Background to the Invention The applicant has developed various printheads which provide high speed, photographic quality printing. The printheads comprise ink jet nozzles arranged in an array. The ink jet nozzles are formed using microelectromechanical systems (MEMS) technology. Using this MEMS technology results in very high speed printing capabilities where pages can be printed at a rate of up to two pages per second (for double sided printing).

To facilitate such high speed printing, it is important, firstly, that the paper feed to the printing station of the printer is accurate and capable of the required feed rate with as little likelihood of paper jams, or the like occurring. Secondly, bearing in mind that full bleed photographic quality printing may be effected on the print media, it is important to ensure that ink on the print media is dried before printed print media is deposited* in an output zone of the printer.

Summary of the Invention According to the invention, there is provided a print media transportation arrangement for a printer, the arrangement including:- a fluid source for entraining a sheet of printed print media in fluid and for transporting the sheet to a receiving zone; a guide path-defining means for maintaining the sheet out of contact with surrounding surfaces.

The fluid source may comprise a fan assembly for feeding air over at least a lower surface of the sheet.

The fan assembly may include a directing means for directing air emitted from the fan assembly in a downstream direction from a printing station for transporting the sheet in said downstream direction. More particularly, the directing means may comprise suitable vents having fins or slats pointing in the downstream direction.

Preferably, the fan assembly comprises two fan boxes, one for feeding air over the lower surface of the sheet and the other for feeding air over an upper surface of the sheet.

The fan assembly may be arranged at an output end of the printing station of the printer, the fan boxes being arranged in an angled relationship relative to each other diverging towards said receiving zone.

The guide path-defining means may comprise a platform arranged at a downstream end of the printing station so that a cushion of air is created between the lower surface of the sheet and the platform. The guide path-defining means may further comprise a cover member arranged in spaced relationship relative to the platform so that a further cushion of air is created between the upper surface of the sheet and the cover.

Brief Description of the Drawings The invention is now described by way of example with reference to the accompanying drawings in which:- Figure 1 shows a three dimensional view of a printer, in accordance with the invention ; Figure 2 shows a three dimensional view, from below, of the printer; Figure 3 shows a three dimensional view of a pre-printing stage of the printer; Figure 4 shows a three dimensional, exploded view of a print media pick-up assembly of a print media feed arrangement of the printer; Figure 5 shows a three dimensional view of the print media feed arrangement; Figure 6 shows a three dimensional view of the print media feed arrangement; Figure 7 shows a further, three dimensional view of the print media feed arrangement; Figure 8 shows a schematic, side view of a home stage of operation of the print media feed arrangement; Figure 9 shows a schematic, side view of a second stage of operation of the print media feed arrangement; Figure 10 shows a schematic, side view of a third stage of operation of the print media feed arrangement ; Figure 11 shows a schematic, side view of a fourth stage of operation of the print media feed arrangement;

Figure 12 shows a schematic, side view of a fifth stage of operation of the print media feed arrangement; Figure 13 shows a three dimensional view of a post-printing stage of the printer; Figure 14 shows a three dimensional view, from an input side, of a printing station of the printer; Figure 15 shows a three dimensional view, from an output side, of the printing station; and Figure 16 shows a schematic, sectional side view of the printing station.

Detailed Description of the Invention A printer, in accordance with the invention, is illustrated generally by the reference numeral 10. The printer 10 is a high speed printer which prints both sides of print media at <BR> <BR> the rate of approximately one sheet per second or two pages per second (i. e. , both sides of the sheet). The print media is, in this case, in the form of a stack of sheets. For ease of explanation, the invention will be described with reference to the print media being a stack of A4 sheets of paper.

Further, the printer 10 uses a pair of pagewidth printheads. Each printhead is in the form of a microelectromechanical systems (MEMS) chip having an array of inkjet nozzles to achieve the high speed, photographic quality printing desired.

The printer 10 has a frame or skeleton 12 supporting components of the printer 10.

The frame 12 is, in use, covered by suitable cladding (not shown) to provide an attractive, ergonomic unit.

The frame 12 has a base member 14, a rear wall 28 and a centrally arranged upright 16 spaced from the rear wall 28. The rear wall 28 and upright 16 support a printing station 18, a paper feed arrangement 20 and a printed paper ejection arrangement 22. The paper feed arrangement 20 is arranged upstream of the printing station 18 and forms part of an input side or pre-printing stage of the printer 10. The printed paper ejection arrangement 22 forms part of an output side or post-printing stage 26 of the printer 10.

The pre-printing stage 24 is shown in greater detail in Figure 3 of the drawings. A paper stack 30 is supported against a metal bulkhead 32 in a cabinet 34 (Figure 1). The cabinet is closed off by a door 36. The paper stack 30 is supported on a platen (not shown) slideably arranged within the cabinet to be vertically displaceable. A corresponding platen

38 of the post-printing stage 26 is shown in Figure 1 of the drawings. The platen of the pre- printing stage 24 and the platen 38 of the post-printing stage 26 are each driven by a drive arrangement 40 (Figure 2). Each drive arrangement 40 comprises a stepper motor 42, which raises or lowers its associated platen, as the case may be, accurately, by the thickness of a sheet of paper. The stepper motors 42 rotatably drive lead screws 44 of each platen via a belt 46 and pulleys 48.

The pre-printing stage 24 includes a tapping mechanism 50, which is solenoid driven, for tapping the paper stack 30 to ensure that the sheets of the stack 30 are maintained in accurate abutment with the metal bulkhead 32 so that, when a sheet is fed to the printing station 18 by the paper feed arrangement 20, as will be described in greater detail below, the sheet lifted from the stack 30 is accurately lifted to be in register with the printheads of the printing station 18. In other words, the tapping mechanism 50 inhibits skewing of a sheet picked from the stack 30. It is to be noted that the post-printing stage 26 also includes a tapping mechanism 52 (Figure 2) to ensure that printed sheets are arranged in accurate register in the post-printing stage 26 so that, for example, for binding purposes, the printed sheets are aligned. The tapping mechanism 52 is also solenoid operated.

Referring now to Figures 3 to 12 of the drawings, the paper feed arrangement 20 and its operation will be described in greater detail. The paper feed arrangement 20 includes a pick-up bar assembly 54. The pick-up bar assembly 54 includes a pivot rod or axle 56 (Figure 4) on which a connecting means in the form of a pair of opposed swing arms 58 are mounted. The assembly 54 further includes a suction bar 60 defining a plurality of suction channels or galleries 62 therein. The galleries 62 are closed off by a foraminous covering in the form of a perforated metal foil 64.

The galleries 62 are in fluid communication with a suction conduit in the form of a suction hose 66 which, in turn, communicates with a suction drive arrangement or suction pump 68 (Figure 1).

The pick-up bar assembly 54 is pivotally driven by a stepper motor 70.

An arm 72 having a bifurcated end 72.1 projects from one side of the suction bar 60.

The arm 72 is slidably received in a sleeve in the form of a pivot block 74. The arm 72 and, more particularly, its bifurcated end 72.1 cooperate with an optical sensor 76 to determine

when the pick-up bar assembly 54 is in its home position shown in Figure 8 of the drawings.

The paper feed arrangement 20 further includes a separating means 78. The separating means 78 facilitates separation of a single sheet of paper 80 from the stack 30 and inhibits the feeding of more than one sheet 80, at a time, by the paper feed arrangement 20 to the printing station 18.

More particularly, the separating means 78 includes an air bar 82 arranged adjacent the pick-up bar assembly 54. The air bar 82, which is fed by an air hose 84 (Figure 6), has a plurality of channels 86 defined therein. Each channel 86 communicates via an exhaust passage 88 with an outlet nozzle 90. Air is blown through the nozzles 90 against the leading edge of the picked sheet of paper 80 to facilitate separation of that sheet 80 from the paper stack 30 and/or any lower sheets that may have been lifted together with the picked sheet of paper 80 off the stack.

The separating means 78 further includes a snagging arrangement 92 which snags the leading edge of the sheet of paper 80 further to assist in separating the picked sheet of paper 80 from any lower, simultaneously lifted sheets of the paper stack 30. The snagging arrangement 92 comprises a plurality of fingers 94 arranged at spaced intervals along a length of the leading edge of the sheet of paper 80. The snagging fingers 94 project through openings in the bulkhead 32 (as shown for example in Figure 7 of the drawings).

As the sheet of paper 80 is raised by the pick-up bar assembly 54, the leading edge of the sheet of paper 80 snags against the fingers 94 but, due to the suction exerted on the sheet 80 by the suction bar 60, the sheet 80 is held against the suction bar 60. Any lifted sheets of paper below the picked sheet of paper 80 snag against the fingers 94 and fall back on to the paper stack 30.

In use, and referring more particularly to Figures 8 to 12 of the drawings, the pick- up bar assembly 54 is initially in its home position resting on the paper stack 30, as shown in Figure 8 of the drawings. When it is desired to feed a sheet of paper to the printing station 18, the suction pump 68 is operated to cause suction in the hose 66 and, accordingly, suction in the suction bar 60. As a result, the uppermost sheet of paper of the paper stack adheres to the suction bar 60.

The stepper motor 70 of the assembly 54 is then operated to cause the swing arms 58 to rise as shown in Figure 9 of the drawings. At this stage, the picked sheet of paper 80 has air blown underneath it by the air bar 82. Also, the leading edge of the sheet of paper 80 snags against the fingers 94 and is carried past the fingers 94. The leading edge of any sheet below the picked sheet of paper 80, if not already having been separated via the air from the air bar 82, snags against the fingers 94 and drops back on to the paper stack 30.

The swing arms 58 continue rising under the action of the stepper motor 70 to lift the sheet 80 clear of the paper stack 30 and direct the leading edge of the sheet 80 to primary drive rollers 96 of the printing station 18.

The swing arms 58 continue to rise and the sliding arm 72 moves upwardly relative to the pivot block 74. As shown in Figure 11 of the drawings, the suction bar 60 moves to a position beyond a plane 98 (Figure 11) bisecting a plane in which rotational axes of the rollers 96 lie. Also, due to rotation of the upper roller 96 in direction of arrow 100, the leading edge of the sheet of paper 80 is engaged by the periphery of the upper roller 96 and is driven between the rollers 96. This action disengages the sheet of paper 80 from the suction bar 60.

Finally, as shown in Figure 12 of the drawings, once the trailing edge of the sheet of paper 80 has cleared the pick-up bar assembly 54, the pick-up bar assembly 54 returns to its home position to pick the following sheet from the paper stack 30 while the sheet of paper 80 is fed through the printing station 18.

The printing station 18 includes, at its input end, the primary drive rollers 96. The primary drive rollers 96 feed the sheet of paper 80 through a paper deflector 102 which deflects the path of the sheet of paper 80 to a substantially horizontal orientation in this embodiment.

The sheet of paper 80 is fed from the paper deflector 102 between secondary rollers 104 arranged upstream of a printhead assembly 106.

The printhead assembly 106 includes a pair of printhead chassis 108. Each chassis 108 supports a pagewidth printhead 110 (shown schematically in Figure 12 of the drawings).

Referring to Figures 13 to 16 of the drawings, the post-printing stage 26 is described in greater detail.

The printed paper ejection arrangement 22 is arranged at an output or downstream end of the printing station 18. The paper ejection arrangement 22 includes a pair of fan boxes 112. The fan boxes 112 are arranged on opposed sides of the sheet of now printed paper 80.

As described above, the printer 10 is a high-speed printer which prints on both sides of the sheet of paper 80, if desired. To facilitate drying of the sheet of paper, air is blown over the surfaces of the printed sheet of paper 80 from fans 114 of the fan boxes 112. Each fan box 112 has a fan 114 arranged at each end thereof.

A platform 116 is arranged at the output end of the printing station 18. Air driven over the sheet of printed paper 80 serves two purposes. Firstly, the air, which may be heated if desired, dries printed matter on the surfaces of the sheet of paper 80. Also, the air driven over the printed sheet of paper 80 serves a transport function driving the printed sheet of paper 80 on to an output stack of paper 118.

More particularly, upon completion of printing of images or data or a combination of both on the sheet of paper 80, the sheet of paper 80 is fed between the fan boxes 112.

Air is driven over the surfaces of the sheet of paper 80 via slatted vents 120 angled towards the post-printing stage 26. As a result, the sheet of paper 80 is entrained in a cushion of air which transports the paper towards a stop plate 122 at a downstream end of the post- printing stage 26. In particular, a cushion of air is formed between the platform 116 and the lower surface of the sheet of paper 80 so that the lower surface of the printed sheet of paper 80 is not in contact with the platform 116. In so doing, drying of the lower surface is facilitated. The fan boxes 112 drive the printed sheet of paper 80 with sufficient velocity and force that the leading edge of the sheet of paper 80 strikes the stop plate 122 and is driven up into contact with a stop bar 124 mounted on the stop plate 122. In this position, a trailing edge of the sheet of paper 80 clears a free edge 116.1 of the platform 116. The spacing between the edge 116.1 of the platform 116 and the stop bar 124 is greater than a width of the sheet of paper 80. Accordingly, once the sheet of paper 80 strikes the stop bar 124 it falls through the gap between the edge 116.1 of the platform 116 and the stop bar 124 to be received on top of the output stack of paper 118.

As shown more clearly in Figure 1 of the drawings, cover members 126 and 128 are arranged above the platform 116 which also serves to trap air between the top of the sheet of paper 80 and the cover 126 which assists in the delivery of the printed sheet of paper 80 to the output stack of paper 118 and the drying of an upper surface of the sheet of paper 80.

Accordingly, it is an advantage of the invention that a printer 10 is provided which facilitates high-speed printing of photographic quality images. Also, it is an advantage of the invention that a robust paper feed arrangement 20 is provided. In particular, the configuration of the suction bar 60 of the pick-up bar assembly 54 ensures that creasing or localised folding of the sheet of paper 80 at the suction point is inhibited. Still further, the provision of the separating means 78 inhibits the feeding of more than one sheet of paper at a time to the printing engine 18. Still further, it is an advantage of the invention that a printed paper ejection arrangement 22 is provided which does not come into contact with surfaces of the printed sheet of paper 80 and which facilitates rapid drying of ink on the surfaces of the printed sheet of paper 80. This is also facilitated by the transportation path of the printed sheet of paper 80 into abutment with the stop bar 124 prior to being fed on to the output stack of paper 118.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.