GB2274431A - Video printer using a thermal printing head following a curved cam surface - Google Patents

Abstract

A printer for a video is disclosed, the printer comprising a plate-like platen 1, upon which paper 9 is clamped, by means of paper holders 2. A colour ribbon 8 is disposed between the paper 9 and a printing head 3. The printing head 3 is mounted on a bracket 7 which includes a follower 6 arranged to travel on a curved guide path 5. In use, when the follower 6 is between positions B and C on the guide path surface 5, the head 3 may cause colour to be transferred from the ribbon 8 to the paper 9, in response to a printing signal. The head 3 is raised from the paper when the follower is in either of positions A or D. The follower 6 may follow path B to C or C to 13 a number of times so that, in each pass, a different colour may be transferred to the paper and a coloured image may thereby be printed. <IMAGE>

Description

A PRINTER The present nvention relates to a printer and particularly, although not exclusively, to a printer for a video.

Conventionally, a printer for a video rotates the printing paper three times while a thermal printing head sequentially sublimes three dyes of Yellow (Y), Magenta (M) and Cyan (C) laid on a three colour ribbon. The amount of the dye sublimed is controlled by the amount of heat generated in rhe thermal printing head.

A conventional printer - a video shown in Figure 1 whizz is a side elevation thereof comprises a platen drum 52 and a thermal printing head 51 positioned over the platen drum. A colour ribbon 53 having three dyes of v, M and C and a printing paper 54 are loaded between the head 51 and the platen drum 5t. The printing paper 54 is closely fixed on the platen drum 52 by a holder. n use, the paper rotates together with the platen drum, while the thermal printing head 51 generates heat to sequentially sublime the three dyes on the colour ribbon 53, so that the sublimed dyes are adsorbed on the printing paper 54.

The reason why the platen drum 52 is rotated three times is to combine the three colours in the same position on the printing paper to obtain full colour printing.

Namely, whenever the platen drum 52 makes a rotation, the three colours are sequentially printed with a slight time interval. Then, the printed paper 54 is discharged through the discharcing secticn. Thus, because the platen drum has to be rotated three times in order to complete printing, it takes considerable time to finish printing.

Furthermore, the printing positions of the three colours may be deviated from each other slightly in spite of the constant rotational speed of the platen drum 52, thereby deteriorating the quality of the printed image. Moreover, as the diameter of the cylindrical platen drum should be large enough to wind the printing paper, it may be generally impossible to decrease the volume of the printer.

According to the invention, there is provided a thermal printer for a video, the printer comprising a platen surface on which a sheet of paper to be printed upon is received, and a thermal printing head arranged to move over the platen surface so as to print an image on the paper.

The platen surface may be substantially flat. The printer may further comprise retaining means for positively retaining the sheet of paper in position on the platen surface. Said retaining means may be arranged to clamp the paper on the platen surface. Said retaining means may comprise an arm pivotally mounted, at a pivot point disposed adjacent the platen surface, and a clamping member mounted on the arm, the arrangement being such that said arm may be pivoted about said pivot point between a first position wherein said clamping member does not clamp paper on the platen surface and a second position wherein said clamping member does clamp paper on said platen surface. Said clamping member may be pivotally mounted on said arm.

Means defining a guide path is preferably provided for said thermal printing head which head is arranged to travel along said guide path. Said guide path is preferably arranged such that said thermal printing head may be guided to move substantially perpendicularly to said platen surface and arranged to move substantially parallel to said platen surface. Said guide path may be in the form of a closed loop.

The invention extends to a video printer comprising a plate-like platen, a pair of paper holders each provided on one end of said platen, a cam having a curved cam surface, a bracket having a cam follower, and a thermal printing head attached to the lower end of said bracket, said head being arranged to be moved up/down and right/left by said cam follower moving along said curved cam surface.

Said paper holder may comprise an arm rotated integrally with a shaft, and a pressing plate pivotably attached to an end of said arm through a pivot.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 2 is a side elevation of a video printer; and Figures 3A and 3B are side elevations of a part of the video printer.

Referring to Figure 2, a plate-like platen 1 has a paper holder 2 on both ends thereof. Over the platen is mounted a cam 4 having a curved cam surface 5, along which a cam follower 6 of a bracket 7 moves. The bracket 7 has a thermal printing head 3 attached to the lower end thereof. The head 3 may move up/down and right/ left during a printing operation as the cam follower 6 moves along the curved cam surface 5. The reference numerals 8 and 9 respectively indicate a colour ribbon and printing paper.

In operation, if the printing paper 9 is supplied onto the upper surface of the platen 1, the paper holders 2 are driven by a drive mechanism (not shown) to fix the paper on the platen 1. More specifically, as shown in Figure 3A, the paper is supplied onto the platen 1 through a gap formed between the platen 1 and a pressing plate 10 of each respective paper holder 2 which plate 10 is lifted initially from the platen 1 to allow the paper to enter the gap. In this position, if a sensor (not shown) senses the paper supplied onto the platen 1, an arm 12 is rotated about its pivot 11 to lower the pressing plate 10 to fix the paper 9 onto the platen 1. The pressing plate 10 is freely pivoted about a pivot 15, on the arm 12, so that the underside 10' of the plate 10 may be abutted in parallel to the platen 1, so as to stably fix the paper onto the platen, as seen in Figure 3B.

Thereafter, upon receiving a printing signal from an internal circuit (not shown), the cam follower 6 of the bracket 7 moves along the curved cam surface 5a from the initial position A, where the thermal printing head is separated from the platen 1, to the position B and, therefore, the thermal printing head 3 moves downwardly to press the paper 9 and the colour ribbon 8 on the platen 1.

Subsequently, as the cam follower 6 moves along the cam surface Sb, the thermal printing head 3 moves linearly, to print the Y colour onto the paper, until the cam follower 6 arrives at position C. If the cam follower 6 further moves to the position D, the thermal printing head 3 rises and is thereby separated from the paper 9.

Then, the ribbon 8 is wound around a reel 20 to replace the initial Y colour part with the M colour part of the paper 9.

Upon receiving the signal of the M colour part and with the ribbon 8 suitably positioned over the paper 9, the cam follower 6 moves along the cam surface 5e from the position D to the position C and the printing head 3 is again lowered to press the ribbon 8 and the paper 9.

Then, the head moves along the cam surface 5b from the position C to the position B whilst generating heat, and, thus, uniformly printing the M colour.

Upon completing the printing of the M colour, the cam follower 6 moves upwardly along the cam surface 5a to the position A and the thermal printing head 3 again rises and is separated from the paper 9. Thereafter, the colour ribbon 8 is wound around the reel 20 to replace the M colour part with the C colour part for the paper 9. The subsequent operational steps to print the C colour are the same as when printing the Y colour, as described above.

Thus, the three colours Y, M and C are harmoniously printed on the paper, so as to complete one printing operation. Finally, the thermal printing head moves linearly from the position D to the position A so as to prepare for the next printing operation.

As apparent from the above description, the printer comprises a plate-like platen that may make it possible to reduce the overall height of a printer. Moreover, as the thermal printing head moves back and forth so as to print, the time required for printing may be reduced.

Furthermore, as slip of the paper on the platen may be substantially prevented, a clear printing image may result.

The foregoing description shows only a preferred embodiment of the present invention. Various modifications are apparent to those skilled in the art without departing from the scope of the present invention which is only limited by the appended claims. Therefore, the embodiment shown and described is only illustrative, not restrictive.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (4)

1. A video printer comprising a plate-like platen, a pair of paper holders each provided on one end of said platen, a cam having a curved cam surface, a bracket having a cam follower, and a thermal printing head attached to the lower end of said bracket, said head being arranged to be moved up/down and right/left by said cam follower moving along said curved cam surface.

2. A video printer as claimed in Claim 1, characterised in that said paper holder comprises an arm rotated integrally with a shaft, and a pressing plate pivotally attached to an end of said arm through a pivot.

3. A video printed as claimed in Claim 1, wherein a said paper holder comprises a pivotally mounted arm and a pressing plate pivotally attached to said arm.

4. A video printer substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying diagrammatic drawings.