Abstract:
A method of producing a printing on a surface of a foil by an energizable printing head and a thermal transfer ribbon including an ink which is transferable in an ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated temperature by the energizable printing head causing the ink to be fluid. The thermal transfer ribbon is arranged in facial contact with the surface of the foil. The energizable printing head is arranged in contact with the thermal transfer ribbon opposite to the foil. The foil and the energizable printing head are moved relative to one another at a specific speed while pressing the energizable printing head and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, and while energizing the energizable printing head. The thermal transfer ribbon is moved relative to the energizable printing head at a reduced speed as compared to the specific speed of the foil relative to the energizable printing head. Consequently the thermal transfer ribbon is moved relative to the foil for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to the foil at specific areas thereof constituting the printing so as to smear the ink of the thermal transfer ribbon at the specific locations onto the foil through the motion of the thermal transfer ribbon relative to the foil.

Description:
This is a Continuation application of PCT/DK99/00017, filed on Jan. 12, 1999, and a Continuation-in-Part application of application Ser. No. 09/120,335, filed on Jul. 22, 1998 now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the technique of producing a printing on a foil by means of a thermal transfer ribbon in an ink transfer operation. 
     The present invention relates in particular to the technique of producing a printing on a foil in a thermal printing operation during a packaging operation in which the foil is used as a packaging foil or as an information foil sheet to be applied to or below a wrap around or packaging foil for packaging a product being an organic or inorganic product. The examples of products relevant in the present context are unlimited ranging from toys, cosmetics, consumer products, foodstuffs drugs etc. In general, any product which is to be packed in a foil or to be applied with an information printing after the product has been included in a separate package may be relevant in the present context. The invention in general relates to high speed printing and packaging operations in which the foil on which the printing is to be applied is moved at a speed up to several hundred millimetres per second. 
     BACKGROUND OF THE INVENTION 
     It is known to print continuous packaging materials constituting foil materials and other continuous printing media such as paper materials for producing labels with alfanumeric information and symbols, information, logos etc. while using a thermal printing or thermal transfer techique. According to the thermal transfer technique, a thermal transfer ribbon including an ink is heated at specific locations to an elevated temperature causing the ink to be fluid and at the same time, the the transfer ribbon is contacted with the prin media such as the foil or paper material in question for causing the transfer of the fluid ink to the foil material or paper material. In the ink transfer operation, the thermal transfer ribbon is moved in synchronism with the print media or foil to which the printing is to be applied and the amount of thermal transfer ribbon material which is used in a high speed printing and packaging operation performed at a speed of several hundred millimetres per second may, as will be readily understood, be extremely high as the thermal transfer ribbon is also moved at the same high speed as the foil material amount to a speed of transportation of the order of several hundred metres per second. 
     Examples of prior art thermal printers of the above kind are described in EP 0 157 096, EP 0 176 009, EP 0 294 633, U.S. Pat. Nos. 5,297,879, 3,984,809, 4,650,350, 4,642,655, 4,650,350, 4,712,115, 4,952,085, 5,017,943, 5,160,943, 5,162,815, 5,576,751, 5,609,425 and 5,647,679 to which reference is made and which U.S. patents are hereby incorporated in the present specification by reference. 
     From the technical field of paper recorders, it is known to utilize a thermal transfer ribbon and produce a printing on a piece of paper by sandwiching the thermal tranfer ribbon between a printing head or recorder head and the paper sheet on which the printings are to be produced. It is known in paper recorders of this kind to reduce the speed of thermal transfer ribbon relative to the speed of the paper sheet for saving the amount of transfer ribbon used and consequently obtain a reduction in costs and improve the economical efficiency of the paper recorder. Examples of paper recorders of this type are shown in Japanese patent publication (Kokoku) No. 62-58917), Japanese patent application laying open (Kokai) No. 63-165169, U.S. Pat. Nos. 5,121,136, 5,372,439 and 5,415,482. Reference is made to the above patent applications and patents and the above US patents are hereby incorporated in the present specification by reference. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a novel technique of producing high speed printings on a print media such as a foil allowing substantial material savings as far as the thermal transfer ribbon is concerned without to any substantial extent deteriorating the quality of the printing produced as compared to the prior art thermal printing techniques. 
     It is a further object of the present invention to provide a novel thermal printing technique rendering it possible with a substantial ribbon material saving to establish an even improved printing quality as compared to the prior art thermal printing technique by providing an improved utilization of the therms transfer ribbon material as compared to the utilization of the thermal transfer ribbon material in accordance with the prior art thermal printing technique. 
     An advantage of the present invention relates to the fact that a thermal transfer ribbon material saving up till 80% may be obtained without to any substantial extent deteriorating the printing quality as compared to the prior art thermal printing technique. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a first aspect of the present invention obtained by means of a method of producing a printing on a surface of a foil by means of energizable printing means and a thermal transfer ribbon including an ink which is transferable in an ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated teperature by means of the energizable printing means causing the ink to be fluid, comprising the following steps: 
     arranging the thermal transfer ribbon in facial contact with the surface of the foil, 
     arranging the energizable printing means in contact with the thermal transfer ribbon opposite to the foil, 
     moving the foil and the energizable printing means relative to one another at a specific speed while pressing the energizable printing means and the foil together so as to sandwich thermal transfer ribbon therebetween in a constrained state, and while energizing the energizable printing means, and 
     moving the thermal transfer ribbon relative to the energizable printing means at a reduced speed as compared to the specific speed of the foil relative to the energizable printing means and consequently moving the thermal transfer ribbon relative to the foil for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to the foil at specific areas thereof constituting the printing so as to smear the ink of the thermal transfer ribbon at the specific locations onto the foil through the motion of the thermal transfer ribbon relative to the foil. 
     Contrary to the prior art thermal printing technique in which the thermal transfer ribbon is moved in synchronism with the foil to which the printing is to be applied in the relative motion of the foil relative to the energizable printing means, it has been realized that the speed of motion of the thermal transfer ribbon relative to the energizable printing means may be reduced as compared to the speed of motion of the foil relative to the energizable printing means providing a substantial saving of thermal transfer ribbon material without reducing or deteriorating the quality of the printings produced. According to the prior art thermal transfer printing technique, the ink is transferred from a thermal transfer ribbon in a process of establishing facial contact between the thermal transfer ribbon and the foil during the process of moving the foil without causing any mutual movement between the thermal transfer ribbon and the foil as it has been considered mandatory to the obtaining of a high quality printing that no deviation between the movement of the thermal transfer ribbon and the foil should be allowed which mutual movement inevitably would deteriorate the printing quality. According to the teachings of the present invention, it has been realized that the quality of the printing process is by no means deteriorated provided the thermal transfer ribbon and the foil are moved relative to one another as the ink transfer process is converted from a facial contact transfer process into a combined facial contact transfer process and a smearing process in which the ink is smeared onto the foil from the thermal transfer ribbon. It is believed that the combined facial contact transfer operation and the smearing transfer operation of the ink from the thermal transfer ribbon to the foil provides an increased utilization of the ink content of the thermal transfer ribbon as compared to the prior art exclusive facial contact transfer operation. 
     The energizable printing means may according to the teachings of the present invention be constituted by any appropriate heating means for causing local heating at specific locations of the thermal transfer ribbon such as a laser, a pin head or preferably and advantageously a printing head including individual energizable printing elements. 
     According to a first implementation or embodiment of the method according to the first aspect of the present invention, the foil is moved continuously while the energizable printing means are stationary and the thermal transfer ribbon is moved relative to the foil and relative to the energizable printing means while the energizable printing means are heated during the ink transfer operation and kept stationary relative to the energizable printing means while the energizable printing means are not heated. 
     According to a second implementation or embodiment of the method according to the first aspect of the present invention, the foil is moved continuously while the energizable printing means are stationary and the thermal transfer ribbon is moved relative to the foil and relative to the energizable printing means while the energizable printing means are heated during the ink transfer operation and moved in the reverse direction relative to the energizable printing means while the energizable printing means are not heated so as to utilize an used part of the thermal transfer ribbon in a subsequent ink transfer operation. 
     According to a third implementation or embodiment of the method according to the first aspect of the present invention, the foil is moved intermittently and kept stationary during the ink transfer operation while the energizable printing means and the thermal transfer ribbon being moved relative to the stationary foil while the energizable printing means are heated during the ink transfer operation and moved in the reverse direction relative to the energizable printing means while the energizable printing means are not heated so as to utilize an unused part of the thermal transfer ribbon in a subsequent ink transfer operation. 
     According to a particular aspect of the present invention as far as the thermal transfer ribbon saving aspect concerned, it has been realized that in numerous instances and in particular in printing on packages, packaging foils or the like, a substantial transfer ribbon saving may be obtained provided the printings to be produced are slightly re-located from one printing operation to another without changing the geometric configuration of the printing. The above described second and third implementation or embodiment of the method according to the first aspect of the present invention constitute embodiments in the present context to be referred to as “side shift technique” and “retraction technique”, respectively, which are to be considered independent aspects of the present invention as will be disclosed below. 
     In accordance with the thermal ribbon saving aspect of the present invention, a specific ink transfer operation is preferably performed utilizing a part of the thermal transfer ribbon not previously used in a preceding ink transfer operation and preferably further, the part of the thermal transfer ribbon used for the specific ink transfer operation being positioned at least partly transversly offset relative to that part of the thermal transfer ribbon used in a preceding ink transfer operation in order to use the maximum amount of the thermal transfer ribbon as compared to a printing technique not involving “side shifting technique” or “retraction technique”. 
     The method according to the first aspect of the present invention may be operated at a high production rate corresponding to a high specific speed of the foil relative to the energizable printing means of the order of 50-1,000 mm/sec, such as of the order of 100-500 mm/sec, preferably of the order of 200-500 mm/sec, while said reduced speed constitutes 20-98%, such as 20-50% or 50-98% of said specific speed or alternatively constitutes 20-30%, 30-40%, 40-50% 50-60%, 60-70%, 70-80%, 80-90% or 90-98% of said specific speeds. Alternatively, the specific speed may be of the order of 100-200 mm/sec, 200-300 mm/sec, 300-400 mm/sec. 400-500 mm/sec, 500-600 mm/sec, 600-700 mm/sec, 700-800 mm/sec, 800-900 mm/sec or 900-1,000) mm/sec, while said reduced speed constitutes 20-30%, 30-40%, 40-50% 50-60%, 60-70%, 70-80%, 80-90% or 90-98% of said specific speed. 
     The foil material to which the printing is to be applied may be any appropriate plastics or inorganic or organic material such as a PE or a PVC foil, a woven or non-woven platics foil or a paper foil, aluminum foil or a combination thereof. 
     The printing head which according to the presently preferred embodiment of the method according to the first aspect of the present invention constitutes the energizable printing means may preferably include energizable printing elements arranged at a mutual spacing of the order of 0.05 mm-1 mm, such as of the order of 0.1 mm-0.5 mm, preferably approximately 0.1 mm. 
     The above objects an the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a second aspect of the present invention obtained by means of a method of producing a printing on a surface of a foil by means of energizable printing means and a thermal transfer ribbon including an ink which is transferable in an ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated temperature by means of the energizable printing means causing the ink to be fluid, comprising the following steps: 
     arranging the thermal transfer ribbon in facial contact with the surface of the foil, 
     arranging the energizable printing means in contact with the thermal transfer ribbon opposite to the foil, and 
     moving the foil and the energizable printing means relative to one another at a specific speed while pressing the energizable printing means and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, and while energizing the energizable printing means, for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to foil at specific areas thereof constituting the printing the foil being moved continuously while the energizable printing means are stationary and the thermal transfer ribbon being moved relative to the energizable printing means while the energizable printing means are heated during the ink transfer operation and moved in the reverse the direction relative to the energizable printing means while the energizable printing means are not heated so as to utilize an used part of the thermal transfer ribbon in subsequent ink transfer operation. The method according to the second aspect of the present invention may advantageously be implemented in accorrdance with the above described preferred and advantageous implementations or embodiments of the method according to the first aspect of the present invention. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a third aspect of the present invention obtained by means of a a method of producing a printing on a surface of a foil by means of energizable printing means and a thermal transfer ribbon including an ink which is transferable in an ink transfer operation at specific locations of said thermal transfer ribbon by heating said specific locations to an elevated temperature by means of said energizable printing means causing said ink to be fluid, comprising the following steps: 
     arranging said formal transfer ribbon in facial contact with said surface of said foil, 
     arranging said energizable printing means in contact with said thermal transfer ribbon opposite to said foil, and 
     moving said foil and said energizable printing means relative to one another at a specific speed while pressing said energizable printing means and said foil together so as to sandwich said thermal transfer ribbon therebetween in a constrained state, and while energizing said energizable printing means, for causing said ink of said thermal transfer ribbon to be transferred at said specific locations to said foil at specific areas thereof constituting said printing said foil be moved continuously while said energizable printing means are stationary and said thermal transfer ribbon being moved relative to said foil and relative to said energizable printing means while said energizable printing means are heated during said ink transfer operation and moved in the reverse direction relative to said energizable printing means while said energizable printing means are not heated so as to utilize an used part of said thermal transfer ribbon in a subsequent ink transfer operation. The method according to the third aspect of the present invention may advantageously be implemented in accordance with the above described preferred and advantageous implementations or embodiments of the method according to the first aspect of the present invention. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a fourth aspect of the present invention obtained by means of a method of producing a plurality of individual printings on a surface of a foil by means of energizable printing means and a thermal transfer ribbon defining a specific width along a transversal direction thereof and including an ink which is transferable in an ink transfer operation by heating the thermal transfer ribbon at specific locations thereof to an elevated temperature by means of the energizable printing means causing the ink to be fluid, each of the printings defining a maximum dimension along a direction coinciding with the transversal direction constituting no more than 50% of the width, comprising the following steps: 
     (a) arranging the thermal transfer ribbon in facial contact with the surface of the foil, 
     (b) arranging the energizable printing means in contact with the thermal transfer ribbon opposite to the oil, 
     (c) moving the foil and the enerizable printing means relative to one another at a specific speed and moving the thermal transfer ribbon relative to the energizable printing means in the ink transfer operation while pressing the energizable printing means and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, and simultaneously energizing the energizable printing means causing the ink to be transferred to the foil at a first area thereof producing a first printing on the foil at one of the longitudinal edges of the thermal transfer ribbon, 
     (d) relocating the thermal transfer ribbon relative to the energizable printing means while the energizable printing means are not heated so as to utilize an unused part of the thermal transfer ribbon and repeating step (c) to provide a second printing on the foil at the opposite longitudinal edge of the thermal transfer ribbon. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a first aspect of the present invention obtained by means of a thermal printed for producing a printing on the surface of a foil in an ink transfer operation, comprising: 
     means for supplying the foil to the thermal printer, 
     a thermal transfer ribbon including an ink which is transferable in the ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated temperature causing the ink to be fluid, 
     means for arranging the thermal transfer ribbon i facial contact with the surface of the foil, 
     energizable printing means for heating the specific locations of the thermal transfer ribbon to the elevated temperature in the ink transfer operation, 
     means for energizing the energizable printing means, 
     means for pressing the energizable printing means and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, 
     means for moving the foil and the energizable printing means relative to one another at a specific speed while pressing the energizable printing means and the foil together an while energizing the energizable printing mean, and 
     means for moving the thermal transfer ribbon relative to the energizable printing means at a reduced speed as compared to the specific speed of the foil relative to the energizable printing means and consequently moving the thermal transfer ribbon relative to the foil for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to the foil at specific areas thereof constituting the printing so as to smear the ink of the thermal transfer ribbon at the specific locations onto the foil through the motion of the thermal transfer ribbon relative to the foil. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a sixth aspect of the present invention obtained by means of a thermal printer for producing a printing in the surface of a foil in an ink transfer operation comprising: 
     means for supplying the foil to the thermal printer, 
     a thermal transfer ribbon including an ink which is transferable in the ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated temperature causing the ink to be fluid, 
     means for arranging the thermal transfer ribbon i facial contact with the surface of the foil, 
     energizable printing means for heating the specific locations of the thermal transfer ribbon to the elevated temperature in the ink transfer operation, 
     means for energizing the energizable printing means, 
     means for pressing the energizable printing means and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, 
     means for moving the foil and the energizable printing means relative to one another at a specific speed while pressing the energizable printing means and the foil together and while energizing the energizable printing means, and 
     means for moving the thermal transfer ribbon relative to the energizable printing means at a reduced speed as compared to the specific speed of the foil relative to the energizable printing means and consequently moving the thermal transfer ribbon relative to the foil for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to the foil at specific areas thereof constituting the print the energizable printing means being stationary and the means for moving the foil and the energizable printing means relative to one another causing the foil to move relative to the energizable printing means in a continuous motion and the means for moving the thermal transfer ribbon relative to the energizable printing means moving the thermal transfer ribbon relative to the energizable printing means at the reduced speed while the energizable printing means are heated during the ink transfer operation and moving the thermal transfer ribbon relative to the energizable printing means in the reverse direction relative to the energizable printing means while the energizable printing means are not heating so as the utilize an unused part of the thermal transfer ribbon in a subsequent ink transfer operation. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a seventh aspect of the present invention obtained by means of a thermal printer for producing a printing on the surface of a foil in an ink transfer operation, comprising: 
     means for supplying the foils to the thermal printer, 
     a thermal transfer ribbon including an ink which is transferable in the ink transfer operation at specific locations of the thermal transfer ribbon by heating the specific locations to an elevated temperature causing the ink to be fluid, 
     means for arranging the thermal transfer ribbon i facial contact with the surface of the foil, 
     energizable printing means for heating the specific locations of the thermal transfer ribbon to the elevated temperature in the ink transfer operation, 
     means for energizing the energizable printing means, 
     means for pressing the energizable printing means and the foil together so as to sandwich the thermal transfer ribbon therebetween in a constrained state, 
     means for moving the foil and the energizable printing means relative to one another at a specific speed while pressing the energizable printing means and the foil together and while energizing the energizable printing means, and 
     means for moving the thermal transfer ribbon relative to the energizable printing means at a reduced speed as compared to the specific speed of the foil relative to the energizable printing means and consequently moving the thermal transfer ribbon relative to the foil for causing the ink of the thermal transfer ribbon to be transferred at the specific locations to the foil at specific areas thereof constituting the printing the means for moving the foil and the energizable printing means relative to one another causing the foil to move intermittently and maintaining the foil stationary during the ink transfer operation and causing the energizable printing means to move relative to the stationary foil and the means for moving the thermal transfer ribbon relative to the energizable printing means moving the thermal transfer ribbon relative to the energizable printing means at the reduced speed while the energizable printing means are heated during the ink transfer operation and moving the thermal transfer ribbon in the reverse direction relative to the energizable printing means while the energizable printing are not heated so as to utilize an unused part of the thermal transfer ribbon in a subsequent ink transfer operation. 
     The above objects and the above advantage together with numerous other objects, advantages and features which will be evident from the below detailed description of preferred embodiments of the present invention are in accordance with a eighth aspect of the present invention obtained by means of a thermal printer for producing a plurality of individual printings on the surface of a foil in an ink transfer operation, comprising: 
     means for supplying said foil to said thermal printer, 
     a thermal transfer ribbon defining a specific width along a transversal direction thereof each of said printings defining a maximum dimension along a direction coinciding with said transversal direction constituting no more than 50% of said width and including an ink which is transferable in said ink transfer operation at specific locations of said thermal transfer ribbon by heating said specific locations to an elevated temperature causing said ink to be fluid, 
     means for arranging said thermal transfer ribbon i facial contact with said surface of said foil, 
     energizable printing means for heating said specific locations of said thermal transfer ribbon to said elevated temperature in said ink transfer operation, 
     means for energizing said energizable printing means, 
     means for pressing said energizable printing means and said foil together so as to sandwich said thermal transfer ribbon therebetween in a constrained state, 
     means for moving said foil and said energizable printing means relative to one another at a specific speed 
     means for moving said transfer ribbon relative to said energizable printing means in said ink transfer operation while pressing said energizable printing means and said foil together and while energizing said energizable printing means causing said ink to be transferred to said foil at a first area thereof producing a first printing on said foil at one of the longitudinal edges of said thermal transfer ribbon, and 
     said means for moving said thermal transfer ribbon relative to said energizable printing means causing said thermal transfer ribbon to be relocated relative to said energizable means while said energizable printing means are not heated so as to utilize an unused part of said thermal transfer ribbon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is now to be further described with reference to the drawings, in which 
     FIG. 1 is an overall perspective and schematic view of a first and presently preferred embodiment of a printing apparatus according to the present invention, illustrating a feature of saving thermo-transfer ribbon by decelerating the thermal-transfer ribbon, 
     FIG. 1 a  is a part of a perspective and schematic view similar to the view FIG. 1 illustrating a further feature of saving thermal transfer ribbon by side-shifting during the printing operation, 
     FIG. 1 b  a part of a perspective and schematic view similar to the view of FIG  1   a  illustrating a further feature of saving thermo-transfer ribbon through retraction during the printing operation, 
     FIG. 2 is a perspective and schematic view of a printing assembly of the first embodiment of the printing apparatus in a disassembled state disclosing the interior of the printing assembly, 
     FIG. 3 is a perspective and schematic view of a part of the printing assembly shown in FIG. 2, as the printing assembly is illustrated from the opposites side as compared to the view of FIGS. 1 and 2, 
     FIG. 4 is a schematic view illustrating the overall operation of the printing apparatus illustrated in FIG. 1, 
     FIG. 5 a  is a perspective and schematic view illustrating a printing assembly of a further, or second, embodiment of the printing apparatus according to the present invention, illustrating the feature also illustrated in FIG. 1 of saving thermo-transfer ribbon through decelerating the thermo-transfer ribbon, 
     FIG. 5 b  is a perspective and schematic view similar to the view of FIG. 5 b  illustrating the feature of saving thermo-transfer ribbon also illustrated in FIG. 5 a  through side-shifting during print operation, 
     FIG. 5 c  is a perspective and schematic view similar to the views of 
     FIGS. 5 a  and  5   b  illustrating the further feature of saving thermo-transfer ribbon through retraction during the printing operation, 
     FIG. 6 a perspective and schmatic view similar to the view of FIG. 6 of a still further, or third, embodiment of a printing apparatus according to the present invention, 
     FIG. 7 is a a block diagrammatic view of the electronic circuitry of the first and presently preferred embodiment of the printing apparatus shown in FIG. 1, 
     FIGS. 8 a - 8   c  are diagrammatic views illustrating in greater details the electronic circuitry of the first embodiment of the printing apparatus shown in FIG. 1, 
     FIGS. 9 a - 9   q  are flow charts illustrating a first mode of operation of the first and presently preferred embodiment of the printing apparatus shown in FIG. 1, and 
     FIGS. 10 a - 10   v  are flow charts illustrating a second mode of operation of the first and presently preferred embodiment of the printing apparatus shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1-3, a first and presently preferred embodiment of a printing apparatus implemented in accordance with the teachings of the present invention is shown and designated the reference numeral  10  in its entirety. The apparatus basically comprises two parts or sections, a printing assembly  12  to be described in greater detail below with reference to FIGS. 2 and 3 and a control assembly or housing  14 , the structure of which is illustrated in FIGS. 7 and 8 a - 8   c , and the function of which for controlling the overall operation of the printing apparatus  10  is illustrated in FIGS. 9 a - 9   q.    
     The printing apparatus  10  is mounted in a frame, not shown, in greater detail, of a packaging apparatus or similar apparatus in which a continuous foil  16  is to be applied with a large number of printings. The foil  16  may constitute any appropriate foil of a material allowing the printing of a number of prints by means of a heat transfer foil, such as conventional polymer foil materials used in the packaging industry or for packaging purposes. Examples of relevant foil materials are PE, PVC, PP of woven or non-woven structured and organic fibre materials, such as paper materials or combined paper and polymer foil materials. The foil  16  is supplied from a foil supply reel  18  mounted on a stationary shaft  20  and guided round two rollers  22  and  24  of the packaging apparatus, which rollers define a substantially horizontal path of travel of the foil  16 . The printing assembly  12  is positioned above the roller  24  and establishes the printing of the printings on the foil  16  as the foil  16  passes by the roller  24  in its continuous high-speed motion. It is in this context to be realized that the foil  16  may be travelling at a speed of several hundred mm/s, such as a speed of 2-300 mm/s, or even more. 
     It is further to be realized that the orientation of the foil  16  and the orientation of the printing apparatus as illustrated in FIG. 10 is by no means mandatory in relation to the teachings of the present invention as the foil  16  may travel along a path differing from the horizontal, or substantially horizontal, path of travel illustrated in FIG. 1, such as a sloping or a vertical path of travel, and similarly, the printing apparatus  10  may be mounted or arranged so as to apply printings on the foil of an orientation differing from the horizontal, or substantially horizontal, 
     From the roller  24 , the foil  16  to which printings  26  are applied, as will be described in greater detail below, travels on and is guided below a further roller  28 . The rollers  22 ,  24  and  28  all constitute idler rollers and the foil  16  is caused to travel by means of a drive roller  30  which cooperates with a capstan roller  32 . The drive roller  30  is caused to rotate defining a peripheral speed of travel corresponding to the speed of travel of the foil  16  by means of a motor  34  which is connected to the roller through a gear assembly  38 . The motor  34  may constitute any AC or DC motor, the operation and speed of which may be controlled by means of an external motor controller, not shown in the drawings. The drive motor  34  receives electric power through a power supply cord  36  from an external power supply source being an AC or DC power supply source. The capstan roller  32  cooperates with the drive roller  30  for causing the foil  16  to move as the capstan roller  32  contacts the outer surface of the roller  30  and causes the foil  16  to move as is well-known in the art per se. 
     The idler rollers  22  and  28  and the capstan roller  32  are made from steel, whereas the drive roller  30  is a roller provided with an elastomeric outer surface, such as a rubber surface which may be slightly deformed through contact with the capstan roller  32 . The drive roller  24  is also provided with an elastomeric outer surface constituting a soft deformable surface, such as a Teflon surface, providing a counter surface during a printing operation. 
     The rotational motion of the foil  16  is detected by the control assembly  14  of the printing apparatus  10  by means of a detector or encoder  40  which supplies an electric control or encoder signal to the control assembly  14  through a signal wire  42 . The detector or encoder  40  may be constituted by a contact or non-contact detector or encoder based on inductive, capacitive or optic detecting principles well-known in the art per se. In the embodiment illustrated in FIG. 1, the detector or encoder  40  is constituted as a contact encoder which comprises a rotating wheel  44  which transfers the rotational motion of the roller  30  to an optic detector  46  for generating pulses representing the rotational motion of the drive roller  30  and consequently the motional travel of the foil  16 . 
     For operating the printing mechanism of the printing assembly  12 , the printing apparatus  10  receives pressurized air from an external pressurized air source through a supply tubing  48  and through a pressurized air valve  50  which controls the supply of pressurized air to the printing apparatus  10  through a pressurized air inlet tube  52 . The pressurized air valve  50  receives a signal from the control assembly  14  through an electric wire, not shown in the drawings. The function of the pressurized air supply will be evident from the below discussion of the structure and function of the printing assembly  12 . The printing assembly  12  is composed of two parallel plate or wall elements  54  and  56  which are kept in spaced-apart relationship by means of distance elements, including a hollow element  58 , and by means of a locking element which is operated by means of a locking lever  60  shown in FIG. 1 in solid line in its locked position and shown in FIG. 1 in its unlocked or released position. The locking position of the locking lever  60  is defined by a pin  62  and the unlocked position or released position of the locker lever  60  is defined by a further pin  64 . The plate element  54  constitutes a rear plate or rear wall supporting a solenoid-actuated pressurized air supply valve to be described below and supported on a bracket  66 . The plate element  56  constitutes a front plate or front wall supporting a handle  68  by means of which the front plate  56  and the components and elements supported on the front plate  56  may be held when the front plate  56  is separated from the rear plate  54 , as is illustrated in FIG. 2, provided the locker lever  60  is in the unlocked or released position shown in dotted line in FIG.  1 . The handle  68  is in FIG. 1 illustrated in a recessed position and in FIG. 2 shown in an extracted position, allowing the handle  68  to be used for gripping and holding the front wall  56 . 
     Within the inner-space defined between the rear plate  54  and the front plate  56 , a heat-transfer ribbon is moved in an intermittent motion controlled by the controller assembly  14  for establishing the printings  26  on the foil  16 . The various element of the printing mechanism received within the inner-space defined between the rear wall  54  and front wall  56  will be described below with reference to FIG.  2 . The terms “inner” and “outer” and equivalent terms are used in the present context referring to the inner space defined between the rear wall  54  and front wall  56 . 
     The controller assembly  14  is housed within a housing  70  which defines a front plate  72  in which a display  74  is provided together with a number of keys  76  for programming and operating the controller assembly  14  and the printing apparatus  10  along with a number of control lamps  78  and display elements  80  which serves the purpose of presenting information to the operator concerning the programming of the controller assembly  14 , and also the operation of the overall printing apparatus  10 . The various keys, lamps and display elements  80  are not to be described in greater detail, as these elements may be configured and implemented in accordance with specific requirements, or alternatively may be elimimated provided the printing apparatus is configured so as to perform one single preset and specific printing operation which is addressed or controlled and monitored by an external source, such as a remote PC-based controller. 
     In FIG. 2, the inner-space defined within the rear plate  54  and the front plate  56  is revealed, disclosing the components of the printing mechanism contained within said inner-space. The rear plate  54  supports, as stated above, the tubular element  58  which serves the purpose of receiving and arresting a pin element  82  supported by and protruding inwardly from the front plate  56 . A further pin element  84  is provided protruding inwardly from the front plate  56 . The pin element  84  is adapted to be received within a bore  86  of a block  88  which is rigidly connected to the rear wall  55  and includes a recess for receiving an arm  90  which is journalled pivotally relative to the block  88 , and consequently the rear wall  54 , on an inner shaft of the block  88 . The arm  90  supports at its outer distal end a printing head  100  and may be raised and lowered during the process of disassembling and assembling the printing assembly  10  for allowing easy access to the interior of the printing assembly as the arm  90  is biased towards its raised position shown in FIG. 2 by means of a sprinting included within the block  88 . 
     Apart from the pin elements  82  and  84 , four additional pins  92 ,  94 ,  96   98  and  99  protrude inwardly from the front plate  56 , serving the purpose of maintaining the front plate in a specific spaced-apart relationship relative to the rear wall  54  as the pin elements  82  and  84  are received within the bores of the block  88  and the tubular element  58 , respectively, provided the front plate  56  is locked in its locked position as the locking lever  60  is in the position illustrated in solid line in FIG.  1 . 
     The locking lever  60  cooperates with a locking pin  102  which at its outer distal end is provided with a transverse minor pin  104 . As the front plate  56  is positioned juxtaposed the rear plate  54  as the pins  82  and  84  are received within the respective bores of the block  88  and the tubular element  58 , respectively, and kept in its intentional spaced-apart relationship relative to the rear wall  54 , the locking pin  102  is received within an inner bore  106  of a locking element  108  which is journalled on a rotating shaft  110  supported by the rear wall  54  and which is provided with outwardly extending wing elements  114  and  116 . On the rotating shaft  110 , a cam element  112  is mounted for cooperating with the outer distal end of the arm  90 . As the locking lever  60  is rotated from its unlocked position shown in dotted lines in FIG. 1 to its locked position shown in solid line in FIG. 1, the transverse pin  104  of the locking pin  102  causes through its cooperation with the locking element  108  the shaft  110  to rotate in its counter-clockwise direction, causing the cam  112  to be lowered and rotated 90° in the counter-clockwise direction urging the outer distal end of the arm  90  downwardly, causing the printing head  100  to be lowered. Similarly, when the locking lever  60  is rotated from its locked position shown in solid line in FIG. 1 to its unlocked position shown in dotted lines in FIG. 1, the arm  90  is raised as the cam  112  is rotated clockwise from its lowered position, not shown in FIG. 2, to the position shown in FIG.  2 . 
     The locking of the front plate  56  relative to the rear plate  54  is establish as the element  106  is rotated 90° counter-clockwise from its position shown in FIG. 2, causing the outwardly extending wing elements  114  and  116  to be locked and arrested behind locking brackets  118  and  120  supported by the front wall  56 . The front wall  56  further supports an inwardly protruding shaft  122  on which a thermo-printing ribbon reel  124  is received and supported from which a thermo-printing ribbon  130  is supplied. The thermo-printing ribbon  130  is delivered from the reel  124  as the reel  124  is rotated on the shaft  122 , still, the rotation of the reel  124  relative to the shaft  122  is controlled through a braking spring  126  serving the purpose of preventing that the ribbon  130  is freely delivered from the reel  124  in a non-tensioned mode. Furthermore, a rotably mounted tensioning pin  86  is provided which is mounted on a rotating arm  87  for catching up any slack in the ribbon  130  and for collecting a length of the ribbon  130  delivered from the reel  124 . The tensioning pin  86  is spring-biased in the counterwise direction and is of importance not only as far as compensating for any ribbon material delivered from the reel  124 , but also for allowing the printing apparatus to reverse the direction of movement of the ribbon  130  relative to the printing head  100  in certain operations to be described below and referred to as “side shift technique” and “retraction technique” to be described below with reference to FIGS. 1 a  and  1   b.  The ribbon  130  is guided round the distance pins  92 ,  94 ,  96  and  98  defining a lower horizontal path which is kept substantially parallel to the path of travel of the foil  16  when the print assembly  12  is in the assembled state illustrated in FIG.  1 . From the distance pin  98 , the ribbon  130  is guided around a drive roller  128  which is driven by a motor assembly supported by the rear wall  54  and further guided from the drive roller  128  round the distance pin  99  and collected on a take-up reel  132 . The take-up reel  132  is connected to the drive roller  128  through a belt drive mechanism including a toothed belt  134  which is driven by a drive gear wheel  136  of the drive shaft  128  and further cooperates with a gear wheel  138  of the take-up reel  132 , which gear wheel  138  is connected to the take-up reel  132  through a frictional clutch compensating for the change of diameter of the take-up reel  132  as the ribbon  130  is collected on the take-up reel  132  in the transmission of the rotation of the drive shaft  128  to the take-up reel  132 . 
     The inner side of the rear wall  54  is illustrated in the upper left-hand part of FIG.  2  and the outer side of the rear wall  54  is illustrated in FIG.  3 . The rear wall  54  supports a motor assembly for actuating the drive roller  128  of the front plate  56 , which motor assembly includes a motor  140  arranged at the outer side of the rear plate  54  and protruding outwardly relative thereto. The motor  140  has its output shaft extending through the rear plate  54  and connected to a drive pulley  142  positioned at the inner side of the front plate  54 , which drive pulley  142  cooperates with a belt  144  cooperating with a drive shaft  146  which is journalled on a journalling bearing  148  and protrudes inwardly into the inner space defined within the printing assembly  112  and cooperates with the drive roller  128  as the drive shaft  146  is received within the drive roller  128  when the front wall  56  is received and locked in position relative to the rear plate  54 . 
     The motor assembly further includes a tensioning pulley  149  which serves the purpose of establishing a preset and specific tensioning of the drive belt  144 . As will be understood, the rotational motion of the output shaft of the motor  140  is transmitted through the drive pulley  142 , the belt  144  and the drive shaft  146  to the drive roller  128  when the front plate  56  is positioned and locked relative to the rear plate  54  as described above. 
     In FIG. 3, a printed circuit board  150  is shown, including the motor control electronics for control the function and operation of the motor  140 . The printed circuit board  150  is connected to the controller assembly  14  through two multicore cables  152  and  154  and is connected to the motor  140 , and optionally detectors of the printing assembly for detecting whether or not the front plate  56  is properly positioned and locked relative to the rear plate  54 . In the below description of the electronic circuitry of the printing apparatus  10 , a detector  180 , not shown in FIG. 2, is described serving the above purpose. As is evident from FIGS. 2 and 3, a further multicore cable  156  is provided for establishing connection between the printing head  100  and the control assembly  14 . 
     The arm  90  is, as discussed above, caused to be raised through the biasing from the bias spring contained within the block  88  to its raised position shown in FIG. 2, provided the cam  112  is in its raised position also shown in FIG.  2 . As the shaft  110  is rotated 90° clockwise, the cam  112  forces the arm  90  downwardly, positioning the printing head  100  in its stand-by position ready for performing a printing function. 
     The outer end of the arm  90  is provided with a printing head suspension block  160  in which the printing head  100  is suspended pivotally. The printing head  100  journalled pivotally relative to the suspension block  160  by means of a rotating shaft  162  and is urged to a raised position by means of a biasing spring  164 , forcing the printing head  100  to be raised or lifted upwardly relative to the foil  16  in its stand-by mode. When a printing operation is to be performed, the printing head  100  is lowered as the pressurized air supplied to the printing assembly  12  through the pressurized air-inlet tube  52  is further supplied, to a pneumatic actuator valve  166  through a pressurized air supply hose  168  from a solenoid-actuated pressurized air supply valve  170  mounted on the outer side of the rear wall  54  and connected to the motor controller circuit board  150  through an electric wire  172 . 
     Before turning to a specific description of the printing operation to be performed by means of the printing apparatus  10  described above with reference to FIGS. 1-3, and also with reference to FIG. 4, it is to be realized that the printing head  100  is a thermo-transfer printing head including a number of transversly spaced-apart heating elements, such as ten heating elements per mm, or even more heating elements, allowing a specific point-like area of the lower exposed surface of the printing head  70  be heated by heating a specific heating element. The printing head  100  is in itself a component well-known in the art per se and readily available from numerous manufactures, such as the Japanese manufacturer Kyocera. The printing head may be of any specific transverse dimension, such as a 1 inch, 2 inch width, or even wider. Also in a modified embodiment, a plurality of printing heads may be mounted on a common operational shaft, allowing a wider ribbon to be used for producing even wider printings in excess of 2 inch, e.g. of any arbitrary width, e.g. an integer multiple of 1 or 2 inches. 
     The printing operation is performed as follows. The control assembly  14  is pre-programmed locally or remotely through an external in/out port from a remote computer, such as a remote PC, for producing a print of a specific typographic shape and also of a specific spacing on the foil  16 . It is to be realized that the computerized controlling of the printing apparatus  10  allows the printing apparatus to produce individual prints on the foil  16 , such as prints of a consecutive numbering, including individual data or identifications of any arbitrary kind, such as a production number, a time of date, etc., without in any way changing the overall function of the printing apparatus. The foil  16  is caused to travel along its substantially horizontal path between the rollers  22  and  24 , vide FIG. 4, at a speed of travel of V 2  up to 500 mm/s, driven by the motor  34  and the drive roller  30  as discussed and described above. The motion of the foil  16  is detected by means of the motion sensor or detector  40 . Provided the printing assembly  12  is properly assembled, which is detected by means of the above-mentioned detector  180  preferably cooperating with the locking lever  60 , the control assembly  14  controls the pressure valve  50  to open for the supply of pressurized air to the solenoid-actuated valve  170 . As the control assembly  14  detects the motion of the foil  16  and on the basis of its programme establishes that a printing is to be performed, the motor  140  of the motor assembly is energized for causing the ribbon  130  to move in parallel with the foil  16  and at the same time energizes the solenoid-actuated valve  170 , causing the printing head  100  to be forced downwardly towards the counter roller  24  for pressing the ribbon  130  into contact with the surface of the foil  16 . The specific heating elements of the printing head  100  is addressed in conformity with the printing to be made for heating specific areas of the thermo-transfer ribbon  130  for causing the ink of the thermo-transfer ribbon to be heated to an elevated temperature allowing the ink to be transferred to the foil  16  as the ribbon  130  is pressed or squeezed against the foil  16 . According to the teachings of the present invention, the ribbon  130  is moved at a lower speed V 1  as compared to the speed of travel of the foil  16  on the one hand providing a perfectly readable printing and at the same time saving ribbon material as compared to a printing operation i which the thermo-transfer ribbon  130  is moved in synchronism with the foil  16 . 
     It has, surprisingly, been realized that the technique of reducing the speed of the thermo-transfer ribbon  130  relative to the foil  16  does not deteriorate the quality of the printing which is believed to be caused by the fact that the process of transferring ink from the heated areas of the thermo-transfer ribbon  130  to the foil  16  may be considered as a smearing process rather than a contact printing process, which smearing process smears the heated ink onto the foil rather than simply transferring the ink through facial contact between the thermo-transfer ribbon  130  and the foil  16 . The Speed of motion of the thermo-transfer ribbon  30  is controlled by the control assembly  14  and according to the teachings of the present invention it has been realized that the speed of motion V 1  of the thermo-transfer foil  130  may be reduced to even 20-30% of the speed of motion of the foil  16 . Also, according to the teachings of the present invention, it has surprisingly been realized that an improved printing, as compared to a printing process in which the velocities V 1  and V 2  are identical, is obtained, provided the velocity V 1  is reduced to 95-97% of the speed V 2  which is believed to be originating from the above described smearing effect. 
     It has, furthermore, surprisingly been realized that further thermal-transfer ribbon material may be saved during the printing operation through further techniques which are illustrated in FIGS. 1 a  and  1   b  and relate to side-shifting the printings during the printing operation and retraction of the thermal-transfer ribbon during the printing operation, respectively. 
     In FIG. 1 a , a printing  26   a  is to be produced on the foil  16  which printing defines a width perpendicular to the longitudinal direction of the foil  16  constituting only a fraction and in particular less than 50% of the width of the foil  16 . In numerous instances, the specific location of the printings on the foil  16  are of minor relevance, e.g. provided the printings constitute printings representing the date of packaging the material or printings identifying the packaging machine or any other identify, in which instance the printings such as the printing  26   a  illustrated in FIG. 1 a  need not to be positioned as a specific location on the foil  16  allowing that the printing  26   a  be shifted sidewise during the printing operation allowing the entire width of the thermo-transfer ribbon  130  to be utilized. As an example, assuming the width of the printing  26   a  constitutes less than 20% of the total width of the foil  16 , a first printing  26   a  is produced adjacent to one of the edges of the foil  16  whereupon the next printing is produced shifted one fifth of the width of the foil  16  sidewise and so on for the next three printings allowing a total of five prints to be produced sidewise shifted along the foil  16  still utilizing no more than a single peace of thermo-transfer ribbon material corresponding to a single thereby producing a total saving of 80% of the thermo-transfer ribbon material as compared to a conventional thermo-transfer printer or a thermo-transfer printer operated in accordance with the technique of reducing the speed of the thermo-transfer ribbon relative to the foil as discussed above with reference to FIG.  1 . Consequently, through combining the speed reduction technique described above with reference to FIG.  1  and further the sideway shifting technique illustrated in FIG. 1 a  and discussed above, an extreme saving of thermo-transfer ribbon material may be obtained provided the printings to be applied to the foil  16  constitute only a fraction of the width of the foil material and provided it is acceptable to shift the printings sidewise along the foil  16 . Assuming that e.g. 50% material is saved through the speed reduction technique described above, and assuming that a total of e.g. five prints may be produced side by side on the foil in the above described side-shifting operation, the amount of thermo-transfer ribbon material used in a printing process combining the speed reduction technique and the side-shift technique allows that only 10% of the thermo-transfer ribbon material be used in the apparatus according to the present invention as compared to a conventional non-speed reducing and non-side-shifting apparatus producing the same printings. 
     It has still further surprisingly been realized that a saving of thermo-transfer ribbon material may be obtained provided the direction or movement of the thermo-transfer ribbon be reversed during the printing operation or between any two printing operations for retraction of the thermo-transfer ribbon providing the printings to be produced define a configuration having outer contours allowing any two adjacent printings to be positioned in closely juxtaposed position. In FIG. 1 b , this technique saving thermo-transfer ribbon material through reversing the direction or motion of the thermo-transfer ribbon or retraction of the thermo-transfer ribbon after the completion of a single printing operation is illustrated. In FIG. 1 b , the printings to be produced on the foil  16  is a printing of an overall configuration of a Z having two wings protruding in opposite directions along the longitudinal direction of the foil  1 . Provided the thermo-transfer ribbon  130  is not reversed for retraction of the thermo-transfer ribbon, the leading edge of the Z printing  26   b  would be initiated at a location of the thermo-transfer ribbon  30  in spaced apart relationship from the area used for the previous printing as the new printing would be produced by the utilization of thermo-transfer ribbon material starting from the end of the material previously used for the previous printing. By the retraction of the thermo-transfer ribbon, the starting point for the new printing may be located within an area of the thermo-transfer ribbon material which was unused for the previous printing and which may still be utilized in the new printing without producing overlaps between the areas used during the two printing operations on the thermal-transfer ribbon  130 . 
     The retraction technique illustrated in FIG. 1 b  may in certain instances be combined with the side shifting technique illustrated described above with reference to FIG. 1 a  and may advantageously with or without the combination with the side-shifting technique be combined with the speed reduction technique described above with reference to FIG.  1 . 
     The above described first and presently preferred embodiment of the printing apparatus  10  according to the present invention performs its printing operation in an orientation or direction co-extensive with the direction of travel of the continuously moving foil  16  to which the printings are to be applied. The teachings of the present invention, however, may also advantageously be utilized in connection with printing apparatuses which operate in connection with intermittently moving foils and perform their printing operations along a direction of orientation transversly relative to the direction of motion of the foil. In FIGS. 5 a  and  6 , two alternative embodiments of printing assemblies are shown schematically for producing printings in a direction transversly relative to the direction of travel of the foil to which the printings are to be applied. In FIGS. 5 a  and  6 , elements or components identical to elements or components described above with reference to FIGS. 1-4 are designated the same reference numerals, whereas elements or components similar to or serving the same purpose as elements described above with reference to FIGS. 1-4 are designated the same figure, however, added the marking ′ in FIG. 5 a  and the marking ″ in FIG.  6 . 
     The printing assembly  12 ′ shown in FIG. 5 a  includes a further motor assembly including a motor  190  for causing the printing head  100  to be moved from a left-hand position transversly to a right-hand position relative to the foil  16 ′. The printing head  100  is in FIG. 5 a  shown, in its stand-by position. The motor  190  cooperates with the printing head through a drive pulley  192  mounted on the output shaft of the motor  190 , a belt  194  and a pulley  196  journalled on a supporting slide, not shown in FIG. 5 a , on which the printing head  100  is mounted, allowing the printing head to be raised and lowered as described above with reference to FIG.  2 . The thermo-transfer ribbon  130  is moved in its overall direction of motion as indicated by an arrow  200  and supplied from the ribbon supply reel  124  to the ribbon take-up reel  132 . Contrary to the above described first embodiment, the supply reel  124  is also motorized as the printing assembly includes an additional motor assembly and a further drive roller  198  corresponging to the drive roller  128 , a further belt  202  corresponding to the belt  134 , and also a further cam gear wheel  204  and a gear wheel  206  including a frictional clutch corresponding to the drive gear wheel  136  and the gear wheel  138  described above with reference to FIG.  2 . 
     The printing assembly  12 ′ is operated in three following manner. As the foil  16 ′ is kept stationary, the printing head  100  is forced into contact with the upper side of the thermo-transfer ribbon  130  and moved from its left-hand position show in FIG. 5 a  to its right-hand position and at the same time the thermo-transfer ribbon  30  is reversed and moved at a lower speed as compared to the speed of motion of the printing head  100 . After the printing operation has been performed, the printing head  100  is raised in its right-hand position and reverts to its stand-by position shown in FIG. 5 a , and the foil  16 ′ is intermittently moved one further step and at the same time the thermo-transfer foil  130  is moved in the direction indicated by the arrow  200  for collecting the used thermo-ribbon material on the reel  130  and positioning unused thermo-transfer ribbon material for the next printing operation. 
     The second embodiment of the printing apparatus illustrated in FIG. 5 a  may further advantageously be used for the above described side shifting and/or the above described retraction technique as is illustrated in FIGS. 5 b  and  5   c , respectively, allowing the further saving of thermo-transfer ribbon material. In FIG. 5 b , the side shifting technique is illustrated as three identical printings  26 ′ b  are produced side-shifted relative to one another still produced without lengthwise shifting the thermo-transfer ribbon  130 ′ along the direction of the arrow  200  or in the opposite direction as the areas of the thermo-transfer ribbon material  130 ′ used for these three side-shifted printings  26 ′ b  are positioned adjacent one another. 
     In FIG. 5 c , the retraction technique by utilizing or employing the second embodiment of the printing assembly illustrated in FIGS. 5 a  and  5   b  is disclosed as a printing  26  is produced involving the above described retraction technique in combination with the speed reduction technique described above with reference to FIG. 5 a . The two neighbouring printings  26 ′ c  are produced by utilizing mutually overlapping areas of the thermo-transfer ribbon  130 ′ by shifting or retraction of the thermo-transfer ribbon  130 ′ in the direction opposite to the arrow  200  after the completion of a first printing operation and before the initation of a second printing operation. 
     In FIG. 6, a modified third embodiment of the printing assembly illustrated in FIG. 5 a  is shown designated the reference numeral  12 ″. The third embodiment  12 ″ basically differs from the above described second embodiment  12 ″ in that the above described further motor assembly for producing a motorized supply reel  124  is eliminated as the thermo-transfer ribbon  130  is moved in one and the same direction during the printing operation, also producing the take-up on the take-up reel  132  of the thermo-transfer ribbon material without necessitating any reversal of the direction of motion of time thermo-transfer ribbon  130 . In FIG. 6, the direction of motion of the thermo-transfer foil is indicated by an arrow  208 , which direction of motion is parallel to and unidirectional relative to the direction of motion of the printing head  100  during the printing operation, providing an overall simplified structure as compared to the structure illustrated in FIG. 5 a.    
     The third embodiment of the printing assembly illustrated in FIG. 6 may also be used for utilizing the side-shifting and retraction technique described above with reference to FIGS  1   b  and  1   c , respectively, and further with reference to FIGS. 5 b  and  5   c , respectively. 
     In FIGS. 5 a  and  6 , the thermo-transfer ribbon saving aspect of the present invention is illustrated as the width, i.e. the dimension of the printings  26 ′ and  26 ″ produced on the foils  16 ′ and  16 ″ in FIGS. 5 a  and  6 , respectively, is larger than the corresponding width of the signatures produced on the thermo-transfer ribbons  130 ′ and  130 ″. Similarly, in FIG. 1, the lengthwise or longitudinal extension of the printing  26  is substantially larger than the corresponding extension of the signature produced on the thermo-transfer ribbon  130 . 
     In FIGS. 1 a  and  5   b , the thermo-transfer ribbon saving aspect of the present invention through utilizing the above described side-shifting technique is illustrated as the signatures produced on the thermo-transfer ribbons  130  and  130 ′ for producing the side-wise shifted printings are located adjacent one another covering the entire width of the thermo-transfer ribbon. Similarly, in FIGS. 1 b  and  5   c , the thermo-transfer ribbon saving aspect by utilizing the retraction technique is illustrated as the signatures produced on the thermo-transfer ribbons for producing the printings  26   c  and  26 ′ c , respectively, are fitted into one another rather than located within separate areas of the respective thermo-transfer ribbons. 
     In FIG. 7, the electronic circuitry of the printing apparatus described above with reference to FIGS. 1-4 is shown in block diagrammatic view. The electronic circuitry includes centrally a CPU-board  220  communicating with a controller board  222  and also communicating with a power supply block  224 . The power supply block receives electric power from a transformer  226  which is further connected to the mains supply, i.e. a 115 V, 60 Hz or a 230 V, 50 Hz mains supply. The electronic circuitry further includes blocks identifying the printer head  100 , the display  74 , a PCMCIA card station block  228 , a serial and parallel port block  230  and the keyboard  76 . 
     These blocks all communicate with the CPU board  220 . Similarly, the controller board  222  communicates with a block constituting the display  74 , the indicators and lamps  78  and  80 , respectively, and also the detector  180 . The controller board  222  communicates with the above described peripheral element illustrated by a block identifying the foil motion detector or encoder  40 , the solenoid  170  for actuating the printing head  100  and the control circuit  150  for controlling the motor  140 . An additional block  232  is provided for establishing communication to an external detector concerning the state of operation of the packaging machine or for controlling the shift of printing from one specific print to another alternative printing, or for modifying the printing on any arbitrary basis, such as a counter-based modification, a time-based modification, or even a modification of the printing based on an external input entity. 
     In FIGS. 8 a - 8   c , the electronic circuitry of the printing apparatus  10  is illustrated in greater detail. The circuit diagrams are believed to be self-explanatory and no detailed discussion of the electronic circuitry is presented as the diagrams solely serve the purpose of illustrating the presently preferred implementation or embodiment of the electronic circuitry of the first and presently preferred embodiment of the printing apparatus  10  according to the present invention. FIG. 8 a  illustrates the power supply block  224 , FIG. 8 b  illustrates the electronic circuitry of the controller board  22 , FIG. 8 c  illustrates the electronic circuitry of the motor driver circuitry included in the electronic circuit board  150 . 
     EXAMPLE 
     The electronic circuitry of the above described first and presently preferred embodiment of the printing apparatus according to the present invention was implemented in a prototype embodiment as follows, including the components identified in FIGS. 8 a - 8   c.    
     The transformer block  226  included a 230 V/32 V transformer. The power supply block  224  included a rectifier for rectifying 32 V AC to 46 V DC and further three switch mode regulators of the type LM2576 for producing two 24 VDC and one 5 V DC supply outputs. One of the 24 V DC outputs was amplified by a transistor for providing a 10 A output current capacity. The step motor driver circuit included in the printed circuit board  150  was supplied by the 46 V DC, the solenoid circuits were supplied by 24 V and the CPU analogical circuits were supplied by 5 V DC. The printing head was a 2 inch (51,2 mm) corner edge printing head of the type Delta V2.00 supplied from the Japanese company Kyocera. The display  74  was of the type mdls24265-lv-led04 including two times 24 characters. The PCMCIA station was ad to operate on two boards of the type sram from 256 Kbyte to 2 Mbyte. The serial and parallel ports were constituted by a parallel stard centronic parallel port, and a serial standard RS232 serial port, respectively, adapted for 2400 baud to 19200 baud operation. 
     The keyboard  74  was a softkey keyboard including a numeric keyboard also including directional arrow keys for programming the printing apparatus. The CPU board  220  was a conventional label printer printing board, however, including modified software for complying with the requirements of the printing apparatus. The CPU board was connected as described above to the blocks and elements illustrated in FIG.  7 . The controller board block  222  was configured around an Acme 89C52 chip and connected as and configured and interconnected to the various blocks and elements illustrated in FIG.  7 . The motor  140  was a Vexta PH266-E1.2, 200 steps per revolution step motor. The motor driver circuit was constituted by a step motor driver circuit implemented by PBM3960 and PBL3770 integrated circuits supplied from Ericsson Electronics and was further implemented in accordance with the electronic circuit illustrated in FIG. 8 c.    
     In FIGS. 9 a - 9   q , a first mode of the operation of the printing apparatus  10  described above with reference to FIGS. 1-4 is illustrated in an overall flow chart illustrated in FIGS. 9 a  and  9   b  and individual sub-flow charts illustrated in FIGS. 9 d - 9   q . The flow charts are believed to be self-explanatory and no detailed discussion of the flow charts is being presented, apart from the below listing of the various sub-flow charts illustrated in FIGS. 9 d - 9   q:    
     FIG. 9 c  illustrates Segment 1 of the overall flow chart of FIGS. 9 a  and  9   b , Set printer. 
     FIG. 9 d  illustrates Segment 2, Foil tension. 
     FIG. 9 e  illustrates Segment 3, Printer closed. 
     FIG. 9 f  illustrates Segment 4, Set printer stand-by. 
     FIG. 9 g  illustrated Segment 5, Stand-by. 
     FIG. 9 h  illustrates Segment 6, Printer ready continuous. 
     FIG. 9 i  illustrates Segment 7, Printer ready. 
     FIG. 9 j  illustrates Segment 8, Blink stand-by 
     FIG. 9 k  illustrates Segment 9, Relative speed adjust. 
     FIG. 9 l  illustrates Segment 10, Encoder interrupt. 
     FIG. 9 m  illustrates Segment 11, Step motor interrupt. 
     FIG. 9 n  illustrates Segment 12, Pause. 
     FIG. 9 o  illustrates Segment 13, Set printer ready. 
     FIG. 9 p  illustrates Segment 14, Set-up div. 
     FIG. 9 q  illustrates Segment 15, One relative step. 
     In FIGS. 10 a - 10   v  a second mode operation of the printing apparatus  10  described above with reference to FIGS. 1-4 is illustrated in an overall flow chart illustrated in FIGS. 10 a  and  10   b  and in individual sub-flow charts illustrated in FIGS. 10 d - 10   v . Like the above described flow charts illustrated in FIGS. 9 a - 9   q , the flow charts illustrated in FIGS. 10 a - 10   v  are believed to be self-explanatory and no detailed discussion of the flow charts is being presented, apart from the below listing of the various sub-flow charts illustrated in FIGS. 10 d - 10   v:    
     FIG. 10 c  illustrates Segment 1 of the overall flow chart of FIGS. 10 a  and  10   b , Set printer up. 
     FIG. 10 d  illustrates Segment 2, Foil tension. 
     FIG. 10 e  illustrates Segment 3, Printer closed. 
     FIG. 10 f  illustrates Segment 4, Set printer stand-by. 
     FIG. 10 g  illustrates Segment 5, Stand-by. 
     FIG. 10 h  illustrates Segment 6, Printer ready continuous. 
     FIG. 10 i  illustrates Segment 7, Printer ready. 
     FIG. 10 j  illustrates Segment 8, Blink stand-by. 
     FIG. 10 k  illustrates Segment 9, Relative speed adjust. 
     FIG. 10 l  illustrates Segment 10, Modify retraction length. 
     FIG. 10 m  illustrates Segment 11, Column mode ON-OFF. 
     FIG. 10 n  illustrates Segment 12, Encoder interrupt. 
     FIG. 10 o  illustrates Segment 13, Stepmotor interrupt. 
     FIG. 10 p  illustrates Segment 14, Pause. 
     FIG. 10 q  illustrates Segment 15, Set printer ready. 
     FIG. 10 r  illustrates Segment 16, Setup div. 
     FIG. 10 s  illustrates Segment 17, One relative step. 
     FIG. 10 t  illustrates Segment 18, Move to head down. 
     FIG. 10 u  illustrates Segment 19, Foil retraction. 
     FIG. 10 v  illustrates Segment 20, Column mode foil retraction. 
     The above flow charts illustrating the mode of operation of the printing apparatus may of course be modified in numerous ways through elimination of a specific sub-flow chart corresponding to a specific operation or through combining the sub-flow charts illustrated in FIGS. 9 a - 9   q  with one or more of the sub-flow charts illustrated in FIGS. 10 c - 10   v  or vice versa corresponding to the combination of specific operations illustrated in FIG. 9 with specific illustrations illustrated in FIG. 10 or vice versa. 
     Like the possible combination of the various routines of the modes of operation illustrated in FIGS. 9 a - 9   q  and in FIGS. 10 a - 10   v , the above described embodiments may of course also be modified through the elimination of specific elements provided a specific embodiment is to be implemented allowing only specific individual routines of the overall mode of operation illustrated in FIGS. 9 a  and  9   q  and in FIGS. 10 a  and  10   v  or alternatively, the above described embodiments may be combined through combining elements from the second or third embodiment illustrated in FIGS. 5 a - 5   c  and FIG. 6, respectively, with the first embodiment illustrated in FIGS. 1-4 or alternatively combining elements from the first embodiment illustrated in FIGS. 1-4 with the second or third embodiment illustrated in FIGS. 5 a - 5   c  and FIG. 6, respectively. Of course, the second or third embodiments illustrated in FIGS. 5 a - 5   c  and FIG. 6 may also be combined in numerous ways obvious to a person having ordinary skill in the art for deducing a specific printing apparatus complying with specific requirements as to fulfilling certain operational requirements. 
     Although the present invention has been described above with reference to different, presently preferred embodiments of the apparatus and the method of producing printings by the thermo-transfer technique as discussed above, the invention is by no means to be construed limited to the above described embodiments, as numerous modifications are deduceable by a person having ordinary skill in the art, without still deviating from the spirit and aim of the present invention as defined in the appending claims.