WO1999064245A1

WO1999064245A1 - Thermal transfer printers

Info

Publication number: WO1999064245A1
Application number: PCT/GB1999/001817
Authority: WO
Inventors: Daoning Su; Peter Butcher
Original assignee: Imperial Chemical Industries Plc
Priority date: 1998-06-10
Filing date: 1999-06-09
Publication date: 1999-12-16
Also published as: GB9812461D0

Abstract

A thermal transfer printer has a housing (4) accommodating a paper tray (26) and a print head (12) which undergoes a reciprocating movement above the paper tray (26) to execute print strokes and return strokes in alternate sequence. During a print stroke, the print head (12) presses a thermal transfer ribbon (13) against the uppermost sheet (30) of paper in the tray (26). This avoids the need for a conventional paper transport mechanism, thereby rendering the printer very compact and suitable for fitting in a confined space, such as the disc drive bay of a personal computer.

Description

TITLE: THERMAL TRANSFER PRINTERS

This invention relates to thermal transfer printers and was developed to provide a compact printer suitable for fitting in a confined space, such as the disc drive bay of a personal computer.

According to one aspect of the invention a thermal transfer printer comprises support means for supporting a stack of sheets of paper, a thermal transfer print head and receiving means for receiving a thermal transfer dye sheet so that the dye sheet extends between the head and an exposed sheet of paper in the stack, the print head being capable of selectively transferring dye from the dye sheet to the exposed sheet of paper in the stack, and the print head being capable of a traversing movement with respect to the support means for completion of printing of the exposed sheet of paper of the stack. Hence, in the invention printing takes place on the exposed sheet of paper, any remaining sheets of paper forming a backing for the printing operation. This avoids the need for a conventional paper transport mechanism and is a major factor in the achievement of a compact printer.

Preferably, the print head is mounted on a carriage guided for reciprocating movement in an alternating sequence of operative printing strokes and return strokes. The carriage is conveniently reciprocabb ahow; the support means so that the exposed sheet is the uppermost sheet in the siac .

The head may be mounted on the carriage so as to be movable between a lowered position, which the head occupies on each operative stroke, and a raised position which the head occupies on each return stroke. The receiving means, which is preferably also mounted on the carriage, may be adapted to receive a cartridge containing a dye sheet ribbon extending between supply and take-up spools arranged such that the peel angle and peel force between the ribbon and the uppermost sheet are sufficient to ensure reliable separation.

The support means may be in the form of a tray with a movable base panel biased to urge the stack of paper so that the sheet which is for the time being uppermost occupies a predetermined position, so that the plane in which printing takes place remains constant in the printer as the stack of sheets is depleted. This biasing effect may be provided by springs biasing angled faces which engage rods guided for limited vertical movement in slots and engaging the underside of the base panel.

The thermal transfer printer according to the invention was devised to enable the printer to be accommodated in the disc drive bay of a personal computer. Hence, according to another aspect of the invention a thermal transfer printer has a housing sufficiently compact to enable the printer to be accommodated in a disc bay of a personal computer, the housing supporting a paper tray for accommodating a stack of sheets of paper to be printed so that the length and width of the paper define two mutually orthogonal axes, a print head positioned above the paper tray and movable between a lowered operative position, in which the head presses a ribbon against the uppermost sheet of paper in the tray, and a raised inoperative position in which the print head is clear of the paper in the tray, the print head having an elongated line of print head elements which extend parallel to one of the two mutually orthogonal axes and the print head being movable parallel to the other of the two mutually orthogonal axes to execute print strokes and return strokes in alternate sequence, in each print stroke the print head being in the lowered operative position and completing printing of the uppermost sheet and in each return stroke the print head being in the raised inoperative position. The rest position of the carriage, which the carriage occupies between printing individual sheets, may be at an intermediate position along the return stroke.

The printer housing may be formed, eg with guide rails, to enable the thermal transfer printer to be wholly or partially slid out of a slot in the personal computer, for example for replacement of a ribbon cartridge.

The compactness of the printer according to the invention renders it suitable for use in other situations, such as:

Integrated digital camera/printer

TV/printer

Integrated into an interactive toy or games console.

Integrated into an instrument panel of eg aircraft or car for printing out maps.

Integrated into medical diagnostic devices such as ultrasound or endoscopy.

In seat backs of planes, trains, coaches or people movers with or without a small digital camera.

In certain of these applications the printer could be battery powered.

A thermal transfer printer according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a fragmentary isometric view of the printer fitted in the disc bay of a computer, the printer being illustrated in a withdrawn position,

Figure 2 is a plan view of the printer,

Figure 3 is a diagrammatic longitudinal sectional view of the printer with a paper tray in a retracted position,

Figure 4 is a view corresponding to that of Figure 3 but with the paper tray in a partially extended position,

Figure 5 is a transverse sectional view through the paper tray, and

Figure 6 illustrates a possible modification.

Referring to Figure 1, the printer 1 is mounted in the slot 2 defined by a disc bay in a personal computer, part of the casing of which is illustrated at 3. The printer has a housing 4 the sides of which have horizontal rails 5 for slidably moving the printer 1 between the extended position shown in Figure 1 and an operative retracted position in which a front panel 6 of the printer housing 1 is substantially flush with the front panel 7 of the computer housing. The front panel 7 of the printer has a button (not shown) depressible to release the printer from its operative position, to enable the printer to be withdrawn.

Between the front and back of the printer extend two spaced horizontal guide rods 9 which guide longitudinal sliding movement of a carriage 10 carrying a thermal transfer print head 12 and a removable cartridge having a thermal transfer ribbon 13 extending between a supply spool 14 and a take-up spool 15. The head 12 has a line of heating elements arranged on the edge of a substrate of the head, the elements being aligned in a transverse direction, ie parallel to the width dimension of the printer.

The carriage 10 is driven by a lead screw 16 (Figure 2) which extends horizontally between the front and back of the printer housing between the two guide rods 9. The lead screw 16 is driven by an electric stepping motor 17 through the intermediary of a drive belt 8, both accommodated within the printer housing.

The carriage 10 is driven by the motor 17 in a reciprocating motion, undertaking an operative print stroke as the carriage moves from right to left as viewed in Figures 3 and 4 and a return stroke as the carriage moves from left to right as viewed in Figures 3 and 4. During a print stroke, the print head 12 is in a lowered operative position (illustrated in Figures 3 and 4) and on the return stroke the print head is moved to a raised retracted position. To achieve this change over, the carriage 10 has head movement wedge mechanisms 18, 19 at its respective ends, the mechanism 18 engaging a head lift stop 20 at the rear end of the printer and a head lower stop 22 at the front end of the printer. During a print stroke, the take-up spool 15 is driven, through a clutch and one-way ratchet drive, by a pinion 23 engaging a longitudinally extending rack 24. Rotation of the supply spool 14 occurs against light frictional resistance to prevent unwanted unwinding of the ribbon from the spool 14. The lower part of the printer housing is occupied by a paper tray 26 which has an underside panel 27, and two side walls 28 from which extend inturned flanges 29 defining between them a space to enable access to be gained to the uppermost sheet 30 of a stack 32 of paper accommodated in the tray. The tray has a movable base panel 33 beneath which extend two transverse rods 34 guided for movement in vertical slots 35 in the side walls 28. The extremities of the rods 34 extend beyond the side walls 28 and the projecting ends 36 are urged upwardly by the inclined faces of horizontally movable wedges 37 biased by respective compression springs 38. There are four such wedges 37 and springs 38, each spring 38 acting between a fixed abutment 39 in the housing and a facing edge of the corresponding movable wedge 37.

At its front end, the paper tray 26 has a projecting handle 40 which enables the tray to be moved between its fully inserted position shown in Figure 3 and an extended position in which the tray 26 is pulled forwardly through a slot 42 in the front panel 6 of the housing 4. Figure 4 shows a partially extended position of the tray, the fully extended position being defined by the engagement of the rearmost rod 34 with the foremost pair of spring abutments 39. In this extended position, the supply of paper in the tray can be replenished.

As previously explained, the whole printer can be moved to the extended position illustrated in Figure 1, this enabling the ribbon cartridge to be replaced by a sidewards unloading/loading movement. When the printer housing is pushed back into the computer a power and signal connection 43 on the rear of the printer housing makes electrical connection with a cooperating socket on the back of the bay accommodating the printer, to provide electrical power and electrical control signals to an electronics board 41 (Figure 2) of the printer.

Between the printing of individual sheets of paper, the carriage 10 occupies the rest position illustrated in Figures 3 and 4, but with the print head 12 in its raised position. A printing operation then takes place: the carriage 10 completes its return stroke with the print head in its raised position until the head lower mechanism 19 engages the stop 22 at the front of the housing to cause the head to be lowered to the operative position shown in Figures 3 and 4 in which the ribbon 13 is pressed between the print head 12 and the uppermost sheet of paper. With the panel 33 urging the paper stack upwardly so that the uppermost sheet 30 of paper is urged against the undersides of the spaced flanges 29, the carriage undergoes an operative print stroke, moving from the front to the back of the printer so as to print the uppermost sheet 30 of paper which remains stationary during printing. When the carriage 10 reaches the rear of the housing, the lift mechanism 18 engages the stop 20 to cause the head 12 to be moved to its raised position, upon which the head executes the first part of the return stroke and moves to its rest position ready for the next printing operation. The uppermost sheet of paper, now printed on its upper surface, is ejected through the slot 42 at the front of the printer, by means of an eject roller 44 or manually. As the individual sheets are printed and removed from the paper tray, the diminishing stack of paper continues to be urged upwardly by the base panel 33 so that the uppermost sheet 30 of paper always occupies the same physical position in the print tray, this therefore always being the plane of printing, regardless of the number of sheets of paper remaining in the tray.

The described printer is for printing sheets of paper of A6 size, the tray having a capacity of about twenty sheets.

In the modification shown diagrammatically in Figure 6, the carriage 10 carries a depending structure having a drive belt 45 passing around a gear wheel 46 and around a roller 47. The roller 47 has spikes or pins projecting from its cylindrical outer periphery. The lead screw 16 drives the gear wheel 46 and the roller 47, the latter engaging the uppermost sheet 30 of paper in the stack. The peripheral speed of the roller 47 equals the translational speed of the carriage 10, so that the roller 47 rolls (without skidding) across the surface of the uppermost sheet 30 of the paper, holding the paper in position as printing takes place. To prevent the printed area of the paper being perforated, the spikes on the roller 47 may be confined to one or both ends of the roller, so that the spikes engage one or both edge margins of the paper.

Claims

1. A thermal transfer printer comprising support means for supporting a stack of sheets of paper, a thermal transfer print head and receiving means for receiving a thermal transfer dye sheet so that the dye sheet extends between the head and an exposed sheet of paper in the stack, the print head being capable of selectively transferring dye from the dye sheet to the exposed sheet of paper in the stack, and the print head being capable of a traversing movement with respect to the support means for completion of printing of the exposed sheet of paper of the stack.

2. A thermal transfer printer according to claim 1, wherein the print head is mounted on a carriage guided for reciprocating movement in an alternating sequence of operative printing strokes and return strokes.

3. A thermal transfer printer according to claim 2, wherein the carriage is reciprocable above the support means so that the exposed sheet is the uppermost sheet in the stack.

4. A thermal transfer printer according to claim 3, wherein the head is mounted on the carriage so as to be movable between a lowered position, which the head occupies on each operative stroke, and a raised position which the head occupies on each return stroke.

5. A thermal transfer printer according to any of the preceding claims, wherein the receiving means is also mounted on the carriage.

6. A thermal transfer printer according to any of the preceding claims, wherein the receiving means is adapted to receive a cartridge containing a dye sheet ribbon extending between supply and take-up spools arranged such that the peel angle and peel force between the ribbon and the uppermost sheet are sufficient to ensure reliable separation.

7. A thermal transfer printer according to any of the preceding claims, wherein the support means are in the form of a tray with a movable base panel biased to urge the stack of paper so that the sheet which is for the time being uppermost occupies a predetermined position, so that the plane in which printing takes place remains constant in the printer as the stack of sheets is depleted.

8. A thermal transfer printer according to claim 7, wherein the movable panel is biased by springs biasing angled faces which engage rods guided for limited movement in slots and engaging the underside of the base panel.

9. A thermal transfer printer according to any of the preceding claims, wherein a roller movable with the print head engages the exposed sheet of paper to retain the latter during printing.

10. A thermal transfer printer having a housing supporting a paper tray for accommodating a stack of sheets of paper to be printed so that the length and width of the paper define two mutually orthogonal axes, a print head positioned above the paper tray and movable between a lowered operative position, in which the head presses a thermal transfer ribbon against the uppermost sheet of paper in the tray, and a raised inoperative position in which the print head is clear of the paper in the tray, the print head having an elongated line of print head elements which extend parallel to one of the two mutually orthogonal axes and the print head being movable parallel to the other of the two mutually orthogonal axes to execute print strokes and return strokes in alternate sequence, in each print stroke the print head being in the lowered operative position and completing printing of the uppermost sheet and in each return stroke the print head being in the raised inoperative position.

11. A thermal transfer printer according to claim 10, wherein the rest position of the carriage, which the carriage occupies between printing individual sheets, is at an intermediate position along the return stroke.

12. A thermal transfer printer according to claim 10 or 11, wherein the printer housing is formed to enable the thermal transfer printer to be wholly or partially slid out of a slot in a personal computer, for replacement of a ribbon cartridge