Colour video printer

Abstract: A colour video printer for printing on both sides of a sheet printing paper, includes a plurality of guide rollers (31) positioned about the circumference of a platen roller (30) and an ink ribbon supplying unit (50). A thermal recording head (15) is selectively contacted with or separated from the platen roller (30) by the operation of a cam (10), and a slide (20) is operated by the cam (10). Cam grooves (21,22) are formed in the slide (20) so as to operate a paper ejecting guide (40) and a refeed paper roller (45).

Description: The present invention relates to a colour video printer. Video printers are used to produce hard copies of video images. In a known form of video printer, a full colour image is formed by sequentially sublimating three pigments onto a sheet of paper. The pigments are respectively the three primary colours. That is yellow (Y), cyan (C) and magenta (M). Referring to Figure 1, which shows this type of colour video printer, a sheet of thermal printing paper 5 is fed by the rotation of a paper feed roller 11, and then, positioned on the circumference of a drum 4, located below an ink ribbon 6. The ink ribbon 6 has sequential bands of sublimable dyestuffs of the three primary colours: yellow (Y), magenta (M) and cyan (C). Thereafter, the thermal printing paper 5 is held close to the drum 4, together with the ink ribbon 6, by the pressure of a thermal recording head 3 located above the ink ribbon 6. As the drum 4 rotates, the thermal printing paper 5 and the ink ribbon 6 come into contact with one another as the drum 4 rotates; the thermal printing paper 5 proceeding at the same speed as the drum 4. If the thermal recording head 3 generates heat, while the drum 4 is revolving, the dyestuffs of the ink ribbon 6 are sublimated according to the degree of heating of the thermal recording head 3 and adhere to the thermal printing paper 5. Thus, secondary colours are formed on the thermal printing paper by applying different ratios of the primary colours to the thermal printing paper. When the printing is finished, the thermal printing paper 5 is separated from the drum 4 and fed out of the printing machine by the rotation of a paper ejecting roller 12. In this case, the thermal printing paper 5 used for printing purposes contains, as shown in Figure 2, a pulp layer 74, a polyethylene layer 76 and an ink absorptive layer 78 and is only printed on one side. Thus, a colour video printer is known which comprises a printing head; a platen roller for conveying a printing sheet past the printing head during a plurality of colour printing cycles in each of which the sheet is printed with a different colour so as to build up a multi-colour image; and guide means movable to selectively allow retention of the printing sheet on the platen roller or remove it therefrom. However, in such a conventional colour video printer, since the printing paper is only printed on one side and the platen drum must rotate four times, once for printing each primary colour and a further time in order to eject the printing paper, printing is slow. It is an aim of the present invention to overcome these disadvantages. According to the present invention, there is provided a colour video printer as defined above, characterised by control means arranged to drive the guide means such that the guide means moves into its sheet removing position during the final colour printing cycle so as to remove the sheet at the end of that cycle. Preferably, the printer includes paper refeeding means movable between an operative position and an inoperative position by the control means, wherein a sheet of printing paper, printed on one side, is removed from the platen roller by the guide means and refed to the platen roller for printing on the other side thereof by the refeed means under the control of the control means. Preferably, the printing head is movable between an operative position and an inoperative position by means of the control means. Preferably, the control means comprises cam means. In the preferred embodiment, a plurality of guide rollers are positioned on the circumference of the platen roller. Preferably, the printer includes a paper feed unit, a paper ejecting unit, an ink ribbon supplying unit, a slider for operating a paper ejecting guide and a re-feed paper roller. Conveniently, the slider, re-feed paper roller and printing head are driven by a cam having a first and second cam groove formed thereon. Preferably, the slider controls the paper ejecting guide to eject printing paper while completing the printing of cyan (C) colour. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram of a typical colour video printer; Figure 2 is an enlarged sectional view of printing paper suitable for printing purposes; Figure 3 is a schematic block diagram of a colour video printer according to the present invention; Figures 4A to 4E are schematic block diagrams showing a printing process according to the present invention; and Figure 5 is an enlarged sectional view of printing paper according to the present invention. Referring to Figure 3, a plurality of guide rollers 31 are provided about the circumference of a platen roller 30. There is also provided an ink ribbon supplying unit 50. A thermal recording head 15 is arranged to be selectively brought into contact with or separated from the platen roller 30 by the operation of a cam 10. A slider 20 is also operated by the cam 10. Cam grooves 21 and 22 are formed in the slider 20 so as to operate a paper ejecting guide 40 and a refeed paper roller 45 as the cam reciprocates. A sheet of printing paper 70 supplied from a feed paper unit is guided to a feed paper guide 72 by a feed paper roller 71 and arrives at the platen roller 30. Then the printing paper 70 is brought close to the platen roller 30 by a holder (not shown) and is moved at the same speed as the platen roller 30 to an initial position for printing. Thereafter, if the cam 10 rotates, a thermal recording head driving lever 11 operated by a first cam groove 10a rotates about a pivot 12. Then the thermal recording head 15 moves close to the platen roller 30 together with a ribbon 51 and simultaneously a slider driving lever 16 is rotated about a pivot 17 by a second cam groove 10b. Hence, the slider 20 is shifted to the left (as viewed in Figure 3). At this time, the paper ejecting guide 40 revolves clockwise round an axis 41 because a bracket 23, hanging from the cam groove 21 moves up. Moreover, the refeed paper roller 45 does not operate because one end of a bracket 46, hanging from the cam groove 22, is located on the flat bottom of the cam groove 22 (Figure 4A). Thereafter, as the cam 10 operates, the thermal recording head 15 does not operate and the slider driving lever 16 is driven by the cam groove 10b, while the thermal recording head 15 is in contact with the platen roller 30, since the cam groove 10a is part of a circle concentric with the cam 10 as shown in Figure 4B. Then the slider 20 is shifted to the left and the bracket 23 moves downwards. Consequently the paper ejecting guide 40 rotates anticlockwise so as to pass the printing paper 70. Meanwhile, the refeed paper roller 45 does not operate because one end of the bracket 46 is still located at the flat bottom of the cam groove 22. In this case, the platen roller 30 rotates and heat is generated by the thermal recording head 15, thereby printing on the printing paper 70 in yellow (Y) (Figure 4B). Under such a state, if the platen roller 30 rotates once to complete printing in yellow (Y), the cam 10 rotates backwards. Then the slider 20 is shifted to its initial position and simultaneously the thermal recording head 15 is lifted up. Further, the ribbon 51 moves to a position for printing in magenta (M). Next, the cam 10 rotates, to maintain the state shown in Figure 4B, and then the printing paper 70 is printed in magenta (M). When the printing in magenta (M) has finished, the cam 10 rotates backwards, thereby lifting up the thermal recording head 15. Moreover, the ribbon 51 is shifted to the position for printing in cyan (C). As described above, the process for printing in magenta (M) is the same as that for printing in yellow (Y). In order to print in cyan (C), if the cam 10 operates and driven shafts 13 and 14, which are respectively inserted to the cam grooves 10a and 10b, move to ends of the cam grooves 10a and 10b, the thermal recording head driving lever 11 does not rotate about the shaft 12 by means of the driven shaft moving on the concentric circle of the cam groove 10a, and the thermal recording head 15 remains in close contact with the platen roller 30. On the other hand, since the driven shaft 14 moving along the cam groove 10b moves further from the centre of the cam 10, the slider driving lever 16 pivots about the pivot 17 and the slider 20 is shifted to the leftmost extent of its travel. Consequently, the bracket 23 moves up and the paper ejecting guide 40 revolves clockwise about the pivot 41 and the end thereof is moved close to the platen roller 30. Further, since the bracket 46 is also shifted to the upper direction, the refeed paper roller 45 rotates anticlockwise round the pivot 47 and is separated from a paper feed belt 48 (Figure 4C). At this time, if the platen roller 30 is driven, printing in cyan (C) is ended and simultaneously the lead edge of the printing paper 70 is guided to an upper surface 40a of the paper ejecting guide 40. Then the printing paper 70 is moved through a paper ejecting roller 27. When the trailing edge of the printing paper 70 is separated from the thermal recording head 15, the cam 10 rotates backwards to return to its initial position. Then the thermal recording head 15 is separated from the platen roller 30 and simultaneously the bracket 46 moves downwards. Thus, the paper refeed roller 45 moves close to the paper feed belt 48 and the printing paper 70 is ejected (Figure 4D). When printing is on only one side of the printing paper 70, the paper feed belt 48 is driven anticlockwise to eject the printing paper 70. However, when printing is on both sides of the printing paper 70, the refeed paper roller 45 and the paper feed belt 48 rotate backwards before the trailing edge of the printing paper 70 is separated from the refeed paper roller 45 by sensing the trailing edge of the printing paper 70, and then, the printing paper 70 is guided to a guide 75 so as to move to the platen roller 30. At this time, since the printed side of the printing paper 70 comes into contact with the platen roller 30, the other side of the printing paper 70 can be printed on (Figure 4E). As indicated in Figure 5, the printing paper 70 comprises polyethylene layers 76a and 76b and dyestuffs absorptive layers 78a and 78b symmetrically formed on the base pulp layer 74. Therefore, it is possible to print on both sides of the printing paper 70. As is apparent from the aforementioned description, the illustrated embodiment of the present invention may increase printing speed by ejecting the printing paper while printing in cyan (C) is being completed. Also, the printing paper is used more efficiently as it is printed on both sides.

Claims: A colour video printer, comprising a printing head (15), a platen roller (30) for conveying a printing sheet (70) past the printing head (15) during a plurality of colour printing cycles in each of which the sheet (70) is printed with a different colour so as to build up a multi-colour image, and guide means (40) movable to selectively allow retention of the printing sheet (70) on the platen roller (30) or remove it therefrom, characterised by control means (10,20) arranged to drive the guide means (40) such that the guide means (40) moves into its sheet removing position during the final colour printing cycle so as to remove the sheet (70) at the end of that cycle. A colour video printer according to claim 1, including paper refeeding means (45) movable between an operative position and an inoperative position by the control means (10,20), wherein a sheet of printing paper (70), printed on one side, is removed from the platen roller (30) by the guide means (40) and refed to the platen roller (30) for printing on the other side thereof by the refeed means (45) under the control of the control means (10,20). A colour video printer according to claim 1 or 2, wherein the printing head (15) is movable between an operative position and an inoperative position by means of the control means (10). A colour video printer according to claim 1, 2 or 3, wherein the control means (10,20) comprises cam means (10,20). A colour video printer according to any preceding claim wherein a plurality of guide rollers (31) are positioned on the circumference of the platen roller (30). A colour video printer according to any preceding claim further comprising a paper feed unit (71,72), a paper ejecting unit (27,45,48), an ink ribbon supplying unit (50), a slider (20) for operating a paper ejecting guide (40) and a re-feed paper roller (45). A colour video printer according to claim 6 wherein the slider (20), re-feed paper roller (45) and printing head (15) are driven by a cam (10). A colour video printer according to claim 7 wherein a first cam groove (10a) and a second cam groove (10b) are formed on said cam (10). A colour video printer according to any of claims 6-8 wherein said slider (20) controls the paper ejecting guide (40) to eject printing paper (70) while completing the printing of cyan (C) colour. A colour video printer according to any preceding claim loaded with printing paper, the printing paper comprising: a pulp base layer (74); polyethylene layers (76a,76b) on each face of the base layer (74); and ink absorptive layers (78a,78b) on each polyethylene layer (76a,76b). A colour video printer according to claim 10 wherein the polyethylene layers (76a,76b) and ink absorptive layers are symetrically formed on the pulp base layer (74) of the printing paper.

Inventors: CHANG KI-SON, KANG DONG-HWAN, PARK MOON-BAE, CHANG, KI-SON, KANG, DONG-HWAN, PARK, MOON-BAE
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO. LTD.
Application year: 1993
Main classification: B41J13
IPC codes: B41J2, B41M5, B41J13, B41J3