Abstract:
A device for binding a stack of media sheets using imaging material as the binding agent. The binding device includes a tray for supporting the stack and a heated platen or some other type of imaging material activator near the tray. A press coupled to the activator is operative between a first position in which the activator is separated from the stack to a second position in which the activator contacts and compresses the stack at the binding region. A spring or other biasing mechanism operatively connected between the press and the activator biases the activator against the stack when the press is in the second position. The biasing mechanism allows pressure to be maintained on the stack to reactivate the imaging material without continuing to power the press down against the stack even as the stack shrinks under the reactivating pressure. Hence, power can be diverted if necessary or desirable from the press to activator to reduce the overall power consumption of the binding device.

Description:
CROSS REFERENCE TO RELATE APPLICATION  
       [0001]    This is a continuation-in-part of application Ser. No. 09/482,124 filed Jan. 11, 2000.  
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to an apparatus and method for binding media sheets. More particularly, the invention relates to an apparatus and method for producing a bound document from a plurality of media sheets using imaging material as a binding agent.  
         BACKGROUND  
         [0003]    Current devices and methods for printing and binding media sheets involve printing the desired document on a plurality of media sheets, assembling the media sheets into a stack, and separately stapling, clamping, gluing and/or sewing the stack. In addition to imaging material used to print the document, each of these binding methods require separate binding materials, increasing the cost and complexity of binding. Techniques for binding media sheets using a common printing and binding material are known in the art. These techniques generally involve applying imaging material such as toner to defined binding regions on multiple sheets, assembling the media sheets into a stack, and reactivating the imaging material, causing the media sheets to adhere to one another.  
           [0004]    These known devices and methods, however, can consume significantly more time than producing an unbound document. Each involves printing the entire or a substantial portion of the desired document, then assembling and aligning the media sheets into a stack in preparation to be bound. Binding the stack of media sheets also entails applying sufficient heat to the binding region to reactivate the imaging material throughout multiple sheets or throughout the entire stack. Consequently, the thickness of the bound document is limited by the device&#39;s ability to adequately heat the binding regions throughout multiple sheets or the stack without damaging the media sheets. In some instance it is desirable to simultaneously bind a stack of media sheets. However, as the binding regions of the sheets in the stack are heated, the thickness of the stack decreases. Failing to compensate for this decrease produces sub-optimal binding conditions.  
         SUMMARY  
         [0005]    The present invention is directed to a device for binding a stack of media sheets using imaging material as the binding agent. In one embodiment, the binding device includes a tray for supporting the stack and a heated platen or some other type of imaging material activator near the tray. A press coupled to the activator is operative between a first position in which the activator is separated from the stack to a second position in which the activator contacts and compresses the stack at the binding region. A spring or other biasing mechanism operatively connected between the press and the activator biases the activator against the stack when the press is in the second position. The biasing mechanism allows pressure to be maintained on the stack to reactivate the imaging material without continuing to power the press down against the stack even as the stack shrinks under the reactivating pressure. Hence, power can be diverted if necessary or desirable from the press to activator to reduce the overall power consumption of the binding device.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a plan view of multiple media sheets that will be bound in to a document showing the toner binding region along the left edge of each sheet.  
         [0007]    [0007]FIG. 2 is a perspective view of a binding device constructed according to one embodiment of the invention in which the document is stacked horizontally and the binder uses a thermally dissipative heat sink.  
         [0008]    FIGS.  3 A- 3 E are sequential cross section views illustrating the operation of the binding device of FIG. 2.  
         [0009]    [0009]FIG. 4A- 4 E are sequential cross section views illustrating the operation of a binding device constructed according to a second embodiment of the invention in which the document is stacked vertically and the binder uses an electrically dissipative heat sink.  
         [0010]    [0010]FIG. 5 is a block diagram representing a system for creating, printing and binding a bound document.  
         [0011]    [0011]FIG. 6 is a perspective view of a binding device according to another embodiment of the invention in which a lead-screw type press is used.  
         [0012]    FIGS.  7 A- 7 E are sequential cross sectional views illustrating the operation of the binding device of FIG. 6.  
         [0013]    [0013]FIG. 8 is a schematic illustration of the binder of FIG. 6 including a controller and a power supply.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    [0014]FIG. 1 shows multiple media sheets used to form a document  5 , each media sheet generally referenced as  10 . Document  5  includes multiple print images  11 . Each print image  11  represents a page of document  5  and may include text and/or graphics. Each media sheet  10  may have a print image  11  applied to one or both sides. For example, a ten page document, composed of ten print images, may be produced on five media sheets, one print image on each side. Each media sheet  10  also includes imaging material, such as toner, applied to one or more selected binding regions  12 . Binding region  12  usually will be located along one edge of media sheet  10  on one or both sides. Preferably, binding region  12  is applied to only the bottom side of each sheet in which case it is not necessary to apply imaging material to a binding region on the first/bottom sheet. The dotted lines along binding regions  12  in the Figures indicate the imaging material has been applied to the bottom side of the sheet.  
         [0015]    My earlier filed patent application, Serial No. 09/482,124 (the &#39;124 application), discloses a new method and apparatus for binding documents by individually binding each media sheet to previously bound media sheets using imaging material as the binding material. The binding devices described in the &#39;124 application may be adapted for use with the present invention in which stacked sheets are simultaneously bound together using imaging material as the binding agent. The binding devices  22  in FIGS. 2 and 3A- 3 C and FIGS.  4 A- 4 C, for example, are similar to the binding devices described in the &#39;124 application.  
         [0016]    Referring now to FIG. 2, document  5  is formed by binding a stack  14  of sheets  10 . Stack  14  represents generally an entire document or only part of a document. The binding region  12  on each sheet is aligned with the binding region of the sheets in stack  14  and the imaging material applied to binding region  12  is reactivated to fuse and thereby bind stacked sheets  10 . The strength of the inter-sheet bond is a function of the type, area, density, and degree of reactivation of the imaging material applied to binding region  12  of each media sheet  10 . By varying these parameters the inter-sheet bond can be made very strong to firmly bind the document or less strong to allow easy separation. It is expected that the imaging material will usually be reactivated by applying heat and pressure. A variety of other reactivation techniques that may be used are described in my copending application Ser. No. 09/320,060, titled Binding Sheet Media Using Imaging Material, which is incorporated herein by reference in its entirety.  
         [0017]    Binding apparatus  22  includes a sheet collecting tray  24 , press  26 , heated platen  28  and an optional heat sink  30 . Press  26 , heated platen  28  and heat sink  30  move up and down or back and forth along guide posts  31 . Heated platen  28  is biased away from the sheet collection area of tray  24  with, for example, compression springs  32  to provide adequate clearance for the document. Press  26  is operatively coupled to heated platen  28  through heat sink  30  and a second pair of compression springs  33  positioned between heat sink  30  and heated platen  28 . Preferably, heat sink  30  will have a much greater effective thermal mass than heated platen  28  and heated platen  28  will be very thin to promote rapid heating and cooling. In this embodiment, heated platen  28  includes an electrically resistive heating element  34 . Heated platen  28  is heated, for example, by electric current passing through a resistive element  34 . The relatively large thermal mass of heat sink  30  may be achieved in a variety of ways. For example, heat may be dissipated passively through a large physical mass of thermally conductive material that dissipates heat by thermal conduction as it contacts heated platen  28 . Heat may be dissipated actively through a convection heat sink in which moving air is used to cool heated platen  28 . Or, heat may be dissipated through a material having a much lower electrical resistance that diverts electrical current from heated platen  28 . A combination of two more of these techniques might also be used. The relation of the heat capacities of heated platen  28  and heat sink  30  can be optimized for the particular operating environment to help facilitate continuous operation of binder  22 .  
         [0018]    The operation of binder  22  will now be described with reference to the section view of binder  22  in FIGS.  3 A- 3 C. Each sheet  10  is output from the printer, copier, fax machine or other image forming device into tray  24 . Sheet  10  is aligned to the stack  14  as may be necessary or desirable using conventional techniques. Once the desired number of sheets, one full document for example, are output to tray  24 , press  26  descends against heat sink  30 , overcomes the resistance of first biasing springs  32  and presses heated platen  28  against stack  14  along binding region  12 , as seen by comparing FIGS. 3A and 3B. The heat and pressure applied to binding region  12  of sheet  10  reactivates the imaging material (melts the toner) in region  12 .  
         [0019]    Often, the power available to compress and heat binding regions  12  of stack  14  is limited. Once binding regions are compressed it is desirable to divert power from press  26  and utilize the available power for reactivating the imaging material. As imaging material such as toner is reactivated, it melts and spreads slightly causing the thickness of stack  14  to decrease. To create a secure and consistent bond, it is helpful to maintain pressure on binding regions  12  of each sheet  10  in stack  14  as the applied imaging material is reactivated and cooled without driving press  26  further down on the stack. Hence, press  26  continues to descend to overcome the resistance of second biasing springs  33  to the position shown in FIG. 3C. The thickness of stack  14  at this point is represented by T 1  in FIGS. 3B and 3C. As heated platen  28  re-activates and melts the imaging material on binding regions  12  and the thickness of stack  14  decreases to T 2 , second biasing springs  33  expand to maintain pressure on heated platen  28  without driving press  26  further down on the stack, as seen by comparing FIGS. 3C and 3D. The compressed thickness of stack  14  is represented by T 2  in FIG. 3D.  
         [0020]    If optional heat sink  30  is used, once the imaging material is melted, press  26  is re-energized to press heat sink  30  into contact with heated platen  28 , as seen by comparing FIGS. 3D and 3E. The large comparatively cool thermal mass of heat sink  30  cools heated platen  28 , sheet  10  and stack  14 . Press  26  is held momentarily in the fully descended position to maintain pressure on sheet  10  and stack  14  as the heated platen  28  cools. The cooling combined with the continuing compression of media sheet  10  and stack  14  allows the reactivated imaging material (melted toner) to cure. As the pressure is released, biasing springs  32  and  33  return heated platen  28  and heat sink  30  to their respective starting positions.  
         [0021]    In the embodiment illustrated in FIGS. 2 and 3A- 3 E, heat sink  30  is a highly thermally conductive material such as an aluminum block or a forced air convection type heat exchanger. Heat sink  30  must be large enough to dissipate heat from heated platen  28  throughout the binding operation. The size and thermal conductivity of heat sink  30  will depend on a variety of operating parameters for the particular printing system, including the speed of the printer (usually measured in pages output per minute), the maximum number of pages in the bound document, the characteristics of the toner or other imaging materials used to bind the pages and the availability of cooling air flow. Second springs  33  are stiffer than first springs  32  so that as press  26  descends heated platen  28  is pressed against the stack  14  before heat sink  30  is pressed against heated platen  28 .  
         [0022]    FIGS.  4 A- 4 E illustrate an alternative embodiment in which the press  26  moves horizontally and an electrically dissipative heat sink  30  is used instead of the thermally dissipative heat sink of FIG. 2. Referring to FIGS.  4 A- 4 E, sheets  10  accumulate in a vertically oriented tray  26 . As heat sink  30  is pressed toward tray  24 , heated platen  28  is pressed into stack  14  at the urging of springs  33  and slide block  36 . As with the first embodiment, the heat and pressure applied to binding region  12  of sheet  10  reactivates the imaging material in region  12 . As heat sink  30  is pressed further towards tray  24 , it overcomes the resistance of springs  33  and electrically contacts resistive element  34 . This electrical contact diverts or “short circuits” the electrical current from resistive heating element  34  in heated platen  28  to the low resistance heat sink  30  to cool heated platen  28 . Again, as with the first embodiment, binder  22  is held momentarily in the fully compressed position to maintain pressure on sheet  10  and stack  14  as the heated platen  28  cools. The cooling combined with the continuing compression of media sheet  10  and stack  14  allows the reactivated imaging material to cure. Heat sink  30  and the other components are then withdrawn to their starting positions. An electrically dissipative heat sink could also be implemented through a switching circuit selectively connecting heated platen  28  to a heat sink remote from binder  22 . The electrically dissipative heat sink could be located, for example, in the printer or even in a server or client computer. A remote electrically dissipative heat could be selectively connected to heated platen  28  through control switching activated by temperature, sheet registration, timing or any other suitable control mechanism.  
         [0023]    Referring now to the block diagram of FIG. 5, it is envisioned that binder  22  will be used as a component of a document production system  40 . In addition to binder  22 , system  40  includes an image forming device such as printer  42  and one or more computing devices  46 . Binder  22  and printer  42  may be separate components or may be integrated into a single appliance. Alternatively, binder  22  may be used as a stand alone device apart from system  40 .  
         [0024]    Computer  46  may be programmed to generate and/or retrieve a desired print image in electronic form  44  and to transmit electronic document  44  to printer  42  instructing printer  42  to create the desired print image on media sheet  10 . This programming may generally be accomplished by document production software  48  in combination with a printer driver  50 . However, system  40  does not necessarily require computer  46 . Instead, printer  42  may itself perform the functions of computer  46 . A digital copier, for example, generates and stores the electronic document itself for subsequent transmission to the print engine where the electronic image is developed into the printed image.  
         [0025]    Software  48  electronically creates and/or retrieves desired document  44 . Upon receiving a print command, software  48  transmits electronic data representing desired document  44  to printer driver  50 . Printer driver  50  compiles the electronic data into a form readable by printer  42 , generally breaking the electronic data representing desired document  44  into a plurality of separate print images, each representing a page of desired document  44 . Software  48  and/or printer driver  50  may also define binding region  12  for each media sheet  10  to be transmitted along with or as part of each print image. Alternatively, binding region  12  may be defined by printer  42  or by another suitable mechanism. For each media sheet  10  used to form desired document  44 , printer  42  applies imaging material in the pattern of the desired print image on one or both sides of media sheet  10 . Printer  42  may also apply imaging material to defined binding region  12  located on one or both sides of media sheet  10 . Printer  42  activates the imaging material (fuses the toner if laser toner is used) and outputs media sheet  10  to binder  22 .  
         [0026]    Printer  42  is depicted as a laser printer in FIG. 5. Although it is expected that the binding techniques of the present invention will be most often used with and embodied in electrophotographic printing devices such as the laser printer illustrated in FIG. 5, these techniques could be used with and embodied in various other types of image forming devices. Referring again to FIG. 5, document production software  48  and printer driver  50  transmit data representing the desired print image and binding regions to input  41  on laser printer  42 . The data is analyzed in the printer&#39;s controller/formatter  43 , which typically consists of a microprocessor and related programmable memory and page buffer. Controller/formatter  43  formulates and stores an electronic representation of each page that is to be printed, including the print image and the binding regions. In addition to formatting the data received from input  41 , controller/formatter  43  drives and controls the toner development unit  45 , fuser  47  and other components of print engine  49 .  
         [0027]    [0027]FIG. 6 illustrates an alternative embodiment of the invention in which press  26  includes lead screws  60  and carriage  62 . Carriage  62  supports heated platen  28  and travels up and down or back and forth along lead screws  60 . Compression springs  63  are placed between heated platen  28  and carriage  62 . Heated platen  28  includes floating guide posts  64  which slide through carriage  62 . Carriage  62 , in relation to heated platen  28 , travels up and down or back and forth along floating guide posts  64  while compression springs  63  bias heated platen  28  away from carriage  62 . Press  26  utilizes a servo motor or other suitable mechanism that rotates lead screws  60  driving carriage  62 . Depending upon the direction of rotation, lead screws  60  either urges carriage  62  and heated platen  28  toward or away from tray  24 . It may is desirable to include a second heated platen  65  (shown FIGS.  7 A- 7 E)coupled to or embedded in tray  24 . As lead screws  60  rotate urging carriage  62  in the direction of tray  24 , binding regions  12  of sheets  10  are compressed between first heated platen  28  and second heated platen  65 . The dual heating elements in this embodiment provide faster heating to reduce binding times, allows the binder to accommodate thicker stacks, and helps prevent damage to sheets  10  by providing a more uniform heat transfer through stack  14 .  
         [0028]    The operation of this embodiment of binder  22  will now be described with reference to FIGS.  7 A- 7 E. With press  26  holding heated platen  28  in the open position as illustrated in FIG. 7A, sheets  10  of stack  14  are initially collected in tray  24  aligning binding regions  12  of sheets  10  between heated platens  28  and  65 . In FIG. 7B, lead screws  60  rotate driving carriage  62  and moving heated platen  28  into contact with stack  14  compressing binding regions  12  between heated platens  28  and  65 . Continuing to rotate, lead screws  60  cause carriage  62  to overcome the resistance of compression springs  63  and hold heated platen  28  in a first pressed position. The thickness of stack at this point is represented by T 1  in FIG. 7C. As heated platens  28  and  65  reactivate the imaging material deposited on binding regions  44 , the thickness of stack  14  decreases. Referring now to FIG. 7D, compression springs  63  then expand moving heated platen  28  into a second pressed position causing further compression of stack  14 . Consequently, pressure on binding regions  12  is maintained. The thickness of stack  14  at this point is represented by T 2  which is smaller than T 1 . The direction of rotation of lead screws  60  then reverses pulling carriage  62  away from tray  24  separating heated platen  28  from stack  14  while allowing compression springs  63  to fully expand. Stack  14  is bound and can be removed from tray  48 .  
         [0029]    Once lead screws  60  rotate sufficiently to move heated platen  28  into the first pressed position biasing compression springs  54 , press  26  stops, effectively locking carriage  62  in place. Beneficially, the power needed to move heated platen  28  from the first pressed position to the second pressed position is stored mechanically within the biased compression springs  63 . Power needed to reactivate the imaging material can then be diverted from press  26  to heated platens  28  and  65 .  
         [0030]    Compression springs  63  are only one example of a suitable biasing mechanism. Pneumatic cylinders, resilient foam, or other structures or mechanisms that store energy needed to maintain pressure on binding regions  12 . Moreover, heated platens  28  and  65  provide only one example of structures capable of activating imaging material. Other structures, or activators, may accomplish the function through direct application of heat as described above, or through ultrasound, magnetic energy, radio frequency energy and other forms of electromagnetic energy. It is possible to use toner which re-activates upon application of pressure alone. The toner used for binding may include magnetic ink or otherwise may have a quality of reacting to electromagnetic, optical or actinic energy (infrared, visible or ultraviolet). The ability to react to energy may be in the form of heat conversion or chemical reaction. The ability to react to energy enhances the ability of re-activating without burning the paper or otherwise damaging the sheets. Hence, pressing a heated platen against the stack is just one structure that may be used to carry out the method of the invention.  
         [0031]    In the embodiment illustrated in FIG. 8, binder  22  also includes controller  66  and power supply  68 . To help automate binding operations, controller  66  is electronically coupled to computer  46  and/or printer  42  (shown in FIG. 5), press  26 , heated platens  28  and  65 , and power supply  68 . Power supply  68  provides the power needed to operate press  26  and heated platens  28  and  65  and may be a component of binder  22  or printer  42 . Once printer  42  dispenses each sheet  10  of stack  14  into tray  24 , computer  46  or printer  42  sends a binding instruction to controller  66 . Controller  66  contains software or firmware for directing press  26  and heated platens  28  and  65  to bind stack  14 . Upon receipt of the binding instruction, controller  66  directs power from power supply  68  to press  26  and instructs press  26  to move heated platen  28  from an open position to the first pressed position compressing stack  14 . To re-activate the imaging material, controller  66  then diverts power from press  26  to heated platens  28  and  65 . Once the imaging material is sufficiently re-activated, controller  66  removes power from heated platens  28  and  65  allowing the imaging material to fuse to and bind stack  14 . Controller  66  then diverts power back to press  26  instructing press  26  to return heated platen  28  to the open position releasing stack  14 .  
         [0032]    The present invention has been shown and described with reference to the foregoing exemplary embodiments. It is to be understood, however, that other forms, details, and embodiments may be made without departing from the spirit and scope of the invention which is defined in the following claims.