finishing process, and may be moved to the output floor (207) for consumption by the user as will be described in more detail below. In this manner, the printing device (100) may collate the media sheets of a print job, and accumulate the collated print job on shelf (203) and mezzanines (204) of the mezzanine level for further processing. The stack (250) of media sheets is depicted in Fig. 1 using a hashed box that is transparent in order to allow the other elements of the output tray (121 ) to be visible.

[0033] The output tray (121 ) includes a clamp module (201 ). The clamp module (201 ) includes a number of fingers (202) that move in the positive and negative Z direction as depicted in Figs. 2 through 6 and as indicated by arrow B in Fig. 4. The fingers (202) are used to apply a force to a number of media sheets that accumulate on the shelf (203) and mezzanines (204) of the mezzanine level. In one example, the fingers (202) secure a stack (250) of media sheets as the media sheets are output from the printing device (100) into the output tray (121 ). In this example, the fingers (202) may engage and disengage the stack (250) of media sheets as the media sheets are introduced into the output tray (121 ). In this manner, the fingers (202) lift up in the positive Z direction to accept a new media sheet within a print job, and move down in the negative Z direction to again engage the stack (250) after each new media sheet is accumulated in the stack (250).

[0034] The shelf (203) and the clamp module (201 ) serve to reference the media sheets within the stack (250) with respect to one another. The shelf (203) includes a first substrate (208) that exists in the X,Y plane. A number of friction elements (213) are disposed on the substrate (208) of the shelf (203). The friction elements (213) are made of a material with a relatively higher coefficient of friction than surrounding elements. In one example, the friction elements (213) are made of cork, and may be presented in the form of cork pads coupled to the shelf (203). The friction elements (213) limit motion of a first sheet within a plurality of sheets within a stack (250). In this manner, the first sheet within the stack (250) remains stationary against the shelf (103) due to the higher coefficient of friction of the friction elements (213) relative to the surrounding surfaces such as the first substrate (208) and second substrate (209). Subsequent media sheets that are added to the stack (250) above the first media sheet are also held in place due to the registration of the subsequent media sheets with the first media sheet.

[0035] A second substrate (209) exists in the X,Z plane as depicted in Figs. 4 and 5. The first substrate (208) and second substrate (209) provide reference locations for the media sheets as they are introduced to the output tray (121 ) and accumulated on the shelf (203) and mezzanines (204). In this example, a series of rollers or other media sheet deposition elements deposit the media sheets such that the registration of the media sheets and the stack (250) is achieved against the first substrate (208), second substrate (209), and third substrate (210). In this manner, the stack (250) of media sheets is registered in the Y direction.

[0036] In one example, the stack (250) may also be registered in the X direction using a number of X registering devices (21 1 ) as depicted in Fig. 3, for example. In this example, the X registering device (21 1 ) is coupled to and moves with the mezzanine (204) to contact the stack (250) to register the stack (250) in the X direction. Movement of the mezzanines (204) will be described in more detail below. Reference will now be made to Fig. 9 in connection with the registration of the media sheets within a stack (250). Fig. 9 is a front view of the shelf (203) and fingers (202) of the clamp module (201 ) of the output tray (121 ) of Fig. 2, according to one example of the principles described herein. The media sheets are introduced into the output tray (121 ) one at a time after each media sheet is printed or copied. As the media sheets are introduced into the output tray (121 ), the first media sheet and any subsequent media sheet has an amount of air build around each media sheet as they fall to the shelf (203) and mezzanines (204). Further, an amount of air builds between successive media sheets. This trapped air is depicted in Fig. 9 as a wedge of trapped air (901 ) present for a time between two successive media sheets. As a media sheet is deposited, the air wedge (901 ) serves to assist the fingers (202) in forcing the newly-introduced media sheet (904) against the X registering devices (21 1 ) as depicted in Figs. 3 and 9.

[0037] In one example, the fingers (202-1 , 202-2) are able to move independent of one another. This allows the fingers (202-1 , 202-2) to assist in forcing the newly-introduced media sheet (904) towards the X registering device (21 1 ) in the positive X direction. In this example, a first finger (202-1 ) and a second finger (202-2) clamp down on or move toward the newly-introduced media sheet (904) at different rates such that the first finger (202-1 ) is located relatively higher with respect to the Z direction than the second finger (202-2) by distance D. This sequential activation or lowering of the fingers (202-1 , 202-2) causes the newly-introduced media sheet (904) to move in the direction of arrow 902) as the wedge of trapped air (901 ) escapes from in between the newly- introduced media sheet (904) in the direction of arrow 903. The newly- introduced media sheet (904) then lays flat on the stack (250) of media sheets and is held there using the fingers (202-1 , 202-2). Thus, when the clamping module (201 ) closes the fingers (202), the lost motion and sequential activation or lowering of the fingers (202-1 , 202-2) may be used to control and manage the wedge of trapped air (901 ) between the media sheets.

[0038] The fingers (202-1 , 202-2) may move independent of one another using a lost motion system and a servo-mechanical control or other mechanical design as mentioned above. The lost motion may be used to utilize air trapped between successive media sheets to push the media sheets toward a number of X registering devices (21 1 ) by closing a plurality of fingers of a clamp module in a sequential manner. This asymmetric positioning creates a slope in the newly- introduced media sheet (904). In this example, the second finger (202-2) may include a lower degree of lost motion within its movements so that it responds relatively quicker to an instruction to move than the first finger (202-1 ) does. In this manner, the first finger (202-1 ) trails to the movement of the second finger (202-2). The asymmetric movement of the fingers (202-1 , 202-2) is useful in instances where registration in the X-direction is accomplished at least in part by the use of the X registering devices (21 1 ). The wedge of trapped air (901 ) preserves alignment by preventing the newly-introduced media sheet (904) from drifting away from a number of registration surfaces including the X registering devices (21 1 ) and the first substrate (208) and second substrate (209) of the shelf (203). This wedge of trapped air (901 ) may also be used to bias the newly-introduced media sheet (904) from a non-registered position to a registered position.

[0039] Turning again to Fig. 2, the fingers (202) of the clamp module (201 ) also act to maintain registration of the media sheets within the stack (250) in the X and Y directions by pinching the stack (250) before, during, and after a finishing process, deposition of the stack (250) onto the output floor (207), or a combination thereof. With regard to maintaining registration in the Y direction during a finishing process, the fingers (202) of the clamp module (201 ) pinch the stack (250) before, during, and after the finishing process. In this example, the printing device (100) may be instructed to, for example, staple the accumulated stack (250).

[0040] In one example of maintaining registration in the Y direction during a finishing process, the fingers (202) of the clamp module (201 ) are opened. In this example, the fingers (202) acts as a ceiling height to control the stack (250) while the mezzanines (204) move the stack (250) to a stapling mechanism in, for example, the negative X direction. The clamp module (201 ) again clamps the stack (250) when the stack (250) is positioned for the finishing process in order to ensure that the registration of the stack (250) is maintained through the finishing process. After the finishing processes is performed, the mezzanines (204) move back to their original position, and the clamp module resets and again maintains the registration of the stack (250) by moving the fingers (202) to clamp the stack (250). In another example, the clamp module (201 ), the shelf (203), and the mezzanines (204) remain stationary and the stapling mechanism moves into position next to the stack (250) to staple the media sheets of the stack (250). In any of these examples, the fingers (202) of the clamp module (201 ) serve to maintain the registration of the stack (250) during the finishing process.

[0041] Before, during, and after the finishing process, the clamp module (201 ) may vary the amount of force applied by the fingers (202) to the stack (250) of media sheets. In one example, the fingers (202) are separated from the shelf (203) a partial amount based on the height of the stack (250) of media sheets. In this example, the pressure exerted by the fingers (202) is reduced to allow for mezzanines (204) using the X registering devices (21 1 ) to transport the stack (250) to the stapling mechanism to staple the stack (250) of media sheets together without having a number of media sheets within the stack (250) that are not directly held down by the fingers (202) not lay flat against the remaining media sheets within the stack (250). In some instances where the fingers (202) apply too much pressure, the corners of at least the top media sheet in the stack (250) may curl up. If this is the case, the stapling mechanism or other finishing mechanism may cause the media sheets within the stack (250) to no longer be registered with respect to one another and staple, punch, or bind the media sheets in an unregistered manner. Therefore, the pressure exerted by the fingers (202) is reduced during a finishing process to ensure that the stack (250) of media sheets maintains their relative registration. In these examples, the amount of reduction in pressure exerted by the fingers (202) of the clamp module (201 ) may be based on the height of the stack (250). For example, the reduction in pressure may be small in a stack (250) that is thinner or lower relative to another stack. Thus, a stack (250) that is 10 media sheets thick may experience a smaller pressure reduction from the fingers (202) during a finishing process relative to a stack (250) that is, for example, 30 media sheets thick. In one example, servo-mechanical control of the fingers (202) of the clamp module

(201 ) allows error-sensing negative feedback to adjust the pressure exerted by the fingers (202) and adjust such a pressure based on a detected height of the stack (250). The force exerted by the fingers (202) of the clamp module (201 ) may be tuned based on the number of media sheets within the stack (250).

[0042] In one example, the fingers (202) of the clamp module (201 ) utilize lost motion devices mechanically coupled to the fingers (202) to ensure that each finger (202) places approximately the same amount of pressure on the stack (250). In the example of Fig. 2, two fingers (202) are located in line with respect to the Y direction, but are spaced apart from one another with respect to the X direction. Thus, the fingers (202) apply pressure on two separate portions of the stack (250). In order to ensure that one finger (202) does not place too little or too much pressure on the stack (250), the lost motion device may be included within the clamp module (201 ). A lost motion device may be any device that imparts motion such as a reciprocating motion during which no useful work is performed, and may include, for example, a device that utilizes a tolerance between an input gear and an output gear.

[0043] In another example, a balanced clamping force may be achieved by applying a gimbal system within the clamping module (201 ). This gimbal system (1000) will now be described in connection with Fig. 10. Fig. 10 is a front view of the fingers (202) of the clamp module (201 ) of the output tray (121 ) of Fig. 2, according to another example of the principles described herein. The gimbal system (1000) includes a center pivot (1001 ) coupled to a gimbal arm (1002). The fingers (202-1 , 202-2) are pivotably coupled to the gimbal arm (1002) via the finger pivots (1003). Using the system of Fig. 10, the fingers

(202) are balanced by applying a common, centered force (1050) on the center pivot (1001 ). The centered force (1050) translates to the gimbal arm (1002), and, in turn, to each of the fingers (202-1 , 202-2). However, the forces (1051 , 1052) applied in opposition to each of the fingers (202-1 , 202-2) may be different such as those applied to the fingers (202) in Fig. 9. However, the gimbal system (1000) ensures that a balanced clamping force is applied by both fingers (202).

[0044] With regard to maintaining registration in the Y direction during deposition of the stack (250) onto the output floor (207), the movement of the mezzanines (204) will now be described. The mezzanines (204) move in the positive and negative X directions away from a center of the output tray (121 ) as depicted in, for example, Fig. 2. A number of articulating extension bars (205) are mechanically coupled to a number of extension arms (206). The extension arms (206) are coupled to the mezzanines (204) and a number of internal gears. A servomechanism or other mechanical driving device drives the mezzanines

(204) away from the center of the output tray (121 ). As the mezzanines (204) are moved away from the center of the output tray (121 ), the extension bars

(205) are retracted towards a respective mezzanine (204) as indicated by arrows D. As the extension bars (205) are retracted towards a respective mezzanine (104), the extension arms (206) also retract. This leaves the area between the mezzanines (204) open. Further, the distance between the mezzanines (204) is increased to allow for the stack (250) of media sheets to drop between the mezzanines (204) and onto the output floor (207).

[0045] In order to maintain the registration of the stack (250) of media sheets, the clamp module (201 ) and its fingers (202) pinch a proximal end of the stack (250) during the dropping of the stack (250) between the mezzanines (204) and onto the output floor (207) as depicted in, for example, Fig. 6. In Fig. 6, previous stacks (251 ) of media sheets are depicted as being deposited on the output floor (207) of the output tray (121 ). Further, a trailing edge (252) of the stack (250) of media sheets is depicted as being dropped between the mezzanines (204) to the output floor (207) and on top of the previous stacks (251 ) of media sheets. The leading edge (253) of the stack (250) of media sheets, however, is retained by the fingers (202) of the clamp module (201 ). The examples described herein allow a stack (250) of media sheets defining, for example, a print job to be dropped in two stages to maintain the quality of the print job including the registration of the media sheets within the stack (250) of media sheets.

[0046] During the separation of the mezzanines (204) in the X directions, and dropping of the stack (250), the clamp module (201 ) may vary the amount of force applied by the fingers (202) to the stack (250) of media sheets based on the height of the stack (250) of media sheets accumulated on the shelf (203). In this example, the fingers (202) of the clamp module (201 ) may be designed to apply relatively less pressure to a stack that is, for example, 10 media sheets thick, and apply relatively more pressure to a stack that is, for example, 30 media sheets thick. This ensures that the registration of the media sheets in any size of stack (250) is maintained despite the dropping of the trailing edge (252) of the stack (250) to the output floor (207) before the leading edge (253) is dropped.

[0047] In some examples, the user does not instruct the printing device (100) to perform a finishing process. In this example, the media sheets of the stack (250) are left unbound, and may lose their registration with respect to the media sheets included within the stack (250). In this case, the clamp module (201 ) maintains the registration of the media sheets by applying pressure between the fingers (202) and the shelf (203) and relying on the friction between the media sheets within the stack (250) to keep the media sheets in registration during the drop of the stack (250) to the output floor (207). Thus, in even an unfinished state, the registration of the stack (250) of media sheets is maintained due to the clamp module (201 ).

[0048] Turning again to Fig. 6, the leading edge (253) of the stack (250) is retained between the fingers (202) of the clamp (201 ) and the shelf (203) for a moment. Once the trailing edge (252) of the stack (250) has made contact with the output floor (207) or a previous stack (251 ), the shelf (103) may move such that it no longer supports the leading edge of the stack. In one example, the shelf may pivot toward the output floor (207) as depicted by arrow A of Fig. 4 using a pivoting mechanism (212) of the clamp module (201 ). The pivoting mechanism (212) couples the shelf (103) to the clamp module (201 ), and allows the shelf (103) to rotate. The actuation of the pivoting mechanism (212) causes the shelf (203) to rotate towards the output floor (207) and away from the fingers (202) of the clamp module (201 ), and releases the leading edge (253) of the stack (250) to drop to the output floor (207) or a top of a previously dropped stack(s) (251 ) of media sheets. In this manner, the registration of the stack (250) is maintained throughout the dropping of the stack (250) to the output floor (207).

[0049] In one example, the clamp module (201 ) and pivot mechanism (212) of the shelf (203) may be operated independently. The independent operation of the clamp module (201 ) and pivoting mechanism (212) provides for adjustments to be made to the operational sequencing described herein for optimum performance. Thus, as mentioned above, the clamp module (201 ), fingers (202), shelf (203), and mezzanines (204) provide a sequence or process of stack (250) management that provides better print job quality control for both finished and unfinished stacks (250).

[0050] Fig. 7 is a flowchart showing a method of ejecting a stack (250) of media sheets from a printing device (100), according to one example of the principles described herein. The method of Fig. 7 may begin by engaging (block 701 ) a clamp (201 , 202) to grab a number of registered media sheets comprising a print job. The media sheets form a stack (250). A height of the stack (250) of media sheets (i.e., the number of media sheets within the stack (250)) may be evaluated (block 702) to determine a pinch force of the fingers (202) of the clamp module (201 ).

[0051] With the clamp (201 , 202), the stack (250) of media sheets may be pinched (block 703) based on the determined pinch force. The method may continue by moving (block 704) a number of support mezzanines (204) from under the stack (250) of media sheets to allow a first end (252) of the stack (250) of media sheets to fall to an output floor (207). The clamp (201 ), the fingers (202), and the shelf (203) are disengaged (block 705) to allow a second end (253) of the stack (250) of media sheets to fall to the output floor (207). In one example, the disengagement (block 705) of the clamp (201 , 202) may be accomplished by pivoting the shelf (203) using the pivoting mechanism (212). [0052] Fig. 8 is a flowchart showing a method of ejecting a number of media sheets from a printing device (100), according to another example of the principles described herein. The method of Fig. 8 may begin by accumulating (block 801 ) a number of media sheets on a number of mezzanines (104) within an output tray (121 ) of a printing device (100). A clamp (201 , 202) may be engaged (block 802) to grab or retain a number of the media sheets. The media sheets form a stack (250).

[0053] The method of Fig. 8 may continue by determining (block 803) whether a finishing process is to be performed. In one example, a user may instruct the printing device (100) to perform a finishing process such as stapling, hole punching, binding, other finishing processes, or combinations thereof. In response to a determination that the user has requested a finishing process to be performed (block 803, determination YES), a number of processes are performed including lifting (block 804) the clamp (201 , 202) a partial amount based on the height of the stack (250) of media sheets to maintain the registration of the media sheets within the stack (250).

[0054] The stack (250) of media sheets may be aligned (block 805) with a finishing device such as, for example, a stapling mechanism. In one example, the stack (250) is moved to the finishing device using, for example, the clamp module (201 ), the fingers (202), the shelf (203), the mezzanines (104), other elements of the output tray (121 ), or combinations thereof. In another example, the finishing device is moved to the stack (250) as positioned on the shelf (203) and the mezzanines (104). The finishing process such as the stapling, hole punching, binding, or other finishing process is performed (block 806). The clamp (201 , 202) is opened (block 807) to allow the stack (250) of finished media sheets to be moved to a drop position on the shelf (203) and the mezzanines (104).

[0055] In response to a determination that the user has not requested a finishing process to be performed (block 803, determination NO), or when the stack (250) of finished media sheets is moved to the drop position on the shelf (203) and the mezzanines (104), a height of the stack (250) of media sheets (i.e., the number of media sheets within the stack (250)) may be evaluated (block 808) to determine a pinch force of the fingers (202) of the clamp module (201 ).

[0056] With the clamp (201 , 202), the stack (250) of media sheets may be pinched (block 809) based on the determined pinch force. The method may continue by moving (block 810) a number of support mezzanines (204) from under the stack (205) of media sheets to allow a first end (252) of the stack (250) of media sheets to fall to an output floor (207). The clamp (201 , 202) is disengaged (block 81 1 ) and the pivoting mechanism (212) of the clamp module (201 ) pivots the shelf (203) to allow a second end (253) of the stack (250) of media sheets to fall to the output floor (207). In one example, the

disengagement (block 81 1 ) of the clamp (201 , 202) may be accomplished by tilting or pivoting the shelf (203) using the pivoting mechanism (212), disengaging the fingers (202) of the clamp (201 ), or combinations thereof.

[0057] Throughout the methods of Figs. 7 and 8, a registration of the media sheets within the stack (250) is maintained with respect to one another. This registration may be maintained through a finishing process, through a drop process, and combinations thereof.

[0058] Aspects of the present system and method are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to examples of the principles described herein. Each block of the flowchart illustrations and block diagrams, and combinations of blocks in the flowchart illustrations and block diagrams, may be implemented by computer usable program code. The computer usable program code may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer usable program code, when executed via, for example, the controller (130) of the printing device (100) or other programmable data processing apparatus, implement the functions or acts specified in the flowchart and/or block diagram block or blocks. In one example, the computer usable program code may be embodied within a computer readable storage medium; the computer readable storage medium being part of the computer program product. In one example, the computer readable storage medium is a non-transitory computer readable medium.

[0059] The specification and figures describe methods and systems of ejecting a stack of media sheets from a printing device. A printing system for ejecting a stack of media sheets to an output tray includes a shelf to receive a leading edge of the stack of media sheets. The printing system also includes a clamp module to secure the leading edge of the stack of media sheets between a number of fingers of the clamp module and the shelf to retain the media sheets of the stack of media sheets in a registered state.

[0060] These methods and system (1 ) allow a stack of print media defining, for example, a print job to be dropped in two stages to maintain the quality of the print job and, especially, the registration of the media sheets within the stack of media sheets; (2) allow for a sequence that provides better print job quality control for both stapled and unstapled stacks; (3) allow the clamp pinch force to be tuned for the number of pages within a stack of media sheets; (4) provide fingers of the clamp mechanism with lost motion to ensure that each finger places a similar load on both the front and rear corners of the sheet and allows for the use of the fingers to control and manage the wedge of trapped air that is trapped under the media sheets during the operation of closing the clamps; (5) provide a pivoting shelf as a second action in the dropping of a stack of media sheets from the mezzanines allows for a gentle drop of the stack of media sheets onto the output floor while maintaining job quality including media sheet registration; (6) provide fingers of a clamp that are movable to different heights allows for the performance of the fingers to be tuned to the needs of a specific stack of media sheets at a specific location within the output tray; and (7) operate the clamp mechanism and shelf independently so that operational sequencing can be adjusted for optimum performance, among others.

[0061] The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.

Claims

CLAIMS WHAT IS CLAIMED IS:

1 . A printing system for ejecting a stack of media sheets to an output tray comprising:

a shelf to receive a leading edge of the stack of media sheets;

a clamp module to secure the leading edge of the stack of media sheets between a number of fingers of the clamp module and the shelf to retain the media sheets of the stack of media sheets in a registered state.

2. The system of claim 1 , further comprising a number of mezzanines to support at least a portion of the stack of media sheets, wherein the mezzanines are moveable out of underneath the stack of media sheets to allow a first end of the stack of media sheets to fall to an output floor.

3. The system of claim 1 , wherein the clamp maintains pressure on the stack of media sheets when a first end of the stack of media sheets reaches the output floor.

4. The system of claim 1 , wherein pressure exerted by the clamp on the stack of media sheets to secure the leading edge of the stack of media sheets is based at least partially on a height of the stack of media sheets.

5. The system of claim 1 , wherein the fingers move asymmetrically to create a wedge of air underneath the media sheets, the asymmetrical movement of the fingers causing the media sheets to register relative to one another.

6. The system of claim 1 , further comprising a number of friction pads coupled to the shelf to maintain a first of the media sheets in alignment with respect to the shelf.

7. A clamp for ejecting a stack of media sheets from a printing device comprising:

a shelf on which a number of media sheets are accumulated, the accumulated media sheets forming a stack of media sheets; and

a number of clamp fingers that secure the stack of media sheets against the shelf.

8. The clamp of claim 7, wherein the shelf pivots away from the clamp fingers independent of the movement of the fingers during a drop of the stack of media sheets to a floor of the output tray.

9. The system of claim 7, wherein the fingers comprise at least two fingers that exert an approximately identical pressure on different areas of the stack of media sheets.

10. A method of ejecting a stack of media sheets from a printing device comprising:

engaging a clamp to grab a number of registered media sheets comprising a print job, the media sheets forming a stack;

evaluating a height of the stack of media sheets to determine a pinch force;

with the clamp, pinching the stack of media sheets based on the determined pinch force;

moving a number of support mezzanines from under the stack of media sheets to allow a first end of the stack of media sheets to fall to an output floor; disengaging the clamp to allow a second end of the stack of media sheets to fall to the output floor once the shelf is removed.

1 1 . The method of 10, further comprising:

determining if a finishing process has been requested;

in response to a determination that a finishing process has been requested: performing the finishing process; and

maintaining registration of the media sheets within the stack of media sheets.

12. The method of 1 1 , wherein the finishing processes comprise, stapling, hole punching, binding, or combinations thereof.

13. The method of 1 1 , wherein performing the finishing process, and maintaining registration of the media sheets within the stack of media sheets comprises:

lifting a number of fingers of the clamps a partial amount based on the height of the stack of media sheets to maintain the registration of the media sheets;

aligning the stack of media sheets with a finishing device;

performing the finishing process; and

opening the clamp to allow the finished media sheets to be moved to a drop position.

14. The method of 13, wherein aligning the stack of media sheets with the finishing device comprises moving the stack of media sheets with the mezzanines to align with the finishing device.

15. The method of 13, wherein aligning the stack of media sheets with the finishing device comprises moving the finishing device to align with the stack of media sheets on the mezzanines.