EP0109863A2 — A thermal transfer colour sheet printer

Claim 1

Independent Claim 336 words

A thermal transfer colour printer for printing colour images on separate individual sheets (24) of a recording medium comprising: feed means (46) for feeding separate sheets of the recording medium one by one; a reversible platen roller (74) to transport a single sheet of recording medium received from the feed means; a multicoloured ink ribbon (108) which is supported to move across the platen roller (74) with one face of said ink ribbon in heat transfer relationship with the sheet (24) of recording medium, and which has a plurality of colour segments successively arranged along its length; a thermal printhead (116) having thermal elements (120) adapted to be selectively energised by colour component electrical signal representing the colour image to be printed on the sheet of recording medium, the printhead being positioned with its thermal elements facing the surface of the platen roller (74) in heat transfer relationship with the multicoloured ink ribbon; ink ribbon drive means (176) for transporting the multicoloured ink ribbon (108) in a first direction; and electrical circuit means connected to the thermal printhead for supplying the colour component electrical signal to the thermal elements while the sheet of recording medium is transported in the first direction; characterised in that retention means (82, 84) are located adjacent the platen roller (74) for retaining a sheet (24) in contact with the surface of the platen roller and for guiding the sheet over the surface of the platen roller when driven by platen roller drive means (76), and in that the platen roller drive means (76) are arranged both to drive the platen roller (74) to transport a sheet (24) in the first direction, without disengaging the retention means (82, 84) from the rear end portion of the sheet, at substantially the same rate as the ink ribbon (108) is driven by the ink ribbon drive means (176), and to drive the platen roller (74) in the reverse direction without disengaging the retention means (82, 84) from the front end portion of the sheet.

Claim 2

Dependent Claim 336 words

A thermal transfer colour printer for printing colour images on separate individual sheets (24) of a recording medium comprising: feed means (46) for feeding separate sheets of the recording medium one by one; a reversible platen roller (74) to transport a single sheet of recording medium received from the feed means; a multicoloured ink ribbon (108) which is supported to move across the platen roller (74) with one face of said ink ribbon in heat transfer relationship with the sheet (24) of recording medium, and which has a plurality of colour segments successively arranged along its length; a thermal printhead (116) having thermal elements (120) adapted to be selectively energised by colour component electrical signal representing the colour image to be printed on the sheet of recording medium, the printhead being positioned with its thermal elements facing the surface of the platen roller (74) in heat transfer relationship with the multicoloured ink ribbon; ink ribbon drive means (176) for transporting the multicoloured ink ribbon (108) in a first direction; and electrical circuit means connected to the thermal printhead for supplying the colour component electrical signal to the thermal elements while the sheet of recording medium is transported in the first direction; characterised in that retention means (82, 84) are located adjacent the platen roller (74) for retaining a sheet (24) in contact with the surface of the platen roller and for guiding the sheet over the surface of the platen roller when driven by platen roller drive means (76), and in that the platen roller drive means (76) are arranged both to drive the platen roller (74) to transport a sheet (24) in the first direction, without disengaging the retention means (82, 84) from the rear end portion of the sheet, at substantially the same rate as the ink ribbon (108) is driven by the ink ribbon drive means (176), and to drive the platen roller (74) in the reverse direction without disengaging the retention means (82, 84) from the front end portion of the sheet.

Claim 3

Dependent Claim 103 words

A thermal transfer colour printer according to claim 1, wherein the thermal printhead (116) is selectively movable up and down so that, in the up state, it presses the ink ribbon (108) and the sheet (24) of recording medium onto the surface of the reversible platen roller (74) for thermally transferring coloured ink from the ink ribbon onto the sheet of recording medium when the thermal elements (120) are energised and, in the down state the thermal printhead (116) provides a guide path for the sheet (24) of recording medium between the ink ribbon (106) and the surface of the platen roller (74).

Claim 4

Dependent Claim 43 words

A thermal transfer colour printer according to claim 1, wherein the ribbon drive means (176) is arranged to apply tension to the ribbon (108) so that the ink ribbon guides the sheet of recording medium along the surface of the platen roller (74).

Claim 5

Dependent Claim 65 words

A thermal transfer colour printer according to claim 3, wherein the ribbon drive means comprises a rotatable supply reel (106); brake means (172) adjacent the rotatable supply reel for providing a braking force against the rotation of the supply reel; a rotatable take-up reel (138); and a take-up motor (176) for driving the rotatable take-up reel to transport the ink ribbon in the first direction.

Claim 6

Dependent Claim 100 words

A thermal transfer colour printer according to any one of the preceding claims, wherein the retention means comprise first and second pinch rollers (82, 84) each of which is rotatably supported adjacent the platen roller (74) on opposite sides thereof, and pinch roller shift means (250) for shifting the first pinch roller (82) towards the platen roller (74) during a first loading period to retain the sheet engaged with the surface of the platen roller to cause the platen roller to feed the sheet to the second pinch roller (74),,and away from the platen roller in a second loading period.

Claim 7

Dependent Claim 65 words

A thermal transfer colour printer according to claim 5, wherein slack removing means (236) are positioned to apply a force to the sheet between the feed means (46) and the platen roller (74) during the second loading period to remove slack from the sheet, the pinch roller shifting means (250) then shifting the sheet of recording medium back towards the surface of the platen roller.

Claim 8

Dependent Claim 67 words

A thermal transfer colour printer according to claim 6, wherein the feed means comprise supply means (22, 46) for storing sheets of the recording medium and supplying the sheets one at a time, and guide means (234, 236) for guiding each sheet from the supply means to the reversible platen roller so that it is gripped between the platen roller (74) and the first pinch roller (82).

Claim 9

Dependent Claim 126 words

A thermal transfer colour printer according to claim 7, wherein there are further guide means comprising second guide means (260) for guiding the sheet of recording medium discharged from the platen roller (74) and the second pinch roller (84) in a substantially vertical direction; third guide means (96) for temporarily receiving the sheet of recording medium from the second guide means (2 6 0); fourth guide means (242) intersecting the first guide means (234, 236) for temporarily receiving the sheet transported from the platen roller (74) and the first pinch roller (82) when the sheet is transported in the reverse direction; and flap means (236) positioned at the intersection of the first and fourth guide means for selectively guiding the sheet to the fourth guide means.

Claim 10

Dependent Claim 116 words

A thermal transfer colour printer according to claim 8, wherein first rotatable drive rollers (232) are located at the entrance of the first guide means (234, 236) to transport the sheet along the fist guide means; second rotatable drive rollers (264) are located at the exit of the second guide means (260) to transport the sheet along the second and third guide means; and roller drive means (268, .270) are connected to drive the first and second rotatable drive rollers (232, 264) in synchronous relationship with the reversible platen roller (74), the roller drive means driving the first and second rotatable rollers in opposite direction to transport the sheet in the first and second directions, respectively.

Claim 11

Dependent Claim 40 words

A thermal transfer colour printer according to claim 8, wherein the flap means (236) constitute the slack removing means, being arranged to push the sheet at a point intermediate the first drive rollers (232) and the first pinch roller (82).

Claim 12

Dependent Claim 27 words

A thermal transfer colour printer according to claim 10, wherein the flap means (236) pushes against the sheet opposite the opening of the fourth guide means (242).

Claim 13

Dependent Claim 28 words

A thermal transfer colour printer according to any one of the preceding claims, wherein the length of the colour segments defines the maximum printing zone of the printer.

Claim 14

Dependent Claim 24 words

A thermal transfer colour printer according to any one of the preceding claims, wherein the colour segments comprise the colours yellow, magenta and cyan.

Claim 15

Dependent Claim 23 words

A thermal transfer colour printer according to any one of the preceding claims, wherein the recording radium is a sheet of plain paper.

Claim 16

Dependent Claim 24 words

A thermal transfer colour printer according to any one of claims 1 to 13, wherein the recording medium is a sheet of plastic material.

Claim 17

Independent Claim 301 words

A method of thermal transfer colour printing of colour images on separate individual sheets of a recording medium comprising the steps of: storing a plurality of individual separate sheets of a recording medium in a storage cassette; removing one sheet of the recording medium at a time from the storage cassette; transporting the sheet of recording medium in a first direction over a reversible platen roller at a first predetermined rate; removing slack from the sheet of recording medium shortly after it is first engaged by said reversible platen roller; transporting a multicoloured ink ribbon adjacent the sheet of recording medium in the first direction and at said first predetermined rate, the multicoloured ink ribbon having a plurality of different colour segments successively arranged along its length; pressing a thermal printhead against the platen roller to press said multicoloured ink ribbon and the sheet of recording paper together while they are moving in the first direction at said predetermined rate, said thermal printhead having a linear array of thermal elements transverse to the first direction; energising the linear array of thermal elements with colour component signals corresponding to the particular colour segment of said multicoloured ink ribbon currently pressed against the sheet of recording medium to thermally and selectively transfer the colour of the particular colour segment onto a sheet; disengaging the thermal printhead from the platen rcller; transporting the sheet of recording medium a predetermined distance in a second direction opposite said first direction at a second predetermined rate; repeating the above steps of transporting, pressing, energising and disengaging until all colours of the multocoloured ink ribbon have been thermally and selectively transferred onto the sheet to form a colour image in response to all colour component signals; and discharging the sheet of recording medium with the printed colour image.

Claim 18

Independent Claim 301 words

A method of thermal transfer colour printing of colour images on separate individual sheets of a recording medium comprising the steps of: storing a plurality of individual separate sheets of a recording medium in a storage cassette; removing one sheet of the recording medium at a time from the storage cassette; transporting the sheet of recording medium in a first direction over a reversible platen roller at a first predetermined rate; removing slack from the sheet of recording medium shortly after it is first engaged by said reversible platen roller; transporting a multicoloured ink ribbon adjacent the sheet of recording medium in the first direction and at said first predetermined rate, the multicoloured ink ribbon having a plurality of different colour segments successively arranged along its length; pressing a thermal printhead against the platen roller to press said multicoloured ink ribbon and the sheet of recording paper together while they are moving in the first direction at said predetermined rate, said thermal printhead having a linear array of thermal elements transverse to the first direction; energising the linear array of thermal elements with colour component signals corresponding to the particular colour segment of said multicoloured ink ribbon currently pressed against the sheet of recording medium to thermally and selectively transfer the colour of the particular colour segment onto a sheet; disengaging the thermal printhead from the platen rcller; transporting the sheet of recording medium a predetermined distance in a second direction opposite said first direction at a second predetermined rate; repeating the above steps of transporting, pressing, energising and disengaging until all colours of the multocoloured ink ribbon have been thermally and selectively transferred onto the sheet to form a colour image in response to all colour component signals; and discharging the sheet of recording medium with the printed colour image.

Claim 19

Dependent Claim 18 words

A method according to claim 16, wherein the second predetermined rate is greater than the first predetermined rate.

Claim 20

Dependent Claim 21 words

A method according to claim 16 or claim 17, wherein the sheet of recording medium is a sheet of plain paper.

Claim 21

Independent Claim 55 words

A method according to any one of claims 16 to 18, wherein the sheet is continuously gripped between the platen roller and at least one pinch roller during the steps of transporting, removing slack, pressing, energising and disengaging in order to prevent distortion in the colour image when those steps are repeated for all colours.

Claim 22

Dependent Claim 39 words

A method according to any one of claim 16 to 19, wherein tension is applied to the multicoloured ink ribbon to enable that ribbon to guide the sheet along the surface of the platen roller in said first direction.

Claim 23

Dependent Claim 52 words

A method according to claim 20, wherein the movement of the ink ribbon in the first direction is adjusted in response to variations in the tension along the ink ribbon in order to make the rate of movement of the sheet of iecording medium susiantially constant despite variations in ink ribbon tension.

A thermal transfer colour sheet printer

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