Patent Application
20050175387
The present invention relates generally to methods and apparatus for printing, and more specifically, to methods and apparatus for impact printing upon print receivable media.
Dot matrix line printers are well known in the industry. Dot matrix line printers have an elongated bank of hammers forming a print head. The print head is shuttled back and forth over a small number of character positions during printing. That is, rather than shuttling a small print head back and forth over the entire width of the paper during printing, the print head of a dot matrix line printer is wide and shuttled only over a few character positions. For example, the print head may include 66 dot printing elements located along a linear axis or line. Each of the dot printing elements is shuttled over two character positions. Thus, back and forth shuttling of the print head allows a maximum of 132 characters to be printed. As the print head is shuttled, the dot printing elements are selectively impacted to create dots. A series of lines of dots creates a row of characters or, alternatively, a graphic image.
Dot matrix line printers are often used to print upon a continuous web of print receivable media, such as paper, fabric, metal, synthetic materials, organic materials, etc. The continuous web of print receivable media may be formed from a series of sheets of paper coupled to one another in a head-to-toe (i.e., top-to-bottom) relationship. The sheets may be blank or may have forms pre-printed thereon. The sheets may also include two or more layers, such that one or more carbon copies may be simultaneously created by printing upon the top sheet.
Typically, the paper includes a pair of detachable drive strips coupled to the sides of the paper. The drive strips include a series of evenly spaced perforations designed to be engaged by a series of pins of a pair of drive tractors. The drive tractors engage the perforations in the drive strips to drive (move) the paper past the print head.
Many previously developed dot matrix line printers use two pairs of drive tractors to move paper and control paper tension when printing upon the paper. More specifically, such previously developed printers include a first pair of tractors (one tractor located on each side of the paper) located downstream of the print head, and a second pair of tractors located upstream of the print head. The two pairs of tractors work in tandem to move the paper across the print head while maintaining an appropriate amount of tension in the paper. Recently, in order to reduce the manufacturing costs of line printers, printers that employ only one pair of tractors to move the paper across the print head have been developed. Due to the difficulty of pushing paper through the narrow gap between a print head and a platen, the tractors of such printers are located downstream of the print head. As a result, the tractors pull the paper past the print head.
When only a single pair of drive tractors are used, paper tension becomes an important issue. It is important for good print quality that paper be kept taut during printing. Consistent paper tension may be provided in single tractor dot matrix line printers by a paper iron. A paper iron usually includes a cantilevered strip of spring material that pinches paper against the platen upstream of the print head. The paper iron is biased by the spring towards the platen so as to apply a consistent paper pinching force. The friction applied to the paper by the paper iron and the platen provides controlled, consistent paper tension.
Typically, the sheets forming a continuous web of paper are printed in a continuous manner. As a result, after one sheet is printed, the next sheet is printed without the first sheet being detached from the web. However, on occasion, a user may wish to detach the first sheet for use or review prior to the printing of the second sheet. This type of printing is often called single sheet printing.
In the past, when a printer having a single pair of pull drive tractors performed single sheet printing, the print could be no closer to the top edge of a sheet than the distance between the closest tractor pin and the print hammers of the print head. Due to the presence of a ribbon shield above the print hammers, this distance is usually greater than one inch. If printing is required closer than one inch to the top edge of the sheet, a sacrificial sheet must precede the sheet to be printed. The sacrificial sheet is used to preserve tractor engagement with the paper while the printer prints upon the sheet to be printed. Thus, two sheets are required for every one that is printed. Such printing can be expensive, especially if the sheets are preprinted forms or carbon copies are to be produced. A 50% print yield can significantly increase costs for single sheet printing employing single tractor dot matrix line printers and other types of printers, in particular impact printers, employing a single pair of tractors.
Therefore, there exists a need for single tractor dot matrix line and other printers and methods of printing employing such printers that provide for single sheet printing near the top and/or bottom margins of single sheets without requiring a sacrificial sheet.
In accordance with the present invention, a new and improved printer for printing on a continuous web of print receivable media is provided. One exemplary embodiment of a printer formed in accordance with certain aspects of the present invention includes a print head having a media drive assembly side. The printer further includes a media drive assembly for moving the media past the print head, the media drive assembly disposed only on the media drive assembly side of the print head. The printer also includes a platen disposed adjacent the print head and a controller coupled to the print head, the media drive assembly, and the platen for controlling a mode of operation of the printer in accordance with user input. The mode of operation of the printer includes a continuous print mode of operation and a single sheet mode of operation. During the continuous print mode of operation, the print head, the media drive assembly, and the platen are controlled such that the media is moved by the media drive assembly past the print head in a downstream direction. During the single sheet mode of operation using push printing, the print head, the media drive assembly, and the platen are controlled such that the media is moved by the media drive assembly past the print head in an upstream direction one sheet at a time.
In one exemplary embodiment, the controller controls the printer to print in a continuous pull printing manner. More specifically, the controller controls the media drive assembly to alternatingly advance the media by pulling the media past the print head and pause media movement during printing by the print head. The controller also controls the printer to print in a single sheet push printing manner. More specifically, the controller directs the media drive assembly to alternatingly advance the media by pushing the media past the print head and pause media movement during printing by the print head.
In yet another exemplary embodiment, the controller controls the printer to print on the media in a continuous pull printing manner. More specifically, the controller controls the media drive assembly to alternatingly advance the media by pulling the media past the print head and pause media movement during printing by the print head. The controller also controls the printer to print in a single sheet pull printing manner. More specifically, the controller controls the media drive assembly to push a sheet of the media past the print head and then alternatingly advance the media by pulling the media back past the print head and pause media movement during printing by the print head.
In accordance with other aspects of the present invention, a method of controlling a printer to perform continuous sheet printing, single sheet push printing, and/or single sheet pull printing is provided. The printer includes a print head for printing on a web of continuous print receivable media and a paper drive assembly having at least one driver for moving the media. The driver is located on the downstream side of the print head. The method includes determining if continuous sheet printing is desired, and if continuous sheet printing is desired, directing the media drive assembly to alternatingly: (i) pause printing and advance the media past the print head by pulling the media; and (ii) pause media movement while the print head prints. The method also includes determining if single sheet push printing is desired, and if single sheet push printing is desired, directing the media drive assembly to alternatingly: (i) pause printing and advance the media by pushing the media past the print head; and (ii) pause media movement while the print head prints. The method further includes determining if single sheet pull printing is desired, and if single sheet pull printing is desired, directing the media drive assembly to push a sheet of the media past the print head, and alternatingly: (i) pause printing and advance the media back past the print head by pulling the media; and (ii) pause media movement while the print head prints.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
A quantity of print receivable media, such as continuous printer paper 18, may be stored in a lower paper bin 52 (
The paper drive assembly 26 includes a pair of well known drive tractors 34 (one shown). The drive tractors 34 include a series of drive pins disposed on a flexible belt 36. The drive pins are spaced and sized to engage the perforations in the drive strips 22 (
Although the drive tractors of the paper drive assembly 26 are described as including flexible belts 36 for engaging perforations in a pair of drive strips 22 (
The print head 28 is an impact print head, preferably a dot matrix line printer print head. As well known to those skilled in the art, dot matrix line printer print heads include a bank of hammers that are shuttled back and forth over a small number of character positions during printing. That is, rather than shuttling a small print head back and forth over the entire width of the printer paper 18 and printing characters in a serial manner, a dot matrix line printer print head 28 is wide and shuttled only over a few character positions. For example, the print head 28 may include 66 dot printing elements, each shuttled over two character positions, thereby covering 132 character positions. One line of dots is printed during each half of the shuttle motion cycle.
The bank of hammers includes a plurality of hammer springs (not shown) mounted along the length of the print head 28 in a conventional manner. See, for example, U.S. Pat. Nos. 4,833,980 and 4,793,252, the disclosures of which are hereby expressly incorporated by reference. During printing, the hammer springs are selectively released or fired such that dot printing elements impact the printer paper 18 through a length of ink ribbon (not shown) thereby printing images on the printer paper 18.
The platen 30 is a movable anvil aligned with the bank of print hammers and receives the impact force created by the print hammers. The platen 30 is an elongate member, generally cylindrical in shape. While the platen 30 is generally uniform in size and shape along the length of the platen 30, the shape of the platen 30 varies around the circumference of the platen 30, i.e., the radius of the platen changes around the circumference. The variation in radial distance allows the rotation of the platen 30 to selectively adjust the size of a print gap or platen gap 38, i.e., the space or gap between the print head 28 and the opposing outer surface of the platen 30. The platen gap 38 is adjusted to: (1) accommodate varying thicknesses of printer paper 18; (2) manipulate the friction between the print head 28 and the platen 30; and/or (3) to assist the loading of printer paper 18. While the platen 30 may be manually rotated, preferably the platen is power rotated by a suitable motor or other well known platen rotation mechanism.
The platen 30 includes at one or both ends a paper iron disengagement arm 40. The arm 40 is positioned to selectively engage a paper iron 42 that forms part of the paper iron assembly 32. The engagement moves the paper iron 42 between a paper load position and a paper tension position, as will be described in more detail below.
The paper iron assembly 32 also includes a leaf spring 44. The paper iron 42 is affixed along one edge of the leaf spring 44. The other edge of the leaf spring 44 is affixed to a base 46 positioned such that the paper iron 42 is cantilevered from the base 46. The leaf spring 44 biases the paper iron 42 toward the platen 30.
The paper iron 42 is positionable between a paper load position (shown in
The printer 10 further includes two paper bins; a lower paper bin 52 and an upper paper bin 54. The paper bins 52 and 54 are sized and configured to hold the printer paper 18 in position for immediate use. Typically, the top edge of the paper will be loaded first since this is how the paper comes out of the box. Generally stated, when the printer paper 18 is loaded in the front of the printer in the lower paper bin 52, the print job is printed first line first, last line last and the print appears upright when viewed by a person standing in front of the printer. When the printer paper 18 is loaded in the back of the printer in the upper paper bin 54, the print job is printed last line first and first line last when pull printing. When push printing, the print job is printed first line first and last line last. The print will appear upside down when viewed by a person standing in front of the printer.
As will be understood from the following description of
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As will be readily appreciated by those skilled in the art and others, the first sheet of the printer paper 18, or at least the portion of the printer paper 18 located beyond the print head 28, cannot be printed on. However, subsequent sheets can be fully printed, from top to bottom. Because loss of the first sheet does not significantly reduce printing efficiency during continuous printing, this loss is not a significant issue. If one thousand sheets are printed after the first sheet, the ratio of wasted sheets to useable sheets is 1/1000. However, if single sheets are printed using this approach, i.e., wherein one sheet is printed on and then torn off before the next sheet is printed, the ratio of wasted sheets would be 1/1, since each printed sheet would require a sacrificial sheet. As shown in
When single sheets are to be printed, the printer mechanism 24 is operated in the reverse (backward) direction. The printer paper 18 is loaded from the upper (downstream) paper bin 54 located at the back of the printer and pushed past the print head 28 in a backward direction, as indicated by the arrow 50 in
Referring to
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Regardless of which single sheet printing mode of operation occurs—push printing or pull printing—the sheets are printed in a single sheet, zero wastage manner, i.e., a manner that allows a single sheet to be printed and torn off without the wastage of a first sacrificial sheet. In the single sheet push printing mode of operation, the sheet of the printer paper 18 to be printed on is loaded such that the top edge of the first sheet is under the print head 28. The first sheet of the printer paper 18 is then alternatingly pushed past the print head 28 and paused while printed on by the print head 28. This process continues as the sheet is printed, line by line, in a top to bottom manner. The full length of the sheet is available for printing. The printed sheet may then be pushed a sufficient distance past the print head 28 to permit a user to tear off the sheet for immediate use. The printer paper may then be pulled back toward the paper drive assembly 26 to align the top edge of the next sheet with the print head 28. The next sheet may then be printed on as the sheet is pushed past the print head 28. No sacrificial sheets are wasted.
The images (e.g., characters) printed on the sheets of the printer paper 18, when the paper is loaded from the upper bin 54 and fed in the backward direction, are preferably printed upside down relative to the orientation of the images printed when the printer paper is loaded from the lower bin 52 and fed in the forward direction. This is done so that the images are correctly oriented relative to any forms preprinted on the sheets of printer paper 18. More specifically, when continuous printer paper 18 is loaded from the lower bin side of the print head 28 and fed beginning to end in the forward direction, a preprinted form on the first sheet is oriented in a first direction. However, if the same continuous printer paper 18 is loaded from the upper bin side of the print head 28 and fed beginning to end in the backward direction, the printer paper 18 is now oriented upside down relative to the preprinted form. Any images printed on the printer paper 18 oriented and fed in this way need to be printed upside down relative to the orientation of the images when printed in the forward direction. Alternatively, continuous printer paper loaded from the upper bin side of the print head can be fed end to beginning in the backward direction. In this case, the form and printed images are oriented correctly, except that printing is from end to beginning in the push mode of operation. However, operation in this manner typically would require an operator to remove the continuous paper from its box to obtain access to the last sheet of the stack.
The routine then proceeds to decision block 210, where a test is made to determine if the printer paper has been loaded. As will be readily apparent to those skilled in the art and others, the determination of whether the printer paper has been loaded may be accomplished in any number of suitable ways, such as automatically by the use of any one of a number of well known sensors or in response to user input received from the user interface, for example. Decision block 210 remains in an endless loop until it is determined that the printer paper has been loaded. The routine then proceeds to block 212. At block 212, the platen is rotated to decrease the platen gap and to place the paper iron in the paper tension position. Thus, the printer is prepared to begin printing.
The routine then proceeds to block 214 where the images to be printed are processed for printing. Because continuous printing was requested (block 206), printing occurs in a rightside up manner. The routine then proceeds to block 216 where the first line of images is printed on the printer paper. As well known to those skilled in the art of line printers, if the images are a line of characters, this is accomplished by printing a “line” of dots indexing the printer paper, printing another line of dots, etc., until the first line of character images is printed. Other well known techniques are used to create pictures or other images. The routine then proceeds to block 218 where the printer paper is pulled a selected distance past the print head, the selected distance being to the next row of dots to be printed. The routine then proceeds to decision block 220, where a test is made to determine if the print job is complete. If the print job is not complete, blocks 216 and 218 are repeated until the print job is complete. After the print job is complete, the routine proceeds from decision block 220 to block 222. At block 222, the platen is rotated to increase the platen gap. After the platen gap is increased, the routine proceeds to block 224 where the printer paper is pulled past the print head to a position where the user can access (either visually or physically) the now printed paper, to either visually assess the printed images and/or tear off a sheet of printer paper. The routine then proceeds to block 226, where the process ends, i.e., the controller is shut down or placed in hibernation until a new printing process is begun at start block 202.
Returning to decision block 206, if it is determined that continuous printing was not requested, the routine proceeds to a single sheet printing subroutine 228. An exemplary single sheet printing subroutine 228 is illustrated in
At block 300 the single sheet printing subroutine begins. Processing promptly proceeds to block 301, wherein a test is made to determine if the printer paper was indicated (by the user) as sufficiently stiff (i.e., having a stiffness equal to or greater than a selected stiffness). As noted above, if the printer paper is of a sufficient stiffness, the printer paper can be pushed past the print head during printing without the printer paper buckling to a degree where print quality is significantly affected. If the paper is not stiff enough to be pushed past the print head during printing without significantly affecting print quality, the routine proceeds to a single sheet pull printing subroutine 324 illustrated in
If it is determined at decision block 301 that the paper is sufficiently stiff, the subroutine 228 proceeds to block 302 where the platen is rotated to increase the platen gap to facilitate the loading of printer paper. The printer paper is loaded from the upper paper bin 54, i.e., the leading end of the printer paper is brought into engagement with the pins 36 of the paper drive assembly 26. While this could be done automatically, in most printers embodying the invention, loading of paper will be done manually. The subroutine 228 then proceeds to decision block 304, where a test is made to determine if the printer paper has been loaded. The determination of whether the printer paper has been loaded may be accomplished through the use of any number of well known means, as discussed above with respect to block 210 (
At decision block 308, the images to be printed on the printer paper are processed for printing. The single sheet printing subroutine 228 then proceeds to block 310 where the platen is rotated to decrease the platen gap to facilitate printing by the print head. The gap size is chosen to minimize friction on the printer paper as the paper is pushed past the print head. The subroutine 228 then proceeds to block 312 where, as described above (block 216,
The routine then proceeds to decision block 316, where a test is made to determine if the print job is complete. If the print job is not complete, blocks 312 and 314 are repeated until the print job is complete. After the print job is complete, the subroutine 228 proceeds to block 318. At block 318, the platen is rotated to increase the platen gap. After the platen gap is increased, the routine proceeds to block 320 where the printer paper is pushed past the print head to a position where the user can access (either visually or physically) the now printed paper, to either visually assess the printed images and/or tear off a sheet of printed paper. The routine then proceeds to block 322, where the subroutine ends. Processing then returns to block 226 of
Returning to
The subroutine 324 then proceeds to decision block 402, where a test is made to determine if the printer paper has been loaded. The determination of whether the printer paper has been loaded may be accomplished through the use of any number of well known means, as discussed above with respect to block 210 (
At block 403, the images to be printed are processed for printing. During single sheet pull printing, images are printed in an upside down orientation.
The single sheet pull printing subroutine then proceeds to block 404, where the printer paper is pushed past the print head. Preferably, the printer paper is pushed past the print head to the point where one full sheet of the printer paper lies beyond the print head. The subroutine 324 then proceeds to block 406 where the platen is rotated to decrease the platen gap. The single sheet pull printing subroutine then proceeds to block 408 where the print head prints one image line of print, similar to the line of print printed in blocks 216 (
While the presently preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
