Abstract:
Disclosed is a printing system having a plurality of print heads for printing an image on a print receiving medium, print head actuators operable for individually repositioning the print heads to optimal locations for each print job, and software operable while a current print job is active for determining the optimal print head locations for a next anticipated print job.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to printing devices used by computer systems and more specifically to printing devices that are configured to position the print heads for the expected printed output.  
         DESCRIPTION OF RELATED ART  
         [0002]    There are many types of printing devices for computer systems including laser printers, pen plotters, scanning head printers, impact printers and ink jet printers. Laser printers create an image by placing a charge onto a drum that attracts colorant particles, or toner, and transferring the colorant particles onto a sheet of paper. The sheet of paper is then passed through a fuser where the colorant is fused or melted onto the paper.  
           [0003]    A pen plotter draws lines on a medium by moving a pen relative to a sheet of paper. By moving the pen in a scanning direction and moving the medium in a perpendicular direction, a two-dimensional image is created. A pen plotter may be used to create line drawings of any type, or area fills, by drawing lines right next to one another. In pen plotters, color images may be created by the use of different color pens. Typically, two to eight different color pens are used.  
           [0004]    In a scanning head system both the print head and the paper (or, more generally, the print medium) are moved independent of each other. In this system, the print head is scanned across the medium and then the medium is advanced. Once the medium has been advanced, the print head is scanned for a next pass. A variation on a scanning head printer is to hold the printing device (such as a pen in an ink jet printer) stationary and pass the medium under the print head. These devices are referred to as fixed pin or fixed print head printing devices.  
           [0005]    Impact printers use an ink bearing component, such as a ribbon, which is struck by a print head to write onto a printing surface. Typically, the print head moves along the width of the print medium and the print medium is transported longitudinally.  
           [0006]    In an ink jet printer a jet of ink is projected out of a print head onto the surface of the object, such as paper, to be printed. The print head is moved along the surface of the print medium.  
           [0007]    A printer utilizing a fixed print head keeps, as the name implies, the print head stationary and passes the paper or print medium under the print head to form an image. Movement of the print media may vary from system to system; in some systems the medium is moved back and forth several times to create additional details in the image. See, for example, U.S. Pat. Nos. 6,113,232 and 6,155,680, both of which are incorporated herein by reference in their entirety, which describe stationary pen ink jet printers.  
           [0008]    In fixed pen printing systems, those in which printing is accomplished with a single pass of the medium under the pen or print head, the size of the printed image is limited by the size of the printing device, for instance the size of a nozzle array. The size of the printed image may be increased by using multiple print heads or pens positioned in sequence, effectively employing a larger print head. Such systems are described in, for example, U.S. Pat. Nos. 4,977,410; 5,589,868; 5,943,083; 6,290,316; and 5,966,149, all of which are incorporated herein by reference in their entirety, describing use of a plurality of print heads or a segmented or divided line head to print a full line across a page. Each of these methods increase the cost, complexity, and size of the printing device. Typically in each of these printing devices, the printable portion of the paper is determined by the location of the print head or pen with respect to the medium. In order to allow printing over the entire paper, numerous print heads, or one extended print head, can be constructed along one edge of the paper. With this configuration, a single color can be printed along an entire page in a single pass of either the print heads or the paper.  
           [0009]    With today&#39;s printing devices, printing on specialty media such as envelopes, labels or similar medium, requires either a versatile-multifunction printing device configured for the specific task, or requires a machine designed and dedicated specifically for that purpose. For example, a multi-purpose printer could be configured to print envelopes, or a printer can be purchased for printing envelopes.  
         BRIEF SUMMARY  
         [0010]    One embodiment is directed to a printing system comprising a plurality of print heads for printing an image on a print receiving medium, print head actuators operable for individually repositioning the print heads to optimal locations for each print job, and software operable while a current print job is active for determining the optimal print head locations for a next anticipated print job.  
           [0011]    Another embodiment is directed to a method for printing an image onto a print receiving medium comprising determining, while a current image is being printed, a desired subsequent printing position for one or more print heads, and repositioning, at the completion of the printing of the current image, one or more print heads to the desired subsequent printing position.  
           [0012]    Another embodiment is directed to an apparatus for printing an image onto a print receiving medium comprising a plurality of print heads, means for repositioning each of said print heads from previous printing locations to desired print head locations in accordance with a determined desired print head location for each said print head on a print job by print job basis, means for determining said desired print head location for a next anticipated print job while a current print job is in process, and means for enabling said repositioning means immediately upon the conclusion of said current print job. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a block diagram illustrating one embodiment of print heads within a printing system which implements the current invention; and  
         [0014]    [0014]FIG. 2 is a flow chart illustrating the steps performed in one embodiment of the current invention.  
     
    
     DETAILED DESCRIPTION  
       [0015]    The current invention is a variation of a fixed pen device in that the pens remain fixed during the printing of a specific print job, but can move from a first position to alternate positions for the next print job. It should be appreciated that pens as referred to with respect to the present invention encompasses any form of print mechanism, including ink jet, laser, impact, and pen printing mechanisms.  
         [0016]    The structure of the present invention reduces printer costs by minimizing the number and/or size of print heads included in a printer. Preferred embodiment printers may be connected electronically to a computer system in a conventional manner, e.g., using a standard serial or parallel printer interface or via a local area network and associated protocol. Positioning of print heads to desired printing positions may enable printing on a particular print receiving medium and/or in a particular format. In order for the print heads to be properly positioned, a signal may be sent to the control mechanism attached to the print heads, such as motors, which represents the amount of movement necessary for any or all of the print heads. Preferably, the print heads may be mounted in carriages that are configured to traverse a width of the print receiving medium, or some portion thereof, while the medium is transported in a longitudinal direction beneath the linear or staggered array of print heads. One method of determining the amount of movement necessary in the print heads is to determine the current position, determine the desired position, and to determine the amount and direction of movement necessary of the print heads.  
         [0017]    [0017]FIG. 1 is a diagram of one embodiment of a print system, including print heads, according to the current invention. In FIG. 1, information regarding a particular medium and associated print format, such as for envelope  101 , may be provided to positioning software stored in and executed by processor  117 . The software uses this information to calculate the desired positions for each of the print heads  102 ,  103  and  104 .  
         [0018]    Once determined, the positioning software instructs and/or controls actuators, such as positioning motors  105 ,  107  and  109  to reposition print heads  102 ,  103  and  104  respectively. For example, positioning motor  105  may reposition print head  102  by means of a track or guide  106 . In one embodiment of the current invention, guide  106  may include a rod with a screw-like helical pattern along its circumference which enables positioning motor  105  to rotate guide  106  such that screw threads engage complimentary threads at print head  102 , or any moveable carriage assembly into or on which print head  102  may be mounted. Thus, controlled rotation of guide  106  causes a linear translation of print head  102  in a direction perpendicular to a direction of movement of the print receiving media such that print head  102  is repositioned in the “Y” axis as shown by reference number  118 , while the print receive medium (in this example, envelope  101 ) moves in the “X” axis, as shown by reference number  119 .  
         [0019]    In one embodiment of the present invention, the threads of rod  106  may be orientated so that a clockwise rotation of guide  106  moves print head  102  towards motor  105 . The threads of  106  may be changed in such a manner that a clockwise rotation of rod  106  would move print head  102  away from motor  105 . Similarly, motor  107  uses guide  108  to position print head  103 , and motor  109  uses guide  110  to position print head  104 . Each of the motors  105 ,  107  and  109  preferably receives positioning information from the positioning software run by processor  117 . Processor  117  can be within printer  112 , or within an external CPU or partially within each.  
         [0020]    Still referring to FIG. 1, processing software resident on processor  117  may use the characteristics of printing medium  101  to determine the locations of print head  102 ,  103  and  104 , such as may be determined by analysis of print stream information, possibly including document size information, transmitted to a printer hosting the print heads of the present invention. For example, processor  117  may analyze a print stream to determine a physical arrangement of the text and/or image to be printed in order to position one or more of print heads  102 - 104  and/or to select an appropriate print head. Moreover, processor  117  may analyze the print stream to determine a particular print head suitable for printing aspects of the print job and, therefore, place that print head accordingly. Additionally or alternatively, sensory input, such as may detect physical attributes of the selected printing medium, may be utilized by processor  117  in determining locations of print heads  102 - 104 . In the embodiment illustrated in FIG. 1, print head  102  is used to print a bar code  116  on the printed medium  111 . Similarly, print head  103  is used to print address  113  on printed medium  111  and print head  104  is used to print return address  114  and proof-of-postage  115  on printed medium  111 .  
         [0021]    Structure in addition, or in the alternative, to that shown in FIG. 1 may be utilized according to the present invention. For example, a brake mechanism may be provided upon a print head, a print head actuator, a print head guide, and/or a chassis component in order to hold the print head, actuator, and/or guide from movement when a print head has been properly positioned. According to one embodiment, a brake mechanism is disposed upon a print head and coupled to processor  117  to be controllably engaged when the print head has been positioned. Additionally or alternatively, the actuator may be controlled to hold a print head&#39;s position, such as by application of a holding voltage or current.  
         [0022]    The invention is further subject to being incorporated in different embodiments. For example, while the print heads are shown staggered along a direction of travel of the print receiving media, they may instead be aligned in a linear array within a common or concentric track or guide structure. Further, while translation of the print heads is described using a motor and screw arrangement, other positioning may be used including stepper motors, rack and pinion gear arrangement, belt and pulley system, etc. Still further, multiple heads and paper handling apparatus may be dynamically positioned in response to particular print job requirements. For example, a color print head may be positioned to insert a color segment into an otherwise monochromatic (e.g., black and white) printed document such as to print a small photograph within a document. Similarly, stapling may be adjusted by proper positioning of a stapling apparatus relative to a particular medium, size, format, and related requirements. Note that the size of the printed image may require the use of two or more print heads and that not all print heads need be used for each and every print job. Further note that any material that can be deposited from any type of print head could be used in this device such as “postal mark” ink, “barcode” ink and similar marking material  
         [0023]    [0023]FIG. 2 shows a chart illustrating the steps performed according to one embodiment of the current invention. Referring to the flow chart of FIG. 2, a determination of the current position of one or more print heads is performed at step  201 . This determination may be made from sensors located along print head guides, from a position stored within the control mechanism, from a print head position stored within another system resource, or any other suitable method. A new desired position(s) for one or more print heads for the next print job is determined according to step  202 .  
         [0024]    The new positions preferably represent printing swaths required for the next identified print job. In particular, while the printer is printing the current print job, the print heads are positioned in a specific orientation to support the current print job. However, the next print job may require different print head positions. Thus, step  202  defines steps to gather information, or use information gathered, related to the next print job, or a queued print job, to determine the desired positions for the print heads. For instance, if the current print job is printing an address, a return address, and proof-of-postage for a wide envelope, the spacing between the print heads might need to be reduced in order to print the address, the return address, and the proof-of-postage on a narrow envelope. In step  202  the next queued (or anticipated) print job is examined to determine the characteristics of the next/expected print job. For example, if the next print medium is a narrow envelope, new positioning information for the print heads would be calculated to properly place the address, the return address, proof-of-postage and possibly a bar code on the narrow print medium.  
         [0025]    In step  203 , the differences between the current print head positions and the desired print head positions are calculated. These calculations are preferably to determine the movement desired for each of the print heads. Optional decision  204  determines if these are currently unused (inactive) print heads. If so, decision  205  determines if the unused print heads should be moved prior to completion of the current print job. If so, step  206  controls this process. If either decision  204  or  205  is no, (or not used), or when step  206  is finished, the process goes to step  207 , where, after the current print job is completed, the print heads are moved from their current position to the desired position for the next queued print job. Once the print heads have been moved, at step  208  the next print job is printed on the print receiving medium.  
         [0026]    The current invention may be applied to one or more print heads. For example, if the return address is preprinted on envelopes sent from a particular company, a single print head used to print recipient address information on the envelopes may be relocated to print address information onto the appropriate portion of both narrow envelopes and wide envelopes. Alternatively, more than one print head could be included in a printing system where the location of each of the print heads is determined in the flow chart of FIG. 2 as applied to position each of the print heads in a desired location. Also, if desired, a print head, or heads, not currently being used could be prepositioned to further reduce time between print jobs.