Liftable transport pinch for a sheet printer

A liftable transport pinch is provided with a simplified construction to enhance lifetime and productivity. This transport device includes at least one roller mounted on an arm, and an actuator connected to a frame for moving the roller between a first and second position. The arm is mounted onto the frame by means of an elastic hinge element. The elastic hinge element provides a simple, cheap, wear-resistant, and easy-to-assembly alternative to prior art solutions.

FIELD OF THE INVENTION

The present invention generally pertains to a transport device for a sheet printer, a sheet printer comprising such a transport device, and a method for forming such a transport device.

BACKGROUND ART

Liftable pinches are applicable in sheet printers, specifically mid to large volume printers. A transport pinch is generally formed of two opposing rollers, one which is driven by means of a motor, such that a sheet pinched between the rollers is moved further along the transport path at which the transport pinch is positioned. In specific cases, it is desired to allow the transport pinch to release the sheet before it has exited the transport pinch by distancing the rollers from one another. For example, the sheet may be transferred from the transport pinch to a registration device which rotates and/or laterally translates the sheet. A liftable transport pinch is generally formed by mounting an arm holding one of the rollers on a pivot rod. An actuator is provided to alternate the rollers between adjacent and remote positions with respect to one another. At high print speeds (e.g. 300 sheets per minute) the transport pinch is required to operate at a similar frequency. The fast switching may result in oscillations in the arm, which need to be sufficiently reduced before accurately switching to another position and/or reliably releasing or further transporting the sheet. While springs may be provided on the arm to dampen oscillations, the dampening force of such springs is relatively low. Additionally, the pivot rod and/or the bearings required for allowing the arm to pivot were found to be sensitive to wear under this alternating load. Further, the construction is relatively complex and cumbersome to assemble.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved liftable transport pinch, specifically one which improves productivity and/or provides a simpler construction.

The present invention relates to a transport device for a sheet printer comprising:at least one roller mounted on an arm;an actuator connected to a frame for moving the roller between a first and second position,wherein the arm is mounted onto the frame by means of an elastic hinge element.

The elastic hinge element provides a simple support for the arm holding the roller, while defining the pivot axis around which the arm is allowed to pivot due to the elastic deformation of the hinge element. The elastic hinge element further acts as a damper, which reduces oscillations, shortening the delay between switching, while also reducing play and thereby decreasing (spring) hysteresis, and thus improving productivity. The dampening forces which can be achieved with the elastic hinge element are relatively large as compared to its overall dimensions. This allows for a compact construction. The pivot axis and damper are thus provided by the elastic hinge element, which does not require bearings for e.g. rotating parts. This results in a compact and simple construction, which is easy to assemble due to the low number of components. Thus, the object of the present invention has been achieved.

In an embodiment, the elastic hinge element defines a pivot axis for the arm, around which pivot axis the arm pivots upon actuation by the actuator. The elastic hinge element comprises a hinge axis or line, around which the arm substantially pivots. It will be appreciated that said hinge line may deform to a certain degree as the hinge element is deformed, dependent on the dimensions and materials applied in the hinge element.

In an embodiment, the elastic hinge element comprises a leaf spring. The elastic hinge element is formed of a leaf spring, preferably formed of an elastic plate. Preferably the leaf spring is formed of a metal plate or sheet. The leaf spring is in another embodiment configured as a damper to reduce oscillation of the arm after actuating the arm between the first and second position. The leaf spring allows for a relatively high elastic dampening force compared to the displacement of the arm. Thus a high braking force is generated to swiftly reduce or remove oscillations after actuating the arm.

In an embodiment, the leaf spring is a folded leaf spring. The elastic hinge element comprises or is formed of a folded leaf spring. The leaf spring, for example formed of a sheet or plate of elastic material, is folded around at least one fold line or axis. The fold line preferably corresponds to or substantially defines the pivot axis of the arm. This allows the arm to be pivotable without bearings. The folded leaf spring is a simple and cost effective method of forming an elastic hinge element.

In an embodiment, the hinge element is defined by channel in the plate. The channel is an elongated through-hole extending between the front and back side surface of the plate. The channel is provided at a predetermined location to achieve an elastic hinge element with the desired elasticity and range of motion required for the operation of the transport device. This allows the plate to extend to the lateral sides of a transport path section to be connected there to the frame. A standard plate materials may thus be used. It will be appreciated that the channel may range from a narrow elongated channel to a large opening in the plate, dependent on the manufacturing method applied.

In an embodiment, the channel extends between two points adjacent a fold line around which the plate is folded. The channel in combination with the fold line substantially circumscribe a through-hole in the plate. The through-hole may be partially filled with a plate portion connected to the fold line, though the through-hole may also be vacant if the corresponding material has been cut out or punched out. The channel provides a local reduction in the rigidity of the plate allowing the hinge element to be configured to the specifications of the user. The arm is preferably positioned in between the two points adjacent the fold line, when viewing perpendicular to the plate.

In an embodiment, the arm is rigid. The arm is rigid as compared to the section of the elastic hinge element on which the arm has been mounted. When exerting a force on the arm, the hinge element will deform while the arm substantially maintains its shape.

In an embodiment, the arm comprises at least one beam element with a U-shaped cross-section. The rigidity of the arm may be increased by forming the arm of one or more U-shaped beam elements. The legs of the U-shape provide a convenient mounting point for the roller, while the central part of the U-shape may be mounted on the hinge element or a central portion of the arm connected to the hinge element. Opposing U-shaped beam elements may be provided for a compact yet rigid construction of the arm.

In an embodiment, the first and/or second position is defined by a stop element for limiting the movement of the arm, and wherein the elastic hinge element dampens oscillations of the arm after the stop element has been contacted. In case of high productivity, the arm encounters the stop element with a relatively large velocity or force, which causes the arm to bounce back and/or oscillate. The arm may thereby briefly return at least partially to the its starting position before actuation. This results in a delay, as for accurate operation the position of the liftable hinge element needs to be determined to avoid damage the image receiving member. Since the arm is relatively rigid, the force and/or oscillation is transferred to the hinge element, which acts as a relatively strong damper and thus minimizes the delay.

The present invention further relates to a sheet printer comprising a transport device according to the present invention.

The present invention further relates to a method for forming a transport device for a sheet printer, comprising the steps of:Forming an elastic hinge element by folding a plate;Mounting a roller and an actuator on the elastic hinge element.

The elastic hinge element as described above may be formed of a plate, for example a metal sheet. The plate is folded to comprise at least one fold line to form the elastic hinge element. Preferably, a through-hole is provided in the plate near the position where the arm is to be mounted. The through-hole is for example a channel extending between two points adjacent or at the fold line. The roller is mounted on the elastic hinge element for example by means of arm. The arm may be formed separately, e.g. from U-shaped beam elements, or integrally with the hinge element. The transport device may then be positioned along a transport path section opposite to a drive roller to create a fast, reliable, and low-costs liftable transport pinch.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG.1shows schematically an embodiment of a printing system1according to the present invention. The printing system1, for purposes of explanation, is divided into an output section5, a print engine and control section3, a local user interface7and an input section4. While a specific printing system is shown and described, the disclosed embodiments may be used with other types of printing system such as an ink jet print system, an electrographic print system, etc.

The output section5comprises a first output holder52for holding printed image receiving material, for example a plurality of sheets. The output section5may comprise a second output holder55. While 2 output holders are illustrated inFIG.1, the number of output holders may include one, two, three or more output holders. The printed image receiving material is transported from the print engine and control section3via an inlet53to the output section5. When a stack ejection command is invoked by the controller37for the first output holder52, first guiding means54are activated in order to eject the plurality of sheets in the first output holder52outwards to a first external output holder51. When a stack ejection command is invoked by the controller37for the second output holder55, second guiding means56are activated in order to eject the plurality of sheets in the second output holder55outwards to a second external output holder57.

The output section5is digitally connected by means of a cable60to the print engine and control section3for bi-directional data signal transfer.

The print engine and control section3comprises a print engine and a controller37for controlling the printing process and scheduling the plurality of sheets in a printing order before they are separated from input holder44,45,46.

The controller37is a computer, a server or a workstation, connected to the print engine and connected to the digital environment of the printing system, for example a network N for transmitting a submitted print job to the printing system1. InFIG.1the controller37is positioned inside the print engine and control section3, but the controller37may also be at least partially positioned outside the print engine and control section3in connection with the network N in a workstation N1.

The controller37comprises a print job receiving section371permitting a user to submit a print job to the printing system1, the print job comprising image data to be printed and a plurality of print job settings. The controller37comprises a print job queue section372comprising a print job queue for print jobs submitted to the printing system1and scheduled to be printed. The controller37comprises a sheet scheduling section373for determining for each of the plurality of sheets of the print jobs in the print job queue an entrance time in the paper path of the print engine and control section3, especially an entrance time for the first pass and an entrance time for the second pass in the loop in the paper path according to the present invention. The sheet scheduling section373will also be called scheduler373hereinafter.

The sheet scheduling section373takes the length of the loop into account. The length of the loop corresponds to a loop time duration of a sheet going through the loop dependent on the velocity of the sheets in the loop. The loop time duration may vary per kind of sheet, i.e. a sheet with different media properties.

Resources may be recording material located in the input section4, marking material located in a reservoir39near or in the print head or print assembly31of the print engine, or finishing material located near the print head or print assembly31of the print engine or located in the output section5(not shown).

The paper path comprises a plurality of paper path sections32,33,34,35for transporting the image receiving material from an entry point36of the print engine and control section3along the print head or print assembly31to the inlet53of the output section5. The paper path sections32,33,34,35form a loop according to the present invention. The loop enables the printing of a duplex print job and/or a mix-plex job, i.e. a print job comprising a mix of sheets intended to be printed partially in a simplex mode and partially in a duplex mode.

The print head or print assembly31is suitable for ejecting and/or fixing marking material to image receiving material. The print head or print assembly31is positioned near the paper path section34. The print head or print assembly31may be an inkjet print head, a direct imaging toner assembly or an indirect imaging toner assembly.

While an image receiving material is transported along the paper path section34in a first pass in the loop, the image receiving material receives the marking material through the print head or print assembly31. A next paper path section32is a flip unit32for selecting a different subsequent paper path for simplex or duplex printing of the image receiving material. The flip unit32may be also used to flip a sheet of image receiving material after printing in simplex mode before the sheet leaves the print engine and control section3via a curved section38of the flip unit32and via the inlet53to the output section5. The curved section38of the flip unit32may not be present and the turning of a simplex page has to be done via another paper path section35.

In case of duplex printing on a sheet or when the curved section38is not present, the sheet is transported along the loop via paper path section35A in order to turn the sheet for enabling printing on the other side of the sheet. The sheet is transported along the paper path section35until it reaches a merging point34A at which sheets entering the paper path section34from the entry point36interweave with the sheets coming from the paper path section35. The sheets entering the paper path section34from the entry point36are starting their first pass along the print head or print assembly31in the loop.

The sheets coming from the paper path section35are starting their second pass along the print head or print assembly31in the loop. When a sheet has passed the print head or print assembly31for the second time in the second pass, the sheet is transported to the inlet53of the output section5.

The input section4may comprise at least one input holder44,45,46for holding the image receiving material before transporting the sheets of image receiving material to the print engine and control section3. Sheets of image receiving material are separated from the input holders44,45,46and guided from the input holders44,45,46by guiding means42,43,47to an outlet36for entrance in the print engine and control section3. Each input holder44,45,46may be used for holding a different kind of image receiving material, i.e. sheets having different media properties. While 3 input holders are illustrated inFIG.1, the number of input holders may include one, two, three or more input holders.

The local user interface7is suitable for displaying user interface windows for controlling the print job queue residing in the controller37. In another embodiment a computer N1in the network N has a user interface for displaying and controlling the print job queue of the printing system1.

FIG.2shows a transport device70as may be applied along any of the transport path sections32,33,34,35inFIG.1. The transport device70inFIG.2is a so-called liftable transport pinch70, which comprises two opposing rollers71,73one of which may be driven by a drive or motor to transport the image receiving material further along the respective transport path section32,33,34,35. The transport device70comprises an actuator85for positioning the rollers71,73between a first and a second position. In the first position the rollers71,73are adjacent and/or in contact, such that the image receiving material passing between the rollers71,73is in good contact with the driven roller71,73for reliably transporting the image receiving member without or with little slippage. The first position is generally referred to as ‘closed.’ In the second position the rollers71,73are relatively remote from one another, such that the image receiving member may pass through the rollers71,73relatively unengaged or unaffected by the transport device70save for support from below. The second position is generally referred to as ‘open’, as the image receiving member may pass through the transport pinch70without being locally held or pinched by the rollers71,73. InFIG.2, the rollers71,73are in the first position. While in this example, roller71is provided with a drive (not shown) for rotating the roller71around its axis72, such a drive may instead of or also be provided for the roller73.

FIG.2shows the roller73being rotatable around axis74, which axis74is mounted on the arm80. The arm80comprises a first beam81with a U-shaped cross-section and a second beam82with a U-shaped cross-section, which are mounted onto one another by means of fasteners83in the form of screws83. The U-shaped cross-sections of the beams81,83ensure a relatively high rigidity of the arm80to avoid oscillations due to elastic deformation of the arm80. The arm80is connected to the frame100via the elastic hinge element90. The elastic hinge element90further defines the pivot axis (93inFIGS.3and4) around which the arm80may pivot when actuated by the actuator85. The actuator85is illustrated as a solenoid85, though other suitable actuators such as pneumatic or linear actuators may further be applied with the context of the present invention. The actuator85engages the arm80by means of the attachment element86.

The attachment element86is connected to both the actuator85and the arm80to allow of sufficient freedom of movement for both the pivoting of the arm80and the motion of the actuator85. The attachment element86may thereto be rotatably or deformably mounted with respect to the arm80and/or the remainder of the actuator85.

The elastic hinge element90is formed of a bent plate90, which is mounted to the frame100. The elastic hinge element90provides a simple and cheap means for mounting the transport device70to a frame100of a printer. This reduces costs in terms of material and assembly time. The elastic hinge element90further defines the pivot axis of the arm80. This is advantageous in terms of wear on the pivot axis as compared to e.g. an arm provided on a rod by means of a bearing that allows the arm to pivot around the rod. In a high production environment print speeds up to 300 or more sheets per minute may be reached, requiring the transport pinch70to operate at the same frequency. With a suitable selection of materials and dimensions a long lifetime of the elastic hinge element90can be reached. Further, the elastic hinge element90acts as a damper when it is deformed from its rest position, which prevents oscillations of the arm90after actuation. As in the indicated, the actuation may be relatively fast, such that when the arm80hits it stop element (not shown) with relatively high impact, this will cause the arm80to bounce back and forth. This oscillation is reduced or even eliminated, as the elastic hinge element90is capable of generating a relatively large elastic counter force to dampen such an oscillation. Additionally, the elastic hinge element90's simple construction helps in reducing play in the transport device70. In consequence, the operation is relatively energy efficient, as the elastic hinge element90contributes to reducing hysteresis, specifically spring hysteresis. The rest position (corresponding to the undeformed state) of the hinge element90may be suitably selected to lie in between the first and second position or at one of those positions, dependent on the requirements of the transport device70.

FIGS.3and4illustrate the elastic hinge element90in a perspective view. The elastic hinge element90is formed of a folded metal plate. Other suitable elastic materials other than metal may be applied, such as plastics or composite materials. The plate92of the hinge element90is folded around the fold line93. The hinge element90has a first plate portion95on a first side of the fold line93on which first plate portion95the arm80is mounted. A second plate portion96extends on an opposite side of the fold line93. The hinge element90is connected to the frame100, such that one of the first of the second plate portions95,96is moveable around the fold line93with respect to the frame100. InFIG.3, the second plate portion96is formed by a channel94, which extends between two different points along the fold line94. The channel94is a cut-out or elongated through-hole that allows the second plate portion96to move with respect to the remainder of the plate92. The first plate portion95is secured to the frame100at its lateral ends. The first plate portion95does not substantially move, but deforms as the arm80is moved. The second plate portion96is substantially free to pivot or fold around the fold line93. The channel94provides sufficient local deformability in the plate92to allow the arm80to move between its first and second position under the force of the actuator85. It will be appreciated that the second plate portion96may also be omitted and an equally large opening may be provided in the plate92at the location of the second plate portion96.

The plate92is mountable onto the frame100of the printer1. InFIG.4mounting points for fasteners, specifically screws, are provided at the lateral sides of the plate92. The connection to the frame100secures the plate92at two fixed points on opposite sides. The fixation prevents the plate92from translating or rotating, ensuring that movement of the arm80is achieved through deformation of the elastic hinge element90alone. In consequence, an elastic counter force or dampening force acts on the arm80when it moves from the first to the second position and/or vice versa. The elastic deformation of the hinge element90does not rely on any moveable parts requiring bearings and is thus very wear resistant. The arm80is substantially more rigid than the elastic hinge element90, such that forces on the arm80entirely or for the large majority affect a deformation of the hinge element90. Deforming the hinge element90results in an opposing force urging the hinge element90back to its rest position. The counter force prevents or reduces oscillations of the arm80, which effectively reduces the time required for switching. This allows consecutive image receiving members to be positioned closer together, which in turn increases the total number of image receiving members which can be processed at a certain transport velocity.

The elastic hinge element90is comprised in the plate92. The plate92extends laterally along the width of the respective transport path section, such that it can be easily mounted to the frame. By mounting the plate92to the frame100, the external degrees of freedom of the plate92are fixed, such that moving the arm80results in an elastic deformation of the hinge element90. The plate92further the pivot axis of the arm80by its fold line93, while also providing a dampening force when the hinge element90is deformed. Thus, the support for the arm80, its damper, and its pivoting means are integrally formed from the plate92. It will be appreciated that the arm80may further be integrally formed with plate92by providing a suitable cut-out for the arm, and even for forming a U-shaped beam element by bending sections of the plate.

FIG.5schematically illustrates the steps for forming the transport device70. The elastic hinge element90is formed by the optional step a, in which the channel94is formed in the plate92. The plate92is further folded along its fold line93to form the elastic hinge element90. The angle wherein the plate92is folded is at angle greater than 45°, preferably a substantially right angle. The plate92is then secured to the frame100, such that it as a whole is unable to translate or rotate. The roller73and the actuator85may be connected to the hinge element90, for example via the arm80. A drive roller71may further be provided opposite the roller73.

Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any advantageous combination of such claims are herewith disclosed.

Further, it is contemplated that structural elements may be generated by application of three-dimensional (3D) printing techniques. Therefore, any reference to a structural element is intended to encompass any computer executable instructions that instruct a computer to generate such a structural element by three-dimensional printing techniques or similar computer controlled manufacturing techniques. Furthermore, such a reference to a structural element encompasses a computer readable medium carrying such computer executable instructions.

Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly.