Abstract:
Thermal printer with bi-directional print head movement and method thereof. The invention comprises a more time efficient thermal printing mechanism ( 100 ) including an assembly of one thermal print head ( 111 ) or a first thermal print head ( 11   a ) and a second thermal print head ( 11   b ). Either of the print heads being adapted with at least one universal bi-directional stepping motor ( 121 ) controlling the movement of the thermal printing head ( 111 ) or one universal bi-directional stepping motor ( 222 ) controlling the movement of the first thermal printing head ( 11   a ) and the second thermal printing head ( 11   b ). The invention also comprises a method of generating a hard copy ( 113 ) comprising only one ejection step from either the thermal printing mechanism ( 100 ) using one print head ( 111 ) or the thermal printing mechanism ( 200 ) using the first thermal printing head ( 11   a ) and the second thermal printing head ( 11   b ). The thermal printing mechanism ( 100 ) and the thermal printing mechanism ( 200 ) each uses a line by line sequential printer row of elements ( 113   a ) or dual rows of elements ( 312   a ) and ( 312   b ). The thermal printing mechanism ( 100 ) with one printing head ( 111 ) operates bilaterally in relation to the flow direction of the thermal printing medium ( 314 ). Alternatively, the thermal printing mechanism ( 200 ) simultaneously operates dual thermal printing heads ( 11   a ) and ( 11   b ) bilaterally with one universal stepping motor ( 222 ) operating bi-directionally with only one ejection for release of a thermally sensitive hard copy output media ( 413 ). The printing head ( 111 ) is adapted to print using a single source of donor material ( 116 ). A pair of print heads ( 11   a ) and ( 11   b ) are adapted to use a single source ( 316 ) of donor material with the source ( 316 ) providing color media sections ( 315 ) and ( 318 ) such as yellow and magenta. Another pair of print heads ( 411   a ) and ( 411   b ) are adapted to use a plurality of output spools ( 416   a ) and ( 416   b ) of donor material with each of the donor media output spools ( 416   a ) and ( 416   b ) providing a different color such as yellow and magenta, respectively, or cyan and black, respectively.

Description:
FIELD OF THE INVENTION  
         [0001]    The present novel invention relates generally to a thermal printer adapted to more efficiently print a thermal hard copy output resulting in less time to produce a thermal print. More specifically, the present invention relates to a thermal printing mechanism and method of utilizing a bilateral single head printer or multiple heads for printing alternate or multiple rows simultaneously in multiple colors.  
         BACKGROUND OF THE INVENTION  
         [0002]    Technology related to the novel invention is disclosed in Japan Patent No. 8,072,282 assigned to Fuji. Also, U.S. Pat. No. 5,367,321 assigned to Kyocera, discloses an electrical circuit system comparable to that used in the novel improved invention. The problem of improving print speed in related printers is addressed in both Japan Patent No. 6,127,267 assigned to Sharp and U.S. Pat. No. 4,774,529 assigned to Xerox. Of further background relevance are Japan Patent No. 7,214,870 assigned to Brother Kogyo; U.S. Pat. No. 5,196,864 assigned to Eastman Kodak; and, Japan Patent No. 7,184,410 assigned to Silver Seiko.  
           [0003]    More relevant is Japan Patent No. 8,072,282 which discloses the use of three staggered print heads arranged linearly to improve print speed and Japan Patent No. 6,127,267 wherein two parallel electrodes provide simultaneous recording. Japan Patent No. 7,214,870 also discloses an arrangement wherein one or more print heads are arranged in parallel.  
           [0004]    For additional background purposes, U.S. Pat. No. 5,367,321 issued to Shigenori, et al. discloses multiple insulating substrates to form a linear heating element in a thermal printer and U.S. Pat. No. 4,774,529 suggests a printing system for increasing the speed of a multi-color printer when utilized in a single color mode by repositioning the recording head cartridge from a first level to a second level to enable two lines of information to be created during a single scanning pass when it has been determined by the electronic means to be of the same color.  
           [0005]    Other art appears in U.S. Pat. No. 5,196,864 wherein a multiple print head thermal printer is disclosed.  
           [0006]    U.S. Pat. No. 4,946,297; U.S. Pat. No. 5,000,595; and, Japan Patent No. 7,184,410 refer to the use of four separate line print heads being mounted and teaches how to split a line into four prints using four separate print heads and then joining the line together.  
           [0007]    Today&#39;s thermal printers are designed with one thermal head and multiple donor media types. Typically, the donor media is composed of multiple areas of different donor material which are mechanically linked in a specific sequential order. Typically, three areas of color specific donor material are required for a photographic quality thermal hard copy print. For a typical donor today, that sequence of color specific donor material may be yellow, magenta, and cyan. Other donor materials may be composed of a base sequence of four color specific donor areas: yellow, magenta, cyan, and black. The particular sequence of donor material (whatever that may be) is repeated in a serial fashion to complete a roll of donor material.  
           [0008]    Referring to prior art, FIG. 1, in producing a thermal hard copy output, donor material (usually the least thermally active color, yellow  15 ) is positioned over the thermal paper  13 . Mechanical rollers  16  and  17 , edge and color sensors are used to recognize and position the desired donor material color over the thermal output paper. A thermal head  11 , in which pixels  12  (typically 300 per inch) are arranged in a linear fashion, is positioned at the edge of the thermal paper. Digitized control data is then applied to each pixel simultaneously (usually pulse modulated) such that a row or line of one color is printed onto the thermal paper. Through stepper motors and mechanics, and control logic, for example, such as disclosed by the electrical circuit system in Kyocera which is adopted and incorporated herein by reference, either the thermal print head or thermal output paper is advanced one line or row and the thermal transfer process is repeated for that row. This whole sequence is repeated until one color is thermally transferred onto one full sheet of desired thermal output paper. The thermal paper is projected, as shown in prior art FIG. 1 b,  donor material is advanced to the next color area, and the thermal output paper is re-inserted, as shown in prior art FIG. 1 c.  The entire process is repeated until the next color (for example, magenta  18 ) in the sequence is transferred onto the thermal output paper. This process is repeated again with donor material advancing to the next color area until all colors of the donor material are transferred or thermally printed onto the thermal output paper. The problem with this process is that it requires a relatively lengthy time period to complete. More particularly, it is time-consuming, mechanically intensive and requires four paper projections for a donor composed of four independent color areas per each thermal print.  
           [0009]    The novel invention resolves the problem of lengthy time consumption and four paper projections for a donor composed of three independent color areas for each thermal print. Specifically, the novel invention significantly reduces the required projections and mechanical steps, and thereby the printing time necessary for a thermal printer to produce a thermal print.  
         SUMMARY OF THE INVENTION  
         [0010]    An object of this invention is to provide a novel combination of steps in a thermal printer printing process wherein the output paper is retained and thermal printing occurs in a bilateral direction instead of a unilateral direction and wherein the output paper is ejected after the application of each color.  
           [0011]    This object is achieved by a novel integration of a preferred embodiment thermal printer mechanism having a donor media which contains a yellow media section, a magenta media section, a cyan media section, and a black media section, all of which are positioned mechanically between the thermal print head and the thermal output media by the rotation of two roller spools. In addition, the thermal print head contains a mounting mechanism that works like a universal socket wherein the thermal head is precisely positioned over the donor media at the correct angle when the head is traveling in a left to right motion as well as a right to left motion. The stepper motor control is adapted to direct a bi-directional stepper motor and comprises the electronics therefor.  
           [0012]    One of the most outstanding advantages of the present invention is that the use of the above described mechanical and electrical combination significantly increases the printing speed of thermal head printers approximately 30% or more.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 a  is a perspective view of a first aspect of an internal printing mechanism in a prior art printer;  
         [0014]    [0014]FIG. 1 b  is a perspective view of a second aspect of the internal printing mechanism in the prior art printer;  
         [0015]    [0015]FIG. 1 c  is a perspective view of a third aspect of the printing mechanism in the prior art printer;  
         [0016]    [0016]FIG. 2 a  is a perspective view of a first aspect of an internal printing mechanism which depicts a first preferred embodiment of a printing mechanism of the novel invention;  
         [0017]    [0017]FIG. 2 b  is a perspective view of a second aspect of the internal printing mechanism which depicts the first preferred embodiment of the printing mechanism of the novel invention;  
         [0018]    [0018]FIG. 2 c  is a perspective view of a third aspect of the internal printing mechanism which depicts a first preferred embodiment of the printing mechanism of the novel invention;  
         [0019]    [0019]FIG. 2 d  is a perspective view of a fourth aspect of the internal printing mechanism which depicts the first preferred embodiment of the printing mechanism of the novel invention;  
         [0020]    [0020]FIG. 2 e  is a perspective view of a fifth aspect of the internal printing mechanism which depicts the first preferred embodiment of the printing mechanism of the novel invention;  
         [0021]    [0021]FIG. 2 f  is a perspective view of a sixth aspect of the internal printing mechanism which depicts the first preferred embodiment of the printing mechanism of the novel invention;  
         [0022]    [0022]FIG. 3 depicts a first alternative embodiment wherein separate multiple thermal heads and a single donor media spool are utilized for printing; and,  
         [0023]    [0023]FIG. 4 depicts a second alternative embodiment wherein juxtaposed multiple thermal heads and multiple donor media spools are utilized for printing.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    In IG.  1   a  there is shown a printer mechanism  10  of a prior art printer and an illustration of the prior art method of operation. As further shown in greater detail in FIGS. 1 a,    1   b , and  1   c,  these prior art thermal printers were designed to produce hard copy output  13  starting at a leading edge  13   a  and printing to a trailing edge  13   b  with one thermal head  11 , thermal heating elements (or pixels)  12 , and multiple donor media  14 .  
         [0025]    Typically the donor media  14  of the prior art as illustrated in FIGS. 1 a,    1   b,  and  1   c  are composed of multiple areas of the donor media  14  which are mechanically linked in a specific sequential order. There is shown a yellow donor media  15  located in between a first donor media spool  16  and a second donor media spool  17 . There also is a magenta donor media  18 . As illustrated in FIGS. 1 a  and  1   b,  in the prior art at least two areas of color specific donor media  14  are required for a photographic quality thermal hard copy print. For typical donor media  14  today, that sequence of color specific donor material is yellow, magenta, and cyan. Other donor materials may be composed of a base sequence of four color specific donor areas: yellow, magenta, cyan, and black. The particular sequence of donor material (whatever that may be) is repeated in a serial fashion to make up a complete roll or spool of donor material.  
         [0026]    In producing the thermal hard copy output  13  , donor material (usually the least thermally active color) is first positioned over the hard copy output  13 , e.g. thermal paper. Mechanical rollers, edge and color sensors are used to recognize and position the desired donor material color over the thermal output paper. A thermal head, in which pixels (typically 300 per inch) are arranged in a linear fashion, is positioned at the edge of the thermal paper. Digitized control data is then applied to each pixel simultaneously (usually pulse modulated) such that a row or line of one color is printed onto the thermal paper. Using stepper motors and mechanics, and control logic well known in the art, either the thermal print head  11  or the hard copy output  13  or thermal paper is advanced one line or row and then the thermal transfer process is repeated for that line or row. This whole well known sequence is repeated until one color is thermally transferred onto one full sheet of desired hard copy output  13 . The thermal paper is projected, donor material is advanced to the next color area, magenta  18 , as shown in FIG. 1 b.  The hard copy output  13  or thermal output paper as shown in FIG. 1 b  is re-inserted and the magenta color is printed as shown in FIG. 1 c.  The entire process is repeated until the next color in the sequence is transferred onto the thermal output paper. As shown in FIG. 1 b  and  1   c,  this well known prior art process is repeated again with donor material advancing to the next color area of a plurality of color areas issuing from the first donor media spool  16  to the second donor media spool until all colors of the donor media  14  are transferred or thermally printed onto the hard copy output  13  or thermal output paper.  
         [0027]    The above described prior art process as generally illustrated in FIGS. 1 a,    1   b,  and  1   c  is characterized by engineers in the art as mechanically intensive because this prior art process requires no less than four (4) paper projections for a donor composed of a like number or three (3) independent color areas for each full color thermal print (typically a clear coat is printed over all colors). The resulting prior art process, as briefly shown in FIGS. 1 a,    1   b,  and  1   c,  is a thermal process requiring an extended period of time, To. The novel invention as illustrated in FIGS. 2 a,    2   b,    2   c,    2   d,    2   e,    2   f  and FIGS. 3 and 4 significantly reduces the processing time T 0  by approximately 20% to 50% to a new processing time T N . Thereby, with the novel arrangement of donor elements and printing heads illustrated in FIGS. 2 a  through  4 , printing time for a thermal printer is significantly and substantially reduced such that T 0 −(0.20)T 0 =T N .  
         [0028]    Referring again to FIG. 1 a,  a detailed description of the prior art printing process is as follows. The prior art printing mechanism  10  contains a thermal head  11  which contains thermal heating pixels. There are  300 - 440  elements  12  or pixels per inch in density, for example. The mechanism  10  also contains a thermally active donor material  14  which is mechanically positioned between the thermal head  11  and the hard copy output media  13 , for example thermal paper. A specific color from the donor material  14  is provided by advancing (virgin) donor material  14  of various colors such as yellow  15  via two spools  16  and  17 , respectively. When completed, the hard copy output media  13  or thermal paper is ejected from the printing mechanism  10  housed internally in a printer housing (not shown for clarity) and positioned onto a customer retrieval shelf  118 .  
         [0029]    As previously described, the prior art sequence and method of printing is depicted in FIGS. 1 a,    1   b,  and  1   c.  Specifically, in FIG. 1 a,  the thermal head  11  commences a first step of printing by transferring yellow donor media  15  at the leading edge  13   a  opposite from the trailing edge  13   b  associated with the hard copy output  13 . Via a single linear array of the individual elements  12 , pulse width modulation commands, the thermally active donor material  14  is preferentially heated on a pixel by pixel basis for the entire line or row. Typically, the head  11  moves in a left to right motion or from the leading edge  13   a  to the trailing edge  13   b  of the thermal paper in a controlled fashion, transferring electronically selected colors from the donor material  14  from a raster or bit map function for the next line or row of the hard copy output  13 . In the first step of this sequence all the appropriate yellow thermal media  15  is transferred to the entire area of the thermal hard copy output  13 .  
         [0030]    Shown in FIG. 1 b , the thermal output  13  is temporarily ejected to the customer retrieval shelf  118 . While this ejection step occurs, in a second step the thermal head  11  is repositioned to a position where the leading edge  13   a  of the thermal hard copy output media  13  was initially located.  
         [0031]    As shown in FIG. 1 c , the (virgin) donor media  14  is advanced by the step of simultaneously rotating the spools  16  and  17  in a like direction, respectively, such that the next color to be printed, for example donor media magenta  18 , is in a position between the thermal head  11  and the thermal output  13 .  
         [0032]    It should be noted that notwithstanding whether the exact sequence of the above described prior art steps is utilized, the inventor has discovered that a common element in the prior art sequencing is that the thermal output paper or more specifically the thermal output  13  is always ejected at an intermediate step in the sequencing of the prior art printing process as illustrated in FIGS. 1 a,    1   b,  and  1   c.    
         [0033]    In addition, the improvement represented in the novel invention is based partly on recognition of a unique attribute of the prior art, namely, that prior art thermal printing occurs in a unilateral direction. See, for example, FIGS. 1 a,    1   b  and  1   c.  First, there is shown the yellow donor media  15 . It is printed from left to right. Next, the paper is ejected, the thermal head  11  is moved in the z direction, the donor media is advanced to magenta  18 , the thermal head  11  is lowered, and finally, the magenta  18  is printed from left to right where required by raster or bit mapping functions on a pixel by pixel or thermal element basis one row at a time until the entire output  13  has been thermally printed. In FIG. 1 b  the thermal output  13  is shown temporarily ejected and in FIG. 1 c  the color specific printing process repeats itself again.  
         [0034]    A first preferred embodiment for the mechanism and steps of the novel invention are depicted in FIGS. 2 a  through  2   f.  There is shown an arrangement which utilizes a preferred embodiment thermal printing mechanism  100 . The preferred embodiment thermal printing mechanism  100  contains a thermal head  111  with elements  112 . It also contains a thermally sensitive output media  113  having a leading edge  113   a,  a trailing edge  113   b,  and a customer retrieval shelf  218 . In addition, the preferred embodiment thermal printer mechanism contains donor media  114  which further contains a yellow media section  115  located between a first donor media spool  116  and a second donor media spool  117 . There is also a magenta media section  181 , a cyan media section  119 , and a black media section  120 . All of said media sections are adapted for positioning mechanically between the thermal print head  111  and the thermally sensitive output media  113  by the likewise rotation of the first donor media spool  116  and the second donor media spool  117 . In addition, the thermal print head  111  contains a mounting mechanism, i.e., a universal stepping motor  121 . With the universal stepping motor  121  connected to the thermal print head  111  it is precisely mechanically positioned over the donor media  114  at electronically pre-selected time intervals and at an electronically pre-selected angle as the print head  111  is traveling in a left to right direction and also when the thermal print head  111  is traveling intermittently in an opposite or right to left direction. Thus, a customary stepper motor control for the universal stepping motor  121  is altered and adapted using known and available mechanical means to operate the thermal print head  111  bi-directionally.  
         [0035]    A novel sequence of operation for the preferred embodiment of thermal printer mechanism  100  is fully illustrated in FIGS. 2 a,    2   b,    2   c,    2   d,    2   e,  and  2   f.  In FIG. 2 a,  the yellow media section  115  is positioned between the thermal head  111  and the output media  113  via the rotation of spools  116  and  117 . The thermal head  111  is positioned intermittently at pre-selected heights and angles by the universal stepper motor  121 . The novel mechanism and thermal printing process initially operates and progresses, respectively, as in the prior art initial sequencing up to the completion of printing all of the yellow color  115  to the thermal output paper edge  113   b.  In the novel printer mechanism  100  and in the method of its operation, instead of temporarily projecting the thermal output  113  onto the customer retrieval shelf  218  (as previously illustrated in FIG. 1 b ), the donor media  114  is advanced as shown in FIG. 2 b  until a magenta media section  181  is positioned over the thermal output media  113  via likewise rotation of the rollers  116  and  117  by employing the use of well known color donor sensors (not shown) and well-known motor control techniques. The thermal head  111  is temporarily moved away in a vertical or z-direction from the advancing donor medial  14  and then lowered prior to restarting the printing process for the next color media, for example, the cyan media section  119  as illustrated in FIG. 2 c.  The bi-directional universal stepper motor  121 , repositions the thermal print head  111  at a pre-selected angle in preparation for the next step of reverse printing (right to left). There is shown in FIG. 2 b  the step wherein the thermal print head  111  actuates a line of thermal printing elements  112   a  at the trailing edge  113   b  and prints the magenta media section  181  sequentially towards the leading edge  113   a  and onto the thermal output media  113 .  
         [0036]    Referring to FIG. 2 c,  the thermal head  111  ends up at the left or leading edge  113   a  of the output media  113  after the step of printing the magenta media section  181 . The next step is the macro process of printing the cyan media section  119  in a leading edge  113   a  to trailing edge  113   b  direction (left to right). In FIG. 2 e  is the step of printing the black media section  120  in a reverse right to left direction. This is similar to the previous description of the step of printing the yellow media section  115  and the magenta media section  181 , respectively, as shown and described previously referencing FIGS. 2 a  and  2   b.  In the novel sequencing of steps using the preferred printing mechanism  100 , the step of ejection of the thermal output media  113  as illustrated FIG. 2 f,  occurs only after completion of the steps of printing all colors or media sections.  
         [0037]    A first temporary ejection (not illustrated) of the thermal output media  113  can electively occur after the first complete pass of the print head  111  from the leading edge  113   a  to the trailing edge  113   b  (left to right) for the color yellow  115 . Referring now to FIG. 2 c,  on the next sequence of printing from the trailing edge  113   b  to leading edge  113   a  (right to left) another elective second temporary ejection of the thermal output media  113  may occur. In the novel structure and method of the invention, at least three temporary projections are eliminated using bi-directional or bilateral printing. The total printing time T 0  using prior art sequencing is significantly reduced to T N  using the novel invention whereby T 0 &gt;&gt;T N .  
         [0038]    In FIG. 3, there is shown a first alternate or second preferred embodiment wherein a printing mechanism  200  utilizes two separate thermal heads  11   a  and  11   b.  Each is connected to a separate but equivalent universal stepping motor  222  adapted to operate bi-directionally. The print mechanism  200  uses a single donor media spool  316  and an uptake spool  317 . The alternative embodiment is enabled by using the stepper motor  222  as a unidirectional stepper means to control the movement of both heads  11   a  and  11   b . The heads  11   a  and  11   b  have a first heating element set  312   a  and a second heating element set  312   b,  respectively. Thus, the first alternative embodiment as shown in FIG. 3 is adapted with the additional steps of sequentially moving thermal output media  313  having a leading edge  313   a  and a trailing edge  313   b  in two directions: for example, first in a right to left direction, after which head  11   a  transfers yellow from a yellow media section  315  of a spooled donor media  314  in a left to right direction starting from the leading edge  313   a  of the thermal output media  313 . After yellow has been completely transferred to the thermal output media  313  as previously described, the thermal output media  313  moves in a left to right direction and wherein after which the thermal output media  313  is positioned such that head  11   b  transfers magenta color from the magenta media section  318  of the thermal donor media  314 . As a further alternative step, the spooled donor media  314  can be mechanically sequenced to move in a right and in a left direction to achieve a reduction in the overall size physical size of the spooled donor media  314  when the two heads  11   a  and  11   b  are both utilized to transfer color from the same sections of the spooled donor media  314 .  
         [0039]    The novel method is completed by repeating the above step as described for the color yellow such that in addition to sequential printing of the colors yellow and magenta, next the color cyan and then the color black is printed using the thermal elements  312   a  and  312   b,  respectively. Hence, the color cyan (not shown) is printed like the color yellow  315  and the color black (not shown) is printed like the color magenta  318 . Only one output paper ejection step is utilized and required. A substantial time savings of at least 20% is realized due to having only one paper ejection step instead of three as required and utilized by prior art printers.  
         [0040]    The novel arrangement of the printing mechanism  200  shown in FIG. 3 provides additional time savings by employing the two separate print heads  11   a  and  11   b  and by the repositioning thereof serially with like serially scheduled or programmed printing times. In the novel assembly and operation of the printing mechanism  200  the first thermal print head  11   a  is repositioned as the second thermal head  11   b  is printing and vice versa.  
         [0041]    A third alternative preferred embodiment for the novel operating structure is shown in FIG. 4. This novel arrangement for a printing mechanism  300  provides at least two adjacent thermal heads  411   a  and  411   b  and at least two sets of related juxtaposed donor media spools  416   a,    416   b,  and  417   a,    471   b,  respectively. The printing mechanism  300  is made up of a combination of first and second thermal heads  411   a  and  411   b  and a spooled donor media  414   a  at the left of the hard copy output media  413  and a spooled donor media  414   b  at the right of the hard copy output media  413 . The donor media  414   a  is mechanically and fixedly connected in-between a first donor media output spool  416   a  and a first donor media input spool  417   a.  The donor medium  414   b  is mechanically and fixedly connected in-between two roller mechanisms  416   b  and  417   b.  In this last described embodiment, it is significant to recognize that the printing mechanism  300  is merely a simple exemplary embodiment. This alternative novel embodiment can be expanded to include more than two sets of donor mediums in a donor mechanism and more than two donor mechanisms with a like increase in printing heads such as  411   a  and  411   b.  It should be noted that these two donor mechanisms  416   a  and  416   b  may easily number three, four, or more mechanisms or N mechanisms where N is an integer and N≧2. This embodiment results in an overall improvement in printing time due to the parallel feature of printing with two heads which result in less additive donor spooling time, less additive time to move the thermal head in the z direction and the ability to print 1.5 colors for each complete pass of one of the two thermal heads.  
         [0042]    In yet another alternate structure or fourth embodiment, the printing mechanism  300  is as shown in FIG. 4 and described above. With the two printing thermal heads  411   a  and  411   b  and two spools  416   a  and  416   b  of donor media, respectively, at least two colors can be simultaneously printed with simultaneously activated print heads. The novel invention is adapted to accomplish this operational level by employing known stepper motor control technology to simultaneously operate thermal heads  411   a  and  411   b  and/or, alternatively a stepper motor control for the two spools  416   a  and  416   b  of donor media. Basically, one head  411   a  thermally prints all pixels within a row  412   a  at the leading edge of the paper  413   a.  The other or second head  411   b  thermally prints all pixels within a row  412   b  at the trailing edge  413 B of the thermal output media  413 .  
         [0043]    In yet a second alternate structure to the 4 th  embodiment, a mechanical arrangement the thermal heads  411   a  and  411   b  are controlled by a stepper motor (not shown), then thermal head  411   b  is located {fraction (1/2)} the distance of the donor medium  414   a  which is mechanically and fixedly connected in-between the two roller mechanisms, for example spools  416   a  and  417   a,  and is adapted to move in the direction of the printing process. The thermal printing head  411   a  is positioned at the leading edge  413   a  of the thermal output media  413 . Both heads  411   a  and  411   b  travel during the same time interval in unison in a reverse direction with the head  411   b  beginning at the trailing edge  413   b  of the thermal output media  413 . The head  411   a  thermally prints {fraction (1/2)} or midway across the thermal output media  413  while the  411   b  thermally prints {fraction (1/2)} or midway across the thermal output media  413  in a sequencing of steps for operation of the printing mechanism  300 . As thermal head  411   a  completes 100% of its&#39; printing process, thermal head  411   b  will have printed 50% of its&#39; printing process and so on. Therefore, a printing time efficiency equal to or greater than 50% per two thermal colors is achieved since the print head  411   a  completes 50% of its operational task during the same time interval the head  411   b  is operational.  
         [0044]    In FIG. 4, two spools of thermal donor media  414   a  and  414   b  are depicted wherein spool  414 A is shown to contain yellow media  415  and cyan media  419 . The donor media  414   b  is shown to contain magenta media  418  and black media  420 . All media described are thermally activated to print.  
         [0045]    The two donor media  414   a  and  414   b  can be increased by one of ordinary skill to four sets of donor media with one of each of four heads adjacent and underneath each set of donor media wherein, for example, spool  414   a  is 100% yellow media; spool  414   b  is 100% magenta media; and by linear extrapolation a spool  414   c  (not shown) is 100% cyan media and interposed between the spools  414   a  and  414   b;  and  414   c  (not shown) is 100% black media and also interposed between the spools  414   a  and  414   b.  The operation of this arrangement results in a time savings of approximately 63% for the entire printing process with an additional increase in efficiency associated with the time savings for head mechanical alignment and positioning of the multiples heads simultaneously and the time savings associated with multiple thermal output media projection times, thus significantly reducing total printing time.  
         [0046]    As thermal heads have become cheaper and smaller and are now more widely used in consumer applications, the third embodiment is economically viable for large scale production. It should be noted that it is well known to those in this art that with certain known types of thermal output media, the density of printing elements or pixels is increased, sometimes by a factor of 2 to print four separate pixels in an equivalent 300 dpi density due to the color science of printing one color before another and vice versa in different areas of the same output media.  
         [0047]    The invention has been described in detail with particular reference to a first preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the novel invention and subject to the doctrine of equivalents.  
       PARTS LIST  
       [0048]    [0048] 10  prior art printer mechanism  
         [0049]    [0049] 11  thermal print head  
         [0050]    [0050] 11   a  first thermal print head  
         [0051]    [0051] 11   b  second thermal print head  
         [0052]    [0052] 12  thermal heating elements  
         [0053]    [0053] 13  hard copy output  
         [0054]    [0054] 13   a  leading edge of hard copy output  
         [0055]    [0055] 13   b  trailing edge of hard copy output  
         [0056]    [0056] 14  donor material  
         [0057]    [0057] 15  yellow donor media  
         [0058]    [0058] 16  first donor media spool  
         [0059]    [0059] 17  second donor media spool  
         [0060]    [0060] 18  donor media magenta  
         [0061]    [0061] 100  first thermal printing mechanism  
         [0062]    [0062] 111  thermal print head  
         [0063]    [0063] 112  heating elements  
         [0064]    [0064] 113  thermally sensitive output media  
         [0065]    [0065] 113   a  leading edge of thermally sensitive output media  
         [0066]    [0066] 113   b  trailing edge of thermally sensitive output media  
         [0067]    [0067] 114  donor media  
         [0068]    [0068] 115  yellow media section  
         [0069]    [0069] 116  first donor media spool  
         [0070]    [0070] 117  second donor media spool  
         [0071]    [0071] 118  customer retrieval shelf  
         [0072]    [0072] 119  cyan media section  
         [0073]    [0073] 120  black media section  
         [0074]    [0074] 121  universal stepping motor  
         [0075]    [0075] 181  magenta media section  
         [0076]    [0076] 200  first alternate printing mechanism  
         [0077]    [0077] 218  customer retrieval shelf  
         [0078]    [0078] 222  universal stepping motor  
         [0079]    [0079] 312   a  first heating element set  
         [0080]    [0080] 312   b  second heating element set  
         [0081]    [0081] 313  thermal output media  
         [0082]    [0082] 313   a  leading edge of thermal output media  
         [0083]    [0083] 313   b  trailing edge of thermal output media  
         [0084]    [0084] 314  spooled donor media  
         [0085]    [0085] 315  yellow media section  
         [0086]    [0086] 316  single donor media spool  
         [0087]    [0087] 317  uptake media spool  
         [0088]    [0088] 318  thermally sensitive donor media with magenta  
         [0089]    color donor area  
         [0090]    [0090] 319  thermally sensitive donor media with cyan color donor area  
         [0091]    [0091] 320  thermally sensitive donor media with black color donor area  
         [0092]    [0092] 300  alternate third thermal printing mechanism  
         [0093]    [0093] 411   a  first thermal print head  
         [0094]    [0094] 411   b  second thermal print head  
         [0095]    [0095] 412   a  heating elements of thermal head  411   a    
         [0096]    [0096] 412   b  heating elements of thermal head  411   b    
         [0097]    [0097] 413  thermally sensitive hard copy output media  
         [0098]    [0098] 413   a  leading edge  
         [0099]    [0099] 413   b  trailing edge  
         [0100]    [0100] 414   a  spooled donor media  
         [0101]    [0101] 414   b  spooled donor media  
         [0102]    [0102] 415  thermally sensitive donor media with yellow color donor area  
         [0103]    [0103] 416  first donor media spool  
         [0104]    [0104] 417  second donor media spool  
         [0105]    [0105] 416   a  first donor media output spool  
         [0106]    [0106] 416   b  second donor media output spool  
         [0107]    [0107] 417   a  first donor media input spool  
         [0108]    [0108] 417   b  second donor media input spool  
         [0109]    [0109] 418  thermally sensitive donor media with magenta color donor area  
         [0110]    [0110] 419  thermally sensitive donor media with cyan color donor area  
         [0111]    [0111] 420  thermally sensitive donor media black color donor area